US3679519A

US3679519A - Control system for apparatus for friction-fusing overlapping portions of a thermoplastic strapping ligature

Info

Publication number: US3679519A
Authority: US
Inventors: Robert J Frey
Original assignee: Signode Corp
Current assignee: Signode Corp
Priority date: 1970-06-16
Filing date: 1970-06-16
Publication date: 1972-07-25
Anticipated expiration: 1989-07-25

Abstract

The system disclosed herein is adapted to control the overall duration of the operating cycle of a tool for friction-fusing overlapping portions of a thermoplastic strapping ligature. The operating cycle that is controlled includes the withdrawing of the supply end of the strapping material to tension a loop about a package and the oscillation of a strap gripping member to produce the frictional heat for interface melting and subsequent joinder. The control system includes first and second switches connected in a series circuit with an electric motor, with a first switch being normally closed and a second switch being normally open. A single operating means in a form of a manually engageable push button simultaneously actuates the first and second switches, with the first switch immediately returning to the closed position when the push button is released, and with the second switch having a timer connected thereto so that it returns to the first or open position only after a fixed time interval has elapsed during which the motor is energized.

Description

July 25, 1972 Filed June 16. L970 CONTROL SYSTEM FOR APPARATUS FOR FRICTION-FUSING OVERLAPPING PORTIONS OF A THERMOPLASTIC STRAPPING LIGATURE R. J. FREY 2 Sheets-Sheet l CONTROL SYSTEM FOR APPARATUS FOR FRICTION-FUSING OVERLAPPING PORTIONS OF A THERMOPLASTIC STRAPPING LIGATURE Filed June 16, 1970 2 Sheets-Sheet 2 July 25, 1972 R. J. FREY v 3,679,519

176' 35%; 1 L4 174 I lZ/ 4 152 5 United States Patent 3,679,519 CONTROL SYSTEM FOR APPARATUS FOR FRIC- TION-FUSING OVERLAPPING PORTIONS OF A THERMOPLASTIC S'IRAPPING LIGATURE Robert J. Frey, Mount Prospect, 111., assignor to Signode Corporation Filed June 16, 1970, Ser. No. 46,591 Int. Cl. B32b 31/20 US. Cl. 156-359 12 Claims ABSTRACT OF THE DISCLOSURE The system disclosed herein is adapted to control the overall duration of the operating cycle of a tool for friction-fusing overlapping portions of a thermoplastic strapping ligature. The operating cycle that is controlled includes the withdrawing of the supply end of the strapping material to tension a loop about a package and the oscillation of a strap gripping member to produce the frictional heat for interface melting and subsequent joinder. The control system includes first and second switches connected in a series circuit with an electric motor, with a first switch being normally closed and a second switch being normally open. A single operating means in a form of a manually engageable push button simultaneously actuates the first and second switches, with the first switch immediately returning to the closed position when the push button is released, and with the second switch having a timer connected thereto so that it returns to the first or open position only after a fixed time interval has elapsed during which the motor is energized.

BACKGROUND OF THE INVENTION In the commonly assigned copending application Ser. No. 801,133 of Arvid I. Ericsson filed Feb. 20, 1969 and entitled Electrically Controlled Hand Tool for Friction- Fusing Non-Metallic Strap, now US. Pat. No. 3,586,572, apparatus is disclosed and claimed that accomplishes the friction-fusion bonding of overlapping portions of a thermoplastic strapping ligature in an extremely short period of time. In a commonly assigned application Ser. No. 46,727 entitled Improved Electrically Controlled Hand Tool for Friction-Fusing Non-Metallic Strap, filed concurrently herewith in the name of Ilmar J. Vilcins and Robert J. Frey, improvements upon the basic structure illustrated in the Ericsson application are disclosed and claimed. When operated properly, such tools have produced extremely satisfactory friction-fusion joints. How'- ever, because of the rapid speed of the loop tensioning and friction-fusing operations, a fairly high degree of operator skill is required to terminate operation of the tool after the expiration of an appropriate time interval.

It will be appreciated that if the moveemnt of the overlapping strap portions is terminated too quickly, in suificient frictional heat will be generated at the interface regions so that a joint of inadequate strength will result. If the operation of the tool continues for too long of a time period, excessive frictional heat is generated which again results in the creation of a joint having inadequate strength.

