US3772896A

US3772896A - Heat exchange unit to regulate the temperature of recirculating hydraulic fluid for operating hydraulic systems of machinery

Info

Publication number: US3772896A
Application number: US00231509A
Authority: US
Inventors: R Prabhakar
Original assignee: Fluidics Inc
Current assignee: Fluidics Inc
Priority date: 1972-03-02
Filing date: 1972-03-02
Publication date: 1973-11-20
Anticipated expiration: 1990-11-20

Abstract

A heat exchange unit to maintain the temperature of an aqueous non-toxic and non-flammable hydraulic fluid supplied from a reservoir to enclosed hydraulic systems of machinery used in confined areas, such as mines and the like, within a desired temperature range.

Description

United States Rao [ Nov. 20, 1973 HEAT EXCHANGE UNIT TO REGULATE THE TEMPERATURE OF RECIRCULATING HYDRAULIC FLUm FOR OPERATING HYDRAULIC SYSTEMS OF MACHINERY [75] Inventor: Prabhakar B. R. Rao, Cincinnati,

Ohio

[73] Assignee: Fluidics, 1nc., Cincinnati, Ohio [22] Filed: Mar. 2, 1972 21 Appl. N0.: 231,509

2,210,121 8/1940 Jewell 60/53 2,467,398 4/1949 Miller 62/243 2,511,582 6/1950 Grindrod.... 62/98 2,596,195 5/1952 Arbuckle 62/435 2,888,810 6/1959 Hamm 62/226 2,929,212 3/1960 Lewis 60/52 3,603,105 9/1971 Figa 62/230 Primary ExaminerWil1iam J. Wye Attorney-John W. Melville et a1.

[57] ABSTRACT A heat exchange unit to maintain the temperature of an aqueous non-toxic and non-flammable hydraulic fluid supplied from a reservoir to enclosed hydraulic systems of machinery used in confined areas, such as mines and the like, within a desired temperature range.

12 Claims, 12 Drawing Figures 1 I 2024 4004 F4 mp I easzzeyo/z PATENTEI] BUY 2 0 I975 sum 2 BF 9 Pmmmuovzo 1913 3772.896

sum 3 GF 9 PATENTEBHHVPO I975 SHEET 5 CF 9 WMY PATENTEUHUY 20 1975 SHEET 6 BF 9 PAIENTEUMJVPU 197s SHEET 7 EF S) PATENTEDMW 20 I915 SHEU 8 BF 9 HEAT EXCHANGE UNIT TO REGULATE THE TEMPERATURE OF RECIRCULATING HYDRAULIC FLUID FOR OPERATING HYDRAULIC SYSTEMS OF MACHINERY BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to improvements in heat exchangers for heat exchange between liquids, and more particularly to a heat exchange unit to maintain the temperature of an aqueous, non-toxic and nonflammable hydraulic fluid supplied from a reservoir to enclosed hydraulic systems for machinery used in confined places, such as coal mines, within a desired temperature range.

2. Description of the Prior Art 7 The operation of enclosed hydraulic systems of machinery used in confined areas, such as coal mines and the like, where proximity to personnel and the danger of fire and explosion make it desirable that the hydraulic fluid be non-toxic, non-flammable and nonexplosive even if sprayed in atomized form in a confined enclosure, have led to substantial efforts to develop a hydraulic fluid for use in such systems which will meet these requirements.

While the prior art has long been concerned with de veloping a non-toxic and non-flammable hydraulic fluid for use in enclosed hydraulic systems of machinery used in confined spaces, a satisfactory hydraulic fluid meeting the aforementioned requirements has only been recently developed. Reference is hereby made specifically to a patent application filed concurrently herewith in the names of James A. Peek, Peter V. Croft and Elliot H. Myers, entitled METHOD OF ACTUATING ENCLOSED HYDRAULIC SYSTEMS AND AQUEOUS FLUID THEREFOR, application Ser. No. 231,724, filed March 3, 1972, and assigned to the assignee of the present invention, wherein an aqueous, non-toxic, non-flammable hydraulic fluid having good dispersant, extreme pressure, lubricity, corrosioninhibiting and anti-foam properties is disclosed.

It has been found that if the aforementioned fluid is circulated through enclosed hydraulic systems from a reservoir and returned to the reservoir, and if the temperature of the aqueous hydraulic fluid supplied from the reservoir is regulated within the temperature range of 60 85 F, the temperature of the fluid anywhere in the hydraulic system not exceeding about 90F, a satisfactory hydraulic fluid meeting all of the aforementioned requirements is obtained It will, of course, be quickly understood that the use of hydraulic fluid in an enclosed hydraulic system causes such fluid to reach an exceedingly high temperature, in the range of 120 to 220 F, as it acts as a power fluid for the machinery in the system. Accordingly, in order for the aforementioned hydraulic fluid to achieve satisfactory results as a power fluid in the enclosed hydraulic systems of machinery, such as continuous mining machines, shuttle cars and other machinery used in the mining industry, it was necessary to develop a heat exchange unit which could carefully regulate the temperature of the hydraulic fluid. Many prior art heat exchange units were considered, but quickly discarded because they were unable to maintain careful regulation of the temperature of the hydraulic fluid over an extended period of time. Additionally, such prior art heat exchangers have many other shortcomings, in-

eluding size, inefficiency, lack of dependability under difficult mining conditions, lack of mobility and substantial dependence upon other external sources in order to function. Such prior art heat exchangers are also extremely expensive, highly unreliable becuase of the failure of their electrical control components, and initial starting of electrically driven units tend to stall. Finally, such prior art heat exchange units are not totally explosion proof and maintenance free under difficult mining conditions.

