US2204572A - Electrically driven stretching tool - Google Patents

Description

June 18, 1940.

w. c. CHILDRESS 2,204,572 ELECTRICALLY DRIVEN STRETCHING TOOL File d Nov. 16, 1936 s Sheets-Sheet 1 June '18, 1940- w. c. CHILDRESS EILEC'IRICALLY DRIVEN STRETCHING TOOL 6 Sheets-Sheet 2 Filed NOV. 16, 1956 6 Sheets-Sheet 3 w. QMCHILDRESS Flled Nov 16, 1936 hn i MEN .QN QN ELacmIcALLY mifi'an s'ranwcnms TOOL June 18, I940.

June 1940- w. c. CHILDRESS I 2,204,572

ELECTRICALLY DRIVEN STRETCHING TOOL Filed Nov. 16, 1936 s Sheets-Sheet 4 June 0- w. c. CHILDRESS 2,204,572

ELECTRICALLY DRIVEN STRETCHING TOOL Filed Not. 16, 1936 6 Sheets-Sheet 6 Patented June 18, 1940 UNITED STATES PATENT OFFICE 2,204,572 ELEOTRICALLY DRIVEN STEETCHING TOOL William C. Childress, Oak Park, Ill., assignor to Acme Steel Company, Chicago, 111., a corporation of Illinois Application November 16, 1936, Serial No. 111,088

6 Claims.

This invention relates to improvements in strap stretching and sealing apparatus and its purpose is to provide impoved means for drawing a metal strap taut around a package or group of packages and then sealing the overlapping ends of the strap. The principal object of the invention is to provide an improved form of apparatus of this type in which the mechanism for drawing the strap taut is actuated by an electric motor or other power driven means. .A further object of the invention is to provide an improved appa ratus of the type referred to comprising power driven strap stretching mechanism which is adapted to be automatically released when a predetermined degree of tension has been created in the strap. A further object of the invention is to provide strap stretching mechanism comprising means for drawing a strap taut to a predetermined degree and adjustable means for varying the degree of tension which is set up in the strap. A further object of the invention is to provide strap stretching and sealing mechanism comprising means for holding or gripping opposite end portions of the strap and drawing the strap taut with its ends overlapping-in combination with means for controlling the grip on the strap and means for applying a seal to the overlapping strap ends after the strap has been drawn taut. Still another object is to provide apparatus of the type referred to comprising improved means for actuating and controlling a gripping device by which one end of the strap is held. Another object is to provide improved means for actuating and reversing the circuit of the motor by which the strapstretching mecahnism is driven. A further object is to provide improved mechanism for actuating and controlling the movements of .the relatively movable jaws of the sealing deviceby which a seal is applied to the overlapping strap ends to form an interlocking joint. Other objects relate to various features of construction and arrangement which will appear more fully hereinafter.

The nature of the invention will be understood accompanying drawings, in which one embodiment is illustrated.

In the drawings,

Fig. 1 shows a top plan view of the improved strap stretching and sealing apparatus, of the present invention;

Fig. 2 shows a side elevation of the apparatus illustrated in Fig, l with the strap sealing device and the strap gripping dog in their elevated positions;

from the following specification taken with the Fig. 5 is a perspective view of the gripping dog illustrated in Figs. 2, 3 and 4;

Fig. 6 is a. perspective view of the eccentric on which the gripping dog is mounted together with i a portion of its operating lever, a part of which is broken away;

Fig. '7 shows a perspective view, partly in sec-1 tion, of the sleeve in which the locking balls are mounted for controlling the movement of the lever and eccentric illustrated in Fig. 6;

Fig. 8 is a perspective view of the lower por- 20 tion of the locking lever which is employed in I conjunction with the parts shown in Figs. 6 and 7 to effect the locking and release of the eccentric on which thegripping dog is mounted;

Fig. 9 shows an enlarged section taken on the 5 line 9-9 of Fig. 1, illustrating in vertical section a portion of thedriving mechanism by which the strap is drawn taut;

Fig. 10 is a somewhat diagrammatic view of the circuit connections of the motor and its control- 30 ling switches by which the strap stretching mechanism is actuated;

Fig. 11 is a perspective View of the clutch disk whichis embodied in the construction shown in Fig. 9 to effect the automatic disengagement of 5 the driving mechanism when a predetermined tension has been set up in the strap;

