Switching devices

Details Switching devices Switching devices

1996-02-12

1997-12-02

Donovan, Lincoln

Electricity: magnetically operated switches, magnets, and electr

Electromagnetically actuated switches

Polarity-responsive

335128, H01H 5122

Patent

active

056940998

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to switching devices, such as relays, which incorporate solenoid actuators.


BACKGROUND OF THE INVENTION

In International (PCT) Publication No WO 91/19314 there is described and claimed a switching device comprising a solenoid actuator, a lever made of electrically insulating material pivotally mounted for movement by the actuator, a flexible switch contact bearing element having a movable contact at one end for engagement with a fixed contact, and connection means connecting the lever to the contact bearing element to move the contacts between open and closed states.
Whilst such a switching device operates satisfactorily in normal applications, it has been found that under extremely high current conditions, eg short-curcuit conditions, a repulsion force is generated which tends to part the pairs of contacts, which may cause serious damage to the switching device.
It is an object of the present invention to provide an improved switching device without the foregoing disadvantage.


SUMMARY OF THE INVENTION

According to the present invention there is provided a switching device comprising a solenoid actuator, a first terminal attached to a first bus-bar on which is mounted a flexible switch blade operable by the actuator and having a movable contact at its free end, and a second terminal connected to a fixed contact with which the movable contact is engageable, the arrangement being such that when in use the device is in the ON condition the resultant current flow produces an electrodynamic force between the blade and the first bus-bar which tends to maintain the contacts in engagement.
In an advantageous arrangement in accordance with the invention, the first and second terminals of the switching device, together with the related contact sets and bus-bars, together referred to hereinafter as the "switching assembly" are physically arranged within the device such that under conditions of high (eg short-circuit) current in the external circuit switched by the device, the current flow through the switching assembly is able to reduce repulsion forces occurring between the fixed and movable contacts and to cause the force applied to close the contacts to be increased electrodynamically.
In this way inadvertent opening of the contacts under high current or short-circuit conditions, which could lead to arcing and potential destruction of the switching device, may be largely avoided.


BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention, given by way of example only, will now be described with reference to the accompanying drawings in which:
FIGS. 1A to 1C together show a plan view and two scrap views of a known switching device;
FIG. 2 shows a perspective view of an improved switching assembly (as hereinbefore defined) for a device of the general type shown in FIG. 1; and
FIG. 3 shows a diagrammatic illustration of a device of the general type shown in FIG. 1 incorporating an improved switching assembly.
Referring first to FIGS. 1A and 1B, there is shown a known single-pole power relay or contactor switch configured for switching industrial or domestic electrical loads, typically at 100 A and 250 V AC.
The relay is housed in a split moulded case 70 open initially for assembly and adjustment, and then closed to provide protection from shock and from the ingress of dust. The case is shown open in the drawing.
One power terminal 72 comprises a heavy metallic block with integral fins which engage positively in slots in case 70. Connection is made to external wiring by means of a bolt 74 engaging in the threaded hole in the terminal end face.
The moving part of the relay switch comprises a high conductivity blade 76 which is partly reduced in section towards its fixed end 76A to create flexibility and ease of movement. The fixed end of the blade is suitably attached by welding, screwing or rivetting to the inside face of terminal 72. A switching contact 78 attached to the free end of blade 76 is made of an alloy suitable for the magnitude of the switc

REFERENCES:
patent: 5227750 (1993-07-01), Connell et al.
patent: 5515019 (1996-05-01), Schedele

Affiliated with

Also associated with

Rating

Switching devices does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Switching devices, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Switching devices will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-805178