US2770698A - Thermostatic switch - Google Patents

Description

Nov. 13, 1956 H. ULANET 2,770,698

THERMOSTATIC SWITCH Filed Nov. 2, 1953 2 Sheets-Sheet l il NLE Nov. 13, 1956 H. ULANET THERMOSTATIC SWITCH 2 Sheets-Shea Filed Nov. 2, 1953 INVENTOR f/m 'r W @BM ATTORNEY United States Patent() THERMOSTATIC SWITCH Herman Ulanet, Maplewood, N. J. Application November 2, 1953, Serial No. 389,523 11 Claims. (Cl. 20G- 138) This invention relates .to thermostatic switches wherein Ithe switching mechanism is enclosed in a casing, and one of the objects of my invention is to provide a construction wherein the leads to the switch are brought into the switch casing through a novel con-struction protecting the switch against the passage of moisture along the insulated leads to the switch interior.

Another object of my invention is to provide a thermostatic switch of the type above referred to wherein means are provided for adjusting fthe setting of .the mechanism of the switch, this adjusting means including bellows adjustable from the exterior of Ithe switch casing while maintaining the hermetic seal of the casing intact. This adjusting means is such that the bellows is positively elongated or contracted, instead of relying upon the spring of the bellows material for this purpose.

A further object of the invention is to provide a thermostatic switch in which the lead wires for the switch are brought out through a boss provided upon the end of the switch casing, this boss, after the leads have been threaded therethrough, being upset to provide a strain-.relief construction, so that any flexing of the leads or pushing or pulling of the leads will not move that portion of the leads lying within the casing, thus preventing the portion of the leads within the casing from interfering with the normal movement of the current-carrying blades of the switch.

A still fur-ther object of my invention is to provide a switch of the thermostatic type in which the switch blades, which are usually of spring steel, are laminated, the spring steel being sandwiched between two layers of a good conducting material, such as copper, for example, bonded to the steel, so that the lead wires for the switch may be attached to the switch blades in the vicinity of the anchored end of the switch blades, and yet heating of the blades, when a heavy curren-t passes through them, will be avoided.

A still further object of my invention is to provide a switch of the thermostatic type in which the stranded leads from the switch blades to the exterior of the switch casing lie beside and substantially parallel to and substantially in the plane of the switch blades, so that thetmovement of the switch blades will not be interfered with by the switch leads.

A still further object of the invention is to equip the switch casing with fins, to provide a large exposed area so that there will be a rapid heat transfer to the switch, which in tire detectors, for example, is very desirable. There is, of course, the other advantage, viz., rapid cooling of the switch, where it is used as a temperature control device. It will be seen, therefore, that the switch will possess a quick temperature-sensing characteristic, thus providing a very sensitive temperature control.

In the accompanying drawings,

Fig. l is a longitudinal sectional view of one embodiment of my invention;

YFig. 2 is a similar view of another embodiment of my invention;

ice

IFig. 3 `is a similar view of yet another embodiment;

Fig. 4 is an exploded view of a portion of Fig. l; and

Fig. 5 is an isometric view in part-section of another embodiment of the invention.

Referring, rst .of all, to Figs. l and 4, wherein I have illustrated a thermostatic switch yin which 2 designates the switch casing.

Within this casing I mount the switch blades 4 and 6, along with the bimetallic thermostatic control element S, which makes or breaks the switch circuit.

The switch casing is closed at one end by head 1t), which is soldered or brazed in place. Telescoping the opposite end of the casing and brazed or soldered thereto is an extteriorly threaded mounting sleeve 14, into which is threaded a plug 1-2. This plug is shouldered, as illustrated, so that a sealing washer 16 may be clamped between it and the end of the mounting sleeve 14.

The switch leads 4are designated 20 and 22, and, as above mentioned, they are brought into the casing through a novel construction which will prevent 'the passage of moisture along the switch leads to the interior of the switch casing.

As appears from the drawings, the mount 14 is provided with a threaded orifice 24, which extends at right angles to the longitudinal axis of the switch casing, and screwed into this orice is a metal sleeve 26. This sleeve may be soldered to the mount 14, or I may employ a washer between the sleeve and the mount 14 to make sure that -no moisture can work its way along the threads of th-e sleeve 26 to the interior of the switch casing. As seen at 28, the sleeve 26 is shouldered internally, and seating upon this shoulder is `a sealing plug 30 of neoprene, for exa-mple, or other elast-ic material, which is provided with two longitudinal tangential bores 32, as seen clearly, for exam-ple, in Fig. 4, each one of these bores receiving a switch lead.

