An automatic strapping apparatus is disclosed which forms a small primary loop from strap; expands the primary loop to a larger predetermined diameter loop which can be placed about a package to be strapped; and tensions, friction fuses, and severs the strap. The small primary strap loop is formed by feeding a free end of a length of strap into a circular cup through a slot in the cup sidewall so that the free end is guided by the inner periphery of the cup to form a loop with the strap free end overlapping a portion of the loop. The cup is moveable from an upper position around the formed primary loop to a position out of contact with, and below, the loop. A cylindrical gripper is provided inside the loop and a smooth-surfaced anvil is provided on the exterior of the loop for engaging the overlapped portion of the loop therebetween so that the strap free end is restrained by the gripper while the overlapped portion of the loop can be continued to be fed to expand the loop to a larger predetermined diameter. The strap free end remains restrained by the gripper as the strap is tensioned to tighten the loop about the package. The gripper is then rotatably oscillated at a high frequency to cause the strap free end to slide against the overlapped portion of the loop thereby generating heat and fusing the strap free end to the overlapped portion of the strap loop. A cutter is provided to sever the tightened and fused loop from the standing length of strap.
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1. An In an apparatus for forming, tensioning, and securing a strap loop about a package, said apparatus comprising:
means for feeding guiding a length of strap in a path to form a primary strap loop with a portion of the strap loop overlapped by the free end of the length of strap; means for restraining said free end of the strap from movement while feeding the standing length of the strap to expand the loop to a predetermined size; means for tensioning the strap to tighten the loop about said package; and means for joining said free end of the strap and an adjacent overlapped portion of the loop; the improvement in the apparatus characterized in that said means for guiding the strap to form a primary loop is free of guides for acting on the inside of the loop but includes an arcuate guide member having an inner surface for acting on the outside of the loop for guiding only one surface of the strap along the inner surface of the guide member to form said primary strap loop, said guide member defining a slot and being positionable to receive said length of a strap through said slot, said slot being open to one edge of said guide member; the improvement further characterized in that said guide member is movable relative to said restraining means; and the improvement further characterized in that said apparatus includes means for moving said guide member relative to said restraining means between a first position wherein said primary strap loop is formed and a second position spaced away from said first position to allow said primary strap loop to be expanded to said predetermined size out of contact with said guide member.
22. In an apparatus for forming, tensioning, and securing a thermoplastic strap in a loop about an article; means for feeding a length of strap to form a primary strap loop; means for expanding the loop to a predetermined size; means for tensioning the loop about the article; and means for connecting the overlapping strap loop ends; the improvement that includes:
a weld head having a peripheral gripping surface adapted for contacting a side of the strap; a generally smooth-surfaced anvil located adjacent said weld head; means for moving said anvil away from said weld head to permit passage of the free end of said strap past said anvil and for moving said anvil towards said weld head to engage portions of the strap therebetween with a predetermined force; an arcuate guide member substantially surrounding said weld head, said guide member having slot means for accommodating the movement of said anvil towards said weld head and for accommodating the passage of said length of strap between said anvil and said weld head from the exterior to the interior of said guide member when said length of strap is fed into said guide member to form a primary strap loop with a portion of the strap loop overlapped by the free end of the strap, said guide member being movable between a first position for receiving said strap while forming said primary strap loop and a second position spaced from the first position wherein said primary strap loop can be expanded without interference to a larger loop of predetermined size when said free end of the strap is pressed between said weld head gripping surface and an adjacent overlapped portion of the loop by said smooth-surfaced anvil; and means connected to said weld head for oscillating said weld head at a frequency sufficiently high to fuse said free end of the strap to an
adjacent overlapped portion of the loop. 2. The apparatus in accordance with
3. The apparatus in accordance with
4. The apparatus in accordance with
out of contact with said band member. 5. The apparatus in accordance with claim 1 in which said means for restraining said free end of the strap comprises a rough-surfaced member adapted for bearing against a side of said free end to engage said free end between said rough-surfaced member and an adjacent overlapped portion of the loop while the standing length of the strap is fed to expand the loop. 6. An apparatus for forming, tensioning, and securing a strap loop about a package, said apparatus comprising:
a frame having means for supporting a length of strap; means for feeding a length of strap; guide means for receiving a free end of said length of strap and for guiding said free end in a path to form a primary strap loop with a portion of the strap loop overlapped by said free end; means for restraining said free end of the strap from movement while feeding the standing length of the strap to expand the loop to a predetermined size; means for tensioning the strap to tighten the loop about said package; and means for joining said free end of the strap and an adjacent overlapped
