Dimpling tool

Abstract

 The invention relates to a dimpling tool (1) or the like for forming dimples in metal sheet (35). The sheet (35) is positioned on an anvil (7) for support. In order to accommodate different gauges of sheet metal the anvil may be moved towards or away from a body (3) of the tool. This movement is facilitated by cooperating screw threads on the tool body (3) and an anvil clamp (33).

Description

[0001] The invention relates to a tool for working sheets of material and particularly, but no exclusively, to hand-held tools for the dimpling or the like of thin metal sheets.

[0002] The process of dimpling is particularly advantageous when it is desired to join thin sheet metals using countersunk rivets. A dimpling tool forms a hole in the metal sheet and presses the surrounding metal into a shape to accommodate the rivet head. In contrast, countersinking involves the removal of metal from around the hole to accommodate the rivet head which makes it inappropriate for thin sheet metals. An example of a dimpled sheet of metal is shown in Figure 1.

[0003] Conventional dimpling tools comprise a main body which houses a drill motor which is operable to rotate a dimpling tool bit which protrudes from the main body. What is known as an anvil, which supports the metal sheet to be dimpled and defines the shape of the dimple, is attached in fixed relation to the main body. On application of air pressure the drill motor is made to rotate the dimpling tool bit, and is also forced to move in a direction longitudinal to the main body such that the rotating bit comes into contact with the metal sheet thereby forming a dimple.

[0004] As will be appreciated by those skilled in the art, there is an optimum distance between the drill bit in its inoperative position and the top face of the metal sheet, ie that facing in the direction of the main body of the tool. If the distance strays outside the optimum, this will result in poorly formed dimples and/or their orifices being excessively burred. In order to allow dimpling tools to dimple sheets of various gauges, while retaining the optimum distance between bit and sheet, various adjustment mechanisms have been devised. These methods consist of either adjusting the position of the drill motor inside the main body or adjusting the nose piece around the bit. Both these methods are complicated and time consuming because they require the partial dismantling of the dimpling tool.

[0005] Another problem with conventional dimpling tools is that the removal of their anvils is time consuming, as they are often attached to the main body by a plurality of bolts. The problem is exacerbated by the need to enable different shapes and sizes of dimple to be made.

[0006] According to the invention there is provided a tool comprising a main body portion which supports a bit to work a sheet of material, and anvil means to support the sheet of material and which is threadedly attached to the main body portion such that movement of the anvil means in the thread results in a change in the distance between the main body portion and the sheet of material.

[0007] Such a tool, which may be suitable for dimpling, can facilitate easy adjustment of the distance between the dimpling tool bit and the top face of the sheet to be dimpled.

[0008] The anvil can preferably be simply and quickly removed and replaced.

[0009] Conveniently the bit is rotated by a motor releasably attached thereto and which is housed in the main body portion.

[0010] Preferably the motor is an air motor.

[0011] Conveniently the bit is releasably attached to the motor by means of a key chuck.

[0012] Preferably the anvil means includes means for substantially preventing movement of the anvil means relative to said main body portion.

[0013] The invention is diagrammatically illustrated by way of example in the accompanying drawings, in which:

Figure 1 shows a cross-sectional view through a dimpled sheet of metal;

Figure 2 shows a partially cross-sectional view of a dimpling tool according to the invention; and

Figure 3 shows an overhead view of a screw-clamp to attach an anvil to a main body of the tool shown in Figure 2.

[0014] Referring to the drawings, a spin dimpling tool is shown generally at 1 in Figure 2. The tool 1 includes a main body 3, an air-driven drill motor 5, an anvil 7, a gas inlet assembly 9 and two gas outlet ports 11 and 13. The drill motor 5 includes a conventional key chuck 15 which releasably holds a dimpling tool bit 17, allowing it to be easily removed and replace with another item. At the upper, gas inlet, end of the dimpling tool is a cylindrical bore 19 formed within the main body 3. A complementarily sized piston 21 is positioned within the bore 19 for longitudinal movement with respect to the main body 3. An O-ring 23 is disposed around the periphery of the piston 21 to form a gas tight seal with the bore 19.

[0015] A substantially cylindrical space 25 in the main body 3 in which the drill motor 5 is housed is lined with a PTFE bearing surface 27. The drill motor 5 is driven by gas supplied via a feed line 29.

