US3442203A - Automatic strapping machine employing friction-fused joints - Google Patents

Description

May 6, 1969 R. J. @BIELLA 3,442,203

AUTOMATICi STRAPPING MACHINE EMPLOYING FRICTION-FUSED JOINTS Filed Aprillo, 1967 sheet of 'r May 6, 1969 R. J. KOBIELLA 3,442,203

AUTOMATIC STRAPPING MACHINE EMPLOYING FRICTION-FUSED JOINTS Filed April l0. 1967 Sheet a of? f mw May 6, 1969 R. .1. KOBIELLA 3,442,203

AUTOMATIC STRAPPING MACHINE EMPLOYING FRICTION-FUSED JOINTSI Filed April lO, 1967 Sheet i of 7 TTQRA/IZI R. J. KOBIELLA May 6, 1969 AUTOMATIC STRAPPING MACHINE EMPLOYING FHICTION-FUSED JOINTS Sheet 4 of? Filed April l0, 1967 May 6, 1969 R. J. KOBIELLA 3,442,203

AUTOMATIC STRAPPING MACHINE EMPLOYING FRICTIONFUSED JOINTS Filed April 1o, 1967 Sheet 5' of '7- R. J. KOBIELLA May 6, 1969 AUTOMATIC STRAPPING MACHINE EMPLOYING FRICTIONFUSED JOINTS Sheet Filed April 10, 1967 May 6, 1969 R. J. KoBlELLA 3,442,203

AUTOMATICSTRAPPING MACHINE EMPLOYING FRICTION-FUSED JOIN'FS Filed April 1o, 1967 sheet 7 of 7 United States Patent O 3,442,203 AUTOMATIC STRAPPING MACHINE EMPLOYING FRICTION-FUSED JUINTS Robert J. Kobiella, Rolling Meadows, Ill., assignor to Signode Corporation, a corporation of Delaware Filed Apr. 10, 1967, Ser. No. 629,799 Int. Cl. B65b 13/04, 13./34; B32b 3]/08 U.S. Cl. 100-26 19 Claims ABSTRACT F THE DISCLOSURE This disclosure is directed to an automatic strapping machine wherein plastic strap is fed about a package at a high rate of speed into overlapping position with the trailing end of the strap. The strap disposed about the article is tensioned and the overlapped ends are moved into engagement under pressure. The straps are moved relative to each other at a high rate of speed to form a friction-fused joint at the interface regions. The strap ends `are in tension during the formation of the fused joint with the result that the stress distribution existing in the strap during fusion and after the joint has been formed as part of the complete loop is similar.

The present invention relates to an automatic strapping machine wherein plastic strap is automatically fed around an article, tension drawn thereon, and the overlapped strap portions secured in place by a joint formed by frictionally fusing the interface regions together.

Heretofore, plastic strapping has been extensively used for strapping articles, but only recently has such strap been secured in place by fusing the overlapping strap ends by the generation of heat between the interface surfaces created by the friction forces resulting from the rapid relative movement of the Strap portions when biased together under substantial pressure. Various tools have been employed for securing the strap in place by means of a friction-fused joint, but prior to this invention, there has been no machine available which automatically disposes the `strap about a package, tensions it in position, and then forms a friction-fused joint by gripping the overlapped strap portions and moves them relative to each other without the application of any other external members to the tensioned strap during the fusion operation, It has been ascertained that a friction-fused joint that is formed when the only forces acting on the tensioned overlapped strap portions are those imposed by the members forming the point makes for a highly etlicient joint.

Another obviously desirable feature in an automatic strapping machine is one in which the strap can be fed at a relatively high speed, yet tensioned at a low speed and proportionally higher torque by the use of a single motor and drive mechanism. This desirable attribute, while not limited in its application to an automatic strapping machine employing friction-fusion mechanism is also part of the present invention.

The mechanism hereinafter disclosed provides for highspeed, economical, substantially trouble-free operation.

In accordance with the present invention, there is provided a fully automatic strapping machine which will feed strap at a high rate of speed about an article, after which the leading end of the strap will be retained in place. The trailing end of the strap is then tensioned to tighten the strap about the article. After the strap has been tensioned about the article and the strap placed in overlapping relationship, the overlapping strap portions are squeezed together and moved relative to each other to form a friction-fused joint. When the friction-fused joint is being formed, there are no other members en- ACC gaging the strap, with the result that the tension previously imposed on the strap acts during the period that the joint is being formed. The existence of the loop tension on the overlapping strap portions; during the fusion operation provides for a more eiiicient strap joint. After the joint has been at least partially solidified, the straps are released and the full tension in the loop acts on the joint. The friction fusion jaws are at and hold the strap portion in the same general configuration that the joint assumes after it is completed and the loop of strap is free of the strapping mechanism.

The transmission of the load through the joint is significantly improved, presumably because the Warm or hot state of the strap portions at the joint area at the time the joint is tensioned makes these strap portions more ductile and allows them to undergo plastic deformation so that the joint may elongate without cracking. When the joint ultimately cools and freezes, the strap portions at the joint lose ductility and the joint is in effect prestressed. When the load on the joint is ultimately removed, as by cutting the strap loop, the joint assumes a wavy configuration evidencing this prestressed effect. When making a friction-fusion joint in accordance with the present invention, the stress distribution which exists in the strap during fusion and later as part of the completed loop is similar, which is obviously highly desirable.

