US3506041A - Pneumatic sealing control system for strapping machines - Google Patents

Description

April 1970 B. R. ANGAROLA 3,506,041

PNEUMATIC SEALING CONTROL SYSTEM FOR STRAPPING MACHINES Filed June 5, 1968 5 Sheets-Sheet 2 I/V VEN T0R BARRY R. ANGAROLA By dwmL Q. 8%

April 14, 1970 B. R. ANGAROLA 3,506,041

PNEUMATIC SEALING CONTROL SYSTEM FOR STRAPPING MACHINES Filed June 5, 1968 5 Sheets-Sheet 5 22| 2423? 236 FIG 5 220 April 14, .1970 B. R. ANGAROLA 3,506,041

PNEUMATIC SEALING CONTROL SYSTEM FOR STRAPPING MACHINES 5 Sheet-Sheet 4 Filed June 5. 1968 MIMI I I 2 I WWW I/V VENTOR BARRY R. A/VGAROLA April 14, 1970 B. R. ANGAROLA 3,506,041

PNEUMATIC SEALING CONTROL SYSTEM FOR STRAPPING MACHINES 5 Sheets-Sheet 5 Filed June 5, 1968 United States Patent Oihce 3,506,041 Patented Apr. 14, 1970 3,506,041 PNEUMATIC SEALING CONTROL SYSTEM FOR STRAPPING MACHINES Barry R. Angarola, Franklin Park, Ill., assignor to Signotle Corporation, Chicago, 11]., a corporation of Delaware Filed June 3, 1968, Ser. No. 734,138 Int. Cl. B21f 21/00 U.S. Cl. 140-934 18 Claims ABSTRACT OF THE DISCLOSURE A cyclicly operable pneumatic heavy duty strapping tool for tensioning a loop of steel strapping about an object, applying a seal to the overlapping portions of the strapping, crimping the seal to unite such portions, and severing the loop from the source of strapping, wherein that portion of the cycle which applies the seal, crimps it, and severs the strapping is initiated automatically when a predetermined desired degree of tension in the strapping loop is attained. Depression of a single start button or lever thus initiates the complete tool cycle and no secondary manual operations are required during the remainder of the cycle.

The present invention relates to package binding tools, commonly referred to as strapping tools, and by means of which a loop of flexible metal strapping which has been caused to encircle an article, or series of articles, is tensioned and thereafter a seal which has been positioned about the overlapping end regions of the loop is crimped or otherwise deformed to provide a seal joint, after which the feed end region of the strapping is severed to free the tensioned loop and article encircled thereby from the source of strapping.

Strapping tools embodying the principles of the present invention will find particular application in applying heavy duty strapping, i.e. fiat steel strapping having a width of three-quarters of an inch or greater, and a thickness between .031 and .050 inch, as well as plastic strapping having a Width on the order of one inch or greater. However the invention is not limited to such use and narrower and thinner grades of strapping, either steel or plastic, may be accommodated by the present invention, with or Without modification as required. Furthermore, the invention is not necessarily limited to use with flat strapping material. Therefore, throughout this specification and in the appended claims, it is intended that the term strapping shall be broadly construed to cover a wide variety of elongated binding materials capable of being formed into a loop for articleor bundle-encircling purposes and including flat ribbon-like materials as well as wire, cord and the like.

Basically, the present strapping tool embodies many of the features of existing strapping tools which are designed to operate upon heavy duty strapping. For example, because of the fact that the use to which such strapping is put requires a greater degree of tensioning than may be conveniently attained by manual force, pneumatic power is employed for effecting the seal applying and crimping operation, as well as the strap-severing operation, and this power is applied through opposed crimping jaws in a manner similar to that employed in connection with certain prior strapping tools.

The adoption of the above-outlined previously used features of strapping tool operations and the employment of a more or less basic or standard strapping tool design which, in outward appearance at least, renders the present strapping tool similar to other known strapping tools is an advantageous feature of the present invention for the obvious reasons that since no new manipulative skills are required for its operations, sales appeal is therefore enhanced, and the tool may be manufactured on a production basis by modification of only a few tool components, the tool otherwise being constructed largely from available stock parts on inventory for conventional tools. If desired, the present strapping tool may be manufactured and sold as original equipment or it may be constructed by the modification of certain components of existing tools designed for the same purpose.

The present invention has, for exemplary purposes, been shown and described'herein as being applied to a strapping tool of the general type disclosed in U.S. Patent No. 3,198,218, granted on Aug. 3, 1965 and entitled Strapping Tool. The invention is however not limited to this specific type of tool and the same may, if desired, by suitable modification, be applied to numerous other types and forms of pneumatically operable strapping tools, the only requisite being that the tool embody a strap tensioning feed wheel which is driven by a pneumatic motor and that it be equipped with seal applying instrumentalities effective to seal together the overlapping portions of a strap loop after a predetermined degree of tension has been attained in the strapping loop. Irrespective therefore of the particular use to which the invention may be put, the essential features thereof are at all times preserved.

A strapping tool of the type with which the present invention is concerned, and specifically a tool of the type disclosed in the aforementioned Ericksson Patent No. 3,198,218, is semi-automatic in its operation in that it employs two sets of instrumentalities, each of which requires a manual operation for setting the same in motion. The first of these which is effective to completion by depression of a lever, releases a latched feed wheel so that it moves into operative engagement with the strapping for tensioning purposes and supplies pressurized air to a pneumatic tensioning motor to rotate the feed wheel and progressively shrink the strapping loop about the article undergoing strapping. The operation of this first set of instrumentalities is completed when the tensioning motor stalls due to the resistance to feed Wheel turning offered by the fully tensioned strapping. At this time, a second lever is depressed and the second set of instrumentalities is set into motion and serves to apply a metal seal to the overlapped portions of the now tensioned loop of strapping, crimp the seal about such portions to unite the same, sever the loop from the source of strapping, and restore the various moving parts thereof to their initial positions, while at the same time loading the seal applying and crimping mechanism with a fresh seal for use in a succeeding strapping operation. The two sets of instrumentalities function independently of each other during the actual strapping operation but, after such operation is complete, the second set of instrumentalities is effective not only to restore its moving parts to their initial positions but also is effective to restore the moving parts of the first set. Such semi-automatic tool operation as has been briefly outlined above is, of course, exclusive of initial loading operations wherein the tool is positioned against the article undergoing strapping, the loop is created, the overlapping portions of the loop are properly juxtapositioned with respect to the tool frame and the tensioning wheel, and any other operations which must necessarily be manually performed in connection with any portable tool preparatory to initiating the tensioning operation.

