GB2048628A - Fastener disassembly tool - Google Patents

Abstract

A tool for the disassembly of a fastener 13 including a tubular thermoplastic locking sleeve 16 comprises a tubular anvil 21 and an electrical heating element 23 therefor. The heated anvil is applied to one end of the thermoplastic sleeve and pressure is exerted, to soften the thermoplastic material and displace it. The bore 27 of the tubular anvil is connected by passages 31, 32 to openings 28 spaced axially behind the anvil, to allow the escape of softened thermoplastic material from the bore. The bore may be offset from or at an angle to the body of the tool so that it is open at both ends, allowing a pushrod to be pushed through it to help disassemble the fastener. <IMAGE>

Description

SPECIFICATION Fastener disassembly tool The present invention relates to a tool for disas sembly of a fastener incorporating annular or tubu lar engaging means which is also thermoplastic. One example of such a fastener is described in our British Patent Specification No. 1 538423 and is commercially available in the United Kingdom under the Registered Trade Mark AVTAINER. Essentially this fastener comprises a rigid tubular shell carrying tubular engaging means in the form of a nylon sleeve, and a pin having annular barbs which are embedded in the nylon sleeve to engage therewith.

In practice it is sometimes required to disassemble the installed fastener by separating the shell and the pin.

The present invention provides a tool for disassembly of a fastener incorporating annular or tubular thermoplastic engaging means, which tool comprises an annular or tubular anvil for contacting the engaging means, and heating means for heating the anvil, whereby when the heated anvil is applied the thermoplastic engaging means the latter is thereby softened sufficiently to disassemble the fastener.

Preferably the annular or tubular anvil is provided with an aperture for the escape of softened material forced into the anvil when the latter is applied to the engaging means.

Preferably the escape aperture is provided at the opposite end of the anvil to that end (the mouth end) which, in use of the tool, first contacts the fastener.

In one embodiment of the invention, the annular or tubular anvil has a bore of uniform diameter extending completely through it, so that the escape aperture is provided by the end of the bore remote from the mouth end. In that case the tool may include a plunger or pushrod adapted to be pushed through the anvil bore to assist in disassembly of a fastener.

Preferably the arrangement is such that, in use of the tool, softened material emerges from the tool at a position remote from a workpiece for which a fastener is being removed.

In another embodiment of the invention, the escape aperture in the anvil is connected by one or more passages to one or more openings, spaced away from the anvil, from which softened material may emerge from the tool. It may be that the said passages comprise a first passage extending rearwardly from the anvil bore and a second passage transverse thereto and connecting the first passage to at least one opening as aforesaid.

Preferably the anvil is adapted to engage a part of the fastener released by the disengagement thereof so as to assist in removing the said part.

The invention includes the combination with a fastener incorporating annular or tubular thermoplastic engaging means of a tool for disassembly thereof as aforesaid.

The invention also provides a method of disengag ing or unlocking a fastener incorporating annular or tubular thermoplastic engaging means, comprising applying a heated annular ortubular anvil to the engaging means so as to soften the latter at least sufficiently to disengage or unlock the fastener.

The invention may include the step of withdrawing the anvil from the fastener with a part of the fastener which has been released by the softening of the engaging means carried by the anvil. It may be that softened material assists in retention of the said part to the anvil.

The invention may include the step of assisting in the disassembly of the fastener by pushing on a part of the fastener with a part of the anvil. Alternatively the invention may include the step of urging a plunger or pushrod through the anvil bore in order to assist in disassembly of a fastener.

A specific embodiment of the invention together with two modifications thereof will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 shows, partially in section, a fastener disassembly tool about to be applied to a fastener installed in a workpiece; Figure 2 is an end elevation on the line II - II of Figure 1; Figures 3 and 4 show successive stages in the use of the tool; and Figures 5 and 6 show alternative optional modifications of the tool.

In this example the fastener is shown installed in a workpiece comprising a sheet of plywood 11 and a metal frame member 12, to secure them together.

The fastener 13 comprises essentially a steel pin 14 and a steel shell 15, both pin and shell having radially enlarged heads 8 and 9 respectively for contacting and clamping the workpiece (i.e. sheet 11 and frame 12). The shell 15 carries resilient engaging means in the form of a nylon sleeve 16, and the pin carries engaging means in the form of annular barbs 17. To install the fastener, a suitable hole 18 is drilled through the workpiece, the pin 14 inserted from one end of the hole, and the shell inserted from the other.

