US2349126A - Thermostatic element - Google Patents

Description

May 1s, 1944.

D. W. ABERNATHY THEARMOSTATIC ELEMENT Filed June 9, 1942 Patented Mayl, 1944 THERMOSTATIC ELEMENT David W. Abernathy, Chicago, lil., assignor to Products Development, Inc., Chi corporation of Illinois un nl".

' Application June' 9, 1942, Serial No. 446,332

This invention relates generally to thermostatic elements and more particularly to a novel and improved element to be used inv connection with the heating elements used to heat wound tresses of hair as for the permanent waving thereof.

'I'he primary object of the invention is to provide a novel and improved thermostatlc element.

A further object of the invention is to provide a novel thermostatic element which is simple and compact and invwhich the bl-metal element is not subject to undue stress at low temperatures.

A further object of the invention is to provide I a novel and improved thermostatic element which will respond accurately to high tempera@ tures for which it has been adjusted.

A further object of the invention is to provide a novel thermostatic element which may be easily associated with the shell of a heater clamp so that same is responsive to the heat immediately.

A still further object of the invention is to provide a novel heater clamp having a thermostatic element associated therewith.

Other objects of theinvention lie in the speciiic constructional details of the'thermostatic element and the heater clamp.

With the foregoing and other objects in view which. will appear as the description proceeds, the invention consists of certain novel features of construction, arrangement and combination of parts hereinafter fully described, illustrated in the accompanying drawing, and particularly pointed out in the appended claims, it being understood that various changes in .the form, proportion, size and minor details of the structure may be made without departing from they spirit or sacrincing any of the advantages of the.

invention.`

For the purpose of facilitating an understanding oi my invention, I have illustrated inthe accompanying drawing a preferred embodiment thereof, from an inspection of which, when considered in connection with the following descr'iption. my invention, its mode of construction, assembly and operation, and many of its advantages should be readily understood and appreciated.

Referring to the drawing in which the same characters of reference are employed to indicate corresponding or similar parts throughout the several iigures of the drawing: I

Fig. l is a perspective view of a heater clamp suchas used in heating wound tresses of hair (Cl. 20G-138) in the permanent waving thereof, having my invention incorporated therein.

Fig. 2 is a perspective view of one of the jaws of the clamp broken away in order to show the inner construction thereof.

Fig. 3 is a. sectional view taken through a clamp member taken generally along the line 3-3 of Fig. 1. Y

Fig. 4 is a side elevational view of the thermo- 10 static element. i

Fig. 5 is a perspective view oi the element prior to being installed into the shell of the clamp jaw.

In the permanent waving of hair by'means of 'l5 electrical heaters, it has been customary to utilize thermostats for the purpose oi' maintain- 'ing the temperature of the heaters substantially constant. This is desirable ,for reasons of con trol and uniformity. In the-manufacture oi' the 20 heating clamps the thermostatic element is associated with said clamps and lis adjusted to open the circuit to the heating elements when a cer- 'tain predetermined temperature theoretically exists at the clamp jaw. The types of theru 25 mostatic elements heretofore used have been constructed in such manners that the ci-metallic element, referred to sometimes as the lli-metal, is subject to undue stress at the early part of its life and hence its characteristics are not as con- 30 templated. It is hence necessary to replace the.

thermostats or readiust them often, or provide compensation for the change of characteristics in some other manner. Either excess heat or fluttering may' result from misadjusted thermo- 3'5 static elements.

. curing is that reverse stress is placed upon the Probably the greatest cause for the strain ocbi-metal when same is subject to low temperal tures, as for example when transported in coldl 0 weather or stored in unheated warehouses. Even 46 bly.

My newy invention besides eliminating the disadvantages above `described is so small and compact that instead oi' being associated with the heater clamps as has heretofore been customary,

' lo it may be associated with jaws of the clamps at a point immediately adjacent the heating element andhence may more accurately respond to the proper temperature and does not depend for l its operational heat upon that portion ofthe heat as? from the element which is conducted to it alena the shell as has been the case of prior thermostaidc elements.

