US2097444A

US2097444A - Strap stretching device

Info

Publication number: US2097444A
Application number: US708986A
Authority: US
Inventors: William C Childress
Original assignee: Acme Steel Co
Current assignee: Acme Steel Co
Priority date: 1932-02-10
Filing date: 1934-01-30
Publication date: 1937-11-02
Anticipated expiration: 1954-11-02

Description

Nov. 2, 1937. w- C cHlLDREss 2,097,444

STRAP STRETCHING DEVICE Original Filed Feb. l0, 1932 5 Sheets-Sheet 1 Nov. 2, 1937. l w. c. CHILDREss 2,097,444

STRAP STRETGHING DEVICE Original Filed Feb. 10, 1932 'o' Sheets-Sheet 2 Nov. 2, 1937. w, c, cHlLDREss 2,097,444

STRAP STRETCHING DEVICE;

Original Filed Feb. 10, 1932 5 Sheets-Sheet 3 Patented Nov. 2, 1937 2,091,444 g .STRAP s'rnE'ronrNo. DEVICE William C. Childress, Oak Park, Ill., assigner to Acme Steel Company, Chicago, Ill., a corporation of Illinois Original application February 10. 1932, Serial No. 592,050. Divided and this application January 30, 1934, Serial No. 708,986. Renewed February 11 Claims. (Cl. 140-93) This invention relates to improvements in strap stretching and sealing devices and the present application is a division of my co-pending application Serial No. 592,050, filed February 10, 1932,

5 in which there is disclosed a strap stretching and sealing device adapted to draw a exible metal strap taut around a box or package, cut oi the strap from the source of supply and then form an interlocking joint between the overlapping l strap ends by cutting and shearing or otherwise deforming these portions of the strap. The present invention relatesA particularly to the means which are embodied in said device for drawing the strap taut around the box or package preliminary to the cutting of the strap and the formation of the joint and the principal object of the present invention is to provide improved mechanism for performing this operation of stretching or drawing taut a exible strap or binder. A further object of the invention is to provide an improved strap stretching device comprising a base having mounted thereon a pair of gripping devices adapted to grip opposite end portions of the strap in combination with a slidably mounted bar carrying one of the gripping devices and means for effecting relative movement of the bar and the base for drawing the strap taut. A further object of the invention is to provide a strap stretching device comprising means Afor engaging opposite end portions of a strap and effecting relative movement of these portions for drawing the strap taut in combination with means for automatically terminating the tightening opera'tion when a predetermined tension is obtained in the strap. Still another o bject of the invention is to provide a strap stretching device comprising a base having mounted thereon a pair ofA relatively movable gripping devices adapted to engage opposite end portions of the strap in combination with mechanism comprising a lever movable transversely to the direction in which the strap extends for effecting movement of said gripping devices. Still another object of the invention is to provide a strapstretching device iii ed to function after a predetermined degreeof tension has been brought about in the strap. Other objects relate to various features of construction and arrangement which will appear 50 more fully hereinafter.

The nature of the invention will be understood from the following specification taken with the accompanying drawings in which one embodiment is illustrated.

In the drawings,

comprising a yielding connection which is adapt- Figure 1 shows a side elevation of a box or package with the improved strap stretching and sealing device of the present invention applied thereto for the purposetof drawing a iiexible metal strap taut around the package;

Fig. 2 shows a top plan view of the overlapping ends of a metal strap having formed therein the improved interlocking joint which is formed by the operation of the device of the present inven- Fig. 3 shows a side elevation of the joint illustrated in Fig. 2; I

Fig. 4 shows a bottom plan view of the joint illustrated in Fig. 2;

Fig. 5 shows an enlarged transverse section taken on the line 5-5 of Fig. 2;

Fig. 6 shows an enlarged transverse section taken on the line 6--6 of Fig. 2;

Fig. 7 shows an enlarged top plan view Aof the strap stretching and sealing device of the present invention with parts thereof broken away;

Fig. 8 is a detail sectional view taken on the line 8 8 of Fig'. 7;

Fig. 9 shows an enlarged front elevation of the strap stretching and sealing device illustrated in Figs. 1 and 7;

