US3841213A

US3841213A - Strapping machine feed control

Info

Publication number: US3841213A
Application number: US00332449A
Authority: US
Inventors: G Goodley
Original assignee: FMC Corp
Current assignee: Illinois Tool Works Inc
Priority date: 1971-11-15
Filing date: 1973-02-14
Publication date: 1974-10-15
Anticipated expiration: 1991-10-15

Abstract

This machine straps a package with heat sealable plastic strapping. The strap is fed by motor driven geared feed and tension wheels around a yoke and against a stop. A loop of strap is developed which is sensed by a flag causing reversal of the motor, withdrawal of the loop and stopping of the motor. The operator then operates a valve to cause further reversal of the motor which tensions the strap around the package. An idler senses removal of slack in the drive chain from the motor when the strap is tight and this causes the motor to stop. The strap is gripped against a side-retractable anvil on opposite sides of a vertically moving platen and knive assembly, while straddling a retractable tongue. A heated blade replaces the tongue whereupon the platen squeezes the heated joint and cuts the strap. The anvil and tongue are withdrawn for removal of the strapped package. The platen, tongue, anvil and sealing blade are controlled by a set of cams on a linear actuator.

Description

United States Patent [191 Goodley [111 3,841,213 1 Oct. 15, 1974 STRA'PPING MACHINE FEED CONTROL [75] Inventor: George F. Goodley, Media, Pa.

[73] Assignee: FMC Corporation, San Jose, Calif.

[22] Filed: Feb. 14, 1973 [21] Appl. No.: 332,449

Related US. Application Data [62] Division of Scr. No. 198,862, Nov. 15, 1971, Pat. No.

FOREIGN PATENTS OR APPLICATIONS Great Britain 100/26 Primary ExaminerBilly J. Wilhite Attorney. Agent, or FirmC. E. Tripp [57] ABSTRACT This machine straps a package with heat sealable plastic strapping. The strap is fed by motor driven geared feed and tension wheels around a yoke and against a stop. A loop of strap is developed which is sensed by a flag causing reversal of the motor, withdrawal of the loop and stopping of the motor. The operator then operates a valve to cause further reversal of the motor which tensions the strap around the package. An idler senses removal of slack in the drive chain from the motor when the strap is tight and this causes the motor to stop. The strap is gripped against a sideretractable anvil on opposite sides of a vertically moving platen and knive assembly, while straddling a retractable tongue. A heated blade replaces the tongue whereupon the platen squeezes the heated joint and cuts the strap. The anvil and tongue are withdrawn for removal of the strapped package. The platen, tongue, anvil and sealing blade are controlled by a set of cams on a linear actuator.

7 Claims, 29 Drawing Figures Pmmigam '2 5m SHEET MOTOR,M

REAR

GRIPPER TENSION VALVES PLATEN/ PAIQHEB 1 5 1974 3, 841 ,2 l 3 sum :15 0F1T MA TENSION,3Q, 78

, FLAGJO 11 '10? 36a Q 04 O0. 1 220 52 FEED 203 \90 STRAP LIMIT \9 VALVE SV CAM LIMIT VALVE CL ANVILIE TONGUE,'Z4 n2 PAIENIEB um 1 51214 sum as or 17 iF'I l'7 s (see FIG. 23)

III... 641/.

STRAP LIMIT WITHDRAWS LOOP gggfi, 5V

If u

.55 P T I I; -1 El (SEE FIG. 24)

SV CLOSED PAIENIEB um I 51914 SHEU 11 [If 17 (SEE FIG. 25)

TENSION LIMIT VALVE v P 3 2 3 mm (SEE H626) TENSION LlMlT VALVE STOPS MOTOR STARTS CAM 1 PAIENIEU 0m 1 51914 SBiET "12 0F 17 FOOT VALVE AS) I F 3V4 il ,.p

4 o as T I P-\ v I H 34 v-a S TENSION WHEEL I F FLAG p, V 10 E5 v I M Mr 72 sv-z V STRAP LIMIT As g LvE As n q REvERsE REAR FRONT '2- v P-z B E GRIPPER (TENSION) V v ON-OFF L m sci MOToR 4 VALVE A 2 FWD. (FEED) A LINEAR P-4 ACTUATOR, no

