GB2038762A

GB2038762A - Package strapping machines

Info

Publication number: GB2038762A
Application number: GB7940934A
Authority: GB
Original assignee: Gerrard Industries Ltd
Current assignee: Gerrard Industries Ltd
Priority date: 1978-11-28
Filing date: 1979-11-27
Publication date: 1980-07-30

Abstract

A strapping machine has a package- compression platen (8, Figure 1, not shown) vertically movable with respect to a frame (5). The platen (8) can be raised and lowered by pinions (17) on a cross-shaft (16) and engaging racks (18) fixed to the frame (5). The cross-shaft (16) is driven by an electric motor (12) through a belt drive and a magnetic powder fluid clutch (14) at the input of a worm drive gear box (15) the output of which is connected to the cross-shaft (16). The magnetic clutch (14) has a field winding the current through which is adjustable to limit the torque at which the clutch will slip. This is set so that the platen applies the required compression to the package while the motor continues to run without overheating. <IMAGE>

Description

SPECIFICATION Improvements in package strapping machines This invention relates to strapping machines for binding packages, parcels or the like of the kind in which metal or plastics strapping is looped around a package by power means or by hand, the package is compressed while the strapping is tensioned and the ends of the loop are secured one to the other by the machine.

Most compression type strapping machines use compressed air to move the compression platen.

They use large quantities of compressed air which is costly to produce and is not universally available.

Compressed air devices are also noisy.

The present invention consists in a package strapping machine comprising a movable platen adapted to compress a package, means for converting rotary input motion to linear output motion, and an electric motor drivably connected to the input of the converting means through a torque limiting clutch, the output of the converting means being so connected as to move the platen towards and away from the package.

The torque-limiting clutch slips when the package is fully compressed and is arranged to allow the motor to run within its rated capacity. The torque limiting clutch may be a magnetic clutch, preferably a magnetic-powder fluid clutch, having a field winding to energise the magnetic clutch and connect its input and output. By adjusting the current through the winding of the magnetic clutch the torque at which the clutch will slip can be altered to suit the compression required, provided that this will not overload the motor.

The platen may be horizontal and move vertically towards and away from a support on which the package rests. The converting means then preferably includes a drive which is non-reversible in the sense that the weight of the platen or pressure theron will not turn the motor and allow the platen to fall or move under pressure. The non-reversible drive may be a worm drive or a lead screw and nut mechanism. The converting means may comprise a rack and pinion mechanism to convert rotary into linear motion or the lead screw and nut mechanism may perform this function.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings in which Figure 1 is a perspective view of a package strapping machine according to the invention.

Figure 2 is an end view and Figure 3 is a diagrammatic perspective view of part of the mechanism of the package strapping machine.

The machine illustrated is intended primarily for compressing and subsequently strapping a stack of "knock-down" but is illustrated in an alternative use for strapping large corrugated cardboard boxes. In the form illustrated it applies simultaneously two parallel loops of polypropylene or other suitable plastics strapping around eachrbox. The strapping machines includes a power-driven roller conveyor 1 which forms a support on which a box 2 rests while it is being strapped. Roller conveyor lengths 3 and 4 bring boxes to the strapping machine and take them away after strapping.

The machine has a rigid inverted U-shaped frame 5 straddling the conveyor 1 and having pillars 6 on which a carriage 7 is slidably mounted for vertical movement. The carriage includes a horizontal platen 8 which, when the cariage 7 is brought down, engages the top of the box 2 and then applies compression to it. On the top of the platen 8 on each side is a strapping head 9 (only one of which is visible in Figure 1) to feed strapping around a strap guide 11 to encircle the box with a loop of strapping which is tensioned and its overlapping ends joined together while the box is under compression.

To move the carriage 7 up and down and apply compression to the box a mechanism (better seen in Figure 3) is provided. An electric motor 12 is connected by a belt drive 13 to the input of a magnetic-powder fluid clutch 14. The output of the clutch 14 drives the worm of a worm drive gear box 15. The worm shaft is also provided with a brake 19.

The worm gear in the gearbox 15 drives a cross-shaft 16 at each end of which is a pinion 17 in mesh with a rack 18 rigid with the adjacent pillar 6. When the motor 12 rotates in one direction the pinions 17 turn in the direction to move the carriage downwards. As there is a rack 18 and pinion 17 at each end the carriage is kept level during this movement. When the platen 8 engages the top of the box 2 the motor 12 continues to run and the platen bears on the box with increasing pressure until the limiting torque of the magnetic clutch is reached. This limiting torque is determined by the electric current flowing through the winding (not shown) of the magnetic clutch 14 which is restricted to a value such that the clutch 14 slips before the electric motor 12 is overloaded. The electric motor continues to run within its rated capacity maintaining compression on the box.If consolidation of the box occurs after full compression is first reached, the motor is still running and will immediately move the platen down to maintain full compression. When full compression has been applied and the box consolidated the strapping heads 9 are actuated to apply loops of strapping around the box 2. To allow the box to be moved on after strapping, the motor 12 is reversed to lift the platen clear of the box 2. The worm drive in the gear box 15 has a reduction ratio of the order of 30:1 and is an irreversible drive so that the weight of the carriage 7 does not back drive the motor 12. The brake 19 is provided as an additional safeguard. It is applied when the motor 12 is de-energised.

