US2294552A - Refrigerating condensing unit - Google Patents

Description

Sept l, 1942. i E GYGAX. 2,294,552

REFRIGERATING CON-DENS-ING UNIT Original Filed May 15, 1937 2 Sheets-Sheet 1 k Y' J Z7 2,9 rlq 5/ 219 J-fg. Q

Sept. l, 1942.` E. GYGAX 2,294,552

REFRIGEHATING CONDENS'ING UNIT Original Filed May 13, -1937 2 Sheets-Sheet 2 Patented Sept. l, 1942 eras -rNr orFlcs REFRIGERATING CONDEN SING UNIT Ernest Gygax, St. Louis, Mo., assigner to Curtis Manufacturing Company, Wellston, Mo., a corporation of Missouri 3 Giaims.

This invention is a division of my pending application, Serial No. 142,395, led May 13, 1937. Said application has matured into Patent No. 2,178,100.

This invention relates to refrigerati-ng 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 of operation 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 sufcient supply of lubricant in their respective crankcases to maintain satisfactory operation. This is often attempted when two compressors are connected to a common suction 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 therebetween. When, however, a difference exists between the pressure in the crankcases of the respective compressors, such a line 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 which the evaporator is exposed varies and after a shutdown of the system, a rather high positive pressure exists in the compressor suction line. This makes it very difficult to start the Compressor after a shutdown period and often results in the stalling of the driving motor.

It is an object of this invention to provide a device to ease the starting load of refrigeration compressors.

The above and other objects will become apparent from the following detailed description and accompanying drawings of my invention. In the accompanying drawings:

Figure 1 is a diagrammatic view of a portion of a condensing unit embodying some of the controls of this invention.

Figure 2 is 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.

Figure 4 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: l indicates a driving motor equipped with a pulley 3 and driving compressors 5 and 'l through belts 9. Each compressor has its suction, intake, or inlet, side connected to a common suction line l l through passages or pipes i3 and l5. The outlet of each compressor is connected to an oil separator Il by lines I9. A line 2| may connect with a refrigeration condenser, of any of the many types known in the art, which is not shown in the drawings. An oil return line 23 connects the oil separator with the crankcases 25 and 21 of the respective compressors. One form of oil equalizing device is shown in Figure 1 in which an oil equalizing line 29 connects with the crankcases of each compressor and has a valve 3| inserted therein, the function of which will presently be described. Outlets 32 to the equalizing lines may be placed above the safe oil level in the orankcases. Lines 33 and 35 communicate the pressures in the respective crankcases of the compressors to this valve. n.

detailed view of this valve is shown in Figure 4. A modulating or choke valve 3l!` may be inserted in the suction inlet connection to one of the compressors and has a line 39 communicating with the common suction line II. This valve is of a type well known in the art which closes when the 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 3l is of a type which will open when the pressures communicated to it by the lines 33 and 35 are substantially equal but will close when a predetermined difference in pressure exists between the lines 33 and 35. This valve may comprise a body portion 49 in which the oil lines 29 may be inserted. A piston 42 may slide in an opening or bore 44. A passage 46 cooperates with passages 43 in the body portion to allow oil or other uid to pass through the valve when it is in the position shown. The pressure in the respective compressor crankcases is communicated to the chambers 52 and 54 by the lines 33 and 35. The chambers may be closed by plates 55 against which springs 58 may press to maintain the piston by acting against rods 69. It 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 pressure 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 ilow of oil through the pipes 29.