' RETRACTED rm n CAMS 90 i A I r SOL. c. I i E V 4 v A R FH OPEN I VALVE H 2 A5 ll -'\/-2. E

I p PE'Z TENSION LIMIT A I 2-4 VALVE WE i ---6o H l T J' L "5v AC SOL.V-6

: z E-T"fic.)\

T I DR. PE-zmo) ;.2 j

TDR-Z 1, P .\f

AAA l COUNTER :E G 2 n I 1 HEAT SEAL \44 BLADE ELEMENT 4,

PAIENTED um I 51914 FOOT VALVE sum TENSION WHEEL I H 12 'IIIIE' 5 sv rH-P-z REAR FRONT GRIPPER GRIPPER M ON-OFF VALVE V4 32 3o MOTOR h A I LINEAR PE-I ACTUATOR, no

J SOL. IF ll AS II -F-fl l V'G i i I l I TENSION LIMIT l VALVE TV I I AS M 1 )3 I: 7;.- L; .i l

SOL.V-6

I TDR PE-zmc TOR-2W TI (.OLSNTER} T2 HEAT SEAL BLADE ELEMENT 143 IENIEDBUWQYI mm '.213

Sum 15 0F 17 (SEE FIG.I9)

TENSIONING C T m. W: T Mm A P 4 RRB M FG n ELLI 190 RL V-4 t. u

a SOL.V-6 I PE-I (NO) 5-2040.) TOR l OUNTER n5 v. M;

BLADE ELEMENT ACTUATORJTO REAR GRIPPER 1 'BQfi 3 I640.

LINEAR CAM LIMIT VALVE PE-Z I 60 I I HEAT SEAL FOOT VALVE FV OPENED VALVE STRAP LIMIT I: U' EJ I MI As I T\ FLAG IO ON- v ALvE Aifis/ /TENSION WHEEL PE-I cld SOL S -L- I TENSION LIMIT VALVE TV STRAPPING MACHINE FEED CONTROL REFERENCE TO RELATED APPLICATION This application is a division of Goodley, Ser. No. 198,862, filed Nov. 15, 1971 and assigned to the FMC Corporation and now Pat. No. 3,759,169 which issued Sept. 19, 1973.

Application Ser. No. 332,465, filed Feb. 14, 1973 is also a division of the aforesaid Goodley parent application and has claims directed to control of the strap feed mechanism.

1. Field of the Invention This invention relates to apparatus for strapping articles such as packages and more particularly to an improved strap feeder in a machine for strapping the packages with heat sealable plastic tape.

2. Description of Prior Art The apparatus of the present invention is an improvement over the U.S. patent to Billett et al. No. 3,269,300, Aug. 30, 1966. The improvements are so numerous and varied that they can only be made clear after an understanding based on the apparatus of the present invention.

The US. patent to Plattner, No. 3,590,729, July 6, 1971, shows a small diameter feed wheel geared to a large diameter tensioning wheel in a strapping machine with the strap wrapped less than 180 around the tensioning wheel and not wrapping around the feed wheel at all.

The US. Fat. to Rogers, No. 2,880,666, Apr. 7, 1959 shows a tying machine for cord wherein the cord passes between geared together tensioning wheels without wrapping around either wheel.

BRIEF DESCRIPTION OF THE MACHINE The mechanical features of the strapping machine of the present invention will be briefly summarized.

