US3192972A - Opposed piston cutting apparatus - Google Patents

Description

July 6, 1965 w. L. TENNEY OPPOSED PISTON CUTTING APPARATUS 2 Sheets-Sheet 1 F'ilecl June 29, 1961 mm mm Mn L M m M W ATTORNEYS y 1965 w. TENNEY 3,192,972

OPPOSED PISTON CUTTING APPARATUS Filed June 29. 1961 2 Sheets-Sheet 2 INVEN TOR.

WILLIAM L. TENNEY ATTORNEYS United States Patent l 3,192,?72 @PPOhEE CUTTENG APPARATUS William L. Tenney, (Irystal ham'l vfinn. Filed June 29, 1961, Ser. No. 129,696 Qlaims. (Cl. 143-63} This invention relates to portable self-powered cutting devices, such as power saws and the like, operated by novel internal combustion apparatus.

The present invention is particularly directed to power saws and cutting machines of the reciprocating blade type, which are capable of effective cutting operation where space .is limited, and in which the motive power for reciprocating the cutting blades is so obtained that vibration is substantially minimized. Thus, by utilizing two cutting blades reciprocating side by side in parallel but opopsite directions, and driving each of the blades respectively from one of the opposed pistons of a dual opposed piston internal combustion engine, the masses of the piston, and of the connected blades, will move in opposite directions and tend to cancel the inertia efiects of each other, with a consequent substantial reduction in vibration.

Such a direct transmission of motive power to the blades provides a basically more efficient power transmission arrangement, since friction losses are minimized and the size and weight of the apparatus can be significantly reduced. Furthermore, reaction forces generated by contact of the cutter blades against the material being cut can be self-canceling.

In this connection reference is made to copending application Serial No. 791,107, filed February 4, 1959, now Patent No. 3,023,564, of which this application is a continuation-in-part. In said parent application there is disclosed a novel'internal combustion mass reaction engine in which the piston and cylinder members are mounted for relative movement on a supporting frame or the like, and wherein there is a direct power output connection from one of these members to a reciprocating cutter blade, which blade thus moves concurrently with the member by which it is driven. The supply of fuel, i.e., a combustible fuel-air mixture in the case of a carburetor fed engine, is accomplished, as disclosed in said parent application, through a flexible tube extending between the carburetor and the cylinder member. In the present invention, such a flexible connection can be eliminated. Accordingly, the primary object of this invention is to provide a novel internal combustion engine drive for reciprocating cutting devices, particularly saws and the like.

Another object of the invention is to provide such a drive in which oppositely reciprocating cutting baldes are employed, and such blades are driven respectively by opposed and oppositely moving pistons of an internal cornbustion engine having a combustion chamber formed by a cylinder and opposed pistons therein, thus substantially minimizing vibration due to reciprocation of these parts of the drive.

Another object of the invention is to provide a novel, lightweight, portable power saw having reciprocating cutters. a V

' a An additional object of the invention is to provide a .novel direct drive arrangement between a piston engin and a reciprocating cutter blade.

Other objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.

' In'the drawings- FIG. 1 is a perspective view of a typical configuration rof a'portable power saw incorporating the features of the present invention;

3,l2,9l2 Patented July 6, 1965 FIG. 2 is a view, partially broken away, taken on a vertical section line through the saw shown in FIG. 1;

FIG. 3 is a partial sectional view taken on line 3? of FlG. 2;

FIG. 4 is an enlarged detail sectional view taken on line 4-4 of FIG. 2;

FIGS. 5 and 6 are schematic views illustrating movement of the parts during operation of the saw;

FIGS. 7 and 8 are schematic showings of modified engine constructions; and 7 FIGS. 9 and 16 are, respectively, front and side views showing the principles of the invention applied to another form of cutting machine, a reciprocating cutter bar mowing machine.

