US 2901577 A
Description (OCR text may contain errors)
Aug. 25, 1959 R. E. DRUMMOND Er-AL COVER OPERATED THERMOSTAT Filed March, 20, 1958 United States Patent COVER OPERATED THERMOSTAT Ralph E. Drummond, Bell, and John W. Wright, Long Beach, Calif., assignors to Robertshaw-Fulton Controls Company, Richmond, Va., a corporation of Delaware Application March 20, 1958, Serial No. 722,810
4 Claims. (Cl. 200'138) This invention relates to control devices and more particularly to a bimetal actuated thermostat.
It is an object of this invention to control the ambient temperature by manual manipulation of the cover of a control device.
It is another object of this invention to provide a simple adjustment or calibration means for a control device.
It is another object of this invention to fixedly mount a temperature indicating device regardless of movement of a temperature control device.
It is a further object of this invention to provide means to insure disengagement of a pair of contacts when a cover member is rotated to the oil? position.
It is still a further object of this invention to make the parts of the control device easily accessible in the event service is required.
These and other objects will become apparent from the following detailed description taken in connection with the accompanying drawings wherein:
Fig. 1 is a front view of the control device embodying this invention;
Fig. 2 is a cross-sectional view of the device shown in Fig. 1; and
Fig. 3 is a sectional view taken along line III-III of Fig. 2.
Referring more particularly to the drawings, a control device, indicated generally at 10, includes a circular base member 12 which is adapted to be secured in a vertical position by screws (not shown) driven into a wall or suitable mounting surface through a pair of mounting apertures 14 provided in the base. The base 12 is provided with a centrally disposed boss 16 having a square opening 18 therethrough. A center post or shaft 20 is provided with a non-circular, preferably square-shaped reduced portion which is split to form legs 22. The legs 22 are slidably received in the opening 18 and due to their shape, rotation of shaft 20 is prevented.
Rotatably mounted on the upper portion of boss 16 is a generally elongated member which forms a first lever 24. Lever 24 is held in place by a U-shaped clip 26 which is secured to the base 12 by suitable fastening means 28. A flange 30 extends from one end of the lever 24 and has one end of a bimetal strip 32 attached thereto by rivets 34. The bimetal strip 32 has a sub- :stantially circular configuration with the high expansion :element situated on the inner side thereof.
The other end of the bimetal is bent inwardly so as to form a portion of a radius of the circular configuration and has a contact 36 of a pair of contacts 36-, 38 resiliently connected thereto. More particularly, a substantially U-shaped armature 40 has one leg fastened to a bimetal 32 and a leg of a substantially U-shaped spring clip 42 is attached to the other leg of the armature by a rivet 44. The U-shaped armature 40 and the U-shaped spring clip 42 are positioned in mating relation and the contact 36 is secured to the other leg of the spring clip 42 and extends through an aperture 46 formed in the bimetal 32 and the armature 40. The contact 36 is 2,901,577 Patented Aug. 25, 1959 adapted to be moved into and out of engagement with contact 38 by bimetal 32 in response to changes in ambient temperature.
The contact 38 comprises a screw which is threadedly received by the outwardly extending leg of an angular member 48 which is secured to the base 12 by rivets 50. A permanent magnet 52 is also attached to the outwardly extending leg of angular member 48 and is adapted to encircle the contact 38. It is apparent that the permanent magnet 52 attracts the armature 40 to close the contacts 36, 38 and that the screw contact 38 may be rotated to adjust the holding force thereof.
Means is provided to move contact 36 relative to contact 38 to vary the temperature at which the contacts will open or close. This means includes a second lever 54 which is pivotally mounted on a pin 56. The pin 56 is attached to the base 12 and extends outwardly therefrom. The lever 54 is of a V-shaped configuration and has one of its legs adjustably connected to the first lever 24. This connection comprises a screw 58 which is threadedly mounted on a flange 60 of a lever 24 and a coil spring 62 which has one end fastened to the base 12 and the other end fastened to the lever 24. The spring 62 urges the lever 24 in a clockwise direction about shaft 20 to cause engagement of the screw 58 with the lever 54.
