US2075873A - Thermostat - Google Patents

Description

"I A. A. STRAND 2,075,873

THERMOSTAT 5 Sheets-Sheet 1 Filed Oct. 20, 1951 A. A. STRAND A ril 6, 1937.

THERMOS TAT Filed Oct. 20, 1951 3 Sheets-Sheet 2 INVENTOR ATTORNEY-3 BY his Patented Apr. 6, 1937' rnaamosmr August A. Strand, Maiden, Mass., assignor to G and N Engineering Company, Boston, Mass., a corporation of Massachusetts Application October 20, 1931, Serial No. 569,916

15 Claims. (01. 1753l5) The invention relates to controlling temperature, and more particularly to thermostats.

The objects of the invention include the provision of a relatively inexpensive, dependable, highly efficient and sensitive device of the type above indicated. Various further and more specific objects, features and advantages will clearly appear from the detailed description given below, taken in connection with the accompanying drawings which form a part of this specification and illustrate, merely by way of example, embodiments of the invention. a

In the drawings, Fig. 1 represents a front elevation of the thermostat with the cover removed;

Fig. 2- is a section taken on the line 2-2 of Fig. 1;

Fig. 3 is a detail taken on the line 33 of Fig. 1, illustrating the construction of a part of the device;

Fig. 4 represents a section on the line 44 of Fig. 1; Fig. 5 is a section on the line 5-5 of Fig. 4;

Fig. 6 is a section taken on the line 6-6 of Fig. 1;

Fig. 7 is a section on the line 1-1 of Fig. 1;

Fig. 8 is a section on the line 8-8 of Fig. 2;

Fig. 9 is a detail showing the manner in which the thermostat may be mounted on a wall;

Fig. 10 represents diagrammatically the wiring diagram of the thermostat;

Fig. 11 is a detail illustrating a modified form of the contacts.

Figs. 1 2 and 13 illustrate, on an enlarged scale, the manner of sealing the temperature-responsive units.

In the following description and in the claims, various details will be identified by specific names for convenience, but they are intended to be as generic in their application as the art will permit.

Like reference characters denote like parts in the several figures of the drawings.

In the drawings accompanying and forming part of this specification, certain specific disclosures ofthe invention are made for purposes of explanation, but it will be understood that the details may be modified in various respects with out departure from the broad aspect of the invention.

Referring rfiiw to the drawings, the thermostat comprises a metal base 44 having a removable cover 45 secured thereto in any desired manner. The removable cover 45 may have the usual, ordinary thermometer 46 secured thereto.

Secured to the base 44 is a bracket 41, a lower insulating plate 48 and an upper insulating plate I5.

Secured to the bracket 41 is a bellows 20 constructed to expand upon a rise in temperature and to contract upon a drop in temperature. The bellows shown comprises a plurality of sections 49 of a similar construction, each section having a socket 5I secured on one side and a plug 50 secured to the other. These sections are screwed together with the plugs fitting in the sockets and, if desired, washers 52 may be interposed between the plugs and sockets, as indicated.

Each section 49 is made up of two circular discs I49 and I50 overlapped and soldered together around their periphery. These discs may be made of good temperature conducting material such as copper and, as shown, are corrugated annularly with the corrugations increasing in size (becoming flatter) from the circumference to the center. These discs I49 and I50 are suitably soldered to the plugs and sockets, as shown.

Each section 49 may be filled with a suitable temperature responsive medium such as ether. The ether is introduced preferably through an opening in the plug which is sealed by a ball of lead shot placed in the opening after the section is filled. The soft metal of the shot is expanded in the opening and the metal of the plug 50 is spun over as shown to make a gas tight joint, Fig. 12 representing the relation of the parts prior to the spinning operation and Fig. 13

representing the relation of the parts after the spinning operation. The spinning tool is denoted It will be noted that the ball250 is pressed against the tapered surface 25I on the plug and that the reduced upper end 252 is spun down on the ball 250. A double seal is thereby provided at these points. I

The top section of bellows 20 is secured to the bracket 41 by a fitting I5I threaded on the plug 5|. The lower section of bellows 29 has a rod 54 soldered in the socket 50, the rod 54 passing through an opening I54 in the bracket 41. A coil spring 56 may be interposed between the lower section 49 and the bracket.