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 4I 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 different method of controlling the oil flow in the equalizing line has been provided in the form of a reservoir 41, a float valve 59 and associated float 5t. It should also be noted that the line from the crankcase of compressor extends to a low level in the reservoir 41. A pressure relief valve 5I is placed in a line 53 which enters the reservoir and the crankcase above the oil level. This valve 5| 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 oil level in each compressor is indicated by the line 55 and the high oil level by a line 51 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 valve in the suction inlet to one of the compressors and controlling the action of this valve by the physical conditions of the refrigerant returning to the compressors. In Figure 1 the valve shown is operated by the pressure in the common suction line. Thus in normal operation, refrigerant from the evaporating coils is drawn through the common suction line II and through the passages I3 and I5 to the compressors to be compressed and delivered through the lines I9, the oil separator I 1 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 suflicient to evaporate all of the refrigerant, the 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 the evaporating 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 evaporatoin of some of the unevaporated refrigerant. The valve 4I 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 4I 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 iollow 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-l in the refrigerant leaving the compressors will be caught in the oil separators I1 and returned to the respective compressor crankcases through lines 23. The oil in the respective crankcases may flow through the line 29 to equalize the oil level in the crankcases. It can be seen that if the valve 3| were not in the line 29, oil would flow from the crankcase 21 to the crankcase 25 when the moderating valve 31 was closed, due to the decrease in the pressure within the crankcase 25. Eventually all the oil in the crankcase 21 above the level 55 would be forced into the crankcase 25 after which refrigerant could be drawn through the line 29 from the crankcase 21 to the crankcase 25 and compressor 5. Such operation would defeat the purpose of the moderating valve 31 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 3| will close andthe unsatisfactory cycle of operations above outlined will be prevented.

In Figure 2 is shown an optional method of controlling .the iiow of oil or lubricant from one crankcase or lubricant reservoir to another. When the moderating valve 4| is open and the pressures in the compressor crankca-se substantially equal, the lubricating oil is free to flow from one crankcase to the other through the reservoir d1. The level of the lubricant in the reservoir 41 will depend upon the elevation or position of the reservoir with respect to the two crankcases. When the moderating Valve il closes and the pressure within the crankcase of the compressor 5 is thus decreased, oil will flow from the crankcase of the compressor 1 through the reservoir s1 and into the crankcase of the compressor 5. This flow cf oil will continue until the oil in the compressor 1 is reduced to the level 55 when due to the position of the outlet to the line 29 no more oil will flow but any further flow will be of refrigerant fromthe crankcase af the compressor 1. The refrigerant will flow into the reservoir 41 and force oil from this reservoir into the crankcase of the compressor 5 until the level of the oil in the reservoir allows the float 59 to fall and close the line 29 from compressor 1 by the valve 49. By this arrangement, a safe oil level is insured in each compressor and the refrigerant from the compressor 1 cannot flow into the suction side of the compressor 5. When the moderating valve is opened and the pressures 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 refrigerant which was in the reservoir can flow back through the line E3 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. This permits oil from the crankcase of the compressor 5 to raise the oil level in the reservoir i1 which in turn opens the iioat valve and allows the oil to flow back to the crankcase of the compressor 1.

Referring now to Figure 3, the numeral 19 indicates a special valve which may have a throttling or modulating control section somewhat like the valve 31 or a temperature control section similar to the valve lil, 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 or 4| are located in Figures 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 12 provided with an upper chamber 14 and a lower annular chamber 16. A valve seat 18 cooperates with a valve face or washer 89 which is secured to a piston 82. The piston operates in a cylinder bore 84 and is secured to a rod 86 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 enclosed the bellows and is secured to the body portion of the valve. A connection 98 allows a pipe |99 to be connected thereto by a nut |02. The pipe |00 may be connected to any portion of the suction line between the valve and the evaporating coils or may be connected directly to the proper side of the valve itself as shown in this drawing by a connection |94. The valves 31 and il in the Figures l and 2l show a line 39 and 45 respectively which are similar to this line and it is obvious that the line as here shown could be connected as there shown or those lines could be connected as this one is.

An adjustable stop for the piston may be provided by a rotatable rod |06 provided with a portion |93 suitable to be turned by a properly designed key or wrench. The rod passes through a packing nut HU, packing ||2 and bushing IIB. A threaded portion H6 acts with a cooperating stationary threaded portion ||8 to give the rod vertical movement when it is rotated. An end of the rod |20 which may be cylindrical in shape and oscillate in the sleeve 2|, may be provided with a washer |22 secured thereto as by a screw IZA against which the portion |25 of the piston may abut. A cap |39 covers the end of the rod. Thus it can be seen that by rotating the rod |05, the distance through which the piston 82 moves may be adjusted to vary the valve opening, A chamber |32 below the piston communicates with a passage |34 into which a line |35 may be inserted and secured as by a nut |31. The numeral |35 indicates a drain plug which may be desirable. The line |35 communicates with a solenoid valve |39.

