US3391370A - Snap action thermostat with amplified actuating movement - Google Patents

Description

July 2, 196s F, REINGRUBER 3,391,370

SNAP ACTION THERMOSTAT WITH AMPLIFIED ACTUATING MOVEMENT Filed Aug. 4, 1965 [UIMM 'a um.. '.111

[NVE/VTR. FPA N K RE/NGPUBER Arrowf Y United States Patent O 3,391,370 SNAP ACTION THERMOSTAT WITH AMPLIFIED ACTUATING MOVEMENT I Frank Reingruber, Bartlett, N.H. 03812 Filed Aug. 4, 1965, Ser. No. 477,118 1 Claim. (Cl. 337-343) ABSTRACT OF THE DISCLOSURE A bimetal secured intermediate its ends on a heat transfer plate, with both ends free for thermostatic action and an inverted V-strut engaged at its opposite ends with the free ends of the bimetal imparts snap switch opening and closing movements to a spring toggle biased form of switch blade.

The invention herein disclosed relates to thermostats for general control purposes.

Special objects of the invention have been to provide a simple practical snap action thermostat, with amplified movement actuating means, rendering it particularly sensitive and responsive to small as well as greater temperature changes.

This has been accomplished by means of a spring switch blad-e biased in one direction by a spring strut operating as a toggle link to snap the switch blade in opposite directions and by providing a bimetal anchored at the center so as to ilex both ends and by engaging the ends of a V-shaped strut with the opposite ends of the bimetal and the center of the strut in position to stress the switch blade over the dead center of the toggle structure.

Other novel features of the invention and desirable objects accomplished are set forth and will appear in the course of the following specification.

The drawing accompanying and forming part of the specification illustrates a present commercial embodiment of the invention. Structure, however, may be modified and changed as regards the present illustration; all within the true intent and scope of the invention as hereinafter defined and claimed.

FIG. 1 in the drawing is a broken, part vertical sectional view of the thermostat in the normal, circuit closed position.

FIG. 2 is a broken detail view illustrating the reverse, open circuit position of the parts.

FIG. 3 is a bottom plan view with cover removed to show the toggle action switch.

FIG. 4 is a top plan view of the switch mechanism on substantially the plane of line 4-4, FIG. 1.

FIG. 5 is a plan view of the heat transfer bottom cover and the bimetal mounted thereon.

FIG. 6 is a broken sectional detail of the control knob with yielding terminal point.

FIG. 7 is a broken sectional detail of one of the wire terminal binding posts.

FIG. 8 is a diagram illustrating action of the centersecured bimetal.

The bimetal is shown in the form of a ilat strip 10, anchored at the center by means of a rivet 11, on a cover plate 12, forming a heat transfer member and enclosing the bottom of a rectangular case 13, having extended lugs 14 at the bottom by which the unit may be secured in operative position.

The opposite ends of the bimetal are turned up to form abut- ment lugs 15, 16, for the angularly related legs 17, 18 of a V-shaped strut arched at the center and carrying a correspondingly shaped insulating button 19, having a transverse pressure transmitting ridge 20 in engagement with the Switch blade to be controlled.

3,391,370 Patented July 2, 1968 rice The ends of the angular sided expansible and contractible strut are shown as anchored to the ends of the bimetal strip by having extended lugs 21 projecting through corresponding openings in the bimetal.

The angularly spread legs of the V-strut are shown as stiffened by embossed ribs 22 so as to serve as straight rigid pressure transmitting elements.

The switch blade consists in the present illustration of a spring strip 23 secured at one end at 24 and carrying a contact 2S at the opposite end engageable with a companion stationary switch element 26.

Movement of the contact carrying end of the switch blade is limited in the opposite direction by a spaced insulator 27.

Snap spring toggle action of the switch blade is accomplished by means of a spring strut or toggle for-ming link 28 connected at one end with the free end of the switch blade and fixed at the opposite end at 29 to a stationary lug or post 30.

This spring strut is shown as an integral piece struck out of the body of the spring switch blade and left connected thereto at the contact end at 31 and free at the opposite end for engagement with the stationary abutment 30.

