US2178100A - Refrigerating condensing unit - Google Patents

Description

Oct. 31, 1939. E. GYGAX REFRIGERATI'NG CONDENSING UNIT 3'. 2 Sheets-Sheet l Filed lay 13, '19

ATTORNEY.

Patented Oct. 31, 1939 t I UNITED STATES PATENT o FicE Refrigerating Machine Co Mo., a corporation of Missouri mpany, Wellston,

Application-May 13, 19's,. Serial No. 14z,s95 Claims. (cuss-'1) This invention relates to refrigerating systems and controls.

An increasingly large number of refrigerating systems are subject to varying loads on the evaporating coils. In such installations, the amount of refrigerant which is evaporated in the evaporating coils may vary considerably during short periods ofoperation of the apparatus. This is especially true of air conditioning installations where the variance of the load on the evaporating coils may be appreciable. If the load on the evaporating coils, that is, their capacity to evaporate refrigerant, becomes less than the capacity of the compressor and condenser to condense refrigerant, liquid or partially liquid refrigerant will be drawn into the compressor crankcase and produce serious damage to the compressor because of freezing of the lubricant and locking of the pistons. It is necessary, therefore, that the load or capacity of the evaporating coils or evaporator be balanced with respect to the capacity of the compressor or condensing unit.

Two compressors supplying a common load are often connected to the same suction line, powered from the same motor and mounted on the same base along with other equipment to form a condensing unit. It is often necessary to balance the output of such a condensing unit with the'capacity of the evaporator at any particular time.

The above is accomplished in the present invention by the insertion of a modulating or choke valve in the suction line of one of the compressors, and controlling it by the condition of the refrigerant in the common suction line of the condensing unit, in a manner yet to be described.

When such a system is used to control the capacity of a condensing unit and under certain other conditions of compressor operation where two compressors are interconnected, it is necessary to provide a means to insure that both compressors will retain a suflicient supply of lubricant in their respective crankcases to maintain satisfactory operation. This is often attempted when two compressors are connected to, a commonsuction line and'each provided with an oil separator in the outlet, by.- providing an oil equalizing-line.

between the compressor crankcases to equalize. the oil level tlierebetween. When, however, a difference exists between the pressure in the crankcases of the respective compressors, such aline will not'function properly as all of the lubricant will be forced from the compressor having the higher crankcase pressure to the compressor having the lower crankcase pressure.

It is, therefore, another object of this invention to'provide a condensing unit "having dual interconnected compressors with a means to insure a safe oil level in both compressors at all times.

In various installations, for example, in air conditioning installations, the temperature to I OI which the evaporator is exposed varies and after a and accompanying drawings of my invention. In

the accompanying drawings:

Figure l is a diagrammatic view of a portion of a condensing unit embodying some of the controls of this invention.

Figure 21s a diagrammatic view of a portion of a condensing unit provided with other controls of this invention.

Figure 3 is a view showing an arrangement of controls to ease starting loads.

Figured is a detailed view of one type of oil equalizing valve.

Referring now to the drawings in which the same numerals are used throughout to denote the same or similar parts, I indicates a driving motor equipped with a pulley 3 and driving compressors '5 and I through belts 9. Each compressor has its suction, intake or inlet, side connected to a common suction line ll through passages or pipes l3 and ii. The outlet of each compressor is connected to an oil separator H by lines IS. ;A line 2| may connect with ,a refrigerationcondenser,

in which an oil'equalizing line!!! connects-with I'the crankcasespf each-compressor and has. a

valve 3i insertedtherein, the function-of which will presently be" .described- Outlets '32' to the form of oil equalizing. device is shown in Figurel 1 equalizing lines-may be placed above the safe oil f' level in the crankcases. Lines v33-ancl35com-.

municate thepressures} in the respective crankcases of the compressors to this valve. A detailed view of this valve is shown in Figure 4.-- A modu-.

