US3033217A - Control apparatus and method for unloading compressors - Google Patents

Description

May 8, 1962 J. RAUFEISEN 3,033,217

CONTROL APPARATUS AND METHOD FOR UNLOADING COMPRESSORS Filed Feb. 16, 1959 2 Sheets-Sheet 1 4 g, 1 T0 CONDENSER [720M .Z'VAPDFA-TOR 2W0 LdBR C/ITION 5Y5 TEM lhzxaniar Jase OZ Eauf'esem. 2 I

May 8, 1962 .1. RAUFEISEN 3,033,217

CONTROL APPARATUS AND METHOD FOR UNLOADING COMPRESSORS Filed Feb. 16, 1959 2 Sheets-Sheet 2 J0s'90 Raufez'sew United States Patent 1 3,033,217 CONTROL APPARATUS AND METHOD FOR UNLGADING CGMPRESSORS Joseph Raufeisen, Palatine, Ill, assignor to Bell & Gossett Company, a corporation of Illinois Filed Feb. 16, 1959, Ser. No. 793,570 4 Claims. (Cl. 137-82) This invention is concerned with a variable capacity control for compressors and, more particularly, relates to a capacity control for multiple-cylinder compressors in which the control varies the loading of all of the cylinders simultaneously to maintain balanced relationships between cylinders.

In the preferred form, the capacity control system is automatically responsive to predetermined changes in the system load forvarying the compressor loading in corresponding predetermined increments.

In prior art unloading systems, a multiple-cylinder compressor is partially unloaded by completely disabling one of the cylinders, and this limits the selectivity and adjustment range of the load-regulation system while introducing dynamic unbalance into the compressor arrangement.

The principal object of the present invention is to provide an unloading system for a compressor wherein each cylinder is partially unloaded, with the unloading adjustment for each of the cylinders being accomplished simultaneously to maintain balanced loading relationships between cylinders.

Another object is to provide a compressor arrangement wherein a single control mechanism operates the unloader equipment for a plurality of cylinders simultaneously.

Still another object of the invention is to provide an arrangement wherein the unloader equipment is actuated through the medium of oil supplied under pressure from the compressors lubrication system, oil pressure being required to maintain the cylinders fully loaded, and since thereis no oil pressure when the compressor is at rest, the compressor starts at its unloaded condition.

Briefly, the unloading system in accordance with this invention accomplishes its loading or unloading functions, respectively, by covering or uncovering a fluid passage in the cylinder sleeve. When this fluid passage is uncovered, direct communication for the compressible fluid is established from the cylinder to the crankcase to disable the cylinder during the initial phase of the compression stroke and provide correspondingly reduced capacity.

In the simplified embodiment illustrated herein for purpose of disclosure, a one-step fifty percent capacity reduction is provided, though it is contemplated that a multiplestep unloading arrangement may be provided where desired by forming the cylinder with a number of fluid passages at lengthwise spaced points therealong. A multiple-position control valve mechanism would actuate the multiple-step unloading arrangement.

Other objects and advantages will become apparent during the course of the following description.

In the accompanying drawings forming a part of this specification and in which like numerals are employed to designate like parts throughout the same:

FIG. 1 is a fragmentary, semi-diagrammatic, side-elevational view, with parts broken away and sectioned, illustrating a multiple-cylinder compressor arrangement provided with unloading equipment in accordance with the present invention;

FIG. 2 is a diagrammatic cross-sectional view of one of the compressor cylinders illustrating the unloader equipment thereon and the control valve mechanism for the unloader equipment, with the cylinder being shown in condition for full-load operation; and

FIG. 3 is a view corresponding to that of FIG. 2 and illustrating the cylinder in condition for partially loaded operation.

Referring now to the drawings and more particularly to FIG. 1 thereof, the invention is illustrated in its application to a multiple-cylinder refrigeration compressor, though it will be apparent that the invention is also applicable to compressors having any number of cylinders and to related types of compressors.