The strap transport of the present invention comprises a feed wheel and a tension geared together. The feed wheel feeds the strap beneath a front gripper, between a side retractable tongue and a platen, between a rear gripper and a side retractable anvil, up around a yoke, back between the front gripper and the anvil, over the tongue and against a stop on the anvil. In accordance with the present invention, a slight overfeed after the free end of the strap strikes the stop develops a loop, which closes the front gripper, reverses the feed motor toremove the overfeed loop and stops the feed motor. I

The operator now operates a control valve which resumes reversal of the feed to tension the strap around a package within the yoke. As claimed in the parent application, after the strap has been tensioned, a rear gripper closes automatically to maintain the tension, and a linear cam actuator starts advancing. As a result of actuator advance and retraction, the tongue is retracted, a heated sealing blade replaces the tongue between the end of the bight of the strap, a platen presses the joint, the blade is withdrawn, the platen is raised further to squeeze the heated joint, the strap is cut off at the joint, the anvil and tongue are retracted together, the platen is lowered and the strapped package can now be removed. The anvil and tongue are automatically returned to their initial positions andupon full retraction of the actuator the feed is automatically restarted and stopped in the manner described above.

SUMMARY OF THE INVENTION The strap transport comprises a transport wheel assembly comprising a feed wheel and a tensioning wheel geared together. The feed wheel feeds the strap beneath a front gripper, between a side retractable tongue and a platen, between a rear gripper and a side retractable anvil, up around a yoke, back between the front gripper and the anvil, over the tongue and against a stop on the anvil. A slight overfeed after the free end of the strap strikes the stop develops a loop, and a sensor at the tensioning wheel detects the loop formation. A control responsive to the sensor closes the front gripper, reverses the feed motor and hence the transport wheel assembly to remove the overfeed loop and stops the feed motor when the sensor responds to removal of the loop. The loop sensor comprises a movable flag overlying the wrapped portion of the tensioning wheel and the control reverses the motor upon partial displacement of the flag by the loop and stops the motor after motion of the flag toward its initial position.

The operator now operates a control valve which resumes reversal of the feed to tension the strap around a package within the yoke. An idler on the drive chain for the tensioning wheel senses removal of the slack in the chain when the strap has been pulled tightly around the package and the control then stops reversal of the motor and hence further tensioning of the strap. As

mentioned, after the strap has been tensioned, a rear gripper closes automatically to maintain the tension, the linear cam actuator starts advancing, and the ends of the tensioned strap are joined.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall view of the strapping machine embodying the invention.

FIG. 2 is a horizontal section of the machine taken on line 2 2 of FIG. 1 with parts broken away.

FIG. 2A is a schematic diagram showing the threading of strap through the machine.

FIG. 3 is a persp'ective of the feed and tensioning mechanism of the present invention.

FIG. 4 is a side view of the front of a machine with parts broken away.

FIG. 4A is a horizontal section of the strap tension valve operator taken along line 4A 4A of FIG. 4.

FIG. 5 is an enlarged section taken on line 5 of FIG. 2.

FIG. 6 is an enlarged section taken on line 6 6 of FIG. 2.

FIG. 7 is a view from the rear of the machine taken on line 7 7 of FIG. 2.

FIGS. 8 and 9 are perspectives showing the tongue and anvil operation.

FIG. 10 is a diagram showing threading of the strap through certain parts of the machine, as well as yoke details.

FIGS. ll, 12 and 13 are sections through the yoke taken as indicated on FIG. 10.

FIG. 14 is an exploded perspective showing feeding of the strap through the feed wheel casing structure.

FIG. 14A is a section through the casing structure of FIG. 14, taken as indicated on FIG. 7.

FIGS. 15 to 20 are operational schematic diagrams illustrating the salient mechanical features of the invention at various portions of a cycle.

FIGS. 21 to 26 are control diagrams showing how the operations of FIGS. are carried out in sequence.

DETAILED DESCRIPTION Mechanical Features Referring to FIG. 1, the strapping machine of the present invention includes a main body or housing 12 supported on legs 13 and mounting a flat upper table 14. The table is slotted at 16 to accommodate tensioning of a strap around a package (not shown) on the table. A retractable anvil 18 (see also FIG. 6) is at the center of the table 14. The strap S is fed from a tape reel in a manner to be described in detail presently around a yoke 20 that surrounds the package. After the feed, the strap is tensioned against the package, a heat sealed joint is made, the strap is cut and the strapped package removed.