Pneumatic strapping tools of the character set forth in the Ericksson Patent No. 3,198,218 have been found to be extremely effective for the heavy duty strapping of large articles or bundles but nevertheless they are possessed or certain limitations which it is the aim of the present invention to obviate. Principal among these limitations is the fact that to effect a complete strapping cycle, the operator is obliged to be in attendance during the entire strapping procedure. After depression of the first lever, he is obliged to await completion of the tensioning operation when the motor stalls so that he will be available to depress the second lever and initiate the seal applying and crimping operation. Additionally, the use of two-lever operation is not conducive toward uniformly strapped articles or bundles inasmuch as many operators, in an effort to save time, will depress the second lever before complete motor stall, thus initiating the seal crimping operation before full tension is attained in the strapping loop= Complete motor stall is not a phenomenon that can readily be ascertained, either visually or by a sense of hearing in which the character of the motor noise changes. Since the feed wheel is visible only at certain tool angles and with good illumination, visual determination of feed wheel stalling is not a reliable phenomenon on which to base a conclusion that the tool is ready for the seal crimping operation. Similarly, the noise characteristics of different pneumatic motors are not uniform so that a sound which, to one operator, would indicate motor stall, might not be audible or recognizeable to another operator. By the same token, if audible signals from a motor are relied upon for second lever depression, certain motors are capable of emitting sta'll simulating signals when, in fact, the motor is not in stall but only nearly so. Extraneous noises also are deceiving and may result in premature initiation of the seal crimping operation. Whatever may be the cause of premature seal crimping, the practice of either voluntarily or involuntarily initiating the seal crimping operation is a common one and has resulted in poorly strapped articies or bundles which are inadequate for handling during transportation.

Another limitation that is attendant upon the use of conventional pneumatically operable strapping tools resides in the fact that when motor stall is relied upon for initiation of the strapping operation, variation in strapping tension to accommodate different types of articles or bundles is attained by varying the pressure of air supplied to the tensioning motor. Such a procedure necessitates adjustment of the pressure regulator which controls the ressure of air delivered to the tool and which is variably located at a point remote from the scene of strapping operations.

The present invention is designed to overcome the above noted limitations that are attendant upon the construction and use of conventional pneumatically operable strapping tools and, toward this end, the invention contemplates the provision of a novel strapping tool which is substantially fully automatic in its operation and requires depression of but one starting button or lever for the initiation of a complete strapping cycle, followed by automatic restoration of all tool parts and instrumentalities to their initial positions preparatory to the next succeeding strapping operation. By reason of such single-lever operation, the operator is not required to be in full attendance during the entire tool cycle and from the time of initial depression of the starting lever until the strapping operation has been completed, the operator is free to perform extraneous functions in the vicinity of the strapping station, as for example making ready the next succeeding article to be strapped, or by labeling the package.

Automatic tool operation to the extent indicated above is attained according to the invention, not necessarily by relying upon complete motor stall for the attainment of proper strap tension as is the case with conventional strapping tools, but rather by sensing the back-up pressure which develops in the air supply line leading to the tensioning motor and which is a function of feed wheel resistance to strap motivation. When such back-up pressure attains a predetermined maximum as a result of resistance to normal feed wheel motion. and which does not 4 necessarily result in complete feed Wheel and motor stall, certain pneumatic functions are automatically set into operation, these functions resulting in initiation of the seal applying, crimping and strap cut-off operations, substantially in the same manner and sequencein which they are carried out by conventional strapping tools after the second operating lever is depressed as heretofore described. By such a procedure, uniform tensioning in the strapping loop associated with successively strapped articles or bundles is assured.

Still further, according to the invention, means are provided for reguably adjusting the back-up pressure sensing means so that it may be made responsive to varying and predetermined pressures, thus advancing or retarding the point in the tool cycle when the final seal crimping operation is performed. Advancing the time of seal crimping obviously results in less tension in the sealed strapping loop, while retarding such time results in greater tension in the loop: Even with a tensioning motor and feed wheel drive ratio which has the ability to exceed the breaking point of the strapping, the present invention makes possible safe and uniform strapping of articles or bundles by the simple expedient of adjusting the pressure sensing means to a point where the seal is applied and strap cutoff takes place at a point in the tool cycle where the tension in the loop is below the breaking point.

The provision of a pneumatic sealing control means for strapping machines such as has :briefiy been outlined above constitutes the principal object of the present invention.

The provision of a pneumatically operable seal applying and crimping control means wherein the component parts thereof consume but little space so that they may conveniently be housed within a small out-of-the-way enclosure which does not add appreciably to overall tool size; one which is comprised of a minimum number of moving parts and which therefore is unlikely to get out of order; one which is rugged and durable and which therefore will withstand any abnormal rough usage to which the tool may be put; one which is capable of ease of assembly and disassembly for purposes of inspection of parts, replacement or repair thereof; and one which, otherwise, is well adapted to perform the services required of it, are further desirable features which have been borne in mind in the production and development of the present invention.

Other objects and advantages of the invention, not at this time enumerated, will readily suggest themselves as the nature of the invention is better understood.

In the accompanying five sheets of drawings forming a part of this specification, one illustrative embodiment of the invention has been shown.

In these drawings:

FIG. 1 is a side elevational view of a pneumatic strapping tool embodying the principles of the present invention, the tool being illustrated with the operative parts thereof in the positions which they assume when air is first applied to the tool and the latter is in condition for immediate use;

FiG. 2 is a sectional view taken substantially along the line 22 of FIG. 1 and illustrating the nature of a tensioning valve assembly and a sealing valve assembly employed in connection with the invention;

FIG. 3 is a fragmentary perspective view of a limited portion of the tool in the vicinity of a closure cap which is applied to the tool housing and which encloses certain of the control instrumentalities of the present invention, a portion of the closure cap wall being broken away to more clearly reveal the nature of the invention;

FIG. 4 is an enlarged top plan view of the strapping tool with portions of the closure cap broken away to illustrate the nature of a certain pressure relief valve employed in connection with the invention;

FIG. 5 is a sectional view taken substantialy along the line 55 of FIG. 4;

FIG. 6 is a sectional view taken substantially along the line 66 of FIG.

