US3057088A - Portable trenching device - Google Patents

Description

Oct. 9, 1962 Filed Nov. 2, 1960 W. E. GEORGE ETAL PORTABLE TRENCHING DEVICE 6 Sheets-Sheet l INVENTORS WARREN E .GEORGE FRED C. KIECHEL GLENN W. MCININCH ATTYs Oct. 9, 1962 w. E. GEORGE ETAL 3,057,088

PORTABLE TRENCHING DEVICE 6 Sheets-Sheet 2 Filed Nov. 2, 1960 INVENTORS WARREN E.GEORGE FRED C. KIECHEL GLEN W. McINmcH M //v-/ ATws,

Oct. 9, 1962 w. E. GEORGE ETAL 3,057,088

PORTABLE TRENCHING DEVICE Filed Nov. 2, 1960 6 Sheets-Sheet 3 OUT PUT RPM o VALVE TRAVEL (CONTROL COLLAR nu) INVIENTORS WARREN E. GEOQGE FRED C. KEECHEL Grams W. W: lNmcH gf 2 W 2/4 ATTYS.

Oct. 9, 1962 w. E. GEORGE ETAL 3,05

PORTABLE TRENCHING DEVICE Filed Nov. 2, 1960 6 Sheets-Sheet 5 a 4 nvmvroxs Jaw .. WARREN 56:50am;

I FRED C. KIECHEL F" Z3 GLENN WMcImNcH & b zJ/%, Wax mm rm's w. E. GEORGE ETAL 3,057,088

PORTABLE TRENCHING DEVICE Oct. 9, 1962 6 Sheets-Sheet 6 Filed Nov. 2, 1960 INVENTORS WARREN E-GEORGE FRED C. KIEcHEL GLENN W. McImNcH W 26%, M, w MA TTYS 3,057,088 PORTABLE TRENCHING DEVICE Warren E. George and Fred C. Kiechel, Auburn, and

Glenn W. Mclninch, Omaha, Nehr., assignors to Anburn Machine Works, Inc, Omaha, Nebr., a corporation of Nebraska Filed Nov. 2, 1960, Ser. No. 66,737 14 Claims. (Cl. 37--86) The present invention relates to trenching devices and more particularly to a self-propelled trencher capable of being maneuvered by hand into trenching position.

In the past, most commercial trenching operations have employed trenching attachments secured to a tractor or vehicle and manually guided trenchers have not been favored except for the digging of shallow trenches used to accommodate electrical conduits. Manually guided trenching devices capable of digging a trench of 3 to 6 inches in width and up to, say, 4 feet in depth have been diflicult to maneuver requiring application of brute force and difficult to transport to the digging location.

Accordingly, it is an object of the present invention to provide a manually operated trencher which is easily maneuvered into digging position, convenient to operate, and readily transported from job to job. It is a related object to provide a trencher which can readily be turned or skewed by application of light manual efiort. In short, it is an object to provide a trencher in which light manual control forces are all that is required to jockey the machine into precise digging position. It is an object to provide a trenching machine which is not only easily maneuvered under manual control but which is exceedingly compact and thus capable of use in narrow quarters not accessible by a conventional tractor or jeep-mounted trencher. It is a further object of the invention to provide a trencher which, although compact and easily manuvered is nevertheless heavy duty in that it is capable of digging trenches of adequate width and depth for the installation of drain tiles, sewer lines and the like and for domestic utilities including gas, water and electric lines, particularly where the latter are included in a common trench,

It is another object to provide a trencher having a high degree of traction and in which the weight, augmented by the suck of the digger blades is distributed substantailly equally over two spaced pairs of traction wheels. It is still another object to provide a trencher having a special pair of wheels capable of being lowered to ground engagement to assume the weight of the trencher during transport or While jockeying into position but capable of being raised clear of the ground during the actual trenching operation. It is another object of the invention to provide a trencher having a novel arrangement of tractive and auxiliary supporting wheels in which the auxiliary Wheels are located substantially at the center of gravity so that when the latte-r are in their lowered ground engaging position the trencher is balanced requiring only light efiort to move the machine with the traction wheels clear of the ground. It is another object to provide a trencher having separate sets of wheels for traction and maneuvering into position, making a total of six wheels but in which the wheels are compactly interfitted, with one set of the tractive wheels in an inwardatent 1y offset position thereby to insure the advantages of easy maneuverability and the compact construction and appearance assoicated with use of short wheelbase. In this connection it is an object to provide a trencher construction in which the effective wheelbase for maneuvering purposes is little more than one-half of that of machines of comparable size but of conventional design.

It is still another object of the invention to provide a trenching machine having a separate driving arrangement for maneuvering and for actual trenching operations which can be shifted from one mode of operation to the other simply by throwing a control lever and without the necessity for inserting or removing drive pins or similar mechanical coupling devices. In one of its aspects it is an object of the invention to provide a trenching machine in which power may be utilized in the maneuvering procedure but in which the supporting wheels are independently pivoted :and free of any connection to the power source.

It is a more specific object of the invention to provide a trencher which includes a novel transport wheel arrangernent which enables the trencher to be maneuvered while balanced solely on the transport wheels but which, nevertheless, permits power driving either forwardly or backwardly simply by rocking the trencher in one direction or the other to bring a selected pair of traction wheels into driving contact with the ground.

It is an object to provide a novel slow speed driving arrangement for the traction wheels which enables the unit, in spite of limited size, limited power of the engine, and limited weight to accomplish almost all of the work conventionally done by a trencher of the vehicle mounted type. It is a related object to provide a trencher having a novel variable speed hydraulic driving arrangement capable of applying a predetermined, but adjustable torque to the driving Wheels and so constructed that upon striking a large root, heavy clay or the like, the forward motion of the trencher is temporarily slowed until the obstruction has been chewed away, following which speed is automatically resumed. It is a more specific object to provide a trencher having maximum traction at the driving wheels with the wheels locked gear-like to the ground but in which intentional slippage takes place in the driving connection when hard-going is encountered to limit the torque applied to the driving wheels to a value below that which will cause wheel slippage. It is another object related to the foregoing to provide drive connection which is capable of limiting the driving torque to a predetermined, settable amount but which is nonretrograde so that the driving wheels do not give in the opposite direction thereby preventing cyclical bucking or bounceback when diflicult digging is encountered.