Fig. 10 is a detail vertical section taken on the line I0-I0 of Fig. 7;

Fig. 11 is a detail vertical section taken on the line II-II of Fig. 9;

Fig. 12 is a detail vertical section taken on the line IZ-IZ of Fig. 9;

Fig. 13 is a detail section taken on the line I3-I3 of Fig. 15;

Fig. 14 is an enlarged vertical section taken on the line lli-I4 of Fig. 7, showing the position of the cutting blade or die and of the strap crimping jaws preliminary to their engagement with the Fig. 15 is a partial vertical section similar to that of Fig. 14, showing the4 relative positions of the parts after the strap has been cut off from the source of supply by the cutting die and after the crimping jaws have been brought into engagement with the straps;

y Fig. 16 is an enlarged vertical sectional view showing the positions of the jaws after they have been brought into nal engagement with the overlapping strap ends;

Fig. 17 is an enlarged detail horizontal section taken on the line i'I-i1 of Fig. 16;

Fig. 18 is an enlarged vertical section taken on the line Iii-,I8 of Fig. 17; and

Fig. 19 is a perspective view of one of the intermediate plates of the crimping jaws.

It is common practice to employ at' flexible steel straps'or other binders for reenforcing boxes or packages and also for binding together groups of packages to form load` units and the present invention is directed to improved means for drawing taut the strap or binder after it has been passed around the package or group of packages, although it is illustrated in the accompanying drawings in association with the means for cutting ou the strap from the source of supply and the means for subsequently crimping and also, preferably, shearing the overlapping strap ends to form an interlocking joint, which features are described andclaimed in the copending application above referred to. As illus-l trated in Fig. 1. the strap stretching and sealing device I is shown applied to the upper surface of a box or crate I I and the walls of this box are reenforced by two flat flexible steel straps or binders I2 which are passed around the box. The strap stretching and sealing device I0 is shown in position to engage one of these straps.

The device I0 comprises a base plate I5 which is adapted to rest upon the surface of the box or package and which carries the operating part by which the strap is rst stretched, then cut off from the source of supply and i'lnally crimped or otherwise deformed to form an interlocking joint between the ends of the strap. The base plate I5 is provided with a forwardly extending ange I6, spaced slightly above the surface of the box, which is adapted to receive on its upper side the free end I2a of the strap I2. Adjacent to the flange I6, the base plate carries an upwardly extending block or lug I1 which serves as a support for a gripping dog or detent I8 having a lower serrated or roughened part I8a which is adapted to coact with the upper side of the strap I2'to hold the strap firmly in engagement with the flange I6. The gripping dog I8 is rotatably mounted upon a pin or shaft 20 which is fixed in the block I1 by means of a set screw 2I. 'I'he pin or shaft 20 is provided with a relatively xed handle 22 which serves as a handle for the detent I8 so that the latter may be moved out of engagement with the upper side of the strap against the compression of .a coil spring 23 which is mounted in a recess in the detent and which engages at its upper end a plug 24 mounted in an aperture in the upper flange |13 of the lug or block I1. This spring thus normally serves to maintain the dependent engagement with the strap and the serrated portion I8a of the detent is displaced laterally from the pivotal axis of the detent, as shown in Fig. 9, so that a pull upon the strap I2 toward the left as viewed in that figure tends to increase the grip of the gripping dog and iiange upon the strap, while a movement of the strap in the other direction tends to effect an automatic release of thestrap from the gripping dog. After having the free end I2 of the strap passed into gripping engagement with the dog I8, the strap is passed around the box or package II and the supply portion I2b of the strap is then carried over the free end I2 and passed into engagement with a slotV I8b which is formed in the side of the gripping dog I8 as shown particularly in Figs. 9 and 11. For the purpose of maintaining the supplyend of the strapin engagement with this slot, the recess in which the spring 23 is mounted is provided'at its lower end with a movable ball 25 adapted to project through a tapered aperture in the lower end of the recess so that it is held by the spring 23 in engagement with the lower wall of the slot Ill to hold the strap in the slot while permitting the ready insertion or withdrawal of the strap when desired.

