GB2334769A

GB2334769A - Manual strapping tool

Info

Publication number: GB2334769A
Application number: GB9803849A
Authority: GB
Inventors: Tony Sandland
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-02-25
Filing date: 1998-02-25
Publication date: 1999-09-01
Also published as: GB9803849D0

Abstract

The tool, for pre-tensioning and securing two ends of strapping material together with a seal, comprises a housing 2; a baseplate 3 coupled to said housing; a sealer block 5 in sliding engagement with the housing for compressing seals between the sealer block and the baseplate; and a drive mechanism for reciprocating the sealer block in a direction substantially perpendicular to the baseplate, between a compression position and a release position. The drive mechanism includes a cam shaft 30 passing through said housing 2, a handle 6 in driving engagement with said cam shaft; a cam 20 axially displaced from said handle along said cam shaft, and a collar 23 substantially surrounding the circumferential surface of said cam. The cam 20 is rotatable in the collar 23 which is in driving engagement with the sealer block 5. The handle 6 has an adjustable stop pin to prevent over-pressure on a seal and contacts a spring-biassed plunger in the release direction to allow for gap increase for larger sized seals when needed. An associated tension lever 7 operates a ratchet-controlled capstan 18 to tension strapping in one direction, and operates a strapping cutter mechanism 12, 13 and acts on a strapping gripper foot to release strapping, in the other direction.

Description

STRAPPING TOOL The present invention relates to strapping tools, and in particular to hand tools suitable for tensioning and sealing together overlapping ends of strapping material placed around an object.

Strapping material is widely available as steel, polyester or polypropylene bands, but in the context of the present application, generally may be formed from any suitable material such as metal or plastics materials. The use of such strapping material is widespread for the purposes of securing in a closed condition packages, cartons and crates etc and also for securing such items to pallets and the like.

Typically, the strapping material is passed around a package and the ends of the strapping material are brought into overlapping relationship with one another, tensioned, and sealed together using a metal seal which is crimped around the strapping material.

Although many types of automated or semi-automated equipment exist for strapping packages, these are generally complex and expensive and therefore not generally suitable for small scale use. Although less complex hand tools do exist, it has been found that many of these have complex gearing, drive and ratchet mechanisms which are expensive and difficult to repair and are vulnerable to damage in a typical warehouse environment.

There is a widespread need for a simple, inexpensive, robust hand tool which can provide the necessary functionality for tensioning and sealing strapping material, which tool is easy to repair and designed to limit susceptibility to damage caused by over-aggressive and/or careless use.

It is an object of the present invention to provide a strapping tool which is simple, low cost and robust.

According to one aspect, the present invention provides a manual strapping tool for securing two ends of strapping material together with a seal, comprising: a housing; a baseplate coupled to said housing; a sealer block, in sliding engagement with the housing, for compressing seals between the sealer block and the baseplate; a drive mechanism for reciprocating the sealer block in a direction substantially perpendicular to the baseplate, between a compression position and a release position, the drive mechanism including a cam shaft passing through said housing; a handle in driving engagement with said cam shaft; a cam, axially displaced from said handle along said cam shaft; a collar, substantially surrounding the circumferential surface of said cam, said cam being rotatable in the collar, said collar being in driving engagement with said sealer block.

Embodiments of the present invention will now be described with reference to the accompanying drawings in which: Figure 1 shows a perspective view of a strapping tool according to a presently preferred embodiment of the invention; Figure 2 shows a schematic front view of the tool of figure 1; Figure 3 shows a schematic cross-sectional end view of the tool of figure 1, on the line A-A of figure 2; Figure 4 shows a schematic partial rear view of the tool of figure 1, showing detail of a preferred sealer handle stop and strap thickness adjustment mechanism; Figure 5 shows a schematic partial rear view of the tool of figure 1, in position to receive a seal; Figure 6 shows a schematic rear view of the tool of figure 1 with part cut away to reveal detail of the strap tensioning mechanism; Figure 7 shows a schematic front view of the tool of figure 1 with part cut away to reveal detail of the cutter mechanism; and Figure 8 shows a schematic exploded perspective view of components of the cutter mechanism of figure 7.

With reference to figure 1, there is shown a perspective view of the presently preferred embodiment of a manual strapping tool 1.