The rod 54 has an oiIset portion 55 (Fig. 5) which straddles the hollow shaft 59. To form a rack-and-pinion connection between the rod 54 and the shaft 59 whereby small longitudinal movement of the rod 54 due to temperature changes causes a large rotary movement in the shaft 59, a flexible round wire, or fiat band 51, as shown, is wrapped around the shaft 59 with a single turn, as shown, or with a plurality of turns, and is held taut by a coil spring 58, the band 51 and spring 58 being secured to the bent ends of the ofiset 55.

It will be noted that the ends of the ofiset 55 5 are so located with respect to the hollow shaft 59 that the adjacent parts of the flat bend 51 on the shaft do not touch each other (Fig. 2).

Also supported by the bracket 41 is an insulating drum or disc 68 mounted upon a bushing 81 which passes through a bearing inthe depending part H! of the bracket. Fixedly secured to the bushing 8'! is a gear member 84 having teeth 85 which mesh an adjusting member 88 which projects out through an opening inthe cover 45 so that the discs 84 and 88 may be adjusted for the desired temperature. If desired, the gear member 84 may be calibrated in degrees of temperature.

The insulating disc 88 has a pair of spiral contacts 24 and 25 partially imbedded therein, as illustrated best in Figs. 1, 2 and 18. Between these contacts is a ridge 28 of insulating material which is normally held abovethe surface of the contacts, as shown in Fig. 3 by a spring 18, to provide a 25 yieldable resistance to the roller 28 on the rotary arm 21. A limiting member I18 secured to the disc 88 limits the retracting movement of ridge 28 to a position flush with the outer surfaces of the spiral contacts 24 and 25 to prevent all pos- 30 sibility of the roller 28 bridging the contacts 24 and 25.

The insulating disc 88 also has a pair of circular collector rings 22 and 23 in the periphery thereof, ring 22 being connected to the contact 25 and ring 23 being connected to the contact 24.

Journalled within the bushing 81 and a depending part 88 of the bracket 41 is a rod 2| upon which is mounted the hollow shaft 53. The latter has its ends flanged inwardly 'so that it 40 contacts the rod 2| at these points only to cut down friction. Mounted upon the shaft 58 is insulating ring 62 which carries a collector ring 29 to which the rigid arm 21 is secured. The arm 27 carries a grooved roller 28 which is rotatable thereon and movable axially thereon and which runs upon the spiral contacts 24 and 25. Spring members 83 and 89 hold the roller 28 in contact with the spiral contacts 24 and 25. A brush 38 (Figs. 4 and 8) is secured to the insulating base 48 and contacts the collector ring 28.

Also mounted upon the insulating base 48 is a pair of electro-magnets 3| and 32 having the reduced ends of their cores 12 riveted over on the opposite side of the insulating base (Fig. '7). A

brass holder 13 has openings through which the cores 12 pass and assists in holding the windings of the electro-magnets 3| and 32 against the insulating base 48, a screw I48 holding the brass holder to the base (Fig. 8).

The armature 34 is pivoted to the holder 13 by pivot 33 and has secured thereto a pivot 88 (Fig. 7) which connects with a connecting rod 8| which in turn is pivoted to an arm 82 mounted on shait83 which is journalled in a fitting 84 secured to the insulating base 48. The shaft 83 has an arm 85 which connects with a link 88 which is pivoted to the center of an insulating bar 38 (Fig. 6).

The insulating bar 38 is pivoted toa fitting I88 which is secured to the, insulating base and carries a circular contact 38 which engages stationary contacts 48 secured to the insulating base.

