US2784274A - Electrical contactors - Google Patents

Description

March 5, 1957 A. c. GASCOINE ETAL 2,784,274

ELECTRICAL CONTACTORS 2 Sheets-Sheet 1 Filed May 22, 1953 l vzvevzfors a 0 w y mm a c A 5 r v FQ A P March 5, 1957 A. c. GASCOINE ETAL 2,784,274

ELECTRICAL CONTACTORS 2 Sheets-Sheet 2 Filed May 22, 1955' United States Patent O 2,784,274 ELECTRICAL CONTACTORS Arthur Cecil Gascoine and Royston Arthur Frederick Craven, Watford, England, assignors to Watford lElec tric & Manufacturing Company Limited, a British conn pauy, and Arthur Cecil Gascoine, Watford, England Application May 22, 1953, Serial No. 356,648 4 Claims. (Cl. 200-87) This invention relates to electrical contactors of the kind which comprise a pivoted arm assemblage (hereinafter referred to as the contact-arm-assemblage) which carries one or more switch contacts and an armature, and wherein there is provided an electro-magnet to act upon the armature to rotate the contact-arm-assemblage from a position in which said switch-contacts are disengaged from co-operating fixed contacts, to a position in which they are engaged therewith.

Usually, in electrical contactors of the kind referred to, the contact-arm-assemblage is biased, as for example by a spring or springs, in a direction such that the contacts are in the disengaged position when the magnet is inoperative. On the magnet becoming energised the armature embodied in the assemblage is attracted towards the pole-piece of the magnet, thereby partially rotating the assemblage to bring the contacts into engagement.

in practice it is found that, when contactors of this nature are required to operate under conditions where they are subjected to violent shock or vibration, the con tact-arm-assemblage frequently becomes dislodged from the position where the contacts are engaged (i. e., where the armature is held against the pole-piece of the magnet), notwithstanding that under normal stable conditions the magnetic force holding the assemblage in this position is ample. This is found particularly to be the case when using a contactor in an alternating current circuit as in this instance, of course, the strength of the magnetic force fluctuates with the changes in value of the current in the coil of the magnet. It is also sometimes found that accidental temporary closing of the contacts from the open position results from such shock, or vibration. Such conditions of operation arise, for example, when contactors are used in naval vessels.

The object of this invention is to provide a contactor of a construction such that the risks of the contactorarm-assemblage becoming dislodged in the manner described above are greatly reduced.

According to this invention there is provided an electrical contactor of the kind described wherein the axis of rotation of the contact-arm-assemblage lies intermediate of the armature and the switch-contacts carried by the assemblage, and wherein the parts of the assemblage are so proportioned and positioned that the assemblage as a whole possesses approximate static balance and approximately balanced moments of inertia both about the said axis of rotation and about axes perpendicular to the said axis of rotation, about which axes the assemblage would otherwise tend to rotate when subjected to sudden shock.

These conditions of the design of the assemblage are closely analagous to the conditions for providing dynamic balance of a rotating body, wherein rotation or acceleration does not introduce any force or couple tending to set up vibrations in the system. In the present case the requirement is that shock or vibration should not set up rotation of the assemblage which would cause rotation and unwanted opening or closing of the switch contacts.

Preferably, the contact-arm-assemblage is substantially a fiat structure the general plane of which contains the axis of rotation. By fiat is meant that the lateral and longitudinal dimensions of the structure in the said plane are considerably greater than the thickness of the structure normal to the said plane.

According to a feature of the invention the flat contact-arm-assemblage is mounted on a panel to be rotatable about its axis through a small angle from approximate parallelism with the panel, the fixed contact or cont acts being mounted to one side of the said assemblage and the operating magnet on the opposite side of the assemblage.

According to another feature of the invention the contacts aforesaid are mounted between the panel and the assemblage, and the magnet is mounted on the remote side of the assemblage from the panel.

One embodiment of the present invention will now be described, merely by way of example, with reference to the accompanying drawings whereof:

Figure 1 is a front elevation of an electrical contactor in accordance with the present invention, and

Figure 2 is a side elevation in the direction of arrow 2 shown at left in Fig. 1 wth certain parts cut away to show details of construction.

Referring to the drawings, a panel 10 carries two spaced-apart support-brackets 11, for a contact-arm-assemblage generally indicated at 12. The assemblage i2 is pivoted at 13 (see Figure 1) between the brackets 11 for partial rotation about a horizontal axis parallel with the panel 10.

The assemblage 12 comprises a main transverse contact-carrier 15 from which extend three laterally spaced pairs of lugs 16 carrying contacts 14 mounted on rockers 17. Two laterally spaced arms 18 extend downwardly from the carrier 15, and the arms are bridged at their free ends 19 by a channel-sectioned armature support 20. An armature 21 is partially embraced by the support 20, and is connected thereto at the middle of its length by a single pivot generally indicated at 22 (see Figure 2) and consisting of a vertical pivot pin 23 on a rubber bush 24. The pin 23 has a tight fit in the bush 24 which has a tight fit within the armature 21. With this arrangement thearmature is resiliently supported for limited pivotal movements to adjust itself to the pole-piece of an electromagnet which will hereinafter be described. It will be observed that the contacts 14 are mounted on that side of the asesmblage 12 near the panel 10, while the armature 21 is mounted on the remote side of the assemblage from the panel.

When the assemblage 12 lies generally in a position parallel with the .panel 10 the contacts 14 engage cooperating fixed contacts 27 mounted on thte panel It}. This position is taken up when the armature 21 engages the pole piece 28 of an electro-magnet generally indicated at 29, and represents the maximum displacement of the armature 21 from the panel 10.