portion of the loop. 7. The apparatus in accordance with
8. The apparatus in accordance with
9. The apparatus in accordance with
said strap and drive means for rotating said traction wheel. 10. The apparatus in accordance with claim 6 in which said strap is one of non-metallic and 1 adapted for use with strap that is either a thermoplastic material or a metallic material with a non-metallic coating and of thermoplastic material; in which said means for forming a connection comprises for restraining and said means for joining include at least a rough-surfaced gripping member rotatably mounted on said frame, an anvil, and means for effecting relative movement between said anvil and said gripping member to compress press said strap free end and an adjacent overlapped portion of the loop therebetween and to place said strap free end and the adjacent overlapped portion of the loop in frictional engagement,; and in which said means for joining further includes means for oscillating said gripping member to produce bodily sliding frictional movement of said strap free end against the adjacent overlapped portion of the loop to effect interface melting therebetween, whereby said strap free end is fused to the adjacent overlapped portion of the loop. 11. The apparatus in accordance with
therebetween. 12. The apparatus in accordance with claim 11 including 10 in which said means for effecting relative movement includes means for moving said smooth-surfaced member anvil to bear against a side of an adjacent portion of the loop in contact with said strap free end whereby a side of said strap free end is pressed against said rough-surface gripping member. 13. The apparatus in accordance with claim 11 10 further comprising strap edge locator means for guiding at least one of the two edges of a portion of the length of strap as the strap is fed. 14. The apparatus in accordance with claim 13 in which said strap edge locator means comprises a plate mounted adjacent said smooth-surface member anvil and substantially parallel to the plane of said primary strap loop. 15. The apparatus in accordance with claim 13 in which said strap edge locator means comprises a flange on one end of said rough-surfaced gripping member. 16. An apparatus for forming, tensioning, and securing one of a non-metal strap and a metal strap with a non-metal coating in a loop about a package, said apparatus comprising: a frame having a package support surface; means for supporting a length of strap on edge in a strap transport zone below said package support surface; a motor driven traction wheel and adjacent idler wheel located in said strap transport zone and adapted for engaging said length of strap therebetween for feeding said length of strap in one direction for forming a loop and for drawing said length of strap in the reverse direction to tension said loop; a cylindrical weld head located in said strap transport zone with the axis parallel to the sides of the strap in said zone and having a peripheral gripping surface adapted for contacting a side of said strap; a smooth-surfaced anvil member located adjacent said weld head in said strap transport zone; means for moving said anvil in said zone towards said weld head to engage portions of the strap therebetween; a hollow cylindrical guide in said strap transport zone surrounding said weld head and having slot means for accommodating said movement of said anvil member towards said weld head and for accommodating the passage of said length of strap between said anvil and said weld head from the exterior to the interior of said guide when said length of strap is fed into said guide to form a primary strap loop with a portion of the strap loop overlapped by the free end of the strap, said guide being moveable between a first position in alignment with said strap transport zone and a second position, below the first position, wherein said primary strap loop can be expanded to a larger loop of predetermined diameter when said free end of the strap is pressed between said weld head gripping surface and an adjacent overlapped portion of the loop by said smooth-surfaced anvil; means connected to said cylindrical weld head for oscillating the head at a frequency sufficiently high to fuse said free end of the strap to an adjacent overlapped portion of the loop after the larger strap loop has been placed around said package and tensioned; and cutter means for severing the standing portion of the length of strap from the tightened tensioned and fused loop. 17. The apparatus in accordance with claim 16 including control means responsive to the rotation of said traction wheel for moving said cylindrical guide from said first position to said second position after formation of said primary strap loop in said guide. 18. The apparatus in accordance with claim 17 in which said traction wheel is secured to a shaft and in which said control means includes a clutch member engageable with said shaft. The apparatus in accordance with claim 16 in which said means for moving said anvil includes an air operated piston and cylinder actuator. . The apparatus in accordance with claim 18 including automatically actuated valve means for variably pressurizing said piston and cylinder actuator to bias said anvil member with variable force against said weld head with portions of strap impressed therebetween. 21. An apparatus for forming, tensioning, and securing a strap loop about a package, said apparatus comprising:
means for forming a primary strap loop with a portion of the strap loop overlapped by the free end of the length of strap; means for restraining said free end of the strap from movement while feeding the standing length of the strap to expand the loop to a predetermined size; means for tensioning the strap to tighten the loop about said package; and means for joining said free end of the strap and an adjacent overlapped portion of the loop.