FIG. 7 is a fragmentary front elevational view of the tool with portions of the casing wall broken away to reveal certain internal parts;

FIG. 8 is a fragmentary sectional view similar to FIG. 2 but showing the sealing valve in its operative or effective position;

FIG. 9 is a sectional view taken substantially along the line 99 of FIG. 4 and illustrating, specifically, the nature of a seal applying and crimping mechanism employed in connection with the invention;

FIG. 10 is an enlarged detail sectional view taken substantially centrally and longitudinally through a trip release valve employed in connection with the present invention and showing the valve in its normal inoperative position;

FIG. 11 is a sectional view similar to FIG. 10 showing the trip release valve in its operative position; and

FIG. 12 is a pneumatic circuit diagram, entirely schematic in its representation, showing the pneumatic control mechanism by means of which the tool is operated.

Referring now to the drawings, the sealing control system of the present invention has been illustrated therein as being applied to a portable pneumatically operable strapping tool of the type disclosed in the aforementioned patent to Ericsson et al., No. 3,198,218, the illustration being for exemplary purposes only since the principles of the system are applicable to other forms of portable pneumatic strapping tools, as well as to fully automatic strapping machines. For a full understanding of the nature and operation of the Ericsson et al. tool, reference may be had to such patent but in the present application, only such portions of the tool as are pertinent to the sealing control system have been illustrated herein, these portions being described only in suflicient detail as to afford an understanding of their relation to the present invention. However, the entire disclosure of such patent, insofar as it is consistent with the present disclosure, is hereby incorporated in and made a part of this application by reference thereto. Such modifications as are necessary to adapt the Ericsson et al. tool to the present invention have been described in detail.

Considering the drawings in detail and with particular reference to FIGS. 1, 2 and 4, the strapping tool 10 involves in its general organization a base frame or foot assembly 12 having a handle 14 secured thereto, extending upwardly and forwardly from the front end thereof, and terminating in a suspension hook 16 which overlies the center of gravity bf the tool, thus providing a support by means of which the tool as a whole may be suspended from an adjustable overhead convenience cable (not shown). An auxilliary reaction handle 17 is fixedly secured to the frame 12 for manipulative purposes. The base 12 is provided with a flat bottom surface 18 adapted to be supported on an article undergoing strapping and it is formed with a pair of spaced wings 20 and 22 which project laterally from one side of the base and provide a gap or void 24 therebetween which is of sufficient length to permit entry of the jaws associated with a sealing mechanism 30 (see also FIG. 9) for the purpose of applying and crimping a metal seal such as has been shown at S in FIGS. 1 and 9 around the flat overlapped portions of a fiat metal strap ST associated with a loop of strapping Which has been caused to encircle an article and which has been placed under tension preparatory to applying the seal. A series of the stacked seals S (FIG. 1), disposed in a seal magazine 32 are adapted to be fed successively to the jaws of the sealing mechanism 30 by means of an ejector arm 34 which engages the lowermost seal in the stack and pushes the same endwise between the jaws, all in a manner that will be described in greater detail presently.

Both the ejector arm 34 and seal magazine 32 are supported on a main frame or casting, various portions of which appear throughout the drawings and which have been designated severally at 36. The frame is secured by cap screws 38 to the foot assembly 12. The main frame 36 also serves to support a combined valve and cylinder housing assembly 40 which provides a cylinder section 42 and a valve section 44'. At the front of the base frame 12, an integral support projects upwardly and carries a transverse rock shaft 52 to which there is secured a tiltable frame 53 on which there is mounted a pneumatically operable tensioning motor M. The motor M is operatively connected through a gear reduction device 51 to a rotatable strap-tensioning feed wheel 54. The feed wheel 54 is carried on a shaft 55, and cooperates in the usual manner of feed wheel operation with a toothed anvil or backup pad 5-6 on the base frame and which grips the lower overlapping portion of the strap and holds the same fixed while the feed Wheel impels the upper portion of the strap in a strap-tensioning direction. The shaft 55 is carried on the frame 53' at a region below the level of the rock shaft 52 so that when rocking movements are imparted to the frame about the axis of the rock shaft. the feed wheel 54 may be raised and lowered out of and into cooperation with the back-up pad 56 while at the same time the tensioning motor M will be moved between a raised and a lowered position. A spring (not shown) encircles the rock shaft 52 and yieldingly biases the frame toward an operative position wherein the tensioning motor assumes the raised position in which it is shown in full lines in FIG. 1 with the feed wheel 54 engaging the strapping. An upwardly biased latch arm 58 pivotally connected to the motor cooperates with a latch pin 59 in releasably maintaining the motor in its lowered position as shown in dotted lines so that the feed wheel 54 is raised from the back-up pad 56 and strapping. The latch arm 58 projects forwardly of the frame 36 as shown in FIG. 1 and presents a laterally turned finger 60 (see also FIG. 7) which is accessible for manipulation at the front of the tool. The motor and feed wheel may be released from their latched position by manually lowering the latch arm out of latching engagementwith the pin 59. However, according to the present invention, the latch arm cooperates with a plunger 62 (FIGS. 2, 7 and 12) which slides in a cylinder 63 and is spring biased at 64 for the purpose of effecting automatic release of the arm at a point near the commencement of the tool cycle, all in a manner that will be described subsequently. At

the rear of the tool, a depressible spring biased lever 65 controls the raising and lowering movements of a rear toothed gripper element 66, the latter serving to anchor the free end of the strap at the time of initial loading of the tool. After the sealing mechanism 30 has been operated to effect crimping of the seal S about the overlapping portions of the tensioned loop of strapping, a cutter blade 67 which moves bodily in unison with a portion of the sealing mechanism 30, is caused to descend against a fixed cutter block 68 to effect shearing of the free end portion of the strapping to thus free the tensioned loop of strapping so that the strapped article may be removed from the strapping tool.