Referring to the drawing, which illustrates a preferred embodiment of the invention, the main body of the saw is provided by a cylinder member 13 which may be cast from suitable metal or machined, as desired, and may have cooling fins 1:. formed thereon. A pair of handles 12 are mounted on hands 13 clamped in any suitable manner around the body it} for grasping by the user to sup port and guide the device. Within the body 19, formed with its longitudinal axis eccentric with respect to theiaxis of the body itself, is an engine cylinder is", and within this cylinder there are opposed pistons 16 and 13, which may include conventional sealing rings (not shown) providing the usual sliding seal between their outer surfaces and the walls of the engine cylinder. These pistons, in cooperation with the cylinder 15, define a variable volume power cylinder which provides space Ztl for combustion and expansion ofcombustible charges.

A suitable igniter, such as an ignition plug 22 is mounted to extend through a side wall of the cylinder 15 for the purpose of igniting combustible charges within the cylinder. This plug can be energized in any known manner, such as by a battery or a magneto (not shown). These charges are introduced through an inlet port 24 controlled by piston 18, and products of combustion are exhausted from the cylinder through an exhaust port 25 controlled by piston 16. The timing of the opening and closing of these ports, and their relative length (thus the duration during which they are uncovered) may be varied in accordance with well known practice regarding engines of'this type, operating on the two-cycle principle.

Combustible charges are supplied from a carburetor 27 through an inlet manifold 28 which opens into an elongated transfer port or passage 34?. Details of a suitable carburetor are disclosed in said parent application.

Passage 3i? communicates with the inlet port 24 and with the spaces behind each of the pistons 16 and 17. These spaces are closed respectively by a finned head member 32- and a transverse partition 33, thus defining scavenging -pump chambers the volume of which is varied by disr, placement of the respective pistons to draw in charges through a check valve (not shown) in the carburetor when the pistons move toward each other, and to pump charges through port 24 as the pistons separate due to combustion of a charge in the space 20.

The movement of these pistons is exposed, in each case, by a biasing member, and such member may conveniently be provided in the form of a spring 36 acting upon piston 16 and a spring 38 acting on piston 18, tending to drive the pistons toward each other and compressing charges in the space 20. Other equivalent biasing means a may be provided if desired in place of these springs.

The pistons are shown in FIGS. 1 and 2 at approximately the outer limits of their travel relative to the cylinder member ill, or in other Words, at the normal end of their power stroke resulting from combustion of a charge in space M). The springs 36 and 38 are thus shown essentially fully compressed, and it will be noted also that the pistons have overtraveled the ports 24 and 25 to some extent. This arrangement is preferred since it assures good breathing of the engine even when there is a misfire or a sudden overload is placed on the engine.

Furthermore, it Will be noted that exhaust ports 25 are somewhat larger than the intake ports, and the exhaust ports are so arranged that they normally are uncovered first as the pistons separate on their power stroke. A satisfactory arrangement has been obtained in this regard when the opening of the exhaust ports precedes opening of the intake ports by about ten percent of the normal efiective travel of piston 16. Ample intake area can be provided by increasing the number of intake ports around the cylinder, and these ports can be directed at any desired angle with reference to the cylinder axis, in accordance with known practice in the art of ported engines operating on the two-cycle principle.

An output rod 40 is secured to piston 16 and extends forwardly of the body it? through baflle 33, extending through a seal bushing 41 therein. Similarly, an output rod 42 is fastened to piston 18 and extends through piston '16, having a seal therewith as by suitable sealing rings or the like (not shown), and thence through the battle 33, through a seal bushing 43 at this point. The rods 49 and 42 carry respective registration racks 45 and 46, and these racks in turn mesh with a common pinion 43 which is mounted free to rotate upon a cross shaft 49 within the forward chamber of the body. This rack and pinion construction normally does not serve to transfer any power, but merely acts to maintain proper relative movement and registry between the pistons 16 and 18.

Mounted over the forward chamber of the body is a fuel supply tank 59 inciuding filler tube 51 closed by a cap 52. The tank is supported spaced from the chamber on straps 53, to minimize heat transfer to the tank. Fuel for forming combustible charges is transferred from this tank through supply pipe 54 to carburetor 27 Connected to the rods 4% and 42 through the racks 45 and 46, and also providing a suitable mounting for such racks, are the reciprocating output or driving members 5-6 and 58 which are thus directly coupled to the pistons 16 and 18, respectively. These members may be formed conveniently as complementary semi-cylindrical rods which extend through a guide bearing 59 (FIG. 2) in the forward end of the housing, and it will be understood that these members move parallel to each other but in oppositedirections, according to the movement of the corresponding pistons.

