US1174006A - Thermostatic circuit-breaking apparatus for electrical heaters. - Google Patents

Description

Jv. E. HARVEY.

THERMOSTATIC CIRCUIT BREAKING APPARATUS FOR ELECTRICAL HEATERS. APPLICATION FILED APR. 3. I9I5.

l. E. HARVEY.

THEIIMosIAIIc CIRCUIT BREAKING APPARATUS-F03 IQLECIIIICHAI IIE'AIEIIS.

v -APPLICATION FILED APR. 3- I9I5AI I 1,174,006.` l Pafentd Feb. 29,1916..

3 SHEETS-SHEET 2.

. J. E. HARVEY. THERMCSTATIC CIRCUIT BREAKING APPARATUS POP ELECTRICAL HEATEIIS.

APPLICATION FILED APIT. 3. 1915. 1,174,006. Petented Feb. 29,1916. 3 SHEETS-SHEET 3. /55

To all 'whom t may concern.'

v JOHN E. HARVEY, 0F MILTON, MASSACHUSETTS.

i THEMOBTATC CIRCUIT-BREAKING APPARATUS FOB ELECTRICAL HEATEBS.

Specication of Letters Yatent.

I Patented Feb.'29, 1916.

Application lecl A111113, 1915. Serial No. 18,906.

Be it known that I, JOHN E. HARVEY, a citizen of the United States, -and resident of Milton, in the county of Norfolk and- State of Massachusetts, have invented cer-v tain new and useful Improvements in Thermostatic Circuit-Breaking Apparatus for Electrical Heaters, of which the following is a specification.

This invention relates to means for automatically breaking an electric circuit -through a heating unit when the heat rises above a predetermined degree, and as here shown is embodied in a sterilizing apparatus, which includes a tank; a heating unit adapted to heat the bottom of the tank; a

, movable circuit-closing and breaking member in circuit with the heating unit, and held in circuit-breaking position; arresting means adapted to hold said member in circuit-closing position; thermostaticmeans connected with said arresting means in such manner that upon the overheating of the bottom of the tank, in consequence of the evaporation of water therefrom, the said movable member is released and caused to break the circuit and thus discontinue the heat.

Of the accompanying drawings forming a part of this specification: Figure 1 represents a longitudinal section of a sterilizing apparatus embodying my invention, the plane of said section being indicated by the line 1--1 of Fig. 2; Fig. 2 represents a top plan view, the tank being removed, a part of the heating unit broken away and certain parts shown in section; Fig. 3 vrepresents a section on line 3-3 of Fig.2; Fig. 4 represents a section on line 4 4 of 3, looking upwardly; Fig. 5 represents a fragmentary elevation of a portion of the tank and the bracket and detent holder; Fig. 6

A represents a section on line 6 6 of Fig. 3; .Fig 7 represents a perspective view'of the bracket; Fig. 8 represents a perspective view p of the inne'r section of the detent lever; Fig.

9 is a view similar to Fig. 2, showing a different embodiment of the invention; Fig. 10 represents a section on line 10-10 of Fig. 9; Fig. 11 represents aV section on line 11-11 of Fig. 9; Fig. 12 represents a fragmentary perspective view showing details hereinafter referred to.

Referring rst to Figs. 1 to 8 inclusive,- 12 represents a casing which may be of sheet metal and of rectangular form, and is supwith nuts 12b.

ported by a horizontal base 13 having a flange 13L which surrounds the lower edge portion ofthe casing, the base being provided with legs 13?. As here shown, the

\ horizontal portion of the base has an opening 13 covered by a relatively thin sheet metal bottom plate 13d, the other portions of the base being preferably formed as a single casting. The casing is provided with downwardly projecting bolts 12 offset inwardly om its inner surface and passing through holes in the base, said bolts being provided The said bolts and nuts detachably secure the casing to the base and permit the heating unit and other parts hereinafter described, supported by the base, to be assembled before the casing, the tank, and the hereinafter described thermostat and detent lever supported thereby are located on the base.

14 represents a tank attached at its upper edge to-the upper edge of the casing 12, the sides of the tank being preferably inclined, as shown by Figs. 1 and 3, to form an air space. -The bottom of the tank is elevated above the base to form a space in which the lhereinafter described heating unit, the ther- I preferably interposed between the body 17 and the bottom of the pan to prevent the downward radiation of heat. The pan is supported and spaced from the base by bolts 2O attached to the bottom of the pan and passing through orifices in the base, the bolts eing separable from the base and provided with nuts 21 bearing on oppo-site surfaces of the base, and detachably securing the bolts thereto.