The housing assembly 40 involves in its general organization a relatively large upper cup-shaped casing 70, the upper open rim of which is closed by a closure head or plate 72 secured in position by bolts 73 (FIG. 4). The casing is internally compartmented to provide the cylinder proper 74 (FIG. 9) of the previously mentioned cylinder section 42, as well as to provide a pair of valve chambers 75 and 76 (FIG. 2). The bottom wall 78 of the casing seats upon and is secured by bolts 80 (FIGS. 1, 7 and 9) to the upper portion of the frame 36. The valve chamber 75 has associated therewith a tensioning valve assembly TV while the valve chamber 76- has associated therewith a sealing valve assembly SV. The nature and function of these two valve assemblies will be set forth in detail presently.

Referring now to FIG. 9, the sealing mechanism 30 is operable under the control of a vertically movable ram 100 associated with the cylinder section 42 of the housing 40 and which is provided with a stern portion 102 and an enlarged head portion 104. The stem portion 102 is fixedly secured to a piston 106 which is disposed within the cylinder 74 and projects through the bottom wall 78 thereof, the head portion being disposed exteriorly of the cylinder and being slidable in a vertical bore 112 provided in a jaw support 114. The lower end of the head portion 104 is bifuracted as shown at 116 and a transverse pin 118 extends across the bifurcations and serve to support he upper ends of a pair of toggle links 120. The lower ends of the toggle links are pivotally connected to a pair of coacting crimping jaw members 122 by means of pins 124. The jaw support 114 is formed with a depending side plate 123 which, in combination with the aforementioned cutter blade 67 (FIG. 1), establishes a cage-like enclosure for the two jaw members 122. Each jaw member 120 is pivoted intermediate its ends for swinging movement about a horizontal axis by means of a fixed pivot pin 126 which has its opposite ends secured in the cutter blade 67 and side plate 123 respectively. Conventional notcher bars 128 have their outer end regions pivoted to the jaw members 122 by means of free floating pins 130 and clearance slots 132 are formed in the notcher bars 128 for reception of the pins 130 therethrough. Small notches 134- are formed in the lower ends of the jaw members 122 and facilitate holding of the seals S as they are successively fed from the magazine 32 as heretofore described. The extent of maximum jaw opening is determined by the provision of a pair of opposed dogs 136 integrally formed on the jaw members 122 and which, when in contact with each other, maintain the jaws spaced apart a distance just wide enough to admit a seal S therebetween.

The head portion 164 of the ram 100 is formed with a tangentially extending notch 140 in its outer surface, this notch being designed for cooperation with a shoulder formed on a cam latch 142 in the form of a rock shaft carried by the jaw support 114. One end of the cam latch projects outwardly of the jaw support 114 and has a flattened surface 152 designed for engagement with a fixed lug 154 secured to a portion of the main casting 36, such engagement taking place as the support 114 and cutter plate 67 move downwardly in unison. At such time as the cam latch engages the lug, further downward movement of the jaw support is prevented but the angular turning movement of the cam latch 142 incident to such engagement shifts the shoulder out of the notch 140, thus freeing the ram for further downward movement. Thus, during initial downward movement of the piston 106 and ram 100, the support 114, cutter plate 67 and crimping jaw assembly are lowered bodily as a unit to carry the seal S downwardly into a saddle-like position of seating engagement with the overlapping portions of the strapping. During this initial downward movement no relative jaw motion takes place. After the cam latch 142 engages the lug 154 to arrest further downward movement of the jaw support 114, continued downward movement of the ram 100 actuates the toggle links 120 and jaws 122 to effect the seal crimping and notching operation, while at the same time the cutter plate 67 cooperates with the fixed cutter block 68 to shear the upper portion of the strapping and then release the strapped bundle from the strap-ping source.

The general arrangement of parts thus far described is similar to that known and described in the aforementioned patent to Ericsson, No. 3,198,218, slight differences in design and the omission of certain non-essential instrumentalities being made in the present disclosure. Therefore, no claim is made herein to any novelty associated with the sealing mechanism 30 per se, the novelty of the present invention residing rather in the pneumatic control mechanism for automatically initiating actuation of the ram 100, and consequently the sealing mechanism 30, in response to the attainment of the desired predetermined maximum tension in the strapping loop which encircles the article undergoing strapping, all in a manner that will now be fully described and subsequently claimed.

In its broadest aspects, the pneumatic control mechanism of the present invention is, by suitable modification, applicable to pneumatic tools other than those of the type shown and described in the Ericsson et a1. Patent No. 2,198,218. However, its adaptation to a structure of the Ericsson et al. type has been made largely by modifying the porting associated with the tensioning and sealing valves and by providing a pneumatic actuator for the sealing control valve which takes the place of the former manual actuator. This pneumatic actuator is made ffective under the control of a pressure relief poppet valve which, for convenience, is embodied in a small casing adjunct that is bolted to the large main tool casting. The pressure relief poppet valve is operatively connected to the air supply line leading to the tensioning motor and is actuated by back-up pressure that takes place in the line at the time the motor approaches or attains a complete stall. When the predetermined pressure is thus attained in the line, the pressure relief poppet valve actuates a second valve (also embodied in the casing adjunct) which conducts air at full line pressure to the pneumatic actuator, thereby causing actuation of the sealing mechanism. By following substantially the same procedure, the present invention is applicable to practically any pneumatic strapping tool which relies upon motor stall or slow-down for termination of the tensioning operation and which employs a pneumatic sealing cylinder for effecting the seal crimping operation.

Briefly, the operation of the strapping tool 10 is effected under the control of the previously mentioned tensioning and sealing valve assemblies TV and SV respectively (FIG. 2), the former valve assembly being manually operated at the commencement of the tool cycle and serving, when thus actuated, to supply air to the tensioning motor and also to release the latch arm 58 so that the spring-biased motor may move to its raised position and thus lower the feed wheel 54 (now rotating) into driving engagement with the strapping. The sealing valve assembly which, in the Ericsson structure, formerly was also manually actuated is, according to the present invention, automatically operable and becomes actuated to perform the seal applying and crimping operation at such time as the desired degree of tension is attained in the strapping and as evidenced by the building up of back pressure (stall pressure) in the air line leading to the tensioning motor. As will be described in greater detail presently this rising pressure is sensed and utilized to trip a poppet valve which, when thus opened, actuates the sealing valve which, in turn, then initiates the sealing operation in the usual manner by supplying air to the main cylinder section 42 of the housing 40.