It is a further detailed object to provide hydraulically powered means for bringing transport wheels into position to support the trencher for transport purposes which is fail-safe and which provides for automatic locking in transport position. This prevents the trencher from being lowered into contact with the ground inadvertently while being towed behind a truck or automobile at highway speed.

It is another object of the present invention to provide highway transport Wheels as an integral part of the trencher thereby making it unnecessary to load the trencher onto a trailer for transport from job to job. This not only saves the inconvenience of loading or unloading but it is economical since it saves the expense of a trailer.

It is another object to provide a boom assembly which includes a boom housing and a boom telescoped therein and adjustably extensible to accommodate chains of different length and to take up for wear and elongation of the chain. In this connection it is an object to provide a boom housing which carries all of the auxiliary parts such as the auger, idler and dirt shield so that a boom of different length may be substituted and the chain changed to one of different length quickly and easily and without removal or adjustment of the auxiliary parts.

It is one of the detailed objects of the invention to provide in a trenching machine, having a pair of central wheels for transport, a tow bar which permits adjustment for the height of the towing connection and which is retractable into the machine, out of the way, during the trenching operation.

In one of its aspects it is an object of the present invention to provide a trencher having a novel box-type body of great rigidity and strength and which serves as a fixture for the support of connected and moving parts in permanent alinement with one another and which enables the whole assembly to be made and fitted together with a precision which is beyond that normally achieved in the field of trenching equipment. It is a related object to provide a trencher having a box-type body pro viding a lower profile and smaller width than trenchers of conventional design. In this connection it is an object to produce a trencher which has an attractive streamlined appearance and with the various operating parts being out of sight yet with the necessary control levers conveniently accessible to the operator. It is an object to provide a trencher which is inherently strong and durable and which may be operated for long periods of time under the most difficult operating conditions without strain or danger of mechanical breakage.

Finally, it is an object to provide a trenching machine which provides in a novel combination the trench digging capability of a vehicle mounted trencher and ability to operate in tight quarters possessed by a manually guided trencher but which is simple in construction, inexpensive to manufacture and which requires little or no maintenance over extended periods of use.

Other objects and advantages of the invention will become apparent upon reading the attached detailed description and upon reference to the drawings in which:

FIGURE 1 is a perspective view of a trencher construction in accordance with the present invention with the digger chain ready to be lowered into the ground.

FIG. 2 is a top View of the trencher shown in FIG. 1 with the top of the housing broken away in order to re veal the enclosed mechanism.

FIG. 3 is a side view of the chain drive connection between the engine and the digger chain.

FIG. 4 is a front view, in perspective, of the trencher with the boom housing and bearing caps removed.

FIG. 5 is a perspective showing the boom housing and associated auger flights.

FIG. 6 is a vertical section taken through the boom housing showing the means for adjusting the boom length.

FIG. 7 is a diagrammatic perspective showing the means for driving a tractive wheel.

FIG. 8 is a diagrammatic perspective showing the means for controlling the hydraulic coupling.

FIG. 8a shows the characteristic curves of the hydraulic coupling.

FIG. 9 is a fragmentary section taken through the trio tion positioning device of FIG. 8.

FIG. 10 is a top view of the forward-reverse gear box.

FIG. 11 shows the linkage associated with the transport wheels with the latter in upraised position.

FIG. 12 is a view similar to FIG. 11 but showing the wheels in lowered transport position and with the locking element engaged.

FIG. 13 is a diagrammatic view of the hydraulic system for operating the boom housing and transport wheels.

'FIG. 14 is a side view showing the trencher in its balanced condition for skewing into place by an operator.

FIG. 15 is a perspective showing the transport of the present trencher behind an automobile.

FIG. 16 is a fragmentary section showing the hitch adjusting mechanism.

FIG. 17 is a diagram of an alternate form of transmiss1on.

While the invention has been described in connection with a preferred embodiment, it will be understood that we do not intend to be limited to the particular embodiment shown but intend to cover the various modifications and equivalent constructions included within the spirit and scope of the appended claims.

Turning to the drawings and particularly to FIGURE 1, there is shown a trencher 20 constructed in accordance with the present invention. It includes a body 21 of hollow box-like construction supported fore and af on traction wheels 23, 24 and having a pair of transport wheels 25 to which later reference will be made. Extending from the right-hand or trailing end of the body is a boom assembly 30 about which is trained a digging chain 31 carrying a set of digger blades 32. Mounted on the boom assembly 30 is an auger 35 which moves the excavated dirt away from the trench laterally in both directions. For the purpose of driving the traction wheels 23 and the chain 31, an engine or prime mover 40 is provided at the left-hand end of the trencher. Mechanical coupling means employed to drive the chain at high speed and the traction wheels at relatively low speed will be described in connection with the other figures. It will suffice to say that the torque transmitted to the traction wheels, and hence the speed under given load conditions, is controlled by a manual control lever 41, and the direction of movement of the trencher, whether forward or reverse and with an intermediate neutral, is under the control of a lever 42. In order to raise and lower the boom assembly 30, an hydraulic lift is provided under the control of an hydraulic control lever 43. Hydraulic means are also provided for raising and lowering the transport wheels 25 under the control of a lever 44.

For the purpose of maneuvering the trencher into position and also for guiding it in the desired direction of the trench, a tubular framework 50 is provided at the front of the trencher including handles 51, 52 at a convenient height for the operator. And for the purpose of towing the trencher from job to job behind a truck or automobile, a hitch, generally indicated at 55, is provided at the forward end.

With the over-all appearance of the machine in mind, it will be convenient, in the discussion which follows, to consider in some detail the various sub-assemblies which, either solely or jointly with other sub-assemblies, contribute to the final result and to the features and advantages of the present machine. Thus attention may first be given to the boom assembly 30 disclosed in FIGURES 2-6, inclusive, but particularly well shown in FIG. 5. Here it will be noted that the assembly includes a boom housing 60 which is of hollow, elongated construction and having a pair of alined supporting brackets 61, 62 defining a space 63 between them. Projecting laterally from the brackets 61, 62 are stub shafts or trunnions 65, 66 which are mounted in bearings 67, 68 (see FIG. 4) fixed in the body 21 of the trencher.