In the arrangement shown, the numeral 10 designates a hollow compressor body having a crankshaft 11 rotatably mounted therein by any suitable bearing arrangement (not shown), with the crankshaft being adapted for connection to the output drive shaft of a motor (not shown). In the illustration, the compressor body 10 is broken away to disclose a pair of fluid compression assemblies 12, each of whichincludes a cylinder 13 and cylinder head 14, with a piston 15 being reciprocably movable through the cylinder to draw in, compress, and discharge a fluid charge. Each piston is connected to the crankshaft 11 by a suitable connecting rod 16.

As is indicated by the labeling of the external connection line arrangement, the compressor unit is adapted for use in an air-cooling system. The return line from the evaporator of such a system is shown at 17 entering into the crankcase chamber; and the discharge line to the condenser of such a system, as shown at 18, is brought through a cover plate 19 for the cylinder heads. Each cylinder head contains the usual intake and discharge valves, designated generally as 20 and 21, respectively,

with the intake valve controlling a supply passage 22 between the crankcase chamber and the upper end of each cylinder.

An unloader apparatus in accordance with this invention, as shown generally at 23, is applied to each of the cylinders, the unloader apparatus being controlled by oil pressure delivered from the compressors lubrication system over the line 24, pressure to this line being supplied through a control valve mechanism 25 that is responsive to changes in the crankcase pressure and correspondingly controls the condition of loading of the fluid compression assemblies 12. V

As is apparent, the compressor is provided with one control mechanism 25 for simultaneously actuating both unloader devices. All of this equipment is located totally within the crankcase body of the compressor, with the exception of a control mechanism adjustment which is brought through the compressor body for convenience of access. All control piping is internal, and no wiring is required.

The function of each unloader mechanism is to reduce the capacity of its cylinder upon demand from the control mechanism. In the preferred constructional embodiment of the invention, the unloader mechanism is integrated into the cylinder sleeve construction and, as is shown in FIGS. 2 and 3, the cylinder sleeve 13 carries an unloader body 27 rigid therewith and having a lengthwise projecting cylindrical wall section 27W cooperating with the cylinder in defining an annular groove that slidably receives an annular piston-like seal ring assembly 28 and an unloader piston 29 of tubular cylindrical form.

Each cylinder sleeve is provided with coplanar slots 138 that define passages opening between its compression chamber and the crankcase chamber, and the unloader piston 29 is slidable along the cylinder between an unblocldng position (FIG. 3) wherein the slots 133 are open and the fluid compression assembly is operating in a partially unloaded condition and a blocking position (FIG. 2) wherein the slots are masked and the fluid gompression assembly is operating in a fully loaded conition.

While these slots are open or uncovered, they aflord direct passage from the compression chamber of the 3 cylinder to the crankcase chamber of the compressor. During the initial travel of the piston on its compression stroke, the compressible fluid in the compression chamber escapes into the crankcase. After the piston passes the slots 138, the fluid remaining in the compression chamber is compressed and discharged into the line 18.

As indicated in FIG. 3, the unloader piston 29 is normally biased to its unblocking position by a spring assembly 30 that reacts between an integral shoulder 13H provided at the head end of the cylinder and an integral flange 29F provided on the base end of the unloader piston.

The unloader piston 29 is actuated to its blocking position whenever the pressure in the line 24 supplying oil to the base of the unloader body 27 is sufiicient to overcome the biasing action of the spring assemblies 36. To distribute the actuating pressure uniformly, the wall bordering the bottom end of the chamber for the unloader piston is formed with an annular groove 276. It will be noted that since the oil pressure in this line is supplied from the compressors lubrication system, there is no oil pressure when the compressor is starting and the unloader piston 29 is in the position in which it is shown in FIG. 3. Thus the compressor starts partially unloaded until oil pressure is built up and supplied to the unloading mechanism in accordance with the demands of the control mechanism.

