US1931731A - Thermo-regulator - Google Patents

Description

I Oct. 24, 1933.

P. E. KLOPSTEG THERIO REGULATOR Filed Dec.

' on the line 6-6 the type shown in the employed in the'worm assembly; and

I with the worm gear.

Patented Oct. .1933.

UNITED sures PATENT OFFICE 'rnnnuo-aeam'ron Paul'E. Klopsteg, Evanston, 11]., amino:- to

Central Scientific Company,

Illinois Application a corporation oi" Decemger 21, 1931 Serial No. 58 .26 3 Claim. (01.290-138) to thermo-regulators of I De Khotinsky Patent No. 1,375,780, issued April 26, 1921 and bs'for its principal object to improve the same. Further and other objects and advantages will This invention relates become apparent as the disclosure proceeds and the description is read inconiunction with the accompanying drawing in which Fig. 1 is a perspective view of the improved thermo-regulator;

Fig. 2 is a front view of the thermo-regulator with the cover removed;

Fig. 3 is a sectional view taken on the line 3-3 of Fig. '2, the contact arm and its associated parts being shown in elevation Fig. 4 is a transverse, sectional view taken on theline4-.4ofFig.3';

Fig. 5is afragmentary sectionalview taken on the line 5-5 of Fig; 3 showing particularly the novel mounting of the worm;

Fig. 6 is a fragmentary, sectional view taken of Fig. 5';

Fig. '7 is a perspective view of the journal guide Fig. 8 is a perspective view of the resilient clip which holds the worm in positive engagement But this specific. illustration and the correspondingly specific description are for the purpose of disclosure only for it is realized that the invention may be variously embodied within the scope of the appended claims.- I

The thermo-regulator is primarily intended for. use in controlling thetemperature of electric ovens, but its use is not so limited. It may obviously be used wherever'a thermostatic control of an electric current is desired.

As explained in the DeKhotinsky patent above referred to, the device includes a bi-metallic helix which contracts and expands in response to temperature changes in the ambient air'and thereby actu'ates a" movable contact to and from circuit closing position. When the circuit is closed, an

electric heateris put into operation which therebyraises' pands the thermoesensitive helix and after a given movement will openthe heater circuit. A

more detailed explanation of the device will be given as the description proceeds.

In its preferred form, ,the thermo-regulatorl comprises a base 10 having integral end walls 11 and 12. The base is securely mounted on the exterior of the oven by a screw (not shown) passing through the aperture. 18 in the boss 14. The

preventsthe baseirom ing screw as a pivot.

- A binding 90 the wall 11 of thermoesensitive means,'generally designated. 15' passing through an aperture it in the boss 17 turning about the fastenpost 18 is insulatedly eunted'on' the base and is connected away from the web and projects through the temperature withinv the oven, ex-

' arm 38 which, in the form connected by conductors and 26 to the other sideof the power line.

A pair of relatively'flxed contact members 2'7 and 28 are adjustably supported in metallic contact holders 29 and 30 which are in effect continuations of the binding posts 19 and 20. These contacts, it will be understood, are insulated from the base and from each other.

The contacts 27 and 28 are adjustable for position by rotating the threaded shanks 31 and 32 which are in threaded engagement with the contact holders 29 and 30, respectively.

A pair of movable contacts 33 and 3 mounted on thin, resilient supporting me bers 35 and 36 which are in turn clamped to the web 3"! of a contact arm, generally designated 38', by sinall rivets ,39. A spacer 40 holds the contacts 37 for a purpose later to be described. v 1

The moving contacts 33 and 34 are controlled are by the thermo-sensitive means 15 extending into the oven in the path of circulating air. This -means comprises a tubular stem 41 tightly fitted within the bore 16 and telescopically supporting a worm gear shaft 42 which projectsa slight distance beyond the stem 41 into'the interior of the housing, as indicated at 43. A worm gear 44 is rigidly secured to this end of the shaft.

The outer end of the plied with a collar 45 that is prevented from having relative rotation with the shaft 42 by a set screw 46. Mounted on the collar by meansoi; a screw 47, or similar means, is a bimetallic helix worm gear shaft is sup-- 48 composed preferably of an outer layer 49 of invar, and an inner layer 50 of brass. The outer extremity of the helix is rigidly fastened to the bent end 51 of a torque shaft 52 which is mounted within the hollow worm gear shaft 42 the worm gear 44, the latter constituting abearing for its inner end.

An insulating block 53 slips over the inner end of the torque, shaft and is held in place by a set screw 54 that seats upon a flattened edge 55 of the shaft toinsure that there will be no relative movement between the block and the shaft.

The insulating block 53 carries. the contact shown in the drawing, has a bowed mid-section 56 that merges with the web 3'7. The contact arm is at all times in electrical connection with the binding post 18 by meansoi a braided ribbon conductor s'l which is bent inwardly at 58 and fastened to the insulating block 53 by machine screws 59, 59. The machine screws are adapted to pass throughthe block and the. web 60 of the contact arm so that by appLving the nuts 61,61, the braided conductor 5'7 and the contact arm will be simultaneously clamped to the insulating block. The use of a highly flexible braided conductor between the binding post 18 and the insulating block 53 otters little or no resistance to the movement of the contact arm and, therefore, is highly-desirable.

that the temperature of the oven is such as to cause the helix 48 to contract, it will beseenthattbe torque armwiilbe slightiyrck. tated to the right (Fig. 2) bringing the moving contacts 33 and 34 against the fixed contacts 2'7 and 28, thereby energizing the heaters 23 and 24. The purpose of mounting the moving contacts 33 and 34 on the thin resilient supporting members 35 and 36 now becomes apparent, for this insures that a slight torque produced on the torqueshaft by the contraction of the helix 48 will cause both heaters to be put into operation, whereas if the contacts were mounted on the less resilient contact arm itself, it might happen that only one contact would be made with the result that one heater would be left out of operation.

