US3545220A - Capacity controlled refrigeration system - Google Patents

Description

Dec. 1970 F.TEEGARDEN CAPACITY CONTROLLED REFRIGERATION SYSTEM Fi1ed No v. 29, 1968 2 Sheets-Sheet 1 INVENTOR. ARLO ETEEG ARDEN ATTORNEY United States Patent Oifice 3,545,220 CAPACITY CONTROLLED REFRIGERATION SYSTEM Arlo F. Teegarden, Onalaska, Wis., assignor to The Trane Company, La Crosse, Wis., a corporation of Wisconsin Filed Nov. 29, 1968, Ser. No. 779,867

Int. Cl. F25h 41/00 U.S. Cl. 62-196 Claims ABSTRACT OF THE DISCLOSURE A refrigeration system involving a multi-cylinder reciprocal refrigerant compressor provided with means for bypass unloading of the refrigerant discharged from at least one of the compressor cylinders to the suction side of the compressor including a pilot operated bypass value driven to the open and closed positions by refrigerant discharge from the cylinder unloaded and including dashpot means for delaying movement of the pilot valve.

This invention relates to bypass capacity control for compression type refrigeration systems.

In refrigeration systems of the compression type it is often desirable to increase or decrease the capacity of the system such as to correspond to the refrigeration load as by passing compressed refrigerant from a portion of the discharge of the compression means back to the suction side of the compression means. This may be accomplished by placement of a valve in a bypass line which extends from the discharge s de of a part of the compression means to the suction side of the compression means. By opening the valve, compressed refrigerant gas from part of the compression means flows directly to the suction without passing through the condenser, expansion means and evaporator thereby reducing the refrigerating eifect of the system. Many such bypass unloader systems have been'developed. The instant invention affords certain advantages and is characterized by certain difierences particularly in the manner in which the valve in the bypass line is actuated by gas pressures within the refrigeration system.

A principal object of this invention is to provide a refrigerant compressor with a bypass unloader valve powered by refrigerant gas discharged from the cylinder to be unloaded thereby eliminating the possibility of a high to low side leak when the compressor is unloaded. Upon first consideration a high to low side leak would not appear to be detrimental as during this time much of the gas is being bypassed to suction. However, it must be appreciated that such bypass gas is not first raised to discharge pressure; whereas any gas used to operate the bypass valve which is derived from the discharge side at discharge pressure which leaks to suction, will first have undergone considerable compression and heating. Such leakage gas from the high pressure side of the compressor increases the horsepower requirement of the compressor and also tends to heat up the suction gas. Where this suction gas is used to cool the motor, such a high to low side leak is detrimental to the motor cooling ability of the system. By deriving the gas to Operate the bypass unloader valve from the unloaded cylinder, these undesirable results of a high to low side leak within the unloader mechanism are eliminated.

Thus it is an object to provide a refrigeration system with a more eflicient bypass unloader capacity control.

It is a further object of this invention to provide a refrigeration system with a bypass type capacity control which does not adversely affect the temperature of the suction gas.

It is still a further object to provide a refrigeration system with a pilot operated bypass unloader valve having a dashpot delay mechanism for the pilot valve thereof whereby hunting of the bypass valve is avoided.

It is another object of this invention to provide a refrigeration system compressor bypass unloader valve with a time delay means which may be simply and easily altered in duration.

And it is still a further object of this invention to provide a refrigeration system bypass unloader mechanism which utilizes a number of standard low cost parts.

And yet another object of this invention is to provide a refrigeration system bypass unloader mechanism in which the bypass valve is driven to the open position by the gas discharged from the cylinder which is unloaded by such bypass valve.

It is another object of this invention to provide a refrigeration system compressor bypass unloader mechanism in which gas discharge from the unloading cylinder or cylinders is used to power the bypass valve to both the open and closed positions.

It is another object of this invention to provide a refrigeration system compressor bypass unloader mechanism in'accordance with the above mentioned objects which is controlled in response to suction pressure, that is the pressure in the low side of the refrigeration system.

Other objects and advantages will become apparent as this specification proceeds to describe the invention with reference to the accompanying drawing wherein like elements have been identified by like reference numerals in which:

FIG. 1 is a diagrammatic view of a refrigeration system incorporating the invention including a portion of the compression means therefor;

FIG. 2 is a sectional view of the bypass unloader mechanism incorporating the instant invention.