For giving a snap action to the switch 33, 48

a rod 81 is pivoted to theinsulating member 38 and loosely passes through a fulcrum member 88 and through an opening in fitting 88 which is secured to an insulating base 48. A spring I88 operating between a shoulder upon the rod 81 and the fulcrum piece 88 insures a quick snap of the movable contact 38 for opening and closing.

Secured to the bracket 41 is an insulating panel 14 (Figs. 1 and 7). To this panel are pivoted contacts 36 and 31 which in turn are pivotally connected toan insulating link 35 which is secured to a pivot 15, in turn secured to the armature 34. The contacts or brushes 38 and 31 have curved ends for alternately engaging and disengaging the collector rings 22 and 23, as indicated in Figs. 2 and 7.

It will be noted that the three binding posts, indicated by 42 (Figs. 6 and 2), are mounted upon the insulating base 48 and connect with the magnets 3| and 32 and with the brush 38, and contacts 48, as indicated in Fig. 10, which illustrates diagrammatically the thermostat and the electrical wiring thereof.

If desired, the binding posts 42 may be connected by wires 18 to the three prongs of the connector, illustrated by I42 in Fig. 9, which may be mounted upon the upper insulating base 15, as illustrated in Figs. 2 and 9, and the other part of the connector 43 may form a wall receptacle (Fig. 9) by which the entire thermostat may be mounted.

The contacts on the wall receptacle may lead to the source of power and the load, as illustrated in Fig. 10. The load may be a distant electromagnet for operating the controls of a heating or cooling system or, in the case of electrical heating, the load may be the heater units themselves.

If desired, the connectors 43 and I42 may be omitted and the connecting wires to the power source and load may lead to these devices directly in which case the thermostat may be supported from the wall or other support in any conventional manner.

The operation of the thermostat is as follows: Referring to Fig. 10 and assuming the room to drop below its desired temperature, the bellows 28 will contract and the arm 21 will move, say, to the left. As the roller 28 engages the spring pressed insulating piece 28, it will depress it to a position flush with the outer edges of the spiral contacts 24 and 25 with the result that the spring pressure on the insulating piece 28 will cause the roller 28 to make a quick make with the contact 24. This completes the circuit through the collector ring 23, brush 38, which is in engagement therewith, operating magnet 32 to close the contacts 38, 48 and apply energy to the load. This provides more heat, raising the temperature of the room.

It will be seen that the operation of the magnet 32 breaks the contact at 38 and makes the contact at 31 so that the circuit through spiral contact 25 will be in readiness when the circuit is completed by operation of the roller 28 back to the position shown.

As the temperature of the room increases, the bellows 28 will expand and move the arm 21 back across the spring pressed insulating piece 28 to the position shown in Fig. 18, which will establish a circuit through magnet 3| to open the contacts 39, 48 and thereby turn off the-heat. This cycle of events will continue, to keep the temperature substantially constant;

It will be appreciated that the current through the electro-magnets 3| and 32 lasts only for an instant and therefore there is no chance for them to become hot and interfere with the operation of the thermostat. Furthermore, the roller 28 never breaks a circuit, all breaking being done by the brushes 36 and 31. The roller 28 merely operates to make a circuit. Thus, no arcing, which may interfere with radio, can take place since the make of contact 28 is always quick due to the snap action of spring pressed insulating piece 26, and the break of the brushes in 36 and 31 is always quick due to the quick action of the arm 38 which operates these members.

To adjust the thermostat to a different operating temperature it is only necessary to move the gear 66 to move the disc 64 to set the desired is temperature. Thus, a wide range of operating conditions is provided for. The thermostat may be used to keep a room, say, at '70 degrees and then, if desired, by merely making the adjustment stated above, the thermostat may be set to keep a temperature of, say, degrees. The long length of spiral of the contacts 24 and 25 allows a great range of movement for the roller 28. The thermostat is suitable for regulating temperature both in buildings and in refrigerators.