The problem of controlling the overall duration of the friction-fusing operation obtains with many different types of friction-fusion apparatus, and thus the control system of the present invention has general rather than specific utility. However, the control system is particularly well suited for an electric tool of the type disclosed and claimed in the above mentioned Ericsson and Vilcins et al. applications, and thus the disclosures of these applications are incorporated herein in their entirety by this reference, to the extent that they are not inconsistent with the following detailed description.

BRIEF SUMMARY OF THE INVENTION The present invention includes -a novel means for controlling the duration of the time interval of energization of a motor means for moving one strap portion relative to a further strap portion in a friction-fusion operation. In a specific embodiment, the control system includes first and second switches connected in a series circuit with an electric motor, with the first switch being normally closed and the second switch being norm-ally open and connected to a timer means for retaining the second switch closed for a fixed time interval. A common operating means is provided for actuating both switches, with the actuating means being in the form of a manually operable push button that moves the first switch to an open position and the second switch to a closed position. When thhe push button is released, the first switch returns to the closed position and the timer means retains the second switch closed for the duration of the time interval governed by the timer means. In the specific embodiment illustrated herein, the motor means initially drives a strap gripping member in a direction to tension a strapping loop, and after a predetermined amount of tension has been drawn in the loop, the movement of the strap gripping member is converted into oscillating movement, for reciprocating one strap portion relative to another strap portion to generate frictional heat at the interface region therebetween. The timer means controls the overall duration of the tension drawing and oscillating steps.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a friction-fusion tool in a sealing position on a package, with a strapping ligature having been formed into a loop about the package;

FIG. 2 is an enlarged view taken generally along line 22 of FIG. 1;

FIG. 3 is a view taken generally along line 3-3 of FIG. 2; and

FIG. 4 is a schematic wiring diagram of the control system of the present invention.

DETAILED DESCRIPTION While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail only a preferred embodiment of the invention, with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiment illustrated. The scope of the invention will be pointed out in the appended claims.

Referring now to the drawings in detail, a frictionfusion tool is shown generally at 10 in the drawings, and tool 10 includes a frame in the form of a housing defined by

mating housing members

11 and 12 secured together by screws 13. A handle 14 is provided at the upper end of tool 10, and handle 14 is formed of inverted U-shaped handle portions 1'5 and :16 formed integrally with

housing members

11 and 12, respectively. Housing members 11 and :12 are generally thin walled shell-like structures, which collectively define a hollow interior or chamber 17 therebetween.

The tool 10 is shown in position on a package P in FIG. 1, with the trailing end portion 18 of a loop L of thermoplastic strap overlapping a leading end portion 19 of the strap, and with the overlapping strap portions being positioned between a strap gripping wheel 20 and a strap supporting anvil 21. The trailing strap end portion 18 may extend to a suitable supply of strap, not shown. Drive means, to be hereafter described in detail, is provided withinthe chamber 17 of tool for shifting anvil 21 upwardly into strap compressing relationship with respect to wheel 20, for intermittently rotating wheel 20 to withdraw the upper strap portion 18 to the right, as viewed 1n FIG. .1, to'constrict the loop L about the article and place the loop in tension, and for oscillating wheel 20 relative to anvil 21 to produce bodily sliding frictional movement between the opposing surface regions of the overlapping

strap portions

18 and 19 to effect interface melting therebetween.

drive means within chamber 17 includes an electric motor M (FIG. 2), and motor M includes a rotary output shaft 23, the left-hand end of which is supported in a bearing 24 in the rear wall of the housing, and the forward end of which is supported in a bearing 25 that is provided in an intermediate housing wall 26. The righthand end 27 of shaft 23 includes an integral eccentric portion 30. Shaft portion 30 extends through a bore 31 in a slide block 32, and block 32 is mounted for lateral sliding movementwithin a transversely extending, generally cylindrical shaped cavity 33 in the rearwardly extending arm 41 of a rocker member 40. Slide block 31 includes rounded upper and lower surfaces that make slidable engagement within cavity 33.

