US2514947A - Electric switch - Google Patents

Description

July 11, 1950 w. T. GRAY 2,514,947

ELECTRIC swncn Filed Sept. 8; 1945 Inventor William T. rag

His Attorney.

Patented July 11, 1950 ELECTRIC swrrcn William Tan Gray, Altrincham, England, assignor, by mesne assignments, to General Electrlc Company, a corporation of New York Application September 8, 1945, Serial No. 615,134; In Great Britain October 18, 1944 2 Claims.

This invention relates to electric switches whose contacts, are adapted to be actuated variantly with regard to magnitude and rate of application.

For example, switches used to effect speed control of traction motors are commonly operated by cams on a cam shaft. In order to provide quick make and break, the cam shaft must be moved rapidly from one notch to the next and then rapidly retarded to prevent overshooting. Furthermore, in conventional arrangements it is necessary to provide for extended movement of the cam shaft between adjacent notches and this limits the number of switches which can be controlled from a shaft of given diameter. In addition, special arrangements are required for insuring proper registration with the several notches and in existing equipments there is ap preciable wear and tear on the operating parts due to the above-mentioned required rapid movement and retardation of the cam shaft.

One of the objects ofthe present invention is to provide switching arrangements which can be applied for achieving sequential switching, more particularly in traction control equipment, without the above mentioned drawbacks involved with hitherto known arrangements of cam-operated switches.

However, in its broader aspects the invention is not limited in application to switching arrangements for traction control equipment, nor indeed to sequential switching, its principles being eminently capable of wider application, namely in respect of an individual electric switch, whatever its use and whether of large or small capacity.

According to the present invention one of the contacts of an electric switch is associated with spring means and an electromagnet. When controlling force is applied to effect actuation of the contact, the electromagnet is first energized to restrain movement of the contact while stress is being built up in the spring means, and then the magnet is deenergized to permit rapid contact movement due to the release of the spring stressed member.

There will occur to those skilled in the art various modifications which do not depart from the broader aspects of my invention which ll aim to cover in the appended claims.

My invention will be fully understood and its objects and advantages further appreciated by referring now to the following detailed specification taken in conjunction with the following drawing, in which Fig i represents diagram= 2 matically an electric switch embodying my invention; and Figs. 2 and 3 are plan and section side elevations, respectively, of a modified form of electromagnet suitable for use in connection with the invention.

In one convenient embodiment of the invention which will now be described by way of example, a movable contact 2' for cooperating with a relatively stationary contact 2 is carried at or adjacent to one end of a lever or switch member mounted intermediately on a pivot 4 and attached at its other end to an armature 5 movable in an air gap between two poles 8 and T of an electromagnet 8; the lever 3 may conveniently be bifurcated so as to embrace opposite sides of a ectangular block of iron constituting the armature, as shown in detail at Fig. 3'. The pivot #3 supports an L-shaped operating member 9 whichconveniently extends for at least part of its length substantially parallel to, and alongside, that part or the contact-carrying lever lying between the pivot and the contact. It is to this member 8 that controlling force will be applied in any suitable manner as for example by cam means, when the switch contacts are desired to be actuated.

Interposed between the operating member 9 and the contact-carrying lever 3, and conveniently centered on a. transversely-extending rod Hi carried by, but movable relatively to the memher 9, is a helical spring ll engaged at one end with the member 9 whilst its other end engages with an enlargement of or collar i2 attached to the rod to. In the normal position of the contact-carrying member 3 corresponding to the contacts being fully open the enlargement or collar I2 is just clear of the contact-carrying lever 3. Mechanically connected to the operating member 9' is a contact segment (3 conveniently of arcuate form with which cooperates a relatively stationery finger or like contact l4 which latter is normally disengaged from the contact segment it" when the contact-carryig lever 3 is in the position corresponding to the main switch contacts being fully opened. The contact segment and the cooperating contact finger it constitute an auxiliary switch controlling energization of the electromagnet 8, and for this purpose they are connected in circuit with the coil of the electromagnet and to a source of current.

