US3790075A - Thermostat assembly - Google Patents

Abstract

A ceiling air terminal serving as part of an air conditioning system for a building and adapted to discharge conditioned air into an area to be treated. The terminal is provided with a bleed-type thermostat employing a bimetallic element movable in response to temperature variations in the air passing over the element from the area served by the ceiling terminal. The bimetallic element is adjustably supported for movement relative to the housing of the thermostat. The adjustable support includes a calibration member formed of a thermoplastic material. The calibration member journals a control rod. The position of the control rod is selectively varied to regulate the operation of the terminal to obtain a desired temperature in the area. A resilient spring member cooperates with the calibration member so the member is maintained in intimate contact with the control rod, thereby preventing the rod from self rotating.

Description

United States Patent [191 Rifkin et a1.

[ THERMOSTAT ASSEMBLY [75] Inventors: Ernest Rifkin, Dewitt, N.Y.;

Richard C. Dreibelbis, Fair Lawn, NJ.

[73] Assignce: Carrier Corporation, Syracuse, N.Y. [22] Filed: July 12, 1972 g [21] App]. No.: 270,914

[51] Int. Cl. F24f 3/06 [58] Field of Search 308/26; 236/49, 87; 74/531 Primary Examiner-William Wayner Assistant Examiner--,Willi am E. Tapolcai, Jr. Attorney, A gent, or F irm- Barry E. Deutsch 51 Feb. 5, 1974 ABSIRACT A ceiling air tenninal serving as part of an air conditioning system for a building and adapted to discharge conditioned air into an area to be treated. The terminal is provided with a bleed-type thermostat employing a bimetallic element movable in response to temperature variations in the air passing over the element from the area served by the ceiling terminal. The bimetallic element is adjustably supported for movement relative to the housing of the thermostat. The adjustable support includes a calibration member formed of athermoplastic material. The calibration member journals a control rod. The position of the control rod is selectively varied to regulate the operation of the terminal to obtain a desired temperature in the area. A resilient spring member cooperates with the calibration member so the member is maintained in intimate contact with the control rod, thereby preventing the rod from self rotating. v

5 Claims, 6 Drawing Figures PATENTEUFEB 51914 3790.075

saw 3 OF 3 FIG. 6

FIG.4 FIG.5

THERMOST AT ASSEMBLY BACKGROUND OF THE INVENTION This invention relates to ceiling air terminals of the type employed in air conditioning systems, and more particularly to an improved thermostat assembly employed in combination with the ceiling air terminals for obtaining desired temperature conditions in an area being served by such terminal. Still more particularly,

this invention relates to an improved control rod assembly for use in air conditioning systems controls.

The use of thermoplastics, such as acetals, instead of metals, has become quite prevalent in recent years, due to the relative inexpensive cost of such thermoplastics. The utilization of such plastics has permitted manufacturers to decrease the cost of their products without creating a concomitant decrease in performance. Thermoplastics have been found to be particularly suitable for many applications formerly requiring metals such as zinc, brass, and aluminum.

Of the various types of thermoplastics used throughout industry, the acetal plastics have proven to be particularly effective in applications formerly utilizing metals. There are two types of acetal thermoplastics commonly in use. One is a homopolymer essentially formed of a straight formal dehyde chain. The other acetal thermoplastic is a copolymer, essentially formed of a trioxane chain, sold and manufactured by the Celanese Corporation under the trademark Celcon."

Thermoplastics have been used quite extensively in the manufacture of thermostats of the type disclosed in US. Pat. No. 3,595,475, issued July 27, 1971, Daniel H. Morton, inventor. The thermostat disclosed in the aforecited patent has proven to be highly satisfactory when employed to regulate the operation of ceiling air conditioning terminals of the type utilizing a portion of the conditioned air supplied thereto as a control medium, to avoid the necessity of a separate control system.

As is readily apparent to those skilled in the air conditioning arts, thermostats are designed to provide extremely accurate performance within a relatively narrow operating range. However, the thermostats are often exposed to temperature conditions which greatly exceed their designed operating range.

addition, thermoplastic parts also have a tendency to cold flow as a function of time.

One of the parts, which has been formed of the thermoplastic material and which has thence, at times, become permanently deformed, is a calibration member or block, which is adjustably connected to the housing of the thermostat for relative movement therebetween. The calibration member journals a control rod, which the occupant of the area being served by the air terminal may selectively adjust so a desired temperature condition is obtained in the area. The calibration member is designed to provide a force to counteract any forces tending to cause the control rod to self rotate.