The foregoing method of operation is accomplished by a mechanism, which, while appearing to be quite cornplex, employs simple mechanical components. The feeding and tensioning of the strap, as well as the forming of the joint after the straps have been placed in abutting relationship under high pressure, is accomplished with but a single motor through suitable clutches and gears to sequentially operate the feeding, tensioning, and sealing mechanisms at the appropriate time.

Briefly, the strap is fed at a high rate of speed about the article to be strapped. Once the strap has been disposed about an article, the motor is reversed to draw tension on the strap, and thus form a tensioned loop about the article. After the tension has been drawn, the motor is disengaged from the tensioning mechanism and acts to operate the sealing mechanism through a cam and plate arrangement which serves to move the overlapped strap portions into frictional engagement. After the straps have been disposed in frictional contact under high pressure, a vibrator contacting one of the straps is operated to move one of the straps relative to the other to fuse the interface region of the overlapped strap portions. Prior to the fusing of the overlapped sections, the strap loop has been severed from the strap roll by a suitable cut-olf mechanism located adjacent the strap gripping mechanisms. After the joint has been formed, the motor is then reversed and acts to operate the feeding mechanism and begin a new cycle.

The advantages of this invention will be seen from the following description taken in conjunction with the attached drawings, in which:

FIGURE l is a schematic cross-sectional view 0f a strapping machine and associated strap guide with an article located therein to be strapped;

FIGURE 2 is an elevation view of the strapping machine shown partially broken away to illustrate various component parts;

FIGURE 3 is a plan view partially broken away of the strapping apparatus shown in FIGURE 2;

FIGURE 4 is a sectional view taken along line 4-4 of FIGURE 2;

FIGURE 5 is a sectional View taken along line 5-5 of FIGURE 3;

FIGURE 6 is an elevation view of the tension clutch;

FIGURE 7 is an end view of the tension clutch illustrated in FIGURE 6;

FIGURE 8 is a perspective view of the strap cutter;

FIGURE 9 is an elevation view partially broken away showing the mechanism for gripping the overlapped stra-p sections and taken along line 9-9 of FIGURE 4;

FIGURE 10 is a perspective view of the carriage and associated gripper elements;

FIGURE 11 is a sectional view of the face gate shown in the strap engaging and disengaging positions;

FIGURE 12 is an exploded perspective view of the cam and clutch mechanisms employed to squeeze the straps together and drive the vibrator;

FIGURE 13 is a plan view of the clutch mechanism shown in FIGURE 12 in position prior to engagement to oscillate the vibrator;

FIGURE 14 is a perspective view of the cam face and associated vibrator plate; and

FIGURES 15-19 are sequential views showing the positions of the various grippers starting from when the inner strap end is maintained in place against the vibrator by a temporary holding gripper through the various steps until the overlapped strap ends are pressed into tight frictional engagement between the vibrator and the main grippers free of any other holding members.

As previously mentioned, this invention is directed t0 a strapping machine for use with plastic strapping. An example of a strapping material that could be used is nylon. The invention is not limited to this specific material as other plastics such as polypropylene could be employed.

Referring first to FIGURE 1, there is illustrated in schematic form a motor 10 that is used to drive the feeding, tensioning, and sealing mechanisms through suitable drive mechanisms to be described in detail here inafter. The feeding and tensioning mechanisms are operated by a belt 12 (FIGURE 3) driven by the motor 10. The feeding mechanism pays off strap from a roll 21, past the feeding and tensioning wheels, through the joint forming mechanism and around a strap guide 14 to envelop the article 16 to be strapped located within the guide 14. The guide 14 can be of any suitable design and the `details thereof are not important to an understanding of the present invention.

Turning now to FIGURES 2 and 3, there can be seen various details of the feed and tensioning mechanisms which provide for a rapid feeding of the strap and a lower tensioning rate to facilitate pulling a high torque on the strap utilizing the single motor provided for this purpose. The particular feed and tensioning mechanism. to be described is usable for metal strap as well as plastic strap and could be employed in mechanisms other than that using a friction-fused joint. While the particular novel feeding and tensioning mechanisms employed in the instant strapping machine will be described in some detail in this application, since the automatic strapping machine forming the subject of this application must by its nature include a feeding and tensioning mechanism, a separate application Ser. No. 612,910 directed to this feeding and tensioning mechanism has been led in the name of the instant inventor and assigned to the assignee of the present application. The application in question is entitled Strap Feed and Tensioning Mechanism, iiled Jan. 31, 1967.

For ease of understanding, the various portions of the automatic strapping machine will be described in sections, starting iirst with the feed mechanism.

Strap feed mechanism Briey, the feeding arrangement to be described hereinafter enables the strap to be fed at a very high rate, which is possible since there is essentially no impediment to its travel from the strap supply past the feeding and tensioning wheels, past the sealing mechanism, through 4 the strap guides, and back into overlapping relationship with the lead end of the strap.