The magnet 29 is resiliently carried on a pair of supports 39 (Figure l), which extend from the panel 10, by means of resilient bushes 32 mounted on bolts 33 (see Figure 2). The supports 30 are channel sectioned, and embrace the sides 35 of the core 40 (see Figure l) of the magnet 29, the bolts passing through elongated holes 36 in the flanges 37 of the channel sectioned supports 39 and through the bushes 32. The bushes 32 may be made from any suitable resilient material. In the embodiment now being described they are made of neoprene.

When the magnet 29 is de-energised the assemblage 12 partially rotates under the action of springs 42 (see Figure 1) so that the armature 21 leaves the pole-piece 28 and moves towards the panel 10, and the contacts 14 and 27 disengage. Rotation of the assemblage 12 under the action of the springs 42 is arrested by arms 43 (Figure 1) carried by the carrier 15 which engage stops 44 carried by the panel 10.

The assemblage i2 is formed as a substantially fiat structure, by which is meant that the lateral and longitudinal dimensions of the structure measured horizontally and verticallyrespectively in the plane of Figure 1 are considerably greater than the thickness of the struc ture, measured normally to the plane of the paper.

ine individual parts of the assemblage 12 are so proportioned and positioned that the assemblage as a whole is statically balanced and. possesses, balanced moments of inertia about its axis of rotation, and about the vertical and horizontal axes of the assemblage at the point on that axis midway between the two pivotal supports 13 (Figure 1) of the assemblage. In this manner 9 the assemblage is found, as proved by oscillograph rec ords, to suffer far less from the effects. of shock or vibration originating from various directions, than otherwise is the case.

The resilient mounting of thte core 40, and. therefore i) of the pole-piece 28 still further reduces the possibility of the contactor opening under the action. of shock or vibration.

Owing to the fluctuating nature of the magnetic flux when the magnet is energised by an alternating current and the fact that the armature is. biased away from the pole-piece of the magnet by the springs 42, the opening of the contactor, when the flux. is momentarily zero, is more critical than the closing of the contactor; and a smaller out or balance force due to shock or vibration on the armature will open the contactor than will close it. Since, however, the pole-piece 28 is capable of lirnited movement under the action: of shock or vibration, any out of balance force tending to move the armature towards the panel 10 (i. e., out of contact with the polepiece) is accompanied by the tendency of the pole-piece also to move toward the panel. under the action of the shock. The arrangement of contactor described wherein the axis of rotation lies intermediate of the contacts and armature facilitates the balancing of the contact-armassemblage in contrast with customary arrangements of contactor.

We claim:

1. An electrical contactor, device comprising a panel, contacts fixedly mounted thereon, spaced apart brackets .iounted on the panel below the fixed contacts, a contact-arm-assemblage pivotally mounted on said brackets to rotate on a horizontal axis parallel to said panel, said assemblage including a carriencontacts mounted on said carrier and projecting upwardly from the pivotal axis for engagement with the fixed contacts, arms attached to the carrier and projecting downwardly below the said axis and offset inward. toward said panel and having free ends further offset and generally parallel to said panel, an armature carried by the free ends of the arms for pivotal movement about said axis, brackets attached to the panel below the pivotal axis of the contact-armassemblage, an electromagnet supported by said last mentioned brackets close to but forwardly of the armature, whereby when said electromagnet is energized it attracts the armature carried by the arms, causing the contactarm-assemblage to pivot on said horizontal axis and move the switch contacts to engage the fixed contacts; said carrier and switch contacts being located, on the remote side of a plane passing through the horizontal axis parallel to said panel, and the said armature and the said free end so the said arms being located on the opposite side of said plane adjacent the panel, and so disposed relatively to the horizontal axis that static balance and approximately balanced moments of inertia of said assemblage is obtained.

2. The device as set forth in claim 1, including spring means mounted on the first-mentioned brackets in engagement with said assemblage to bias the armature away from the electromagnet, and stop means on the carrier and panel respectively for arresting the rotation of the asesinblage when the electromagnet is cleanergized.

3. The device as set forth in claim 1,. wherein the assemblage constitutes a flat structure, namely, the lat eral and longitudinal dimensions thereofi' measured horizontally and: vertically in a plane parallel to the panel re-considerably greater than the thickness thereof measured in a plane normal to the panel.

4. A device as set forth in claim 1, wherein the electromagnet support brackets are mounted near the opposite edges of the panel facingeachother, with the free ends of the arms and the armature carried thereby swinging freely between said brackets toward and away from the electromagnet.

References Cited in, the file of this patent UNITED STATES PATENTS 532,394 Rawson Jan. 8, 1895 695,568 Lavens et al. Mar. 18, 1902 1,001,409 Jennings Aug. 22, 1911 1,160,896 Hoeltke Nov. 16, 1915 1,763,116 White June 10, 1930 1,832,477 Callingham Nov. 17, 1931 1,936,098 Pengillyetal. Nov. 21, 1933 2,087,895 Bierenfeld July- 27, 1937 2,239,031 Bierenfeld et al. Apr. 22, 1 941 2,424,308 Ellis et al. July 22, 1947 2,425,648 Schaelchlin et a1, Aug. 12, 1947 2,513,695 Van Valkenburg July 4, 1950 FOREIGN PATENTS 301,743 Great Britain Feb. 20, 1930 721,747 Great Britain Jan. 12, 1955

Images