However, if the calibration member has become permanently deformed, the member may no longer provide the requisite counteracting force to prevent the rod from self rotating.

During the typical operation of a .ceiling air terminal, the occupant of the area establishes a desired setpoint by moving the control rod to a position corresponding to a desired temperature which he wishes in the area. Due to insufficient frictional engagement between the rod and the calibration member, caused by the members permanent deformation, the control rod may move from its desired location without the occupant being aware of such movement. Thus, after a period of time, when the temperature of the area being served by the terminal has not achieved the desired level, the occupant may not be aware of the actual reason. therefore. The occupant may think a severe malfunction exists, resulting in the occupant calling for service from a qualified Serviceman. The occupant may thence incur a relatively expensive service charge when, in effect, no service call is required.

SUMMARY OF THE INVENTION It is therefore an object of this invention to prevent self rotation of a control rod of a room thermostat.

It is a further object of this invention to improve selfcontained controls of the type' employing a bimetallicelement to sense the temperature of air in an area so a desired temperature condition may be obtained therein by regulating the supply of conditioned air thereinto.

A still further object of this invention is to improve the strength of thermoplastic members so regardless of their becoming deformed, they will still perform their intended function. v

It is yet another object of this invention to provide an air conditioning control, including thermoplastic parts, that is extremely accurate in its designed operating range, and will maintain its performance capability when exposed to extreme conditions.

These and other objects of our invention are obtained by providing a thermostat including a bimetallic element movable in response to ambient temperature. The bimetallic element is mounted on an adjustable support member disposed in the housing of the thermostat.

The adjustable support member includes a calibration member adjustably secured to the housing for movement relative thereto. The calibration member is formed of a thermoplastic material. The calibration member journals a control rod, which may be selectively positioned by the occupant of the area, to obtain a desired temperaturecondition in the area. A resilient spring member is connected to the calibration member so the portion thereof journaling the control rod is maintained in intimate contact therewith so the control rod is prevented from-self rotating.

BRIEF DESCRIPTION OF THE DRAWINGS I FIG. 1 is a schematic'illustration of a portion of an air conditioning system illustrating an air terminal employ- FIG. 4 is a perspective .view of a detailof the thermostat;

FIG. 5 is a sectional view taken along the lines 5-5 of FIG. 4; and

FIG. 6 is a somewhat schematic sectional representation of the prior art.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, there is illustrated a central air conditioning apparatus of the type employed in large multistory buildings including a system of duct work, a filter 5, a cooling coil 7, spray means 9, a cooling coil 11, a heating coil 13, and a fan for heating, cooling, humidifying and filtering the air as desired to provide conditioned air for passage to the areas for use in the building equipped with an air conditioning system incorporating the apparatus. 7 A supply air duct 17 is illustrative of the plurality of ducts provided to supply conditioned air to ceiling air terminals disposed in areas throughout the building. The ceiling terminal includes a primary chamber 19 lined with a sound absorbing material 21 such as a glass-fiber blanket. The primary chamber is ordinarily open at both ends for connecting a series of terminals end to end to provide a complete air discharge system. Suitable end pieces, not shown, are utilized to cap the end terminals in the series. An air supply distribution plate 23 having a plurality of collared openings 25 therein is provided to evenly distribute the supply of air from primary chamber 19 into a distribution chamber 27 which is defined by the top and side walls of distribution plate 23.

The bottom of distribution chamber 27 includes aligned cut-off plates 29 which are provided with a curved surface 30 for engagement by bladders 31 and 33 of an air flow control unit to form a damper. The curved surfaces smooth the flow of air through the damper to minimize the pressure drop therethrough and to minimize noise generation within the terminal. The surface 30 is covered with felt 32 to further minimize noise. By varying the inflation of the bladders, the area of the openings between the bladders and the cutoff plates may be varied to regulate the quantity of air discharged into the area being conditioned.

Bladders 31 and 33 are adhesively mounted on a central partition comprised of opposed, generally convex plates 35. The plates have a V-shaped recess therein so the bladders arecompletely recessed within the plates when deflated. This provides 'a large area between active walls 34 of the bladders and the cut-off plates for maximum air flow therebetween. Further, the recessed bladder provides a smooth surface along plate 35 to minimize air turbulence.