Referring now to FIG. 1, there is shown a refrigeration system 10 having a refrigerant condenser 12, a refrigerant expansion means 14, a refrigerant evaporator 16, and a refrigerant compression means 18 respectively serially connected in a closed refrigerant circuit.

Compression means 18 has a first compression cylinder 20 and a second compression cylinder 22 having pistons 24 and 26 respectively mounted therein and arranged to be reciprocated by crankshaft 28 via connecting rods 30. Compressor 18 has a valve plate 32 mounted at the end of compression cylinders 20 and 22 for admitting and discharging refrigerant to and from cylinders 20 and 22. Suction ports 34 and discharge ports 36 are disposed in plate 32 and communicate with first cylinder 20. Suetion ports 38 and discharge ports 4'0 are disposed in plate 32 and communicate with second. cylinder 22. Suction ports 34 and 38 are each provided with an annular resilient suction valve 42 and discharge ports 36 and 40 are each provided with an annular resilient discharge valve 44. Valve-s 44 are provided with a stop member 45 to limit their open position.

Now with reference to FIGS. 1 and 2 it will be seen that a cylinder head 46 which may be bolted to the cylinders as by bolts 48 is disposed on the side of the valve plate opposite cylinders 20 and 22. Cylinder head 46 includes a suction chamber 50 which forms part of a suction passageway 51 extending from the outlet of evaporator 16 to the suction ports 34 and 38. The cylinder head 46 has a first cylinder discharge chamber 52 and a second cylinder discharge chamber 54 communicating respectively with discharge ports 36 and 40 for receiving refrigerant compressed in cylinders: 20 and 22. Chamber 52 forms part of a first discharge passageway 56 extend- Patented Dec. 8, 1970 v 3 check valve 60 arranged to permit flow in passage 58- only in a direction away from chamber 54 toward passage 56.

Chamber 54 also communicates with bypass passageway 62, defined by cylinder head 46, which extends to suction passageway 51 for bypassing refrigerant gas from discharge chamber 54 to suction chamber 50. A bypass unloader valve means 64 is provided for passageway 62 for controlling the flow of refrigerant gas therethrough.

Unloader valve means 64 includes an annular valve seat 66 through which passageway 62 extends and a valve 68 arranged on the upstream side of seat 66 in cooperative relationship therewith. Seat 66 may have external threads (not shown) for sealingly securing it in passageway 62. Valve 68 is mounted at one end of valve stem 70 for guiding valve 68 to and from the face of seat 66.

Adjacent the other end of valve 70 is a cylindrical chamber 74 defined by cylinder head 46. Chamber 74 has a movable partition 76 therein dividing chamber 74 into a first portion 78 and a second portion 80. Partition 76 preferably is a piston slidably mounted for reciprocal movement along the axis of cylindrical chamber 74. Valve stem 70 slidably extends through a bore 82 in a wall defining the second portion 80 of chamber 74. Valve stem 70 and cylindrical chamber 74 are of such length and arranged in such proximity so that movement of piston 76 toward the second portion 80 of chamber 74 causes piston 76 to bear upon the end of valve stem 70' and move valve 68 to the open position. Movement of piston 76 towards the first portion 78 of cylindrical chamber 74 Will permit valve 68 to close. It will be seen that piston 76 is not directly attached to valve stem 70 whereby some misalignment of cylindrical chamber 74 and bore 82 is permissible.

The movement of valve 68 and piston 76 is controlled by the fluid pressures on these elements. When bypass valve 68 is closed, it will be seen that compressor discharge pressure is exerted on one side thereof and compressor suction pressure is exerted on the other side. The net pressure under such condition-s will maintain valve 68 in a closed position. If valve 68 is in the open position the pressure differential across valve 68 is substantially reduced. However, it has been found that the net pressure on valve 68 and stem 70 is suflicient to cause valve 68 to move to the closed position. Referring now to the pressures exerted on piston 76, it will be seen that the pressure on the side of piston 76 adjacent valve stem 70 is maintained at suction pressure as second portion 80 of chamber 74 is in direct fluid communication with suction passageway 51 by way of bore 84 and that portion of bypass passageway 62 downstream of valve 68. Thus the side of piston 76 adjacent stem 70 is always maintained at suction pressure. The pressure on the other side of piston 76 is controlled in response to suction pressure as will hereinafter be described.