Through suitable drive mechanisms described hereinafter, and as best illustrated in FIG. 2 the strap 20 fed from the roll 21 (FIG. 1) is directed into a lower guide 22 to between lower pinch rolls 24 and feed wheel 28 that is partially surrounded Eby a guide 26. The strap is directed about the feed wheel by the guide 26 and is biased into engagement with the feed wheel by the upper pinch rolls 30, which provides the initial energizing force for the wrapping eiect. The pinch rolls 24, 30 are biased into engagement with the feed wheel by a tension spring 31. The angle of wrap around the feed wheel provides the pulling force for taking strap from the feed roll 21. After leaving the feed wheel 28, the strap enters a strap guide 32 disposed adjacent to and partially surrounding the tension wheel 34. The resistance of the lead edge of the strap contacting the guide 32 tends to make the strap hug the curve of guide 32, keeping the strap from any appreciable contact pressure against the tension wheel. In this way, the tension wheel does not impede the high-speed feeding rate imposed on the strap by the feed wheel.

After the strap leaves the tension wheel 34, it moves through an upper guide 38 past a gripper member 40, which, as described hereinafter, functions to hold the lead end of the strap in place about the package when tension is applied to the strap.

Located adjacent the gripper member 40 is a stationary cutter 42 which has an opening 44 through which the lead end of the strap passes (see FIGURE 8). The strap then moves under a face gate 46 and into strap chutes 14 surrounding the package to be strapped. The face gate 46 functions to separate the overlapping strap portions during feeding, thus facilitating the feeding operation. As described hereinafter, the face gate 46 is subsequently moved out of the position shown in full lines in FIGURE 11 to that shown in dotted lines therein to permit the overlapped strap portions 20a, 2Gb to be placed in overlapping relationship under substantial pressure when the joint is to be formed.

After leaving the chutes 14, the strap travels through the gate 48 and the space provided between the vibrator 50 and gripper 40. The vibrator `50` functions to form the friction-fused joint between the overlapping strap portions 20a, 20b and will be discussed in detail in the portion of this application dealing with the sealing operation. The strap is directed over the stationary cutter 42 and face gate 46 to where it engages a stop 52. When the stop 52 is engaged, the strap which is being continuously fed by the motor expands outward into the chamber 53 located adjacent the tension wheel 34 against the action of a pivotally mounted drop-out arm 57. The clockwise movement of the arm 57 brings it into contact with a switch 59 that stops the motor 10. Any overrunningr of the motor merely results in a further accumulation of strap in the chamber 53. The obvious advantage of such an arrangement is that whatever impediment the strap may encounter during the feeding cycle, the motor will be shut off to prevent milling of the strap. This design also prevents the trapping of strap between the tension and feed wheels, which could otherwise occur if the motor was not turned olf promptly. Such trapping of the strap would require disassembly of the machine to clear the strap, and avoidance of this problem is highly desirable. The dropout arm 57 is designed to initially provide substantial resistance against privotal movement, but once it starts swinging, the resistance substantially decreases. The switch can be designed to be actuated after any given travel of the dropout arm. After the motor has stopped, a solenoid 54 is energized through suitable electric circuitry, which through linkage 55 causes the gripper 40 to engage and hold a portion of the lead end of the strap against the vibrator 50.

The operation of the gripper `40 and its associated mechanisms can best be seen by referring to FIGURES -19. Essentially, the gripper 40 is energized (moved upward into engagement with strap end a) by solenod 54 which moves the linkage 55 to the left, as viewed in FIGURE 15. The linkage 55 including the yoke 55a and spring 55h acts on a pin 57a that is secured to link 57. The link 57 is connected to the gripper 40 through pin 61. With this arrangement movement of linkage 55 to the left results in spring 55h moving pin 57a to the left which moves link 57 in a clockwise direction about its pivot `59. This clockwise movement of the link 57 raises gripper 40 into engagement with strap end 20a and acts to secure it against vibrator 50. It is to be noted that pivot 59 is secured to reciprocating rod 67, which as shown in FIG- URE 15, is retained in position when the gripper 40 is initially energized by an interconnection with gripper 144 through pin 142a located in slot 67a of member 67. As will be described in detail hereinafter when the gripper 144 is moved upward to act against the overlapped strap ends the member 67 will be moved to the right to effect disengagement of gripper 40 from strap end 20a. The strap can then be tensioned about the article.

Returning to the specifics of the feeding mechanisms it is noted that the drive mechanism for the feed wheel 28 can best be seen by referring to FIGURE 3. This mechanism includes a clutch shaft 56y that is driven by the belt 12 connected to the motor 10 in clockwise direction in the illustrated embodiment. The clutch shaft 56 is splined to a tensioner clutch 58, which tensioner clutch includes clutch ramps 60 that are engaged with pinion ramps 62 of the clutch pinion 64 during the feeding operation. The clutch pinion 64 drives a tension gear 66 in a counterclockwise direction that rotates a slip clutch pinion 68 mounted on a shaft 29 to which the feed wheel 28 is con nected in a clockwise direction. The feed `wheel shaft 29 is driven through clutch discs 70 and acts to rotate the feed wheel at the desired speed. The reasons for the various clutches and pinions will become apparent when the slack takeup and tensioning steps are discussed below. It is suilicient to say at this time that with the mechanisms employed, it is possible to use a single motor to accomplish the desired feed and tensioning steps.