The tensioning valve assembly TV in the valve chamber includes a spool-type valve body (FIG. 1) which is vertically slidable in a valve cage 152 and is normally urged by a spring 154 to the raised position in which it is shown in FIG. 2. The valve body 150 is provided with an upwardly projecting depressible finger 156 which extends through the closure head 72 and is adapted to be depressed by means of a manually operable fingerpiece 160 (see also FIG. 3) which is pivotally carried by a pin 162 which overlies a portion of the closure head 42. The upper side of the closure head is recessed to provide a sunken shelf portion 164 and a dome-like cap member 166 is secured by screws 168 to the closure head and overlies the shelf portion as best seen in FIG. 3. The finger 156 cooperates with a spring-biased latch memher 170 (FIGS. 3 and 12) which is pivoted at 172 to the shelf portion 164 and has an arm 174 adapted to move over a shoulder 176 provided on the finger 156 and latch the valve body 150 in its depressed position for a purpose that will be made clear presently. The latch member 170 is provided with an upstanding cam wing 184 by means of which the latch member may be automatically released from its latching position in a manner that will be described subsequently. A manual release finger 186 also is provided on the latch member 170. The valve body 150 is provided with a downwardly projecting stem 180 (FIG. 2) on which there is disposed a valve element 182 which normally closes the lower end of the valve cage 152. However, upon depression of the valve body 150 under the control of the fingerpiece 160, the valve element moves downwardly away from its seating engagement on the lower end of the cage.

The sealing valve assembly SV includes a spool type valve body 200 having a pair of spaced valve elements 201 thereon; the valve body being vertically slidable in a valve cage 202 and being norm-ally urged by a spring 204 to the raised position in which it is shown in FIG. 2. The valve body 200 is provided with a depressible finger 206 which projects upwardly through the closure head 42 and has its upper end exposed within the confines of the cap member 166 for actuation by a plunger 208 which is reciprocable in a small cylinder 209 formed in the cap member and which functions as a sealing control cylinder as will be made clear subsequently.

As best seen in FIGS. 2, 8 and 12, means are provided for latching the valve body 200 in its lowered position after initial lowering thereof by the plunger 208. Accordingly, a spring biased latch shaft 210 has a half-moon extension 219 thereon designed for latching engagement with a shoulder 216 provided on the lower end of the valve body 200. The latch shaft 210 lies substantially in the plane of the bottom wall 78 of the cylinder casing 70 as shown in FIG. 9 and a second half-moon extension 218 on the shaft projects into the sealing cylinder 74 and is designed for engagement by the underneath side of the piston 106 at such time as the latter reaches the bottom of its stroke. Engagement of the half-moon extension 218 by the piston 106 serves to rock the shaft 210 through a small angle and thus release the latched valve body 200 and allow the same to return to its normal raised position.

Referring now to FIGS. 4, 5, 6 and 12, an adjustable pressure relief poppet valve PRV which is responsive to the pressure of air supplied to the tensioning motor M operates, when a predetermined degree of pressure is attained in the supply line leading to the motor, to trip a trip release valve TRV, the function of which is to release air from the motor supply line directly to the sealing control cylinder 209 for actuation of the sealing valve SV and consequent actuation of the piston 206 in the sealing cylinder 74 for seal-applying and crimping purposes. The pressure relief valve PRV is a diaphragm type valve and is disposed within the cap member 166. The diaphragm 220 associated therewith is confined in a cavity 221 which is provided in an air supply head 222 (FIGS. 4 and suitably secured to the cap member 166, the edges of the diaphragm being clamped between the cap member and head. A poppet spool 224 slidable in a bore 226 is provided with an enlarged head 228 which bears against the diaphragm 220 and forces the latter against a sealing annulus 228 which surrounds an inlet port 230 to which there is connected an inlet fitting 232 carried at one end of a flexible air conduit 19 (FIGS. 2, 4 and 12). The other end of the air conduit 19 is connected to one leg of a T-fitting 235 leading to the inlet port of the tensioning motor M. The poppet spool 224 is yieldingly urged against the diaphragm 220 by means of a spring 236, while an adjustment screw 238 is provided for regulation of the pressure exerted by the spring 236. The poppet spool 224 is formed with an annular groove 242 therein (FIGS. 4, 5, 10 and 11) into which there projects the outer end of a trip finger 244 formed on a two-position valve element 246 associated with the trip release valve TRV. The valve element is generally of spherical design and is movably disposed within a surrounding valve housing 250. The latter housing is adapted to seat within a recess 251 formed in the underneath side of the cap member 166. A relief area 252 formed in the valve element 246 is effective in the position in which it is shown in FIG. 10 to close a port 254 provided in the housing 250. In the other position of the valve element illustrated in FIG. 11, the relief area is effective to establish communication between the port 254 and an annulus 256 provided in the housing 250-.

The above described trip release valve TRV per se is of conventional design and no claim is made to any novelty associated with the same. A valve of this general type is manufactured and sold by the Compressed Air Service Company of Dayton, Ohio under the trade name of Tiny Tim." For a more detailed disclosure of the valve TRV, reference may be had to US. Patent No. 3,036,589, dated May 29, 1962 and entitled Air Valve.

The pressure relief valve PRV aflfords a quick and sudden activation of the trip release valve TRV at such time as the pressure developed at the inlet port 230 (FIG. 5) rises above a predetermined maximum. Prior to the attainment of such a predetermined pressure, the force of the spring 236 maintains the diaphragm 220 seated against the annulus 228 and overbal-ances the total air pressure acting on the circular area of the diaphragm 220 and which is bounded by the annulus. The diaphragm therefore remains insealing engagement with the annulus 228 until such time as the predetermined pressure of air at the inlet port is such as to overbalance the pressure exerted by the spring 236. At such time, the diaphragm is forced away from the sealing annulus 228 or cracks open, so to speak, whereupon the pressure of air at the inlet port may then act upon substantially the entire diaphragm area within the chamber 221, thereby rapidly forcing the poppet spool 224 to the right as viewed in FIG. 5 so that the trip finger 244 swings in a clockwise direction from the position in which it is shown in FIG. 10 to the position shown in FIG. 11, thereby establishing communication between the port 254 and annulus 256.