Another advantage of the present construction is that it may be used directly on household voltages in the neighborhood of 110 volts and that it is not necessary to provide dry cells or local sources of current of reduced voltage.

The construction of the multiple unit bellows provides a large temperature control surface and the corrugated construction of each unit assists inproviding a bellows which is extremely sensitive to minute changes in (temperature. Furthermore, the connection between the bellows and the thermostat arm is such as to greatly multiply the movement of the bellows to make the arm move a substantial distance when the temperature varies a fraction of a degree.

The provision of the hollow shaft 59 supported on the rod 2| at its ends only, the spacing of adjacent parts of the convolutions of the band 51 on the shaft 59 and the loose sliding fit of the bellows rod 54 through the opening in the bracket, all assist in cutting down friction in the operating parts to a minimum and thereby greatly increasing the sensitivity of the instrument.

It will be understood that in some cases the switch 39, 40 may be placed away fromthe thermostat, near the apparatus it is desired to control, or both the electromagnets 3|, 32 switch 39, 40 and brushes 36, 31 may be located away from the thermostat.

The construction of the bellows is such that a substantially uniform rate of linear expansion of the bellows per degree change in temperature is obtained.

If desired, instead of using the snap contact arrangement for the roller 28 above described, the arrangement shown in Fig. 11 may be used. In this figure the spiral contacts 2| and 25 are merely spaced apart by a fixed piece of insulation .200 and an additional roller 26! is placed upon the arm 21 riding on the face of the insulating disc in a circular path. A spring pressed piece 203 may. be placed in the path opposite the section of insulation 260. Thus, the operation of the spring pressed piece 203 against the roller 20! on the rigid arm 21 operates to snap the contact roller 28 from one spiral segment to the other. The piece 203 may be constructed and spring actuated in a manner similar to the piece 26 except that it need not be made of insulation.

while certain novel features of the invention have been disclosed and are pointed out in the annexed claims, it'will be understood that various omissions, substitutions and changes may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is:

1. In a thermostat, a base, a temperature responsive bellows secured rigidly to said base at one end and having a rod at its other end, a shaft rotatably mounted on said base, a contact on said shaft, a flexible member wrapped around said shaft and connected to said rod whereby longitudinal movement of said bellows imparts rotation to said shaft, and a contact adapted to be engaged by said first contact.

2. In a thermostat, a temperature responsive device adapted to expand and contract longitudinally, a rotary element, connections between said temperature responsive device and said rotary element whereby the peripheral movement of said rotary element is substantially equal to the linear movement of said device, means cooperating with said rotary element to control an electrical circuit, and means comprising a spiral 7 contact for controlling the path of said rotary element.

3. In a thermostat, a temperature responsive device adapted to expand and contract longitudinally, a rotary contact member, connections between said temperature responsive device and said rotary contact member for transmitting movement therebetween, a second contact member cooperating with said rotary contact member to control an electrical circuit, and means for adjusting one of said contact members for desired temperature conditions.

4. In a thermostat, a temperature responsive device adapted to expand and contract, a rotary element, a flexible member wrapped around said rotary element and secured to said device to transmit motion from said device to said rotary element, and heat controlling devices operated by said rotary element.

5. In a thermostat, a base, a temperature responsive bellows comprising a plurality of disclike units arranged in line, said bellows being secured rigidly to said base at one end and having a rod at its other end, an insulating disc rotatably mounted on said base, a plurality of spiral contacts on said insulating disc and a spring pressed insulating piece therebetween, an electric circuit controlled by said contacts, a plurality of collector rings on the periphery of said disc and connected to said contacts, a shaft rotatably mounted on said base, a rigid arm projecting from said shaft, a grooved roller rotatable and slidable on said arm riding on said spiral contacts, a strand wrapped around said shaft and connected to said rod whereby longitudinal movement of said bellows imparts rotation to said arm, an electromagnet in said circuit operated by engagement of said roller and said contacts and brushes engaged with said collector rings and operated by said electromagnet.