The barbed part of the pin enters the tubular nylon sleeve inside the shell, and force is applied to draw the two parts of the fastener together until the enlarged head 8 on the pin and the enlarged head 9 on the shell clamp the sheet 11 and frame 12 tightly together. The barbs 17 are embedded in the nylon sleeve and because of their asymmetric shape lock the pin against removal from the shell. In practice one advantage of the fastener of this example is that it is very difficult to remove, thus making it nearly "tamper-proof". However it is sometimes necessary to undo an installed fastener, e.g. in order to repair the structure in which the fastener is installed.

The tool of the present example is shown in Figures 1 and 2 and comprises a tubular anvil 21 formed as the forward end of a copper member 22 of circular cross-section, and an electrical heating element indicated schematically at 23.

The anvil is positioned centrally on the front end of the member 22 leaving an annular shoulder 30 sur rounding the rear of the anvil. The anvil has an annu lar front end face 20, and the junction between its rear outer end and the shoulder 30 is radiussed.

The heating element is embedded in a body 24, around a bore at its front end which receives a major part of the length of the copper member. To the rear end of the body is secured a handle 25 of low ther mal conductivity by which an operator can grasps the tool. The power lead 26 for the heating element 23 passes through the handle 25.

The tubular anvil 21 is made with internal and external diameters such as to fit as closely as possible between the barbed portion ofthe pin, and the shell 15, of the fastener 13 to be disassembled. The internal bore 27 of the tubular anvil is, in this example, sufficiently long to accommodate the barbed portion of the pin, as will be described later. The anvil is provided with an aperture 29 in the rear or inner end 33 of its bore, which is connected by an axial passage 31 and a cross passage 32 to two openings 28 on the outside of the member 22. The openings 28 are spaced axially along the member behind the rear end of the anvil. The fact that the cylindrical wall ofthe anvil is not perforated by an aperture or passage meansthatthe anvil is not thereby weakened.

The method of use of the tool is as follows: The electric power supply to the heater element 23 is switched on and the anvil allowed to come to a suitable operating temperature, the tool being preferably provided with a thermostat to maintain the correct temperature.

The tool is offered up to the installed fastener in the alignment illustrated in Figure 1, i.e. with the end 20 of the anvil 21 opposite and facing the end of the nylon sleeve 16 of the fastener. The tool is advanced axially towards the fastener. Entry of the anvil into the fastener is assisted by the flare inside the shell head 9. The front end face of the heated anvil then contacts the outer end of the nylon sleeve 16, and the operator maintains pressure on the tool. The nylon sleeve is progressively softened, due to the application of heatthereto by the anvil. The anvil advances between the pin barbed portion and the shell 15, displacing softened nylon material backwards both inside and outside the anvil. Material flowing between the outside of the anvil and the inside of the shell can emerge without restriction.

However, inside the anvil softened nylon material 43 fills the bore 27 and is forced, by the barbed pin portion advancing into the bore, through the aperture 29, along bores 31 and 32 and out through openings 28. This is illustrated in Figure 3, where the anvil 21 is entered about half-way into the length of the nylon sleeve 16. The operator maintains pressure on the tool to press the anvil as far as possible into the nylon sleeve 16, to soften and displace the part of the nylon sleeve around the barbed portion 17, of the pin, thus releasing the shell 15 from the pin 14.

Since, in this example, the length of the stem inside the shell is greater than the length of the anvil bore 27, the inner end wall 33 of the anvil bore abuts the free end of the pin stem, and the thrust on the tool pushes the pin 14 slightly out of the workpiece, until the anvil shoulder 30 abuts the fastener shell head 9.

It should be noted that the openings 28 through which the softened nylon 43 emerges are positioned sufficiently far away from the anvil shoulder 30 to keep the softened nylon away from the workpiece, which might be marked or contaminated thereby.

The operator now withdraws the tool from the workpiece, where upon the sleeve 15 can be removed from the hole 18 through the workpiece.