In use, assuming that the main switch contacts 5 and 2. are fully opened the auxiliary switch it, it will be opened, and accordingly the electromagnet deenergized. In the corresponding pcsition of the contact-carrying lever 3 the armature 5 attached thereto will lie at or adjacent to the pole 6 of the electromagnet 8. If now it is desired to close the contacts, force will be applied to the aforesaid operating member 9, as by a cam l6 actuated by a handle 11. The initial displacement of the member 9 about the pivot 4 will result in movement of the contact segment l3 relatively to the cooperating finger l4 accordingly to close the auxiliary switch and so cause the electromagnet 8 to become energized. As a result the electromagnet armature 5 will be held against the cooperating pole 6 of the electromagnet, so that the contact-carrying lever 3 is restrained from rotating in the direction to carry its contact I towards the relatively stationary contact 2. Under the force applied to the member 9 carrying the pivot 4. the head l2 of the spring-loaded rod l carried by the member 9 will be carried into engagement with the contact-carrying lever 3, with the result that compressive stress will be built up in the spring I0 as the member 9 rotates relative to the lever 3. When rotation of the member 9 about the pivot 4 is sufficient to cause the contact segment 13 to move beyond the cooperating contact finger It the electromagnet 8 will become de-energized, whereupon the contact-carrying lever 3 will become freed to move, under the action of the compressive stress in the spring ID, in the direction to carry its contact I into engagement with the cooperating contact 2 with abrupt action. When the controlling force is released from the member 9, as it will be when the main switch contacts are required to open, said member will tend to return to its former position. The initial portion of the return movement of the member 9 about the pivot will cause reclosure of the auxiliary switch l3, it accordingly to energize the electromagnet 8. Since the armature will now be at or adjacent to the other pole I of the electromagnet, it will be held there accordingly to retain'the contact-carrying lever in the position corresponding to the main switch contacts being closed. When the movement of the member 9 about the pivot is sufficient to cause opening of the auxiliary switch, the electromagnet will become de-energized whereupon the contact-carrying lever 3 will move in the direction to carry its contact I away from the cooperating contact 2, such movement being assisted by a throw-off spring l8 associated with the main switch contacts.

In employing a number of switches, each arranged for actuation as hereinbefore described, to efiect the desired sequential establishment of circuits in a traction or other control equipment where the controlling forces for individual switches are applied for example through respective cams operated by a common cam-shaft, many advantages can be achieved. Among these advantages are elimination of indeterminate contact pressures due to partial closing, elimination of dependence of rate of contact operation on rate of cam shaft movement, elimination of the necessity of arresting cam shaft movement at each notch, and the allowance of a greater number of switches operable from a single cam shaft as well as greater precision of switch actuation.

What I claim as new and desire to secure by Letters Patent of the United States is:

,file of this patent:

1. An electric switch actuating arrangement comprising a fixed contact, a movable contact, a principal switch member adapted to carry said movable contact into and out of engagement with said fixed contact, an operating member mounted for movement relative to said principal switch member, resilient energy-storing means including a spring interposed between said operating member and said principal switch member, an electromagnet adapted to act on said principal switch member in opposition to and with a force greater than any force exerted by said spring, an auxiliary switch adapted to open and close responsive to movement of said operating member and independent of movement of said principal switch member, said auxiliary switch being arranged to be open at the end limits of travel of said operating member and closed for a predetermined distance of travel between said end limits, and means for energizing said electromagnet through said auxiliary .switch 'inember, whereby said electromagnet will be energized during initial movement of said operating member to hold said principal switch member in position and will be deenergized during final movement to enable said operating member to act through said resilient means on said principal switch member to move it with a snap action.

2. An electric switch arrangement comprising a pair of cooperating main switch contacts, a contact-carrying member adapted to carry one of said contacts into and out of engagement with the cooperating contact, an electromagnet having pole pieces defining an air gap, an armature located on said contact-carrying member and adapted to operate in said air gap between said pole pieces in such a manner that with said contact-carrying member in the position corresponding to the contacts being fully opened said armature will be located adjacent one of said pole pieces and with the contacts fully closed said armature will be located adjacent the other 0: said pole pieces, an operating member adapted to have a controlling force applied thereto when actuation of said switch is desired, resilient means interposed b tween said operating member and said contactcarrying member and arranged so that the restraint imposed by said electromagnet is greater than the force exerted through said resilient means, and means including an auxiliary switch arranged in series with said electromagnet and adapted to be closed during mid-operation of said operating member, and said auxiliary switch being adapted to deenergize said electrom'agnet at either extreme limit of travel of said operating member, whereby said contact-carrying member may be caused to carry its contact into and out of engagement with the cooperating contact with an abrupt snap action.

WILLIAM TAIN GRAY.

REFERENCES CITED The following references are of record in th 1 UNITED STATES PATENTS 3 Number Name Date 692,217 Sundh Jan. 28, 1902 1,535,240 Morris Apr. 28, 1925

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