Referring now to the speciiic details of the invention, the reference character It designates generally a clamp of the type used in giving the so-called machine permanent wave. The clamp Il comprises apairof clamp arms il terminating in iaws f I! which have the inner surfaces I3 thereof concave in order to hold and heat therebetween a trees of hair which has been suitably wound or formed to some desired configuration. Electrical wires Il supply current to a heating element which has been generally shown as a lmica member Il wound with resistance wires II,

embedded in a ceramic material or the like I1 and the whole being retained by a covering member Il. The outer portion of the jaws il comprises a metal shell il which may have its edges 'and .may be integrally formed with the arms u.

Said arms Il are provided with ears 2| which cooperate with a pin I! extending therethrough so that the arms If may pivot with respect to one another. A wire spring 2l normally urges the clamp jaws I2 into engagement with one another.

integrally formed with the shell i9, I have provided a cavity Il which is on the outer side of the Jaw Il. The shell being formed of sheet metal. the cavity Il is struck therein at the time of the drawing of said shell. Within this cavity Il. I have aiiincd my thermostatic element Il. Of course the cavity appears from the outside of the clamp member Il as a somewhat rectangular protubersnee :l upon the cuter surface er the shell II. The thermostat'is thus seen to be almost immediately next' to the heating element contained in the covering member Il. Hence heat from the element will impinge directly upon the thermostatic element 24 and cause same to operate in the desired manner,

The thermostatic element comprises a substan-` i tially rectangular base member 2i adapted to f ggly nt into the cavity Il. The base member extending danses 21 along portions of its longer edges which are adapted to engage the inner walls of the cavity 2|. The base rdem l ber 26 is lined with a layer of ilber insulating vpalier 2l. At one end of the element 2l the base member il has a pair of integrally formed lugs II engage the ends 3l ofasmall strip ll of resilent metal such as phosphor bronze, which strip is laid across the end of the base member It.

4The centralportion ofthe strip Il isbentup-` wardlyassbown ats! andacontactpoint Slis provided thereon. Obviously the mounting of the contactA point is more or less resilient. It will be noted that for heat insulation I have provided a layer of asbestos paper u between the fiber per ayer zum the end n of me strip u.

The opposite end of the base member It is provided with a second' strip 8l of resilient metal such as phosphor bronze engaged beneath bent over lugs Il and insulated by said layer of fiberv paper 2l and asbestos paper Il. This strip 3l is fiat and is provided with a portion 31 extending forwardly of the element il, bent back upon itself as at Il to form a nat leaf spring, and terminating at Il. At the termination point 3l, I have 1l Vntages should be readily under-sima from the welded the ends of a bi-metal member Il and a long strip of resilient metal 4I which is provided on the free end thereof with a contact point 42 adapted to normally engage with the contact point Il. The ends of all three members $0, l0

and Il are so intimately joined together by welding that they together foi-m` a block II' which moves as a unit. 'Ihe block II' is tapped and suitably threaded for the reception of an adjusting screw Il the bottom end of which is adapted to contact the top of the strip Il.

'Ihespringlltendstoserveasapivotandits arms are so biased that they tend to close upon one another. Thus when the adjusting screw is rotated to cause the arms to open, the tension of the free end of the member Il and the pressure between the contact points l! and Il is increased.

It will be noted that the terminus of the bimetal member Il is somewhat thicker than the body of the member 4l and hence there isa space M between the upper face of the bi-metal member Il as caused by ordinary warm weather without said bi-metal enticing against the bot, tom face of the metal strip Il. Because of this there is'obviously no stress placed in the bimetal which would cause same vto become permanently strained.