For the purpose of stretching the strap I2 around the package, the supply portion I2b thereof is engaged by another gripping dog 26 which is carried by a block 21 mounted upon the outerend of a slidably mounted bar 28 carried by a plate I 5. This bar is adapted to move parallel to the strap which is held by the gripping dog 2B against a flange 21* which projects forwardly from the block21. The block 21 is secured to the bar 28 by a stud 29 and it carries a fixed pin or axle 30 upon which the gripping dog 28 is pivotally mounted. 'I'he upper edge of the gripping dog is curved to coact with the curved flange 2lb of the block. 'I'his flange is concentric with the pin 38 so that the gripping dog is supported independently of the pin. The other end of the gripping dog is provided with a serrated surface 26 which coacts with the upper side of the strap I2 and forces it against the flange 21l under the inuence of a coil spring 3| which engages a socket in the gripping dog and coacts with a flange 21c carried by the block 21. The gripping dog 26 is inclined toward the left as viewed in Fig. 9 so that a pull upon the strap I2b toward the right will tend to increase the grip of the dog upon the strap while movement of the strap in the other direction will tend to effect an automatic release of the strap from the gripping dog. With the block 21 and the gripping dog 26 mounted as above described it will be apparent that movement of these members with the bar 28 toward the left, as view in Fig. 9, will draw the strap I2 taut around the box or package II. The base plate I5 is provided on its upper side with a groove 32, of rectangular 'cross section, in which the bar 28 is adapted to slide and the base plate is also provided with a recess 33 which is adapted to be engaged by the underside of the block 21, as shown in Fig. 12, during the sliding movement of the bar 28. The bar is maintained in the groove 32 by means of the retaining members 34 which are secured to the base plate by screws 35, as shown in Fig. 7. 'I'he sliding movement of the bar 28 is eiected by certain operating mechanism comprising a link 31 which extends between two ears 38 carried by one of the members 34, as shown in Fig. 10, and is secured thereto by means of a pivot pin or rivet 39. 'I'his link 31 has its other end pivotally -connected at 48 with a shifting link 4I which has its forward end inserted between the bar 28 and the reversely bent portion 28 thereof, as shown in Fig. 10, being pivotally connected thereto by means of the pin 42. The pin 40 carried by the link 31 thus provides a movable fulcrum about which the lever 4I is adapted to pivot in effecting a sliding movement of the bar 28 and this pivotal movement of the lever 4I is effected through the connections which are shown particularly in Figs. 14 and 15. The rear end of the lever 4I carries an upwardly extending pin 43 provided with a spherical head 43a. This pin is adapted to be inserted through a key-hole slot 44 formed in the wall of a hollow link 45 and the head 43a is engaged within the hollow link by a coil spring 46, the compression of which may be adjusted by a plug 41 which threadedly engages the end of the link to coact with the end of the spring. The other end of the hollow link 45 is provided with another key-hole slot 48 to receive the head 49a and the neck of a pin 49 which is secured to the short arm 50! of the strap stretching lever 50, the long arm of which extends upwardly as shown in Fig. 9 with a handle 5I)b at the upper end thereof for engagement by the hand of the operator. The lever 5I! is fixed upon a shaft 5| which is journaled in bushings 52 secured by set screws 52a within the spaced bearing

members

53 and 54 mounted on or formed integrally with the baseplate I5, as shown in Fig. 7. When the lever 50 is moved rearwardly. or toward the left as view in Fig. 14, the hollow link 45 is carried forwardly and this causes the spring 46 to move the pin 43 and thus actuate the lever 4| in a forward direction, causing the latter lever to rock about the pin 40 so that it moves bodily from the position shown by full lines in Fig. '1 to the position shown by dotted lines in that figure. This results in shifting the bar 28 toward the left as viewed in Figs. 7 and 9 so that the strap 2 is thereby drawn taut. 'When a predetermined degree of tautness is obtained in the strap I2, the continued movement of the lever 50 will merely serve to compress the spring 46 within the hollow link 45. During this movement of the operating lever 4I, the rear end of that lever is maintained in position adjacent to the -base I5 by a plate 55 which is secured by screws 56 to a ledge 51 formed on the base I5, with a part of the plate overlying a portion of the lever 4|, as shown particularly in Figs. '1 and 8. An important advantage of this construction is that the operation of the lever 50 produces arapid relative movement of the blocks I1 and 21 during the early part'of the stretching operation when the strap is comparatively slack, while the rapidity of motion decreases and the force exerted upon the strap increases as the final stages of the stretching operation are approached. This permits the tool to be used in stretching a strap in a single operation as compared with the use of several tools or several operations, which has been the practice heretofore.