The break away plan view of FIG. 2 shows additional mechanical features The anvil 18 is broken away in this view as is a retractable tongue 24 (best seen in FIG. 6) to expose a vertically reciprocating platen 26 that mounts a strap cutting knife 27 (see FIG. 5).

FIG. 2 also shows a heat sealing blade assembly indicated generally at 28 and illustrated in its retracted position. A side view of the blade appears in FIG. 6. Also appearing in FIG. 2 are a front gripper 30 and a rear gripper 32 for holding the ends and the bight of the strap respectively. These grippers are operated by bell cranks; as seen in FIG. 5.

A strap transport mechanism in the form of a pair of geared together feed and tension'wheels appears in FIG. 3. The strap enters from below and is wrapped partially around a feed wheel 34, pinched between that wheel and a tension wheel 36, wrapped around the tension wheel and fed on through the mechanism.

FIG. 2A (a simplified diagram) shows the path of a strap through the apparatus. The strap enters the feed wheel 34 from the tape reel (FIG. 1) passes between the feed and the

tension wheels

34, 36, wraps around the tension wheel 36, passes beneath the front gripper 30, passes beneath the tongue 24 and above the platen 26, passes between the rear gripper 32 and the anvil 18, is threaded through the yoke 20, traverses the entire yoke 20, passes between the front gripper 30 and the anvil 18, passes between the tongue 24 and the anvil l8, and abuts a stop 19 formed on the anvil.

Strap Transport Drive Referring principally to FIGS. 2, 3, 4 and 7, the transport drive of the present invention includes a reversible air motor M has a sprocket 40, driving a chain 42, and a sprocket 44 on the shaft 46 for the tension wheel 36. The other end of the shaft 46 mounts a gear 48 which is meshed with a gear 50 of the same pitch diameter on the shaft 52 for the feed wheel 34. The feed and

tension wheels

34,36 are covered with friction bands 34a and 36a formed of 90 Durometer polyurethane elastomer. In accordance with the invention of the aforesaid divisional application, Ser. No. 332,465, filed Feb. 14, 1973, the strap S is gripped between the

wheels

34,36, but it wraps around the feed wheel 34 for something over 90 and around the tension wheel 36 for something over 180. The wrap around the feed wheel 34 is adequate to feed the strap through the path shown in FIG. 2A and the wrap around the tension wheel 36 is adequate to tightly tension the strap around the package before sealing the joint in the strap.

In accordance with the invention of this divisional application, in order to operate a tension limit valve TV, for stopping the tensioning of the strap around the package, and to initiate other functions to be described presently, an idler sprocket 60 (FIGS. 3,4 and 4A) is mounted on an arm 62 pivoted to the frame at 63 and connected to a link 64. A compression spring 66 that is compressed between a nut on the link 64 and a frame element 67 (FIGS. 4- and 4A) is used for taking up the slack in the chain 42. The idler link 64 also mounts a tab 65 (FIGS. 4 and 4A) which is held against the operating button of the tension limit air valve TV, the construction being that the valve TV is closed when there is a slack in the reach 42a of the chain 42 engaged by the idler sprocket 60. This slack occurs when the motor M is driving the wheels in the feed direction illustrated by the solid arrow on the wheel 34 in FIG. 3. The slack tends to be removed from the idler side 42a of the chain 42 when the motor M is reversed to drive the tension wheel 36 in the tension direction indicated on that wheel by the dashed arrow in FIG. 3. When the strap is tight around the package, the side 42a of the chain becomes taught, swinging out the idler arm 62, and pulling the tab 65 away from the tension limit valve TV. This opens the air valve for stopping the motor M and for other purposes to be described presently. Opening of the valve TV only takes place upon the generation of a predetermined amount of torque required to drive the tensioning wheel 36, which torque is sufficient to adequately tension the strap around the article. Hence the action just described does not stop the motor M from drive in the tensioning direction until the package is tightly strapped.

Overrun Flag As seen in FIG. 7, and in accordance with the present invention, an overrun flag 70 is provided at the tension wheel 36 for sensing a loop in the strap that develops during the feeding operation and causing the loop to be removed before the strap is tensioned about an article.

