GB2177337A

GB2177337A - Nibbling tool

Info

Publication number: GB2177337A
Application number: GB08605218A
Authority: GB
Inventors: Kenneth John Turner
Original assignee: Turner
Current assignee: Turner
Priority date: 1985-07-02
Filing date: 1986-03-03
Publication date: 1987-01-21
Also published as: GB8605218D0; GB2177338A8; GB2177338B; GB8605219D0; GB2177338A; GB8516711D0

Abstract

The invention concerns a nibbling tool for cutting sheet material having a body (12) in which a rotary shaft (14) is mounted for rotation by an external drive means. The rotary shaft is coupled to a punch (34) by coupling means (41-45) which convert the rotary movement to a reciprocal movement of the punch. The punch is guided in a die (27) with the punch and die having co- operating cutting edges. The die (27) has a circular sectioned shank (28) located as a good sliding fit in the body (12) and retained by a screw (30) projecting into a recess (29) in the shank (28). When the screw (30) is released the die can be rotated to change the cutting direction or removed and replaced without opening up the body or taking out other parts. With the die removed the punch can be removed easily. The punch is guided both at its upper end in a bore (25) in handle (23) and at its lower end by its head (38) located in a bore in a die extension (53). <IMAGE>

Description

SPECIFICATION Nibbling tool This invention relates to a nibbling tool for shearing sheet material and more particularly to a hand held tool which may have its own drive or have a rotary drive shaft designed to be coupled to an external drive means, for example the chuck of a conventional electric drill.

Nibbling tools are known comprising a body, a punch, drive means for reciprocating the punch and a die defining a channel for guiding the punch for reciprocating movement, the punch and die having cooperating cutting edges. Normally a drive shaft is mounted in the body for rotation about its axis and coupling means couple the punch and drive shaft for converting the rotational movement to linear reciprocation of the punch.

Punches are known which are arranged to cut on either the downward stroke (out of the body) or the upward stroke (into the body).

We have devised a nibbling tool having several improved novel features which may be claimed separately or in any combination.

In a preferred form the invention provides A nibbling tool comprising a body, a punch, drive means for reciprocating the punch and a die defining a channel for guiding the punch for reciprocating movement, the punch and die having co-operating cutting edges, in which the die is mounted in the body by retaining means which when released allow the die to be rotated about its axis without axial movement or to be removed from and re-connected to the body without opening up the body or disconnecting other parts. This allows easy adjustment of the cutting direction and easy die replacement. Preferably the punch is arranged to cut on the upward stroke or on both the upward and downward strokes.Preferably the lower portion of the punch is guided throughout the stroke.This allows the die portion carrying the cutting edge which co-operates with the punch in the shearing action to be made stronger and thus with less movement so that the gap between the shearing faces of the punch and die can be kept to a minimum reducing burr at the cut edge; for example this gap can be reduced to 5/1000 of an inch. (0.0127 cms) and in any case preferably not more than twice this.

According to one feature, the punch has a shaft portion and a head which includes the upward cutting face on its upper surface and which is connected to the shaft portion by a tapered portion, the shaft and head portion both being cylindrical and preferably of the same diameter.

Preferably the die has an upper circular sectioned shank located as a good sliding fit in a bore in the body, the shank being provided with at least one locating recess (either annular or, for example, four angularly spaced at 90 intervals) into which a retaining member, such as a screw, movable in the body can be inserted to locate it against axial and rotational movement.

According to another feature a handle is connectable to the upper part of the body coaxial with the punch and die and the upper end of the punch is a sliding fit in a bore in the handle (preferably in a bush) so that the upper end of the punch is guided.

According to another feature the punch is also guided for sliding movement in a lower part of the die (below the cutting plane) so that the punch is guided at each end throughout its stroke in both directions.

According to another feature the punch has a shaft portion and a guide portion of lesser diameter than the shaft portion and connected therewith, the guide portion being eccentrically mounted with respect to the shaft portion so that one axially extending edge thereof is aligned with an edge of the shaft portion.

According to a further feature the coupling means comprises a punch location block secured to the punch shaft and defining a (preferably non circular) recess on one side opposite the head of the rotatable drive shaft, and a drive transfer bearing fitted in the recess and lightly compressed or cushioned between the location block and the drive shaft head and having a recess receiving an eccentrically mounted pin on the drive shaft head. This arrangement ensures improved smoothness of action and torque transmission.