The thermostat is composed of a brass tube 22 soldered or brazed along its entire length to the bottom of the tank, and a steel rod 23, which extends loosely through the tube 22. One end of the rod 23 is provided with an adjustable head or abutment bearing on one end of the tube 22, 'and preferably composed of two nuts 24 engaged with a threaded portion of the rod, one nut I section 30 is formed to detachably engage locking the other at the desired adjustment. One end of the tube 22 is soldered or brazed in a recess 27, formed for its reception in a fixed bracket 27 (Fig. 7) which supports the inner section or member 28 of a swinging detent, forming a part of the circuitbreaking and closing means hereinafter described, controlled by the thermostat. The bracket 27 includes rivet-engaging ears 27h bearing on the bottom of the tank; a perfol-ated ear 27 and an arm 27d havin a perforated ear 27e in alinement with the ear 27, the recess 27a being in an enlargement of the arm, and the bracket being referably cast'in one piece. The detentever section 28 includes a bar 28a formed to enter the space between the bracket ears 27, 27, longitudinally perforated at 28b to receive a fulcrum pin 29, which connects it with said ears; an arm 28 on one end of said bar slotted to receive an eye on one-end of the thermostat rod 23, and perforated to receive a pintle 29, which connects the arm with said rod, and an elongated arm 28d, which extends at right angles with the arm 28.

30 represents the outer member or section of the detent lever, this section being adapted to engage a finger on the movable switch member hereinafter described. The section 30 is pivoted at 31 to the arm 28d ofthe inner section, and has two arms preferably of unequal length. The shorter arm is pressed by a spring 32 against an adjustable stop screw 33 on the arm 28d, said spring being coiled about a fixed stud 32 on the base and having two arms, one bearing on a fixed stud 34 on the base, and the other on a stud 35 in the shorter arm of the lever section 30. The two lever sections 28 and 30 constitute a bell-crank lever, one arm of which is formed by the arm28, and the other by the arm 28d, and the outer section 30. The object of the sectional construction of the lever is to permit the lateral adjustment of its outer end by the screw 33, for a purpose hereinafter described.

The outer end portion of the detent-lever a linger or projection on the movable member of a circuit-closing and breaking switch composed of a fixed member and a movable member, said members, when in contact with each other, closing the circuit through the heating unit, and breaking said circuit when separated. In this embodiment of the invention, I have shown a circuit-closing and breaking device of the knife switch type, one member of the switch including two spaced-apart contact springs or strips, 36, 36, while the other member includes a contact bridge 37 formed to enter and bridge the space between said springs, as shown by Fig. 1, thus closing an electric circuit, which includes the springs, the bridge and the 'is provided with a linger 38 formed to engage a notch 38 in the detent-lever section 30, as shown by Fig. 2. 80

40 represents a spring which is coiledon the fulcrum stud 39 and has two arms, one bearing on a fixed stop stud 41, and the other on a stud 38d on the carrier member 38. Said spring normally holds the carrier in the position shown by Fig. 4 with contact bridge separated from the contact springs, and 'the circuit broken. The engagement of the finger 38 with the detentlever section 30 holds-the contacty bridge 37 in contact with the contact springs, and prevents the spring 40 from acting.

44 represents a push piece movable in a guide 45 in the base, and connected by a link 4 6 with the carrier member 38, said push piece being manually movable to move the finger 38 into engagement with the detentlever notch 30, as shown by Fig. 2.

The electric circuit includes a wire 47 electrically connected by a conducting strip 47a (Fig. 2) with the contact spring 36, and with one end of the resistance wire of the heating unit 16, a wire 48 connecting the opposite end of the resistance wire with a plug 49, and a wire 50 connecting the companion 105 plug 5l with a conducting strip 50a electrically connected with the other contact spring 36a.

When the plugs 49, 51, are connected with a source of electrical energy, and the 11o contact bridge 37 is in the position shown by Figs. l and 2, the heating unit acts to heat the contents of the tank 14.

When the heat of the bottom of the tank exceeds a predetermined degree, as a result, for example, of the evaporation of water from the tank, the resulting expansion of the tube 22 of the thermostat exceeds that of the rod 23, and the tube is caused by its elongation to act on the rod shoulder p formed by the nuts 24 and exert a pull on the rod. This pull swings the detent lever` in the direction of arrow m (Figs. 2, 4 and A 8), and disengages its outer section 30 from the contact-bridge carrier, whereupon the v closing position by an inward movement of the push piece, the latter having been forced outwardly, when the circuit was broken.

