US2753419A - Mechanical thermo-responsive actuating means - Google Patents

Description

y 3, 1956 A. E. SCHWANEKE ET AL 2,753,419

MECHANICAL THERMORESPONSIVE ACTUATING MEANS Filed Dec. 14 1953 zzvmvroas: 56/5 wazzeke red C :5 fiwazzejfe Qflrea a United States Patent MECHANICAL THERMO-RESPONSIVE ACTUATING MEANS Alfred E. Schwaneke, Northbrook, and Fred C. Schwaneke, Chicago, Ill., assignors to A-M Corporation, Chicago, Ill., a corporation of Illinois Application December 14, 1953, Serial No. 397,850 8 Claims. (Cl. 200-137) This invention relates to mechanical devices operated by the expansion and contraction of a rigid body under the influence of temperature changes, and particularly to improvements in such devices wherein the physical expansion and contraction of a solid in response to temperature changes is utilized to operate some other means such as the switching element of an electric thermostat.

The main objects of this invention are to provide an improved means for utilizing the physical expansion and contraction of a rigid body under changing temperature conditions to actuate an operating arm; to provide such a means for utilizing the lineal expansion and contraction of an elongated rigid body to actuate a lever arm integrally supported by the body; to provide such a device in which dimensional changes of the body are greatly multiplied during translation to effectuate the function of the operating arm; to provide an improved actuating device in which relatively small dimensional changes in a rigid body caused by temperature variations are translated into mechanical movement of practical operational use; to provide such a device that is operationally more sensitive and accurate; and to provide such a device that is of simple unitary construction, easily fabricated, and of low manufacturing cost.

A specific embodiment of this invention is shown in the accompanying drawings, in which:

Fig. 1 is an elevational side view showing the principal elements of a temperature responsive actuating means embodying the invention.

Fig. 2 is a perspective view of the same.

Fig. 3 is a view similar to Fig. 1 showing an arrangement in which the operating arm functions directly as a contact carrying switch member.

Fig. 4 is a plan view of a thermostat frame adapted to embody a device such as that shown in Figs. 1 and 3.

Fig. 5 is a sectional view as taken on line 5--5 of Fig. 4 showing a thermostat arrangement for using the device shown in Fig. 1.

Fig. 6 is a side elevation showing a thermostat arranged to use the form of actuating device shown in Fig. 3; and

Fig. 7 is a sectional view of the same as taken on line 7-7 of Fig. 6.

In the form shown in the drawings the improved actuating means comprises three principal elements, namely: a base member, or driving element 1, made of a soft material having a. high coefiicient of expansion; a motion translating member, or driven element 2, made of a material having a relatively low coefficient of expansion; and an operating member or arm 3, which is actuated by the driven element 2.

The base member, or driving element 1, is preferably a solid elongated bar having a flat bottom surface and adapted to be influenced by heat, through direct conduction, uniformly throughout its length. Any suitable material may be used for the member 1 which will withstand the temperature to which it is to be subjected and which has a relatively high rate of expansion and contraction under changing temperature conditions. For example,

2,753,419 Patented July 3, 1956 brass or cobalt chromium steel may be used for this purpose.

The driven element or motion translating member 2 is preferably made of a material having a low rate of expansion and contraction in response to temperature change, such as stainless steel or Invar, and is formed as an angle member, such as a forwardly oblique L, having a long leg and a short leg, preferably with an acute included angle between them so that when the ends of the legs rest on a common plane the short leg will stand substantially normal to the common plane.

In the form shown the remote ends of the legs of the driven element 2 are set upon and integrally secured to the upper surface of the base member 1 by means of laterally projecting feet 4 and 5, which are formed to lie flatly against the surface of the base member and which are preferably welded thereto. Thus, upon any lineal expansion or contraction of the base member 1, the long leg of the driven member 2, which is inclined upwardly from the base member, will act as a rigid strut and the short leg 6, which stands substantially normal to the base member, will be moved angularly about the axis of the angle corner 7 between legs of the driven member. The axis of the angle corner 7 lies parallel with the plane of the base member 1 and at right angle to the direction of lineal expansion and contraction thereof so that the corner 7 functions as a stiff hinge between the legs and the short leg 6 is thereby principally affected, by any variation of the length of the base member between the points where the feet 4 and 5 are secured, to change its angular disposition relative to the plane of the base member.