The damper mechanism is disposed a substantial distance upstream from the discharge openings. in the terminal to provide sufficient space therebetween to absorb any noise generated by the damper mechanism. For maximum sound absorption, downwardly extending walls 41 which form narrow, vertical air discharge passages in conjunction with plates 35 are lined with a sound absorbing material such as glass-fiber blankets 43. Outlet members 45 having outwardly flared lower portions 47 thereon are affixed by welding to walls 41.

The ceiling terminal disclosed hereinabove may be utilized to provide a variety of modes of terminal operation. If it is desired to maintain a constant discharge of air from the terminal,.a pressure responsive control may be employed to inflate the bladders in response to supply air pressure to reduce the area between the bladders and cut-off plates as duct pressure increases and to increase the area therebetween as duct pressure decreases.

If it is desired to control the terminal to provide a constant room temperature under varying cooling loads, the bladder inflation may be controlled by a thermostat responsive to room temperature to provide an increased quantity of air flow from the terminal as the cooling load increases and a decreased quantity of air flow from the terminal as the cooling load decreases.

A cross-sectional view of a thermostat which has proven to be highly satisfactory in regulating the operation of the ceiling air terminal disclosed hereinabove is shown in FIG. 2. Thermostat 50 includes a housing 57 having an opening formed in the lower portion thereof for passage of room air therethrough into the interior of the housing. A U-shaped bimetallic element 59 is mounted within housing 57 on an adjustment block 61. In order to assure maximum contact of room air with the bimetallic element and to provide a bimetallic element large enough to actuate the movable members of the thermostat, bimetallic element 59 is preferably provided with a plurality of perforations 62 extending throughout its axial length in both legs 60 thereof. By preferably forming the perforations in legs 60 of the bimetallic element, an element having a width slightly less than the interior of housing 57 may be employed. The perforations in element 59 allow maximum contact between room air and element 59 for rapid and accurate response of the thermostat to variations in room temperature.

The adjustment block which mounts bimetallic element 59 is slidably mounted within housing 57 for vertical movement relative thereto. Springs 69 are provided to bias block 61 against temperature adjustment cams 71 formed on adjustment shaft or rod 75. Shaft or rod 75 is journaled in a calibration member or block 77 (See FIGS. 3 and 4) which is secured to housing 57 by calibration screw 79. The position of the calibration block may be adjusted relative to the housing by the calibration screw.

Resilient spring means 81 is suitably joined to calibration block 77 for reasons. to be more fully explained hereinafter. For a more detailed explanation of the manner in which the thermostat is calibrated by adjustment of screw 79, reference may be had to the aforecited US. Pat. No. 3,595,475. A rotational force may be applied manually or otherwise to shaft 75 via adjustment lever' 85 which is affixed to the end thereof.

A lever 87 pivotable about a shaft 89, journaled within the side walls of housing 57, is provided to convert the vertical movement of the bimetallic element caused by temperature variations into horizontal movement. A bleed plate 91 having an opening 93 therein is provided to override bleed port 95 formed within housing 57. To obtain an extremely compact thermostat a very short bimetallic element is utilized. Lever 87 is therefore provided with arms 86 and 88 of unequal lengths measured from pivot 89. The short arm contacts bimetallic element 59 while the long arm contacts bleed plate 91. This provides a relatively large horizontal movement of the bleed plate to compensate for the relatively small vertical movement resulting from the use of a short bimetallic element. To obtain the necessary force against arm 86, bimetallic element 59 has a greater thickness than bimetallic elements normally employed in a thermostat of this type.

A leaf spring 97 suitably affixed to housing 57, by means such as fastener 98, is provided to bias plate 91 toward lever 87. An adjustment screw 99 in housing 57 is provided to adjust the biasing force exerted by spring 97 against plate 91.

Bleed port 95 communicates with an air passage 101 within housing 57. An opening 103 within housing 57, communicating with passage 101, is provided for receiving a suitable pressure regulator to provide regulated control pressure to thermostat bleed port 95. For a description of a suitable pressure regulator, reference may be had to US. Pat. No. 3,434,409, granted Mar. 25, 1969 in the name of Daniel A. Fragnito Air is bled from the regulator through bleed port 95 to provide variable air pressureat bladders 31 in response to temperature variations in the area being treated. To minimize installation costs, the thermostat is preferably factory calibrated in the manner disclosed in the heretofore cited US. Pat. No. 3,595,475.