For purposes of controlling the pressure within first portion 78 of chamber 74 bypass unloader valve means 64 has been provided with a pilot valve and damper body 76 connected at one end as by bolts (not shown) to the cylinder head adjacent first portion 78 of chamber 74. A pilot valve actuator body 88 is mounted at the other end of pilot valve and damper body 86 as by bolts (not shown). Disposed between pilot valve and damper body 86 and cylinder head 46 is a fluid distributor plate 90. It will be appreciated that appropriate gaskets are provided between cylinder head 46 and distributor plate 90, between distributor plate 90 and pilot valve and damper body 86, and between pilot valve and damper body 86 and pilot valve actuator 88. Elements 88, 86 and 90 could, of course, be made integral with cylinder head 46 if desired with additional cost and difficulty.

It will be seen from FIG. 2 that a first passageway 92 extends from a point in passageway 62 upstream of bypass valve 68 through a bore 94 in fluid distributor plate 90, through a pair of bores 96 to a pilot valve chamber 98 in pilot valve and damper body 86. Passageway 92 continues on through pilot valve actuator body 88 by way of a central bore 11, first lateral bore 13, second lateral bore 15 and bore 17 to bore 19 extending to passage 21 in fluid distributor plate 90. Passage 21 provide-s fluid communication only between bore 19 and first portion 78 of chamber 74. Central bore 11 is provided with a flange or pilot valve seat 23. A pilot valve 25 is disposed within pilot valve chamber 98 and positioned to cooperate with valve seat 23 for closure of passageway 92.

Pilot valve and damper body 86 has a large cylindrical bore 27 or chamber extending therein from the end adjacent plate 90. A dashpot partition or piston 29 which may be provided with an O-ring seal 31 is sealingly and slidably received within bore 27. Piston 29 is connected to pilot valve 25 by way of shaft 33 and bolt 35. Shaft 33 extends through a bore 37 connecting pilot valve chamber 98 and bore 27. Bore 37 is made only sufliciently larger than shaft 33 to permit a small amount of gas leakage from pilot valve chamber 98 to bore 27. Dashpot piston 29 is biased in a direction tending to close valve 25 by compression spring 39 interposed between plate and the side of piston 29 remote from shaft 33. The space of bore 27 on the spring side of piston 29 is in open communication with passageway 92 by way of passage 41. The space of bore 27 on the side of piston 29 adjacent shaft 33, in addition to leakage communication with pilot valve chamber 98, communicates with an accumulator portion of pilot valve damper body 86 provided with a cavity 43.

Removably connected to the accumulator portion of pilot valve and damper body 86 in fluid communication with cavity 43 is a secondary accumulator 47 having a cavity 99 therein. Thus it will be seen that both cavity 43 and cavity 99 are in fluid communication with that portion of bore 27 adjacent shaft 33.

Pilot valve actuator body 88 has a large bore 49 therein. Bore 49 is disposed in fluid communication with suction passageway 51 by way of passageway 53 extending through pilot valve actuator body 88, and pilot valve and damper body 86 and cylinder head 46 to a point in bypass passageway 62 downstream of bypass valve '68. A bellows actuator 55 disposed within bore 49 is sealingly fixed at one end thereof to actuator body 88. The movable end of bellows 55 is sealingly closed by plate 57. A push rod 59 fixed to plate 57 extends through a bore 61 into bore 11 at the downstream side of pilot valve 25. The interior of bellows 55 is vented to the atmosphere. Disposed within bellows 55 is an adjustably mounted compression spring 63 which biases plate 57 and thus push rod 59 in a direction tending to open valve 25. Push rod 59 is of such length that sufficient movement in this direction will cause valve 25 to open. The pressure within bore 49, i.e. suction pressure, works against the bias of spring 63 to contract bellows 55 thereby permitting valve 25 to close. The pressure at which level valve 25 is opened or closed may be adjusted as by adjustment screw 60.