The detent-lever section 30 has an oblique face 30b on which the finger 38c bears, when moving to engage the notch 30a. The entire detent lever and the thermostat rod 23 are adapted to be displaced by the passage of the finger over the oblique face, the nuts 24 separating slightly from the end of the tube 22, after which the spring 32 presses the notched end of the detent lever 'into engagement with the fin er.

The length of t e expanding movement of the tube 22 depends mainly on the adjustment of the top screw 33 on the detent-leverA in effecting the described adjustment.

In a sterilizing apparatus comprising a water tank, the adjustment of the screw 33 should be such that the circuit will be broken, when the heat of the tank bottom exceeds 212 F., the boiling point of water. Injurious overheating of the tank and its contents after the water boils away may be, therefore, automatically prevented.

While I have specified a knife switch as the preferred form of circuit-closing and breaking device, I do not limit myself thereto and may use any suitable device including contact members, which are separable by a spring acting on one of said members. The spring 40 should be sufficiently strong to give the movable contact member a circuit-breaking movement, which is quick enough to obviate or minimize injury to the Contact members by sparking when they are being separated. e

In the above described embodiment of the invention the detent lever 30, which acts to release the movable switch member carrier 38, is moved by direct mechanical connections between it and the thermostat member 22, when the latter is expanded by the heat of the tank.

To guard against failure to'break the circuit when the temperature rises to the predetermined point, it is necessary to soladjust the notch 30a that a relatively slight movement of the arm 30 will release the finger 38. This renders the engagement of the notch and finger somewhat sensitive, so that they are liable to be prematurely or accidentally disengaged by shocks or jars, such as those caused by moving the apparatus from one location to another. 'Io obviate this .objection I have devised the means shown by Figs. 9, 10, 11 and 12, whereby the thermostat formed by the members 22 and 23, instead of acting entirely through mechanical connections to break the circuit, acts to close a circuit through a secondary heating unit resistance, which in turn acts on a secondary thermostat, the latter `in turn acting to release the movable member of the spring-impelled circuit-closing and breaking devlce. In this embodiment of the invention the thermostat composed of the members 22 and 23 may be called the primary thermostat. The member 23 is pivoted at 55 to the shorter arm of a lever 56 which is fulcrumed at 57 to ears 58 on a bracket 59 (Fig. 12) having ears '60 which arkscrewed or riveted to the bottom of the ta The lever 56 has at the end of its longer arm a collar 56 of insulating material bearing on the upright arm of a bell-crank lever 61, which is fulcrumed at 61a to a fixed bracket 62a attached to and insulated from the base.` The horizontal arm of the lever 61 projects under a lever 62 and is normally out of-contact therewith, as shown by Fig. 11. The lever 62 is fulcrumed at 63 to av Xed bracket 64 insulated from the base, and is pressed downward by a spring 65 against an adjustable bearing screw 66 engaged 'with the base, the lever being provided -with an insulated stud 67 bearing on said screw.

The levers 61 and 62 and brackets 62, 64, constitute parts of an electric circuit which includes a secondary heating unit 68, said current being'normally broken by the separation of the levers 61 and 62 shown by Fig. 11. The lever 56 constitutes a means for closing said circuit by moving the lever 61 into contact with\the lever v62 when the primary thermostat is expanded by heat.

The secondary heating unit is embedded in an elongated tube 70 of insulating material which contains the secondary thermo# stat hereinafter described, said tube being supported by brackets 71, 72, attached to the base. One end of said unit is connected by a wire 73 with the bracket 64 and the other end by a wire 7 4 with a contact spring,

or strip 75 which is the upper member of a pair of; spaced-apart contact springs, the lower member of which is designated by the numeral 76, said springs being insulated from each other. The sprin 76 is connected by wire 77 with the termina plug 49, which is connected by wire 7 8 with one end of the tank heating unit 16', which is supported and arranged like the unit 16 previously described. A The opposite end of the unit 16 is connected at 79 with a contact spring or strip 80- which isthe upper member of a pair of spaced-apart contact springs, the lower member of which is designated by the reference numeral 81, said springs being insulated from each other. The spring 81 is connected by'wire 82 with the terminal plug 5l, and this plug in turn is connected with the bracket 62a by wire 83.