Strap takenp and tensioning mechanism After the strap has been fed about the article at a rapid rate and the switch 59 is engaged to stop the strap feed, the motor 10 is reversed through suitable electrical circuitry to rotate in the illustrated embodiment in a counterclockwise direction. The clutch shaft 56 now acts to rotate the tensioner clutch 58 counterclockwise, which rotates the clutch pinion 64, and through it the tension gear 66 clockwise and the slip clutch pinion 68 in a counterclockwise direction. The slip clutch pinion 68 rotates the feed wheel shaft 29 and associated feed wheel 28 in a counterclockwise direction to take up the slack in the strap disposed about the article. Specifically, as can be seen in FIGURE 2, the strap pinched between the feed wheel 28 and the pinch rolls 24, 30, respectively, is caused to be removed in the direction of the counterclockwise direction of the feed wheel 28. As aforementioned, the strap 20 is now pulled back through the chute system 14 and tension is drawn thereon. The strap is retained in position relative to the package bythe gripper 40, which holds the leading end of the strap against the vibrator 50 to keep the strap from being completely pulled back out of the chute and also to provide the necessary means to hold the strap tension reaction.

During tensioning, the strap which has been disposed about the tension wheel 34, but out of contact therewith, by sliding against the guide 32, now acts to wrap itself around the tension wheel 34. The tension wheel 34 is positively attached to the tension shaft 36, but the tension shaft 36 receives its turning moment through an overrunning clutch 72, which is attached to the tension gear 66. Since in the instant embodiment the mechanisms are de- CII signed so that the feed wheel 28 rotates 3.3 times faster than the tension wheel 34, the tension wheel 34 and tension shaft 36 will overrun the tension gear and speed up to match the speed of the feed wheel 28. It is again noted that various mechanisms which can be used in this novel feeding and tensioning mechanism are illustrated in the copending application entitled Strap Feed and Tensioning Mechanism, filed in the name of the present inventor and assigned to the same assignee as the instant application.

After the slack strap has been pulled from the chutes 14 and the strap snugs around the item to be strapped, the strap tension begins to increase. At a preset strap tension, the slip clutch pinion 68 will slip causing the feed wheel 28 to stall. However, since the tension gear 66 is positively driven, it continues to rotate Iand drives the tension shaft 36 through the overrunning clutch 72. The tension shaft 36 rotates the tension wheel 34 clockwise at a slower speed and consequently higher torque for pulling the nal tension around the article being strapped. As the strap tension increases, ultimately all the torque required to pull the strap tight is transmitted through the inclined ramp 60 or the clutch pinion 64. This induces a reaction which `causes the tension clutch 58 to slide along the spline of the clutch shaft 56 in the direction of disengagement with the clutch pinion 64.

The tension setting on the clutch pinion 64, which in effect sets the amount of tension to be drawn on the strap, is determined by a toggle linkage 74 shown in detail in FIGURE 5. By varying the amount of the preload on the toggle linkage 74, which is set by varying the tension of the spring 76 through the action of the spring-adjusting means 78, the desired strap tension can be obtained. That is to say that the clutch pinion will disengage from the tensioner clutch 58 at the strap tension determined by the toggle linkage. After a certain distance of tensioner clutch disengagement, the spring-loaded toggle linkage 74 goes overcenter, thereby snapping the tensioner clutch 58 out of full engagement with the clutch pinion. The feed and tension gear drive train at this point is fully disconnected from the driving motor and further strap tensioning will not take place.

It, of course, can be appreciated that with the release of the driving motor, some means must be provided for retaining the strap tension. Otherwise, after disengagement of the tensioner clutch 58, the tension in the strap will reverse the rotation of the tension wheel and release the tension in the looped strap. This action is avoided by the provision of a sprocket and chain arrangement which locks the feed and tension wheels in position to prevent this from occurring. Specifically, as best illustrated in FIGURE 3, the tension gear shaft 36 engages another overrunning clutch 80 to lock itself to a sprocket 82 tending to rotate the sprocket in ya counterclockwise direction. The sprocket 82 acts on chain 84, which is disposed about a smaller sprocket 86 to rotate it in the counterclockwise direction. The sprocket 86 is positively locked to the feed shaft 29 and would thus act to rotate the feed shaft 29 in a counterclockwise direction. Rotation of the feed shaft 29 rotates the feed wheel 28 counterclockwise, which is in the tension direction, thereby locking the feed shaft 29, which in turn locks the tension shaft 36 through the sprockets and chain. The tension in the strap between the feed and tension wheels combined with the wrap effect of the strap around the tension wheel is sufficient to keep the strap from sliding around the wheels. Thus, the strap is locked in this state although the motor has ybeen disengaged therefrom.

Sealing cycle After the tension has been drawn in the loop, the strapping machine operates to fuse the overlapped strap sections 20a, 20]; into a friction-fused joint. In the illustrated embodiment, the sealing cycle is accomplished by the motor 10 heretofore used for feeding and tensioning along with various gears, cams, clutches, vibrators, and other mechanisms to be subsequently described.

