US1746908A - Automatic oven-temperature control - Google Patents

Description

Feb. 1l, 1930. J. P. scHoENBERGER AUTOMATIC OVEN TEMPERATURE CONTROL Filed Jan. l5. 192'? m INVENTOR.

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Patented Feb. 11, 193@ STATES PATENT cries JOHN P. SCHOENBEBGER, F SAN JOSE, CALIFORNA, ASSIGNOR OF TVJO-THIRDS T0 DANIEL RYGEL, OF OAKLAEIE, CALIFORNIA., AND E. J. BURT, OF SAN JOSE, CALT- FORNIA.

AUTOMATIC OVEN-TEMPERATURE CONTROL Application led January 15, 1927. Serial No. 161,333.

This invention relates to improvements in control devices tor the elements oit' electric cooking ovens to control the heat ot the oven, and particularly represents an improvement over the torm ot control device shown in m cri-pending application tor patent, filed July 31st, 1926, Serial No. 126,125.

The principal object ot the present invention is to provide a control apparatus for the l0 same purpose as the former but ot simplied and more compact torni. such as is less liable to become deranged in action, which is easy to apply to the oven and which may be readily removed as a single unit whenever necessary. A further object ot the invention is to provide the control apparatus with a plurality of switch or Contact points arranged in cooperating pairs which may be connected to oney or more oven heating elements and the opening and closing ot whose circuits while taking place simultaneously will loe independent of each other.

A further object ot the invention is to produce a simple and inexpensive device and yet one which will be exceedingly effective for the purpose tor which it is designed.

These objects l accomplish by means ot such structure and relative arrangement of parts as will fully appear by a. perusal of the following specification and claims.

ln the drawings similar characters of reference indicate corresponding parts in the several views:

Fig. 1 is a sectional elevation ot my improved torm ot' control apparatus.

Fig. 2 is an outer end view ot the same with the cover and operating handle removed.

Fig. 3 is an inner end view of the housing member with the cap removed.

Referring now more particularly to the characters ot reference on the drawings, the numeral 1 denotes the outer side wall ot an oven or conventional form having an electric heating device mounted therein and preferably depending from the inner top wall 2 ot the oven, each heating ldevice including a heating element 3 of suitable character.

My improved apparatus to control the opening and closing of the element circuit by the heat generated in the oven by said element comprises a main centrally oriiiced supporting plate 4t rigidly secured on the outside of the wall 1. Projecting inwardly oi' the oven from the plate is a tubular housing- 5 of expansible metal in which adjacent its inner end is rigidly mounted a longitudinally slotted block G having a transverse pin 7 therethrough. Pivoted at one end on the pin is a lever 8 ot a metal having the same coefficientot expansion as the housing. The lever eX- tends to a point adjacent the plate et and at said end is secured an extension 9 which projects through and beyond the plate and supports a cross bar 10 ot insulation material on its outer end. Projecting loosely7 through the bar 10 on each side ot the support 9 tor tree vertical movement are pins 11. rlhe lower ends ot these pins carry contact pads 12 arranged to normally engage similar pads 13 mounted on brackets 14. rllhe brackets are secured to the outer tace of a centrally oriticed disc 15 of porcelain or the like, which disc is removably secured to the plate 4 by suitable means such as screws 16. @n the upper ends ot the pins 11 are mounted binding nuts 17 which are clear of the cross bar 10 a Certain distance when the contact pads are engaged.

