US1728242A - Electrical switch - Google Patents

Description

Sept. 17, 1929. 9A. G. LoBLEY ELECTRICAL SWITCH Filed Sept. 22, 1926 2 Sheets-Sheet gum-ron l lH M "1.

SGP- 17', 1929- A. G. I oBLEY 1,728,242

' ELECTRICAL swITcH I Filed Sept. 22. 1926 2 Shets-Sheet 2 Patented Sept. 17, v192,9

UNITED STATES PATENT OFFICE .ALFRED GLYNNE LOBLEY, F CHAPEIn-EN-LE-FBITH, ENGLAND, ASSIGNOB T0 BIR- MIN'GHAI ELECTRIC F'UBNACES LIMITED, OII BIRMINGHAM, ENGLAND, A COB- POBATION 0F GREAT BRITAIN ELECTRICAL SWITCH Application led September 22, 1988, Serial No.

rlhis invention has reference to electrical switches of the quick-make and quick-brake type wherein a spring element isinterposed between a lever or similar operating member e and a triplaction member that carries or is connected with the movable contact member, and wherein the displacement of the said op- .erating member through a predetermined distance (eitherin the break or the"make direction) so shifts the spring element in relation to the ivot centre of the trip member as to render t e said spring effective for opening or closingthe switch with a snap action.

When such switches are used for certain purposes (as, for example, when the operating lever is actuated mechanically or by a thermostat device) the said lever may be subjected to intermittent or other impulses tendf lng to oscillate or displace the snap-action spring without actually carrying the latter over the 'dead centre of the system, and when such oscillations are set up as the lever is approaching the tripping int, they may, un-

ess their eiect be neutra ized, result in slight separations of the switch contacts sufficient to permit of arcing between the latter and irregularity or intermittence in the circuit controlled by the switch.

In order to eliminate the possibility o f arcing' and intermittence occurring under the conditions referred to, and with the further object of providing an efficient quick makeand-break switch which is specially adapted for thermostatic or mechanical actuation, it

is proposed, according to the present invention, to 'arrange in connection with the springactuated trip member, means for posltively retainin or locking the said member definitely in eit er its on orits off position, and

40 to utilize the operating lever (or means connected therewith) for releasing the trip member only when the snap-action spring has been carried beyond the dead-centre oint or made eiective for imparting the full reak or make movement to the trip member.

A form of switch constructed according to the said invention, and embodyingl provision for neutralizing or damping-out t e effect of lever and spring oscillations when the said lever is in proximity to the dead centre 4of the nasceva in Great Britain october 1, 1925.

system, is shown in the accompanying drawin lin which v igure 1 is a general elevation of the switch mechanism which is adapted to be operated, in the break direction, by a thermostat (part of which is also shown in the figure) and in the other or make direction by a spring. This view shows the parts in the positions they assume when the switch-contacts or-terminals are closed but with the operating lever just on the pointof bein tripped in the circuitbreaking direction y the thermostat control.

, Figure 2 shows certain parts of the switch in plan or edge view, on a larger scale than Figure 1. r

Figure 3 is a view of the switch similar to Figure ,1 showing'the parts in the oil or circuit-breaking positions, and

Figure 4 shows the switch closed and with the member that controls the contacts definitely locked in the on position.

The same letters of reference indicate corresponding parts in the several figures ofthe drawings.

In this switch, the trip member (i. e., the member which actually controls the separation and closing of the contacts a, a1) consists lof a pair of elongated plates or crank arms b, b1 furnished with bearings b* or suitablybracketed pivots and separated sufficiently to permit of an extremity of an o rating lever c being exten ded into the s ace Btween them. The trip-spring element (which may be a simple tension spring or a pull-action com pression spring) is connected at one end to the extremity c1 of the lever and at the other end to a cross-pin b or other anchorage disposed between the plates of the trip member and forms an extensible link connection between the trip and lever, whilst the pivots b* of the said trip-member are disposed intermediate the respective connectlons of the spring with the lever and tri member, or in such a manner as will enable t elever, during its angular displacement in either direction, to first increase the tension of said spring and then bring about the snap action of the trip member by carrying the spring past or over the centre of the tmp-member ivots.

A suitable stop or catch is em ed in the switch for limiting thevmovement of the trip member in both the make and break directions, Whilst the trip member is connected, directly or indirectly in any convenient manner, with the movable contact member of the switch. As an example of contact arrangement which may be used with advantage in a thermostat-operated switch for controlling a relay circuit,'two contacts a, a1 of stud-like form are used and one of these is carried on a fixed terminal support a2 Whilst the other is carried by a spring blade a3 whose shank is fixed to another terminal support a4, this spring being extended into engagement or connection with a piece of ebonite or other non-conductor a5 fixed to. and extending from one side of the trip member. The tendency of the blade spring is to maintain the studs in close contact both when the trip member ig in the on position and at or during commencement of the break action, but on the trip-member. being shifted to the off position, the contact stud on the spring contact arm is moved away from'the fixed contact to a distance suilicient to prevent arcing between. g

the contact studs when the switch is open.