The tool 1 comprises a housing 2 including a reinforced side wall 15 for the passage of a cam shaft 30 therethrough (shown in figure 3), a base plate 3 which provides a working surface 4 against which a sealer block 5 may compress a seal (not shown). A sealer handle 6 is coupled to the cam shaft 30 at the rear of the housing 2 and the cam shaft is coupled to the sealer block 5 at the front of the housing 2 in a manner to be described later. A tension handle 7 is coupled to drive a strap capstan 8 for tensioning a strap prior to sealing. A strap gripper foot 9, coupled to a gripper foot release lever, is biassed by a coil spring 67 (shown in figures 2 and 6) against the base plate 3 to grip strapping material during the strapping operation and is releasable by the release lever 10 which causes the strap gripper foot 9 to lift away from the base plate 3 when pressed. A spring 11 maintains the strap gripper foot approximately parallel to the base plate when the foot is lifted away from the base plate, thus preventing an edge of the gripper foot from jamming against the base plate.

A grip handle 16 is provided for the user to manipulate the tool 1. A fixed cutter blade 12 and a rotating cutter blade 13 operate in conjunction with one another to provide a strap cutting facility. The sealer handle 6 also includes an adjustable stop member 14 extending laterally from one end thereof.

Figure 2 shows a front view of the strapping tool 1 with the sealer block 5 sectioned to reveal detail therein. Figure 3 shows a sectional side view of the strapping tool 1, on line A-A of figure 2. With reference to figures 2 and 3, the sealer block 5 is coupled to the cam shaft 30 (shown in dotted outline in figure 2) in the following manner. The cam shaft 30 extends through the housing 2 by way of bearings 32, 33 and includes a square section first end 31 to which the sealer handle 6 is fixed using a locking screw or similar (not shown). At the other end of the cam shaft 30 is a cam 20 which in the preferred embodiment comprises a circular disc having its centre line 22 displaced from the axis 21 of the cam shaft 30. The cam 20 is free to rotate within a collar 23 which extends around the cam 20, separated therefrom by a bearing 34. A cover plate 35 is secured to the cam 20 by screw 36, thereby concealing the cam 20 and bearing 34.

The collar 23 includes a connecting rod portion 24, the distal end of which is connected to the sealer block 5 by a pivot pin 26 and bearing 29. The sealer block 5 is maintained in sliding engagement with the housing 2 by a plurality of bolts, eg. 37, 38, passing through a retaining plate 39 and through respective vertical slots in the housing 2. The sealer block is therefore free to rise and fall respectively away from and towards the base plate according to the rotating action of the cam shaft 30.

Throughout the present specification, the lower positions of the sealer block 5 (ie. when in close proximity to the working surface 4 of the base plate 3) will be described as compressed or closed positions, and the upper positions of the sealer block (ie. when relatively remote from the working surface 4 of the base plate 3) will be described as release or open positions. It will be understood that the compressed position will correspond to the approximate thickness of a compressed seal or clip 40 together with the thickness of a compressed pair of straps therein and thus is variable according to circumstances. It will further be understood that a normal open or release position will correspond to a distance of separation of the sealer block 5 and working surface 4 which is sufficient to insert and release seals 40 and strapping material, and is thus also variable according to seals and strapping material being used.

With further reference to figure 3, the sealer block 5 may include a lower working surface 27 which is suitably profiled to operate, in conjunction with base plate working surface 4, to compress and close a seal or clip 40 which is installed therebetween and which surrounds strapping material (not shown). Various styles of sealer block and seal or clip 40 are well known in the art.

With further reference to figure 2, the sealer block 5 may include an internal, spring loaded pin 28 which projects downwardly from the working surface 27 to facilitate retention of a seal 40 when pressed into place prior to a strap tensioning and sealing operation. This spring loaded pin prevents the seal 40 from sliding towards the cutter mechanism (ie. fixed and rotating cutter blades 12, 13). When the sealer block 5 is moved to its closed or compressed position, the spring loaded pin 28 can retract into the sealer block as required.

Figure 4 shows a schematic, partial rear view of the strapping tool, illustrating the adjustable stop mechanism 14 of the sealer handle 6. The handle 6 is preferably connected to the cam shaft 30 by way of the square section end 31 of the cam shaft. The handle 6 therefore pivots about the cam shaft axis 21.