Fig. 12 is a vertical section taken transversely of the apparatus on the line l2l2 of Fig. 3;

Fig. 13 is an enlarged detail section taken on the line I3--I3 of Fig. 3, showing the locking device by which the movement of the gripping dog is controlled;

Fig. 14. is an enlarged detail section taken on positions of the parts after they have been actuated to cause the locking members to hold the eccentric lever against angular movement;

Fig. 15 is an enlarged detail section similar to that of Fig. 14 showing the relative positions of 50 the parts after they have been actuated to cause the locking members to secure the locking lever against angular movement;

Fig. 16 shows an enlarged horizontal section onthe line l6l6 of Fig. 3 illustrating. the con: to

the line l4l4 of Fig. 4, showing the relative nections of the driving motor with the mechanism lowered to engage a seal on the overlapping strap ends;

' Fig. 19 shows an enlarged detail section on the line iii-l9 of Fig. 18, showing the locking means for controlling the movement of the operating lever by which the sealing head is actuated;

Fig. 20is a sectional view taken on the line 2026 of Fig. 18 showing on an enlarged scale the relative positions of the parts of the locking means after they have been actuated to permit downward angular movement of the operating lever for effecting relative movement of the jaws of the sealing head;

Fig. 21 is a vertical section taken on the line 2l-2| of Fig. 20;

Fig. 22 is a perspective view of the lower hub portion of the operating lever. by which the seal ing head is actuated;

I Fig. 23 is a perspective View of the supporting member on which the sealing head is mounted; and

Fig. 24 is a perspective View of the stationary member on which the movable supporting member'shown in Fig, 25' is mounted.

As shown in the drawings, the invention'com prises a casing 35 adapted to rest upon the surface of a box or package 3% about which a flexible binder 37, shown as a fiat steel strap, is adapted to be drawn tautpreliminary to having its overlapping ends secured together by means of a seal which is deformed along with portions of the strap ends, by a portion of the apparatus in order to form an interlocking joint. The frame 35 is provided at its lower edge with two projecting feet or flanges 38 and 39 upon which the free end 37* of the strap is adapted to rest, as shown in Fig. 2. This free end portion of the strap is adapted to be held in engagement with the foot 38 by means of a gripping dog 40 which is capable of adjustment toward and from the foot for the purpose of gripping and releasing the strap. After being passed around the package 35, the other end portion of the strap 33* is passed into engagement with one of the transverse slots fil of a rotatable drum M by which the strap is adapted to be drawn taut about the package before applying thereto a seal 42 which is preferably constructed as a channel-shaped metal member adapted to embrace the overlapping end portions of the strap adjacent to the foot 39, the end por tion 3'! being projected beyond this foot a sufficient amount to permit the application of the seal at this point. The drum ll is adapted to be rotated through suitable driving mechanism actuated by an electric motorwhich is mounted in an auxiliary casing 35 carried at one side of the casing 35. The casing 35 has a handle 43 which permits it to be carried around conveniently and to be located at any desired point on the surface of thebox or package 36 to permit the application of a strap 37. After the strap has been drawn taut by the winding of the drum M, the seal 42 is applied thereto to form an interlocking joint by means of a sealing head it which. is pivoted on the upper part of the casing adjacent one end of the handle and which is adapted to be moved downwardly,by means of an operating lever 45, to a position where it embraces the seal &2 and the overlapping strap ends.