This valve is of the usual type and will not be described in detail except that the passage between the line |35 and a line Ilil is open when the valve stem |53 is raised by the passing of an electric current through solenoid coil |145. The leads |651 and |49 from this coil pass to a current supply through a switch |59. 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 unless the compressor motor is switched on. The switch |59 is of a type which is operated by pressure communicated to it by line |52 which connects to the compressor suction line between the valve 10 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.

If the special valve 19, switch |50, and solenoid valve |39 are connected as described above and properly adjusted, a compressor can be started up on a refrigeration system which has become warm without overloading or stalling the motor due to the abnormal back pressures present.

The valve 1U as shown in Figure 3 incorporates the throttling portion, i. 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 use of the valve 31 previously described. Ob-

viously the bellows section could be interchanged with a thermostaticr sectionfsimilar yto the thermostatic valve 4| previously described and ther results would be the same. The piston portion vrof the valve yisy the part which rserves to ease thestarting load, however, and its operation is as follows:

After a refrigeration systemhas been idle for a time and the temperature of the coilsfand lines allowed to rise, the pressure of the refrigerant o inthesuction line increasesand sometimes to such an extent, depending, of course, on the ternperature, that it is diicult to start the compressor due to theincreased back pressures on the piston. f

Such diiculties are often encounteredin air conditioning systems when ,ther system may be shut down over night and restarted during the day. If these Valves are connected to the system as described, a high pressurein the suction line I claim: 1. In a device for insuring a safe oil level in each of the crankcases of a plurality of interconnected compressors, an oil reservoir, a fluid passage between said' oil reservoir and each of the crankcases'of the compressors, each of the said fluid passages having'one of its ends in communicrankcase at all times, and meansy responsive tor the level of theY contents in the oil reservoir to Y vary the passage of a fluid through one of said fluid passages.

2. In a device for insuring ya sato oil level in each of the crankcases of a plurality of interconnected compressors, an oil reservoir, a fluid passage between said oil reservoir and each of the rcrankcases of thecompressors, each of the fluid y y passages having one of yits ends in communication with the oil reservoir and its other end ex- |3 will be communicated tov the switch |58 by the tending into the crankcase of one of the interconline I 52. This high pressure will close the switch {5l}J and if thefmotor line is closed, the lines I 41 and |49 will be energizedfto open the solenoid valve 39. This allows positive pressurer from the ccmpressorfoutlet toy ,be ycOrrlrnurlicated to the chamber |32 through lines I4! and |36.,r Pressure in the chamber |32 will cause the piston to rise and close the valve face 80 against the seat '18.

Briefly, a high pressure in the suction line will f close the line when the compressor motor is started. The closing ofthe suction line will allow the compressor to start without the heavy load of the back pressure. As soon as the compressor reduces the back pressure in the suction line, the switch |50 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 used.

It is obvious that the various controls may be variously combined to meet any particular condition 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.

While I have described but several embodiments of my invention. it will be apparent to those skilled in the art that Various modifications, additions, substitutions, and omissions may be made in the embodiments shown without departing from the spirit and scope of the invention as dened in the appended claims.

case at all times, means responsive to the level of the contents in the oil reservoir to vary the passage of a fluid through one of said fluid passages, said means being arranged to permit the'V flow of fluid through the fluid passages whenever the levelof the oil in the oil reservoir is above a predetermined level, and to halt 'the'ow of fluid throughy the one iluid passage whenever the level of the oil in the oil reservoir falls to the predetermined level, and a pressure relief passage to allow the passage of a gas from the oil reservoir to one of the compressor crankcases.

3. A lubrication system for a plurality of refrigeration compressors, including a lubricant reservoir, a passage between the crankcase of each of said compressors and the reservoir, said passage having one end in communication with the oil reservoir and its other end extending into the crankcase of one of the compressors, said end of the passage that extends into the crankcase of the compressor being positioned a short distance above the bottom of the said crankcase, and being adapted to cooperate with the crankcase to maintain a safe oil level in the bottom of the crankcase at all times, a valve means to shut oi one of said passages when the level of a lubricant in the lubricant reservoir recedes below a predetermined level, and a pressure relief conduit to permit gas to flow from the reservoir to one of the compressor crankcases.

ERNEST GYGAX.

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