SUMMARY OF THE INVENTION It is a principal object of the present invention to provide a heat exchange unit for carefully controlling the temperature of an aqueous non-toxic, non-flammable, hydraulic fluid used to actuate enclosed hydraulic systems of machinery, such as continuous mining machines, shuttle cars and other mining equipment, used in confined places, such as coal mines, wherein the fluid is supplied from a reservoir to the enclosed hydraulic systems, circulated under pressure to the systems and returned to the reservoir for reuse, so as to prevent any reaction of any of the components of the fluid with alkaline earth ions and to prevent any deposit of any components at any point in the system.

According to the invention, the above object is achieved by a heat exchange unit which includes a hydraulic motor operable by at least a portion of the hydraulic fluid in the hydraulic system. A hydraulic motor speed control, including a bypass circuit for hydraulic fluid not used to operate the hydraulic motor, controls the speed of the motor. A heat exchanger is provided in communication with the bypass circuit, the hydraulic motor, and a reservoir, and receives substantially all of the hydraulic fluid from the machinery. The heat exchanger provides for heat exchange between the hydraulic fluid and a heat exchanger medium, whereby the hydraulic fluid is cooled within a desired temperature range and returned to the reservoir. The desired temperature range is preferably within the range of 60 85 F, with the temperature of the hydraulic fluid anywhere in the systemnot exceeding about 90F.

A source of heat exchanger medium for the heat exchanger unit is provided. A compressor operable by the hydraulic motor is in communication with the heat exchanger, the compressor receiving the heat exchanger medium as it exits from the heat exchanger in vaporized form, whereby the vaporized heat exchange medium is compressed. A condenser, including fan means operable by the hydraulic motor to pull ambient air through and around the condenser, is in communication with the compressor and the heat exchanger for the heat exchager medium so as to regulate the temper- .ature of the hydraulic fluid in the hydraulic system within the desired temperature range.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is schematic diagram showing the heat exchange unit of the present invention as used with various hydraulic systems which actuate the machinery involved.

FIG. 2 is a schematic diagram showing the operation of the heat exchange unit of the present invention.

FIG. 3 is a plan view of the heat exchange unit according to the present invention.

FIG. 4 is a left side elevational view of the heat exchange unit according to the present invention.

FIG. 5 is a right side elevational view of the heat exchange unit according to the present invention.

FIG. 6 is a rear elevational view of the heat exchange unit according to the present invention.

FIG. 7 is a rear elevational view of an alternate heat exchange unit according to the present invention.

FIG. 8 is an exploded view showing the heat exchanger of the heat exchange unit according to the present invention.

FIG. 9 is a cross sectional view taken on the line 9 9 of FIG. 5 showing the thermostatic expansion valve.

FIG. 10 is an exploded view of the thermostatic expansion valve of FIG. 9.

FIG. 11 is a cross sectional view taken on the line 11 11 of FIG. 3 showing the load compensation valve.

FIG. 12 is a side elevational view, partially broken away, of the valve of FIG. 11.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1, an enclosed hydraulic system 10 having a reservoir 12 which provides a supply of aqueous hydraulic fluid, is disclosed. The fluid is diluted to the desired concentration either prior to introduction into the reservoir, or with suitable mixing equipment, the concentrate can be introduced into the reservoir and sufficient water added to achieve the desired concentration. Although the type of hydraulic fluid is not a limitation on the heat exchange unit of the present invention, preferably the hydraulic fluid utilized is in accordance with that disclosed in the aforementioned patent application filed concurrently herewith in the names of James A. Feck, Peter V. Croft and Elliot H. Myers, entitled METHOD OF ACTUATING ENCLOSED HYDRAULIC SYSTEMS AND AQUE- OUS FLUID THEREFOR, and assigned to the assignee of the present invention.

The hydraulic system 10 includes flexible conduits 15 and I7 and the like leading to the various hydraulic systems which actuate the machinery involved, and therefrom return back to the reservoir 12, preferably existing on either a continuous mining machine 16, or a shuttle car 18, or any other hydraulically actuated machinery. The flexible conduits l5 and 17 are high pressure lines leading to actuators and hdyraulic motors. Hydraulic fluid to the pump or the like is directed through the intake line 19 from the reservoir 12. It will, of course, be understood that a plurality of

machines

16 and 18 may be connected to a single reservoir 12 and that one or more pumps 20, including a power source in combination therewith, such as the electric motor 22, the pumps 20 being mounted on the

machines

16 and 18, as well as gravity flow, will be utilized for circulation of the hydraulic fluid in the hydraulic system 10.