The gripping dog 46 is provided with a serrated portion til adapted to engage the upper surface of the strap 31 and this dog also has a cylindrical opening li which is rotatably engaged by a cam or eccentric member if having the form shown particularly in Fig. 6. This cam or eccentric member is provided with an eccentrically located opening d'l which is engaged by a pin 38 upon which the eccentric has angular movement. As shown in Fig. 12, the pin it is mounted in a bushing ill located in a hub or bearing member 5b which is mounted in the side of the casing 35. A threaded aperture 5| extends through the bearing member and through the bottom of the casing and is engaged by a. headless screw 52 which passes through an aperture in the bushing i9 and which has its extremity engaging a recess it in the pin, thus holding the pin against longitudinal or rotative movement. At its outer end, the pin 18 has an enlarged cylindrical portion 38 and at its outer end the pin is provided with A washer 53 is inserted between the enlarged portion 48 of the pin and the adjacent faceof the eccentric or cam ll. A coil spring 54 surrounds the portion 48 of the pin with one extremity E l thereof engaging an aperture in the head :28 of the pin and with the other extremity M thereof engaging an aperture M in the outer face of the eccentric M. The spring thus tends to turn the eccentric 41 normally in a direction adapted to swing the gripping dog ill downwardly against the surface of the strap. The gripping dog til has a recess 48 in the lower part thereof which is engaged by a movable block 55. A coil spring 55 is mounted in this recess and engages a recess in the block to force it normally against a lug ill which forms a part of the casing 35. The spring 58 thus tends to swing the gripping dog ll] in a counterclockwise direction, as viewed in Fig. l, so that the upright face M of the gripping dog bears against a stop screw 58 which is adjustably mounted in a lug 59 carried by the casing 35. A nut till is mounted on the projecting end of the stop screw 58 to secure it in adjusted position. The ten.- sion in the strap 37, being directed toward the left as viewed in Fig. 3, normally tends to tighten the grip of the dog ill upon the strap due to the fact that the serrated portion ill of the gripping dog is offset toward the right, as viewed in that figure, from a vertical plane passing through the axis about which the gripping dog pivots. When the tension upon the strap is relieved, the coil spring 59 pressing on the block 55 tends to swing the gripping dog about the eccentric so that the serrated portion lll moves upwardly away from the surface of the strap and'the extent of this angular movement of the gripping dog may be regulated by adjusting the position of the stop screw 58. v

The cam or eccentric ll is adaptedto be moved about thepin lllby means of alever 62 which is secured to or formed integrally with the cam or eccentric, as illustrated in Fig. 6. The lever 62 is provided at its outer end with a transverse handle 52 adapted to be engaged by the fingers of the operator and it is provided adjacent the Whichcarries the feet 38 and 39, as shown in Fig. 13, and when the parts are in the position illustrated in this figure, the outer ball 63 engages the recess 62 to prevent angular movement of the cam oreccentric 41. The release of the lever 62 by the ball 63 is controlled by another lever 65 which has a handle 65 at one end thereof to be engaged by the fingers of the operator and which has an enlarged plate or hub 65 at the other end thereof provided with an aperture 65 which permits the lever to be journaled upon the bushing 49 in. which the pin 48 is secured. This plate 65 is further provided with a recess 95 in its outer side,having a cone-shaped bottom, and when the lever 65 is adapted to register with the bushing 64 so that the lever 62 may then be turned to force the balls inwardly and cause one of them to engage the recess 65 in the controlling lever. The controlling lever 65 is further provided between its ends with a transverse flange 65 having an aperture therein which is slidably engaged by a pin 66 and this pin is pivoted at 61 by a lug 68 carried by the casing 35, as shown in Figs. 2 and 3, and a coil spring 69 is mounted on this pin 66 between the lug 68 and the flange 65 so that the spring tends normally to force the controlling lever toward the normal upright position shown in Fig. 3.

When the lever 65 is in the upright position shown in Fig. 3, the recess 95 in the hub portion thereof is out of registry with the bushing 64 and the balls 63 are thus held outwardly so that the outer one engages the recess 62 in the lever 62 and prevents rotation of the eccentric 41, thus holding the gripping dog 49 in a position where it grips the strap 31 as shown in Fig. 3. If the lever 65 is moved from the position shown in Fig. 3 toward the position shownin Fig. 2, with the resulting compression of the spring 69, a position is reached where the recess 65 registers with the balls 63 and the lever 62 may then be moved angularly with the result that the wall of the recess (it! forces the balls inwardly into the recess 65 as shown in Fig. 15, while the rotation of the lever 62 may be continued in an upward direction to cause the elevation of the gripping dog 49 out of engagement with the strap 31. When the lever 62 is again operated to rotate the eccentric and cause the dog to be lowered into engagement with the strap, the balls will again enter the recess 62 as the lever 65 is returned to its normal upright position by the action of the spring 69 so that the lever 62 will then again be locked in its lower position until the operator wishes to release the strap from. the grip of the dog 49.