Seating upon the top of the plug 30 is a non-metallic sealing washer 34, which is provided with two tangential bores 35, matching the bore-s 32 in the plug 30 and receiving the switch leads 20 and 22.

Screwed into lthe top of the sleeve 26 is a metal plug 36, the inner end of this plug engaging the sealing washer 34. Obviously, when th-e plug is screwed down tightly, it will compress the washer 34 and the sealing plug 3l) about the insulation of the switch leads 20 and 22, thereby effectively sealing olf the leads, so that no moisture or gases may work along the same to the interior of the switch casing.

The Switch blades 4 and 6, which have already been referred to, carry contacts 38 and 40, respectively. The switch blades and the bimetallic control element S are insulated from each other by insulating pile 42, which is rigidly secured to the casing head or plug 10, above referred to, and provides an anchoring means for anchoring the switch blades and the thermostatic control element.

The leads 20 and 22 are attached to the switch blades 4 and 6 at the pile 42, as shown at 44. This point of attachment of the leads to the blades is remote from the contacts 38 and 40, and, in order that heating of the blades when carrying a load may be avoided, each blade is of laminated construction comprising steel blades 4S, sandwiched and bonded between two sheets of a lowresistance metal, such as copper for example, as shown at 46.

The switch blade 4 carries a pin 50, which is insulated with a tube of insulation 51, such as Pyrex for example. This tube extends loosely through the switch blade 6 into engagement with the thermostatic control element 8.

In a normally-closed type of switch, such as illustrated, the bimetallic control element 8 is set so as to be deilected toward the switch blades upon a temperature rise,

U so that the insulating tube 51 will be moved in a direction to separate the contacts 38 and 40. The pin 50, it will be understood, is simply a kind of mount or guide for the insulating tube 51. Instead of employing the tube 51, the pin 50 may be coated with vitreous enamel.

In a normally-open type of switch, the bimetallic control element 8 is set so as to be deflected in a direction away from the switch blades upon a temperature rise, which will permit the insulating tube 51 to move away from switch blade 4, and permit this blade to close its contact 3S upon the contact 40.

The insulating tube 51 passes freely through the switch blade 6, and, hence, no motion is ever imparted to the blade 6 by the bimetallic element S.

This construction is very simple, and, inasmuch as the insulating tube 51 insulates the pin 50, there is no danger of faulty switch operation due to current jumping the gap between the pin 50 and the hole in the switch blade 6, through which the pin passes.

Furthermore, it will be seen that the pin 50 is at all times insulated from the thermostatic element 3 by the tube 51, thus avoiding the necessity of attaching an iusulating block to the face of the thermostatic element S for this purpose.

The switch of Figs. l and 4 includes a construction for adjusting the switch or setting the switch from the exterior of the casing 2. This construction embodies a partition 52 across the casing, provided with an internally threaded boss 54, concentric with the casing.

The plug 12, previously referred to, is provided with an internal bore or recess 56, and this bore or recess receives the head of a switch-adjusting screw 58, which extends through the boss 54 and is provided at its inner cud with a block of insulation 60, which cooperates with the free end of the switch blade 6.

The free end of the switch blade 6 is bent upwardly and downwardly in the form of an inverted V, and the outer leg 62 of this inverted V is engaged by insulating block 60. Obviously, by removing the plug 12 and turning the adjusting screw 58 in one direction or another, the blade 6 may be moved relatively to the blade 4, to vary the setting of the switch and, it should be observed, without any movement being imparted to the thcrmostatic control element 8.

ln thermostatic switches of the normally-closed type, such as that illustrated in Fig. 1, there is an occasional tendency for the contacts to stick when the bimetallic thermostatic control element functions. By providing the bent end on the switch blade 6, this sticking of the contacts is avoided, upward movement of the blade 6 when the blade It is pushed upwardly by the action of the thermostatic control element 8, being prevented by the ieg 62 being in engagement with the insulating block 60.