As shown in FIGS. 7 and 12, air is supplied to the tool 10 through a flexible conduit 260 which leads directly to the valve chamber 75 of the tensioning valve TV through a quick-release fitting 262 (see also FIG. 2). The valve chamber 75 communicates through an internal passage 21 with the valve chamber 76 of the sealing valve SV and thus the valve chambers of both valves TV and SV are at all times supplied with air at full line pressure. It is to be noted at this point that the casing 70, closure member 72 and cap member 166 are provided with a multiplicity of additional internal passages which extend between the various pneumatically operable instrmentalities associated with the tool and which appear variously in FIGS. 2, 4, 6, 7, 8 and 9. In the drawings, sectional views have been made along judiciously selected planes in an effort to disclose all such passages. Since certain of these passages are disposed entirely in one member, while other passages extend through or into two adjacent members, and still other passages project through or into all three members, it is deemed adequate for descriptive purposes herein to rely upon the disclosure of FIG. 12, wherein all passages are schematically illustrated and designated by individual reference numerals. Corresponding reference numerals have been applied to the detailed disclosure of parts in FIGS. 2, 4, 6, 7, 8 and 9, the individual internal passageways being composite ones, not necessarily existing in one casing part, or being wholly illustrated in any single view of the drawings. External air lines have been similarly treated.

In the operation of the strapping tool 10', the tool may be suspended from an overhead hoist or adjust-able tool balancing support by means of the suspension handle 14, the latter being designed to maintain the tool at various universal inclinations other than the vertical position in which it is illustrated in FIG. 1. An appreciable amount of the total weight of the tool is thus supported so that there will be no danger of damaging the article undergoing strapping. The tool isthen manipulated to bring the foot portion 12 to a position wherein its underneath surface bears against the article to be strapped. Prior to manipulation of the tool, the fiat metal strapping is pulled forwardly from a supply roll or other suitable source of strapping and looped around a package or bundle with its free end underlying the feed end thereof as is customary with strapping machines of the type under consideration. The. free end of the strapping is then passed .bver the wings 20 and 22 and under the gripper element 66 which is raised by depressing the lever 65. Upon release of: the lever, the gripper element moves downwardly and clamps the free end of the strapping against longitudinal movement. The *feed portion of the strapping is caused to pass between the feed wheel 56 and the back-up pad 60.

After loading the tool in the rnannerindicated: above, the start lever of fingerpiece 160 is depressed and thereafter the operation of the tool'is entirely automatic and a complete cycle of strapping operation takes place, terminating in application of a seal S to the overlapped portions of the tensioned straping and severing of the strap loop from the bundle.

It will be understood that prior to the application of the strapping tool to the article or bundle, the flexible conduit 260 will have been appliedio the quick release fitting 262 so that the tool will be supplied with air, the air entering the valve chamber 75 and passing around and through the valve cage 152 and through the internal passage 21 (FIGS. 2 and 12) from whence it enters the valve chamber 76 and passes through the valve cage:202 .and is conducted through a passage 23 to the bottom of the sealing cylinder 74, thus maintaining the piston 216 in its raised position. With the piston 216 thus raised,

'the seal-applying and crimping jaws 122 assume the position in which :they areashown in FIG. 9 with the jaws in their fully open seal-supporting position.

Depression of the start lever 160, and consequent shifting or" the valve body.150 (FIG. 2) carries the valve element 182 away from the lower end of the valve cage 152 so that air passes from the valve chamber 75 to the tensioning motor M through a flexible conduit 25 (FIGS. 2, 4 and 12) which is connected at one end to a leg of the T-fitting 235 and at the other end to a nipple fitting 266 leading from th; bottom; of the cylinder 75 (FIG. 2) Such energization of the motor M initiates rotation of the feed wheel 56. Simultaneously with passage of air through the conduit.25, air passes through a passage 27 to. the upper end of the positioning cylinder 63, thus driving the plunger 62 downwardly and disengaging the latch arm 58 from the pin 59 and allowing the tensioning motor M to swing in a counterclockwise direction as seen in FIG. 1 to;bring the feed wheel 54 into operative engagement with the overlapping portions ;of the strapping on the back-up pad 56. Since the feed wheel 54 is rotating at this time, tensioning of the strapping will ;com

mence and the strap loop will continue to shrink upon the article or bundle undergoing strapping until such time as the desired and predetermined degree; of tension has been attained. At this time the air-operated tensioning motor. M will stall, as is customary with strapping machines of the character under consideration.

In order todatch the valve body 150 of the tensioning valve TV in its shifted position so as 'to maintain the tensioning motor M actuated during the entire cycle of tOOlzOPfiIfitlOfi, the spring-biased latch member 170 (FIG. 3) swings inwardly against the finger 156 and thus overlies the shoulder 176 so as to prevent the valve body 15,0 from returning to its initial position. The latch member 170 is adapted to remain etfective until the end of the tool cycle when the upstanding cam wing 184 whichis formed on the latch member 170 is engaged by the lower CniOf the plunger 208 associated with the sealing control cylinder 209 as will be described in detail subsequently.

.As the tension in the strapping increases, the load upon the motor will, of course, increase proportionately and this load resistance is reflected by the back-up pressure in the line 25 leading to the motor M. This back-up pressure is also reflected in. the flexible conduit 19 which extends from the tensioning motor M to the pressure release poppet valve PRV. When a predetermined backup press ure incident to approaching motor stall, or .com-

plete motor stall, has been attained in the line 19, as

determined by the setting of the adjusting screw 238, the spring-pressed poppet spool 224 is forced away from the inlet port 230 due to the building up of pressure on the pressure side of the diaphragm and the shifting movement of the spool val-ve trips the trip release valve TRV. At this point, air which formerly was prevented from passing through this valve through the passages .27, 33, may now flow through the reliefi area 24% (FIGS. 5 and 11 of the two-position ball valve element 246 and enter a passage 35 leading to the upper end of the sealing control cylinder Upon pressurizing of the upper end ot the cylinder 21 as previously described, thezzplunger 208 moves downwardly and depresses the finger 206, thus actuating the sealing valve SV and causing it to assume the position in which it is shown in FIG. 8,.so that air will flow through the cylinder 76 and through a passage 37 leading to the top of the sealing .cylinder::74. Such admission of air to the cylinder 74 causes the piston 216 to deliver its poyver stroke, thus actuating the sealing jaws 122 in the manner previously described and causing a seal S to be applied .to the overlapping portions of the strapping and crimped therearound. I 5