The secondary thermostat is composed of a brass tube 22 inclosed in the tubular holder of the secondary heating unit and attached at one end to the bracket 72, and a steel'rod 23 extending through the tube and having nuts 24 bearing on the free end of the tube. p

85 represents an oscillatory carrier fulcrumed at 86 on the base, and engaged by a spring 40, which has the same function as the spring 40, in that it causes the breaking of the circuit through'the primary or tank heating unit, and the added function of causing the breaking of the circuit through the secondary heating unit. In performing these functions the spring 40 swings the carrier in the direction indicated by arrows 2, a, from the position shown by Fig. 9, and thus removes two contact bridges 88 and 89 carried by it at opposite sides of its fulcrum from positions between and in contact with the contact springs 75, 76, and 80, 81, said bridges being insulated from the carrier 85.

When the apparatus is set for operation, the spring 40 is prevented from performing fits functions by a detent lever 90 fulcrumed The shorter arm of said lever is pivoted at 92 to the rod 23 of the secondary thermostat, and the longer arm has a notch 93 engaging the reduced end of thecarrier 85. It will now be seen that when the apparatus is in the condition shown by Figs. 9, 10 and 11, the primary heating circuit is closed through the terminal plug 49, wire 78, unit 16', spring 80, bridge 89, spring 81, wire 82, and terminal plug 51, and the circuit through the secondary unit 68 is broken, because the lever 61 is normally held out of contact with the lever 62, as shown by Fig. 11, by a spring 94. (Fig. 9).

When the primary thermostat is eX- panded by the heat of the tank bottom, it swings the lever 56 in the direction indicated by arrow 1/ (Fig. 9) against the pressure of a spring 95 which normally holds said lever in the position shown by Fig. 9; This movement of the lever 56 moves the bell-crank lever 61, and causes it to make contact with the lever 62. The secondary heating unit circuit is now closed through the terminal plug 51, wire 83, bracket 62, lever 61, lever 62, bracket 64, wire 73, unit 68, wire 74, spring 75, bridge 88, spring 76, wirev 77 and terminal plug 49. The primary heating unit circuit remains closed until the secondary thermostat is sulficiently expanded by the heat developed by The last described construction avoidsany'premature or accidental circuit breaking which may occur when the apparatus is organized as first described, because at 210o the switch member carrier 38 must be held in the notch 30EL while the current is heating the element 16. At the same time the detent lever 30 must release the carrier 38 at a few degrees above 212. Now according to the second construction, the secondary thermostat may be at a temperature of approximately 200 when the 'secondary heating element is not in operation. When the secondary circuit is closed, however, the secondary thermostat will be raised to from 400o to 500 in a few seconds, so that the carrier is released by a relatively ample movement of the lever 90 due to a rise in temperature of from 300 to 400, instead of by a relatively slight movement of the detent lever 30 due to a rise lin temperature of a few degrees.

The bearing screw 66 constitutes the equivalent of the screw 33 as an adjusting means for varying the extent of movement of the primary thermostat required for the performance of its function.

Each ofthe above described embodiments of the invention includes a movable carrier having circuit-breaking and closing means and normally held by means such as the spring 40. or thev spring 40 in circuit-breaking position, arresting means such as the detent 30, or the detent 90, normally adapted to hold said carrier in circuitclosing position, and thermostatic means, which may include the .tank-heated thermostat only, and direct mechanical connections between said thermostat and the arresting means, o1' may include the tankheated `primary thermostat and the secondary thermostat, the latter constituting a member of the connections between the primary thermostat and the arresting means, and retarding the circuit-breaking action of the primary thermostat.

Having described my invention, I claim:

1. In combination, an electrical heating unit; a body heated thereby; a movable carrier having circuit-breaking and closing means in circuit with said unit, said carrier being normally held in` circuit-breaking position; arresting means normally adapted to hold said carrier in means operated by an increase of temperature of said body for making said arresting means inoperative.

2. In combination, an electrical .heating unit; a body heated thereby; a movable carrier having circuit-breaking and closing means incircuit with said unit, a spring normally holding said carrier in circuitbreaking position; arresting means normally adapted to hold said carrier in circuitclosing position; and thermostatic means operated by an increase of temperature of said body for making said arresting means inoperative.

3. In combination, an electrical heating unit; a body heated thereby; a movable carrier having circuit-breaking and closing means in circuit with said unit, said carrier `being normally held in circuit-breaking position; arresting means normally adapted to hold said carrier in circuit-closing position; thermostatic means operated by an increase of temperature of said body for making said arresting means inoperative; and adjusting means for regulating the action of the thermostatic means.

