US2561437A

US2561437A - Temperature sensitive device for ice bank controllers

Info

Publication number: US2561437A
Application number: US57859A
Authority: US
Inventors: Clifton A Cobb
Original assignee: Missouri Automatic Control Corp
Current assignee: Missouri Automatic Control Corp
Priority date: 1948-11-02
Filing date: 1948-11-02
Publication date: 1951-07-24
Anticipated expiration: 1968-07-24

Description

July 24, 1951 c. A. coBB 2,561,437

TEMPERATURE SENSITIVE DEVICE FOR ICE RANK CONTROLLERS Filed Nov. 2, 1948 Patented July 24, 1951 UNITED STATES PATENT OFFICE TEMPERATURE SENSITIVE DEVICE FOR ron BANK ooNrnoLLEas I Clifton A. Gobbi University City, Mo., assigner to Missouri Automatic Control Corporation, St. Louis, Mo., a corporation of Missouri Application November 2, 194s, serial No. 57,859

6 Claims. l

This invention relates to control devices which are actuated by the change in volume of a liquid as it is frozen or melted. More particularly, it relates to a control device of this character adapted to control the operation of a refrigeration com-.-` pressor so as to closely control the ice formation or thickness of the ice bank which builds up on or adjacent to the refrigerant coils in a cold water type cooler.

`The advantage of employing the considerable volume change of a liquid as it freezes or melts to actuate a refrigeration controller is well known. Also devices have been proposed which employ this principle of operation and which incorporate therewith a non-freezing transmission lud for transmitting movement of the expansible receptable or feeler bulb containing the freezing liquid to a remote point,`there to cause the expansion of a second expansible element and the actuation of an associated control member.

An object of this invention is to provide a generally new and improved control device of this character which is unusually sensitive and dependable, which is simple and inexpensive to produce, and which will not be damaged by eX- DOsure to temperatures considerably below the freezing point of water.

A further object is to provide a control device of this character having an improved all metal-l lic feeler bulb adapted to measure the ice thickness, which comprises a pair of liquid containing chambers separated by a flexible metallic wall wherein many suitable combinations of freezing and non-freezing liquids may be used without danger of absorption by the separating wall or its dissolution, or of dilution of either of the liquids by osmosis.

A further object is the provision of a control device of this character having a feeler bulb comprising a hollow elongated metal outer tube of circular cross section and an inner elongated relatively thin walled metal tube of non-circular cross section, which inner tube contains a nonfreezing liquid and has communication with a remote expansible element, and which outer tube contains a volume of pure water surrounding the inner tube.

A further object is the provision of a control device of this character having a feeler bulb comprising a pair of chambers separated by a rela-` tively thin flexible metal wall in which one of the chambers contains pure water and the other contains a non-freezing liquid, the chamber containing the non-freezing liquid being in communication with a remote expansible element, the

chamber containing the non-freezing liquid also having a rigid backing wall opposite the flexible separating walll which is shaped to permit uniform deflection of any part of the wall to a point below the elastic limit of the material of which the flexible wall is constructed.

A further Object is the provision of a feeler bulb for use in a control device as above comprising an elongated hollow metal outer tube of circular cross section, and an inner elongated andrelatively thin metal inner tube of non-:circular cross section,` which inner tube contains sealed therein a volume of pure water and which outer tube contains a volume of non-freezing liquidsurrounding the inner tube and has communication with a remote expansible element.

Other objects and advantages will appear from the following complete description when read in connection with the accompanying drawing.

In the drawing,

Fig. v1 is a schematic view showing a cooler in part together with a motor driven compressor and refrigerant coils and a control device constructed in accordance with the present invention associated therewith so as to control the starting and stepping of the compressor so as to maintain a predetermined thickness of ice formation .on the wall of the cooler.

Fig. :2 is ,an enlarged view of the control device shown use in Fig. 1 in which parts have been shown in section to more clearly illustrate.

