GB2042667A - Improvements in or Relating to Power-driven Tools - Google Patents

Abstract

A traction pin for a power-driven tool has a pin end (1) by which it is coupled to the power-driven tool, a pin shaft (2) extending therefrom and having, connected at and extending on from its opposite end, a traction rod (3). The traction rod has a free end (7) by which tool parts are attached, and accommodates an extensible strip, typically a wire (8), that is fixed on the one hand to the free end (7) of the traction rod, and on the other hand to a spaced position on the traction pin. Then, if the traction pin breaks under stress the broken parts will be restrained by the strip. <IMAGE>

Description

SPECIFICATION Improvements in or Relating to Power-driven Tools The present invention concerns improvements in or relating to power-driven tools, especially hand tools such as punch presses, and has particular reference to traction pins of or for such tools.

Traction pins as generally utilised in power tools, such as hydraulically operated hand tools, serve in drawing tool parts together for performing pressing or stamping operations. In a typical arrangement, the traction pin is secured at one end to one of the press tool parts of the power-driven tool and has a threaded free end for connection of another press-tool part.

If the thickness of a workpiece is too great for particular pressing tools to handle, or if a wrong pressing or stamping tool part is used the traction pin may break. Then, the traction pin usually breaks at some point along its traction rod if not at the position of its threaded end connection to other press tools. Since the traction pin is under considerable traction stress during the working operation, a sudden break in the traction rod may cause the broken end of the traction pin along with its threadably mated tool member to fly off in an uncontrolled manner and possibly cause damage or injury.

It is an object of the present invention to mitigrate this problem arising from traction pin breakage.

To this end, we provide traction pin having a pin end part, advantageously a pin head, adapted for being held in a power tool, a pin shaft extending from said pin end part, a traction rod connected to extend from said pin shaft and being adapted, normally threaded, at its free end for attachment of a tool part, and extensible strip means fixed at spaced positions one to the traction rod in the region of its free end and the other to the traction rod and/or to the pin shaft, preferably with its intermediate parts loosely accommodated in a guide lengthwise of at least the traction rod. The strip means can be elastically and/or plastically extensible.

If the traction pin should break during working operation of a power tool, the broken-off end of the traction rod, along with the tool part attached thereto, is limited by the strip means as to the distance it can travel. The extensible strip means can be of an appropriate length and energy absorption capability so that the broken-off end of the traction pin will remain connected to the rest of the traction pin. However, even if the stress on the strip means becomes so great as to break the strip means, sufficient energy will have been expanded to ensure that the broken-off end of the traction pin will no longer cause great damage or be a significant hazard.

In a preferred embodiment, the traction rod is of hollow form, and its cavity serves to accommodate the extensible strip means.

However, especially if of profiled section, the traction rod may have at least one external groove.

therealong to accommodate the strip means.

Such external grooving may serve as a guide groove for rectangular tool parts. That grooving could extend into a threaded said free end of the traction rod. The strip means may, of course, extend into and along threaded courses of the traction rod.

Preferably, the extensible strip means will be in the form of a wire, say of steel. The length of such wire can be increased by running the wire other than straight, say, in a wavy or undulating manner, and can then absorb energy also in being straightened. Such undulations can be accommodated at or near the traction rod interfitment with the pin shaft, especially within the latter which will have a larger diameter than the traction rod.

One embodiment of this invention will now be described specifically, by\way of example, with reference to the accompanying drawings, in which:~ Figure 1 is a partially cross-sectional view of a traction pin: Figure 2 is a cross-sectional view along the lines 2-2 of Figure 1; and Figure 3 is a partially cross-sectional view of the traction pin of Figure 1 in a press.

Referring to Figures 1 and 2, the traction pin has a pin head 1 with a pin shaft 2 extending to a traction rod 3. Pin shaft 2 has an axial blind bore 4 that is internally threaded at 5 to mate with one externally threaded end of the traction rod 3. Pin shaft 2 and traction rod 3 are further secured to each other, where they overlap, by means of a radial securing pin 6 in aligned openings in the pin shaft and the traction rod.

The traction rod 3, at its free other end, has an external thread 7 for connection to a further tool part as subsequently discussed.