4. In combination, a primary heating circuit including an electrical heating unit; a body heated thereby; a secondary heating circuit including a thermostat-heating unit; .a movable carrier having circuit-breaking and closing members in circuit with said units, said carrier being normally held in circuit-breaking position; arresting means normally adapted to hold said carrier in circuit-closing position; a primary thermostat arranged to be heated by said body; secondary circuit-closing means actuated by said primary thermostat; a secondary thermostat arranged to be heated by the secondary heating unit; and means operated by the secondary thermostat for making said arresting means inoperative.

5. In combination, an electrical heating unit; a body heated thereby; a movable carrier having circuit-closing and breaking means in circuit with said unit, said carrier being normally held in circuit-breaking position; arresting means normally adapted to hold said carrier in circuit-closing position; a thermostat arranged to be heated by said body; and means intermediate the thermostat and the arresting means for rendering the latter inoperative when the thermostat is expanded.

6.- In combination, an electrical heating unit; a body heated thereby; a movable carrier having circuit-closing and breaking means in circuit with said unit, said carrier being normally held in circuit-breaking position; arresting means normally adapted to hold said carrier in circuit-closing position; a thermostat composed of an elongated metal tube and a metal rod passing loosely through the tube and having a shoulder at one end bearing on one end of the tube; and means intermediate the opposite end of the rod and the arresting means,

vfor rendering the latter,inoperative When the thermostat is expanded.

7 In combination, an electrical heating unit; a body heated thereby; a movable carrier having circuit-closing and breaking means in circuit with. said unit', said carrier being normally held in circuit-breaking position; a detent normally adapted to hold said carrier in circuit-closing position; a thermostat arranged to be heated by said body; and means intermediate the thermostat and detent for moving the latter to a carrier-releasing position when the thermostat is expanded.

8. In combination, an electrical heating :soA

unit; a body heated thereby; a movable carrier having circuit-closing and breaking means in circuit-with said unit, said carrier being normally held in circuit-breaking position; a detent normally adapted to hold said carrier in circuit-closing position; la thermostat arranged to be heated by said body; and means intermediate the thermostat and detent for moving the latter to a carrier-releasing position When the thermostat is expanded, said means having provi-,

l stat and detent for moving the latter to a carrier-releasing position When the thermostat is expanded, said -means including a secondary heating unit, a secondary thermostat arranged to be heated'thereby, and devices for closing the circuit through the secondary heating unit When the thermostat heated bv the body is expanded.

10. In combination, a sterilizing tank; av

casing surrounding the tank; a base supportingthe casing and tank, said base and casing forming a space below the bottom of the tank; and heat-controlling means located in said space and comprising an electrical heating unit arranged to heat the tank, a movable carrier having circuit-breaking and closing means in circuit with said unit, said carrier being normally held in circuitbreaking position, arresting means normally adapted to hold said carrier in circuit-closing position, and thermostatic means operated by an increase of temperature of said tank for making said arresting means inoperative.

11. In combination, an electrical heating unit; a body heated thereby; a movable carrier having circuit-closing and breaking means in circuit with said unit, said carrier being normally held in circuit-breaking position; a detent normally adapted to hold Said carrier in circuit-closing position; a.

thermostat arranged to be heated by said.

body;l and means intermediate the thermostat and detent for moving the latter to a carrier-releasing position when the thermostat is expande said means including a secondary heating unit` a secondary thermostat arranged to be heated thereby, and devices for closing the circuit through the secondary heating unit when the thermostat heated by the body is expanded, said means including a primary thermostat heated by the tank, a secondary heating unit energized by the action of the primary thermostat, and a secondary thermostat heated by the secondary heating unit.

12. In combination, a sterilizingtank; a

casing surrounding the tank; a base supporting the casing and tank, said base and vcasing forming a space below the bottom of the tank; a heat-controlling meansvlocated in said space and comprising an electrical heating unit arranged to heat the tank, a movable carrier having circuit-breaking and closing means in circuit with said unit, said carrier being normally held in circuit-breaking position, a detent normally adapted to arrest said carrier in circuit-closing position, a thermostat arranged to be heated by the tank, means intermediate the thermostat and detent for moving the latter to a carrier-releasing position When the thermostat is expanded, and a push piece manually movable in the base and adapted to cause the re-engagement of the carrier and detent.

In testimony whereof I have aliXed my signature.

JOHN E. HARVEY.

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