Bolted or otherwise secured to each of these output members are the cutting blades 60 and 62, secured respectively to the output members 56 and 53. Thus, these lades will reciprocate parallel to each other, but in opposite directions, as the pistons 16 and 18 reciprocate, and the cutting teeth will therefore function accordingly. In order to maintain these blades parallel and closely together, as desired, a suitable guiding mechanism is incorporated therewithin, the blades being grooved or notched as shown at 63 to produce a chamber of appro priate length internally of (i.e., between) the blades 60 and 62. The blade 62 has a guide part 65 fastened thereto and including reversely curved ends forming gibs 66. These ends are received in U-shaped guide members or tracks 68 which are fastened to blade 69 in any suitable manner. Thus, the parts 66 slide within the members 68 and provide guides which hold the blades in closely aligned and parallel position during operation thereof.

The operation of a portable saw constructed in accord- I ance with the invention can be understood by reference to H68. 5 and 6 of the drawing. Fuel is supplied from tank 59 to the carburetor 27, and the combustible mixture from the carburetor passes through intake manifold 28 to the transfer passage 30. Assuming that the biasing springs 36 and 38 are effective to move the pistons 16 and 18 respectively toward the center of cylinder 15, "the clearance volume is indicated as the central portion of the combustion space 26, at which point the ignition plug 22 is located. In practice no particular stop mechanism is usually needed to maintain separation of the pistons at this time, since the compression of the combustible mixture will resist the biasing force of the springs and maintain sufficient clearance volume. The combustible mixture at this time is passing to the volumes behind the respective pistons, into what may be conveniently termed scavenging pump chambers.

When the mixture is ignited between the pistons the resultant pressure of the expanding products of combustion will cause the pistons to separate and will produce corresponding power output strokes of the blades 60 and 62, in the directions indicated in FIG. 6. As the pistons separate they of course act against the bias of the springs and will store a certain amount of energy therein as well as supplying the power to the cutting blades. The power so stored in the springs is returned in large measure to the engine system in producing the opposite or compression stroke of the engine, and thus the action of the springs may be considered analogous to that of the flywheel on a conventional internal combustion engine with a rotating crank shaft. When the pistons separate sufiiciently, piston 16 will first uncover the exhaust ports 25 and the hot gases will commence to exhaust from the cylinder supply ahead of the uncovering or opening of the intake ports 24 by cylinder 18. This general scheme of operation is known in the art, and is sometimes referred to as a uniflow scavenging arrangement. Of course, at this time the fresh charges of combustible mixture, having been drawn into the scavenging pump chambers behind the pistons upon the compression stroke thereof, will be pumped out of such chambers throtwh the transfer passage 30 and will enter the cylinder through the intake ports 24. A check valve is provided in the carburetor system to avoid reverse flow therethrough at this time, as is well known in the art, and as disclosed in detail in said copending application.

It was noted above that the springs 36 and 38 have a function similar to a flywheel. In addition to returning energy for purposes of moving the pistons in their compression stroke, some of the stored energy is applied through the outputs 56 and 58 to the cutting blades, and their return or opposite stroke, in the directions indicated in FIG. 5, is thus accomplished also under power. Thus, the present invention provides a compact, lightweight and efficient power saw apparatus wherein the direct connection of reciprocating saw blades to the opposed pistons affords an efficient means for transferring energy from the opposed pistons of the engine directly to the cutting blades, with friction losses considerably reduced with respect to the normal type of rotary engine drive and output. Moreover, by utilizing opposed pistons connected to oppositely moving reciprocating cutter blades, and by maintaining the movement of the pistons in synchronism, as through the rack and pinion registering mechanism disclosed, the masses of the pistons react in opposite directions and vibration of the apparatus is accordingly minimized to a great extent, and reaction forces generated by contact of the cutter blades against the material being out are essentially self-canceling.