Telescoped into the boom housing 60 is a boom 76 having an idler 71 at its outer end. The boom 70 is rigidly connected to the boom housing yet adjustable with respect to it. As shown in FIG. 6, a pin 72 projects through the boom and boom housing, registering with an opening 73 in the boom and slots 74 in the housing. Since the boom is of hollow construction, the opening 73 is preferably reinforced with .a length of pipe or tubing as illustrated. In order to adjust the degree of extension of the boom and thereby take up any wear or elongation which may occur in the chain, the pin 72 is mounted upon threaded supports 75 which are anchored in eyes 76 welded or otherwise secured to the boom housing. Turning the nuts '77, as will be apparent, moves the pin in the slots 74 providing the necessary takeup. In order to accommodate different lengths of chain for digging trenches of difierent depth, additional openings 78 are provided in the boom, reinforced in the same manner as the opening 73, for selectively accommodating the pin 72.

In carrying out the present invention, the auger assembly which engages the lower run of the chain and the idler which engages the upper run of the chain are both secured to the boom housing so that neither of these elements need be adjusted or disturbed when changing from one length of boom to another. Turning next to the auger assembly 35, it includes a shaft having left and right-hand flights 91, 92, respectively, mounted on tubular supports 93, 94. The shaft 90 is supported at the center on a bracket formed of a U-shaped piece of metal having edges which are secured to the side walls of the boom housing by bolts 96. Fore and aft adjustment is provided by a series of holes 97. It is one of the features of the present arrangement that the flights 91 are not fixed with respect to the shaft 90 but are adjustable inwardly and outwardly in order to accommodate digger blades having different width or span. To provide this adjustability, the tubular supports 93, 94 are provided with a series of holes 98 which selectively register with holes in the shaft 90 and with the parts being secured together by an inserted roll pin or the like.

For the purpose of rotating the flights the auger shaft 96 has at its center a sprocket 100 which is alined with the chain and in mesh with it. The upper run of the chain is supported by an idler 1111 mounted on a bracket 102 which is welded or otherwise fixed to the boom housing 60.

To drive the chain, a chain drive shaft 105 is provided having a drive sprocket 106 which is centered in the space 63 between the two alined brackets 61, 62 of the boom housing. To provide access, the two stub shafts or trunnions 65, 66 which support the boom housing are made hollow for reception of the shaft 105, and suitable bearings are interposed. For the purpose of coupling the engine 411 to the chain drive shaft 105, a roller chain 110 is used (see FIG. 2) which lies adjacent the inside wall of the trencher body. At the front end, the chain 110 is trained about a sprocket 111 which projects from a gear box 112 which is integral with the engine 40 and which has a control lever 113 to engage and disengage the driving chain. At the rear end of the chain 110 a sprocket 115 is provided which is secured to the shaft 195 and which is provided with shear pins 116 made of hard wood or the like and designed to break when the digging chainencounters some non-yielding obstruction in the ground. The chain 110 is kept taut by idler pulleys 117.

For the purpose of reinforcing the brackets 61, 62 on the boom housing with respect to one another and also for the purpose of deflecting any dirt which may be thrown from the chain or digger blades when the chain abruptly changes direction, an arcuate deflector plate 113 is used mounted on short brackets 119.

To hold the boom down in digging position and to raise the boom upright for transport under power when the work is completed, an hydraulic actuator 12% is provided (FIG. 5) having supply lines 121, 122. Connected to the actuator is a rack 123 which operates a gear 124 which is secured to the hollow stub shaft 66 which forms a part of the boom housing. Interposed between the rack 123 and the gear 124 is an auxiliary idler pinion 125.

As will be noted, the pinion 125 is on a center which is substantially forward of the gear 124 in order to reduce the degree of projection of the rack when the actuator is fully extended. The rack and pinion are maintained in engagement by a back-up roller 126. The source of hydraulic pressure for powering the actuator 12% will be described at a later point.

It will be apparent from what has been said thus far that the actuator 120 serves to rock the boom assembly 30 down into contact with the ground. With the digger blades driven by the chain 110 on sprocket 106, the boom gradually cuts its way to an operating position in which it is inclined rearwardly and downwardly from the end of the trencher .and with the trench being cut upon slow forward movement of the traction wheels 23, 24.

In accordance with one of the aspects of the present invention, a step-down, high torque drive connection is provided between the engine 40 and the traction wheels with means for limiting the transmitted torque to a predetermined but adjustable value so that forward movement of the trencher is reduced when the blades encounter hard-going, as for example, when the blades must cut through a thick tree root, with normal forward speed being resumed as soon as a path has been cut through the obstruction. Referring to FIGS. 2, 7 and 8, limitation of torque is accomplished by an adjunstable hydraulic coupling 131} having an input shaft 131 and an output sprocket 132. For coupling the input shaft to the engine, a V-belt 135 is used which is trained about pulleys 136, 137, the pulley 136 being directly connected to the crankshaft of the engine. An idler pulley 138 takes up any slack in the belt. From the output sprocket 132 of the hydraulic coupling, power is transmitted to a transmission 140 having an input shaft 141 and an output shaft 142. The connection is made by a roller chain 145 which is trained over sprockets 132, 147 respectively.

Mounted on the output shaft 142 of the transmission, are sprockets 151, 152. The sprocket 151 serves to drive the forward traction Wheels 23 by means of a sprocket chain 153 and driven sprocket 154, the latter being pinned to an axle 155 which rigidly interconnects the two front traction wheels 23. Similarly, the output sprocket 152 drives a chain 157 which is trained about a sprocket 158 on an axle 159 interconnecting the rear traction wheels 24. A speed reduction of approximately 30:1 is provided in the transmission 140' so that the wheels 23, 24 creep forwardly at a slow trenching speed and with the torque which they exert upon the ground being limited in accordance with the value for which the hydraulic coupling has been set.

Referring to the hydraulic coupling 130, the purpose of the device, briefly stated, is to limit the torque transmitted to the traction wheels to a preset value. It accomplishes this by producing an output speed which varies more or less inversely with the torque imposed by the load. Thus, assuming the unit is driven at a constant speed by a prime mover, a speed which may in a practical case be 1760 r.p.m., the output speed at near zero load may equal the input speed so that there is little or no slippage. However, as the torque load is increased, the output speed drops off or droops until a predetermined equilibrium speed is reached, the actual speed depending upon the setting of the control element.