To further reduce costs, many of the parts of the thermostat are formed from a thermoplastic material such as an acetal plastic of the type heretofore mentioned. In particular, calibration block 77 is preferably formed from such a thermoplastic material.

Thermoplastic parts have proven highly satisfactory in maintaining their design integrity when subjected to a relatively narrow range of operating conditions. However, the parts have not always maintained their integrity when subjected to conditions substantially in excess of their designed operating range.

For example, it has been found, during the .shipping of the thermostats from the factory to their place of installation, some of the thermostats have been subjected to excessively high temperatures. When the thermostats are so subjected to such high temperatures, some of the thermoplastic parts may become permanently deformed by creeping or cold flowing. If calibration block 77 has become so deformed as a result of cold flowing, the portion thereof journaling control rod 75 may no longer maintain sufficient contact therewith.

Heretofore, it has been the practice to use a set screw 79 and pressure pad 80 in cooperation with block 77 to provide a requisite force on rod 75. In using the set screw and pad, calibration block 77 has been mildly deformed in the manner illustrated in FIG. 6. The mild deformation creates a restoring force in block 77. The restoring force of block 77 counteracts a force provided by the action of springs 69 attempting to move block 61 to its original location, after the block had been moved therefrom as a result of rod 75 being rotated. The force produced by springs 69 created moments which tended to cause rod 75 to self rotate. The restoring force of block 77 offsets the moments,

' thereby maintaining rod 75 in the position established by the occupant.

However, when block 77 has become permanently deformed as a result of cold flowing, the restoring force is eliminated. Thus the moments produced by the forces of springs 69 caused rod 75 to self rotate, thereby changing the setpointor desired temperature level in the area. To obviate the problem, set screw 79 and pad 80 have been eliminated. It no longer is necessary to mildly deform block 77 to obtain a restoring force. In lieu of the set screw and pad, a resilient spring member or clamp 81 has been provided to supply the necessary force to maintain calibration block 77 and control rod in intimate contact to prevent the control rod from self rotating. Spring member 81 is formed from a resilient material, such as spring steel, which has sufficient strength to maintain'the desired contact between rod 75 and block 77 regardless of any permanent deformation of the parts. In addition, spring member 81 should be sufficiently yieldable to compensate for any expansion of calibration block 77.

As is clearly illustrated in FIGS. 3-5, spring member 81' includes preformed side arms 83 and 83', an upstanding wall portion 84 having the preformed side arms integrally connected thereto, and a horizontally planar portion 82, formed integrally with wall portion 84 and having an upstanding portion 82' extending therefrom. f

The preformed side arm portions 83 and 83 are adapted to cooperate with wedge-shaped portions 76 and 76' of calibration block 77. As is illustrated in FIG. 5, the side arm portions are sprung outwardly by movement over the wedge-shaped portions. The ends of side arm members 83 and 83 are adapted to abut flange portion 78 of the calibration block to thereby maintain the top portion of the spring and the calibration block in intimate contact.

As is illustrated in FIG. 3, upstanding wall portion 82 of the resilient spring member 81 is adapted to abut a portion of the face of the calibration block, which has a slot preformed therein to provide suitable interference between the wall 82' and the front face of the calibration block. In assembling the control rod assembly including control rod 75, block 77 and spring member 81, the spring clamp is brought into engagement with the block. Upstanding wall portion 82' of spring 81 is placed in contact'with the front face of block 77 by being aligned with the slot provided therefore. Preformed side arm members 83 and 83' are placed in engaging relationship with wedge-shaped portions 76 and. 76' of block 77 so the ends of the preformed wall portions abut flange 78. The control rod is then inserted in the opening in the block 77 provided therefore. The surfaces of the block defining the opening yield a sufficient amount so the shaft may be readily inserted therein. The material forming spring 81 is sufficiently yieldable so as to accommodate the insertion of shaft 75 into the opening. Side-arm members 83 and 83' are provided to maintain the spring clamp 81 in place relative to block 77, yet permit the assembly of the clamp about the block without stressing the spring member beyond its yieldpoint. Spring member 81 cooperates .with block 77 to maintain intimate contact between rod 75 and block 77. Spring member 81 provides a squeezing force to maintain the desired frictional contact be tween the foregoing members of the control rod assembly.