As can be seen from FIG. 1, the hydraulic fluid in the enclosed system 10 is caused to pass to a heat exchange unit 24 of the present invention having a capacity, for example, of up to about 35,000 B.T.U.s per hour,ifthe hydraulic system 10 includes only one machine such as a continuous mining machine 16. However, it will, of

course, be understood that the required capacity of the heat exchange unit 24 as well as the number of heat exchange units 24 which are included in the hydraulic system 10 will vary depending upon the number of hydraulically actuated machines being operated within the system 10.

The hydraulic fluid in the hydraulic system 10 will be regulated to a temperature of F, but not exceeding F, by the heat exchange unit 24. In general, the heat exchange unit 24 will be located immediately after the

machinery

16 and 18 and before the reservoir 12, in which case the hydraulic fluid is pumped therefrom to the reservoir 12.

Normally hydraulically actuated

machines

16 and 18 are equipped with one or more reservoirs. The reservoirs l2 mentioned herein will preferably be such reservoirs. While the temperature of the fluid is caused to increase slightly upon passing through the recirculating systems, it has been found that operation in the manner disclosed in acoal mine does not result in an increase in temperature of the hydraulic fluid above 90F. because of continuous circulation of the fluid through the hydraulically actuated

machines

16 and 18, back to the heat exchange unit 24, and then again to the reservoir 12.

Introduction of fine abrasive particles into the hydraulic fluid of the hydraulic system 10 of the present invention cannot be avoided in ordinary operation, but the flow of fluid can be relied upon to entrain most of the contaminants and to carry them back to the reservoir 12 where a major proportion will settle to the bottom by gravity. As shown in FIG. 2, provision can of course be made to withdraw these contaminants from the bottom of the reservoir 12 periodically, and the supply conduits 14 leading to the reservoir 12 and the intake line 19 of the hydraulic machinery preferably are positioned intermediate the top and bottom thereof in order to avoid re-en'trainment of contaminant particles. A magnetic chip collector 13 may also be utilized.

Referring now to FIG. 2, which discloses a schematic diagram of the heat exchange unit 24 of the present invention, as well as to the plan and elevational views of FIGS. 3 through 6, it will be seen that the heat exchange unit 24 includes a hydraulic motor 26 which is operable by at least a portion of the hydraulic fluid in the system 10. A hydraulic motor speed control valve 28 controls the amount of hydraulic fluid which is directed to the hydraulic motor 26, and thus the speed thereof. In practice, hydraulic fluid is directed through the speed control valve 28 and into a high pressure line 30 leading to the motor 26. The position of the hydraulic line down stream of speed control valve 28 is the priority flow line at high pressure connected to high pressure line 30 going into the hydraulic motor 26. The speed control valve 28 admits only the specified amount of flow through the priority flow line 29 at high pressure to the motor 26 and maintains constant speed under varying speed and flow conditions of the hydraulic pump 20. The hydraulic motor 26 will be running at constant speed under varying conditions of heat load generated by the hydraulically actuated machinery l6 and/or 18. The flow going through the hydraulic motor 26 is adjusted to handle a capacity of up to 35,000 B.T.U.s/hr or less depending upon the type and number of hydraulic machines in the system 10.

An alternate method of close temperature regulation within the desired range would be to either manually or automatically varying the speed of the hydraulic motor '26 by means of the conventional flow control valve 28 shown in FIG. 2, in proportion to the heat load generated by the hydraulic equipment on a

machine

16 and 18. Increasing and decreasing the opening of the flow control valve 28 results in more or less flow to the hydraulic motor 26, and thus more or less speed thereof and can be accomplished by sensing thetemperature rise in the hydraulic system 10, such as at the reservoir 12.

That portion of the hydraulic fluid not directed into the high pressure line 30, as shown in FIG. 2, is directed into the bypass line 32, which is at a lower bypass pressure and leads into the heat exchange unit 24. The portion of the hydraulic fluid not directed into the high pressure line, in the line 17, could be made to actuate subcooler 60 is a conventional cooling unit which includes an elongated chamber 62 through which vapor-.

ized heat exchanger medium passes, the vaporized medium from the heat exchanger 34 entering and exiting at opposite ends 62a and 62b of the chamber 62. The condensed heat exchanger medium is cooled further as it passes through the conduit 74A and the inlet 61A of the subcooler 60, out through the outlet 61B and into the conduit 74B. The usual finned conduit 64 runs through the chamber 62 and provides passage for condensed heat exchanger medium, as will be more fully hydraulic'machinery by providing a high pressure relief valve in the line 17 before directing the line to an actuator or motor on hydrualically actuated machinery, as shown in FIG. 1. After having done the work, the hydraulic line 17 returns at a lower pressure and is directed into line 32, as shown in FIG. 1. As will be more fully explained hereinafter, the hydraulic fluid exiting from the hydraulic motor 26 in the high pressure line 30 subsequently combines with the hydraulic fluid in the bypass line 32 prior to passing through the heat exchanger or evaporator 34, where the hydraulic fluid is cooled and then returned to the hydraulic system 10, such as to the reservoir 12 on the

machinery

16 and 18, through the discharge line 183.