It is, however, important to note at this time that the fusing of the overlapped strap sections takes place when the strap is only held by the pressure between the two principal grippers holding it against the vibrator, since all other external grippers have been released. This results in the total tension in the strap being placed on the joint at the time the fusion is made. This has been found t provide better stress distribution throughout the joint and higher joint strength than is obtained by other known methods.

Specifically, the present invention as illustrated in the present embodiment consists of holding the overlapped strap portions between horizontally parallel pressure members with the full loop tension acting on them. The straps are moved relatively to each other to heat up the interface regions and fuse the overlapped sections together. Since the pressure loaded members are the only means acting on the straps during fusing, the stress distribution that exists in the strap at this time is similar to that which acts on the strap when the loop is completed and removed from the machine.

In the case of nylon strapping the apparatus disclosed herein is operated at a rate of vibration of approximately 4,000 cycles per minute for a period of approximately one second during which time the interface regions of the overlapped strap ends are melted. After the oscillation of the vibrator member has ceased the strap ends will begin to fuse together to form a joint. Generally speaking the stress distribution across the joint in the overlapped strap ends runs from zero at each end of the strap to a maximum at the opposite end of the joint. The stresses in the overlapped strap ends thus run counter to each other which results in a wavy configuration of the joint when the joint is completed.

Referring now to the mechanical details of this portion of the strapping machine, it will be observed that when the tensioner clutch 58 `was disengaged after the final strap tension was drawn, the tensioner clutch was carried along the clutch shaft 56 by the action of the spring 76 through the toggle linkage 74 until the tensioner clutch engaged a clutch pinion 88 disposed on the clutch shaft 56 and having ramps 90. The clutch shaft 56 and tensioner clutch S8, which are still being rotated in the counterclockwise direction, now act to rotate the clutch pinion 88 through ramps 90. The clutch pinion acting through a reduction gear train 92 rotates a cam shaft 94 and the vibrator cam 96, which is secured thereto. Briefiy, the vibrator cam 96 functions through suitable mechanisms to move the overlapped strap portions a, 2Gb into contact under substantial pressure and then to move them relative to each other to form a fused joint.

As seen more particularly in FIGURE 9, the vibrator cam 96 driven by the cam shaft 94 first acts to squeeze the overlapping strap portions 20a, Zib together. This is accomplished by the action of a cam follower 106 located in a cam track 98. The cam follower 106 is connected to a toggle plate 104 that contains a pair of slots 112, 138, which guide the actions of toggle links that in turn funetion to move associated carrier members 126, 142, which carry grippers 128, 144 (FIG. 10), respectively, that engage the undersurface of strap portion 20b and move it and strap portion 20a by the application of substantial pressure against the undersurface of vibrator 50.

The toggle links 114, 116 for moving carriage 126 upwardly are pivotally connected by a pin`108 that is disposed in the upper portion of slot 112. The upper link 114 connects to a pin 124 that is secured in aligned openings in the carriage 126. The carriage 126 contains a gripper 128 having teeth formed therein which engage the undersurface of strap portion 20h.

The right-hand carriage 142 containing toothed gripper 1-44 is controlled by the action of toggle links 132, 134 which are connected at their adjacent ends by a pin 130.

The pin 130 is located in the upper portion of slot 138 formed in the toggle plate 104. The right-hand carriage 142 is connected to toggle link 134 by a pin 140 (FIG. 10). The lower ends of toggle links 116, 132 have pins 109, 111, respectively, which are located in the lower portions of slots 112, 138, respectively.

The slots 112, 138 are designed so that during the upward movement of the toggle plate 104, the pin 108 is first positioned by the incline 110 of slot 112 to push the left-hand toggle links 114, 116 inwardly. During the upward movement of the plate 104, it engages a block 118 secured to a depending plate 46a connected to the face gate 46. This relationship can best be seen by referring to FIGURE 11, wherein it is seen that the toggle plate moves the face gate out of engagement with overlapped strap portions to permit the carriage and associated grippers to squeeze the overlapped strap portions together. At a slightly later interval, the toggle links 132, 134 move the gripper 142 upwardly to move it into engagement with the overlapped strap portions. The right-hand gripper 142 is provided with a sharp corner 146, which engages with the cutter 42 to sever the strap from the strap reel. The strap having been retained in place by the left hand gripper 126, there is no problem of the strap previously tensioned becoming unwound.

The relative movements of the grippers 128, 144 during the gripping steps and after the strap has been tensioned can best be seen by referring to FIGURES 15-19. Starting first with FIGURE 15 the grippers 128, 144 are shown out of engagement with the strap ends 20a, 20b and the gripper in engagement with strap end 20a to maintain it against vibrator 50. When the toggle plate 104 moves upwardly the gripper 128 is first moved into engagement with strap end 20b to urge it and strap end 20a into clamping engagement between gripper 128 and vibrator 50 (see FIGURE 16). Further movement of toggle plate 104 moves the gripper 144 into the position shown in FIGURE 17 wherein the gripper 144 in conjunction with cutter 42 severs the strap from strap end 20b. At this time gripper 40 is still in contact with strap end 20a. It is noted that the upward movement of gripper 144 has moved pin 142a out of engagement with rod 67.