The other leg of lever 54 is adapted to ride on a cam surface 64 formed on the inner portion of a cover 66 which is adapted to protect the parts of the device. The cover 66 is of generally cup-shaped configuration and has a centrally disposed annular flange portion 68 which is rotatably positioned on the shaft 20. Resilient means 69, composed of two separate springs, is disposed around shaft 20 between the clip 26 and flange 68 to bias the flange 68 against a shoulder 70 on the shaft 20. The cover 66 is also provided with a downwardly extending peripheral flange 72 which forms a shield for the parts while still permitting free flow of air thereto.
Mounted on the shaft 20 within the cup-shaped recess of cover 66 is a circular dial face 74 having an appropriate scale 76 thereon. A pointer 78 is fixedly mounted on the cover 66. The cover 66 is adapted to be manually rotated to move the pointer 78 relative to the scale 76 to select the temperature condition at which the contacts 36, 38 are to close to operate appropriate air conditioning or other controlled equipment (not shown).
When the cover 66 is rotated in a clockwise direction to move the pointer 78 to a higher setting on dial face 74, lever 54 rides down the cam surface 64 and thereby rotates in a counter-clockwise direction about pin 56. A pair of stop pins 80 are mounted on the base 12 and are adapted to engage a pair of projections 82 formed on the inner portion of cover 66 to limit the range of rotation of the cover 66.
Upon counterclockwise rotation of lever 54, the coil spring 62 maintains the screw 58 in contact with lever 54 thereby causing clockwise rotation of lever 24 about shaft 20. This clockwise rotation of lever 24 moves bimetal 32 and contact 36 attached thereto toward and into engagement with the base mounted contact 38. It is now apparent that a higher ambient temperature will be required to actuate the bimetal 32 to move contact 36 out of engagement with contact 38. Thus, the conditioning equipment will operate to increase the ambient tempereature until the higher temperature is reached and contact 36 disengages contact 38. Conversely, when the cover 66 is rotated in a counterclockwise direction, a lower ambient temperature will be required to open contacts 36, 38 and terminate operation of the conditioning equipment.
To calibrate the device, the screw 58 is merely rotated with respect to its mounting flange 60, This causes be. closed,atany, desired position, of, the cover mem.-
A positive Ofi means is provided to insuredisen gagement-of;the contacts 36,-. 38 -when. the..cover 66 is rotated .to its, extreme,counterclockwise position.-, More particularly, an arm.79 projects from lever, 24 andis adaptedto -engagetheU-shaped armature 40,-to restrain thecontact 36 from-engagemenpwith contact38 when the.,co ver -is,rotate;d to this position.
The device thusfarrdescribed is, adapted to ,control; the ambient temperatureabout a;,sett ing of pointer 78;.
means To this end a bimetal-coil 8,4 -is; attachedutoua, reduced portion 8,6,,of;sha ft and is provided-with anv indicator 88 attached toanendthereof, The. indicatorv 88; is adapted to be movedby the. bimetal coilv84.. rela-. tive to the scale, 76 .in-response .to the ambicnttemperaa ture to inclicatethensame. A. decorative-cover. 90 is. connected to .shaftlllbyfastening means 92: A. transparent. plastic crystal 94.;is1positionedin the cupportion ofcover 66 to shieldtheparts therein while permitting. external viewing of'thedial face 74.. A. series of ports 96:are-provided;in. the cup portionofcover66 to permit the: free flow ofair-to the bimetal-coil 84. These portsare shieldedby the peripheral flange72-on cover 66. i
In operation, current is supplied from an external source (not shown) and passes through a conductor 98 to a terminal 100. which is mounted on the base 12. A lead 102- connects the terminal 10010 the lever 24. Current thenflows from lever 24 through bimetal 32- to contact 36; Whencontact 36 is in engagement with contact 38, current will flow from contact 38- through support member 48 anda bus bar 104 which connects support-member 48 with a terminal 106 mounted-onbase 12. Current then continues from terminal106, out through conductor 108 to the conditioning equipment Assume an ambient temperature of 75 F. is desired. Cover 66 is merely rotated clockwise to set pointer 78-at' 75 F. on scale 76. This rotation of cover 66 causes lever 54-, to rotate counterclockwise lever 2 4 to.