Disposed in the housing 5 and extending lengthwise under and normally parallel t0 the lever 8 is a bar 18 ot non-expansible metal. This bar at its inner end rests on the block 6 or on the bottom ot the housing and has at such end an upstanding lug 19 adapted to engage a shoulder 2O iormed on the lever 8 and disposed sulistantially radial to and below the pivotal pin head ot the lug, or toward the free end oiE the lever with respect to said lug. The bar at its opposite end projects through the plate 4 and member 15 and is threaded at such end to engage a tapped sleeve 21 on the outer end of which is mounted a. calibrated handle 22. The sleeve at its inner end bears against a plate 28 mounted inside and against the plate 4, to which the housing 5 and said plate 23 are attached. The sleeve is held in constant engagement with said plate 23 by a spring 24 engaging the opposite. end ot the sleeve and also pressing against a cover member 25 which is removably but rigidly secured to the plate 4 and which encloses the contact structure and adjacent parts. The handle and sleeve therefore cannot move longitudinally and the rotation of the handle will cause the bar 18 to be moved lengthwise in the housing, so that the distance between the lug 19 and shoulder 20 may be altered. The extension member 9 also projects through the plate 23 above the bar 18 and when the lever 8 is in its normal or cold condition, rests on said plate 23 so that the downward movement of the extension and lever is limited. The bar 18 cannot rotate since it is rectangular where it enters the block 6 and the slot in the latter is shaped to correspond. lt will therefore be seen that as the housing 5 and lever 8 expand with heatthe shoulder 2O approaches the non-moving lug 19. When these parts engage each other, further eX- pansion of the housing causes the vlever to be raised about its pivot and as soon as the slack between the nuts 17 and the bar 10 is taken up the contacts will be broken, as will be evident. rlhe length of the lever is such that a'very slight movement of the shoulder is suiiicient to impart considerable movement to the opposite end of the lever, so that the breaking of the contacts takes place without any undue lag.

lt will be evident that the amount of ei;- pansion of the housing and lever (which is governed by the temperature in the oven generated by the element 3) before the engagement of the lug and shoulder and the consequent breaking of the contacts takes place,is determined by the initial setting of the lug relative to the shoulder. lt is therefore an easy matter to calibrate the handle so that the rotation of the same a certain amount relative to a fixed mark on the adj acent face of the cover 25, will accurately determine at what temperature the contacts will break. lt may be possible that the housing 5 after a certain period of use will become permanently lengthened or distorted so that the rotation of the handle to a predetermined position no longer causes the breaking of the contacts at a corresponding heat. rlortake care of such contingency l mount the handle 22 on a core 26 which is rigidlyV screwed onto the sleeve 2l, and normally Ahold the core and handle immovable relative to each other by a set screw 27. Upon loosen,- ing the set screw the handle may be rotated on the core independently of the sleeve, so that no movement will be imparted to the bar 18, and the calibration of tie handle relative to the 'fixed mark on the cover may be then reset as may be necessary. When the handle has been moved to a proper position the set screw is again tightened up.

lf it is desired to remove the device from the oven as a unit, the screws el which secure plate 4 to the oven, and which are accessible without removing the cover 25, are withdrawn. If it is desired to remove the cover, the handle and core are unscrewed from the sleeve, which permits the wiring as shownto be disconnected and the interior parts inspected. The entire structure may then be withdrawn from. the oven, and the various parts may then be dissembled from each other.

Each of the oven elements may be wired to one of the brackets and the corresponding contact pin in any suitable manner so that the circuit to the element will be broken when the adjacent contacts 12 and 13 are separated. It will be seen that by the use of separated pairs of these contact units two or more heating elements may be connected to a source of current with each element circuit independentof each other, and yet in such manner that all circuits will be broken simultaneously.

The device is therefore suitable to be used,

whether the oven-is of the single or double element type. i Y

rlhe purpose of the increasing height of the housing toward itsk outer end is to enable the operator to adjust the bar 18 when the circuit has been broken with a high heat, and it is desired to make adjustments to cause the contacts to be broken at a lower heat, while the housing is still in a hot and expanded condition. To make such adjustment it will be evi-f dent thatthe lug 19 on the bar 18 will be pulled closer toward the outer end of the de-v vice, and when such movementn of the lug takes place when the shoulder 20 is already engaged therewith, it is necessary of course i that sufficient vertical space Vbe had in the outer end of the casing to allow the lever to swing upwardly as the lug is thus adjusted.

As far as the operation of the device is concerned, the lever 8 could be made non-eXpansible. By making it expansible however and with the same coefficient of expansion as the lever, the contact points are always kept in direct vertical alinement.