The drum 4|, upon which theend 31 of the strap is wound during the operation of drawing the strap taut around the package, is journaled in bushings 19 and 1| mounted in bearing members carried by the casing 35, as shown in Fig. 16, and the intermediate part of I this drum has formed integrally therewith a gear 12 which is adapted to mesh with a pinion 13 secured on or formed integrally with an intermediate shaft 14. This shaft 14 is journaled in bushings 15 and 13 which are mounted in bearing members 11 and 18, respectively, secured in the walls of the casing 35. Adjacent the bushing 16, the shaft 14 has formed integrally therewith, or secured thereon, a gear 19 which is driven by a pinion 89 secured upon the shaft 8|. The shaft BI is journaled in bushings 82 and 83 which are mounted in the bearing member 59 and in the inner wall of the casing 35, respectively. The hub of thepinion 89 has secured thereto a worm wheel 84 which meshes with a worm 85 secured upon the longitudinal shaft 86. The outer end of the shaft 86 is journaled in a ball bearing unit 81 which is. mounted within the tubular bore 35 of the easing, as shown in Fig. 9, and the inner end .of this shaft is journaled in another ball bearing unit 88 which is mounted in a portion of thisbore having a reduced diameter Where it seats against an annular shoulder 89. The ball bearing unit 88 is maintained in position against the shoulder 89 by means of a cup-shaped retaining member 99 which fits within the bore and which is held in place by a nut 9| threadedly engaging the end of the bore and having a stem Ill which bears against the end face of the retaining member 99. The shaft is held against endwise movement with respect to the ball bearing unit 88 by means of a washer 92 and nut 93 mounted on the end of the shaft. In this way a relatively rapid rotary motion imparted to the shaft 86 is transmitted through the train of gearing described above into a comparatively slow rotary motion of the drum 44 on which the end of the strap is wound during the operation of drawing it taut.

The shaft 89 is adapted to be driven by the electric motor mounted in the auxiliary casing 35 and in order that this driving power may be automatically disconnected when the strap 31 has been drawn taut around the package to a predetermined degree, a clutch is provided for disconnecting the motor when that degree of tautness in the strap has been reached. For this purpose, a clutch disk 95 is secured on the shaft 89 adjacent to the ball bearing unit 81, the hub of the diskin this instance being extended within the ball bearing unit. The disk 95 is provided with recesses 95 which are normally engaged by the spherical balls 96 which also extend into openings 91 formed in the radial disk of a clutch gear 91 which is arranged to revolve about the shaft 86 and which has its peripheral flange extending around the outer edge of the clutch disk 95. When the balls 99 are in engagement with the recesses 95 as shown in Fig. 16, the clutch gear 91 drives the clutch member 95 and thereby actuates the worm shaft 86. r The clutch gear 91 is driven by an intermediate gear 98 which is mounted on a roller bearing unit 99 carried by a short shaft I99 which has one end secured in the end wall of the motor casing and the other end secured in the end plate IIll of the casing 35 which is detachably secured thereto by screws I92. The intermediate gear 98 is driven by a pinionl93 which is secured on or formed integrally with the motor shaft I 94. This motor shaft is mounted to revolve in a ball bearing unit I95 carried by the end wall of the motor casing 35 When a predetermined degree of tautness has been set up in the strap 31 by the rotation of the drum 4|, the clutch balls 96 are adapted to move out of the recesses 95 due to the wedging action of the semi-spherical walls of these recesses, thereby breaking the connection between the clutch gear 91 and the clutch member 95 so that the worm shaft 86 will no longer be driven. The point at which the balls 96 thus move out of driven engagement with the clutch member 95 is determined by certain adjustable mechanism in-' cluding a cap member I91 which normally seats against the outer end face of the clutch gear 91 opposite the balls 96 so that it maintains the balls in engagement with the recesses 95. This cap member I91 is journaled upon a bushing I99 collar H and has its outer end secured within the annular groove of an adjusting ring H3.