One distinct advantage of the thermo-regulator thus far described over the regulator shown in the DeKhotinsky patent resides in the elimination of the base 10 and the thermo-sensitive means from the electrical circuit. In the embodiment of the invention disclosed in the drawing, the electrical circuit from the binding post 18 to the binding post 19 or 20 may be traced from conductor 57, screw 59, contact arm 38, contact supporting members 35 and 36, moving contacts 33 and 34, fixed contacts 37 and 38, contact supports 29 and 30'back to the binding posts 19 and 20. By eliminating the casing and thermo-sensitive means from the electrical circuit, electrical, resistance is somewhat out down and there is no danger'oi shock to the'person manipulating the theme-regulator by contact with the casing.

In a device of this kind, it is necessary to provide means for controlling the temperatures at which the circuit will be opened and closed. This is accomplished by means of a worm 62 meshing with the worm gear 44. Upon rotating the worm by means oi the control knob 63, the worm gear shaft 42 displaces the inner end of the helix 48 a proportional distance which has the eflect of changing the temperature at which the closing of the circuit takes place.

Experience has shown that the back lash inherent in the worm gear assembly shown in the DeKhotinsky patent detracts from the accuracy of the device. Novel means are; therefore, provided for overcoming this defect.

The worm 62 is provided with bearings 64 and 65, the latter of which is extended beyond the edge of the base 10 and is rigidly connected to the control knob 63. The bearings are held in longitudinal alinement with respect to the worm gear by means of a journal guide 66 fastened to the base 10 by screws 67. The guide comprises arms 68 and 69 joined together by a connecting web '10 of substantial cross section. The arms each have an open slot '7-l corresponding in width to the diameter of the worm bearings. The base of the slots are rounded as at 72 and communicate with transverse channels 73.

when the journal guide is screwed to the base in its appropriate position, the wormbearings rest within the slots '71 but the guide is so positioned that-the rounded bases 72 of the slots do not force the worm into iirm engagementwith the worm gear. This, however, is accomplished by a resilient clip 74 fastened to the base by screws 75 and provided with arms 76 which are adapted to fit within the channels 73 of the journai guide, and press against the bearings. The resilient arms 76 cause 'an engagement of the worm with the worm gear which is devoid of beck-lash and which will remain that way regardless of wear, since the wear is taken up by the resilience of the clip.

A cover, generally designated 77, is adapted to slip over the end walls 11 and 12 of the base and enclosethe thermo-regulator. The cover is held in place by screws 78' and the front portion is provided with windows '19 to expose the in terior of the device. To prevent dust and other deleterious matter from entering the housing, it is preferred that the windows 79 be provided with a glass cliisurc 80 which is held against the front 0! the cover by resilient lugs 81.

The cover may be provided with an insulated sheet 82 on the side which is adjacent to the braided conductor 5'7 in order to insure that the casing will not become electrified.

A pair of apertures 83 provided in the cover give ready access to the contact carrying screws 31 and 32.

Although the thermo-regulator is not equipped with an absolute scale for indicatin the temperatures directly, the control knob is provided with graduations 84 cooperating with the index 85 on the cover so that comparative readings may be taken.

Preferably a condenser 86 is connected across the conductors 19 and 26 to prevent arcing between the flxed and moving contacts.

From the above, it will be apparent that the improved regulator is more sensitive to heat fluctuations and more accurate in temperature control than the DeKhotinsky device above identitled.

What I claim, therefore, is:

1. In a device of the class described, a relatively fixed contact, a movable contact, therrncsensitive means connected to the movable c0ntact including a bimetallic helical coil, means for regulating the thermo'sensitive means including a worm. having end. bearings, a worm gear adapted to iniermesh therewith, a journal guide for holding the worm in proper alinerncnt with relation to the gear, and a resilient clip pressing on the hearings to cause firm engagement of the worm with the gear.

2. In a device of the class described, a relatively fixed contact, a movable contact, thermo-- sensitive means connected to the movable con tact, means for regulating the merino-sensitive means including a worm having end bearings, a worm gear, a. journal guide adapted to fit over the bearings and hold the worm in proper alinement with relation to the gear, and resilient means urging the worm into i'irm engagement with the gear.

3. In a device of the class described, a'relatively fixed contact, a movable contact, thermosensitive means connected to .the movable contact, means for regulating the thermo-sensitive means including a worm having end bearings, a worm ge'ar,,a journal guide having-longitudinally extending open slots'receiving the bearings and transverse channels communicating with the slots, and a resilient clip provided with arms adapted to ht into said channels and urge the worm into thin engagement with the gear.

' PAUL n moss'rsa.

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