Fig; 3 is an enlarged transverse sectional View taken through the feeler bulb of the control de- ViGe Shown Fig. 2 and is taken on line `fie-3 of 2.

Fig, fi illustrates a second form ,of feeler bulb which may be used in lieu of the one shown in Fig. 3.

Fig. 5 is an enlarged transverse sectional view taken on line 5,-5 of the bulb shown in Fig. 4.

Fig. 6 1S a part longitudinal section taken .on line 6-7-6 of Fis. 4.

The reference numeral ID indicates a cooler shown in Dart having a wall I I in which are ar.- ransed refrigerant evaporator coils I2. The cooler substantially flledwith water as indicated at 1 3 and the refrigerant coils connect with a compressor indicated at I4 which is drivenfby .an electric motor I5. A circuit for the motor I5 comprising the leads I6 and Il connected to a source of power is provided and a control device generally indicated at I8 is interposed in the circuit to effect an off and on control of the operation of the compressor. The control I 3 includes a feeler bulb generally indicated at It which'is positioned at a predetermined distance from the wall thereby to control the thickness of the ice bank.

The bulb |9 as shown in Figs. 2 and 3 comprises an outer metal tube 2U in which is fitted a relatively thin walled metal tube 2| having flat sides 22 and rounded edges 23. The outer tube 20 in cross section has a circular exterior wall 24 and a passage 25 therethrough which is generally elliptical in cross section and which receives the attened inner tube 2|. has inserted therein a ller bar 26 having concave surfaces 21 opposite the flat sides 22 of the inner tube. Otherwise the iiller 26 nicely nts the interior of tube 2|.

The inner metal tuber At its ends the outer tube 26 isfprovided with concentric circular counterbores at 28 and 29 to receive the circular

end closing plugs

36 and 3|. The end closing plug 3| is shown as being an integral' part of the filler bar 26. For economical construction the circular plug 3| may be attached to the ller bar 26 by welding or solder- 1,

ing. The end closing plugs 36 and 3| maybe rigidly held in place by soldering or welding. The shape of the passage 25 in cross section is such that the rounded edges 23 of the inner tube are contiguous therewith for a full 180 as indi-V cated.

There is a longitudinal passage 32 in the filler bar 26 extending from one end to approximately the center of its length and a transverse passage 33 intersecting the passage 32 providing communication between the passage 32 and the opposite spaces which lie between the concave sides 21 of the ller bar and the at sides 22 of the inner tube 2|. The passage 32 extends through the end closing plug 3| and receives at its outer end a capillary tube 34. The other end of the capillary tube 34 communicates with the.

interior of an expansible element 35 comprising a rigid outer metal cup member 36 and an inner iiexible metal cup member 31. The outer and

inner cup members

36 and 31 are attached alongY their side walls as by continuous welding Vas indicated at 38. As` fluid pressure is applied through the capillary 34 to the space between the bottom walls of the cups, the bottom wall ofthe y ally mounted a sensitive snap action switching device 42 mounted on a pivot 43,v supported by the casing. The switching device 42 is provided vwith an actuating plunger 44 and the switch mechanism is arranged so as to open upon de" pression of the actuating plunger 44. Slidably fitted in the wall of the casing is a second actuating plunger 45 which bears at one end on the bottom wall of the inner flexible cup member 31 and at its other end on the switchY actuating plunger 44.

A relatively strong diaphragm return spring 46 biased between the front casing wall and a ange Y 41 on the plunger 45 resists expansion of the element 35. A second relatively strong spring 48 at both ends as by soldering or welding and this inner tube, the capillary 34 and the expansible element 35 form a sealed system which is filled with a suitable non-freezing motion transmitting liquid such as, xylene (ortho). The longitudinal passage 25 in the outer tube 20 is filled with a suitable liquid which preferably freezes at 32P F. such as pure water. The inner tube 2| does not extend the full length of the passage 25, a small space being provided at one end as indicated at 53 to permit communication between the spaces on opposite sides of the inner tube.