rotate clockwise, and-movement of contact 36 into engagement with contact 38 to operate conditioningequipment in a manner hereinbeforedeseribed. When the arnbient temperature reaches .75 F., the bimetal willbe dia; metrically expanded with the inner high expanding surface tending to straighten the circular configuration. The contact 36 will then be moved'upwardly and outwardly at approximately a 45 angle of contacts 38 to break the circuit and ceaseoperation of the conditioning equipment.
Conversely, the contracting of the bimetal 32 due to cooling will close the contacts 36, 38. When the cover 66 is rotated to its extreme clockwise or Off position, the projection or arm 79 on lever 24 will engage the armature 40 to prevent contacts 36, 38 from closing.
In the event that service of the control device is required, the legs 22' of shaft 20 are merely extracted from theopening 18in base 12 and the shaft 20 and the partsattached thereto are readily accessible to the Serviceman.
While only a single embodiment of this invention has been shown and described herein, it is apparent that many changes. may be made in the construction and operation without departing from the scope of this invention as. defined in the appended claims.
1. A thermostatic control device comprising a base member, first contact means carried by said base member, temperature setting means movably mounted on said base member and including a substantially circular cover member spaced from said base member for ambient air flow between said cover memberand said base member, a bimetallic element secured to said temperature setting means and .being, disposed adjacent the space. between said base, member and vsaid cover member, and second contactmeans carried by said bimetallicelement and movable therewith, relative to said first contact means in response to movement of said temperature setting means and in response to temperature variations of the air, said bimetallic elementhaving a substantially circular configuration to provide a maximum area exposed to the air flowing between said base member and said cover member.
2, Athermostatic control device, the combination comprising a base member, first contact means carried by said. base e ber. ver an at l?. m unt d Q a base member, a. substantially circular cover member movably mounted on said base member and beingsp laced therefrom for ambient.air flow betweensaid cover member n said b m mber a d ovetmember. n i g said lever means and being operable to ,cause rotational v men e o a. mper re es o s ve me attached to said lever meansand-substantially encircling the same, said temperature .responsive element; being positionedadjacent the spacebetween said cover member and said base member to provide maximuin air exposure, and-second contact means carried bysaid temperature responsiveelement and movable therewith relative to said first contact means in responseto movement of said lever member and in response. to variations in air temperature, v I
3. In a device for controlling operation of conditioning equipment, the combination comprisingabase having a shaft extending outwardly therefrom, a substantially circular cover member rotatably mounted on said shaft and'being spaced from said base for ambient air flow therebetween, cam means disposed in said cover member,
a first lever pivotally mounted at its medial portion Onv said shaft betweensaid base and said cover member, a second'lever-pivotally mounted on said base and operatively connected to said first lever and said cam means to cause movement of said first lever upon rotationiof said cover member, a temperature sensitivebimetal hav} ing one end-attached'to an end of-said first lever, said bimetal substantially encircling the first lever and being positioned adjacent the space between said base member andsaid-cover member to provide a maximum area of air-exposed bimetal in minimumspace, and'a pair of contacts one of which is selcuredto another end of said bimetal and the other being carriedby said base, said one contact being positioned relative to said other contact by movement of said cover member whereby said one contact-willengage said-other contact to cause operation of-the conditioning equipment at a predetermined air temperature.
4. The control device ofclaim 3 wherein the operative connection between said first and; second levers com prises a screw threadedly mounted on said first lever, resilient. means urging said screw into engagement with said second lever, said screw being adjustable to vary the position of-said-first lever relative to said second-lever to calibrate the control device.
References Citedin the file ofthis patent UNITED STATES. PATENTS 2,681,965 Kebbon June 22, 1954 2,729,719 Kronrniller Jan. 3, 1956 2,734,113- Hilgert Feb. 7, 1956 w ll.