The heat exchanger 34 may be of acceptable conventional design, but is preferably of the type disclosed in U. S. Pat. No. 2,523,990, in the name of Graham. As best seen in FIGS. 5 and 8 the heat exchanger 34 includes a manifold 38 having a fluid tight cover 40. The cover 40 includes therein a receiving port 42 and dis charge port 44, for the hydraulic fluid of the system 10, as well as a receiving port 46 and a discharge port 48, for the heat exchanger medium or coolant. A plurality of conduits 50 are positioned within the manifold 38 of the heat exchanger 34. The conduits 50 have opposite extremeties 52 and 54 extending through the aforementioned inlet and

outlet ports

46 and 48, respectively, for the heat exchanger medium. Each conduit 50 has the portion between the center and opposite ends formed into parallel, coaxial, symetrical spirals engaged throughout the spiral portions with one another in cooperative sealing engagement throughout the length of the spiral portions to form a spiral passage thereabout in the manifold 38. Hydraulic fluid passing through the manifold 38 surrounds the coils 50 carrying the heat exchanger medium and exits through the outlet port 44 leading to the discharge line 183.

It will, of course, be understood that the heat exchanger 34 provides for heat exchange between the hydraulic fluid in the system 10 and the heat exchanger medium or refrigerant, such as FREON and the like, whereby the hydraulic fluid is cooled within the desired temperature range and returned to the system 10. The heat exchanger medium or refrigerant utilized should preferably be non-toxic, non-flammable, and inert, and if possible compatible with the existing gases in the mine.

The heat exchanger medium exiting from the heat exchanger 34 proceeds through the heat exchanger medium outlet line 56, which may lead directly to the compressor 58, or to preferably a subcooler 60. The

explained hereinafter.

vaporized heat exchanger medium exiting either directly from the heat exchanger 34, or from the subcooler 60, proceeds through the conduit 56 to the compressor 58, where it is compressed and exits to the condenser 66. At this point, it should be noted that the hydraulic motor 26 operates both the compressor 58 and the fan '78 which pulls cool ambient air through and around the condenser 66. In operation, the heat exchange unit 24 will be utilized in underground mines where the temperature averages 56F. Accordingly, the cool mine air increases the efficieny of the heat exchange unit 24, primarily the condenser 66, and enables the components thereof to be smaller and more compact. For example, the size of the condenser 66 may be reduced by as much as 50 percent as compared with condensers operating under normal conditions.

As can be seen from the drawings, the hydraulic motor 26 is positioned axially between the condenser 66 and the fan 68, and the compressor 58. Suitable drive means 70 operatively connect the hydraulic motor 26 with the fan 68. Additionally, a coupling unit 72 connects the hydraulic motor 26 with the compressor 58. It should perhaps be emphasized that aligning the fan 68 with the hydraulic motor 26 and the compressor 58 eliminates the requirement for a pulley drive and the like, as well as external cooling means for the compressor, resulting in a substantial savings on space and cost.

Condensed heat exchanger medium from the condenser 66 proceeds through -a suitable conduit 74 (74A, 74B and 74C) either directly to the finned conduit 64 of the subcooler 60, or if a subcooler 60 is not utilized, directly to the inlet 46 ofthe heat exchanger 34, through the thermostatic expansion valve 82.

In practice, a sight glass 76, a filter dryer 78 and a receiver or dampener 80 are positioned in the conduit 74A. The sight glass 76, which is of conventional design, simply provides visual observation that the heat exchanger medium is properly flowing through the system. For example, conventional sight glasses generally include therein means which may be visually actuated by the heat exchanger medium. Such means will be green if the medium is flowing through the system, or red if the medium is not flowing through the system.

The dryer and filter 78 is also of conventional design and simply takes moisture, extraneous material, and acid forming materials out of the heat exchanger medium.

The receiver or dampener 80 is of the conventional type and its purpose is to cushion or dampen surges of heat exchanger medium in the heat exchange unit 24. In practice, the receiver or dampener 80 merely comprises a hollow chamber through which the heat exchanger medium passes. Additionally, the receiver or dampener 80 stores excess liquid heat exchanger mediurn and aids in the servicing of the heat exchange unit 24.

The temperature of the condensed heat exchanger medium entering the heat exchanger 34 must be regulated in order to provide satisfactory heat exchange between the hydraulic fluid and the heat exchanger medium so as to carefully regulate the temperature of the hydraulic fluid within the aforementioned desired temperature range. Briefly, this is accomplished by a combination of a thermostatic expansion valve 82 in the line 74 following the sight glass 76, the filter dryer 78, and the receiver 80, from the condenser 66 to the heat exchanger medium inlet 46 of the heat exchanger 34, and a load compensation valve 84 and associated bypass circuit 86, joining the high pressure compressor discharge line 65 between the compressor 58 and the condenser 66 with the line 74, following the thermostatic expansion valve 82.