If the thermostat is exposed to temperatures of a substantially excessive magnitude beyond the designed operating range in which the thermostat is to normally function, as for example during shipping, the calibration block may become permanently deformed as a result of cold flowing. However, resilient spring 81 maintains control rod 75 and calibration block 77 in intimate contact regardless of the magnitude of the deformation. Thus, when an occupant of an area adjusts the position of control rod 75 by moving lever 85, the lever and control rod will not self rotate from such preselected position. The squeezeforce provided by spring clamp 81 is of a sufficient magnitude to prevent any self rotation from occurring.

While we have described and illustrated a preferred embodiment of our invention, it should be understood that the invention is not limited thereto, but may be otherwise embodied within the scope of the following claims.

We claim:

1. In combination with a room thermostat for regulating the operation of a terminal supplying conditioned air into an area so a desired temperature level can be obtained, said thermostat including a bimetallic element for sensing the temperature of the air in the area and being movable in response thereto, the improvement which comprises:'

A. adjustable support means, including a calibration member formed of thermoplastic material, for supporting at least a portion of said bimetallic'element;

B. control means journaled by said calibration member and being selectively adjustable to position said bimetallic element so a desired temperature condition is obtained in said area; and

C. resilient spring means connected to said calibration member for providing a squeezing force to maintain intimate contact between the portion of said calibration member journaling said control means and said control means, said contact being maintained regardless of any deformation of said calibration member from its original configuration, to prevent said control means from self rotating re]- ative to said calibration member.

2. The combination in accordance with claim. 1 wherein said spring means includes an upstanding wall portion having side-arm portions extending integrally therefrom.

3. A control assembly for use in air conditioning system components wherein said components regulate the operation of terminal units employed in said system to discharge conditioned air into an area comprising:

A. a control rod, the position thereof being selectively adjustable to a position corresponding to the desired temperature condition in said area;

B. means journaling said control rod within the housing of said component; and

C. resilient spring means to maintain intimate contact between said control rod and said journaling means to prevent said control rod from self rotating.

4. A control assembly in accordance with claim 3 wherein said spring means includes an upstanding wall portion having side-arm portions extending integrally therefrom.

5. The combination in accordance with claim 2 wherein said calibration member includes a portion having opposed wedge-shaped surfaces, and a flange normal to said wedge-shaped surfaces, said side arm portions of said spring means moving radially outward as a result of contacting said wedge-shaped surfaces the outer ends of each of said side arm portions being in intimate contact with said flange.

Claims (5)

1. In combination with a room thermostat for regulating the operation of a terminal supplying conditioned air into an area so a desired temperature level can be obtained, said thermostat including a bimetallic element for sensing the temperature of the air in the area and being movable in response thereto, the improvement which comprises: A. adjustable support means, including a calibration member formed of thermoplastic material, for supporting at least a portion of said bimetallic element; B. control means journaled by said calibration member and being selectively adjustable to position said bimetallic element so a desired temperature condition is obtained in said area; and C. resilient spring means connected to said calibration member for providing a squeezing force to maintain intimate contact between the portion of said calibration member journaling said control means and said control means, said contact being maintained regardless of any deformation of said calibration member from its original configuration, to prevent said control means from self rotating relative to said calibration member.

2. The combination in accordance with claim 1 wherein said spring means includes an upstanding wall portion having side-arm portions extending integrally therefrom.

3. A control assembly for use in air conditioning system components wherein said components regulate the operation of terminal units employed in said system to discharge conditioned air into an area comprising: A. a control rod, the position thereof being selectively adjustable to a position corresponding to the desired temperature condition in said area; B. means journaling said control rod within the housing of said component; and C. resilient spring means to maIntain intimate contact between said control rod and said journaling means to prevent said control rod from self rotating.

4. A control assembly in accordance with claim 3 wherein said spring means includes an upstanding wall portion having side-arm portions extending integrally therefrom.

5. The combination in accordance with claim 2 wherein said calibration member includes a portion having opposed wedge-shaped surfaces, and a flange normal to said wedge-shaped surfaces, said side arm portions of said spring means moving radially outward as a result of contacting said wedge-shaped surfaces the outer ends of each of said side arm portions being in intimate contact with said flange.

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