The operating member or arm 3 is directly and rigidly secured by one end to the outer face of the short leg 6 of the driven element 2 by any suitable means and is moved angularly with the short leg 6 about the axis of the corner 7 upon any variation of the length of the base member 1. The arm 3 is an elongated member, as shown, and the major portion of its length extends outwardly across the corner 7 a considerably greater distance than the length of the short leg 6. Thus any lineal movement of the end of the short leg 6 at the plane of the base member 1 is directly translated to the free end S of the operating arm 3, in a swinging movement thereof about the corner 7, and is multiplied in direct proportion to the relative lengths of the leg 6 and the arm 3. In this way the relatively small changes in the length of the base member caused by variations in temperature are increased or multiplied to an extent sufficient for practical use, particularly where operative response to small temperature changes, or sensitivity, is desired.

As shown in Figs. 1 and 3 the operating arm 3 is a substantially right angle member having a short leg 9, secured directly to the short leg 6 in parallel relation therewith, and a long leg disposed substantially parallel with the base member 1. In this manner the space occupied by the actuating means or device is kept to a minimum without sacrifice of the movement multiplying function of the operating arm. It will be understood, however, that the disposition of the tree portion of the operating arm may be as desired and in accordance with the manher in which the device is to be used.

In the arrangement of Fig. l, the arm 3 is intended to operate the moving blade of an electric switch, as in Fig. 5, and is provided with an operating button 10 of a suitable dielectric material, such as porcelain. In the arrangement of Fig. 3 the short leg 9 of the operating arm 3 is suitably insulated from the driven member 2, by means of an insulation plate 11 disposed between the legs 6 and 9 and by suitably insulating the mounting rivet. In this arrangement the arm 3 is intended to function as the moving blade of an electric switch and carries a contact element 12 adjacent its free end 8.

means is illustrated in Figs. 4 to 7 inclusive, and in the form shown comprises. a one-piece frame havinga topplate 14 from which support legs 15 and 16 dependon each side for suitable attachment to the base member 1 of the actuating. means. As shown, the rearward legs 15 are staked t the side margins of the base member 1 and hence rigidly fastened thereto; The legs 16, however, which are located intermediatethe frame ends, are engaged in marginal. notches 17 in the base member in such a manner as to permit relative movement in the longitudinal directionof the base-member and yet secure the frame against lateral or vertical movement relative to the base member. This is accomplished by underbeveling' the inner edge of each notch 17 and then staking the bottom end of each leg 16' inwardly, as shown in Fig. 7, and by making the notches 1-7 of greater length than the legs 16.

As shown in-Figs. 4 and the thermostat is constructed toutilize-the actuatingmeans of Fig; l and in this arrangement the top plate 14 of the frame carries a pair of cantilevered switch blades 18 and E9; positioned so that the lower blade19 may be operated by the operating arm 3; The switch blades 18' and 19 are secured to the top plate 14 in the usual manner by means of suitable terminal rivets 20 adapted for connection with conductor leads; not shown, and the blades have contacts 21 and 12;.

respectively, adjacent their free ends for mutual coaction to open and close an electric circuit between the blades.

In use this thermostat is mounted with the bottom surface of the base member l in direct heat conducting engagement with the heated element to be controlled, the frame being attached to suitable support members, not shown, by'means of the Wings 23 whichproject' from each side of the frame top plate 14.

Figs. 6 and 7 show a thermostat embodying. the actuating device of Fig. 3. In this arrangement only the stationary switch blade 24 is carried by the thermostat frame member 14, the operating arm 3 serving as the movable switch blade and the contact 12 thereof engaging the contact 25 on the blade 24.

In the case of the thermostat of Fig. 5 the switch blade 19 is tensioned to bear away from the blade 18, toward the operating arm. 3, and any lineal expanding or contracting movement of the base member 1, in response to a temperature change, causes a proportionate angular movement of the arm 3, to open or close the contacts 21' and I2, and hence controls the operation of. the electric heating means affecting the base member 1. The arm 3, being a relatively stiff member, is directly responsive to any angular movement of the short leg 6 about the axis of the angle corner 7 and because the base member 1 is of high expansion rate material, whereas the driven member 2 is of a material having a low expansion rate, only a relatively small change in the length of the base member is required to produce an appreciable movement in the free end of the arm 3. Thus a relatively small temperature change will cause opening and closing of the contacts 21-12 and the thermostat is comparatively quite sensitive.

In the case of either thermostat it will be seen that upon lineal expansion of the base member 1 of the actuating means, the short leg 6 of the driven member 2 will be moved arcuately about the corner 7, in the counterclockwise direction as seen in Figs. 5 and 6, soas to cause the free end' of the arm- 3 to lower and thereby open the contacts. This open position is shown by the relation of theparts in Fig. 5". Upon cooling of the heated element,

however, the base member 1., contracts and moves the leg.