While the means to control or regulate the temperature of the condensed heat exchanger medium entering the heat exchanger 34 may comprise only the thermostatic expansion valve 82, such as, for example, if the heat is constant, it has been found that best results are achieved when the means includes a combination of a thermostatic expansion valve 82 and the load compensation valve 84 and bypass circuit 86.

FIG. 9 discloses a cross sectional view through the thermostatic expansion valve 82. It will first, be understood that the purpose of the expansion valve 82 is to provide or furnish a set drop in pressure in the condensed heat exchanger medium in line 748, prior to its reaching the inlet port 46 of the heat exchanger 34, through line 74C. The purpose of such pressure drop is to control the degree of heat which the heatexchanger medium will remove from the hydraulic fluid in the heat exchanger. For example, the greater the pressure drop provided by the thermostatic expansion valve 82, the greater the quantity of heat the medium will remove from the hydraulic fluid in the heat exchanger 34. In general, the condensed heat exchanger medium in line 74B coming to the thermostatic expansion valve 82 is at a pressure of about 150 psi. The thermostatic expansion valve 82 reduces this pressure level to about 30 psi. However, the setting for the pressure dropmay be changed depending upon the demand upon the medium.

As can be seen from FIGS. 9 and 10 the thermostatic expansion valve 82 comprises a body 88 having an inlet 88a and an outlet 8811, a thermostatic element, which includes a control diaphragm 92 and a remote control bulb 94, including a capillary tube or suction line 95, push rods 96, seat 98, strainer 100, pin carrier 102 carrying pin 104, spring 106, including a spring guide 108, a bottom cap assembly 110, which includes an adjusting stem 112, and a sealed cap 114.

In operation, the push rods 96 carry the action of the diaphragm 92 to the pin 104. Tl-le control bulb 94 is located at the outlet of the heat exchanger 34 on the suction line 56. When the control bulb 94 warms, some of the heat exchanger medium or refrigerant in the bulb vaporizes and builds up pressure in the body 88 by means of the capillary tube connection 95, and the diaphragm 92 moves toward the body 88. This forces the pin 104 to move away from the seat 98 admitting the liquid heat exchanger medium or refrigerant into the heat exchanger or evaporator 34. This action continues until the whole coil 50 within the heat exchanger 34 is cooled, and the suction line 56 begins to cool. As soon as the suction line 56, to which the control bulb 94 is attached, becomes cooled sufficiently, the pressure in the bulb 96 decreases, due to condensation of its refrigerant. This reduces the pressure against the diaphragm 92. This action causes a movement of the diaphragm 92, and the expansion valve 82 is shut off, leaving the coil 50 of the heat exchanger 34 filled with heat exchanger medium or refrigerant vapor. The heat exchanger 34 now lowers or decreases the low side pressure, depending upon the heat load generated by the

machines

16 and 18. When the heat exchange unit 24 stops, the thermostatic expansion valve 82, if it were still open, would close because the low side pressure begins to build up. This clsoing action is important, because it precludes the flooding of the coil 50 in the heat exchanger 34 with liquid heat exchanger medium or refrigerant. The thermostatic expansion valve 82 is equipped with an adjustment stem 112. The adjustment stem 112 is designed to move the push rods 96 against the diaphragm 92. If the adjustment stem 1 12 is tunred out or counterclockwise, the push rods 96 will be moved away from the diaphragm 92. This action will starve the coil 50 of the heat exchanger 34 and result 8 in closing the pin 104 before the coil 50 becomes full of liquid exchanger medium or refrigerant. Turning the adjustment in or clockwise will increase the amount of liquid heat exchanger medium or refrigerant allowed to flow into the coil 50 of the heat exchanger 34.

As was previously explained, the means to regulate the temperature of the condensed heat exchanger medium or refrigerant entering the coils 50 of the heat exchanger 34 also preferably includes the load compensation valve 84 and the bypass circuit 86, which together allow for the introduction of compressed, vaporized heat exchanger medium or refrigerant into the conduit 74C. Under normal conditions, the load compensation valve 84 is closed and vaporized heat exchanger medium is precluded from passing through the bypass circuit 86 into the conduit 74C.