It is to be noted at this point that upon initial depression of the valve body 200 (FIGS. 2 and 8) the half moon extension 214 on the latch shaft 212 will engage the shoulder 216 on the valve body and maintain the latter in its depressed position until the piston 106 in the cylinder 74 completes its power stroke. At this time the underneath side of the piston will engage the halfmoon extension 218 on the latch shaft 212 and rotate the latter shaft throughout a small angle in such a" manner as to withdraw the half-moon extension 214 from the shoulder 215 of the valve body 200 so as to allow the spring 204 to restore the valve body 200 to its initial raised position, thereby providing a path for evacuation ofair from the top of the sealing cylinder 74 and a path for introduction of return air into the lower end of the sealing cylinder. I

'Introduction of such return air into the cylinder is effected by passage of the air through the valve chamber 76 from'the tensioning valve which becomes restored to its initial position at such time as the plunger 210 associated'with the sealing control cylinder 2 -09 completes its downward stroke. At such time the lower end of the plunger 208 engages the cam wing 184 and displaces the latch member from its engagement with the shoulder 176 on the valve body150, thus allowing the latter to move' upwardly under the influence of the spring 154. With the tensioning valve TV thus restored to its original'position, air from the supply line- 260 is again effective through both the tensibning valve TV and the sealing valve SV, as well as through the passageway 23 to raise the piston 216 of the sealing cylinder 74 as previously described. Such raising of the piston 216 serves to restore the crimping jaws 122 to their open position for'reception of a fresh seal S therebetween for use in the next succeeding tool cycle. Restoration of the tensioning valve TV to its initial position also discontinues the supply of air to the tensioning motor M so that the back-up pressure of air'in the passageway 19 collapses, thus'allowing the spring 236 to restore the poppet spool 224 and diaphragm 238 to their normal positions. Such reverse shifting of the poppet spool 224 operates through the trip finger 244 to 'restore the trip release valve TRV to its normal position,

13 thereby bleeding the upper end of the sealing control cylinder 209 to the atmosphere to allow restoration of the sealing valve SV to its normal position as previously described.

The collapse of backup pressure in the lines leading to the tensioning motor M also relieves air pressure in the upper end of the positioning cylinder 63 so that the spring 64 may restore the plunger 60 and thus release the latch 58 from the pin 59 so that the motor M may be lowered to raise the feed wheel from the back-up pad 56. A bleeder passage 223 (FIGS. 4 and 12) allows the spring 236 to restore the diaphragm 220 of the pressure relief valve PRV to its normal position. All the various tool parts being thus restored to their original positions, the tool is then ready for the next succeeding strapping cycle.

From the above description it is believed that the nature and operation of the present sealing control system will be readily understood without further description. However, certain hitherto unmentioned refinements have been incorporated in the disclosure of FIG. 12 and operate to enhance the efliciency of the tool. For example, a small internal restriction orifice 270 is interposed in the line 19 to prevent the starting up surge pressure in the motor feed line from tripping the valve PRV prematurely. Additionally, a surge chamber shown in dotted lines at 272 may be interposed in the line 19 for the same purpose. In the illustrated embodiment of the invention which, as previously stated, utilizes the basic framework of the Ericksson Patent No. 3,198,218 for its environment, the volumetric capacity of the flexible line 19 is adequate for surge pressure assimilation and an additional surge chamber is not necessary. The dotted line rectangle 272 may therefore represent the total volumetric capacitance of the line 19 in the absence of an actual physical surge chamber. It is also to be noted that the point at which the line 19 communicates with the passageway 25 leading to the tensioning motor M is close to the air inlet port of the motor. Thus, back-up pressure in the line at such time as the motor approaches its condition of stall is translated to the pressure relief valve with no lessening eddy current or surge losses such as would take place if the back-up pressure were to be tapped at a point remote from the tensioning motor.

The invention is not to be limited to the exact arrangement of parts shown in the accompanying drawings or described in this specification as various changes in the details of construction may be resorted to without departing from the spirit of the invention. For example, it is within the purview of the invention to effect actuation of the sealing control cylinder assembly 208, 209 directly from the pressure relief valve PRV without utilizing a relay valve such as the trip release valve TRV. Additionally, the invention is not necessarily limited to use in connection with sealing mechanism of the type where a metallic seal is crimped about the overlapping portions of the strapping. Other forms of sealing mechanism wherein heat sealing operations are performed on the overlapping portions of the strapping may be set into motion by the sealing control cylinder if desired. Therefore, only insofar as the invention has particularly been pointed out in the accompanying claims is the same to be limited.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. In a pneumatically operable strapping tool for tensioning a loop of strapping having overlapping end portions about an article, an air-operated motor effective when energized to progressively apply tension to the loop and to maintain such tension, an air supply line leading to the motor, sealing instrumentalities effective when actuated to seal said overlapping end portions to each other, and pneumatic means responsive to the incidence of backup air pressure in said supply line for actuating said sealing instrumentalities when said back-up pressure reaches a predetermined maximum.

3. In a pneumatically operable strapping tool, the combination set forth in claim 1, wherein said pneumatic means comprises a cylinder operative when supplied with air to actuate said sealing instrumentalities, a trip release valve effective when actuated to supply air of said cylinder, and a pressure-responsive relief valve connected to said air supply line and effective when the back-up pressure in said line reaches said predetermined maximum to actuate said trip release valve.

4. In a pneumatically operable strapping tool, the combination set forth in claim 1, wherein said pneumatic means comprises a sealing cylinder effective when supplied with air to actuate said sealing instrumentalities, a sealing valve effective when actuated to supply air to said sealing cylinder, a sealing control cylinder operative when supplied with air to actuate said sealing valve, a trip release valve effective when actuated to supply air to said sealing control cylinder, and a pressure-responsive relief valve connected to said air supply line and effective when back-up pressure in said line reaches said predetermined maximum to actuate said trip release valve.

5. In a pneumatically operable strapping tool, the combination set forth in claim 4 and including, additionally, a restriction interposed in said air supply line leading to the motor, said restriction being disposed between the motor and the point of connection of the pressure-responsive relief valve to said air supply line and serving to prevent back-up surge pressure inicident to motor starting operations from prematurely reaching said predetermined maximum.