At the end of the handle 6, a grub screw or pin 41 passes through the handle 6 and extends laterally therefrom in the plane of rotation of the handle. The extending portion 42 of the grub screw 41 collides end on with an end stop block 43 when the handle is in its extreme clockwise position (as seen in figure 4). This corresponds to a compressed or closed position of the sealer block 5 as indicated in dotted outline. The precise position of sealer block which corresponds to a compressed position can therefore be varied and, importantly limited by adjustment of the grub screw 41 to vary the extent of the extending portion 42.

The handle 6 is preferably biassed in an anticlockwise direction (viewed from the perspective of figure 4) away from the closed position shown in figure 4 and towards the open position shown in figure 5, by a suitable spring mechanism (not shown).

Figure 5 shows a schematic, partial rear view of the strapping tool 1, illustrating an opening stop of the sealer handle 6. At a predetermined extent of rotation of the handle 6 in the anticlockwise direction (as seen in figure 5), corresponding to the normal open or release position of the sealer block, further anticlockwise rotation of the handle is resisted by a spring biassed plunger 50 having a roller surface 51 for contacting the lower surface of the sealer handle 6. An internal spring 52 provides the bias mechanism. Thus, the spring biassed plunger provides, in the normal open or release position a clockwise bias to the sealer handle 6, the cam shaft 30 and thereby a limited downward bias on the sealer block 5 which holds a seal 40 in position ready for a sealing operation, by a friction fit.

By virtue of additional travel of this plunger 50, available by compressing the spring 52, the sealer handle 6 may be moved, against the bias, to an extended release position in which the sealer block 5 is raised beyond the position normally required for insertion and removal of seals 40 and strapping material. This enables extra large or oversize seals to be accommodated on an ad hoc basis without requiring adjustment of the tool.

In another embodiment (not shown), the normal position of the plunger 50 may be adjustable to accord with a preferred size of seal in predominant use.

Figure 6 shows a schematic partial rear view of the strapping tool 1 with part of the housing 2 cut away to reveal detail of a preferred strap tensioning mechanism.

The strap tension handle 7 and a ratchet wheel 61 are independently rotatable on an axis defined by axle 60. A top ratchet tooth 62 is pivotally mounted on the tension handle 7 and engages with the ratchet wheel 61 when the handle 7 is operated in the clockwise direction (as viewed from the perspective of figure 6). A pawl 65 prevents return of the ratchet wheel 61 during return of the handle in an anticlockwise direction (as viewed from the perspective of figure 6), according to well known mechanical principles. The tension handle 7 is free running about the axle 60, whereas the ratchet wheel is in fixed relation to the axle 60 together with the strap capstan 8 on the front end of the axle 60 (as seen in figure 1). Thus, rotation of the ratchet wheel within the housing 2 causes corresponding rotation of the strap capstan 8.

The strap gripper foot 9 is lifted and lowered by gripper foot operating lever 66 which is spring loaded by the coil spring 67 in a clockwise direction to keep the gripper foot closed against the base plate 3. The operating lever 66 includes a roller 68 upon which a lower surface of the tension handle 7 can act. The gripper foot 9 is lifted by depressing the tension handle 7 which in turn rotates the operating lever 66, lifting the gripper foot.

Figure 7 shows a schematic partial front view of the strapping tool 1 with part of the housing 2 cut away to reveal detail of a preferred strap cutting mechanism. Further detail of the cutter mechanism is revealed in the exploded view of components of the mechanism, as shown in figure 8.

The tension handle 6 includes a cutter cam 70 rotating therewith. The cutter cam includes an indented portion 71 which co-operates with a cutter shaft tooth 72. The cutter includes the upper, fixed blade 12 and the lower, rotating blade 13 as shown in figure 1. The fixed blade 12 defines a inner curved surface 73 which forms part of a circular cylindrical surface. The rotating blade 13 defines a corresponding outer curved surface 74, which also forms part of a circular cylindrical surface. The partial circular cylindrical surfaces have substantially the same radius and are coaxial with one another. Thus, upon rotation of the blade 13 in an anticlockwise direction (as viewed from the perspective of figure 7) about the cylinder axis, the curved surfaces 73, 74 are brought into sliding engagement, a leading edge 78 of the blade 13 passing a corresponding leading edge of the fixed blade 12 to effect a cutting action of any strapping material positioned between the blades.