As for the reaction oil' the bi-metal I when itissubiecttolowtemperatm'es,thatisalsoper mittedinorderthattberebenoreversestress placed upon said iii-metal.' It will be noted that the iii-metal 4l is substantially "hosting," that istosay,ifitshouldtendtocurldownwardly there is nothing to impede its movement. Considerable space may be provided foreven subaero temperatures. The bi-metal thus retains its resilience throughout various temperature changessothatwhenitistlnallyuseditvill respond to the exact temperature for which it has been adjusted. At that temperature the bimetal 4l moves upwardly.. asviewed in Pig. 4, engages against the bottom face of the strip ll and lifts the contact Il from the contact ll. Inasmuch as there has been no strain placed upon the bi-metal. it isresilient to the extent where it opposes the reversing movement of the strip Il and hence the return of contact will be gradual, eliminating flutter.

In prior thermostatic elements the bi-metal is usually in some manner connected with the contact carrying member so that where the element is subjected to low temperatures the bi-metal is considerably stressed since its motion is opposed by the ilxed contact. This may result in the permanent strain above referred to. As to the reverse reaction of the element in wann weather. where the' bi-metal is associated with the ccntactdirectly,acertainamountofthetension between the contacts is relieved. making for uncertain break temperatures.

The strips 8| and Il are each provided with a wine lead Il and 4l respectively. whereby same may be connected into the circuit of-the elecmeal heater element in order to act n a switch for said circuit in the well known manner. V

Inviewoftheabovedeacriptionitshouldbe apparent that' not only have I provided anovel Y and ingenious thermostatic element which is not only emcient and positive in operation, but which 10 iscompactandwellarrangedsothatsamemay beincorporatedintoasmalispacesnehas the cavity u of the clamp as described herein.

Itisbeiievedthatmyinvention,itsmodeof construction and assembly, and many of its adforegoing without further description, and it should also be manifest that while a preferred embodiment of the invention has been shown and described for illustrative purposes, the structural details are nevertheless capable of wide variation within the purview of my invention as defined in the appended claims.

What I claim and desire tov secure by Letters Patent of the United States is:

1. A thermostatic switch adapted to open an electrical circuit at a predetermined temperature, comprisinga base member, a resilient fixed contact supporting member attached to said base at one end thereof and having a contact provided thereon, resilient movable contact supporting means attached to the base member at the opposite end thereof and comprising a strip spring may control the pressure between the contacts, the free end of said ybi-metal strip being adapted to engage with a side of said resilient strip for causing disengagement between said contacts when the bi-metal member is subject to.

said predetermined temperature.

bent upon itself to form a substantially U-shaped spring, one end thereof being fixed to the base member, a bi-metal strip and a resilient contact the end of said bi-metal strip being connected to the second end of said spring, whereby said spring may control the pressure between the contacts.

2. A thermostatic switch adapted to open an electrical circuit at a predetermined temperature, comprising a base member, a resilient fixed contact supporting member attached to said base at one end thereof and having a contact provided thereon, resilient movable contact supporting means attached to the base member at the opn posite end thereof and comprising a strip bent upon itself to form a substantially U-shaped spring, one end thereof being fixed to the base 3. A thermostatic switch adapted to open an electrical circuit at a predetermined temperature,

comprising a base member, a resilient fixed contact supporting member attached to said'base at one end thereof and having a contact provided thereon, resilient movable contact supporting means attached to the base member at the opposite end thereof and comprising a strip bent upon itself to form a substantially U-shaped spring, one end thereof being fixed to the base member, a bil-metal strip and a resilient contact carrying strip having a contact on the free end thereof for engagement with said fixed contact, the end-of said bi-metal'strip being connected to the second end of said spring, wherebysaid spring may control the pressure between the contacts, the free end of said bi-metal strip being adapted to engage with a side of said resilient strip for causing disengagement between said contacts whenthe br-metal member is subject to said predetermined temperature, but being normally spaced from said resilient strip and free to bend away from said strip when the temperature is low. 4

'DAWD W. ABERNA'I'HY.

member, a bi-metal strip and a resilient contact

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