GB2058266A

GB2058266A - Fitting for attachment to perforated members

Info

Publication number: GB2058266A
Application number: GB7931235A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-09-08
Filing date: 1979-09-08
Publication date: 1981-04-08
Also published as: DE3033571A1

Abstract

A fitting for attachment to a perforated member (12a) comprises a headed deformable bush (11a) which can be inserted into a perforation (21a) in the member (12a) and a spigot (10a) which is force fitted into a central hole (20a) in the bush (11a). To prevent withdrawal of the spigot (10a) from the central hole (20a), the spigot (10a) has at least two conical enlargements (24, 25) of greater diameter than the central hole (20a) of the bush (11a), the spigot (10a) being forced into the central hole (20a) of the bush (11a), with the cones (24, 25) pointing in the direction of insertion, until the conical enlargements (24, 25) lie beyond the perforation (21a) in the member (12a) and expand the projecting end of the bush (11a). A flange (17a) on the spigot (10a) prevents it being forced too far into the bush (11a). <IMAGE>

Description

SPECIFICATION Fitting for attachment to perforated members The present invention relates to fittings for attachment to perforated members.

Our earlier U.K. Patent No. 786,862 discloses a fitting for attachment to a perforated member which comprises a bush of deformable material which can be pushed part-way through a hole in the member until an external projection of the bush comes up against the edge of the hole on one side of the member and one end of the bush projects beyond the hole on the other side of the member, a spigot having an enlargement bigger than the bore of the bush which can be forced into the bore of the bush until the enlargement lies beyond the hole in the member and expands the projecting end of the bush to prevent withdrawal of the bush from the hole, in which position at least one end of the spigot projects from the bush, and a flange or shoulder on the spigot to prevent it being forced too far onto the bush.

Such devices, known in the art as Barb (Registered Trade Mark) Cone-Lock insulators, have found widespread commercial application over a number of years. In these devices, the enlargement of the spigot which expands the projecting end of the bush is of conical or wedgeshaped form with the cone pointing in the direction of insertion of the spigot. One problem occasionally incurred with the known devices, however, is that, if the spigot is subjected in use to lateral forces, the spigot can be tilted relative to the bush, in which event the extraction force necessary to withdraw the spigot from the bush, in a generally axial direction opposite to that in which it was originally inserted, is found to be somewhat reduced compared with normal.It is believed that this is at least in part due to the reduction in contact area between the enlargement and the adjacent surface of the bore in the bush when tilting has occurred.

It is an objective of the present invention to seek a means of preventing, or at least substantially lowering this reduction in the extraction force which occurs upon the spigot being subjected to lateral tilting forces.

It has been discovered by experiment that a substantial lowering of the reduction in the extraction force can be achieved by increasing the number of conical enlargements on the spigot. It is believed that this is effective due to the relatively high contact area which is maintained with the internal surfaces of the bush bore.

In accordance with the present invention, therefore, there is provided a fitting for attachment to a perforated member which comprises a bush of deformable material which can be pushed partway through a hole in the member until an external projection of the bush comes up against the edge of the hole in one side of the member and one end of the bush projects beyond the hole on the other side of the member, a spigot having at least two conical enlargements thereon of greater diameter than the bore of the bush which can be forced into the bore of the bush, with the cones pointing in the direction of insertion, until the conical enlargements lie beyond the hole in the member and expand the projecting end of the bush to prevent withdrawal of the bush from the hole, in which position at least one end of the spigot projects from the bush, and a flange or shoulder on the spigot to prevent it being forced too far into the bush.

Preferably, two or three such conical enlargements are provided.

The invention is described further hereinafter, by way of example, with reference to the accompanying drawings, in which: - Fig. 1 is a sectional view through our known attachment, shown mounted in a perforated member; Fig. 2 is a sectional view through one embodiment of a fitting in accordance with the present invention; and Figs. 3a to 3c are diagrammatic perspective views illustrating the manner in which the new fitting can improve the performance of the known fitting.