Thus, when motor M is energized, eccentric shaft portion 30 moves along a circular path concentric with the axis of the shaft, and block 32 is moved up and down, and

from side to side within cavity 33. As will hereinafter.

appear, because of the fixed location of the shaft of gripping wheel 20, blocker 32 also moves axially along eccentric portion 30. The rocker 40 is driven by eccentric shaft portion 30, and rocker 40 is mounted for oscillating movement relative to the'frame about an axis defined by the shaft 45 of gripping wheel 20, shaft 45 being rotatably supported in

housing members

11 and 12. Thus, as block 32 is moved up and down by eccentric portion 30, rocker arm 40 oscillates about the axis of shaft 45, and the slidable mounting of block 32 on eccentric portion 30 allows the block 32 to shift axially during this movement.

Rocker member 40 includes a generally annularly shaped wall 52 that defines a chamber 53 therewithin. A ratchet wheel 54 is provided within chamber 53, and ratchet wheel 54 is provided with a central hexagonally shaped opening 55 that is slidably positioned over a hexagonally shaped shaft portion 50. The ratchet teeth around the periphery of wheel 54 cooperate with a pawl mechanism to be hereafter described for converting intermittent rotary motion of the shaft 45 to oscillating motion.

Shaft 45 further includes a portion 58 of enlarged diameter forwardly of shaft portion 50, and the transition between these shaft portions defines a rearwardly facing shoulder that confines the ratchet wheel 54 against the adjacent planar rocker arm surface. The enlarged diameter shaft portion 58 is rotatably supported in housing member 12 by a suitable bearing, and the strap gripping wheel 20 is provided at the outer end of shaft portion 58.

A one way clutch mechanism 65 is provided in chamber 53 for converting the oscillating movement of rocker member 40 into intermittent rotary motion of shaft 45,

Q 81 (FIG. 3) that is positioned in a vertical bore 82 in clutch-teeth 66 which trap cylindrically shaped rollers 67 'therebetween. Teeth 66 are shaped so as to allow the rocker member 40 to rotate freely in a counterclockwise direction (FIG. 2) relative to the shaft portion 58, but

when the rocker member 40 is rotated in a clockwise direcmembers l1 and 12. Lever 70 includes a tension sensing housing member 12, and the force that spring 81 applies to lever 70 may be adjusted by a set screw 83 that is received in the internally threaded upper end of bore 82. In this manner, the amount of tension in the loop L that is sufficient to pivot the lever 70 can be preselected, so that the tautness of the loop L around the package P can be varied, as desired. 7

Before proceeding with a detailed description of the means for converting the intermittent rotary motion of shaft 45 to oscillating movement, the means for effecting relative movement between strap gripping wheel 20 and anvil 21 to compress the overlapping

strap portions

18 and 19 will be described. In the present embodiment of the invention, the anvil 21 is movable upwardly toward the strap gripping wheel 20, and to this end, the anvil 21 is formed as an outwardly extending shelf at the lower end of a vertically disposed base member 85. Base member 85 includes an enlarged non-circular opening 86 that is positioned over shaft portion 58 to enable the base number 85 to move relative to the shaft 45. The means for shifting plate 85 includes a shaft 88 (FIG. 2) that is rotatably journaled in

frame members

11 and 12 above shaft 45. A torsion spring 89 surrounds shaft 88, and one end 90 of spring 89 bears against housing member 12, while the opposite end 91 of spring 89 extends through shaft 88 (FIG. 2) to bias the shaft 88 in a clockwise direction.

An eccentric pin 92 (FIG. 1) extends outward fiom shaft 88, and pin 92 extends outwardly of frame member 12 where it is rotatably journaled in an opening at the compressing relationship with respect to the gripping wheel 20, and tension has been drawn in the strap loop L, as will also hereinafter appear.

A return lever has a mounting portion fixed to shaft 88 between plate 85 and housing member. 12, andlever 100 has a detent surface 102 (FIG. 1) that is adapted to be retentively engaged by a hook (not shown) on a cutter handle 104. Cutter handle 104 is pivotally mounted upon member 85 at 106, and handle 104 includes an arcuate camming surface, not shown, that is engageable with an abutment on a cutter element 105that is pivotally mounted upon base plate 85 at 107. A knife edge is provided at the lower end of cutter element 105 and the cutting edge severs the upper strap portion 18 when the cutter element is pivoted in a counterclockwise direction, as viewed in FIG. 1, by handle 104 against the bias of a return spring, not shown. When handle 104 is pivoted to disengage the hook on handle 104 from detent 102 on handle 100, torsion spring 89 rotates shaft 88 to swing the lever 100, and the action of eccentric pin 92 lifts plate 85 to bring the anvil 21 into strap compressing relationship with respect to gripping wheel 20.