In a. preferred constructional embodiment, the control mechanism senses crankcase pressures and controls the flow of oil to the unloading mechanisms for determining the proper loading of the cylinders. The control mechanism consists of a pressure-sensing assembly 32 operatively connected to actuate an oil control valve assembly 33. Both of these assemblies are mounted in separate chambers provided in a hollow casing 34 that includes an integral attachment flange 34F for anchoring the control mechanism to the crankcase body 19. A divider plate 34? separates the mounting chambers for these assemblies and is apertured as indicated at 34A to accommodate drainage from line 24. The pressuresensing assembly 32 comprises a bellows 35, an abutment plate 36 fixed to the movable end of the bellows, and a pressure spring 37 normally urging the bellows towards its extended position. The spring 37 is mounted in a cup-shaped seat 38 that is carried on an externally accessible adjustment screw 39 which is threadedly engaged in a suitable cover plate 40. A protective cap 39C is removably mounted over the outer end of the screw.

The bellows 35 defines an internal chamber that is open to the atmosphere through vent openings 41 provided in the cover plate 46. The mounting chamber for the bellows is exposed to pressure conditions in the crankcase of the compressor through vent openings 42 formed in the side walls of the casing 34. Thus, the bellows changes length to maintain a balance between the crankcase pressure and the combined effects of atmospheric pressure and spring pressure. The openings 42 also provide a passage for oil draining from line 24 through the apertures 34A.

Adjustment of the crankcase pressure to which the bellows responds is eilected by adjusting the screw 39. After the desired response pressure has been pre-set, any variation in crankcase pressure such as results upon a variation in the refrigeration load causes the bellows to expand or contract correspondingly and shift the abutment plate 36. For example, a reduction in crankcase pressure allows the bellows to expand.

The abutment plate engages and .actuates a set of positioning rods 43 that project through suitable guide bores extending lengthwise through the body of the casing. As will become apparent, these positioning rods 43 actuate the control valve assembly 33.

The oil control valve assembly 33 controls the supply of oil from the pressure lubrication system to both unloading mechanisms and thus provides balanced modulation between full load and reduced load operation. The body of the casing 34 forms a hydraulic cylinder for the control valve assembly 33 which includes a floating piston 45 for this cylinder. The piston is formed with interconnected annular grooves 46 that receive oil under pressure from the oil supply line 47. The bydraulic cylinder is bounded by a head plate 48 that is provided with a vent valve passage 49. A pin valve 50 is mounted on an apertured carrier plate 51 that floats in a chambered end cap 52 for the casing under the control of a pressure spring 53. The cap is vented to the crankcase at 54.

The head end of the floating piston 45 has a bevelled edge to form a permanent oil chamber, and the oil supply line 47 communicates with this chamber through the grooves 46 and an orifice 56 provided in the floating piston. Finally, a spring 57 is located in the hydraulic cylinder and normally biases the floating piston against the head plate 48 (See FIG. 3) to block flow of oil from the line 47 to the line 24.

The operation of the control mechanism will now be evident. As shown in FIG. 3, when the crankcase pressure rises sufficiently that reduced capacity operation is called for, the bellows 35 contracts and the spring 53 holds the valve pin 56 in position to block the vent passage of the head plate 48. The head chamber now fills with oil through the annular grooves 46 and orifice 56 in the floating piston 45 and the oil pressure builds up in the cylinder and forces the floating piston towards the divider plate 34? against the force of the spring 57. Oil now flows from the supply line 47 through the annular grooves 46 and out the line 24 to the unloader mechanisms. The unloader piston 29 moves along the cylinder to block the fluid passages defined by the slots 138. The fluid compression assemblies then operate at full capacity.

When the crankcase pressure is sufficiently low that full-load operation is called for, the bellows will expand and, through the abutment plate 36, will drive the positioning rods 43 against the carrier plate 51 against the action of the spring 53 to vent the head chamber and allow the spring 57 to return the floating piston 45 to its original blocking position (See FIG. 3) wherein it interrupts flow of oil from line 47 to line 24. Oil then drains from the unloader mechanisms, back through the line 24 and out apertures 34A and holes 42 to permit the springs 30 to return the unloader pistons 29.

From the foregoing description, it will be apparent that the loading condition is determined by the location of the cylinder slots 138 along the length of the compression chamber of the cylinder 13. Furthermore, the cylinders 13 are operated in balanced relationship. Another advantage of the invention is that the compressor starts at reduced loading.