To select a desired speed torque characteristic, the coupling includes a control collar 160 (FIG. 8) which is engaged by a lever 161 having one end pinned to the trencher frame at 162. The other end 163 is connected to a rod 164 which is connected to a bell crank 165 and which in turn is coupled to a second rod 166. The latter is operated by a crank 167 to which is secured the control lever 41 previously referred to. In order to insure that the control linkage remains in a preset position in spite of shock and vibration, a friction holding device is provided as shown in detail in FIG. 9. Here it will be noted that the crank 167 is formed on a disc having a conical projection 168 which engages a conical seat 169. To draw the surfaces 168, 169 into snug frictional engagement, a spring 170 is used which encircles a bolt 171 which is fixed in position in the member 167. Consequently, the control lever 41 and the associated linkage is securely held in position between adjustments, having a range of adjustment all the Way from neutral or zero output to the maximum torque position limited only by the power of the engine and the strength of the driven parts.

The present device is not limited to any particular construction of hydraulic coupling, and adjustable couplings providing a drooping speed-torque characteristic may be selected by one skilled in the art from couplings commercially available. As a guide in selection, FIG. 8a shows characteristics applicable to a practical unit, the curves being somewhat idealized for easy understanding. The curves are constant torque curves, for a range of torque from 4 foot lbs. to foot lbs, with speed being indicated as a function of the setting of the control element 16d. For a given setting, the speed-torque output characteristic is defined by a vertical line, for example, the line 1695:, which shows that in the face of a change in loading from 4 to 20 foot lbs. the speed varies from about 1700 rpm. to about 500 rpm. The net eifect is that the trencher assumes a forward speed in accordance with the load imposed on it, speeding up and slowing down automatically depending upon whether the going is easy or hard.

Further in accordance with the invention, the transmission 14fi includes an irreversible worm gear which precludes any retrograde movement of the traction wheels when the digger blades strike hard clay or the like. Thus, referring to FIG. 10, the input shaft 141 drives a worm 18th which is in mesh with a worm wheel 181 mounted upon a shaft 182. Since power cannot be transmitted reversely from the worm wheel to the worm, it will be apparent that retrograde movement of the traction wheels 23, 24 cannot occur thereby preventing any tendency toward cyclical rebound under certain trenching con-,

ditions.

Further in accordance with the invention, means are provided in the transmission 140 for permitting either forward or reverse rotation of the traction wheels at slow speed, thus permitting the transition wheels to be employed for maneuvering the trencher into position as well as for providing the necessary tractive effort during digging. In the present instance, the reversibility is provided by selectable forward and reverse bevel gears. Referring to FIG. 10, a first bevel gear 19%) is provided on the shaft 182 running in engagement with forward and reverse bevel gears 121, 192. These bevel gears have splines 193, 194, respectively. Centered between them is an output spline 195 which is pinned to the output shaft 142 of the transmission. Slidable endwise on the splines is a splined collar 196 having a fork 197 and an operating plunger 198. The latter is coupled to the forward-reverse control 42 by means of a linkage 200. Such linkage (FIG. 7) consists of an arm 201 which is pinned to the plunger 193, a shaft 202 and an arm 263 connected to a rod 204. At the upper end of the rod 284 is an arm 265 which is rigidly connected to the control lever 42. It will be apparent then, that by moving the control lever in one direction or the other from its central or neutral position, the sliding collar 196 in the transmission serves to couple the central spline 195 selectively with the splines 193, 194 (FIG. 11) to provide the desired forward and reverse rotation of the traction wheels.

In accordance with the present invention, a pair of transport wheels are provided between the pairs of traction wheels with means for shifting them from an upraised idle position to a downwardly thrust position in which the transport wheels extend beyond the plane defined by the traction wheels, and with the transport wheels approximately alined with the center of gravity when in the lowered position so that the transport wheels may be employed for supporting the trancher either solely or jointly with one of the pairs of traction wheels as the trencher is maneuvered into working position. In the present instance, the transport wheels indicated at 25 are alined with one another about a transversely extending axis 210. The wheels are mounted upon cranks 211, 212 secured to a transverse crankshaft 213 which is mounted for rocking movement in the body of the trencher.

For the purpose of swinging the wheels between their limit positions, a, double-acting hydraulic actuator 215 is provided (FIGS. 11 and 12) which has supply lines 216, 217 and which is pivoted to the body of the trencher at 218. Reciprocable within the actuator is a plunger 219 carrying a pin 22%. For coupling the actuator to the crankshaft 213, an operating crank 221 is provided near the center of the shaft, and having provision at its upper end for receiving the pin 220 on the plunger.

In accordance with one of the aspects of the present invention, a latch or detent is provided for the operating crank 221 for positively locking the transport wheels in their downwardly thrust position at the end of the stroke of the actuator and with provision for releasing the latch when the actuator is subsequently moved in the opposite direction. In the present instance the pin 220 serves as the latch member riding in a slot 222 and cooperating with an abutment 225 on the trancher body which is arranged in the path of movement of the pin. For guiding and receiving the pin the abutment member 225 includes a notch 226 having an adjacent ramp 227.

To understand the operation of the locking arrangement, consideration may be given to a cycle in which the transport wheels are lowered from the upraised position shown in FIG. 11 to the operating position shown in FIG. 12. Hydraulic fluid is supplied to the actuator 215 through the line 216 causing the plunger 219 to be drawn upwardly. Such movement is accompanied by clockwise rotation of the crank 221 accompanied by swinging of the transport wheels 25 in the downward direction. As the plunger 219 nears the end of its stroke, interference takes place between the pin 220 and the ramp 227 causing the pin to be cammed downwardly in the slot 222 formed in the crank. As the pin 220 rides along the ramp, a point of drop-off is reached following which the pin moves into the notch 226 so that the plunger is free to take up the lost motion between the crank 221 and the pin. This seats the pin 220 fully in the slot 226 thereby locking the crank 221 and the transport wheels in the position shown in FIG. 12. It will be noted that such locking does not depend upon the existence of any pressure in the actuator 215. Thus, ground reaction on the transport wheels tends to rotate the shaft 213 to which they are secured in a counterclockwise direction. However, because of the interference between the pin 220 and the wall of the notch 226, no rocking movement can take place. Consequently, the transport wheels are fixed in position and there is no risk that the traction wheels will be lowered into contact with the ground either during maneuvering or long-distance hauling.