The continued upward movement of toggle plate 104 brings sloped surface 142b thereof into engagement with rod 67 to move it to the right against the action of spring 63. This movement of rod 67 carries 'with it pivot pin 59 which effectively acts to rotate link 57 and associated gripper `40 in a counterclockwise direction out of engagement with strap end 20a. The gripping action with the strap 20a prevents the gripper from moving to the right along with rod 67. The solenoid 54 has been released prior to this action and the counterclockwise movement of link 57 and associated gripper 40 is enhanced by tension spring 69 interconnecting pins 57a and 65. Thus, at the completion of the upward stroke of toggle plate 104, the grippers 128 and 144 have biased overlapped strap ends against vibrator 50 and the gripper 40 has been moved out of engagement with strap end 20a as shown in FIGURE 19. The various parts are then in position to effect the forming of the friction fused joint between strap ends 20a and 20h.

It is noted, as seen in FIGURE 2, that the stroke length imparted by the toggle links 114, 116 and 132, 134 is greater than the stroke needed for the gripper to contact the straps. The overstroke of the toggle links is used to push anchor plate 152 downward, compressing springs 154. The springs 154 thus control the amount of pressure acting on the overlapped straps.

When the straps have been fully squeezed by both grippers 128 and 144, the rotation of the cam shaft 94 has brought the vibrator cam step 156 (FIG. 3) to its dropoff point to allow inner race 158, which is loaded by springs 160, to be forced inward. The inner race 158 carries a clutch jaw 162 into engagement with a clutch jaw 164 (see FIG. 12). Clutch jaw 164 is continuously rotated by 9 belt 166 'from the motor, so when clutch jaw 162 engages clutch jaw 164, it also will be rotated. The clutch jaw 162 drives belt 168 to rotate vibrator eccentric 170 (FIG. 4). Attached to the vibrator eccentric 170 is roller 172 located in a cradle 174 through which the vibrator 50 is rapidly oscillated.

Essentially, the pressure exerted by the grippers 128 and 144 causes the strap portions 20a, 20b to be firmly squeezed together and strap portion 20a to be forced against a toothed surface on the vibrator 50. When the straps have been gripped together under substantial pressure, the oscillating vibrator 50 moves the outside strap position 20a rlative to the inside strap portion 20b, which is held squeezed thereagainst by the toothed surfaces on the grippers 128 and 144. Therefore, the two strap surfaces in contact are being rapidly moved in relation to each other, which by friction produces the necessary heat at the interface regions to fuse the overlapping strap portions together. It is again noted that the strap is only gripped between the vibrator member `50 and the gripper jaws 126, 142. Thus, the tension in the loop is acting on the joint during the formation of the fused joint. It has been found that this results in a stronger joint than would otherwise be formed. Also, as previously mentioned, the stress distribution which exists in the strap during the fusion operation is substantially similar to that which acts vwhen the loop is completed.

Specifically, the inner strap end 20a will have a stress gradient thereacross running from zero at the free end to a maximum at the end of the joint being formed which as shown in FIGURE 19 is immediately above the right hand corner of the gripper 144. The stress gradient in the strap end 20b lwill start ywith zero at the free end and increase to a maximum at the end of the joint which is immediately above the left hand end of the gripper 26.

The design of the cam 96 is such that the rubbing of the two straps relative to each other will cease, after a sufficient period of time, to allow the strap joint to cool, To this end, after a predetermined vibration period wherein the overlapped strap ends have been fused and the jo-int formed but not completely solidified, the inner race 158 will be cammed tout of engagement with the overlapped strap portions by the incline 176 on the inner race 158 and on the vibrator cam 96. The driving action between the races 156, 158 will thus be terminated and the 'vibration stopped. The cam 96 is designed so that a brief period of time will then transpire to allow partial solidification of the joint. A further rotation of cam 96 moves cam follower 106 located in cam track 98 to move toggle plate 104 downwardly to retract grippers 126, 142 from the overlapped strap ends.

A notch 178 (see FIG. 3) on the vibrator cam 96 then comes to a position which allows the cam follower 180, attached to the vibrator 50 to swing inward about an axle 182. T-his rotation of the vibrator 50 pulls its toothed grip surface away from the joint, thereby allowing the tensioned strap to be snapped out of the machine.

Further rotation of the vibrator cam 96 causes ramp- 184 (FIG. 14) to force vibrator 50 back into its initial position. This rotation also continues movement of cam follower 106 downward to return the toggle plate 104, toggle links 114, 116, and 132, 134 and associated gripper- s 128, 144, and carriages 126, 142, along with face gate 46 back to their initial positions. As soon as all the seal mechanisms are in their initial positions, a trip arm 186 attached to the cam shaft 94 actuates a limit switch 188, which through suitable electrical circuitry reverses the drive motor 10.

The clutch shaft 56 now starts to rotate the tensioner clutch S8 in the clockwise direction. The inclines of the tensioner clutch ramps 90` are now tending to drive the clutch pinion 88. Clutch pinion 88 starts to revolve idler gear 190 counterclockwise, but a back stopping clutch 192 prevents the counterclockwise rotation of the idler gear 190, which in turn prevents rotation 'of the clutch pinion '88. The clutch pinion ramps 90 then force the tensioner clutch ramps to yslide out of engagement with each other.