In the embodiment of the invention illustrated in Fig. 2, 102 designates the sealed switch casing of the thermostatic switch. The casing may be evacuated or gas-filled.

@ne end of the casing is sealed by head o1 plug 110.

The switch blades are designated 104 and 106, and, as in the case f the construction illustrated in Fig. l, each blade is composed of a steel blade sandwiched between two layers of a lowresistance metal, such as copper for example.

The switch blades and the thermostatic control element 108 are insulated from each other by insulating pile 14?., secured in any suitable fashion to the head or plug 110, this pile constituting the anchor for the switch blades and the thermostatic control element.

At the end of the switch casing opposite the head 110 I provide sealing plug 112, and the switch leads 120 and 12.2, which are secured to the switch blades at the insulating pile 142, are brought through the sealing plug 112 through fused glass bushings 113.

The contacts for the switch blades 104 and 106 are designated 13S and 140, respectively.

The blade 104 carries alpin 150, which is insulated by a tube 151 of Pyrex or other insulating material, the tube and pin passing freely through switch blade 106.

The operation of the switch, so far as the bimetallic element 108 is concerned, is the same as that described in connection with Fig. 1.

The sealing plug 112 above referred to is provided with a threaded central bore for the reception of an adjusting screw 158. This screw at its inner end is provided with a central bore receiving the stem 0f adjusting plug 161, tipped with insulation at its inner end, this insulating tip engaging the outer leg 162 of the inverted V into which the free end of the switch blade 106 is bent or formed, as described in connection with Fig. 1 and as illustrated in Fig. 2.

The external threads of the adjusting screw 158 are of a coarser pitch than the threads of the stem 159.

designates a sealing bellows within the casing 102, the inner end of the bellows being welded or secured to the adjusting plug 161 in any suitable fashion, and the rear end of the bellows `being secured rigidly to the sealing plug 112 as by soldering or welding or in other suitable fashion. Accordingly, the bellows 170 will prevent rotation of the adjusting plug 161.

It will be seen, therefore, that, to adjust the setting of this switch, that is to say, to adjust the setting of the blade 106 without in any way varying the setting of the thermostatic control element 108, it is merely necessary to rotate the adjusting screw 158v in the proper direction, either right-hand or left, as the case may be, and, because the adjusting plug 161 is nonrotatable as above pointed out, the plug 161 will be moved either right or left, as the case may be, as viewed in Fig. 2; and, because the threads on the exterior of the adjusting screw 158 are of a coarser pitch than the threads on the stem 159 of the plug 161, the movement of the stem 159 and, hence, of insulating tip 160, and, hence, of contact 140 will be very slight.

This construction, as will be appreciated, permits of a very fine and delicate setting of the switch, and I might add that not only is the adjustment effective from the cas ing exteriory but while retaining the hermetic seal of the casing 102 intact.

It will be appreciated also that, in adjusting the setting of the switch, the bellows 170 is moved positively in both directions, and reliance for its movement is not placed upon the spring tension of the bellows.

In the embodiment of the invention illustrated in Fig. 3, 202 designates the switch casing, which is sealed at one end by a sealing plug 210.

The switch blades are designated 204 and 206 and are of the same construction as the blades of the two embodiments of my invention already described, while the thermostatic control element is designated 208. These three elements are insulated from each other by an insulating pile 242, secured in any suitable fashion to the sealing plug 210, this pile also constituting an anchor for the switch blades and thermostatic control element.

For purposes of illustration I have shown the switch as of the normally-closed type, it being understood, of course, that the invention is applicable to switches of the riornazllyppen type, as explained in connection with Figs.

As in the other embodiments of the invention already described, the upper blade 204 carries a pin 250, insulated with Pyrex 251.

'lhe casing 202 of this embodiment of my invention is eqtupped with ns 280, which may be integral with the casing or secured in place thereon. The purpose of the ns 280 is to create a large area exposed to ambient temperatures, so that there will be a rapid heat transfer to the switch such as is very desirable in equipment such as fire detectors, for example. Of course, this construction provides another advantage, namely, rapid cooling of the thermostat, where the switch is used as a temperature control device, so that the switch as a whole possesses quick temperature-sensing characteristics, thereby to provide a very sensitive temperature control device.