The traction rod 3 is actually shown as a hollow rod or tube, that accommodates an extensible strip 8, shown as a wire with a soldered anchorage at one end to the traction rod 3 adjacent the outer thread 7. Towards the other end of the wire 8 is an undulation 9. The wire 8 extends into the blind bore 4 and is fixed at a position spaced from traction rod end thread 7, either to the traction rod 3 or to the pin shaft 2, or possibly to both. As shown, using a tubular traction rod 3, securement of the wire to that rod at or near both ends is advantageous.

Possibly, a longitudinal guide for the wire 8 or other extensible strip, could be in the form of an external groove traversing along the length of the traction rod 3.

Referring to Figure 3, the preferred traction pin is shown in a press tool of a hydraulically operated hand type having an hydraulic cylinder 10 sealingly guiding a piston 1 A pin holder 12 abuts the piston 1 1 and is urged thereagainst by a compression spring 13 which is retained in a spring housing 14 attached, e.g. screwed, to hydraulic cylinder 10. The lower end of the pin head 1 rests on the pin holder 1 Z.

A fixed tool part 15 adjoins the hydraulic cylinder 10, with a pin shaft 2, or at least traction rod 3, extending therethrough. A movable tool part 1 7 is attached to the threaded end 7 of the traction rod 3 by means of a nut 1 6.

In actuating the press tool, an hydraulic pressure medium is introduced via a connection 18 into the hydraulic cylinder 10. The hydraulic pressure medium pushes the piston 1 1 back against the action of the spring 1 3 and the tool part 17 is moved against the fixed tool part 15 in its working operation.

If the thickness of the work material is too great, or the tool parts 18 and 1 7 are not properly matched, the traction rod 3 may break, especially in the region of its threaded end 7. Then, the wire 8 accommodated in the traction rod 3 will limit the displacement of the broken-off end of the traction rod 3 and its accompanying tool part 17, and thereby prevent it from flying off and causing damage or injury. Wire 8 has such extensibility as normally to be able, without itself breaking, to absorb or retrain energy released by traction pin breakage. However, even partial absorption and restraint followed by fracture could be very beneficial in reducing damage.

If desired, the extensible strip 8, while typically in the form of a wire, may also include one or more spring or plastically deformable structural parts, particularly for its attachment to the pin shaft or an adjoining part of the traction rod.

Claims (13)

Claims

1. In or for a power tool, a traction pin having a pin end part adapted for being held in said tool, a pin shaft extending from the pin end part, a traction rod connected to extend from the pin shaft and being adapted at its free end for attachment of a tool part, and extensible strip means fixed at spaced positions one to said traction rod in the region of its free end and the other to said traction rod and/or said pin sahft.

2. A traction pin according to claim 1, wherein at least the traction pin has a lengthwise extending guide to accommodate said strip means between its fixing positions.

3. A traction pin according to claim 2, where the traction rod is hollow and the strip means extends within its cavity.

4. A traction pin according to claim 2, wherein the traction rod has an exterior groove for accommodating the strip means.

5. A traction pin according to claim 2 or claim 3, wherein the strip means is at least partly accommodating in threading on said traction rod.

6. A traction pin according to any preceding claim, wherein the pin shaft has an axial blind bore that is threaded for securement therein of said traction rod by mating threads thereon.

7. A traction pin according to any preceding claim, wherein a radially disposed securing pin is operative between openings in the pin shaft and the traction rod.

8. A traction pin according to any preceding claim, wherein said stretchable strip is metal wire.

9. A traction pin according to claim 8, wherein the said wire is soldered at both of its ends to ends of said traction rod.

10. A traction pin according to any preceding claim, wherein a portion of the strip means between its fixing positions has at least one undulation.

1 A traction pin according to any preceding claim, wherein the strip means is connected at least to the traction rod and/or the pin shaft via a part of spring or plastically deformable type.

12. A traction pin substantially as herein described with reference to and as shown in Figures 1 and 2 of the accompanying drawings.

13. A power tool substantially as herein described with reference to and as shown in Figures 1 to 3 of the accompanying drawings.