After the strap has been drawn taut in the manner described above, the end portion |21 thereof is cut off from the source of supply and the overlapping ends of the strap are then deformed to produce an interlocking joint through the operation of certain mechanism carried by a movable head 59 comprising a pair of flat plates 60, spaced apart in vertical planes, and having their rear ends pivotally mounted upon the shaft 5I as shown in Fig. '1. One plate 60 is maintained in frictional engagement with the side of the bearing hub 53 by meansA of a coil spring 6| which is mounted on the shaft 5| with one end bearing against the last mentioned plate 60 and with the other end bearing against a collar 62 which is secured against endwise movement on the shaft 5| by means of a transverse pin 63. The other plate 60 is maintained against the bearing hub 54 by means of a plate 64 which is secured to the base plate I5 by means of a screw 65. These plates 60 have mounted between the enlarged forward ends thereof a pair of crimping jaws 66 which are mounted upona common pivot 61 extending between the plates and which have their arms 66n extending upwardly with their upper extremities pivotally connected by when the head 59 is in its normal upper position, as shown in Figs. 9 and14 and, when the operator wishes to move the head 59 downwardly that movement is first effected by thrusting on the lever 1|, while maintaining it in its upright position and then, the lever 1I may be turned about the pivot 'I2 for the purpose of actuating the links 69 and thereby moving the jaws 66 toward each other to effect the crimping and shearing of the stra ends as hereinafter more fully described. The extent to which this pivotal movement of the lever 1| may be carried is limited by means of a stop member 13 which threadedly engages the lever 1|, being held in.

lever 1| is in its lowermost position, as shownin Fig. 16, thus preventing further movement of the jaws 66 toward eachother. By adjusting -the position of the stop member 13, the minimum separation of the jaws may be varied as desired. The initial downward movement of the head 59 is utilized to effect the cutting 01T of the strap from the source of supply. The cutting of the strap is effected by a cutting lever 15 which is pivotally mounted on a pin 16 secured in one of the retaining members 34 previously referred to. As shown particularly in Figs. 13 and 14, this lever is provided on one side with a recess 15a in which is removably mounted the cutting blade or die 11, the die being secured to the lever by means of a screw 18. The die is adapted to extend downwardly past the vertical face of a stationary die 19 which is carried by the adjacent member 34 and which extends forwardly therefrom to underlie the upper portion I2b of the strap and to extend over the extremity I2a thereof. The lever 15 has an upwardly extending arm 15b which is pivoted at 80 to a link 8| pivotally mounted at 82 on the adjacent plate 60 of the head. It will be apparent that when the head 59 moves downwardly, the link 8| will serve to actuate the cutting lever 15 so that the movable cutting die 11 will be moved downwardly to engage the supply portion I2b of the strap and cut it off by coaction with the stationary die 19, as shown in Fig. 13.

It is desirable to maintain the manually operated lever 1I in its upright position and to prevent relative movement of the jaws 66 toward each other until aftr the strap has been severed from the source of `supply and the jaws have been brought into a position wherein they may embrace the overlapping strap ends. To obtain this result, the plate 64 heretofore described has an arm 64*3L extending upwardly and forwardly. as shown in Fig. 14, with a curved surface 64b adapted to coact with the end of one of the links 69 along the surface which is concentric with the axis of movement of the head 59. As a result of this arrangement, when the operator pushes downwardly on the lever 1| with this lever extending in an upward inclined position, as shown in Fig. 14, the initial downward movement of the head 59 takes place without any relative movement of the jaws 66 due to the coaction of the link 69 with the curved face 64b of the stationary plate. During this period of movement of the head 59 the cutting lever 15 is actuated to cut off the strap and finally when a point is reached where the jaws 66 are in a position to embrace the overlapping strap ends, as shown in Fig. 15, the end of the link 69 will have passed beyond the curved face 64b of the 75 stationary plate so that the links may then separate from each other toward the position shown in Fig. 16T/The lever 1I is then .permitted to move angularly about its pivot 12 so that the jaws are actuated to crimp the strap and shear its edges as hereinafter described, it being understood that after the strap has been cut oi from the source of supply a portion of the upper end of the strap will overlie the extremity of the lower portion I2 so that when the head 59 is moved-downwardly, 'these overlapping portions are forced together and are then operated upon to deform them into interlocking relation. OW- ing to the frictional engagement of the plate 60 with the bearing hubs-54 and 53, the head 59 is adapted to maintain any position in which it may be put unless it is positively moved therefrom.