Embodiments of nibbling tool, in accordance with the invention, will now be described by way of example only with reference to the accompanying drawings of which: Fig. 1 is an elevational view of a nibbling tool, Fig. 2 is a section on the line Il-Il of Fig. 1, Fig. 3 parts A, B and C are a side view, front view and an underneath plan view respectively of the die of the tool of Figs. 1 and 2, Fig. 4A is a side view of the punch of the tool on an enlarged scale, Figure 4B shows a modified form of part of the punch of Fig.4A, Fig.5 is a view similar to Fig.2 showing an alternative form of tool, Fig.6 parts A and B show an enlarged side and end view of the punch of the Fig.5 tool, and Fig.7 parts A and B are side and front views of a nibbling tool coupled to a drive means.

Fig.8 is a veiw of the parts forming the drive coupling of the tool.

The nibbling tool of Figures 1 to 4 com prises a body 12 having a first bore 13 in which a rotary shaft 14 having a head 15 is mounted in needle roller bearings 16. The projecting end 17 of the shaft is hexagonal to enable it to be easily gripped by, for example the chuck of a conventional electric drill. The bore 13 opens to a counter bore or recess 18 opening to the other side of the body, which recess is closed by a cover 20 retained by a circlip 21. A cross bore 22 extends through the body and recess 18 at right angles to the bore 13. A handle 23 having a threaded shank 24 is screwed into the upper part of bore 22.

The lower end of the handle defines a bore 25 in which is located a bearing bush 26. The handle may be covered with a rubber or plastics material sleeve grip with finger moulds.

A die 27 machined from hexagonal bar has a circular sectioned cylindrical shank 28 located as a good sliding fit in the lower part of bore 22. The shank is formed with four conical recesses 29 spaced there around at 900 intervals and a conical ended screw 30 extending through a threaded bore 31 in the body locates in one of the recesses 29 to restrain the die against rotational and axial movement in the bore 22.

As an alternative, shown in Figure 3B, a single annular conical sectioned recess 29A is provided. Frictional engagement is sufficient to restrain the die against rotary movement. A punch 33 has an upper shaft portion 34 joined at a shoulder 35 (which limits the downward stroke) to a lower, reduced section, shaft portion 36 connected by a tapered portion 37 to a head 38 having the same diameter as the lower shaft portion 36. The main upper shaft portion 34 of the punch is guided in a bore 40 in the die for vertical reciprocation. The upper end of the shaft is guided in the bush 26. The diameter of parts 36 and 38 is kept to at least 3 mms. preferably 3.5 mm. to give rigidity and strength with the actual cutting section width no more than 3 mm. The tapered portion 37 absorbs the shock impact of the material being cut and pushes it towards the cutting edge.This reduces vibration and allows a higher cutting speed.

Coupling means (best seen in Fig.8) for coupling the drive shaft 14 and the punch to convert the rotary movement of the drive shaft to vertical reciprocation of the punch comprise a punch location block 41 secured to the punch by a grub screw 42 and defining a slot recess 43 in its face opposite the shaft head 15. A drive transfer bearing block 44 is slidably located in the recess 43 for horizontal sliding therein and is lightly compressed so that it is cushioned between the punch location block and the head of the shaft and receives in a recess therein an eccentric driving pin 45 on the shaft head. The bearing block 44 is hexagonal or rectangular sectioned and receives the eccentric pin as a good fit thus providing positive location and support for the bearing.Rotation of the eccentrically mounted pin causes reciprocal vertical movement of the punch and block 41 while the transfer block 44 slides horizontally. Because a considerable area is in contact between the bearing block 44 and the sides of the recess 43, the contact forces are minimised and evenly distri buted. This provides a compact, efficient and easily manufactured coupling but other forms of drive and coupling may be used, for example compressed air drive. In addition this tool may have its own motor.

Referring particularly to Figs. 3a, 3b and 3c the lower portion of the die is cut away from one side above and below a projecting portion 50 formed with a bore 51 for receiving the punch, the lower edge of this bore defining a cutting edge 51A co-operating with a cutting edge 52 on the upper surface of the head 38 of the punch. The lower part 53 of the die defines a bore 54 in which the head of the punch is guided for reciprocation during the whole stroke of the punch, this lower part being connected to the main die block by a narrow web 55 which is the same thickness as the punch cutting diameter so that it fits in the cut being formed in material and facilitates material feed. The corners 55A where the web joins the block and head are radiused at 0.38 cms which add strength and reduces burr at the cut edges.The scalloped Section 56 nearest to the shank which is profiled out to the inside edge of the internal bore is provided to allow for the clearance of swarf, dirt etc. after the upward cutting stroke of the punch.

By cutting upwards against the well supported portion 50, as opposed to downwards against portion 53 supported only by web 55, and providing good guiding of the punch, the parts defining the cutting edges are sufficiently rigid and stable that a small gap between the cutting edges can be obtained, in this example 0.0127 cms., thus keeping burr to a minimum. The mounting of the punch and die allows adjustment of the cutting direction and easy replacement of the die without removing any other parts and easy replacement of the punch by removing the die and disengaging screw 42.