The load compensation valve 84 may best be seen in FIGS. 11 and 12. Control pressure from the external equalizer connection 116 senses the pressure at the suction side in the line 56 of the compressor 58. This pressure is transmitted through the passage 118 in the adpator 120 to the space 122 beneath the diaphragm l24,where it exerts its pressure against the diaphragm range spring 126, which is held within the spring bonnet 127 and against the diaphragm 124 by the cap 128. When the suction pressure drops below the value of the spring setting for the diaphragm range spring 126, the diaphragm 124 travels downward, moving the pilot plug 130 within the bore 132 in the adpater 120 in opening direction with respect to the pilot port 134. This allows the pressure in the space 136 above the piston 138 in the valve body 140 to be increased by vaporized heat exchanger medium or refrigerant flowing through the passage way 142 in the adapter 120. The increase in pressure will be exerted on the piston 138 and in turn the plug spring 144, which rests against the piston plug 146 of the bottom cap 138, opening the main port 150 and increasing the vaporized heat exchanger medium or refrigerant flowing through it, thereby correcting for the dropping control pressure sensed by the sensing means 116.

When the control pressure or suction pressure sensed by the sensing means 116 approaches and exceeds the 9 setting of the diaphragm range spring 126, the diaphragm 124 is moved upward, allowing the auxiliary plug spring 156 to move the pilot plug 130 in a closing direction with respect to the pilot port 134. This re-' duces the amount of vaporized heat exchanger medium or refrigerant flowing through the pilot port 134 and the passage way 142. With the pilot port 134 throttled, the pressure decreases on the top of the piston 138 in the 136, because of the bleed of the vaporized heat exchanger medium or refrigerant through the clearance around the piston 138. Accordingly, the plug spring 144 can move the piston 138 in a closing direction, reducing the flow of the vaporized heat exchanger medium or refrigerant through the main port 150, thereby correcting for the rising control pressure.

Turning now to FIGS. 3 through 6, it will be seen that the heat exchange unit 24 is conveniently assembled within a suitable frame 152, which includes a base plate 154 and suitable rubber mounts 156, which dampen vibration. Suitable cowling 158 or the like may be provided surrounding the fan 68. The hydraulic motor 26 is mounted on the base plate 154 by way of bolts 155. The shaft 27 of the motoris operable to rotate the fan 68. A coupling unit 72 operably connects the other end of the shaft 27 of the motor 26 with the compressor 58. The heat exchanger or evaporator 34 may be mounted by way of the bracket 160 to the frame 152, as shown in FIGS. 3 through 6. However, as shown in FIG. 7, the heat exchanger or evaporator 34 may also be mounted beneath the base plate 154, adjacent the subcooler 60, which is also mounted by way of suitable brackets 61 from the base plate 154.

A vent line 162 having a valve 163 is provided in association with the heat exchanger or evaporator 34. Accordingly, when the heat exchanger or evaporator 34 is charged from a source of heat exchanger medium or refrigerant, air in the hydraulic system may be bled from this vent line by opening the valve 163.

The heat exchange unit 24 may be provided with suitable relief valves. For example, the compressor 58 may have a compressor relief valve 164. A hot gas shut-off valve 166 as well as discharge and suction side service valves 168 and 170, respectively, may also be provided.

The heat exchange unit 24 of the present invention is also preferably provided with a suitable operating panel 172. This panel includes an indicator 174. This indicator, which senses the pressure in the line 56, is normally green. However, if the heat exchange unit is not functioning properly and the suction line pressure exceeds the design pressure for the heat exchange unit 24, the indicator will become red. Alternatively, a simple pressure gauge provided with red and green markings on the dial, both on the high and low side, could be used.

The panel also provides for the valve 163 leading to the vent line 162, as well as for a fluid thermometer 176, which registers the temperature of the hydraulic fluid being discharged from the heat exchange unit through the port 178 into the hydraulic system 10. The panel 172 also provides suitable connections 180 and 182 for receiving the bypass line 32 and the high pressure line 30, respectively.

It has also been found desirable to include suitable vibration dampers, such as the suction vibration damper 184 and the discharge vibration damper 186.

While certain preferred embodiments of the invention have been specifically illustrated and described, it

is understood that the invention is not limited thereto, as many variations will be apparent to those skilled in the art, and theinvention is to be given its broadest interpretation within the terms of the following claims.

I claim:

1. In an enclosed hydraulic system for operating hydraulic systems of machinery used in confined areas, such as coal mines and the like, where proximity to personnel and the danger of fire and explosion make it desirable that the hydraulic fluid be non-toxic and nonexplosive, of the type which includes an aqueous hydraulic fluid, a reservoir for said fluid, and at least one pump in connection with said reservoir and said machinery, the improvement, in combination therewith, which comprises a heat exchange unit to regulate the temperature of said hydraulic fluid at all times within said enclosed hydraulic system within the temperature range of 60 F,'said heat exchange unit comprising:

1 a. a hydraulic motor operable by at least a portion of said hydraulic fluid; b. a hydraulic motor speed control, including a first bypass conduit for hydraulic fluid not used to operate said hydraulic motor;

c..a heat exchanger in communication with said first bypass, motor, and reservoir which receives substantially all of said hydraulic fluid in said enclosed hydraulic system, said heat exchanger providing for heat exchange between said hydraulic fluid and a heat exchanger medium, whereby said hydraulic fluid is cooled within the desired temperature range and returned to said system;

. a source of heat exchanger medium for said heat exchange unit;

e. a compressor operable by said hydraulic motor and in communication with said heat exchanger, said compressor receiving said heat exchanger medium I as it exits from said heat exchanger in vaporized form, whereby said vaporized heat exchanger medium is compressed; I

f. a condenser including fan means operable by said motor to pull ambient air through and around said condenser, said condenser being in communication with said compressor and said heat exchanger for condensing said compressed, vaporized heat exchanger medium; and I ,g. means to regulate the temperature of said condensed heat exchanger medium entering said heat exchanger in order to provide satisfactory heat exchange between said hydraulic fluid and said heat exchanger medium so as to regulate the temperature of said hydraulic fluid within said desired temperature range.