6. In a thermostat, a rotary support member, spiral contacts on said support member, an insulating member between said contacts, a rotary arm member, a contact element slidably mounted on said arm.member and engaging said contacts, and temperature responsive means for imparting movement to one of said members and means for adjusting the other member to set a desired temperature.

7. In a thermostat, a support having contacts thereon, a contact member engaging said support and means whereby said contact member is roiii 40 brushes adapted to engage and disengage with tated relative to said support through an extent substantially greater than 360 degrees over a non-reentrant path to engage said contacts.

8. In combination, a support, contacts on said support, an insulating member between said contacts, means for yieldably urging said insulating member outwardly, a contact member and means for imparting relative movement to said contacts and contact member to cause said insulating member to shift engagement of said contact member from one contact to the other with a snap movement.

Q/l'n a thermostat, a drum having a plurality of peripheral collector rings, brushes adapted to engage and disengage with said collector rings,

an electric circuit, an electromagnet in said circuit for operating said brushes to make contact between one brush and one ring and simultaneously to break contact between the other brush and the other ring, and thermostat contacting devices in said circuit responsive to changes in temperature for operating said electromagnet, said electromagnet being controlled by said brushes and contacting devices, parts of said contacting devices being mounted on said drum.

10. In a thermostat, a support, spiral contacts on said support, an opening in said support between said contacts, an insulating member slidably mounted in said opening, a spring for yieldably urging said insulating member outwardly, limiting means to prevent said insulating member from retracting below the surface of said contacts, a rotary arm, a grooved roller rotatably and slidably mounted on said arm and engaging said contacts, and temperature responsive means for imparting relative rotation between saidarm and support.

11. In a thermostat, a plurality of terminals, an electric' circuit connected to said terminals,

said terminals, an electromagnet device in said circuit cooperating with said brushes and terminals to make contact between one brush and one terminal and simultaneously to break contact be- 45 tween the other brush and the other terminal,

50 said contacting devices and thermostat contacting devices responsive to changes in temperature for closing said circuit abruptly to operate said electromagnet devices, said electromagnet devices being controlled by terminals.

12. In a thermostat, a pair of electromagnets,

and by said brushes andan armature operated thereby, a drum, 8. pair of conducting rings mounted thereon, a pair of brushes engageable with said conducting elements, connections between said brushes and said armature for alternately engaging a brush with a ring, a pair of contacts mounted on said drum and connected to said rings, respectively, a contact member adapted to alternately engage said contacts and operable by change in temperature, means whereby said electromagnets are selectively operated by the make 01' said contact member and said contacts and to cause the current in that circuit to be broken at said brushes.

13. In a thermostat, a pair of electromagnets, an armature operated thereby, a drum having a pair of collector rings, a. pair of brushes engageable with said collector rings, connections between said brushes and said armature for alternately engaging one brush with one ring and disengaging the other brush from the other ring, a pair of contacts mounted on said drum and connected to said rings, respectively, a" contact member adapted to alternately engage said contacts and operable by change in temperature, connections from said brushes to the windings of said electromagnets and to said contact member whereby said electromagnets are selectively operated by the make of said contact member and one 01' said contacts and such operation immediately causes the current in that circuit to be broken at said brushes, 2. switch controlled by said electromagnets, and means for adjusting said drum for the desired temperature.

14. In a thermostat, a contacting element, two contact members, two electrical circuits, means to cause said element to engage either one of said members abruptly to complete one of said circuits, and means in said circuits responsive to the current therein to break whichever said circuit has been completed.

15. A thermostat comprising a temperature responsive device having one end anchored and the other end free to move with expansion and contraction of said device, a shaft, 9. flexible strand wrapped around said shaft, a support connected to the free end of said device and having two terminals on opposite sides of said shaft, means for yieldably holding said strand under tension between said terminals, and a temperature control device operated by said shaft.

AUGUST A. STRAND.

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