The apparatus also is of minimum cross section, as will be apparent particularly from inspection of the drawings, and thus is easily supported and maneuvered by a single operator. The handles 12 and their mounting straps can be rotated and fixed in any convenient position around the cylinder member, as can the fuel supply tank 50. If it'is found necessary to maintain the carburetor in an upright position, it too can be mounted for adjustment about the cylinder, and a portion of the intake manifold 28 can be formed of flexible tubing to accommodate such movement of the carburetor. Therefore, the cutting edge of blades 60 and 62 can be directed as desired with respect to the handles and the position of the operator.

The invention also provides a novel arrangement for starting the engine. A fitting '74} (FIG. 2) incorporating a normally closed check valve (not shown) is mounted in the cylinder body adjacent ignition plug 22. This fitting provides a means for injecting gas under pressure, as from a manual air pump, into the combustion space to initiate movement of the pistons. If desired, such gas may be in the form of a combustible mixture provided by adding a vaporized or atomized liquid fuel, or a gaseous fuel such as propane, t0 the air from such pump. Details of apparatus suitable for this purpose are disclosed in said parent application, and some of such apparatus is also shown in the embodiment of this invention illustrated in FIG. 10, as will presently be described. If desired, in portable devices such as the saw just described, the starting apparatus can be provided as a detachable unit. For example a quick-disconnect coupling can be incorporated in the fitting '70 to engage with an air pump during starting and then be disconnected when the engine is running. Alternatively, the starting apparatus can be permanently attached as an inte ral part of the device.

FIG. 7 and FIG. 8 disclose modified forms of engine construction which can be used in accordance with the present invention. For purposes of simplification, only the essential elements of the engine are shown in schematic form, but it will be understood that the usual fuelair supply system may be provided, and suitable output connections can be made from the pistons, as will be described. Thus, referring to FIG. 7, the cylinder body 153:: is provided with opposed pistons 16a and 18a. In this particular arrangement, intake ports and exhaust ports are controlled by each piston, and thus for purposes of of explanation at the top portion of the cylinder 1601, as shown in FIG. 7, the intake ports 24a are connected to the transfer passage 30a which in turn connects to the scavenging pump chambers behind the pistons, and which also is connected to the combustible mixture supply device.

At the sides of the cylinder there are exhaust ports 25a, controlled by each piston, and of slightly greater dimension than the intake ports such that the exhaust ports are uncovered first by the moving pistons toward the end of the power stroke. The output. connections are provided by the rods 43a and 42a, connected to the pistons 16a and Ida respectively. These rods may be connected to reciprocating cutter blades or other apparatus to be driven in reciprocating fashion by the en- "gine, and the rack and pinion registry mechanism can be used in such power output connection. However, in some instances stable operation of the engine can be attained without the use of such registry mechanism, and it should be understood therefore that this mechanism is not an essential feature of the invention.

Similarly, with reference to FIG. 8, another form of engine in accordance with the invention may include a' cylinder ltlb in which pistons 16b and 18b operate in opposition, but wherein only one of these pistons controls the intake and exhaust. Thus, for purposes of explanation the intake ports 24]; are shown adjacent the upper portion of the cylinder to be covered and uncovered by the piston 18]), and likewise the exhaust ports 25b are formed at the same end of the cylinder to be controlled by piston 18b. In other respects, the engine is of the same general type, and functions in essentially the same manner.

The present invention, while particularly applicable to light portable power saws, also can be applied to the construction of other lightweight efficient cutting devices such as mowing machines having reciprocating cutting blades. By way of example, FIGS. 9 and 10 show generally such a machine wherein a framework is provided including front legs 1% which carry a front axle 182 on which are mounted wheels 1103. Rear legs 104 extend from the front legs of the framework, and are steadied by brace members 105. The rear legs support rear wheels 196.

The engine cylinder (FIG. 9) is mounted on brackets 112, these brackets in turn extending from the framework,-and pistons 116 and 118 operate within the cylinder 110 in the same manner as the motors previously described. The springs 136 and 133 act against the respective pistons in the same manner, and the output rods 14%) and 142 are connected to extension rods 143 and 144 zhich in turn may carry the registry control racks 145 and 146, in mesh with the freely rotatable pinion 148. Rod 143 is fastened at its lower or outer end to a lower clipper or cutter bar res, and extension rod 144- is in turn suitably fastened to an upper clipper bar 162.

