US2225841A - Temperature and humidity control - Google Patents

Description

Dec. 24, 1940. c. A. OTTO TEMPERATURE AND HUMIDITY CONTROL Filed Oct. 23, 1939' MAIN AIR;

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UNITED STATES PATENT OFFICE 2,225,841 TEMPERATURE AND HUMIDITY CONTROL Carl A, dtto, Milwaukee, Wis-., assignor to Johnson Service Company, Milwaukee, Wis, a corporation of Wisconsin Application October 23, 1939, Serial No. 300,879

'1 Claim. (Cl. 236-79) ment was changed from high temperature for day to a low temperature for night, by changing the pressure in the supply line. Where the instrument is of .the leak-port type, the change of supply pressure does affect the characteristic of the instrument independently of the adjustment of the thermostatic, unit, or the selection between two differently adjusted thermostatic units, both these schemes being known in the prior art. It was, however, possible to make a compensatory adjustment where all the-instrument did was to select between two definite control points. When the instrument was of the progressive acting type and the readjustment was progressive, the change in supply pressure became a disturbing factor for whichno compensation could be made, because the error introduced by the change in supply pressure was progressive over the entire range of readjustment.

Consequently, in this type of instrument, it has I been universal practice, so far as applicant is aware, to use two lines, one of which supplies air at uniform pressure to the instrument, the other line being confined to operation of the readjusting motor and subject to pressure changes which affect the readjustment. In cases where the control line is long, this scheme has undesirable aspects.

The purpose of the present invention is to elimsure which aifect the control are all above fifteen (15) pounds. 7

50 A simple-embodiment of the invention will now be described in connection with the accompanying drawing which is a diagram of a single instrument arranged for remote readjustment according to the invention.

55 The casting l is the base plate of the instrulever l5.

ment. Mounted in and projecting froin this base plateis an expansible element 2 of the thermostatic couple. This might be a brass tube closed at its outer end. The rod 3 is a relatively inexpansible elementof the thermostatic couple and it enters into thrust relation with the closed end of the tube, 2. It may be of the alloy known by the trade name Invar. Having a negligible coeflicient of thermal expansion, it transmits the changes of length of the tube 2 to the thrust 10- head 4, which is guided in the base I and loaded by a coil compression spring 5.

Pivoted at 6 on the base I is a lever l which carries a leak-port 8. Pivoted on the lever 1 ats is a lever n, against which the thrust head 4 15 in a direction to close the leak-port. Motion of the lever II is transmitted at varying ratios to the lever 15 by means of a thrust boss I! which is adjustable in the direction of the length of the The pivot 6 is above the axis of the thrust member 4 so that angular movements of the lever I modify the adjustment effected by thescrew l2. The position of the lever l is determined by cam l8 against which a thrust screw is reacts under the stress imposed by a tension spring 2| connected between the base I and the lever l.

The cam I8 is carried on the end of one arm 22 of a bell crank lever, the other arm 23 overlying the adjusting bellows 24 mounted on base I. The bellows 24 is simply a metallic diaphragm cell. The pivot for the bell crank lever is shown at 25 and the arm 23 directly engages the front of the bellows 24. To provide for adjustable resistance of the bell crank to the force exerted by 5 the bellows, a spring 26 is connected to a secondary lever 21 which is pivoted at 28 on the arm 23 of the bell crank and which is adjustable by means of a thrust screw 29.

An inspection of the figure will show that the face of the cam I8 is slightly oblique to the path of the arm 22 and the degree of obliquity is adjustable. This result is secured by pivoting the cam is at iii, and clamping the arm 32 which is integral with the cam It in various adjusted relations by means of the screw 33. The screw works in an arcuate slot formed in a plate 34 rigidly mounted on the arm 22 and engages plate 34'. The range of motion afforded-to the bell crank lever 22, 23, is determined by an adjustable stop screw 35. Y

The connection to the leak-port 8 is made by means of a flexible tube 36 which is coiled as indicated to permitmotion of the lever I.

No novelty is here claimed for the-remote readjustable thermostat so far described? A main air line 31 supplies air under a pressure of,.say, thirty pounds (which is about twice that customarily used in pneumatic thermostat sys- ,tems) to the adjustable pressure reducing valve 38 whose constructioni-s clearly shown and for- -which no novelty is here claimed. Thisvalve is connected to the air supply line 39 which leads to the remote readjustable thermostat already described and communicatesfreely with bellows 24. The sole function of the valve 38,. and this function may be performed by any equivalent mechanism, is to vary progressively, according to the adjustment of the valve 33, the pressure in the line 39 between supply pressure (assumed to bethirty pounds) and some pressure slightly higher than the supply pressure tothe remote readjustable thermostat (say twenty pounds).

The remote readjustable thermostat is assumed to be designed for a supply pressure of say fifteen pounds, which is usual in the art. With the as- .sumed values, the tension of the spring 28 would be such that the bell'crank Hand 23 would be moved through its entire range of adjustment in response to a pressure change between twentyand thirty pounds.

A branch of the line 39 leads to a pressure reducing valve 4| and this delivers through the connection 42 to the flow restricting fitting 43 which is the supply connection of the thermostat. The

fiow restricting fitting 43 is connected to the tube .36, which leads to the leak-port 8 and is also connected to the branch line 44 which leads to the motor 45. The motor 45 is typical of any. pressure motor capable of responding to variations of pressure in the line 44.

It will-be understood that according to standard practice, the capacity of the fitting 43 is adjusted just the bell crank lever 22, 23 by the variations of pressure produced in the bellows 24.

- It follows from what has been said above, that with-a single line 39,.it is possible to readjust the thermostat from ,a remote point by changing the pressure of air supplied to the thermostat. The

only effect of the changed pressure is the changed 1 thermostat and thus stabilizes its operating char-' acteristics.

The invention is particularly useful in those,

cases where the supply line 39 islong. it affords.

progressive readjustment with a single supply line and secures this result without substantial expense because the only additional apparatus re .quired is the pressure reducing valve.

The invention is available wherever it is possible'to use a supply pressure substantially above theimmediate pressure of supply to the inlet connection of the thermostat.

It will be' understood that the drawing is dianection 44 and the motor 45, but the use of pneumatio relays in 'this relation is so well known as to require no description. Such use can notinvolve patentable novelty and is mentioned here simply'to indicate that the invention does not exclude the use of such a relay.

What is claimed is: v

The combination of a control .device of the pneumatic typehaving an inlet connection to which. pressure fluid must be supplied at a definite pressure to establish precise operating characteristics' of-the device, said device including a leak-port fed, by said inlet connection, a leakport controlling valve, .a. responsive element ar ranged to operate theleak-port controlling valve,

andadiusting means for progressively modifying v the effect of said element on said valve; fluid pressuremotor meansconnected to actuate said adjusting means and adapted to. operate through its. entire range in response to'change's of fluid pressure through a range above said definite pressure; pressure fluid supplying ,means adjusting fed by said supplying means and arranged to a feed said inlet connection and maintainithereon said definite pressure irrespectiveof changes in supply pressure.

CARL A. OTTO.

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