The adjusting means for varying the setting of this switch embodies a plug 212, soldered or brazed or otherwise sealed in place in the end of the casing opposite the head 210. This plug is provided with a central bore 282 for receiving the head of switch-adjusting screw 258. The screw 258 is provided through its inner end with an internally threaded bore 288, receiving the externally threaded stem 259 of an adjusting member 261, tipped with insulation 260, which engages the free end of the switch blade 206.

The adjusting screw 258 is provided with an annular flange 290, and welded or otherwise rigidly secured to the inner face of the sealing head or plug 212 is a sleeve 292, which surrounds the annular ange 290 as well as the adjusting screw 258.

Surrounding the adjusting screw 258 and the adjusting plug 261 is a bellows 270, the inner end of which is rigidly attached to the face of the member 261, and the outer end of which is clamped between the sleeve 292 and an annular ange 294, provided for this purpose on the inner face of the head or plug 212.

This construction, it will be quite obvious, provides a hermetic seal for the switch casing and at the same time permits of adjustment of the switching mechanism from the switch exterior while maintaining the hermetic seal of the switch mechanism intact.

Simply by rotating the adjusting screw 258, the stem 259 of the adjusting member 261 will be drawn to the right or left, as the case may be, thereby to vary the setting of the blade 206 without in any way affecting the setting of the thermostatic control element 208. Here again, as was the case in connection with the embodiment of my invention illustrated in Fig. 2, the movement of the bellows 270 in both directions is positive, and no reliance is placed upon the tension of the bellows for this purpose.

In the embodiment of my invention illustrated in Fig. 5, 302 designates a switch casing, which may be closed at one end with a head similar to the head 210 of Fig. 3, for example. The opposite end of the casing 302 is closed by a head 400, which is provided on its outer face with an integral boss 402, the head 400 and the boss 402 being bored for the reception of the leads 420 and 422 of the switch.

Within the casing 302 is the switch mechanism, which is similar to that already described in connection with Figs. 1, 2, and 3, 304 designating one switch blade and 306 the other, these blades, together with the thermostatic control element, being insulated from each other by insulating pile 342, which constitutes an anchor for these three elements.

As will appear from the drawings, the leads 420 and 422, which pass through the bores in the boss 402 and head 400 to the interior of the casing 302, extend parallel to and are in substantially the same plane as the switch blades 304 and 306. The ends of the boss 402 are upset, as shown at 424 and 426, to distort the bores in the boss, thereby clamping the leads 420 and 422 against movement. This provides a strain-relief construction, so that any flexing of the leads 420 and 422 or pushing or pulling of the leads will not disturb that portion of the leads lying within the casing 302, thereby preventing this portion of the leads from interfering with the normal movement of the switch blades 304 and 306.

In this embodiment of the invention I have shown an adjusting screw 358, which is threaded through the boss 402 and head 400 and carries at its inner end a block of insulation 360, adapted to engage the end of the switch blade 306 in the same manner as described in connection with Fig. 3, for instance, to enable the switch to be adjusted or set from the exterior of the casing 302.

It will be understood that changes may be made in the details of construction and arrangement of parts hereinabove described within the purview of my invention.

What I claim is:

1. In a thermostatic switch, the combination of a sealed enclosure; a pair of contact arms within said enclosure, each arm comprising at least three metal strips sandwiched and bonded together, one of the metal strips being of spring metal, and one other strip being of low electrical resistance; means for anchoring said arms at one end; a contact carried by each arm adjacent its other end; and switch leads for said arms attached to a lowresistance strip of the arms at a point remote from said contacts.

2. In a thermostatic switch, the combination of a casing; a pair of contact-carrying arms within said casing; an insulating pile at one end of said arms, anchoring the same to said casing; switch leads attached to said arms in the vicinity of said pile; a switch-adjusting screw at one end of the said casing and accessible from the casing exterior, said screw being concentric with said casing, and said lead wires extending through the same end of the casing as the adjusting screw.

3. In a thermostatic switch, the combination of a sealed enclosure; a pair of spring-metal contact arms, one of which is movable relatively to the other, within said enclosure; means for anchoring said arms at one end; a contact carried by each arm adjacent the other end; a thermostatic element for controlling the movement of said movable contact arm, the other of said contact arms being adjustable relatively to the first arm; and adjusting means for the adjustable arm, said adjusting means comprising a longitudinally movable member extending into the enclosure and operable from the enclosure exterior, the free end of said adjustable contact arm being bent into an inverted V, and the end of said longitudinally movable adjusting member engaging one leg of said inverted V for adjusting the same and to prevent said contacts from sticking together.