2. The improvement according to claim 1, wherein said heat exchanger comprises a manifold having a fluid tight cover, the cover having a first receiving port and a first discharge port for the hydraulic fluid of the system and a second receiving port and a second discharge port for the heat exchanger medium, and a plurality of conduits positioned within said manifold, said conduits having opposite extremeties extending through said first receiving and discharge ports, each said conduit having the portion between the center and opposite ends formed intoparallel, coaxial, symetrical spirals engaged throughout the spiral portions with one another in cooperative sealing engagement throughout the length of the spiral portions to form a spiral passage thereabout in said manifold, whereby hydraulic fluid passing through said first receiving port into said manifold surrounds the spiral passage carrying the heat exchanger medium and is cooled prior to exiting from said second discharge port.

3. The improvement according to claim 1, wherein said hydraulic motor, condenser and compressor are in axial alignment with said motor being positioned between said condenser and said compressor.

4. The improvement according to claim 1, wherein a subcooler is in communication with the outlet of said condenser and the heat exchanger medium inlet of said heat exchanger, and between the heat exchanger medium outlet of said heat exchanger and the inlet of said compressor, said subcooler comprising a chamber having a conduit therethrough, said conduit receiving the condensed heat exchanger medium from said condenser and said vaporized heat exchanger medium from the heat exchanger medium outlet of said heat exchanger in said chamber surrounding said conduit, whereby condensed heat exchanger medium from said condenser is further cooled prior to its entrance into said heat exchanger.

5. The improvement according to claim 1, wherein said means to regulate the temperature of said condensed heat exchanger medium comprises controlling the speed of said hydraulic motor by said speed control in response to the temperature of said hydraulic fluid in said system.

6. The improvement according to claim 1, wherein said means to regulate the temperature of said condensed heat exchanger medium entering said heat exchanger comprises a thermostatic expansion valve which reduces the pressure level of said heat exchanger medium from said condesner prior to the introduction thereof to said heat exchanger, said thermostatic expansion valve including means associates therewith to sense the temperature of said vaporized heat exchanger medium as it exits from said heat exchanger and to vary said reduced pressure level in response to the temperature sensed.

7. The improvement according to calim 6, wherein said means to regulate the temperature of said condensed heat exchanger medium also inlcudes a load compensation valve and a second bypass circuit, said second bypass joining the vaporized heat exchanger medium discharged from said compressor with the flow of the heat exchanger medium through said thermostatic expansion valve, said load compensation valve being positioned in said second bypass circuit and being provided with means to sense the pressure of said vaporized heat exchanger medium at the inlet of said compressor, whereby said load compensation valve may be opened and closed, and thus the flow of compressed, vaporized heat exchanger medium through said second bypass circuit controlled, in response to said sensing means.

8. The improvement according to claim 3, wherein a dryer and filter is positioned in said heat exchange unit to receive the condensed, heat exchanger medium from said condenser and to extract the moisture, acid and foreign material therefrom.

9. The improvement according to claim 1, wherein a receiver and dampener comprising an elongated hollow chambered vessel is positioned to receive the condensed heat exchanger medium from said condenser so as to cushion, reduce, and dampen the surges of said heat exchanger medium in said heat exchanger unit and store excess liquid heat exchanger medium and aids in servicing of said heat exchange unit.

10. In a method of actuating enclosed hydraulic systems of machinery used in confined spaces such as coal mines and the like, wherein an aqueous non-flammable hydraulic fluid is supplied from a reservoir to hydraulic systems, circulated through said enclosed systems under pressure, and returned to said reservoir for use, the improvement which comprises:

a. providing a non-toxic aqueous hydraulic fluid having a good dispersant, extreme pressure, lubricity, corrosion inhibiting, and anti-foam properties, said fluid constituting a stable dispersion in water; and

b. regulating the temperature of said hydraulic fluid at all times within said enclosed hydraulic system within the temperature range of 60 F. by the steps of:

i. lowering the pressure of said hydraulic fluid to a desired level after it has passed through the hydraulic systems of said machinery;

ii. passing said hydraulic fluid at a lower pressure to a heat exchange unit;

iii. providing a heat exchanger within said heat exchange unit, said heat exchanger having heat exchanger medium continuously passing therethrough;

iv. directing said hydraulic fluid into heat exchange relation with said heat exchanger medium in said heat exchanger;

v. discharging said hydraulic fluid from said heat exchanger back into said hydraulic system; and

vi. regulating the temperature of said heat exchanger medium entering said heat exchanger in order to provide satisfactory heat exchange between said hydraulic fluid and said heat exchanger medium so as to continuously regulate the temperature of said hydraulic fluid within said desired-temperature range, in response to temperature changes in said hydraulic fluid resulting from fluctuation in heat load generated by said hydraulic machinery.