After a certain distance of tensioner clutch disengagement, the spring-loaded toggle linkage 74 goes overcenter, thereby snapping the tensioner clutch 58 out of full engagement with the clutch pinion 8-8. The tensioner clutch 58 is now carried -across to engage ramps `60 of clutch pinion `64. The mechanism is now in position to repeat the cycle and strap a new bundle.

The method of operation of the apparatus is as follows:

The motor 10 is started and through. various cams and gears the feed and tension wheelsI are actuated to first feed and then tension the strap. Briefly, the strap 20 is fed from the strap roll 21 into contact with the feed wheel 28 and is then led about, but out of contact with the tension wheel 34 from where it moves up past the motor ldropout arm 57. The leading strap end then moves through an upper guide 38, aligned openings in gripper 40 and adjacent cutter 42, under the face gate v46, and through a guide chute 14 within which is located the article 16 to be strapped. The strap reenters a gate `48, moves past the top of the gripper `40 and beneath the vibrator 50 into engagement with a stop 52. Further feeding of the strap results in the bulging out of the strap against the dropout arm '57 into the chamber 53, which pivots the dropout arm into engagement with the switch 59 that stops the motor driving the feed wheel. At this time, the gripper 40 is actuated through solenoid 54 and linkage 55 to maintain the lead end 20a of the strap against the vibrator 50 to prevent the strap from unwinding during tensioning.

The motor is then reversed through suitable electrical circuitry and through various cams and gears the tension wheel is driven to draw tension in the` loop. When the desired strap tension is reached, the toggle linkage 74 is moved overcenter to disengage the motor from the tensioning means. A chain and sprocket assembly 82, 84, 86 is provided to prevent the strap from unwinding when the motor has been disengaged from the tensioning mechanism.

The motor then acts, through the action of various clutches and gears, to drive the cam shaft 94 to which is connected the cam 96 that functions to sequentially move the overlapped strap ends against the vibrator member 50 under pressure, cut the strap from its supply, operate the vibrator member to fuse the overlapped strap ends, and move the vibrator out of the way to permit removal of the strapped package. Essentially, the cam 96, through the action of cam follower 106, moves toggle plate 104 to effect operation of the toggle links 1.14, 116 and 132, '134, to move carriages 126, 142, and associated grippers 128, 144, respectively, into engagement with the overlapping straps 20a, 20b to bias them under pressure against the vibrator member 50. During this movement, the face gate 46, which was provided to facilitate feeding of the strap about the package, is pivoted out of contact with the strap to permit the overlapping strap ends 20a, 20h to be moved into frictional engagement. The carriage 142 disposed adjacent the stationary cutter 42 during its upward movement acts in conjunction with cutter 42 to sever the strap 20 leading from the strap roll 21. It is noted that the toggle links are designed so that the carriage 126 and associated gripper 128 are moved into engagement with the overlapping strap portions before the carriage 142 and gripper l1144 contact the cutter 42 to prevent unwinding of the strap.

After the overlapping strap ends have been placed in contact with the vibrator member by gripper 128, the gripper 40 is released so that the tension in the loop is acting on the overlapped strap ends prior to the operation of the vibrator member to fuse the overlapped strap ends together.

Once the overlapped strap ends have been biased against the vibrator at a force determined by the springs 154 acting on the anchor plate 152, the cam 96 has been moved to a position where the clutch jaws `162, 164 are allowed to engage and drive the belt 168, which is connected to the vibrator eccentric 170. The rotation of the vibrator eccentric 170 brings about the vibrating movement of the vibrator 50` to effectuate the friction fusion. The rubbing of the two straps ceases and after a brief period to allow solidi-cation, the cam follower 180 moves into a notch 184 to move the vibrator out of contact with the overlapped strap ends and thus allow the strapped package to be removed from the strapping machine. Further rotation of the vibrator cam 96 results in the movement of the vibrator 50, toggle plate 104, toggle links 114, 116, and 132, 134, grippers 128, 144, and face gate 46 back to their initial positions. As soon as this occurs, a trip '186 attached to cam shaft 94 actuates a limit switch 188, which through suitable electrical circuitry reverses the drive motor. Reversal of the drive motor returns the toggle linkage 74 back overcenter and resets the gear and clutch mechanisms to permit repeating of the strap feed cycle.

It is understood, of course, that t-he various mechanical components that have been employed are merely representative of those that can be used. It is obvious that the novel invention described in detail above could employ other types of gears, clutches, cams and mechanical components in place of those illustrated within the framework of the present invention.

It is, of course, intended to cover by the appended claims :all such variations and modifications as fall Within the scope thereof.

What is claimed is:

1. A strapping machine for providing a tensioned loop of thermoplastic strap about a package comprising means for automatically feeding and tensioning the strap about a package and placing the overlapped strap ends in a substantially flat plane, means for urging and maintaining the overlapped strap ends together under pressure free of any external holding means whereby the tension in the loop acts on the overlapped strap ends, means for oscillating one strap relative to the other to fuse the overlapped strap sections together at their interface regions.

2. A strapping machine as set forth in claim :1 including motor operated means for rapidly feeding the strap about the package and for tensioning the strap about the package at a reduced rate to draw a high tension in the strap.