23. The apparatus in accordance with
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The cutter blade 102 is moved through a linkage by a pneumatic cylinder actuator 114. As illustrated in FIG. 6, link 108 is pivotally mounted about shaft 110 and is pivotally connected to arm 112 on one end and to cutter slide block 106 104 on the other end. Arm 112 is connected to the cutter air cylinder actuator 114 through a conventional cylinder piston rod (not shown). Pressurization of the cylinder actuator 114 forces the cylinder piston rod and arm 112 toward the cylinder actuator to pivot link 108 counterclockwise (as viewed in FIG. 6) about shaft 110 thereby moving the cutter blade 102 forward to sever the strap. The cylinder actuator is equipped with an internal spring to return the piston rod to the extended position (and hence the cutter blade 102 to the retracted position) upon release of cylinder air pressure.
After the strap has been severed, the anvil slide 46 is moved away from the weld head 52 to retract the anvil 44 and the slide cover 62. With the anvil 44 retracted, the fused portion of the strap loop adjacent the weld head 52 is relieved from its 90° twist configuration with respect to the balance of the loop and lies flat along the bottom surface of the package. Since the slide cover 62 is also retracted, the tensioned strap loop tightens further, under influence of its elasticity, to fit tight around a portion of the surface of the package that was previously in contact with the slide cover 62. The strapped package can then be removed from the apparatus.
As previously described, the movement of cutter blade 102 and anvil slide 46 is effected by pneumatic cylinder actuators 114 and 120, respectively. The actuators are controlled by a pneumatic actuation system illustrated schematically in FIG. 13.
The system is comprised of a supply manifold 124 supplying 90 psi air to three pressure regulating valves 126, 128, and 130 downstream of which are three-way electrically operated solenoid valves 132, 134, and 136, respectively. The solenoid valves admit air to a distribution manifold 137 for supplying the cylinder actuators 114 and 120. A check valve 138 prevents flow from solenoid valves 132 and 134 from pressurizing the cutter cylinder actuator 114. Cylinder actuator 114 can thus be pressurized only from solenoid valve 136 through a flow control valve 139.
Pressure regulating valves 126, 128, and 130 are set to control pressure to relative "low", "medium", and "high" pressure levels, respectively, for purposes to be explained hereinafter. The solenoid valves 132, 134, and 136 each have three ports (labeled A, B, and C in FIG. 13). Exhaust port C is plugged in valves 134 and 136, but is unplugged to exhaust to atmosphere in valve 132. In the de-energized state, the solenoid valves are set to pass flow through ports B and C (except that port C is plugged on valves 134 and 136) and in the energized state the valves pass flow through ports A and B.