W'hile l have shown and described this device as being particularly intended for use in an oven, it is also adapted for the control of the temperatures of rooms, furnaces, fluids, etc. when electricity is used to heat or control heat, orto operate motors in connection with heating devices.

From the foregoing description it will be readily' seen that I have produced such a device as substantially fulfills the objects of the invention as set forth herein.

While this specification sets forth in detail the present and preferred construction of theV device, still in practice such deviations from such detail may be resorted to as do not form a departure from the spirit of the invention,

as defined by the appended claims.

Having thus described my invention'what I claim as new and useful and desire to secure by Letters Patent is:

1. A thermostatically controlled switch structure including a horizontal lever adapted to be projected into a zone oi heat, an expansible housing surrounding the lever, a transverse pivot for the inner end of the lever secured in the housing, a structure adapted to be mounted in a iixed position to which the housing is secured at its end opposite to the pivot, a contact mounted on the free end of the lever, a contact iixed on said structure under the lever contact and normally engaged thereby, a non-expansible bar extending from said structure along and under the lever to the pivoted end thereof,4

,said lever having a substantially radial shoulder below its pivot, and a lug upstanding from the bar beyond the shoulder to be engaged thereby after the housing has expanded a certain distance.

2. A thermostat switch comprising` a longitudinally expansible member to be projected into a zone of heat, a support for the outer end of said member, a lever extending lengthwise of said member from the support and pivoted onto the member adjacent the inner end of the latter, cooperating contacts mounted on the support and the outer end of the lever, means cooperating with the lever to cause the same to swing on its pivot only after said member has expanded a ore determined extent, and means operable from the support for enabling the degree of expansion of said member necessary to swing the lever, to be altered at will.

3. A thermostat switch comprising a longitudinally expansible member to be projected into a zone ot heat, a support for the outer end of said member, a lever extending lengthwise of said member Jfrom the support and pivoted onto the member adjacent the inner end ot the latter, whereby said mem` ber expands longitudinally the adjacent end of the lever will move correspondingly, said lever adjacent its pivot having a substantially radial shoulder, a lug ixed with respect to the member to be engaged by said shoulder as the lever moves with the member, fixed and movable contacts mounted on the support and lever respectively, and means operable trom the support for adjusting the setting of the lug longitudinally of the lever.

4t. A thermostat switch comprising a longitudinally expansible member to be projected into a zone of heat, a support for the outer end of said member, a lever extending lengthwise oit said member from the support and pivoted onto the member adjacent the inner end of the latter, whereby when said member expands longitudinally the adjacent end of the lever will move correspondingly, said lever adjacent its pivot having a substantially radial shoulder, a lug fixed with respect to the member to be engaged by said shoulder as the lever moves with the member, a non-expansible bar to which the lug is secured projecting therefrom to the support,

and means applied to the support end of the bar for moving the same longitudinally, and cooperating contacts on the support and the adjacent end of the lever.

5. A structure as in claim 2 in which the lever is longitudinally expansible and has the same coeihcient ot expansion as said member, whereby the alinement of the contacts is maintained regardless of expansion.

6. A thermostat switch comprising a longitudinally expansible member to be projected into a zone ot heat, a support for the outer end of said member, a lever extending lengthwise of said member from the support and pivoted onto the member adjacent the inner end of the latter, whereby when said member expands longitudinally the adj acent end of the lever will move correspondingly, said lever adjacent its pivot having a substantially radial shoulder, a lug fixed with respect to the member to be engaged by said shoulder as the lever moves with the member, a non-expansible bar to which the lug is secured projectingtherefrom to the support, a turnable but longitudinally immovable handle mounted on the support and threaded onto the adjacent end of the bar, and means preventing rotation of the bar.

7. A structure as in claim 4, with guide means for the bar to prevent turning thereof mounted in said member adjacent the pivoted end of the lever.

In testimony whereof I ax my signature.

JOHN P. SCHOENBERGER.

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