US2446961A - Thermostatically operated electrical switching device - Google Patents

Description

Aug. l0, 1948.

Filed Jan. 5. 1946 J. E. SHERLOCK THERIOSTATICALLY oPsnA'rED ELE SWITCHING DEVICE cTR'IcAL 2 shuts-shut 1 r/////....\m a4 :l//l/z J. E. SHERLOCK 2,446,961 THERIOSTATICALLY OIERATED ELECTRICAL SWTTCHING DEVICE 2 Sheets-Sheet 2 Aug. 10, 1948.

Filed Jan 5. 1946 /NVE/W'OR (kwh @um ,LL/4% Patented Aug. 10, 1948 THERMOSTTATICALLY OPERATED ELECTRI- CAL SWITCHING DEVICE John Edward Sherlock, Snnbury-on-Thames, England, assigner to The British Thermostat Company Limited, Sunbnry-on-Thames, Eng- Y land, a British company Application January 5, 1946, Serial No. 639,373 In Great Britain July 3, 1945 This invention relates, to thermostatically operated electrical switching devices and has for its object to provide an'lmproved construction or ararngement of this character more particularly intended for the control of refrigerating apparatus and designed to provide a simple compact and reliable instrument capable of production at a small cost and characterised by ease of accessibility to the working parts for scaling and testing purposes.

According to the invention the improved thermostatically operated electrical switching device includes a movable switch component adapted to be operated against spring opposition by the movement of a flexible metallic bellows, hand control means for varying the resistance to the `bellows movement and for providing an off position, and means for ensuring quick make-andbreak movements of the said switch component.

According to the preferred form of the invention a thermostatically operated electrical switching device includes a xed switch component, a pivotally mounted movable switch component, a flexible metallic bellows connected by a capillary tube to a phial exposed to the temperature to be controlled, means carried by said bellows to rock said movable switch component to switch closing position, a spring connected to said movable switch component and to an element normally stationary, and manually operated means for ad` l base and has a movable upper end plate 1 to which l is secured centrally a rod 8 abutting in a recess 9 formed at one end of a pvoted switch arm i8 whereby the movement of the bellows when expandng `is transmitted to the arm. The switch arm IB is movable about a fixed pivot II and is formed integral with or fixed to two vertical plates I2 (see Fig. 3).

The end ci the switch arm remote from that engaged -by the rod 8 carries a contact plate i3 adapted to be moved into and out of engagement withtwo stationary electrical contact terminals it. The movement imparted to the switch arm I by expansion oi the bellows 5 rocks it in an Aanti-clockwise direction to bring the plate I3 into contact with the terminals I4 to close the switch, this movement being opposed by a main spring I5, the tension of which is adjustable so that the temperature at which the bellows will overcome the resist-ance of the spring can be varied. One end of the spring I is adjustably anchored to the vswitch arm extension plates I2 by means of an justing the position of said element to move said switch member to an off position.

Reference will now be made to the accompanying drawings which illustrate a thermostatically operated electrical switching device constructed according to the invention and wherein:

Fig. 1 is a sectional elevation showing the switch members open, and inoperative,

Fig. 2 is a sectional elevation showing the switch members closed,

Fig. 3 is a cross sectional elevation taken on the line A-B of Fig. 2, and

Fig. 4 is a sectional plan taken on the line C-D of Fig. 2.

In the construction illustrated and referring first to Fig. 1, the improved thermostatically operated electrical switching device is disposed within a casing I having an extension 2 by which it can be attached to a fixed support. Within this casing is a main compartment 3 which contains the switching and adjusting mechanism and a lower compartment 4 containing a flexible metallic bellows 5 Iconnected by a capillary tube 8 to a phial exposed in the area where the temperature is to be controlled. The bellows is fixed at its adjustable screw-threaded rod l'S which passes freely through asocket Il carried at one end of the plates I2, the head I8 of the ,rod abutting against the outer end of the socket. The screwthreaded portion of the .rc-d Iii engages a nut i9 having a helical groove on its surface so that it engages and retains one end of the' spring i5. Rotational movement imparted to the rod i6 will, therefore, alter the position of the nut i9 and increase or decrease the tension of the spring, but this adjustment is provided for initial setting purposes and is normally inaccessible. The opposite end of the spring is formed with a hook 2li which engages around a pin 2I carried by a vertical portion 22 of a two-armed lever 22-3I moy- .able around a pivot 23 but lield stationary during the normal operations of the instrument.

The two-armed lever 22..-3I carries an extension in the form of a plate 24 which is engaged bythe periphery of a cam 25 carried by a rotatable spindle 26 which projects through to the exterior of the casing I and is provided with a knob 21 for manual adjustment. The cam performs `a double function in that during the first part oi its rotational movement its edge 28, shown in Fig. 4, bears against the plate 24 and rocks the lever 22 about its pivot in a clockwise direction until the position is reached Where the required load is imparted to the spring I5. When the spring has been adjusted to load the bellows to the extent required, the lever 22 remains stationary thereafter during the automatic operation of the instrument. During the second part of the cam movement a ramp at 2! (Fig. 4) rocks the lever to an einem: such that members :u ,carried by as second arm 3i engage beneath the switch arm i0 and lift it to the inoperative position shown in F18. 1. In this way a mechanical "oil" position is provided, movement of the switch arm to this positionv interrupting the electrical circuit irrespective of temperature conditions.

The switch contact plate i3 is mounted over a stud 32 projecting downwardly from the switch arm, said stud being formed with a knife edge 33 .bearing on the plate I3 which can therefore tilt slightly relatively to the stud so that with the assistance of a spring 34 disposed between the plate I3 and the under side of the switch arm the plate is rendered self-aligning with respect to the two y stationary contact members I4. A quick make-and-break in the switch operations is obtained by the use of a permanent magnet 35 disposed immediately below the switch arm (see Fig. 4) and any lost motion is counteracted by the aforesaid spring 34 bearing on the contact plate I3 which ensures that any oscillatory movements of the said plate are damped out when the forces due to the bellows 5 and the main spring l5 are in equilibrium. The adjusting knob 2l disposed on the top of the casing l operates in conjunction with graduations or other markings to indicate to the operator the various operative positions andthe "oiT position.

Iclaim: Y

1` A thermostatically operated electrical switching device comprising, in combination, a pivotally mounted switch component, xed switch components, a self-aligning contact element carried by said pivotally mounted switch component and cooperable with the fixed switch components, a. iiexible bellows movable in response to variations in temperature of the apparatus under control, means actuated by said bellows to rock the pivotally mounted switch component on its pivotal axis, a pivotally mounted two-armed lever, a spring connecting one arm of said lever to the pivotally mounted switch component at a point Sil components in self-aligning relation. therewithV under the influence of said spring, and :being operative to damp out oscillatory movements when the forces due to said bellows and spring are in equilibrium.

3v. A thermostatically operated electrical switching device as deiined in claim 1, wherein said pivotally mountedswitch component carries a contact plate engageable with said xed switch components in self-aligning relation therewith under the iniluence -of said spring, and being operative to damp out oscillatory movements when the forces due to said bellows and spring are in equilibrium, and including a permanent magnet disposed immediately beneath said pivotally mounted switch component and operative to eiect a quick makeand-break operation thereof.

JOHN EDWARD SHERLOCK.

REFERENCES CITED The following references are of record in the lle of this patent:

UNITED STATES PATENTS Number Name Date 40l 2,044,736 ,Remy June 16, 1936 2,239,146 Dillman et al. Apr. 22, 1941 2,304,019 Raney Dec. 1, 1942

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