' This adjusting ring fits within the tubular bore IllI of the hub portion Hil of the end plate I BI and the lower part of the ring H3 is provided with a downwardly extending projection 3 which engages a groove IIlI in the bottom of the hub portion of the end plate for the pur- I pose of preventing the ring from rotating. This adjusting ring H3 is internally threaded and is engaged by the external threaded adjusting nut II5 which is recessed at its inner end to fit over the hub portion of the cap member Iiil' and which is provided at its outer end with a reduced part H5 journaled in the outer end of the hub portion IIlI of the end plate. This adjusting nut H5 is provided at its outer end with an axially extending recess I I 5* of hexagonal or other noncircular cross-section to be fitted by a wrench so that the adjusting nut may be rotated to cause longitudinal movement thereon of the adjusting nut II3, thereby varying the normal compression of the spring IIZ. In order that the balls 96 may become disengaged from the recesses 95 in the clutch member 95, it is necessary that the balls move longitudinally of the shaft 86 against the compression of the spring I I2 and by varying the initial compression of this spring, the degree of tautness which is brought about in the strap 31, before the driving connection to the winding drum is broken, may be varied as desired.

The sealing head MI by which the metal seal 42 is applied to the overlapping strap ends, comprises a housing I29 having inner and outer side plates I20 between which are mounted a pair of sealing jaws IZI. These jaws are pivoted on pins I22 which extend through the side plates and which are engaged on the inner or under side of the sealing head by nuts I23. A bolt I24 extends through the side plates between the upper parts of the jaws and isengaged at its inner end by a nut I25. Each jaw IZI is made up of a plurality of die plates including a series of bending dies I26 and a plurality of intermediate cutting or shearing dies I21. All of these dies are engaged by the pivot pins I22 and, in addition, they are restrained against relative angular movement by other pins which extend through registering apertures in the die" plates of each jaw and which bear at their ends against the side plates IZII of the head. When the sealing head MI is swung by the handle 45 from the position shown in Fig. 2 to the position shown in Fig. 3, the jaws I2! are caused to embrace a channed shaped seal d2 which is mounted over the overlapping strap ends, as shown by dotted lines in Fig, 2. The handle 45 may then be moved about its pivot to cause relative movement of the jaws I2I with the result that the bending dies I26 first bend the side walls of the seal downwardly and then inwardly about the overlapping strap ends,after which the shearing dies I21 shear the lateral edges of the seal and the enclosed strap ends to form the type of interlocking joint which is described and claimed in the U. S. patent to Ralph H. Norton,.No. 1,260,- 016, dated March 19, 1918. I The upper ends of the bending dies I26 of each jaw extend beyond the upper extremities of the shearing dies I2? and these projecting portions of the bending dies are adapted to receive between them the lower ends of a pair of links I33 to which they are pivotally connected by pins I34. These links converge upwardly and are pivotally connected at their upper ends by a single pin I35 to the depending flanges I36 of a rack bar I36 which is mounted to reciprocate between the upper portions of the side plates i20 When the rack bar is forced downwardly, it causes the lower ends of the links I33 to separate, thereby causing a corresponding inward movement of the lower portions of the jaws. This movement of the rack bar I36 is effectedby a pinion I37 which is mounted upon a shaft I38 journaled in the upper transverse bars I39 of the head 14. These bars I39 and also the inwardly extending projection 626 of the inner side plate are journaled upon a pin or bolt I46 which is secured in a stationary position in a bracket MI carried by the end'of the casing 35. In this way, the head M is adapted to swing bodily about the pin MI! in moving from theelevated position shown in Fig. 2 to the position shown in Figs. 27 and 28, where the lower portions of the jaws embrace the seal 12 on the overlapping strap ends. In addition to this bodily movement of the head M, the jaws I2I have the relative angular movement previously referred to for the purpose of bending and deforming the seal and the overlapping strap ends, and it is desirable that both of these movements of the head and of the jaws be effected by the single operating lever 45, previously referred to. For this purpose, the lever 45 is keyed upon the projecting end of the shaft I38 which carries the pinion I37 for actuating the jaws and connections are provided whereby this lever may also be utilized for swinging the head M- about the pin It without at the same time effecting relative movement of the jaws.