The flag 70 is pivoted at 70a to a plate (shown in perspective in FIG. 14) and has a loop sensing surface 70b that is contoured to fit the tension wheel 36. The flag 70 has a cam surface 70c for operating a cam follower 71. The follower 71 is pivoted to the plate 75 at 71a and has a follower roller 71b for depression by the 9 m SIH7ER1QJQZQ Ih l w 71 has a cam surface 710 for depressing the operating arm 72 of a strap limit valve SV, which occurs when the flag 70 is displaced by development of a loop as will be explained in detail presently.

FIG. 14 shows additional details of the housing and guide mechanisms associated with the transport wheels. The strap enters between the guide rollers 69 (see also FIGS. 4 and 7), passes between

vertical guides

72,73 and wraps something over around the feed wheel 34, the position only of which is illustrated in FIG. 14. The strap S then passes between the nip of the

wheels

34 and 36 wrapping more than around the tension wheel 36 (also not shown) passing a pocket 74 for the flag 70, just described. The strap leaves the tension wheel 36 and passes over the top of the upper surface 76 of a plate 77, passes beneath the front gripper 30, passes beneath the tongue 24 and above the platen 26, passes between the rear gripper 32 and the anvil 18 and on through the yoke 20 (not shown). After emerging from the yoke, the strap rides over the upper sur-

Claims

1. Article strapping apparatus of the type wherein reversibLe, power driven strap transport wheel means feeds the strap through an article receiving yoke and against a stop, the end of the strap is gripped, the transport wheel means is reversed to tension the strap; means for accommodating development of a loop of strap at said transport wheel means after the end of the strap has been stopped, means for sensing the devlopment of said loop, and control means responsive to said sensing means for reversing said transport wheel means from the strap feeding direction to the strap tensioning direction, the improvement wherein said control means includes means for stopping rotation of said transport wheel means when said sensing means responds to removal of said loop, and means for independently re-starting motion of said transport wheel means in the strap tensioning direction for completion of the tensioning operation.

2. The apparatus of claim 1, wherein said strap transport wheel means comprises a feed wheel followed by a tensioning wheel with the strap partially wrapped around the latter for directing the strap to said stop, said loop sensing means comprising a movable flag overlying the strap adjacent said tensioning wheel; the improvement wherein said flag is curved to conform to the majority of the wrapped portion of said tensioning wheel, said control means reversing the wheel means drive upon partial displacement of said flag by the loop, said control means stopping reversal of said transport wheel means after motion of the flag back towards its initial position.

3. The apparatus of claim 2, wherein said control means does not stop the drive reversal until the flag reaches its initial, pre-loop forming position.

4. The apparatus of claim 2, wherein said control means includes a circuit for conditioning the reverse drive for resumption thereof under manual control for subsequent tightening of the strap about an article within said yoke.

5. The apparatus of claim 1, comprising means for sensing the tension of the strap as it is tightened around the article, and means for stopping the drive to said transport wheel means upon development of a predetermined strap tension.

6. Article strapping apparatus of the type wherein reversible, power driven strap transport wheel means feeds the strap through an article receiving yoke, the end of the strap is gripped, and the transport wheel means is reversed to tension the strap against an article, the bight of the strap is gripped, and the bight and end of the strap are heat sealed, means for sensing the torque required to turn the transport wheel means during final tensioning of the strap, and control means responsive to said torque sensing means for stopping the tensioning drive to the transport wheel means; the improvement wherein said transport wheel means comprises feed and tensioning wheels geared together, a reversible motor, a drive wheel for the motor, a driven wheel for said tensioning wheel, an endless tension member connecting said drive and driven wheels, said torque sensing means comprising idler means responsive to removal of the slack in said endless member when said feed and tensioning wheels are driven in their strap tensioning direction, and means for connecting said idler means to said control means.

7. The apparatus of claim 6, wherein said reversible motor is an air motor, said control means including directional valve means for determining the direction of rotation of said motor, said means for connecting said idler means to said control means comprising a tension limit valve connected to said directional valve means.