11. The method according to claim 10, wherein the temperature of said heat exchanger medium is regulated by sensing the temperature of said heat exchanger medium leaving said heat exchanger and varying the reduction of the pressure level of said heat exchanger medium in response to the temperature sensed prior to the introduction thereof into said heat exchanger.

12. The method according to claim 10, wherein the temperature of said heat exchanger medium is further regulated by introducing vaporized heat exchanger medium into said heat exchanger medium following the reduction of the pressure level thereof.

Claims

1. In an enclosed hydraulic system for operating hydraulic systems of machinery used in confined areas, such as coal mines and the like, where proximity to personnel and the danger of fire and explosion make it desirable that the hydraulic fluid be nontoxic and non-explosive, of the type which includes an aqueous hydraulic fluid, a reservoir for said fluid, and at least one pump in connection with said reservoir and said machinery, the improvement, in combination therewith, which comprises a heat exchange unit to regulate the temperature of said hydraulic fluid at all times within said enclosed hydraulic system within the temperature range of 60* - 90*F, said heat exchange unit comprising: a. a hydraulic motor operable by at least a portion of said hydraulic fluid; b. a hydraulic motor speed control, including a first bypass conduit for hydraulic fluid not used to operate said hydraulic motor; c. a heat exchanger in communication with said first bypass, motor, and reservoir which receives substantially all of said hydraulic fluid in said enclosed hydraulic system, said heat exchanger providing for heat exchange between said hydraulic fluid and a heat exchanger medium, whereby said hydraulic fluid is cooled within the desired temperature range and returned to said system; d. a source of heat exchanger medium for said heat exchange unit; e. a compressor operable by said hydraulic motor and in communication with said heat exchanger, said compressor receiving said heat exchanger medium as it exits from said heat exchanger in vaporized form, whereby said vaporized heat exchanger medium is compressed; f. a condenser including fan means operable by said motor to pull ambient air through and around said condenser, said condenser being in communication with said compressor and said heat exchanger for condensing said compressed, vaporized heat exchanger medium; and g. means to regulate the temperature of said condensed heat exchanger medium entering said heat exchanger in order to provide satisfactory heat exchange between said hydraulic fluid and said heat exchanger medium so as to regulate the temperature of said hydraulic fluid within said desired temperature range.

2. The improvement according to claim 1, wherein said heat exchanger comprises a manifold having a fluid tight cover, the cover having a first receiving port and a first discharge port for the hydraulic fluid of the system and a second receiving port and a second discharge port for the heat exchanger medium, and a plurality of conduits positioned within said manifold, said conduits having opposite extremeties extending through said first receiving and discharge ports, each said conduit having the portion between the center and opposite ends formed into parallel, coaxial, symetrical spirals engaged throughout the spiral portions with one another in cooperative sealing engagement throughout the length of the spiral portions to form a spiral passage thereabout in said manifold, whereby hydraulic fluid passing through said first receiving port into said manifold surrounds the spiral passage carrying the heat exchanger medium and is cooled prior to exiting from said second discharge port.

10. In a method of actuating enclosed hydraulic systems of machinery used in confined spaces such as coal mines and the like, wherein an aqueous non-flammable hydraulic fluid is supplied from a reservoir to hydraulic systems, circulated through said enclosed systems under pressure, and returned to said reservoir for use, the improvement which comprises: a. providing a non-toxic aqueous hydraulic fluid having a good dispersant, extreme pressure, lubricity, corrosion inhibiting, and anti-foam properties, said fluid constituting a stable dispersion in water; and b. regulating the temperature of said hydraulic fluid at all times within said enclosed hydraulic system within the temperature range of 60* - 90*F. by the steps of: i. lowering the pressure of said hydraulic fluid to a desired level after it has passed through the hydraulic systems of said machinery; ii. passing said hydraulic fluid at a lower pressure to a heat exchange unit; iii. providing a heat exchanger within said heat exchange unit, said heat exchanger having heat exchanger medium continuously passing therethrough; iv. directing said hydraulic fluid into heat exchange relation with said heat exchanger medium in said heat exchanger; v. discharging said hydraulic fluid from said heat exchanger back into said hydraulic system; and vi. regulating the temperature of said heat exchanger mediuM entering said heat exchanger in order to provide satisfactory heat exchange between said hydraulic fluid and said heat exchanger medium so as to continuously regulate the temperature of said hydraulic fluid within said desired temperature range, in response to temperature changes in said hydraulic fluid resulting from fluctuation in heat load generated by said hydraulic machinery.