The actuation of the anvil cylinder actuator 120 will now be considered. When the primary strap loop is first formed in cup 28, the anvil 44 is moved forward to contact abutment surface 56 as illustrated in FIG. 7. With reference now to FIG. 13 also, it can be seen that movement of anvil 44 to this position is accomplished by actuating air solenoid valve 132 to open ports A and B to allow a regulated low air pressure from pressure regulating valve 126 to act upon the piston in cylinder actuator 120 and force anvil 44 against the cup abutment surface 56 with about 2 pounds of force. The 2 pounds of force is a nominal amount that is used to insure that the anvil 44 is abutting the cup 28 to provide proper alignment and guiding of the strap free end 38 as it is fed forward into aperture 34 and between polyurethane pad 48 and weld head 52.
After the primary strap loop has been formed in cup 28, cup 28 is lowered to below the surface of shoulder 26. As cup 28 is being lowered, cup abutment surface 56 slides vertically downward along the front of anvil 44. As soon as cup 28 has cleared the bottom of anvil 44, anvil 44 is urged forward against the strap and weld head 52 by the 2 pounds of force that is still maintained by the anvil air cylinder actuator 120. The loop is expanded to a larger diameter with the anvil 44 maintaining the 2 pounds of force on the strap. Next, after the expanded loop has been located around the package, a higher pressure must be applied to the overlapped portions to prevent the strap free end 38 from being drawn out of engagement with weld head 52, during the tensioning step. Thus, at this point, solenoid valve 134 is energized to open port A to provide medium pressure air to anvil air cylinder actuator 120 to cause the anvil 44 to exert about 30 to 40 pounds on the strap against the weld head 52. After the tensioning process has been completed, the solenoid valve 134 is de-energized to close port A. However, since port C is plugged, the cylinder actuator 120 remains pressurized and the anvil 44 remains pressed against the strap loop.
During the next joint-forming step, the strap must be held with even more force against the weld head 52 as the weld head 52 is oscillated at high frequency to form the friction-fused joint. To accomplish this, the solenoid valve 136 is energized to open port A to admit higher pressure air to anvil air cylinder actuator 120 to force anvil 44 against the strap and weld head 52 with about 100 pounds of force.
The cutter air cylinder actuator 114 is supplied with high pressure air from high pressure regulator 130 only through solenoid air valve 136 since check valve 138 prevents air from low and medium pressure regulators 126 and 128 from flowing into the cutter air cylinder actuator 114. Note that solenoid air valve 136 admits air to both the anvil air cylinder actuator 120 and the cutter air cylinder actuator 114 simultaneously. However, the action of the cutter air cylinder actuator 114 is delayed about one-half second while the high pressure air is admitted to the anvil air cylinder actuator 120 to hold the strap until completion of the friction-fusion welding. After the weld is completed, the cutter air cylinder actuator 114 is permitted to move the cutter blade to sever the strap. This is accomplished by the flow control valve 139 in the air supply line to cutter air cylinder actuator 114. The flow control valve 139 provides a controlled slow rate of pressurization and, acting through the cutter air cylinder actuator 114, moves the cutter blade 102 forward so that it reaches the strap length 36 (FIG. 12) just as the weld sequence is terminated. After the cutter blade 102 has severed the strap and reached the full extent of its travel, solenoid valve 136 is de-energized to close port B and solenoid valve 132 is de-energized to close port A and open port C to exhaust air pressure from both the cutter air cylinder actuator 114 and the anvil air cylinder actuator 120. The internal spring return mechanisms in each of the cylinders causes anvil 44 and cutter blade 102 to return to the fully retracted positions.
In order that the strap loop be properly formed, expanded, tensioned, friction-fused, and severed, the sequence of operation must be appropriately controlled. The operation of the apparatus 20 of the present invention can be made to operate automatically and rapidly by means of a suitable electrical control system. A suitable control system is illustrated in the simplified control block diagram of FIG. 14. In the diagram, the necessary interlocking latching relays and switches are omitted. It is assumed that apparatus is at the beginning of a strapping cycle in a power-on ready mode with the strap threaded in the guideways 42 up to the cutter block 106. The cup 28 is in the raised position by the energized solenoid actuator 66. The solenoid valve 132 is energized to pressurize the anvil cylinder actuator 120 to move the anvil 44 against the cup 28 (as shown in FIG. 7) with about 2 pounds of force. The field coils of the traction wheel motor 76 are energized for motor operation in the direction to feed the strap into the cup 28.
