Electro-mechanical release device for percussion priming of cartridges

[57] ABSTRACT

A release device for percussion priming of a propellant charge contained within a cartridge, particuarly for use in conjunction with piston-operated switchgear drives, includes a striker pin for a detonator cap that primes the cartridge. The striker pin is secured to the armature element of a holding magnet and is held in a position of rest away from the cap by magnetic attraction of the armature to a pole shoe of the magnet against a counter mechanical force created by compression of a spring. Release of the striker pin is effected by a temporary weakening of the effective magnetic field produced by the holding magnet which in turn releases the armature and striker pin assembly for movement under the force stored in the compressed spring to detonate the cap.

Claims, 1 Drawing Figure

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PATENTED OCT 2ΒΠ

3,762.087

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3,762,087

ELECTRO-MECHANICAL RELEASE DEVICE FOR PERCUSSION PRIMING OF CARTRIDGES

The present invention relates to an improved release device for percussion priming of propellant charges, particularly for switchgear drives.

For the operation of switchgear it is known to use rapid drives in which chemical energy is used to load mechanical drive pistons in the connection or disconnection direction. For this purpose it has already been proposed to use propellant charges contained in cartridges, the latter being fed from magazines and being appropriately delivered into and out of the priming chambers with the aid of a rotating drum. In this case the cartridges are primed by means of an electric fuse in the cartridge. In comparison with cartridges provided with a detonator cap adapted to be operated mechanically by means of a striker pin, however, cartridges of the electric fuse type are very expensive.

The problem underlying the invention consists in providing a simple, inexpensive release device for priming cartridges provided with detonator caps, wherein at the same time a short inherent response time of the release device can be achieved. According to the invention, this is achieved through the fact that the striker pin which, in the position of rest, is under the action of a stressed striker spring, is held in position by a holding magnet with the aid of an armature connected to the striker pin, the dropping of the armature being effected through a brief weakening of the holding magnet field. Particularly for circuit-breaker drives with high switching frequency, it is possible in this way to use cartridges provided with inexpensive detonator caps operated mechanically by a striker pin, instead of cartridges provided with more expensive electric detonator caps.

A preferred embodiment of the invention will now be described and is illustrated in the accompanying drawing the single figure of which is a view of the detonator assembly in central longitudinal section with certain parts being shown in elevation.

With reference now to the drawing, 1 designates a holding magnet I which produces the magnetic force necessary to hold the strike pin assembly in a rest position until weakened by creation of a counter magnetic force. Magnet 1 of the permanent type is provided with a soft iron pole shoe la secured thereto. Attractable to the shoe la is an armature 3 which is mounted for guided longitudinal movement within a central opening provided in an iron base plate 10, and depending from this armature is a striker pin 6 surrounded by and spaced from a sleeve 3α provided at its lower end with a flange 3b. Located between flange 3b and the underside of base plate 10 is a helical compression spring 2 which is in a compressed state when armature 3 is held by magnetic force in its upward, rest position against the pole shoe la.

A tubular housing 14 depending from the lower face of base plate 10 serves to enclose the striker pin assembly and also serves to support at its lower end a mount 9 having a bore therein aligned with the striker pin 6 for receiving the end portion of a cartridge 8 and its detonator cap 7. The chemical explosive forces released into space 15 by firing the cartridge 8 serve to drive pistons, not illustrated, which are mechanically coupled to and actuate the control mechanism of the electrical switchgear.

The mount 9 includes an upstanding cylindrical bored part 9α which extends partly within the sleeve 3α and receives the striker pin 6 so as to properly guide the latter in its longitudinal movement between the upward rest position depicted in the drawing and the lower released position in which the end of pin 6 strikes against and mechanically detonates the primer cap 7. Mount 9 is also provided with a passage 9b leading from space 15 into the lower end of guide part 9α so that part of the explosion gases in a pressurized state pass through this passage and come beneath the lower end of the striker pin 6.

As previously explained, the striker pin 6 and its armature 3 are held in the rest position due to the attractive force produced by the holding magnet 1. The path of the magnetic flux produced by magnet 1 passes downward from pole shoe la through armature 10, then laterally outward through base plate 10, then upward through an iron wall 11 which houses the magnet assembly and then laterally inward through an iron closure cap 12 which contacts the upper side of magnet 1. The lower portion of pole shoe la tapers inwardly to a central circular end face of the same diameter as armature 3 which is held to, or released from it. An annular support 13 of non-magnetic material resting upon the base plate 10 serves as a support for the shoe la, and support 13 in conjunction with closure cap 12 and base plate 10 serve to hold the magnet 1 and its shoe la in a fixed position.

Surrounding magnet 1 are two release coils 4 and 5 provided for effecting a reduction in magnetic attractive force necessary to release armature 3. If a control voltage pulse is applied briefly to one of these two coils (one always functions as a reserve), it generates a magnetic flux which has a direction counter to that produced by permanent magnet 1 with the result that the net attractive magnetic flux acting upon armature 3 is weakened to the point where pole shoe la is no longer able to hold armature 3 against the counter force stored mechanically within the compressed spring 2 with the result that armature 3 releases and striker pin 6 is driven downwardly to detonate the primer cap 7 and fire cartridge 8.

As previously explained, the explosion gases thus produced in space 15 which can be imagined as a cylinder drive pistons which in turn actuate the control mechanism of the switchgear, or perform some other desired function. Part of the explosion gases are also returned through passage 9b into the lower end of the cylindrical guide part 9α at a point beneath the striker pin 6 and push the latter together with armature 3 back to the rest position, recompressing spring 2, and holding the armature against pole shoe la until the counter flux which had been produced by the brief pulse of current applied to either coil 4 or coil 5 has subsided to a value at which the permanent flux is once more sufficient to hold the armature in its attracted position.