' and has a line I9 communicating with the common suction line II. This valve is of a type well known in the art which closes when the suction pressure made available to it by the line 39 decreases below a predetermined value and opens again when the pressure increases above a predetermined value. The 'valve ll is of a type which will open when w the pressures communicated to it by the lines '33 and are substantially equal but will close when a predetermined diiference in pressure exists between the lines 33 and 35. This valve may comprise a body portion in which the oil lines 29 may be inserted. A piston l2 may slide in an opening or bore 44. A passage 46 cooperates with passages U in the body portion to allow oil or other fluid to pass through the valve when it is in the position shown. The pressure in the respective compressor crankcase is communicated to the chambers 52 and N by the lines 33 and 35. The chambers may be closed by plates 88 against which springs 58 may press to maintain the piston in position by acting against rods 80. In can be seen that when the pressures at the opposite ends of the valve piston are equal the valve passages will meet and allow oil to pass but when the pres-,

sure on one side of the piston is different from that on the other side, the passages will not be in line due to movement of the piston and will effectually prevent any how of oil through the pipes 28.

The arrangement shown in Figure 2 provides for the actuation of the moderating or choke valve by thermal means instead of pressure means and the moderating valve ll there indicated is of a type well known in the art, which will close when the temperature communicated to it decreases below a predetermined point but will open again when the temperature communicated to it-increases above a predetermined point. The temperature may be communicated to the valve by a tube 43 containing an expansible liquid and a line 45.

In Figure 2 a slightly difl'erent method of controlling the oil flow in the equalizing line has been provided in the form oi a reservoir 41, a float valve 48 and associated float Bil. It should also be noted that the line from the crankcase of compressor 5 extends to a low level in the reservoir 41. A pressure relief valve II is placed in a line 53 which enters the reservoir and the crankcase above the oil level. This valve ii is of a well known type arranged to allow passage of a gas in one direction only, in this case, from the reservoir to the crankcase. The safe all level in each compressor is indicated by the line I! and the high oil level by a line I! in the drawings.

The operation of the choke valve or moderating valve will first be described. As previously stated, it is necessary to control the output of the condensing unit in accordance with the load on the evaporating coils so as to prevent liquid or partially liquid refrigerant from being drawn in the refrigerator compressors through the suction lines. Such control is necessary with a dual compressor'condensing unit as shown in the Figures 1 and 2 and is accomplished in this invention by inserting a moderating or choke vaivevin the suction inlet to one of the compressors and con trolling the action of this valve by the physical conditions of the refrigerant returning to the compressors. In Figure l the valve shown is operated by the pressure in the common suction line. Thus in normal operation, refrigerant from the evaporating coils is drawn thr ugh thc'common suction line I I and through the passages l8 and ii to the compressors to be compressed and delivered through the lines IS, the oil separator l1 and line 2| to a condenser where the refrigerant is condensed after which it passes to the evaporating coils to be evaporated. If the load on the evaporating coils is not sufllcient to evaporate all of the refrigerant, the suction pressure in the common suction line will fall and cause the moderating valve 31 to close in accordance with the pressure communicated to it through line 39 and thus reduce the flow of refrigerant into the compressor 5 which in turn will reduce the output of the condensing unit until the evaporating coils evaporate all the refrigerant which they receive and the pressure in the common suction line returns to normal.

It is obvious that such a control is very sensitive and accurate and will maintain a balance between the condensing unit capacity and the load on the evaporating coils even though the load may vary appreciably during short periods of time.

In Figure 2 the moderating or choke valve is controlled by the temperature within the common-suction line. Thus when theevaporating coils do not evaporate all of the refrigerant produced by the condensing unit, the temperature within the common suction line will fall due to the evaporation of some of the unevaporated reirigerant. The valve H is arranged to close when the temperature in the common suction line decreases below a predetermined value and hence a decrease in temperature by causing this valve to close will cause a reduction in the input to the compressor 5 which will decrease the output of the compressor enough to allow the evaporating coils to become balanced with the condensing unit.

Either of the modulating valves 31 or II need not be located at the precise point shown, they may for instance be located on or in the compressors if desired and control the capacity of the suction inlet thereto. The function of these valves is to regulate the compressor capacity by changing the compressor intake opening.

In compressors where the suction inlet is made to the compressor crankcase it is obvious that the pressure in the crankcase of the compressor provided with the moderating valve on its intake side will vary with the opening and closing of this valve. When the valve chokes or reduces the suction inlet the pressure will decrease in the crankcase while an increase in pressure will follow the opening of the moderating or choke valve.