A strap feed switch 144 is provided and is preferably a foot-operated momentary contact type. When depressed, the feed switch 144 energizes the armature of the traction wheel motor 76 to turn the motor in the direction to feed the strap. The feed switch 144 also actuates the incremental control unit 74 associated with the traction wheel shaft 72 to lower the cup 28 after the primary strap loop is formed. As the cup 28 is lowered, the motor is still rotating so that the strap continues feeding. As the cup reaches the lower position beneath the surface of the shoulder 26, the anvil 44 is urged against the strap to force the strap against the weld head 52 under the influence of the low pressure air being supplied to anvil cylinder actuator through the solenoid valve 132. The anvil 44 bears against the strap and the weld head 52 with about 2 pounds of force as the loop continues to expand. Release of the feed switch 144 stops the motor 76 and stops the strap feed. Repressing of the feed switch 144 continues the feeding of strap and expansion of the loop.
When the loop is of sufficient size, the operator releases the feed switch 144. Alternatively, if identically sized packages are being strapped on a production line basis, the feeding of the strap and expansion of the loop could be controlled by a timer. In any case, the operator next lifts the loop and places it over the package as illustrated in FIG. 4.
A strap tension switch 148 is provided to reverse the motor 76 to tension the loop about the package. The tension switch 148 is preferably a foot-operated momentary contact type. The tension switch 148 is also connected to actuate the solenoid valve 134 to admit medium pressure air to the anvil air cylinder actuator 120 to move the anvil 44 against the strap loop and the weld head 52 with about 40 pounds of force. This holds the strap free end 38 against the weld head 52 while the overlapping portion of the strap loop is allowed to slide against the anvil 44 as the loop is tensioned.
When the predetermined strap loop tension level (about 10 to 15 pounds on small packages) is reached, the tension sensing switch 100 is actuated to stop the motor 76 and reverse the motor field coils for the next cycle operation in the feed direction. The tension sensing switch 100 also de-energizes the medium pressure solenoid valve 134 and energizes the solenoid valve 136 supplying the high pressure to the anvil cylinder actuator 120 and the cutter air cylinder actuator 114. This causes (1) the anvil actuator 120 to provide the high clamping force (approximately 100 pounds) required to hold the overlapped strap portion of the loop while the friction-fusion joint is made and (2) the cutter actuator 114 to move the cutter blade 102 to sever the strap after conclusion of the joint weld. The tension-sensing switch also actuates the weld motor 80 and the timer 152 which de-energizes the weld motor after the weld has been completed (about 3/4 of a second to 1 second). the timer 152 also de-energizes the solenoid valve 136 thereby blocking the high pressure air supply and de-energizes the solenoid valve 132 to exhaust to atmosphere so that both the cutter air cylinder actuator 114 and the anvil air cylinder actuator 120 are returned by their internal spring mechanisms to the positions wherein the cutter blade 120 102 and the anvil 44 are in the fully retracted positions.
To set the apparatus for the next cycle, timer 152 also energizes two additional timers, 154 and 156. Upon timing out, timer 154 energizes solenoid actuator 66 to raise cup 28 and timer 156 energizes solenoid valve 132 to move the anvil 44 forward to abut the cup 28. Timer 154 is set to provide a certain time period for removal of the strapped package before raising the cup 28. Timer 156 is set to provide a period longer than timer 154 to assure that the cup 28 will be in the raised position when the anvil 44 is moved forward.
While preferred construction features of the invention are embodied in the structure illustrated herein, it is to be understood that the changes and variations may be made by those skilled in the art without parting from the spirit and scope of the appended claims.
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| May 03 1982 | Signode Corporation | (assignment on the face of the patent) | / |
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