After the anvil 21 has been moved into strap compressing relationship with gripping wheel 20, and the preselected amount of tension has been drawn in the strap 20, the aforedescribed lever 70 pivots upwardly and a hooked pawl release portion integral with lever 70 moves out of rententive engagement with an inwardly curved detent on a pawl reset lever 116. Pauwl reset lever 116 includes outwardly extending fingers 118 at opposite ends thereof that are received in openings 119 in

housing members

11 and 12, with openings 119 being oversized (FIG. 2) to accommodate rocking movement of the latch reset member 116. Lever 116 includes an upwardly extending portion 122 positioned to engage the pawl 130 for resetting the same, and lever 116 further includes an inclined cam surface 123 that is adapted to be engaged by cam surface 95 on plate 85 for repositioning the pawl 130, as will hereinafter appear.

Pawl 130 is pivotally mounted on a transversely extending pin 131, and the pawl includes a first arm 132 having a toothed end portion positioned to engage the teeth on ratchet wheel 54, and a second end portion 133 positioned to engage the upstanding portion 122 of lever 116. A spring 134 acts between a recess in pawl arm 133 and a recess in the side wall of rocker member 40 for biasing the pawl 130 in a counterclockwise direction, as viewed in FIG. 2. Thus, after the anvil 21 has been raised, finger 93 on plate 85 is moved upwardly and the cam surface 95 on finger 93 is spaced above cam surface 123 on lever 16 to condition the pawl 130 for movement into engagement with the ratchet wheel 54. After tension has been drawn in the strap loop L, lever 70 is moved upwardly to free hook 110 from finger 115 on lever 116, and spring 134 biases lever 116 outwardly to position cam surface 123 below cam surface 95. Concurrently with the movement of lever 116, spring 134 pivots pawl 130 to bring the toothed end 132 of the pawl into engagement with the teeth on ratchet wheel 54, and this engagement prevents the ratchet wheel 54 and shaft 45 from rotating in a clockwise direction, as viewed in FIG. 2.

Thus, when the appropriate tension has been attained in the strap loop L, one way clutch means 65 cooperates to prevent shaft 45 from rotating in a counterclockwise direction, while pawl 130 prevents shaft 45 from rotating in a clockwise direction. Accordingly, as rocker arm continues to oscillate, shaft is effectively locked to the rocker arm, and strap gripping wheel 20 is oscillated in a high frequency-low amplitude mode to move the upper strap portion 18 multi-directionally relative to lower strap portion 19.

The present invention includes a control system for regulating the length of time that motor M is retained energized to thereby regulate the overall length of the tension drawing and friction-fusing operations. The control system of the present invention includes first and second control means in the form of

switches

162 and 164 that are connected in a series circuit with motor M. Switches 162 and 164 are mounted alongside one another within the cavity 17 of tool 10, as can be best seen in FIG. 2.

Switches

162 and 164 are both of the single-pole, double-throw variety, with switch 162 including an actuating lever 166, the switch 164 including an actuating lever 168. Switch lever 166 is normally held in a closed position against contact 162a by a spring 170 that is provided internally of switch 162. Switch lever 168 is normally retained in an open position against contact 164a, by a spring 172 that is provided internally of switch 164.

A common operating means 174 is provided for moving the switch levers 166 and 1-68 toward engagement with contacts 162b and 164b, respectively, and operating means 174 will be best understood from a consideration of FIG. 3. The common operating means 174 is defined by a push button 176 that is mounted for reciprocating movement within a cylindrical recess 178 in housing member 11. The push button 176 includes a manually engageable cap portion 180 having an annular recess 182 therein that provides a seat for one end of a coil spring 184. A body member 186 is snap fit within a central bore 188 in cap portion 180 and extends through an opening in a wall 192 that extends transversely relative to wall 178. Body member 186 includes an enlarged head 190 at one end thereof that is held in engagement with wall 192 by spring 184.