The concave sides 21 of the ller bar 26 are developed so as to permit normal deflection of the thin flat sides 22 of the inner tube under uniformly distributed load and to limit thedeilection of any part of the tube to a point below the elastic limit of the material. The thin inner tube is preferably constructed of a high nickel chrome steel and has a wall thickness in the order of .002 to .004 of an inch. The inner wall surfaces 5| of the outer tube 20 which lie opposite the surfaces 21 ofthe ller 26 are developed.

so that expansion proportional to thedistance which the walls 22v are permitted to iiex at any point will occur.

A second form of feeler ll, 5 and 6 comprises an outer tube 52 of. circular cross section having a generally elliptical passageway 53 therethrough in which is fitted a thin walled inner tube 54 having substantially at opposite walls 55 and rounded ends 56. The shape of the passage 53 in cross section is such that the rounded edges of the inner tube 54 are contiguous therewith for a full 180 as indicated.v The inner tube 54 is closed at its ends `by pinching together the flat sides as indicated' at 51 in- Fig. 6. The ends are further sealed `by soldering or welding. The outer tube 52 is counterbored at each end at 58 and 59 to receive the round end. The

plugs

60 and 6| are soldered or welded to the tube 52. Thev plug 6| is perforated to receive one end of a capillarytube 34a, the other end of which may be attached to the expansible element 35. In this form of bulb, the passage 53 in outer tube 52 is therefore connected to the expansible element and together'` with the expansible element and capillary tube form a closed system which is lled with a suitable non-freezing liquid. The inner tube 54 1 being hermetically sealed is iilled with a freezing liquid such as pure water. l I

The curved walls 32 of the passage 53 in outer f tube 52 are likewise developed so as to permit normal deflection of the inner tube walls- 55 under uniform load and to limit the deflection to a point The end"1 plugs of the outer tubes of both formsof feeler f bulbs are provided with short pieces of capillary, tubing 63 to facilitate lling the outer tubesj' These capillary tubes are pinched and soldered" below the elastic limit of the material.

closed after the outer tubes have been lled.

In operation The feeler bulb is placed in the water filledj:

. cooler and spaced at the desired distance from biased between the rear wall of the casingandv the wall or the evaporator coils.

sition, the temperature of the bulb and the water bulb as shown vin Figs.

If the ice bank.' is not thick enough to touch the bulb injthis po'- the, tube would ordinarily result. The cur-ved` Walls 211' of' the filler bar 2f,` inthe first form of bulb described and' the curved walls S2 of the outer tube in the second form of bulb described, prevent undue deflection of the thin tube walls at any point and force the freezing mixture which is still suiiiciently fluent to permit this, to uniformly deflect these walls both longitudinally and transversely, As hereinbefore stated, the curvature of walls 2'! and @2 is such that the thin tube walls cannot be stressed beyond the elastic limit.

By the use of a sensitive switching device requiring only a slight actuating movement in the order of .002 or .003 inch and the use of a liquid motion transmission medium together with a metal diaphragm type expansible element which altogether results in a positive unyielding transmission of motion, the actuation of the switching device may be achieved by expansion resulting from only partial freezing cf the water within the feeler bulb. In the present invention, I have proportioned the volumes of Vthe freezing and non-freezing liquids within the bulb and the expansible element 35 so as to achieve switch actuation with not more than 25 per cent of the total expansion of the water in the bulb which would occur between water at 32 F. and solid ice at 32 F. Thus it will be seen that in normal operation the water within the bulbs does not completely solidify and the inner tube walls are not deflected to the permissible limit.

The device may however be subjected to temperatures considerably below 32 F. in shipment or in storage when not in use. The relation of the permissible displacement of the inner tube walls to the volume of water within the tube is made such therefore, as to permit total expansion of the water upon complete solidifica tion and some additional expansion of the solid ice as may occur in atmospheric temperatures likely to be encountered. It will be understood that the principles set forth hereinabove may be applied to a design of feeler bulb employing a flat circular diaphragm as well as the preferred round, elongated tube design shown and described.