6, of. the driven element, in the. opposite direction so as tolift the arm 3 and'cause closing of, the contacts whereby the heating means again becomes-energized. This closed.

positionis shown in,Fig. 6.

Adjustment of the thermostat for various ranges of operation is accomplished by varying theposition of the stationary contact arm toward or away from the moving contact and any of several well known means may be employed for that purpose. The adjustment means 26 shown is a common arrangement and therefore need not be described.

The main advantages of this invention reside in the form and arrangement of the driven. element of the actuating means and the operating arm carried thereby whereby small amounts of expansion and contraction of the base member are greatly multiplied during: translation into useful work; and in the extremely simple construction of, the device which is nevertheless considerably more sensitive than arrangements heretofore employed.

Other advantages are to be found in the compact arrangement of the operating elements of the device whereby a minimum of space is required for its installation; and in the fact that the device is readily adaptable for substantially any use where indication or control of heattransmitted by direct conduction is desired.

Although two specific embodiments of this invention are herein shown and described it will be understood that details of the constructions shown may be altered or omitted without departing from the spirit of this invention as defined by the following claims.

We claim:

1. A device of the class described comprising a driving member of high expansion material, a unitary driven memberof low expansion material having two legs joining to form an angle, the remote ends of said legs being secured fast to said driving member in spaced relation, and an operating arm secured to and extendingalong one of said legsacross and beyond the corner formed by'the junction of said legs with each other.

2. A device of the class described comprising a driving member of high expansion material, a unitary driven member of low expansion material made in the form of an angle having a long leg and a short leg the remote ends of which. are secured fast to said driving member, and an operating arm mounted rigidly on the short leg of said driven member and extending therefrom across the corner formed by the angle junction of said long and short legs.

3. A device of the class described comprising a driving member of high expansion material, a unitary driven member of low expansion material made. in the form of an acute angle having a long leg and a short leg the member and extending therefrom across the corner formed by theangle junction of said long and short legs.

4. A device of the class described comprising a. driving member of high expansion material, a unitary driven member of low' expansion material having two legs joining to form anangle, the remote ends of' said legs being secured fast to said driving member in spaced relation, one of said legs being shorter than the other and disposed substantially normal to a plane common to the remote ends of both said legs, and an operating arm mounted on said one leg'and extending therefrom across and beyond the junction-of said legs with each other.

5. A deviceof the class described comprising an elon gated driving member of high expansion material, a unitary driven member of low expansion material extending lengthwise of said driving member and having a long leg and a short leg joining to form an acute angle, the remote ends of said legs being secured fast to said driving member in longitudinally spaced relation, and an operating armvmonnted on said short leg and extending therefrom across the junction of said legs with each other.

6'. A thermal-responsive actuator comprising an elongagted drivingmember made of high expansion material, an, elongated driven memberv made of low expansion ma? terial and bent intermediate its ends to form an acute angle having a long leg and a short leg, said driven member being disposed lengthwise of said driving member and the remote ends of said legs being secured to said driven member in longitudinally spaced relation, an operating arm mounted on said short leg and extending therefrom beyond the angle formed by the junction of said legs with each other, said operating arm lying in a plane common to both said legs.

7. A thermal-responsive actuator comprising an elongated driving member made of high expansion material, an elongated driven member made of low expansion material and bent intermediate its ends to form an acute angle having a long leg and a short leg, said driven member being disposed lengthwise of said driving member and the remote ends of said legs being secured to said driven member in longitudinally spaced relation, an elongated operating arm mounted by one end portion on said short leg and extending therefrom beyond the angle formed by the junction of said legs with each other, said operating arm lying in a plane common to both said legs and having the portion extending beyond said angle disposed substantially parallel with said driving member.

8. A thermo-responsive actuator comprising an elongated driving member made of high expansion material, an elongated driven member made of low expansion material and bent intermediate its ends to form an acute angle having a long leg and a short leg, said driven memher being disposed lengthwise of said driving member and the remote ends of said legs being secured to said driven member in longitudinally spaced relation, an operating arm mounted on said short leg and extending therefrom beyond the angle formed by the junction of said legs with each other, said operating arm lying in a plane common to both said legs, and adapted to move pivotally about said bent portion of said driven member away from said driven member and said driving member upon contraction of said driving member.

References Cited in the file of this patent UNITED STATES PATENTS 1,942,002 Romanelli Ian. 2, 1934 2,248,666 Fischer July 8, 1941 2,441,725 Smith May 18, 1948 2,627,565 Smith Feb. 3, 1953 2,664,483 Broekhuysen Dec. 29, 1953

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