As more clearly shown in figure 8, the rotating blade 13 extends forwards from a cylindrical cutter shaft 75 which is coaxial with and rotates within a cylindrical fixed collar 76. The fixed collar 76 provides the mounting from which the fixed blade 12 extends forwards. The cutter shaft tooth 72 is drivingly engaged with the cutter shaft 75 and engages with the cutter cam 70.

The cutter shaft tooth 72, and thereby the cutter shaft 75 with rotating blade 13 are biassed, by a coil spring 77, in a clockwise direction to a home position as shown in figure 7. A cutter cam stop pin 78 (figure 8) may be provided to prevent over-rotation of the cutter shaft tooth 72.

In operation, when the tension handle 7 is operated to tension the strapping material, the cutter shaft tooth 72 merely rides over the trailing edge of the indented portion 71 of the cutter cam 70. However, when the tension handle 7 is rotated toward the gripper foot 9 release position, the cutter shaft tooth 72 first engages with the leading edge of the indented portion 71 (as depicted in figure 7) and further movement of the tension handle 7 causes rotation of the blade 13 toward the fixed blade 12.

The operation of the strapping tool 1, including sealer block mechanism, tensioning mechanism, strap gripping mechanism and strap cutting mechanism will now be described with reference to all of the figures.

1. The sealer handle 6 is depressed slightly, if necessary, to lift the sealer block 5 from its release position to an extended release position, so that a seal or clip 40 may be inserted (figure 3).

2. The sealer handle 6 is then released to return to the normal release position under the bias of the plunger 50. The seal will remain in position by a friction fit against the bias of the plunger 50 and will also be prevented from sliding toward the cutter by spring loaded pin 28 (figure 2), if fitted.

3. Strapping material is pulled from a reel by a free end thereof and passed around a package for strapping. The leading (free) end of the strapping material is placed along side the front of the tool 1 (as viewed in figures 2 and 7), with the free end positioned to the left of the sealer block 5, and the remaining strap extending clockwise around the package below the tool.

4. The tension handle 7 is then depressed, against the bias of coil spring 67 to lift the gripper foot 9 away from the base plate 3 so that the strapping material can be inserted edgewise: (a) between the gripper foot and the base plate, the tension handle then being release to so that the gripper foot 9 clamps the strapping material; (b) passing beneath both cutter blades 12, 13; and (c) between the sealer block 5 working surface 27 and base plate working surface 4 and, of course, within the open seal 40 (figure 3). The tension handle is release so that the strapping material is tightly retained by the gripper foot 9.

5. The other end of the strapping material (as yet still attached to the reel) is also placed along side the front of the tool and also inserted edgewise: (a) between the sealer block 5 working surface 27 and base plate working surface 4 and, of course, within the open seal 40, over the top of the previously inserted strapping material; (b) passing between the fixed and rotating cutter blades 12, 13; and (c) into a slot 18 of the strap capstan 8. The strapping material reel will be to the right of the tool (as viewed in figures 2 and 7).

6. The strapping material is then tensioned by repeatedly rotating the tension handle 7 which winds the strap capstan using the ratchet wheel 61 in an anticlockwise direction as viewed from the perspective of figure 2.

7. When the required degree of strap tension is achieved, the sealer handle 6 is rotated anticlockwise (figure 2) which causes the sealer block 5 to be lowered by the co-operation of cam shaft 30, cam 20, collar 23 and connecting rod portion 24, and pivot 26. Over compression of the sealer block is prevented by the action of the adjustable stop member 14 comprising grub screw 41 and end stop block 43. The sealer handle 6 returns to the release position (figure 5), raising the sealer block 5.

8. The tension lever is then pressed again which (a) rotates the cutter blade 13 severing the strap lying between the cutter blades 12, 13; and (b) lifts the gripper foot 9 facilitating removal of the strapping tool from the strapping material which is now securely bound around the package being strapped.

The construction of the manual strapping tool described herein offers a significant number of advantages over various prior art manual strapping tools.

Firstly, a common problem with existing tools is that over-aggressive use of the sealer handles invariably causes distortion and damage in the drive mechanisms of the sealer block, in particular to the sliding mechanism and the cam drive. In particular, prior art designs typically provide a small cam surface, lever or pin on the handle itself so that handle forces are directly transmitted to the sealer block mechanism. In the present preferred design however, the sealer handle 6 drives a cam shaft 30 at an end remote from the driving cam 20 and the sealer block 5, thus all forces are transmittable only through the cam shaft 30. Little or no shear forces are applied to the drive mechanism on the sealer block end of the cam shaft.