The spring strut 28 is bent or bowed as shown in FIGS. l and 2, to enable necessary yield in passage of the switch blade over dead center.

The pressure transmitting button 19 of the strut engages a transversely continuous portion 32 of the switch blade, FIGS. 1 Aand 3, at a point inward from the anchorage point 29 of the spring strut and the opening 33 by which this strut is cut out of the blade is extended back of the stationary lug 30 so that the pressure center 32 on the blade Imay travel from the position at one side of center 29, FIG. l, to the opposite side of such center, as shown in FIG. 2, thus to eect the snap toggle movement from the FIG. 1 to the FIG. 2 position.

The spring toggle switch will remain in the latter, open position of FIG. 2 so long as the center 32 determined by the thermostat is 'above the fixed toggle center 29.

As the bimetal retreats from the FIG. 2 toward the FIG. 1 position, the center 32 will lower below the dead center position 29, allowing the spring strut 28 to snap the switch blade back into the FIG. 1 position with the switch contacts 25, 26 again in engagement.

The switch mechanism as shown in FIGS. 3 and 4 is all carried by a channel form base 34, which is pivotally mounted in the case on a cross pin 35 and the base is positioned by an adjusting screw 36l and control knob 37.

A special feature of the control screw is that it has a shouldered terminal point 38 seated in and projecting from the lower end of the screw, backed up by a spring 39 and abutment screw 46, providing a desirable amount of yield in the holding action of the adjustment screw.

Service wires 41 and 42 are connected with the iixed end of the switch blade and with the stationary switch contact 26.

The terminals of these wires are of special construction, being shown each as a sleeve 43, FIG. 7, crimped over the bared end of the wire, having an abutment flange 44 at the back and headed over as a tubular rivet at the front end at 45.

This avoids the use of screws and assures the irm securing of the wire to the terminal and the securing y of the terminal to the switch mechanism.

3 movement of the V-strut, as indicated in exaggerated form in FIG. 8.

The interelation of these mechanical movements adds up to a greater and faster movement of the combined parts, giving a quicker and more positive responsive action.

With slight movement of the pressure point 32 on the spring switch blade past the dead center 29 of the spring toggle, the switch blade will snap over from the FIG. 1 to the FIG. 2 position and will remain in that position so long as the pressure center 32 remains there but as the pressure point 32 is relieved from the FIG. 2 to the FIG. 1 position, travelling to opposite side of the dead center, the switch blade Will be snapped back to the closed circuit position, FIG. 1.

The V-strut may be made of high expansion material, so as to add to the fast expansive movement of the unit.

The quick responsive action of the unit renders it suitable for many purposes, particularly Where slight variations in temperature :and corresponding control are important.

What is claimed is:

1. Snap action thermostat with amplied actuating movement, comprising a heat transfer plate,

=a at bimetal strip having substantially its entire length contiguous with said heat transfer plate, said bimetal being mounted at a substantially center point in fixed engagement on said plate, with opposite ends of the same free to curl up away from the plate under thermostatic action,

said free opposite ends of said bimetal strip being bent up into angularly extended abutment lugs,

said abutment lugs having openings therein,

a spring tensioned switch member, and

an expansible and contractable thrust transmitting strut interposed between said bimetal and switch member,

said strut being of inverted V-shaped formation having divergently inclined legs yieldingly connected at the center and provided at the rdivergent ends of the same with lugs extending through said perforations in the abutment lugs of the bimetal strip,

whereby t0 :add thrust generated by the closing movement of said legs .to the movement generated by the free ends of said bimetal strip.

References Cited UNITED STATES PATENTS 2,382,182 8/1945 Strong 200-138 X 2,689,290 9/1954 Mettler 200--138 3,193,649 7/ 1965 Uhlich 200-138 3,193,792 7/ 1965 Shea 174-75 X FOREIGN PATENTS 1,070,758 10/ 1959 Germany.

BERNARD A. GILHEANY, Primary Examiner.

R. L. COHRS, Assistant Examiner.

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