When pressure is re-applied in the opposite direction, automatic unlocking of the pin 220 occurs incident to the taking up of the lost motion between the plunger and the crank. Thus, referring to FIG. 12, it will be apparent that downward thrusting movement of the plunger 219 acts first to move the pin 220 out of the notch 226. Continued thrust causes the freed pin 22% to ride along the ramp 227 accompanied by counterclockwise rotation of the crank 221 and upward swinging of the transport wheels 25 on their respective crank arms. This restores the transport wheels to the out-of-the-way position shown in FIG. 11, and the weight of the trencher is fully restored to the traction wheels 23, 24.

In order to understand the hydraulic system employed powering the actuator 215 which raises and lowers the transport wheels and the actuator 120 which raises and lowers the boom, reference is made to FIG. 13. Fluid pressure is derived from a pump 230 having an output or pressure line 231 and a return line 232 feeding a sump 233. To control the admission of pressure fluid alternatively to the lines 121, 122 supplying the boom housing actuator, a first valve 235 is provided connected to the boom control lever 43. Moving the control lever 43 to the left as shown in FIG. 13 causes fluid pressure to be applied to the line 121 to raise the boom while movement of the control lever 43 in the opposite direction applies pressure to the line 122 to lower the boom. Similarly, an hydraulic valve 236 is associated with the hydraulic control lever 44 so that movement of the lever in one direction causes pressure to be supplied to the line 217 expanding the actuator and swinging the wheels into the up position, whereas moving the control lever in the opposite direction applies pressure to the line 216 retracting the plunger 219 so that the transport wheels are thrust downwardly into the ground-engaging position. All of the control levers are, as noted in FIG. 1, within easy reach of the hands of the operator.

In accordance with one of the features of the present invention, one of the pairs of traction wheels is spaced more closely together than the other and is mounted in a recessed or nested position within the confines of the transport wheels. Thus, as shown in the drawings and particularly FIGS. 2 and 4, the rear traction wheels 24 are closely spaced inside of the trencher body and re cessed within the transport wheels 25. Prior to discussing the advantages which result from this arrangement, it will be helpful at this point to point out a still further feature of the present construction. Thus, in carrying out the invention, the body 21 is made of hollow box-like construction including a pair of spaced hollow protuberances which not only accommodate the boom assembly bet-ween them but which provide housing and support for the narrowly spaced traction wheels 24. In the present instance, the two protuberances are indicated at 241, 242, respectively, defining a space 243 between them which is sufficiently wide to accommodate the brackets 61, 62 at the inner end of the boom housing. Moreover, the inner opposed walls of the protuberances, indicated at 245, 246, serve to mount the boom housing bearings 67, 68, previously referred to. Finally, it is a feature of the present invention that the rounded tip portions of the protuberances indicated at 247, 248 are separable from the body along a line 249 and serve as a mounting for the mating parts of the two bearings 67, 68. In short, the members 247, 248 serve the function of bearing caps and, when removed, provide access to the interior of the body of the trencher as shown in FIG. 4.

The primary advantage of the nested traction wheel construction is that the over-all length of the trencher body is substantially reduced producing a design which has great inherent compactness. The resulting short wheel base makes the machine more easily maneuverable and more easily transported from place to place. The compactness is indeed striking when it is considered that the trencher has six full-sized wheels, with the appearance more closely resembling that of a four wheeled vehicle. Moreover, the traction wheels 24 are out of the path of movement of the transport wheels 25 as the latter are swung on their cranks between their raised and lowered positions thereby permitting a large range of vertical movement for the transport wheels free of any clearance limitations. Also important is the fact that each of the four traction wheels follows a separate track and therefore each can secure a fresh positive grip upon the ground which is desirable under slick, clayey conditions.

It is an over-all feature of the present construction that the trencher may be maneuvered, either manually or with power, by a single operator to desired operating position even in close quarters where a conventional jeep or tractor-mounted trencher cannot be used. Thus, referring to FIG. 14, since the transport wheels are alined with the center of gravity, it is an easy matter for the operator to balance the trencher above the transport wheels and the trencher may, if desired, be simply wheeled into position. When supported on the two transport wheels, which are independently rotatable, the entire trencher may, with extremely light manual force, be turned or skewed in order to achieve the desired alinement with the direction of cut. Where it is desired during the maneuvering operation, to drive the trencher in one direction or the other with power from the engine, it is sufiicient for the operator to rock the trencher downwardly about the transport wheels, thereby bringing one set of the traction wheels 23, 24 into engagement with the ground. With the torque control handle set in the lower portion of its range, the forward-reverse lever 42 may then be moved in one direction or the other to drive the trencher at a slow speed, either forwardly or backwardly. If desired, the traction wheels may be left running at a slow speed While the trencher is balanced on the transport wheels and the unit may be rocked so that one set of the transport wheels, preferably the forward set, comes into grazing contact with the ground. This gives the operator precise control of the amount of driving effect without requiring the operator to adjust the control levers. Thus, the operator has a delicate control of speed without having to move his hands from the handles 51, 52.

In short, it has been found that a trencher constructed as described above may be maneuvered into any desired working position quickly and with minimum effort by a single operator in spite of the fact that the machine may have a total weight on the order of 1100 pounds. Complete flexibility is provided by applying a combination of light rocking and skewing movements to the guiding handles, a knack quickly acquired by an operator. This is to be contrasted with conventional manually directed trenchers which are either so light as to be ineffective in digging a trench of useful size, or so heavy and unbalanced as to be awkward to maneuver, requiring the services of several men to wrestle the trencher into position. The trencher is also to be contrasted with units which require the wheels to be unpinned for maneuvering purposes.

The present trencher is particularly suited for drawing at high speed behind an automobile or truck from one job to another as shown in FIG. 15, with the hitch 55 at the front end of the trencher being securable in the usual fashion to the ball of a conventional bumper hitch. To transport the trencher from the job, the transport wheels are lowered into ground-engaging position where auto matic locking takes place as has been previously discussed in connection with FIG. 12. The engine may then be turned ofi since the transport wheels are locked even without pressure in the associated actuator 215. The front end of the hitch 55 is then secured to the ball and a canvas cover may be used, as indicated in FIG. 15, to protect the engine of the trencher from the dirt or moisture which may be thrown up from the road.