The bearing 32 and reinforced side wall 15 in which the handle end of the cam shaft 30 is housed can be made particularly robust and carry any unwanted torsional forces. The adjustable stop member 14 can be used to prevent over travel of the sealer handle 6, thereby remotely preventing over-travel of the sealer block itself.

The preferred design of the adjustable stop member is by the grub screw 41 which acts on the end stop block 43 in compression, preventing shear thereof. (Any shear forces only exist over the entire length of the screw thread.) In prior art designs, it is customary for the return of the sealer block to its release position to be by spring bias or by small return pin. Fatigue in such springs is common. Shearing of the return pin is also common.

The use of the cam shaft arrangement of the preferred embodiment also facilitates use of a cam 20 which is internal to the collar 23 which extends completely or substantially around the cam 20. This means that an equal and opposite force can always be applied to return the sealer block after compression of the seal, thereby assuring the user that the sealer block cannot jam or stick. The loading of the cam 20 on the sealer block 5 is through the collar 23 which maximizes cam surface area under load.

The preferred embodiment also offers very simple and low cost repair and replacement of critical parts of the mechanism. The handle is easily removable from one side of the housing 2. The cover plate 35 enables easy removal of the cam shaft 30 in the event of damage thereto. The cam shaft can readily be made a sacrificial component protecting all others on the housing 2.

The provision of an "extended release" facility as described above also offers a significant improvement in convenience of use. Use of generic seals which are not necessarily manufactured to a high specification, and which therefore may vary in thickness tolerances, are easily accommodated on an ad hoc basis without requiring any physical adjustment of the tool (although such adjustment is still possible for regular use of different thicknesses of seal).

Claims

CLAIMS 1. A manual strapping tool for securing two ends of strapping material together with a seal, comprising: a housing; a baseplate coupled to said housing; a sealer block, in sliding engagement with the housing, for compressing seals between the sealer block and the baseplate; a drive mechanism for reciprocating the sealer block in a direction substantially perpendicular to the baseplate, between a compression position and a release position, the drive mechanism including a cam shaft passing through said housing; a handle in driving engagement with said cam shaft; a cam, axially displaced from said handle along said cam shaft; a collar, substantially surrounding the circumferential surface of said cam, said cam being rotatable in the collar, said collar being in driving engagement with said sealer block.
2. A manual strapping tool according to claim 1 in which said handle includes an adjustable stop member which acts against an end stop on said housing to prevent rotation of said cam shaft beyond a predetermined compression position.
3. A manual strapping tool according to claim 2 in which the adjustable stop member comprises a grub screw extending laterally from the pivot end of the handle, within the plane of rotation of the handle.
4. A manual strapping tool according to claim 1 in which the drive mechanism further includes means for driving the sealer block, against a bias, to an extended release position.
5. A manual strapping tool according to claim 4 in which the means for driving the sealer block to an extended release position is actuated by said handle in driving engagement with said cam shaft, operating against a spring load.
6. A manual strapping tool according to claim 1 in which the bearing surface between cam and collar extends completely around the circumferential face of the cam, such that the areal extent of the driving surfaces for movement towards the compression position is approximately equal to the areal extent of the driving surface for movement towards the release position.
7. A manual strapping tool according to claim 1 in which the housing includes: a first housing wall and a bearing therein to support the cam shaft at the handle end thereof, a second housing wall and a bearing therein to support the cam end of the cam shaft, the first housing wall being reinforced over the second housing wall.
8. A manual strapping tool according to claim 1 in which the cam shaft includes a portion of reduced thickness between the handle and the cam as a sacrificial component.
9. A manual strapping tool according to claim 1 further including a cutter comprising a first blade defining an inner curved surface 73 which forms part of a circular cylindrical surface, a second blade defining a corresponding outer curved surface 74, which also forms part of a circular cylindrical surface, the circular cylindrical surfaces having substantially the same radius and being coaxial with one another, rotation of the second blade relative to the first, about the cylinder axis, bringing the curved surfaces into sliding engagement such that a leading edge of the first blade passes a corresponding leading edge of the second blade to effect a cutting action of any strapping material positioned between the blades.
10. A manual strapping tool substantially as described herein with reference to the accompanying drawings.