Fuse Contacts

Abstract

An electrical contact for a cartridge fuse, the contact being stamped and formed from resilient sheet metal and comprising two superimposed strips forming a composite leg having a mounting foot at one end, in which the mounting foot has a surface facing generally away from the contact portion for engagement with an upper surface of a mounting board, and an axis of a cone of the contact converging with the plane in which the surface of the mounting foot is disposed at a location spaced from a side of the contact at which the end portions are located.

Description

This invention relates to a contact for a cartridge fuse having conical end caps formed from electrically conductive metal.

The present invention is a unitary electrical contact for a cartridge fuse having conical conductive ends, the contact being stamped and formed from resilient sheet metal and comprising two superposed strips forming a composite leg having the mounting foot at one end, the strips being bent apart at the other end and being integrally joined at the other end by a U channel receptacle having two spaced walls joined by a bight, the channel extending generally along the axis of the composite leg with the walls located in planes generally parallel to the plane of the composite leg, each channel wall being bent at an end portion remote from the bight away from the other wall into the form of a part surface of a cone the apex of which is located between the bight and the end portions and the axis of which extends from the apex away from the bight and between the channel walls, the two part-conical surfaces forming a contact portion.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings in which:

FIG. 1 is a perspective view of two contacts according to the invention, a cartridge fuse and a printed circuit board prior to assembly of the various components;

FIG. 2 is a view looking in the direction of arrow A in FIG. 1, of one of the contacts of FIG. 1 mounted on the printed circuit board;

FIG. 3 is a view looking in the direction of the arrow B in FIG. 1 of the two contacts of FIG. 1 mounted on the printed circuit board prior to full insertion of a fuse; and

FIG. 4 is a view similar to FIG. 3 but showing the contacts after full insertion of the fuse.

Each contact 10 is stamped from resilient sheet metal and then bent into the form shown. A central portion comprises two superposed strips 11 forming a composite leg 12. The strips 11 are bent apart at the upper end of the composite leg to form two halves of a stop 13 the purpose of which is explained below. The strips 11 are integrally joined at the upper end by a U channel receptacle 15 having two spaced walls 16 joined by a bight 17, the channel extending generally along the axis of the leg 12 with the walls 16 located in planes generally parallel to the plane of the leg 12. The free end portion 19 of each channel wall 16 is bent away from the other wall at 20 into the form of a part surface of a cone the apex of which is located between the bight 17 and the free ends 19 of the channel walls 16 and the axis 21 of which extends from the apex away from the bight 17 and generally parallel to and between the walls 16. The two part-conical surfaces 20 define together with the stop 13 a contact portion for receiving an end cap of a fuse as described below. The free ends 19 of the channel walls 16 are bent away from each other at portions 22 remote from the leg 12 to form a flared mouth best seen in FIG. 2.

The strips 11 are bent apart at 23 the lower end of the leg 12 and are integrally joined at the lower end by a U channel 24 generally aligned with the receptacle 15. The channel 24 has a bight 25 joining two spaced walls 26 which have free ends 27 projecting laterally beyond the leg 12. The free lower ends of the strips 11 are formed as spaced tabs 28 extending in directions parallel to the leg 12.

To mount a pair of contacts 10 on a printed circuit board 29 two pairs of spaced through holes 30 are provided in the printed circuit board. Each contact 10 is applied to the upper surface 31 of the board 29 with its two tabs 28 received through respective holes 30 and with the lower edge 32 of the U channel 24 hard against the upper surface 31 as shown most clearly in FIGS. 3 and 4. The tabs 28 are then bent upwardly and towards each other against the lower surface 33 of the board as shown in FIG. 2 after which the tabs are soldered as shown at 34 to conductors on the lower surface 33. As shown in FIG. 3 the axes 21 about which the part-conical surfaces 20 are generated converge between the two contacts 10 in a direction towards the board 29. This is brought about because the lower edge 32 of the U channel 24 of each contact 10 is in a plane which converges with the axis 21 of the associated part conical surfaces 20 at the side of the contact at which the receptacle 15 opens into.

FIG. 1 shows a conventional form of cartridge fuse 35 which is formed with an insulating body 36 and two conical conductive ends 37 joined together by a fusible conductive strip 38.

Insertion of the fuse 35 into the receptacles 15 of the pair of contacts 10 will now be described. The fuse 35 is inclined with one end 37 nearer the board 28 than the other, and the one end 37 is introduced into a receptacle 15. In order to insert the other end 37 of the fuse 15 in the other contact 10, the other end 37 (the right-hand end as seen in FIG. 3) is forced towards the board into the flared mouth of the receptacle 15 of the right-hand contact 10, and the channel walls 16 flex apart allowing the other end 37 to snap into engagement with the part-conical surfaces 20 and the roof 13. As the other end 37 is being forced into position the receptacles 15 of the two contacts 10 are forced apart by flexure of each contact about the parts 23 and 13 joining the U channel 24 and the receptacle 15, respectively, to the leg 12 to take up the position shown in FIG. 4 on full insertion of the fuse 35. In this position the two conical axes 21 and the fuse axis are aligned parallel to the board 29. Thus the conical ends 37 are perfectly seated in the respective receptacles and the outward flexure of the contacts ensures a strong contact force and pull-out force.

In practice the receptacles may be manufactured in strip form and applied by automatic insertion tooling to the printed circuit boards.

Claims

What is claimed is:

1. A unitary electrical contact for a cartridge fuse having conical conductive ends, the contact being stamped and formed from resilient sheet metal and comprising two superposed strips having a contiguous portion forming a composite leg disposed in a first plane and having a mounting foot at one end, the strips being bent apart at the other end and being integrally joined at the other end by a U channel receptacle having two spaced walls joined by a bight, the channel extending generally along the axis of the composite leg with the walls located in second and third planes generally parallel to the first plane, each channel wall being bent at an end portion remote from the bight away from the other wall into the form of a part surface of a cone the apex of which is located between the bight and the end portions and the axis of which extends from the apex away from the bight and between the channel walls, the two part-conical surfaces forming a contact portion.

2. A contact according to claim 1, in which the mounting foot has a surface disposed in a fourth plane perpendicular to the first plane, the surface facing generally away from the contact portion for engagement with the upper surface of a mounting board, and the axis of the cone converges with the fourth plane in which the surface of the mounting foot is disposed at a location spaced from a side of the contact at which the end portions are located.

3. A contact according to claim 1, in which the end portions of the channel walls are bent away from each other at portions remote from the leg to form a flared mouth.

4. A contact according to claim 1, in which the strips are bent apart at the one end by a U channel generally aligned with the receptacle, the channel having a bight joining two spaced walls which have free ends projecting laterally beyond the composite leg, the free ends of the strips being formed as spaced tabs extending parallel to the composite leg.