In accordance with one of the detailed aspects of the invention, means are provided for varying the height of the hitch connection 55 so that the height of the traction wheels on the trencher may have the same ground clearance independently of the height of the ball on the towing vehicle. To accomplish this, a novel hitch arrangement is used having a height-adjusting mechanism generally indicated at 250 (FIG. 16). The hitch is secured to an extensible tongue 251 which is slidable in an angularly adjustable socket 252. The tongue is maintained in a desired extended position with respect to the socket by a bolt 253. In carrying out the invention, the socket 252 is pivoted to the body of the trencher for rocking about a horizontal pin 254 and means are provided for holding the socket in predetermined angular position. In the present instance, this is accomplished by providing the 11" socket 252 with a pair of spaced downward extensions 255 (only one being shown) having a nut 256 between them. The nut is engaged by an adjusting screw 257 received in the apron 258 of the trencher body. Lock nuts 259, jammed together, serve as a thrust collar to keep the screw 257 seated in the apron 258. Thus, for maximum ball height, the adjusting screw 257 may be screwed as far as possible into the nut 256, causing the socket 252 to assume the upwardly angled position illustrated in FIG. 16. In order to use the bitch with a lower ball, the adjusting screw 257 is turned to rock the socket 252 counterclockwise into the position shown dotdash. Any play between the parts is taken up by a clamping mechanism 260. This mechanism includes a rockable clamping member 261 which is pivoted to the pin 254 and which has a cam surface 262. The lower end of the member 261 is engaged by a threaded thumb screw 263. It will be apparent that regardless of the angling of the socket member 252, screwing the thumb screw 263 inwardly causes the clamping member 261 to be cammed against the tongue 251 thereby taking up the looseness or play between the tongue and the socket or between the socket and the body of the trencher.

It will be apparent that by use of the novel hitch arrangement, the hitch 55 may be moved upwardly or downwardly as may be necessary to equalize the clearance of the traction wheels and the trencher may therefore be pulled by diflerent automobiles or trucks, as may be convenient. With maximum ground clearance assured, and with automotive type bearings in the wheels 25, the present trencher may be pulled at high speed along a highway so that the time lost between jobs may be reduced to a minimum. Moreover, a single trencher of the above type may be used by a single contractor to cover a wide area of operation, much wider than might be covered, for example, by a tractor-mounted trencher. Because the trencher is substantially balanced over the transport wheels, a light vertical hitch force is assured. The expense of a trailer or dolly is saved.

Not only is the trencher easily maneuvered or jockeyed into position, but it tends to follow a straight line with minimum effort on the part of the operator. Where the trencher strikes a patch of hard packed clay, a thick tree root or similar obstruction, the limitation of the torque to the traction wheels, and the drooping speed characteristic of the hydraulic coupling, causes the trencher to be slowed down automatically until the digger blades have had opportunity to cut their way through the obstruction, whereupon normal forward speed is resumed, all without care or attention on the part of the operator. All of the controls are readily accessible at the front end of the machine so safe, convenient control is assured. Moreover, because of the irreversible nature of the drive, retrograde action of the traction wheels is prevented and the rebound experienced particularly in light weight trenchers under certain digging conditions is minimized, with the trencher proceeding on a smooth steady course. The trencher in spite of its small size is capable of digging trenches of considerable width and of a depth which approaches that achieved by trenchers mounted on a tractor or jeep. Consequently, the trencher may be employed for all but the very heaviest work.

The trencher body being of box-like construction, is extremely rigid for its weight. The length of which the body is made may be accurately jig-welded and parts may be fitted into the body with an alinement accuracy which greatly exceeds the accuracy attainable in conventional trencher construction. Instead of having tolerances characteristic of farm implements, fits and alinements are established with high precision enabling the unit to with stand hard useage over a long period of time without adjustment and with only causal maintenance, primarily lubrication. In this connection, the transport wheels serve as a built-in jac which greatly facilitates inspection and servicing. Thus, when the transport wheels are 12 shifted to their lowermost position, the trencher may be rocked fully in one direction or the other to bring either pair of traction wheels into contact with the ground, thus exposing for view and easy access approximately one-half of the underside of the machine. The trencher will remain stable in either position.

While the invention has been described above in connection with a preferred embodiment, it will be understood that an alternate mode of operation may be secured by the making of a minor change in the transmission and which is accompanied by a number of novel advantages. Thus, it is contemplated that as part of the present invention, means may be provided for causing the two pairs of traction wheels to rotate simultaneously but in opposite directions when the trencher is balanced on the transport wheels and while it is being maneuvered into position, thereby permitting the trencher to be propelled slowly in one direction or the other simply by lowering the appropriate pair of traction wheels into grazing contact with the ground without requiring the shifting of any forward-reverse lever in order to achieve the two directions of motion. In the present instance, this is brought about by modifying the transmission 140 as set forth in FIG. 17, where corresponding reference numerals indicate elements corresponding to those in FIG. 10. Here it will be noted that the shaft 142 which is connected to the output sprockets 151 and 152 has been split into two parts, 271, 272. Output sprocket 152a, which is connected to the rear traction wheels, is coupled directly to the bevel gear 192a by shaft 271 as indicated by the pin 273. Output sprocket 151a, which is coupled to the front traction wheels is coupled to the central spline 195a by a pin 274. Thus, when the shiftable splined collar 196a is in the righthand position as viewed in FIG. 17, the output sprocket 15112 is connected directly to the output sprocket 152a for rotation of all four of the traction wheels in the same direction as required for normal trenching.

However, when the splined collar 195a is moved to its opposite or left-hand position, then the central spline 195a is directly coupled to the spline 1930 on the opposite bevel gear 1910:. Since the bevel gear 191a always rotates in the opposite direction from the bevel gear 192a, such shift causes the output sprocket 151a to rotate the forward traction wheels in the opposite direction. Thus, under such conditions the two pairs of traction wheels will rotate simultaneously but in opposite directions. Operation under such conditions may be clearly visualized with reference to FIG. 14. Thus, upward pressure applied to the manual guiding handles serves to rock the trencher in a clockwise direction about the transport wheels so that the traction wheels 24 are brought into grazing contact with the ground propelling the trencher in the same direction that the operator is facing. At any time the operator can ease off on such driving movement by rocking the trencher back into its balanced position. Conversely, the operator may apply downward pressure upon the guiding handles which will bring the traction wheels 23 into grazing contact with the ground, causing the trencher to be propelled toward the operator. Again, movement in such direction may be terminated simply by rocking the trencher back to its centered condition. Thus, by a combination of rocking movements in one direction or the other under relatively light manual pressure, the trencher may be jockeyed forwardly and backwardly. This combined with the skewing movement already referred to in which the trencher is skewed sideways in one direction or the other to change its direction of movement, enables the trencher to be positioned in precise operating position in a minimum of time.