Since the anvil is a close fit within the sleeve, the anvil may engage the sleeve sufficiently to remove the sleeve with the anvil, as illustrated in Figure 4. In addition, softened nylon material between the anvil and the sleeve may cause some adhesion of the sleeve to the anvil.

Figure 5 shows one optional modification in the arrangement of the anvil on the tool. In this modification the anvil axis is still parallel to the body of the tool but is offset therefrom, to facilitate access to fasteners with restricted access e.g. in corners. The copper member 22 is formed with a transverse extention 51 at its front end, the anvil 21 projecting forwardly from this at a position offset outside the body 24 of the tool. The anvil bore 27 extends at uniform diameter completely through the extension 51, the rear end of the bore providing the escape aperture 29 for softened material. Furthermore, a pushrod or plunger 52 may be provided, which, when the tool is in a position corresponding to that illustrated in Figure 3, may be urged forwardly through the bore 27 to help push out the pin of the fastener.

An alternative optional modification of the arrangement of the anvil is shown in Figure 6, in which the anvil 21 is positioned at right angles to the tool body and extends sideways from the copper member 22. The anvil bore 27 extends at uniform diameter completely across the member 22, the rear end of the bore providing the escape aperture 29 for softened material. Again, a plunger or pushrod may be provided, which when the tool is in a position corresponding to that illustrated in Figure 3, may be urged through the bore 27 to help push out the pin of the fastener.

The invention is not restricted to the details of the foregoing example and modifications thereof.

Claims (17)

1. A tool for disassembly of a fastener incorporating annular or tubular thermoplastic engaging means, which tool comprises: an annular or tubular anvil for contacting the engaging means and heating means for heating the anvil, whereby when the heated anvil is applied the thermoplastic engaging means the latter is thereby softened sufficiently to disassemble the fastener.

2. A tool as claimed in Claim 1, in which the annular or tubular anvil is provided with an aperture for the escape of softened material forced into the anvil when the latter is applied to the engaging means.

3. A tool as claimed in Claim 2, in which the escape aperture is provided at the opposite end of the anvil to that end (the mouth end) which, in use of the tool, first contacts the fastener.

4. Atool as claimed in Claim 3, in which the annularortubularanvil has a bore of uniform diameter extending completely through it, so that the escape aperture is provided by the end of the bore remote from the mouth end.

5. A tool as claimed in Claim 4, including a plunger or pushrod adapted to be pushed through the anvil bore to assist in disassembly of a fastener.

6. A tool as claimed in Claim 2, in which the arrangement is such that, in use of the tool, softened material emerges from the tool at a position remote from a workpiece from which a fastener is being removed.

7. A tool as claimed in Claim 2, in which the escape aperture in the anvil is connected by one or more passages to one or more openings, spaced away from the anvil, from which softened material may emerge from the tool.

8. A tool as claimed in Claim 7, in which the said passages comprise a first passage extending rearwardly from the anvil bore and a second passage transverse thereto and connecting the first passage to at least one opening as aforesaid.

9. Atool as claimed in any of the preceding claims, in which the anvil is adapted to engage a part of the fastener released by the disengagement thereof so as to assist in removing the said part.

10. A tool for disengaging or unlocking a fastener, substantially as hereinbefore described with reference to, and illustrated in, and accompanying drawings.

11. The combination with a fastener incorporating annular or tubular thermoplastic engaging means of a tool for disassembly thereof as claimed in any one of the preceding claims.

12. A method of disengaging or unlocking a fastener incorporatong annular or tubular thermoplastic engaging means, comprising applying a heated annular or tubular anvil to the engaging means so as to soften the latter at least sufficiently to disengage or unlock the fastener.

13. A method as claimed in Claim 12, including the step of withdrawing the anvil from the fastener with a part of the fastener which has been released by the softening of the engaging means carried by the anvil.

14. A method as claimed in Claim 13, in which softened material assists in retention ofthe said part to the anvil.

15. A method as claimed in Claim 12, including the step of assisting in the disassembly of the fastener by pushing on a part of the fastener with a part of the anvil.

16. A method as claimed in Claim 12, including the step of urging a plunger or pushrod through the anvil bore in orderto assist in disassemblyofa fastener.

17. A method of disengaging or unlocking a fastener, substantially as hereinbefore described with reference to, and illustrated in, the accompanying drawings.