These clipper or cutter bars are mounted between stationary clamping or holder bars 165, and tensioning bolts 167, provided with suitable Belleville or spring washers 158, extend between the clamping bars and through guide slots in the cutter bars to maintain the cutter bars parallel and in close sliding relation. The bolts 167 can be adjusted to provide the desired tension in the spring washers for determining the clamping force with which the cutter blades or bars are held together.

The handle 17d of the mowing machine preferably includes a tubular portion 172 within which a pump piston 173 operates under control of a pump handle 175. This construction provides a simple starting air pump which may be connected to the starter fitting 177 (FIG. 9) in cylinder lit for conducting starting gas under pressure into the engine. As mentioned previously, further details 'of such a' starting system are disclosed in said copending application.

The engine and cutting mechanism disclosed in FIGS.

9 and 10 operates on the same general principle as the previously described power saw apparatus. The pistons 116 and 118 separate under the force of combustion of a charge in the cylinder, storing some energy in the springs 13$ and 138, and transferring some energy, to the cutter bars providing a cutting stroke. the exhaust and intake ports of the engine as described. On the return or compression stroke the energy from the springs is returned in part to the pistons for compressing a charge in the cylinder, and further energy is supplied from the springs to the cutter bars to produce power on the return stroke thereof.

While the forms of apparatus herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise forms of apparatus, and that changes may be made therein 'without departing from the scope of the invention which combustible charges, means for introducing fresh charges into said space and for exhausting products of combustion from said space in timed relation to movement of said piston, means for supplying a combustible mixture to said charge introducing means including a fuel tank and a car- The pistons also control it to compress a combustible charge introduced into said space between said pistons while driving said blades in a return stroke.

2. A self-contained reciprocating cutting device comprising a main housing, an engine cylinder formed in said housing, a pair of cutting blades extending from one end of said housing and having cutting teeth in side by side relation adapted to reciprocate in opposed parallel directions producing a cutting action, a pair of opposed drive pistons in said cylinder defining therebetween a space for combustion and expansion of combustible charges, means for introducing fresh charges into said space and for exhausting products of combustion from said space in timed relation to movement of said pistons, means connecting one of said pistons to a corresponding one of said blades and the other said piston to the other said blades for concurrent movement thereof producing opposed cutting movements of said blades in response to movement of said pistons, energy storing means acting upon said pistons in opposition to the force resulting from combustion of a charge in said cylinder for storing energy and returning it to compress a combustible charge introduced into said space between said pistons while driving said blades in a return stroke, and register means connected to said pistons maintaining properly phased relative movement between said pistons.

3. A portable self-contained power saw comprising a main housing including means for manual grasping to support and guide the saw, an engine cylinder formed in said housing, a pair of cutting blades extending from one end of said housing and having cutting teeth in side by side relation adapted to reciprocate in opposed parallel directions producing a cutting action, a pair of opposed drive pistons in said cylinder defining therebetween a space for combustion and expansion of combustible charges, means for introducing fresh charges into said space and for exhausting products of combustion from said space in timed relation to movement of said pistons, means connecting one of said pistons to a corresponding one of said blades and the other of said pistons to the other of said blades for concurrent movement thereof producing opposed cutting movements of said blades in response to combustion of charges in said space, means acting upon said pistons in opposition to the force resulting from combustion of a charge in said cylinder tending to compress a combustible charge introduced into said space between said pistons and driving said blades in a return stroke.