Referring now to the means for crimping and shearing the edges of the overlapping portions of the strap to form an interlocking joint, it will be seen upon referring to Figs. 16, 17 and 18 that each jaw comprises a pair of side plates 85, a center plate 86, and two intermediate plates 81, each of the latter plates being interposed between the center plate and one of the side plates. These plates' are secured together by rivets 88 and the intermediate plates have parts 81b extended inwardly and milled off on one side to intert with the corresponding parts of the opposite plates and to receive the pin 61 about which the jaws have pivotal movement.

The intermediate plates 81 have other parts 81a thereof extended upwardly to form the arms 66a of the jaws which are connected to the links 69. 'I'he lower strap engaging portions of the jaws beneath the pivotal axis 61, are provided with parts adapted to receive and operate upon the overlapping ends of the strap I2. For this purpose, the edges of the plates 85 of each jaw are provided with notches 85a of rectangular cross section extending inwardly from `the upright face of the jaw and similar notches 86a of rectangular cross section extend inwardly from the edges of the center plate 86. The notch in each center plate registers with the notches 85a in the plate 85 of the same jaw and the notches in the plates of one jaw are disposed oppositely to the notches in the plates of the other jaw so that they register with each other when the jaws are closed upon each other as shown in Fig. 16. The intermediate plates 81 are provided with notches 81c which are of curved cross section and which register partially with the notches 85a and 86a of the respective jaws. The notches 81C, however, are of larger vertical dimensions and project below the openings of the notches 85a and 86a, as shown in Fig. 18. The side plates 60 of the head 59 are cut away as shown at 6I)a so that when the head 59 is lowered the openings 60aL are adapted to receive the overlapping ends of the strap and to hold these overlapping ends in a position wherein they may be engaged by the notches of the jaws when these jaws are closed upon them by the movement of the lever 1I. A fiange 90 projects forwardly from the base I5 to support the extreme end of the portion I2a of the strap and the side plates 60 of the head are adapted to engage the upper portion of the strap and to bring the two parts of the strap into close overlapping relation with each other with parts of the strap on opposite sides of the head supported from below by the flanges I6 and 90. The base I5 is further provided with a curved recess 9| extending inwardly from the space between the flanges I6 and 90 to accommodate the lower portions of the jaws 66, as shown particularly in Fig. 16. The vertical dimensions of the

recesses

85 and 86a are such that they are closely tted by the overlapping strap ends and the depth of the recesses is such that they are completely occupied 'by the strap ends when the two jaws are closed upon each other, as shown in Fig. 16. The flat surfaces of the walls of these notches hold the strap ends in'a ilat condition'while the portions of the strap between the plates 85 and the center plate 86 are curled or beaded due to the action of the curved notches 81c which are formed in the -plates'81. The side plates 85 and the center plate 86 serve to hold the strap in such a position that the plates 81 will always curl or crimp the edges of the strap in the same direction. The notches 85a and 86a also serve to center the strap ends so that they receive the same amount of curling or beading along each edge thereof. The

plates

85 and 86 also act as shearing dies to cooperate with the plates 81 in shearing the overlapping portions of the strap at the ends of the curled or beaded portions.