While the latter mode of operation has the advantage of flexibility and enables maneuvering under power in both directions without requiring the control levers to be touched, nevertheless, this mode of operation does require slightly greater care and skill for full utilization, and for this reason, the earlier mode of operation will normally treatise be preferred. The position of the control lever 42 which makes the two directions of movement simultaneously available to the operator may be designated Fwd-Rev. (forward-reverse), while the opposite position used in actual trenching may be designated simply Fwd. While the transmission modified in accordance with FIG. 17 does not provide a central neutral setting in which both sets of traction wheels are turned completely off, this ofi position can nevertheless be achieved simply by moving the control lever 41 to its off or neutral position at one end of the control range.

In the following claims, the term shifting as applied to the transport wheels shall be understood to mean shifting relative to the traction wheels since it will be apparent to one skilled in the art that the invention is not limited to movement of the transport wheels but is broad enough to encompass corresponding relative movement of the traction wheels between upraised and ground-engaging positions.

We claim as our invention:

1. In a trencher the combination comprising a frame, digger means including movable digger blades, on said frame, a prime mover having a drive connection to said digger blades, a first pair of traction wheels at one end of the frame rigidly coupled together, a second pair of traction wheels at the other end of the frame rigidly coupled together, a pair of individually rotatable transport wheels between said pairs of traction wheels, said transport wheels having substantially the same span as the first pair of traction wheels, and said second pair of traction wheels having a substantially reduced span and being nested within the confines of transport wheels so that the second set of traction wheels is overlapped by the transport wheels, and means for raising and lowering the traction wheels with respect to the body between limit positions.

2. In a trencher the combination comprising a body, a digging boom having movable digging blades and mounted at one end of the body, a prime mover on said body having means for driving the blades, fore and aft pairs of traction wheels rotatably mounted on said body for normally supporting the same, a pair of transport wheels mounted on said body along a transverse axis generally alined with the center of gravity of the trencher and having means for vertically shifting the same into a lowered position beyond the plane of normal support and so that at least one pair of the traction wheels is upraised from the ground, a slow speed high torque driving connection interposed between the prime mover and the traction wheels, said driving connection having manually adjustable means for limiting the transmitted torque to a predetermined value, said torque limiting means having a drooping speed characteristic so that when the digger blades strike a root or similar obstruction the speed of the traction is automatically slowed while maintaining the normal speed of the digger blades until such obstruction is overcome.

3. In a trencher the combination comprising a body, a digging boom having movable digging blades and mounted at one end of the body, a prime mover on said body having means for driving the blades, fore and aft pairs of traction wheels rotatably mounted on said body for normally supporting the same, a pair of transport wheels mounted on said body along a transverse axis generally alined with the center of gravity of the trencher and having means for shifting the same into a lowered position beyond the plane of normal support and so that at least one pair of the traction wheels is upraised from the ground, a slow speed high torque driving connection interposed between the prime movement and the traction wheels, said driving connection having manually adjustable means for limiting the transmitted torque to a predetermined value, axial driving connection including non-retrograde worm gearing interposed between the torque limiting means and the traction wheels.

4. In a trencher the combination comprising a body of generally box shape terminating at one end in a pair of hollow box-like protrusions defining a vertical opening between them, a digging boom having one end arranged in said vertical opening and journaled in said protrusions to permit vertical swinging movement of the boom, said boom having a series of movable digger blades, a prime mover in said body coupled to the digger blades, a first pair of traction wheels mounted outboard of the body at the end thereof opposite the digging boom, a second pair of traction wheels recessed in said protrusions and generally under the point of pivoting of said boom, a slow speed high torque driving connection for coupling the prime mover to the traction wheels for creeping movement of the trencher with the blades in digging engagement with the ground, handles on said body at the end opposite said boom for manually guiding the trencher, a pair of transport Wheels outboard of said trencher body and mounted on an axis intermediate the axes of the traction wheels, and means for shifting said transport Wheels downwardly for supporting the trencher with the traction wheels elevated above the ground.

5. In a trencher the combination comprising a body of generally box shape terminating at one end in a pair of hollow box-like protrusions defining a vertical opening between them, a digging boom having one end arranged in said opening and journaled in said protrusions to permit vertical swinging movement of the boom, said boom having a series of movable digging blades, a prime mover in said body coupled to the digger blades, a first pair of traction wheels mounted outboard of the body at the end thereof opposite the digging boom, a second pair of traction wheels recessed in said protrusions and generally under the point of pivoting of said boom, a sloW speed high torque driving connection for coupling the prime mover to the traction wheels for creeping movement of the trencher with the blades in digging engagement with the ground, a pair of transport wheels outboard of said trencher body and partially overlapping the wheels in said protrusions, and means for shifting said transport wheels downwardly beyond the traction wheels.

6. In a trencher the combination comprising a body of generally box shape having at one end a pair of hollow box-like protrusions defining a vertical opening between them, a digging boom having one end arranged in said opening and having laterally extending trunnions, bearings in said protrusions journalling said trunnions to permit vertical swinging movement of the boom, said boom having a series of movable digger blades, a prime mover in said body having means for driving the digger blades, a first pair of traction wheels mounted outboard of the body at the end thereof opposite the digging boom, a second pair of traction wheels recessed in said protrusions and generally under the point of pivoting of said boom, a slow speed high torque driving connection for coupling the prime mover to the traction wheels for creeping movement of the trencher with the blades in digging engagement with the ground, the ends of said protrusions being separable from the body to serve as bearing caps and upon removal to permit access to the interior of said protrusions.

7. In a trencher the combination comprising a body of generally box shape having at one end a pair of hollow box-like protrusions defining a vertical opening between them, a digging boom having one end arranged in said opening and journaled between said protrusions to permit vertical swinging movement of the boom, said boom having a series of movable digger blades, a prime mover in said body having means for driving the digger blades, a first pair of traction wheels mounted outboard of the body at the end thereof opposite the digging boom, a second pair of traction wheels recessed in said protrusions, a slow speed high torque driving connection for coupling the prime mover to the traction wheels for creeping movement of the trencher with the blades in engagement with the ground, and a pair of independently 15 rotatable transport wheels outboard of said trencher body having means for vertically shifting the same into lowered transport position.