The locking mechanism for bringing this about includes a locking bar I43 which is pivotally mounted upon the pin Hit and which is also pivotally engaged by the projecting end of the shaft I38. The shaft may be provided with an angular groove I38 to receive a pin I42 which is secured in the member 33., The bar I43 is provided between the pin I 16 and the shaft I38 with a cylin drical opening Hi3 extending completely therethrough and adapted to receive a pair of spherical balls IM. These balls are adapted to move partially out of the opening IAII into a recess '45 formed in the side face of the hub of the operating lever 35 or into another similar recess I45 which is formed in the side face of a block I45 mounted adjacent the bracket I ii. When the head 44 is in its uppermost position, as shown in Fig. 2, and the lever is in the position shown in that figure, one of the balls is adapted to extend into the recess 45 in the hub of the operating lever while the other end of the opening Mt in the locking bar is closed by the end face of the block I45 so that an upward movement of the lever it toward the'right, as viewed in Fig. 2, would then swing the head it bodily downward about the pin M0 toposition the jaws over the seal on the overlapping strap ends, as shown in Fig. 3. As the limit of thisbodily movement is reached, the bar I43 will reach the position shown in Fig. 19 where the balls I44 will register with 75 .the recess I 45 in the block I45 and the wall of the recess I45 will then exert a wedging action upon the coacting ball to cause the balls to move toward the right, as viewed in Fig. 19, until one of. these balls engages the recess I45 and until :the' other ball is free of the recess 45 The lever 45..will then be free to turn with respect to the locking bar I43 and the continued motion of the lever 45 in the same direction will cause relative movement of the jaws IZI through the pinion I31 andthe rack bar I36, thereby bending the ;seal and deforming the edges of the strap and seal. When the sealing operation has been completed, the lever 45 will be moved upwardly with the result that the initial motionthereof. will cause the lower portions of the jaws to separate from each other and'when this separation has reached the point where the upperpartsof the jaws engage the transverse bolt I24, further angular movement of the operating lever 45 about the pivotal axis of the shaft I38 will be prevented and further pressure on the lever will cause the entire head 44 to move bodily upward about the pivot I40. During this upward movement of the lever 45, a point will be reached where both recesses 45 and I45 will align with the balls I44 I and the bodily movement of the head will cause the wall of recess I45 to force the balls partially into the recess 45 asthe upwardly bodily swinging-.jmovement of the head 44 continues, so that when the head reaches its upper position, the operating lever 45 will be locked to the locking bar I43 in readiness for the. next downward swinging movement of the head. The sealing mechanism described above and the parts associated therewith are described and claimed in my copending divisional application, Serial No. 225,680, filed August 19, 1938.

The electric motor contained in the casing 35 is connected in an electric circuit which is shown diagrammatically in Fig. 10. This circuit comprises two line conductors I50 and I5I and a conductor I52 connected to the. ground, all of which are contained in a single conduit I53. The conductor I50 leads to the terminal I54 of a reversing switch I55 and the other conductor I5I leads to the field winding I56 of the electric motor, the rotor of which is indicated diagram.- matically at I51. From the other end of the field winding I56 a conductor I58 leads to the terminal I59 of a circuit controlling switch I65. This switch has a blade I6I whichis adapted to engage a terminal I62 connected by a conductor I63 to a terminal I64 of the reversing switch which is opposite to the terminal I54. From the terminal I59 of the switch I60 a conductor I65 leadsto a terminal I66 of the reversing switch and from a point on the conductor I50 another conductor Ifi'I leads to a terminal Hill of the reversing switch which is opposite to the terminal I66. The terminals of the motor armature are connected by conductors I10 to two intermediate terminals Ill and I12 of the reversing switch which are adapted to be connected to either of the terminals I54--I65 or IB4-I6B by the blades I13. By moving the blades from the position shown by full lines in Fig. 10 to the position shown by dotted lines, the connections to the rotor of the motor are reversed and the direction of rotation is thereby reversed. The switch IE0 is mounted in the handle 43 of the device, as shown in Fig. 9, so that the blade IGI may be conveniently manip-. ulated by a finger of the operator for opening and closing the circuit when desired. The reversing switch has an operating handle I'M which is 10- ing drum 4I.

cated at the end ofzthe handle43 in a position to be conveniently engaged by the finger of theoperator when it is desired to reverse the direction of rotation of the motor, which occurs after the strap has been wound and the seal has been api plied when it is desirable to reverse the direction of rotation of the drum II for a short interval in order to loosen the length of strap which has been wound thereon, thereby enabling the operator to remove the strapjfrom the slots of the drum.

I In the operation of the device, the end 31 of the strap is first placed over the foot 38 and the lever 52 is operated to move the gripping dog 40 downwardly into engagement with the strap.