I claim:

1. In a device of the class described, a temperature sensitive bulb comprising a relatively thick walled outer tube of circular cross-section, a relatively thin walled inner tube flattened s0 as to have relatively extensive and substantially flat and parallel opposite side walls and rounded edges arranged within said outer tube, an elongated filler member within said inner tube extending substantially the full length thereof, said illler member having rounded edges contiguous with the rounded edges of said inner tube and having transversely concave surfaces opposite the flat walls of said inner tube, said outer tube having sealed ends and containing a freezing liquid, said inner tube being sealed at one end and containing a non-freezing motion transmission fluid, an outlet at the other end of said inner tube, and means Dmlldiletcmmunicaticn between` tlnelspaces;1y'-- mena ennostei sides of said euer member. .i

2a A temperature, sensitive bulb as set forth in claim` 1- in which; the curvature of the; concave surfaces; ot the filler member are such thatdeflec.- tien of the flat surfaces. of said inner tube to the` extent. that theyare contiguous therewith relatively thin walled metal innerV tube of non-` circular cross section arranged therein, said inner tube having an elongated member disposed therein and extending substantially the full length thereof for limiting the extent to which said inner tube may be collapsed transversely, said inner tube having a conduit connected to one end thereof which extends exteriorly of said outer tube and is connected to said expansible chamber, said outer tube containing sealed therein a quantity of freezing liquid, and said inner tube, said connecting conduit and said expansible chamber being filled with a non-freezing motion transmitting liquid.

4. For use in a fluid pressure operated refrigeration control device having an expansible chamber, a remote sensitive bulb comprising a charnber having a relatively rigid surrounding wall and being divided by a relatively thin normally flat flexible metal wall, one of the divisions of said -chamber being sealed and containing a freezing liquid, the other division having communication with said expansible chamber and being filled with a non-freezing motion transmitting liquid, said rigid bulb chamber wall deilning said last mentioned division being arcuate and being subtended by said flat flexible metal wall, and the curvature of this wall being such that said flexible metal wall may be deflected at any point so as to be contiguous therewith without exceeding its elastic limit at any point.

5. In a device of the class described an expansible chamber, a remote temperature sensitive bulb comprising a chamber divided by a normally flat relatively thin flexible metal wall into ilrst and second divisions, said bulb chamber Walls forming relatively flat arcuate curves on both sides of said flexible metal wall and being subtended thereby, the curvature of the chamber Wall defining said second division being such that said flexible metal wall may be deflected at any point sufficiently so as to be contiguous therewith without exceeding its elastic limit, said first chamber division being sealed and filled with a freezing liquid, and said second division having communication with said expansible chamber together with which it forms a sealed system lled with a non-freezing motion transmitting liquid.

6. For use in a fluid pressure operated refrigeration control device having an expansible chamber, an ice detecting bulb comprising a chamber divided into first and second divisions by a relatively thin flexible metal wall, said opposite chamber Walls being curved so as to form relatively flat arches on both sides of said flexible metal dividing Wall, said ilrst chamber division being sealed and filled with a freezing liquid, said second chamber division having communication with said expansible chamber and being lled with a non-freezing motion transmitting liquid, the curvature of said second chamber division wall being such that stress and deflection is substana tially equal at alll points on said flexible metal ywallg when deflected so as to be contiguous therewithi andthecurvature of said rst chamber division Wall being 'such that the expansion at any point thereon acting normally to said iexible metal wall 5 CLIFTON A. COBB.

REFERENCES CITED ...i-,The following references are of record in the,

file; of this patent:

Number Number 8 UNITED STATES PATENTS Name Date Powers Dec. 10. 1889 Powers Feb. 11, 1896 Halsey Nov. 26, 1918 Swift Oct. 19, 1920 Smilack Dec. 29, 1936 Wood Jan. 16, 1940 Miller Nov. 16, 1948 FOREIGN PATENTS Country Date Great Britain Mar. 27, 1924 Germany Oct. 22, 1930