[0016] A lower portion 31 of the main body 3 is externally threaded with a corresponding pattern to the inner surface of a screw clamp 33 which is mounted therearound.

[0017] When it is desired to dimple a sheet 35 of metal, the sheet 35 is preferably clamped in a vice (not shown) at one end, while the other end is juxtaposed with an end piece 37 of the anvil 7, the end piece 37 including a hole 39 into which the dimpling tool bit 17 may enter and the hole 39 having an entrance 41 the concave shape of which determines the shape of the dimple.

[0018] When the operator is satisfied that the sheet 35 and the dimpling tool 1 are correctly positioned, a pressurised gas supply (not shown) is put in communication with a space 43 of the bore 19 by the operation of a lever 45 of the gas inlet assembly 9. As the gas enters the space 43 it exerts pressure on the upper surface of the piston 21, thus propelling the piston 21 downwards in the direction of arrow 47 with gas being expelled through the outlet port 11. A proportion of the gas entering the space 43 will pass through an entrance 49 of the feed line 29 and pass therealong into the drill motor 5, thus causing its rotation and that of the bit 17. As the piston 21 moves downward it acts on a piston rod 51 which imparts the downward motion to the drill motor 5 and, as a corollary, to the dimpling tool bit 17, gas being expelled through the outlet port 13 as required. As a result of the contemporaneous downward and rotational movements of the bit 17, it can pierce the metal sheet 35 and form a dimple therein as it presses the sheet 35 against a surface of the entrance 41 of the end piece 37 of the anvil 7. An example of a dimpled sheet of metal is shown in Figure 1.

[0019] In order to accommodate different gauges of metal sheet 35, a distance l, between the upper face of the sheet 35 supported by the end piece 37 of the anvil 7 and the main body 3, can be adjusted by screwing the screw clamp 33 either clockwise or anti-clockwise about the threaded lower portion 31 of the main body 3.

[0020] A better understanding of the working of the clamp 33 can be had by reference to Figure 3 which shows an overhead view, such that, if illustrated, the longitudinal axis of the main body 3 of the drill would be perpendicular to the plane of the paper. The clamp 33 is of one piece construction but has a section 53 removed from between its outer and inner surfaces to allow its tightness around the main body 3 to be adjusted by way of nuts 55 and bolts 57 (one each of which only are visible in Figure 3). It is desirable to have the anvil 7 clamped tightly to the main body 3 during dimpling operations so that the anvil 7 does not move as the bit 17 comes into contact with the metal sheet 35. Conventional quick release pins 59 (one of which only is visible in Figure 3) are provided to enable the anvil 7 to be quickly removed from the screw clamp 33 and exchanged for another. This removal is facilitated by the depression of release buttons 61 which then allow the release pins to be withdrawn from the clamp 33 and the anvil 7 to be removed.

[0021] It should be understood that the various assemblies described herein can be used in operations other than dimpling of metal sheets.

Claims

1. A tool comprising a main body portion (3) which supports a bit (17) to work a sheet (35) of material, and anvil means (7) to support the sheet (35) of material, the anvil means being attached to the main body portion (3) by means of a screw thread such that rotational movement of the anvil (7) with respect to the thread results in a change in the distance between the main body portion (3) and the sheet of material (35).

2. A tool according to claim 1, wherein the bit (17) is a dimpling bit.

3. A tool according to claim 1 or claim 2, wherein the bit (17) is rotated by a motor (5) releasably attached thereto and housed in the main body portion (3).

4. A tool according to claim 3, wherein the motor (5) is an air motor.

5. A tool according to claim 3, wherein the bit (17) is releasably attached to the motor (5) by means of a key chuck (15).

6. A tool according to any preceding claim, wherein the anvil means (7) includes means (33) substantially to prevent undesired movement of the anvil means (7) relative to the main body portion (3).

7. A tool according to any preceding claim wherein the outer surface of the main body (3) has a screw thread thereon and the anvil (7) is secured to a clamp (33) which has a bore with a screw thread therein engaged with the screw thread on the main body (3) such that by rotating the clamp (33) with respect to the main body (3) a workpiece supporting portion (37) of the anvil can be moved towards or away from the main body.

8. A tool according to any preceding claim, formed as a hand-held tool (1).

Drawing