The operation of the refrigeration system is as follows. Let it be assumed that compressor 18 is operating and compressed refrigerant is passing serially through condenser 12, expansion means 14, and evaporator 16 back to compressor 18. As the load at evaporator 16 is met the temperature and pressure within the evaporator and thus the pressure in suction passageway 51 begins to fall. This pressure is reflected on bellows 55 as by passageway 53 and the cavity of bore 49. As the pressure on bellows 55 is reduced bellows 55 is further extended under the bias of spring 63 thereby moving plate 57 and thus push rod 61 into engagement with valve 25 to open valve 25. This movement is delayed by the dashpot effect of piston 29 directly connected to valve 25. The length of this delay will depend upon the volume of bore 27, cavity 43 and cavity 99. In due time sufficient gas from pilot valve chamber 98 will pass through bore 37 into the aforementioned cavities 43 and 49 to exert suificient pressure on piston 29 to permit valve 25 to be opened. The opening of valve 25 permits gas to flow freely through passageway 92 to a first portion 78 of cylindrical chamber 74. The pressure within first portion 78 of chamber 74 exerted on piston 76 causes piston 76 to move toward the second portion 80 of cylindrical chamber 74 thereby moving valve stem 70 and thus valve 68 to the open position. The gas discharge from the second cylinder will thus flow freely through bypass passageway 62 to the suction side of the compressor.

Upon opening of valve 68, the pressure in passageway 92, and thus the pressure on the spring side of dashpot piston 29, is substantially reduced thereby tending to hold the dashpot piston in a position holding pilot valve 25 open to prevent immediate reclosing of the bypass valve 68 despite a temporary rise in suction pressure caused by opening of valve 68.

Should the refrigeration load on evaporator 16 increase thereby causing an increase in temperature and pressure within the evaporator and an increaseof pressure within suction passageway 51, passageway 53, and the interior of bore 49, bellows 55 will be forced to contract thereby permitting valve 25 to be closed via the bias of spring 39. However, once again the movement of valve 25 will be delayed by the dashpot effect of piston 29. In due course the pressure within cavities 99 and 43 will be relieved by leakage of gas from bore 27 through bore 37 to pilot valve chamber 98. Closure of valve 25 terminates the flow of gas by way of passageway 92 to the first portion 78 of chamber 74. The pressure within the first portion 78 of chamber 74 is relieved by leakage around piston 76 to the second portion 80 of chamber 74 and thus to the suction side of the compressor by way of bore 84. The pressures on opposite sides of piston 76 thus are equalized whereby piston 76 will no longer hold valve 68 in the open position. Valve '68 is then closed under the influence of the gas passing through bypass passageway 62. Upon closure of valve 68, gas discharged from the second cylinder passes through second discharge passageway 58 and check valve 60 to join the gas discharged from the first cylinder passing in the first discharge passageway 56 toward condenser 12.

Also upon closure of valve 68, the pressure in passage way 92 and thus the pressure on the spring side of dashpot piston 29 is raised to discharge pressure thereby tending to hold the dashpot piston in a position holding pilot valve 25 closed to prevent immediate reopening of the bypass valve 68 despite a temporary drop in suction pressure caused by closing of valve 68.

It will be appreciated that upon either opening or closing of valve 68 the pressure within the suction passageway 51, passageway 53 and bore 49 will fluctuate. :This would have a hunting effect upon the unloader mechanism if it were not for the delay effect of the aforementioned dashpot mechanism. The length of time delay associated with this dashpot mechanism may be adjusted for various installations and operating conditions by the removal of accumulator 47 or the replacement of accumulator 47 with a larger accumulator. The shafts, rods, and pistons which I have utilized in my unloader mechanism may all be manufactured by way of high production facilities thereby permitting the mechanism to be produced with a minimum of cost. If desired my unloader mechanism by removal of plug 100 may be connected to a number of slave bypass unloader valves as by way of a pressure line connected to second lateral bore 15. In such case the opening and closing of pilot valve 25 will aifect the opening and closing of a number of bypass valves comparable to valve 68.

Although I have described in detail the preferred embodiment of my invention, I contemplate that many changes may be made without departing from the scope or spirit of my invention and I accordingly desire to be limited only by the claims.