8. In a trencher the combination comprising a body of hollow box shape, a digging boom having movable digger blades and mounted on said body, a prime mover on said body having means for driving the blades on the digging boom, a first pair of traction wheels mounted outside of the body, a second pair of traction wheels mounted inside of the body spaced from the first pair, a slow speed high torque driving connection for coupling the prime mover to the traction wheels, a pair of transport wheels mounted outside of the body between the traction wheels and at a position approximately alined with the center of gravity of the trencher, and means for locking the transport wheels in a lowered, trencher supporting position permitting the trencher to be maneuvered while totally supported on the transport Wheels.

9. In a trencher, the combination comprising a body, a digging boom having movable digger blades and mounted for vertical rocking movement at the rear end of said body, a prime mover on said body having means for driving the blades on the digging boom," fore and aft pairs of traction wheels on said body for supporting the same during operation of the digger blades, a slow speed high torque driving connection for coupling the prime mover to the traction wheels, a pair of transport wheels rotatably mounted on said body along a transverse axis intermediate the pairs of traction wheels, said transport wheels having means for positioning the same with respect to the body so that they project beyond the support plane defined by the traction wheels, a tow bar at the front end of the body and having a hitch connection for securing the front end of the tow bar to a tractive vehicle for transport from job to job, and means for vertically adjusting the elevation of the hitch with respect to the body of the trencher so as to provide substantially equal clearance for the traction wheels under conditions of transport regardless of the elevation of the hitch point on the vehicle.

10. In a trencher the combination comprising a body, a digging boom having movable digger blades and mounted for vertical rocking movement at the rear end of said body, a prime mover on said body having means for driving the blades on the digging boom, fore and aft pairs of traction wheels on said body for supporting the same during operation of the digger blades, a slow speed high torque driving connection for coupling the prime mover to the traction wheels, a pair of transport wheels rotatably mounted on said body along a transverse axis intermediate the pairs of traction wheels, said transport wheels having means for positioning the same with respect to the body so that they project beyond the support plane defined by the traction wheels for supporting the trencher during maneuvering and transport, handles at the front end of the body for manually guiding the trencher, a tow bar at the front end of the body and having a hitch connection for securing the front end of the tow bar to a tractive vehicle for transport from job to job, and means for telescoping the tow bar into an out-of-the-way position in said body during manual guidance of the trencher.

11. In a trencher the combination comprising a body, digging means including a boom and a digger chain on said body, a prime mover on said body having means for coupling the same to the digger chain, fore and aft pairs of traction wheels journaled in the body, a slow speed drive connection between the prime mover and the traction wheels, a pair of auxiliary transport wheels located on an axis between the traction wheels and vertically movable between an upraised position in which the traction wheels are clear of the ground and a lowered position in which the transport wheels are below the level of the traction wheels for total support of the frame for transport, means for mounting the transport wheels for vertical movement relative to the traction wheels, means including a double acting hydraulic actuator coupled to the mounting means for moving the same between limit positions, and locking means automatically engageable incident to the movement of the transport wheels into their lowered trencher supporting position so that the transport wheels are maintained in such lowered position independently of subsequent lack of pressure in the hydraulic actuator.

12. In a trencher the combination comprising a body, digging means including a boom and a digger chain on said body, a prime mover on said body having means for coupling the same to the digger chain, fore and aft pairs of traction wheels having respective shafts journaled in the body, a slow speed drive connection between the prime mover and the shafts of the traction Wheels, a pair of auxiliary transport wheels located on an axis between the traction wheels, a shaft cranked at its ends for mounting the transport wheels on the body, an operating crank on said shaft, pinned to the operating crank to move the transport wheels vertically between an upraised position in which the traction wheels are clear of the ground and a lowered position in which the transport wheels are below the level of the traction wheels for total support of the trencher for transport, a lost motion connection between the activator and operating crank, and locking means automatically engageable incident to the taking up of the lost motion following the swinging of the transport wheels into their lowered position so that the transport wheels are maintained in lowered trencher supporting position independently of subsequent lack of pressure in the hydraulic actuator.

13. In a trencher the combination comprising a body, digging means including a boom and a digger chain on said body, a prime mover on said body having means for coupling the same to the digger chain, fore and aft pairs of traction wheels journaled in the body, a slow speed drive connection between the prime mover and the traction wheels, a pair of auxiliary transport wheels located on an axis between the traction wheels, means including a crank for mounting said transport wheels on the body for movement downwardly beyond the traction wheels as the crank is swung to the end of its range of movement, a double acting hydraulic actuator pinned to the crank and having a limited amount of radial lost motion with respect to the latter, and an abutment on the body so positioned as to obstruct arcuate movement of the crank incident to the actuators taking up the lost motion so that the transport wheels are maintained in lowered frame supporting position independently of lack of pressure in the hydraulic actuator and so that subsequent movement of the actuator in the opposite direction is effective to free the crank from this abutment.

14. In a trencher, the combination comprising a body, a digging boom on said body and having movable digger blades, a prime mover on said body having means for driving the blades, fore and aft pairs of traction wheels on said body spaced from one another to provide stable support for the body, a step-down driving connection interposed between the prime mover and the pairs of traction wheels for normally driving the wheels in the same direction for slow advancement of the digging boom in the ground, handles on the body remote from the digging boom for manually guiding the trencher, a pair of transport wheels located intermediate the pairs of traction Wheels and having means for shifting the same between an upraised position clear of the ground and a lowered position below the level of the traction wheels and in which the vehicle may be balanced solely on the transport wheels, the transport wheels being independently pivoted to permit skewing of the trencher in one direction or the other, and means for reversing the slow speed drive connection to one of the pairs of traction wheels for causing the pairs of traction wheels to rotate in opposite directions so that the operator simply by tilting the body forwardly or backwardly about the transport wheels 17 18 may bring a selected pair of the traction wheels into 2,777,2 19 Brant Jan. 15, 1957 grazing contact with the ground to maneuver the trencher 2,828,557 Brown Apr. 1, 1958 forwardly and backwardly into a desired position.

FOREIGN PATENTS References Cited in the file of this patent 5 573 251 Great Britain June 4 1952 UNITED STATES PATENTS OTHER g g ggg 1,722,5351 Matter Jul 30, 1929 L 2,748,504 McIm-nch g 5, 1956 C1v1l Engmeenng, July 1957, vol. 27, No. 7, Model 2,751,698 Brown June 26, 1956 M Ditch-Witch Trencher, pages 124 and 125 relied on.

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