I When that has been done,. the controlling lever 65 is operated to cause the balls 63 to lock the lever 62 to prevent its actuation for elevating the gripping dog from the gripping position. The strap is then passed around the package and the other end portion 31 thereof is passed transverselythrough one of the slots in the end of the wind- The operator then operates the switch blade I6! on the handle 43 to cause the motor to be actuated with the result that the drum M is turned and the strap is gradually wound thereon as it is tightened around the package 36. When a predetermined tension has been set up in the strap, the wedging actionof the bottoms of the recesses 95 on the balls. 96 will overcome the compression of the spring I I2, with the result that the retaining member III! will be forced longitudinally and the balls 96 will move out of the recesses 95 so that the clutch gear 95 will then rotate freely without at the same time I rotating the clutch member 55 or the shaft 86. The clutch gear 91 will then continue to rotate with the balls 96 temporarily engaging the recesses 95 at each half revolution of the clutch gear until the switch is actuated to stop the motor. Afterlthis has been done, a seal42 is placed over the overlapping strap ends and the lever 45 is. actuated to swing the sealing head 44 downwardly and then to operate the jaws IZI of the head. to form an interlocking joint between the seal and the strap ends. It may then be desirable to reverse the direction of rotation of the motor in order to loosen the scrap which has been wound on the drum 4| and this may be done by actuating the switch handle I14, causing a 'short period of reverse rotation with the drum 4 I. The motor is then stopped and the end por- I tion of the strap which has been in engagement with the drum may be removed therefrom by sliding the casing sidevvise and removing the foot 39 from its position beneath the strap, after which the projecting end portion of the strap adjacent the seal 42 may be cut off. To facilitate the re movalof the foot 39 from its position beneath the strap, it may first be desirable to release the gripping dog 40 from the strap so that the entire casing may be removed laterally with respect to the strap and this may be done by actuating the controlling lever 65 to permit the balls 63 to move out of their locking engagement with the lever 62 whereupon the lever '52 may be actuated to rotate the eccentric 4'1 and cause the elevation of the dog 40 which will then tilt automatically toward the right, as viewed in Fig. 2, under the infiuence of the spring 55, so that the serrations 40 will move out of engagement with the surface of the strap.

Although one form ofthe invention has been.

shown and described by way of illustration, it will be understood that it may be constructed in various other embodiments coming within the scope of the appended claims.

, I claim:

1. The combination in a strap stretching device, of a casing having a flange. adapted to extend beneath a strap, a gripping dog adapted to engage said strap, and means for locking said gripping-dog in engagement with said strap.

2. The combination in a strap stretching device, of a casing having a flange adapted to extend beneatha strap, a movable gripping dog positioned over said flange, a lever for operating said gripping dog, and locking means adapted to prevent operation of said lever when said gripping dog is in engagement with said strap,

3. The combination in a strap stretching device, of a casing having a flange adapted to extend beneath a strap, a gripping dog extending over said flange and adapted to engage said strap, means for moving said gripping dog intoengagement with said strap, locking means for preventing reverse movement of said gripping dog, and a lever for controlling the operation of said looking means.

4. The combination in a strap stretching device, of a casing having a flange adapted to extend beneath a strap, a gripping dog positioned above said flange, an eccentric member having said gripping dog pivotally mounted thereon,

means for rotating said eccentric to move said gripping dog into engagement with said strap, locking means for controlling the rotation of said eccentric, and a lever for controlling the operation of said locking means.

5. The combination in a strap stretching device, of a casing having a flange adapted to extend beneath a strap, a gripping dog positioned above said flange, an eccentric member having said gripping dog pivotally mounted thereon, a lever for rotating said eccentric, said lever having a recess, a controlling lever mounted adjacent said first named lever and having a recess, and means for supporting locking balls between said levers to move into either of said recesses depending upon the positions of said levers.

6. The combination in a strap stretching device, of a casing having a flange adapted to extend beneath a strap, a gripping dog positioned above said flange, an eccentric member having said gripping dog pivotally mounted thereon, a lever for rotating said eccentric, said lever having a recess, a controlling lever mounted adjacentsaid first named lever and having a recess, means for supporting locking balls between said levers to move into either of said recesses depending upon the positions of said levers, and resilient means for normally returning said controlling lever to a position wherein said locking balls prevent movement of said first named lever.

' WILLIAM C. CHILDRESS.

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