When the moderating valve is open and both compressors are operating normally any oil which is present in the refrigerant leaving the compressors will be caught in the oil separators l1 and returned to the respective compressor crankcases through lines 23. The oil in the reto the crankcase 2! when the moderating valve 81 was closed, due to the decrease in the pressure I within the crankcase 2!. Eventually all the oil in the crankcase 2'! above the level II would be I forced into the crankcase 28 after which refrigerant could be drawn through the line 28 from the crankcase 21 to the crankcase II and compressor 5. Such operation would defeat the pur pose of the moderating valve 81 and makes the use of a valve similar to the Valve 3| desirable. The valve 3| is interposed in'the line 29- and may have, pressure lines 33 and 35 communicating with the pressure in each of the compressor crankcases. The valve is arranged so as to open only when the pressures within the compressor crankcases as communicated to it by the lines 33 and 35 are substantially equal. Thus when the moderating valve is open and the pressures within the compressor crankcases are substantially the same, the valve 3| will be open and allow the oil level in the two crankcases to become equalized. When, however, the-pressures in the two crankcases become unequal, 'due to the operation of the moderating valve, the valve 3I will close and the unsatisfactorycycle of operations above outlined will be prevented.

In Figure 2 is shown an optional method of controlling the flow of oil or lubricant from one crankcase or lubricant reservoir to another. When the moderating valve H is open and the pressures in the compressor crankcases substantially equal, the lubricating oil is free to now from one crankcase to the other through the reservoir 41. The level of the lubricant in the reservoir 41 will depend upon the elevation or posi-. tion of the reservoir with respect to the two crankcases. When the moderating valve 4I closes and the pressure within the crankcasebi' the compressor is thus decreased, oil will flow from the crankcase of the compressor 1 through the reservoir 41 and into the crankcase of the compressor 5. This flow of oil will continue until the oil in the compressor I is reduced to the level 55 when due to the position of the outlet to the 7 line 29 no more oil will flow but any further flow within the crankcase become substantially equal again, oil will be forced from the crankcase of the compressor 5 back into the oil reservoir. The gas or refrigerantwhich was in the reservoir can flow back through the line 53 and valve 5|, which allows it to pass only one way, that is, into the crankcase of the compressor, to release the gas pressure from the reservoir 41. Thispermits oil from the crankcase of the compressor 5 to raise the oil level in the'reservoir 41 which in turn opens the float valve and allows the oil to flow back to the crankcase of the compressor I.

Referring now to Figure 3, the numeral "I0 indicates a special valve which may have a throttling or modulating control section somewhat like the valve 3'! or a temperature control section similar to the valve 4|, and a piston controlled section which will be described. This valve, when used with dual compressors, may be located in the line where valves 31 orv 4| are located in Fflgures 1 and 2 respectively. If used on only a single compressor, the valve may-be located on the suction line. A valve which has been used and found to give satisfactory results is shown in Figure 3 although it will be apparent that other types of valves may be designed to perform the same function-as this valve. The valve may comprise a body portion I2 provided with an upper chamber I4 and a lower annular chamber I6. A valve seat I8 cooperates with a valve face or washer 80 which is secured to a piston 02. The piston operates in a cylinder bore 84 and is secured to a rod- 80 which may pass through a bushing 88 and packing 90 to be secured to a bellows 92- through a plate 94. A gas tight cover 96 encloses the bellows and is secured to the body portion of the valve. A connection 08 allows a pipe I00 to be connected thereto by a nut I02. The pipe I00 may be connected to any portion of the suction line between the valve and the evaporating coils or may be connected directy to the proper side of the valve itself as shown in this drawing by a connection I04. The valves 31 and 4I.in the Figures 1 and 2 show a line 39 and 45 respectively which are similar to this line and it is obvious that the line as here vided by a rotatable rod I05 provided with a portion I 00 suitable to be turned by a properly designed key or;wrench. The rod I08 passes through a packing nut II 0, packing H2 and bushing II4. A threaded portion II6 acts with a cooperating stationary threaded portion I I8 to give the rod vertical movement when it is rotated. An end of the rod I which may be cylindricalin shape and oscillate in the sleeve I2 I, may be provided wlth'a washer I22 secured thereto as by a screw I24 against which portion I 20 of the piston may abut. A cap I covers the end of the rod. Thus it can be seen that by rotating the rod I 06, the distance through which the piston 82 moves may be adjustedto vary the valve opening. A chamber I32 below the piston communicates with a passage I34 into which a line I36 may be inserted and secured as by a nut I31. The numeral I35 indicatesa drain plug which may be desirable. The line I30 communicates with a solenoid valve I.