A connector member 194 is fixed to switch lever 166, as by sport welding as shown at 195 in FIG. 2, and the opposite end of connector member 194 overlaps switch lever 168 in alignment with push button head portion 190. Thus, when the push button 176 is moved inwardly from the position of FIG. 3 against the bias of spring 184, connector member 194 simultaneously causes switch levers 166 and 168 to move away from contacts 1 62a and 1641:, respectively. When switch levers 166 and 168 move into engagement with contacts 162b and 164b, respectively, and push button 176 is released so that spring 184 returns the push button to the position of FIG. 3, spring returns switch lever 166 into engagement with contact 162a. Timer means 196 is connected to switch lever 168 and retains the same in engagement with contact 164b for a fixed time interval even though the push button 176 has been returned to the position of FIG. 3.

With switch lever 166 in engagement with contact 162a and switch lever 168 in engagement with contact 1 64b, a series circuit is completed to motor M by

lines

198 and 200 that are connected to a l15-volt 60 cycle source of alternating current. It will be understood that the motor M will remain energized for the length of time that the timer means 196 retains the switch lever 168 in engagement with contact 164b, and that when the switch contact 168 moves into engagement with contact 164a, the circuit to the motor M will be opened to de-energize the motor.

' While the present invention contemplates that many different types of timer means may be provided for controlling switch 164, an air dashpot timer of the type illustrated and described in Product Data Bulletin #675 of Magnecraft Electric Co., 5575 North Lynch Ave., Chicago, 111., has been found to be extremely well suited for the purposes of the present invention. As is set forth in the above mentioned bulletin, the air dashpot timer 196 includes a piston 202 that is movable within a cylinder 204, with the rod end 206 of the piston being connected to the lever 168 of switch 164, as by a fastener 208. Timer 196 is supported in a cylindrical wall 210 of housing member 12, and an adjusting screw 212 (FIG. 3) is accessible through an opening 214 in housing member 12 for controlling a needle valve (not shown) that regulates the rate of air bleed into the cylinder 204 to thereby control the length of time that the timer 196 retains switch lever 168 in the closed position in engagement with contact 164b.

In an exemplary embodiment of the invention, the motor M is retained energized for approximately one second, although periods of energization within the range of second to 1% seconds have produced satisfactory friction-fusion joints. The aforementioned time intervals include the overall length of time to withdraw the slack from loop L by intermittent rotary motion of gripping wheel 20 and the length of time to achieve interface melting by the oscillating movement of wheel 20. The take up of slack in the loop L occurs extremely rapidly, and is normally only a matter of a few inches. Because of the short length of time required to tension the loop, and since this time period would be consistent with a given operator, it does not significantly influence the timing required to elfect the interface melting. Since the timer 196 is adjustable, the timing thereof can be varied to fit any given operator technique.

What is claimed is:

1. A control system for regulating the operating cycle of an apparatus for friction-fusing overlapping portions of a thermoplastic strapping ligature comprising: a drive member for moving one strap portion relative to the other strap portion to generate frictional heat at the interface therebetween; motor means connected to said drive member; a first switch having a control element movable between a first position enabling said motor means to be energized and a second position preventing energization of said motor means; a second switch having a control element movable between a first position preventing energization of said motor means and a second position enabling said motor means to be energized; means for simultaneously moving said control elements from said first positions, whereat the control element of said second switch prevents energization of said motor means, to said second positions, whereat the control eletime interval, whereby said motor means remains ener-' gized for the duration of said time interval.

2. A control system as set forth in claim 1 including means for adjusting the duration ofthe time interval of the returning means.

3. .A control system as set forth in claim 1 in which said motor means is an electric motor, and whereinthe switches of said first and second control elements are connected in a series circuit with said electric motor, said first switch being closed in said first position and open in said second position, and said second switch being open: in saidfirst position and closed in said second position.

, 4. A control system as set forth in claim 3 in which said switches are mounted alongside one another, with each switch including an actuating lever, and wherein said means for simultaneously moving said control elements from said first positions to said second positions includes an operating member movable relative to said levers, and a connector member secured to one lever and engageable with the other lever upon movement of said operating means.