The action of these jaws 66 upon the overlapping ends of the strap is illustrated particularly in Figs. 2 to 6, inclusive, where the joint formed by the device is illustrated. As shown in these figures, the joint '95 comprises the two overlapping strap ends I2a and I2b which are deformed so that there is an intermediate at portion a, two end portions 95b and two intermediate pairs of rolls or beads 95C which form indentations in the sides of the strap represented at 95d in Fig. 2. The beads or rolls 95 may be of more or less complete circular cross section depending upon the formation of the recesses or notches 81c in the plates 81 and they have a telescoping engagement with each other so that they effectively prevent separation of the overlapping strap ends in any direction transverse to the length of the strap. These beads or rolls also have a longitudinal curvature, diverging away from each other on opposite sides of the strap ends so that they prevent relative longitudinal movement of the strap ends, but this relative longitudinal movement is further prevented by the shearing of the edges of the strap ends to form inwardly extending cuts 95e at each end of each of the beads. These cuts are formed by the cutting edges 81b of the plates 81 which act as cutting dies so that when they engage the edges of the strap the edges of the strap are sheared at the same time that the portions of the strap between the cuts or shears are turned inwardly to form the beads 95. These cuts 95e provide shoulders which coact with the transversely extending shoulders on the ends of the beads to prevent any possible relative endwise movement of the two overlapping strap ends. As a result of the curling and shearing of the strap ends they are bowed upwardly to a slight extent in the region of the joint, as shown in Fig. 4. In this way an effective joint is obtained without the use of any enclosing sleeve or seal such as has heretofore been employed with many forms of sealing devices. 'I'he form of seal or joint hereinabove described is claimed in my co-pending application Serial No. 592,051, filed February 10, 1932.

In the operation of the device, the base plate I5 is seated upon the surface of the box or package about which the strap I2 is to be secured, as shown in Fig. 1. The free end of the strap is then placed beneath the gripping dog I8 on the 75 lthe box or package, the supply portion I2b thereof is inserted beneath the gripping dog 26 and the ange 21a of the movable block 21, from which point the supply portion of the strap extends above the free end of the strap and through the slot |8h of the gripping dog I8 where it is held in place by the spring-pressed ball 25. The parts are then in readiness for drawing the strap taut, which is effected by moving the lever 50 in a rearward direction, as shown in Fig. 14, thereby causing a forward movement of the hollow link 45 with a resulting forward motion of the rear end oi. the lever 4| to which motion is imparted through the spring 46. As the lever 4| moves forwardly, its forward end swings toward the left. as viewed in Fig. 7, thereby actuating the sliding bar 28 upon which the block 21 is mounted. 'I'he movement oi the block 21 carries with it the gripping dog 26 and flange 211 between which the supply portion of the strap is gripped so that the strap is thereby drawn taut around the package. tautness is attained, the coil spring 46 within the hollow link is further compressed so that further movement of the lever 50 and hollow link 45 will not effect any further tightening of the strap. The movable head 50 is then swung downwardly toward the right, as viewed in Fig. 14, while retaining the` lever 1| in its upright position. The initial motion of the head 59 is adapted to. cut off the strap from the source of supply due to the actuation of the cutting lever 15 which engages the supply portion of the strap seated on the ange 19. The cut-oi end of the strap is then pressed downwardly against the free end which rests upon the anges I6 and 90 and these overlapping ends then enter the notches 60a in the side plates 60 of the head, as the downward motion of the head is continued. 'Ihe lever 1| is then swung forwardly about -its pivot 12 with the result that the jaws- 66 are actuated to form telescoping beads along the edges of the overlapping` portions of the strap at points which are spaced apart, as shown in Fig. 4, while at the same time shearing the lateral edges of the strap ends, as shown at e, to insure further the security of the interlocking joint.

Although one form of the invention has been shown and described by way of illustration, it will be understood that it may be constructed in various other embodiments within the scope of the appended claims.

I claim:

1. The combination in a strap stretching device, of a pair of blocks having relative linear movement, gripping means carried by said blocks for gripping the opposite ends of a strap, and operating means for moving said blocks toward each other to draw said strap taut around a package, said operating means comprising relatively movable parts adapted to yield after a predetermined tension has been set up in said strap.