I claim:

1. A refrigeration system comprising: a refrigerant compressor means, a refrigerant condenser, a refrigerant thottling means and a refrigerant evaporator connected respectively in series; said compressor means including first and second compression cylinders each including a movable piston therein; each of said cylinders having associated therewith a suction port and a discharge port provided respectively with a suction valve and a discharge valve; a suction passageway extending to said suction ports from said evaporator; a first discharge passageaway extending from the discharge port of said first cylinder to said condenser; a second discharge passageaway extending from the discharge port of said second cylinder and communicating with said first discharge passageway; a check valve means disposed in said second discharge passageway for substantially limiting flow therethrough to a flow direction away from said discharge port of said second cylinder; a bypass passageway extending from a point in said second discharge passageway upstream of said check valve means to said suction passageway; a bypass unloader valve means for controlling the flow of fluid in said bypass passageway from said discharge port of said second cylinder through said bypass passageway to said suction passageway; said bypass unloader valve means including a valve seat and a bypass valve disposed on the upstream side of said seat in cooperative relationship with said seat and having open and closed positions; means forming a chamber; a mov able partition traversing said chamber; first conduit means extending from a first side of said partition to a point in said second discharge passageway upstream of said check valve means for exerting a force on said first side of said partition; means for transmitting said force on said first side of said partition to said bypass valve for biasing said bypass valve toward an open position; and pilot valve means for controlling the flow in said first conduit means.

2. The apparatus as defined by claim 1 including a second conduit means extending from a second side of said partition to said suction passageway.

3. The apparatus as defined by claim 2 wherein said chamber is a cylinder and said partition is a piston slidably disposed within said cylinder.

4. The apparatus as defined by claim 1 including means for actuating said pilot valve means in response to pressure in said suction passageway.

5. The apparatus as defined by claim 1 including actuator means for actuating said pilot valve means; and means for delaying movement of said pilot valve means.

-6. A refrigeration system comprising: a refrigerant compressor means, a refrigerant condenser, a refrigerant thottling means and a refrigerant evaporator connected respectively in series; said compressor means including first and second compression cylinders each including a movable piston therein; each of said cylinders having associated therewith a suction port and a discharge port provided respectively with a suction valve and a discharge valve; a suction passageway extending to said suction ports from said evaporator; a first discharge passageway extending from the discharge port of said first cylinder to said condenser; a second discharge passageway extending from the discharge port of said second cylinder and communicating with said first discharge passageway; a check valve means disposed in said second discharge passageway for substantially limiting flow therethrough to a flow direction away from said discharge port of said second cylinder; a bypass passageway extending from a point in said second discharge passageway upstream of said check valve means to said suction passageway; a bypass unloader valve means for controlling the flow of fluid in said bypass passageway from said discharge port of said second cylinder through said bypass passageway to said suction passage-way; said bypass unloader valve means including a valve seat, and a bypass valve disposed in cooperative relationship with said seat and having open and closed positions; means forming a first chamber; a first movable partition traversing said first chamber; first conduit means extending from one of said first and second discharge passageways to said suction passageway for exerting a force on one side of said partition; means for transmitting said force on said one side of said partition to said bypass valve for biasing said bypass valve toward one of said positions; a pilot valve for controlling the flow of fluid in said first conduit means; actuator means for actuating said pilot valve; and dashpot means for delaying movement of said pilot valve for preventing hunting of said bypass valve.

7. The appartus as defined by claim 6 wherein said dashpot means exerts a force on said pilot valve for retarding movement of said pilot valve.

8. The apparatus as defined by claim 6 wherein said dashpot means includes means defining a dashpot chamber; a movable dashpot partition traversing said dashpot chamber; second conduit means extending from one side of said dashpot partition to a point in said second discharge passageway upstream of said check valve means for exerting a variable force on said one side of said dashpot partition of a magnitude generally proportional to the variable pressure upstream of said bypass valve resulting from opening or closing of said bypass valve; and means for transmitting said force on said one side of said dashpot partition to said pilot valve thereby affecting delayed but rapid movement of said dashpot partition and pilot valve.

9. The apparatus as defined by claim 8 wherein said first conduit means extends to a point in said second discharge passageway upstream of said check valve means.

10. The apparatus as defined by claim 6 further including means defining a first fluid accumulator in communication with said dashpot means; means defining a second fluid accumulator in fluid communication with said first fluid accumulator; and means for disconnecting said second fluid accumulator from said first fluid accumulator to thereby change the delay time of said dashpot means.

References Cited UNITED STATES PATENTS 3,360,952 1/1968 Lewis 62-196 MEYER PElKLIN, Primary Examiner

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