4-. A portable self-contained power saw comprising a main housing including means for manual grasping to support and guide the saw, an engine cylinder formed in said housing, a pair of opposed drive pistons in said cylinder defining therebetween a space for combustion and expansion of combustible charges, means for introducing fresh charges into said space and for exhausting products of combustion from said space in timed relation to movement of said pistons, 21 pair of cutting blades extending from one end of said housing and having cutting teeth in side by side relation adapted to reciprocate in opposed parallel directions producing a cutting action, means connecting one of said pistons to a corresponding one of said blades and the other said piston to the other said blade for concurrent movement thereof producing opposed cutting movements of said blades in response to movement of said pistons from combustion of charges, energy storing means acting upon said pistons in opposition to the force resulting from combustion of a charge in said cylinder, and a register device correlating the movement of said pistons to maintain proper phase relation between said pistons and the respectively driven cutting blades.

5. In a self-contained reciprocating cutting apparatus having a main housing, an engine cylinder formed in said housing, a pair of opposed drive pistons in said cylinder defining therebetween a space for combustion and expansion of combustible charges, a pair of coacting parallel cutting blades, one of said cutting blades connected to one of said drive pistons and the other of said cutting blades connected to the other of said drive pistons for reciprocating movement therewith, means for introducing fresh charges into said space and for exhausting products of combustion from said space in timed relation to movement of said pistons, energy storing means acting upon said pistons in opposition to the force resulting from combustion of a charge in said cylinder and for storing energy and returning it to compress a combustible charge introduced into said space between said pistons while driving said blades in a return stroke, and a starter including means for initially supplying a combustible charge under .pressure to said space acting to separate said pistons from their normal at rest position.

References Cited by the Examiner UNITED STATES PATENTS 1,349,698 8/20 Tompkins.

2,244,215 6/41 Pescara.

2,330,937 10/43 Varis 92-65 X 2,598,480 5/52 Wright.

2,876,751 3/59 Kolthotf 123-46 2,904,022 9/59 MacDonald 123-46 2,912,965 11/59 Campbell 123-46 3,023,563 3/62 Tenney 56-265 3,023,564 3/62 Tenney et al 56-265 WILLIAM w. DYER, JR., Primary Examiner.

WALTER A. SCHEEL, DONALD R. SCHRAN,

Examiners.

Claims (1)

1. A LIGHTWEIGHT PORTABLE, SELF-CONTAINED, RECIPROCATING CUTTING DEVICE COMPRISING A MAIN HOUSING HAVING MEANS FOR SUPPORTING AND GUIDING SAID HOUSING, AN ENGINE CYLINDER FORMED IN SAID HOUSING, A PAIR OF CUTTING BLADES EXTENDING FROM ONE SIDE OF SAID HOUSING AND HAVING CUTTING TEETH IN SIDE BY SIDE RELATION ADAPTED TO RECIPROCATE IN OPPOSED PARALLEL DIRECTION PRODUCING A CUTTING ACTION, A PAIR OF OPPOSED DRIVE PISTONS IN SAID CYLINDER DEFINING THEREBETWEEN A SPACE FOR COMBUSTION AND EXPANSION OF COMBUSTIBLE CHARGES, MEANS FOR INTRODUCING FRESH CHARGES INTO SAID SPACE AND FOR EXHAUSTING PRODUCTS OF COMBUSTION FROM SAID SPACE IN TIMED RELATION TO MOVEMENT OF SAID PISTON, MEANS FOR SUPPLYING A COMBUSTIBLE MIXTURE TO SAID CHARGE INTRODUCING MEANS INCLUDING A FUEL TANK AND A CARBURETOR MOUNTED ON SAID HOUSING, MENAS CONNECTING ONE OF SAID PISTONS TO A CORRESPONDING ONE OF SAID BLADES AND THE OTHER SAID PISTON TO THE OTHER SAID BLADE FOR CONCURRENT MOVEMENT THEREOF PRODUCING OPPOSED CUTTING MOVEMENT OF SAID BLADES IN RESPONSE TO MOVEMENT OF SAID PISTONS, AND ENERGY STORING MEANS ACTING UPON SAID PISTONS IN OPPOSITION TO THE FORCE RESULTING FROM COMBUSTION OF A CHARGE IN SAID CYLINDER FOR STORING ENERGY AND RETURNING IT TO COMPRESS A COMBUSTIBLE CHARGE INTRODUCED INTO SAID SPACE BETWEEN SAID PISTONS WHILE DRIVING SAID BLADES IN A RETURN STROKE.

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