4. In a thermostatic switch, the combination of a sealed enclosure; switching mechanism, including a thermosensitive element, sealed within said enclosure; and tins on the exterior of said enclosure for increasing the area exposed to the surrounding atmosphere, to provide for a rapid heat transfer to the thermo-sensitive element.

5. A thermostatic switch comprising, in combination, a sealed enclosure; switching mechanism therein comprising a plurality of contact arms and a thermo-sensitive element controlling the movement of one of said arms; a plug or head sealing one end of the said enclosure; an adjusting screw threaded through said head; an adjusting member threaded into the inner end of said adjusting screw with a shorter pitch than the pitch of the threads on the adjusting screw exterior, the inner end of said adjusting member contacting one of said switch arms to adjust the setting of the same; and a bellows surrounding the stems of the adjusting screw and adjusting member, one end of said bellows being sealed to the inner face of the said enclosure head, the other being sealed to the adjusting member, whereby the latter will be held against rotation but given micrometer longitudinal movement upon rotation of the adjusting screw.

6. A thermostatic switch comprising, in combination, a sealed enclosure; switching mechanism therein, including contact arms and a thermo-sensitive element controlling the movement of one of said arms; a head for the enclosure; a longitudinally movable adjusting member operable from the enclosure exterior for adjusting the setting of one of the contact arms; and a bellows within the enclosure, said bellows surrounding said adjusting member and having one end rigidly secured to the adjusting member and its other end secured to the inner face of said enclosure head, to provide for positive mechanical contraction and expansion of the bellows upon longitudinal movement of the adjusting member.

77. A thermostatic switch comprising, in combination, a hermetically sealed enclosure.; switching mechanism therein, including contact arms and a thermosensitive element controlling the movement of one of said arms; a longitudinally movable adjusting member carried by said enclosure and concentric therewith; and a sealing bellows within the enclosure, said bellows surrounding the adjusting member and sealed at one end' thereto, the opposite end of the bellows being sealed to the casing, to provide for mechanical contraction and expansion of the. bellows and for actuation of the adjusting member from the enclosure exterior while the hermetic seal of the enclosure remains intact.

8. In a thermostatic sWitch,`the combination of a sealed enclosure; a pair of contact arms Within said e11- closure, each arm comprising a central strip of spring metal sandwiched between and bonded to two strips of a metal of low electrical resistance; means for anchoring said arms at one end; a contact carried by each arm adjacent its other end; and switch leads for said arms attached to the low-resistance face of the arms at a point remote from said contacts.

9. A contact arm for thermostatic switches, said arm being composed of three superimposed metal layers bonded to each other, at least one of said layers being composed of a metal 4of high electrical conductivity.

10, In a thermostatic switch, the combination of an enclosure; and switching mechanism therein, comprising a plurality of contact arms and a thermo-sensitive element, andl an insulated pin, secured to one contact arm and passingy loosely through another into cooperative relation to the thermo-sensitive element, whereby movement of the pin-carrying contact arm is under control of the thermo-sensitive element.

11. In a thermostatic switch, the combination of an enclosure; and switching, mechanism therein, comprising a plurality of contact arms and a thermo-sensitive element, a pin secured to one contact arm, and an insulating tube or sleeve telescoping` said pin, said tube passing loosely through another of the contact arms into cooperative relation to the thermo-sensitive element, whereby movement of the pin-carrying contact arm is controlled by the thermo-sensitive element.

References Cited in the file of this patent UNITED STATES PATENTS 2,102,407 Dann Dec. 14, 1937 2,140,147 Vroom Dec. 13, 1938 2,262,025 Marcy Nov. 11, 1941 2,316,612 Newell Apr. 13, 1943 2,321,338 Ulanet June 8, 1943 2,332,518 Koci Oct, 26, 1943 2,500,760 Lee Mar. 14, 1950 2,518,595 Bletz Aug. l5, 1950 2,667,553 -Moorhead et al Ian. 26, 1954

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