To provide for the definite locking of the trip-member and its associated contact member in both the on'and otl' positions, two pawl-like devices e, el, are used and disposed on opposite sides of, and in the plane of movement of, the operating lever. These pawls may consist, as shown0f spring blades or tongues stifl'ened intermediate their two end portions by riveting light but rigid metal plates e2 thereto, and one end of each pawl is anchoredto a post e3 or similar attachment on the switch base, whilst the other ends e, e5 are adapted respectively to engage suitably-disposed notches or shoulders e, e7, formed on the opposite edges of one of the'trip-member plates. vThese pawls and notches are so disposed that 'when the trip-member is in the on position (Figure 4) it is locked by the end e* of the pawl e so engaging the notch e as to resist any force tending to shift the said trip-member towards the oi position, whereas in the open position of the said member, it is similarly engaged and locked by the end c*i of the other pawl e1 engaging the notch e (see Figure 3), whilst for liberating the trip member 4when (but not until the snap-action spring d has been shifted over the centre of the trip-member pivot and made definitely operative for opening or closing the switch) the operating lever is provided with'a pairv of adj ustable` screws or abutments d, 'd1 respectively projecting from its opposite edges towards the pawls e, el.; the arrangement being such that as .the lever swings over .the dead-centre point and brings the spring d into eiective action, one of the abutments will impinge upon and disengage the p awl that is locliing the trip-member and liberate the latter to permit of the opening or closing (as the case may be) of the switch.

The operating lever and a switch such as above described may be actuated positively (by mechanical, thermostatic or other means) in both the make and break directions, or

have positive actuationin one direction only, the movement inthe other direction being derived from a, suitably-applied spring. in the arrangement illustrated, however, where the switch is part of an installation for automatically controlling or regulating the supply of current to electric furnaces, the opening of the switch is effected positively by the impingement of a thermostat-operated contact g on the short heel c1 of the switch lever, whilst the closing movement is derived from a spring h' which (on suiiicient retraction of the thermostat contact) throws the leverin the appropriate direction for rendering the trip-spring operative and disengaging the'retaining pawl so that the tripmember may be actuated for closing the switch contacts.

.A stop device is incorporated in the switch for limiting or determining the movement of the trip-member in both directions, and in the illustrated construction, the stop isconstituted by'two horns or projections z', il, co- Eperating with a plate i2 fixed to the'switchase. plate arrests the trip respectively in the io and on positions. f

Having describ d my invention, what I .claim and desire to secure by Letters Patent 1s Figures 3 and 4 show how the stoip-,

1. A snap switch having a. pivoted trip 4 swings being located between the lever pivot y and the point of connection between the spring and trip, the arrangement being such that the path of movement of the both ends of the spring and the portions ofthe lever and trip to which the spring is connected from one position to the other is across the pivotl of the trip member, a switch member connected to the trip, latches for locking the trip in its extreme positions, and means for disenga'ging the latches.

2. A snap switch having a pivoted trip member, a ivoted actuating lever, a tension spring' fixe y connected to the lever and trip and at points remote from their pivotal connec'tions, said spring extending in the general direction of the lever, the pivot for the trip being located between the point at which the in a air of crank arms acrank lin connecting the. arms to cach ot er, pivotal supports for the crank arms,a switch member connected to the trip, latches for holding the trip'in its extreme'positions, a pivoted lever extending between the cranks of the trip, and a spring fixedly connected to the lever and the crank pin` located betweenvthe cranks, said spring forming an extensible link connectionl between the trip and the lever.

4. A snap switch comprisinga trip having a pair of crank arms, a crank pin connectingl the arms to each other, pivotal supports for the 4crank arms, a switch member connected to the trip, latches for holdingy the 'trip in its extreme positions, limit stops on the trip, a pivoted lever extending between the cranks of the trip, and a spring xedly connected to the lever and the crank pin located-between the cranks, said springl forming an extensible linky connection between the trip; and the lever.

5. A snap switch having vapivotefl-trip, limit stops on the trip, means for actuating y the trip from one extreme position to its other extreme position, a fixed contact, a leaspring xed against movement at one end and connected to the trip at its other end, and va movable contact carried b Vthe leaf spring between its ends, and a apted to engage the fixed contact vwhen the trip is in one of its extreme posltions.

In testimony whereof I have herennto setmy hand. ALFRED GLYNNE LOBLEY.

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