1. A package strapping machine comprising a movable platen adapted to compress a package, means for converting rotary input motion to linear output motion, and an electric motor drivably connected to the input of the converting means through a torque limiting clutch, the output of the converting means being so connected as to move the platen towards and away from the package.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements in package strapping machines This invention relates to strapping machines for binding packages, parcels or the like of the kind in which metal or plastics strapping is looped around a package by power means or by hand, the package is compressed while the strapping is tensioned and the ends of the loop are secured one to the other by the machine. Most compression type strapping machines use compressed air to move the compression platen. They use large quantities of compressed air which is costly to produce and is not universally available. Compressed air devices are also noisy. The present invention consists in a package strapping machine comprising a movable platen adapted to compress a package, means for converting rotary input motion to linear output motion, and an electric motor drivably connected to the input of the converting means through a torque limiting clutch, the output of the converting means being so connected as to move the platen towards and away from the package. The torque-limiting clutch slips when the package is fully compressed and is arranged to allow the motor to run within its rated capacity. The torque limiting clutch may be a magnetic clutch, preferably a magnetic-powder fluid clutch, having a field winding to energise the magnetic clutch and connect its input and output. By adjusting the current through the winding of the magnetic clutch the torque at which the clutch will slip can be altered to suit the compression required, provided that this will not overload the motor. The platen may be horizontal and move vertically towards and away from a support on which the package rests. The converting means then preferably includes a drive which is non-reversible in the sense that the weight of the platen or pressure theron will not turn the motor and allow the platen to fall or move under pressure. The non-reversible drive may be a worm drive or a lead screw and nut mechanism. The converting means may comprise a rack and pinion mechanism to convert rotary into linear motion or the lead screw and nut mechanism may perform this function. An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings in which Figure 1 is a perspective view of a package strapping machine according to the invention. Figure 2 is an end view and Figure 3 is a diagrammatic perspective view of part of the mechanism of the package strapping machine. The machine illustrated is intended primarily for compressing and subsequently strapping a stack of "knock-down" but is illustrated in an alternative use for strapping large corrugated cardboard boxes. In the form illustrated it applies simultaneously two parallel loops of polypropylene or other suitable plastics strapping around eachrbox. The strapping machines includes a power-driven roller conveyor 1 which forms a support on which a box 2 rests while it is being strapped. Roller conveyor lengths 3 and 4 bring boxes to the strapping machine and take them away after strapping. The machine has a rigid inverted U-shaped frame 5 straddling the conveyor 1 and having pillars 6 on which a carriage 7 is slidably mounted for vertical movement. The carriage includes a horizontal platen 8 which, when the cariage 7 is brought down, engages the top of the box 2 and then applies compression to it. On the top of the platen 8 on each side is a strapping head 9 (only one of which is visible in Figure 1) to feed strapping around a strap guide 11 to encircle the box with a loop of strapping which is tensioned and its overlapping ends joined together while the box is under compression. To move the carriage 7 up and down and apply compression to the box a mechanism (better seen in Figure 3) is provided. An electric motor 12 is connected by a belt drive 13 to the input of a magnetic-powder fluid clutch 14. The output of the clutch 14 drives the worm of a worm drive gear box 15. The worm shaft is also provided with a brake 19. The worm gear in the gearbox 15 drives a cross-shaft 16 at each end of which is a pinion 17 in mesh with a rack 18 rigid with the adjacent pillar 6. When the motor 12 rotates in one direction the pinions 17 turn in the direction to move the carriage downwards. As there is a rack 18 and pinion 17 at each end the carriage is kept level during this movement. When the platen 8 engages the top of the box 2 the motor 12 continues to run and the platen bears on the box with increasing pressure until the limiting torque of the magnetic clutch is reached. This limiting torque is determined by the electric current flowing through the winding (not shown) of the magnetic clutch 14 which is restricted to a value such that the clutch 14 slips before the electric motor 12 is overloaded. The electric motor continues to run within its rated capacity maintaining compression on the box.If consolidation of the box occurs after full compression is first reached, the motor is still running and will immediately move the platen down to maintain full compression. When full compression has been applied and the box consolidated the strapping heads 9 are actuated to apply loops of strapping around the box 2. To allow the box to be moved on after strapping, the motor 12 is reversed to lift the platen clear of the box 2. The worm drive in the gear box 15 has a reduction ratio of the order of 30:1 and is an irreversible drive so that the weight of the carriage 7 does not back drive the motor 12. The brake 19 is provided as an additional safeguard. It is applied when the motor 12 is de-energised. CLAIMS

2. A package strapping machine according to Claim 1 wherein the torque limiting clutch is a magnetic clutch.

3. A package strapping machine according to Claim 2 wherein the torque limiting clutch is a magnetic-powerfluid clutch.

4. A package strapping machine according to Claim 2 or Claim 3 wherein the magnetic clutch has a field winding to energise the magnetic clutch and connect its input and output.

5. A package strapping machine according to Claim 4 wherein means is provided for adjusting the current through the winding so as to alter the torque at which the clutch will slip.

6. A package strapping machine according to any preceding claim wherein the platen is horizontal and moves vertically towards and away from a support on which the package rests.

7. A package strapping machine according to any preceding claim wherein the converting means includes a drive which is non-reversible in the sense that the weight of the platen or pressure thereon will not turn the motor and allow the platen to move.

8. A package strapping machine according to Claim 7 wherein the non-reversible drive is a worm drive or a lead screw and nut mechanism.

9. A package strapping machine according to any preceding claim wherein the converting means comprises a rack and pinion mechanism to convert rotary into linear motion.

10. A package strapping machine substantially as described herein with reference to and as illustrated by the accompanying drawings.