The tool may be used to cut on the downward stroke or on both the upward and downward strokes by using the cutting edges 57 and 58.

Figure 5 shows a modified tool having a punch intended to cut on the down stroke only. The tool is similar to that of Figures 1-5 and like parts have been given the same reference numerals. The lower shaft portion 36 of the punch is joined by a shoulder 60 to a lower guide portion 61 which is guided in a bore 62 in the lower die part 53.

In a modification shown in Figure 6 the lower guide part 61 is eccentrically mounted compared with the axis of the punch so that its back edge 64 is aligned with the corresponding edge of the shaft part 36 to give better guiding. The cutting edge is shown at 65. A similar modification to the punch of Figures 1-4 is shown in Figure 4B where the tapered portion 37 is eccentrically mounted to give a continuous back edge 66 acting as a further guide.

Conventionally where the drive has been taken from a power drill or the like the nibbling tool has been held by the user on to the drill while in use. Figures 7A and 7B show a means for mounting the nibbling tool to an external drive such as a drill so that it need not be manually held during use. A drill head 70 is shown engaged with the projecting end 17 of the shaft 14 of the nibbling tool. A pair of clamp supports 71 having arcuate surfaces dimensioned to engage round the body 12 of the tool and a similar body portion 72 of the drill engage a base plate 73. A pair of U-bar clamps 74 extend over the other sides of the body portions 12 and 72 through bores in the clamp supports 71 and baseplate 73 and are secured thereto by nuts 75 engaging their threaded ends 76. A guard 77 may be provided mounted by flanges on the baseplate.

This guard is split into two halves to facilitate fitting of the motor drive to the nibbling tool and the halves are secured together via a slot 78 allowing use of a screwed fastener. The drill with nibbling tool may be mounted on a work bench or the like, leaving both the operator's hands free to guide the sheet being cut.

Claims

1. A nibbling tool comprising a body, a punch, drive means for reciprocating the punch and a die defining a channel for guiding the punch for reciprocating movement, the punch and die having co-operating cutting edges, in which the die is mounted in the body by retaining means which when released allow the die to be rotated about its axis without axial movement or to be removed from and re-connected to the body without opening up the body or disconnecting other parts.

2. A tool according to Claim 1 in which the die has a circular sectioned shank located as a good sliding fit in a bore in the body, the shank being provided with at least one locating recess into which a retaining member movable in the body can be inserted to locate the die against axial and rotational movement.

3. A tool according to Claim 2 in which there is a single annular recess.

4. A tool according to Claim 2 in which there are a plurality of recesses angularly spaced around the shank.

5. A tool according to any of Claims 1-4 in which the punch has a shaft portion and a head portion connected to the shaft by a connecting portion, the head including an upward cutting edge.

6. A tool according to Claim 5 in which the connecting portion is tapered.

7. A tool according to Claim 5 or Claim 6 which can cut on the upstroke, the downstroke or both strokes.

8. A tool according to any of Claims 5-7 in which the connecting portion is eccentrically mounted so that its back edge is aligned with the shaft portion.

9. A tool according to any of Claims 1-4 in which the punch has a shaft portion connected by a shoulder including a downward cutting edge with a guide portion arranged to be guided by part of the die, in which the guide portion is eccentrically mounted with respect to the shaft of the punch so that it has a back edge aligned therewith.

10. A tool according to any of Claims 1-9 in which the die has a main body portion defining the channel for guiding the punch, connected by a narrow web portion to a lower guide portion in which the lower end of the punch is guided.

11. A tool according to Claim 10 in which the corners connecting the web portion with the main body portion and the guide portion are radiused.

12. A tool according to any of Claims 1-11 in which the gap between the shearing faces of the die and punch is no more than 0.0254 centimetres.

13. A tool according to any of Claims 1-12 including further guide means arranged to guide the upper end of the punch throughout its reciprocating movement.

14. A tool according to Claim 13 including a handle connectable to the body and defining the further guide means.

15. A tool according to any of Claims 1-14 including coupling means comprising a punch location block secured to the punch shaft and defining a (preferably non-circular) recess on one side opposite the head of the rotatable drive shaft, and a drive transfer bearing fitted in the recess and lightly compressed or cushioned between the location block and the drive shaft head and having a recess receiving an eccentrically mounted pin on the drive shaft head.

16. A tool according to any of Claims 1-15 adapted to be coupled to an external drive.

17. A tool according to Claim 16 including connecting means for holding the tool to an external drive.

18. A tool according any of Claims 1-15 including its own motor.

19. A nibbling tool substantially as described herein with reference to Figures 1-4 Figure 5 or Figure 6.

20. A connection and mounting assembly for a nibbling tool substantially as described herein with reference to or as illustrated in Figures 7A and 7B.