2.`The combination in a strap stretching device, of a base plate, a pair of blocks carried by said base plate, one of said blocks being mounted for sliding movement with respect to the other block, gripping means carried by said blocks for gripping the opposite ends of a strap, means movable transversely to said strap for actuating said movable block to draw said strap taut around a package, said last named means including rela- When a predetermined degree of.

tively movable parts adapted to yield after a predetermined tension has been set up in said strap.

3. The combination in a strap stretching device, of a base plate, a stationary gripping device and a relatively movable gripping device carried by said base plate for gripping opposite end p0rtions of a strap passed around a package, one of said gripping devices being mounted for sliding movement on said base plate, and operating mechanism carried by said base plate for eiiecting relative movement of said gripping devices, said operating mechanism comprising a yieldable connection to permit extension of said mechanism after a predetermined tension has been created in said'strap.

4. The combination in a strap stretching device, of a base plate, a pair of gripping devices carried by said base plate for gripping opposite end portions of a strap, a bar upon which one of said gripping devices is mounted, said bar being slidably mounted upon said base plate, a link pivoted on said bar, a lever having an intermediate part pivoted on said link and having one end pivoted on said bar, land operating mechanism connected to the other end of said lever for effecting movement of said bar.

5. The combination in a strap stretching device, oi' a base plate, a pair of gripping devices carried by said base plate for gripping opposite end portions of a strap, a bar upon which one of said gripping devices is mounted', said bar being slidably mounted upon said base, a link pivoted on said bar, a lever having an intermediate part pivoted on said link and having one end pivoted on said bar, and operating mechanism connected to the other end of said lever for eecting movement of said bar, said mechanism including a resilient connection adapted to yield when a predetermined tension is obtained in the strap.

6. The combination in a strap stretching device, of a base, a pair of gripping devices carried by said base, a bar slidably mounted on said base and having one of said gripping devices mounted thereon, lever mechanism for effecting movement of said bar, and means for operating said lever mechanism including a spring for permitting extension of said mechanism after a predetermined tension has been created in the strap,

7. The combination in a strap stretching device, of a base, a pair of gripping devices carried by said base, a bar slidably mounted on said base and having one of said gripping devices mounted thereon, lever mechanism for eil'ecting movement of said bar, a hollow link connected to said lever mechanism, means for effecting movement of said hollow link, and a spring mounted in said hollow link and adapted to be compressed when said lever mechanism is actuated.

8. The combination in a strap stretching device, of a base, a pair of gripping devices carried by said base, a bar slidably mounted on said base and having one of said gripping devices mounted thereon, a lever pivoted on said base and movable transversely to the direction of movement of said bar, operating mechanism connected between said lever and said bar for effecting movement of said bar to draw taut a strap passed around a package and held by said gripping devices, and means for causing said operating mechanism to set up a predetermined tension in said strap.

9. The combination in a strap stretching device, of a basea pair of gripping devices carried by said base, a bar slidably mounted on said base and having one of said gripping devices mounted 75 thereon, a lever pivoted on said base and movable around a package and held by said gripping detransversely to the direction of movement of said bar, operating mechanism connected between said lever and said bar for effecting movement of said bar to draw taut a strap passed around a package and held by said gripping devices parallel to the path of movement of said bar, and additional means carried by said base plate for cut- 'ting off said strap when it has been drawn taut.

10. The combination in a strap stretching device, of a base, a pair of gripping devices carried by said base, a bar slidably mounted on said base and having one of said gripping devices mounted thereon, a lever pivoted on said base and movable transversely to the direction of movement of said bar, operating mechanism connected between said lever and said bar for effecting movement of said bar to draw taut a strap passed vices parallel to the path of movement of said bar, and a cutting blade pivoted on said base plate and movable transversely to said strap for cutting said strap off from the source of supply when it has been drawn taut.

11. The combination in a strap stretching device, of a pair of relatively movable gripping devices adapted to\grip opposite end portions of a strap looped around an object to be. strapped, and operating mechanism for effecting a relatively rapid relative movement of said gripping devices in the early stages of the stretching operation and for producing a decreasing rate of relative movement of said devices as the strap approaches its taut condition.

WILLIAM C. CHILDRESS.