Fig. 1 illustrates a known fitting which corresponds substantially to Fig. 2 of our earlier U.K. Patent No. 786,862. The fitting shown in Fig. 1 comprises a spigot 10 and a bush 11 mounted in a perforated member 12, such as a printed circuit board, to constitute an insulated stand-off terminal. The spigot 10 is made of metal and is of circular cross-section. It comprises a central portion 14 and an end portion 1 5 of the same diameter. The other end is formed with an enlargement 1 6 in the form of a cone whose maximum diameter is somewhat greater than the diameter of said central and end portions 14, 1 5.

Between the portions 14 and 15 is a further conical formation 17 of maximum diameter somewhat larger than that of the conical formation 1 6.

The bush 11 is made of a deformable insulating material, such as polytetrafluoroethylene, and comprises a cylindrical portion 1 8 and a flange 19.

A bore 20 of approximately the same diameter as the central portion 14 of the spigot extends right through the bush 11.

The perforated member 12 is provided with a hole 21 of approximately the same diameter as the cylindrical portion 1 8 of the bush. The iength of the cylindrical portion 18 of the bush is somewhat greater than the length of the hole 21 so that, when the bush is inserted into the hole with the flange 1 9 resting against the edge of the hole 21 on one side of the member 12, the other end of the bush will project beyond the hole 21 on the other side of the member 12.

When the bush has been inserted into this position, the spigot 10 is pushed into the bore 20 of the bush until it occupies the position shown in Fig. 1. The bush, being made of a deformable material, permits the insertion of the spigot in this manner.

When the spigot has been so inserted, the conical enlargement 1 6 expands the projecting end of the bush into a bulb-like form as shown at 22, which holds the bush firmly in place. The formation 17, which is forced partly into the other end of the bush, increases the firmness of the fixing and prevents any further significant longitudinal movement of the spigot in the bush.

Conductors can then be attached to the projecting end 1 5 of the spigot, for example by soldering. When the device is to be used as a leadthrough terminal, the end of the spigot carrying the conical enlargement 16 can be extended, as shown at 13 in Figs. 1 and 2 of U.K. Specification No. 786,862, to provide another connection point on the other side of the member 12.

Fig. 2 shows a fitting modified in accordance with the present invention. Those parts which are identical to the fitting of Fig. 1 are given the same reference numbers with the addition of a subscript "a". The principal difference is that the single conical formation 1 6 of Fig. 1 is replaced by a formation having, in addition to a conical end portion 1 6a, two frusto-conical portions 24, 25 adjacent thereto. In other embodiments only one such frusto-conical portion, or three or more, could be provided.

The advantage provided by the new arrangement is that it has a higher resistance to withdrawal of the spigot from the bush in the vertical direction as viewed in the drawings. It is believed that this can be explained as follows: As shown in Fig. 3a if one has a single conical enlargement, at the region of its maximum diameter, i.e. at the circular edge of the cone, when the spigot is axially aligned with the bush there is a line contact with the bush bore throughout 3600. However, should the spigot be tilted considerably relative to the bush bore, the area of contact around the cone edge can be reduced and in an extreme condition could be only at two points A and B. However, as illustrated in Fig. 3c, when two or more conical edges are present, the possibility of tilting of the spigot relative to the bush bore is substantially reduced so that contact around the whole edge of each cone is ensured. Consequently, substantially no reduction in the extraction force is experienced with such fittings irrespective of the lateral forces to which the spigot might be subjected in use.

Claims

1. A fitting for attachment to a perforated member which comprises a bush of deformable material which can be pushed part-way through a hole in the member until an external projection of the bush comes up against the edge of the hole in one side of the member and one end of the bush projects beyond the hole on the other side of the member, a spigot having at least two conical enlargements thereon of greater diameter than the bore of the bush which can be forced into the bore of the bush, with the cones pointing in the direction of insertion, until the conical enlargements lie beyond the hole in the member and expand the projecting end of the bush to prevent withdrawal of the bush from the hole, in which position at least one end of the spigot projects from the bush, and a flange or shoulder on the spigot to prevent it being forced too far into the bush.

2. A fitting as claimed in claim 1 in which there are two or three said conical enlargements on the spigot.

3. A fitting substantially as hereinbefore described with reference to and as illustrated in Fig. 2 of the accompanying drawings.