This valve is of the usual type and will not be described in detail except that the passage between the line I36 and a line MI is open when the valve stem I43 is raised by the passing of an electric current through solenoid coil I45. The leads I41 and I49 from this coil pass to a current supply through a switch I50. The current supply is connected to the motor line of the compressor of the refrigeration system which is being controlled so that the solenoid valve will be inoperative unswitch I50 is of a type which is operated by pressure communicated to it by line I52 which connects to the compressor suction line between the valve I0 and the compressor. The switch is arranged so that when the pressure communicated to it exceeds a predetermined value, it will close the circuit to operate the solenoid valve.

It the special valve 10 switch I50 and solenoid valve I30 are connected as described above and less the compressor motor is switched on. The

properly adjusted, a compressor can be started 1 the-throttling portion, 1. e., the part controlled by the. bellows along with the piston portion-which is necessary to ease the starting load. The throttling portion operates similarly to the valve 31 previously described. When the pressure in they suction line between evaporator and the valve drops too low, the bellows moves the face 00 against the seat is by raising the rod to, thus I! allowed to rise, the pressure of the refrigerant in maintaining a constant suction pressure and bringing about the general results obtained by use of the valve 31 previously described. Ob-

viously the bellows section could be interchanged with a thermostatic section similar to the thermostatic valve 4| previously described and the results would be the same. The piston portion or the valve is the part which serves to ease the starting load, however, and its operation is as follows:

Alter a refrigeration system has been idle for a time and the temperature or the coils and lines 1 as described, a high'pressure in the suction line I! will be communicated to the switch I50 by the line I82. This high pressure will close the switch 150, and, it the motor line is closed the lines I" and I will be energized to open the solenoid valve I. This allows positive pressure from the compressor outlet to be communicated to the chamber I32 through lines ill and ISO. Pressure in the chamber I32 will cause the piston to rise and close the valve face against the seat 18.

Briefly, a high pressure in the suction line will close the line when the compressor motor is started. The closing of the suction line will allow the compressor to start without the heavy load oi the back pressure. As soon as the compressor reduces the back pressure in the suction line, the switch I50 will open, closing the solenoid valve and allowing the valve face 80 to recede from its seat until the pressure rises too high again.

I have thus provided a device which allows the starting load on a refrigeration compressor to be appreciably reduced. This will obviate the necessity of special motors and electrical equipment and will add to the life of refrigeration equipment being It is obvious that the various controls may be variously combined ,to meet any particular con-' dition desired. Thus either type of throttling section could be used with either type of oil equalizing valve and either with or without the unloading section. The number of compressors might also be one, two or more, depending on the particular system used.

I While I have described but several embodibe made in the embodiments shown without decompressor suction line, a modulating valve in the suction line, means to reduce the opening of .the .modulating valve when the temperature within the suctionline falls below a predeter-' mined value, driving means for said compressor and means to close the valve when the 'driving means" is energized it the pressure in the compressor crankcase exceeds a predetermined value.

3. In a refrigeration system, a compressor, a compressor suction line, a modulating valve in the suction line provided with a bellows section to move the valve towards its closed position when.

the pressure in the suction line falls below a predetermined value and a piston section operated by pressure from the compressor, said pressure being available to the piston section through a solenoid valve which is opened in response to a rise in the pressure in the compressor crankcase above a predetermined value.

4. In a refrigeration system, a plurality of compressors, a common suction line, a passage between each of the compressors and the common suction line, a modulating valve in one of said passages provided with a section to reduce the valve opening when the pressure or temperature in the common suction line falls below a predetermined value and another section operated by pressure irom one of the compressors, said pressure being controlled by an electric solenoid valve which is opened by an electric switch when the pressure in the compressor crankcase exceeds a predetermined value.

5. In a refrigeration system two compressors having their suction lines connected to a common suction line, a modulating valve in the suction line 0! one of the compressors, means operative to move the modulating valve to closed position as the pressure in the common suction line decreases below a predetermined point, driving means for said compressor and means operable when the driving means is energized to move the modulating valve to the closed position it the pressure in the compressor crankcase exceeds a predetermined value.

- ERNEST GYGAX.

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