3. A strapping machine as set forth in claim 1 including single motor operated means for eifectuating feeding, tensioning, and fusing of the overlapped strap ends, said last mentioned means including mechanisms for effecting sequential operation of the strap feeding, tensioning, and fusing operations.

4. A strapping machine as set forth in claim 3 including means for retaining the strap under tension when the motor means is released from the tensioning means to oscillate the straps relative to each other to fuse the overlapped strap ends together to form the tensioned loop.

5. A strapping machine as set forth in claim 1 in which the means for maintaining the overlapped strap ends in contact under pressure consists of horizontally disposed grippers located adjacent a horizontally extending vibrator member, means for guiding the strap about the package and for holding it in place during tensioning, and means for biasing the grippers into engagement with the overlapped strap ends and against said vibrator and for releasing said holding means whereby the overlapped strap ends are exposed to the tension in the loop during the fusing operation.

6. A strapping machine as set forth in claim 5 including a gate means located adjacent the gripper means to facilitate feeding of the strap about the package, and means for moving the gate out of position during the closing movement of said gripper means.

7. A strapping machine for providing a tensioned loop of thermoplastic strap about a package comprising means for feeding a strap, means for guiding the strap about a package to place the leading end of the strap disposed thereabout in overlapping relationship with the trailing end, means for holding the leading end of the strap relative to the package, means for tensioning the strap disposed about said package, means for maintaining the strap ends in overlapping relationship under pressure, means for cutting the trailing end of the strap from its supply, means for releasing said holding means whereby the overlapped strap ends are in tension, means for moving the strap ends relative to each other to fuse the overlapped strap ends, and means for releasing the fused strap portions to permit'removal of the package from the strapping machine.

Y8. A strapping machine as set forth in claim 7 in which the feeding and tensioning means includes a plurality of drive wheels, and motor and gear means therefor whereby the strap is fed about the package at a high rate of speed and the strap is tensioned at a low rate of speed and high torque.

9. A strapping machine as set forth in claim 7 in which the means for maintaining the strap ends in overlapping relationship under pressure consists of a pair of adjacent gripper members wherein one gripper includes means for directing the strap into engagement with the cutter means, means for sequentially operating said grippers whereby the gripper effecting the cutting ofthe strap from its supply will not be positioned against the strap until the adjacent cutter Ihas engaged the strap ends to maintain them in position to prevent unwinding of the strap disposed about the package.

10. A strapping machine as set forth in claim 9 including a single motor operated gear and ca-m means for effecting feeding and tensioning of the strap and sealing of the overlapped strap ends into a friction-fused joint.

11. Apparatus for tensioning and sealing a loop of thermoplastic strap about an article, said apparatus having means for tensioning the strap about the article to form a tensioned loop with overlapping strap portions, means including confronting substantially flat jaws for holding the loop under tension by maintaining said overlapping strap portions together under pressure whereby tension acts on said overlapping strap portions in a sense to establish a stress distribution pattern generally corresponding to the strap distribution pattern ultimately established by the completed loop, and means operable while said overlapping strap portions are held together under pressure to produce relative movement between said overlapping strap portions to fuse and unify the overlapping strap portions.

12. Apparatus as set forth in claim 11 in which the means for maintaining the overlapping strap portions under pressure consists of a vibrator member and a pair of flat jaws adapted to be moved into contact with the overlapping strap portions to bias the strap against the vibrator under pressure to maintain the friction contact and means for moving the vibrator member relative to the fiat jaws to produce relative movement between the overlapping strap portions to fuse and unify them.

13. Apparatus as set forth in claim 12 in which the at jaw members each consists of a carriage and a toothed gripper member secured in place relative to said carriage.

14. Apparatus as set forth in claim 12 including means for sequentially moving the grippers into engagement with the strap and adjacent vibrator member and for severing the strap from its supply comprising a cutter member disposed adjacent the gripper that is last to be moved into engagement with the overlapped strap portions.

15. Apparatus as set forth in claim 14 in which the means for sequentially moving the grippers includes a toggle plate assembly and toggle links connected to said gripper members, and motor driven cam means operably connected to said toggle plate and toggle links.

16. Apparatus for gripping and retaining strap ends in overlapping relationship including a pair of horizontally disposed gripper Imembers and a vibrator member, means for sequentially moving the grippers into engagement with the strap and against the vibrator member, and means for moving the vibrator relative to said grippers to effect fusion of the overlapped strap sections.

17. Apparatus as set forth in claim 16 in which each gripper member includes a carriage and a toothed element aixed in position relative to its respective carriages.

18. Apparatus as set forth in claim 16 in which the means for moving the grippers into engagement with the overlapping strap ends includes a toggle member, toggle links secured to said grippers, and cam means for moving said toggle member and toggle link to place the strap ends under pressure between the grippers and said vibrator member.

19. Apparatus as set forth in claim 16 plus means for setting the gripping pressure and cutter means disposed adjacent one of said grippers and cooperating therewith for cutting the strap from its source.

References Cited UNITED STATES PATENTS OTHER REFERENCES Freyes, Robert N., Fabricating With Friction Heat, in Modern Plastics, November 1945, pp. 142-145.

BILLY J. WILHITE, Primary Examiner.

, Us. C1. XR.

2st-470.3; 10o- 33; 156-73

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