6. In a pneumatically operable strapping tool, the combination set forth in claim 4, wherein said pressure responsive relief valve embodies an air chamber having a port in communication with said air supply line, a flexible diaphragm extending across said chamber and having an effective area greater than that of the port, a plunger yieldingly bearing against said diaphragm and normally urging the same into sealing relationship with respect to the port, and wherein said trip release valve is provided with a movable actuating finger operatively connected to the plunger, said finger being effective upon flexing of the diaphragm and consequent shifting movement of the plunger to actuate said trip release valve.

7. In a pneumatically operable strapping tool, the combination set forth in claim 6, wherein the connection between said plunger and actuating finger comprises a recess in said plunger into which the actuating finger projects.

8. In a pneumatically operable strapping tool for tensioning a loop of strapping about an article, and for thereafter applying and crimping a seal about the overlapping portions of the tensioned loop, a feed wheel engageable with the strapping for tensioning said loop, an air-operated motor connected to the feed wheel in driving relationship and having an air inlet port, sealing instrumentalities effective when actuated to seal said overlapping portions of the strapping to each other, a tensioning valve effective when actuated to supply air to the air inlet port of the motor to rotate the feed wheel and progressively apply tension to the strapping loop and to maintain such tension, a sealing valve effective when actuated to actuate said sealing instrumentalities, an operating lever for actuating the tensioning valve, a sealing control cylinder effective when supplied with air to actuate said sealing valve, and pneumatically operable valve means responsive to the incidence of back-up air pressure at said inlet port for supplying air to said sealing control cylinder.

9. In a pneumatically operable strapping tool, the combination set forth in claim 8, wherein said pneumatically operable means comprises a sealing control cylinder operative when supplied with air to actuate said sealing instrumentalities, a trip release valve effective when actuated to supply air to said sealing control cylinder, and a pressureresponsive relief valve connected to said air inlet port and responsive to back-up air pressure at said port for actuating said trip release valve when such back-up air pressure reaches a predetermined maximum.

10. In a pneumatically operable strapping tool, the combination set forth in claim 8, wherein said pneumatically operable means comprises a sealing cylinder effective when supplied with air to actuate said sealing instrumentalities, a sealing valve effective when actuated to supply air to said sealing cylinder, a sealing control cylinder operative when supplied with air to actuate said sealing valve, a trip release valve effective when actuated to supply air to said sealing control cylinder, and a pressureresponsive relief valve connected to said air port and responsive to back-up air pressure at said port for actuating said trip release valve.

11. In a pneumatically operable strapping tool, the combination set forth in claim 10, wherein said pressure relief valve embodies an air chamber having a port in communication with said air supply port, a flexible dia phragm extending across said chamber and having an effective area greater than that of the port, a plunger yieldingly bearing against the diaphragm and normally urging the same into sealing relationship with respect to the port, and wherein said trip release valve is provided with a movable actuating finger operatively connected to the plunger, said finger being effective upon flexing of the diaphragm and consequent shifting movement of the plunger to actuate said trip release valve.

12. In a pneumatically operable strapping tool, the combination set forth in claim 11, wherein the plunger is yieldingly urged against said diaphragm by means of a compression spring, the combination including, additionally, a regulating screw for adjusting the force exerted by the spring upon the plunger whereby said pressure relief valve may be made responsive to varying back-up pressures at said air inlet port.

13. In a pneumatically operable strapping tool for tensioning a loop of strapping about an article, and for thereafter applying and crimping a seal about the overlapping portions of the tensioned loop, a feed wheel engageable with the strapping for tensioning said loop, an air-operated motor connected to the feed wheel in driving relationship and having an air supply port, sealing instrumentalities effective when actuated to seal said overlapping portions of the strapping to each other, a tensioning valve effective when actuated to supply air to said air supply port to rotate the feed wheel and progressively apply tension to the strapping loop and to maintain such tension, an operating lever for actuating said tensioning valve, a sealing valve effective when actuated to actuate said sealing instrumentalities, a control cylinder and plunger assembly effective when supplied with air to actuate said sealing valve, releasable latch means automatically effective to maintain said tensioning valve actuated after actuation by said lever, pneumatically operable valve means responsive to the incidence of back-up air pressure at said air supply port for supplying air to said control cylinder and plunger assembly, and means on the plunger of said control cylinder and plunger assembly engageable with said latch for releasing the same upon actuation of said sealing valve.

14. In a pneumatically operable strapping tool, the combination set forth in claim 13, wherein said pneumatically operable valve means comprises a trip release valve effective when actuated to supply air to said cylinder and plunger assembly, and a pressure-responsive relief valve connected to said air inlet port and responsive to back-up pressure at said port for actuating said trip relief valve when said back-up pressure reaches a predetermined maximum.

15. In a pneumatically operable strapping tool, the combination set forth in claim 14, wherein said pressure relief valve embodies an air chamber having an inlet port in communication with said air supply port, a flexible diaphragm extending across said chamber and having an effective area greater than that of the inlet port, a plunger yieldingly bearing against the diaphragm and normally urging the same into sealing relationship with respect to the port, and wherein said trip release valve is provided with a movable actuating finger operatively connected to the plunger and effective upon flexing of the diaphragm and consequent shifting movement of the plunger to actuate said trip release valve.

16. In a pneumatically operable strapping tool, the combination set forth in claim 15, wherein the connection between said plunger and actuating finger comprises a recess in the plunger into which the actuating finger projects.

17. In a penumatically operable strapping tool, the combination set forth in claim 15, wherein the plunger is yieldingly urged against said diaphragm by means of a compression spring, the combination including, additionally, a regulating screw for adjusting the force exerted by the spring upon the plunger whereby said pressure relief valve may be made responsive to varying back-up pressures at said air inlet port.

18. In a pneumatically operable strapping tool, the combination set forth in claim 15 including, addiitonally, a restriction interposed between the inlet port of said pressure relief valve and said air supply port and serving to prevent back-up surge pressure at said latter port incident to motor starting operations from prematurely reaching said predetermined maximum.

References Cited UNITED STATES PATENTS 3,198,218 8/1965 Ericsson et al. 93.4 3,232,217 2/1966 Harmon et al. l4093.4 3,329,178 7/1967 Plunkett 14093.4

LOWELL A. LARSON, Primary Examiner

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