5. A control system as set forth in claim 4 wherein said. connector member is secured to the lever of said first switch.

6. A control system as set forth in claim 1 wherein said ligature is formed into a loop and including driven means connected between said motor means and said drive member for initially moving said drive member in a direction to tension the loop before movement of the one strap portion to generate frictional heat.

I. A control system for strapping apparatus for securing a ligature about an article, which ligature is made of a length of thermoplastic strap formed into a loop having overlapping end portions, comprising: a frame; first and second gripping members on said frame and adapted to receive said overlapping end portions there'between; means for effecting relative movement between said gripping members to compress said overlapping end portions and place contacting surface regions thereof in frictional engagement; motor means for moving one of said overlapping end portions relative to the other end portion to produce bodily sliding frictional movement between said contacting surface regions to effect interface melting there- I between; and means for stopping movement of said one end portion after a fixed time interval including, first and second switches mounted on said frame and connected to said motor means, operating :means mounted onsaid frame for movement relative to said switches, means for actuating said switches in response to movement of said operating means in a first direction, said actuating means including a first actuating member for said first switch movable from a first position to a second position by said operating means and a second actuating member for said second switch movable from a. first position to a second position by said operating means, said second-switch disabling said motor means in the first position of said second actuating member and said first switch disabling said motor means in the second position of said first actuating member, means for moving said first actuating member to said first position in response to movement of said operating means in a direction opposite to said first direction, and timer means for moving said second actuating member to said first position only after a fixed time interval has elapsed, whereby said first and second switches cooperate to retain said motor means energized for the duration of said fixed interval.

:8. A control system for strapping apparatus as set forth in claim 7 in which said one strap gripping member is a wheel, and wherein means is connected to said motor means for initially rotating said wheel in one direction to tension said loop and for oscillating said wheel after a predetermined amount of tension is drawn in said loop.

9. A control system for strapping apparatus as set forth in claim 7 including means for adjusting the duration of said time interval.

I 10. A control system for strapping apparatus as set forth in claim '7 wherein said motor means is an electric motor and said second switch is open in the first position of said second actuating member and retained closed for said fixed interval by said timer means and said first switch is closed in the first position of said first actuating member and is connected in a series circuit with said electric motor.

11. A control system for strapping apparatus as set forth in claim 10 in which said operating means is a manually operable push button, and where spring means is provided that biases said push button in said opposite direction.

12. A control system for strapping apparatus. as set forth'in claim 11 in which said first and second actuating members are levers for operating their respective switches, and wherein means is provided for simultaneously moving said levers in response to movement of said push button in said one direction.

References Cited UNITED STATES PATENTS 3,554,845 1/ 1971 Billett et al 15673 3,442,203 5/1969 Kobiella 156-73 3,442,733 5/1969 Vilcins 15673 3,442,734 5/ 1969 Ericsson 156-73 3,554,846 1/1971 Billett 15673 BENJAMIN A. BORCHELT, Primary Examiner I. V. DORAMUS, Assistant Examiner U.S. Cl. X.R. 156-73, 366, 367

v v UNI-TED ISTATESCCPATENT OFFICE Y CERTIFICATE-OF CORRECTION Patent a. '3 79';519 m 'aulys, 197

lnvntori f Rake rial" Frey! it is: Certified, that ierror. appears the i above-identified patent Y and. that vsaidaLetlnzlas Patent var-ehereby corrected as shown below:

Column l,' line 56,- "moveemnt"should be movement"---. 7 Column 2 line 18, -"thhe" should be the Y Column 3, line 21, "cylindrical" should be cylindrically Column 3, line 30 "blocker" should be block Column lines 2% and 295 after theword "base the word which appears half in line 2 and half in line 29 "number" should read member -V-.

Column line 7.1, after 'strap" add loop- L through the intermittent rotation of gripping wheel Column 5, line 1, ,"Pauwl"-. should be .Pawl Column 5, line 22, "16" should be 116 Column 6, line "sporfc";should be -vspot Signedband sealed this 2nd daylof January 1973.

(SEAL) Attest:

EDWARD M.FLETQHER,JR. ROBERT GOTTSCHALK Attes tlng Offlcer Commissioner of Patents FORM 7 I I USCOMM-DC r-oznr-J-cw