The specific embodiment illustrated herein for purposes of disclosure is the preferred arrangement at present, though it is contemplated that many variations in detail may be made without departing from the scope of the inventive concept. It will be apparent that a multiple-step unloading arrangement may readily be achieved by providing additional slots at points spaced lengthwise along the cylinder, and suitable control mechanisms for multiple-step arrangements of this character will be .apparent to those skilled in the art. The openings in the cylinder for effecting the unloading may obviously be round holes or of other shape.

It should be understood that the description of the preferred form of the invention is for the purpose of complying with Section 112, Title 35, of the U.S. Code and that the claims should be construed as broadly as prior art will permit.

I claim:

1. A control mechanism for supplying lubricant from a source of lubricant under pressure to a point of use in response to changes in a reference pressure and comprising a hollow casing forming a pressure-sensing chamber and a valve chamber having an inlet for connection to the source of lubricant and an outlet for connection to the point of use, said valve chamber having a vent passage, a vent valve in said vent passage, and means normally urging said vent valve into blocking position in said vent passage, a valve body having one end thereof exposed to lubricant in said valve chamber for shifting movement between an unblocking position wherein said inlet and outlet are in communication and a blocking position wherein said inlet and outlet are isolated, means biasing said valve body to its blocking position, said valve body forming a passage for maintaining said inlet and said vent passage in communication such that when said vent passage is open lubricant normally flows through said inlet and out said vent passage and when said vent valve closes said vent passage, lubricant forces said valve body to its unblocking position, and a pressure-sensing mechanism in said pressure-sensing chamber and connected to position said vent valve in response to changes in said reference pressure.

2. A control mechanism for regulating the supply of fludi from a source of fluid under pressure to a point of use in response to changes in a reference pressure and comprising casing structure providing separate pressure sensing and valve chambers, said valve chamber having a vent passage at one end thereof and having an inlet for connection to said source and an outlet for connection to said point of use, a vent cap on said one end of said valve chamber and spanning said vent passage, a carrier plate movable in said cap and carrying a vent valve for said vent passage, and means for resiliently biasing said carrier plate to a blocking position in which said vent valve is seated in said vent passage,'a valve body in said valve chamber for shifting movement between a blocking position wherein said inlet and outlet are in communication and an unblocking position wherein said outlet is isolated, said valve .body having one end only thereof exposed to fluid entering said inlet to develop pressure thereon tending to move said valve body towards its unblocking position, resilient means for biasing said valve body to its blocking position, said valve body. having a passageway for maintaining said inlet and said vent passage in communication such that when said vent valve unblocks said vent passage fluid normally flows through said inlet and out said vent passage and when said vent valve blocks said vent passage fluid builds up pressure against said exposed end of said valve body sulficient to overcome said resilient means and force said valve body to its unblocking position, a pressure sensing mechanism in said pressure sensing chamber and including movable in response to changes in said reference pressure and engageable with said carrier plate to position said vent valve in response to changes in said reference pressure.

3. A control mechanism for regulating the supply of fluid from a source of fluid under pressure to a point of use in response to changes in a reference pressure and comprising a casing body providing a pressure sensing chamber at one end and a valve chamber at its opposite end, said valve chamber constituting a hydraulic cylinder having a vent passage at one end of said casing body and having a side entrance inlet for connection to said source and a side entrance outlet for connection to said point of use, a piston like valve body having one end in sealingly slidable relation in said cylinder and having its opposite end exposed to fluid entering said inlet, said valve body being mounted in said cylinder for shifting movement between an unblocking position wherein said inlet and outlet are in communication and a blocking position wherein said inlet and outlet are isolated, said valve body providing a passageway for maintaining said inlet in communication with said vent passage, a vent valve in said vent passage, means normally urging said vent valve into blocking position in said vent passage and mechanism in said pressure sensing chamber movable in response to changes in said reference pressure and connected to said vent valve to control the position thereof such that when said vent valve unblocks said vent passage fluid flows through said inlet and out said vent passage but when said vent valve blocks said vent passage fluid pressure acts on the exposed end of said piston-like valve body to force the same to its unblocking position.

4. A' control mechanism for regulating the supply of fluid from a source of fluid under pressure to a point of use in response to changes in a reference pressure and comprising a casing body providing a pressure sensing chamber at one end .and a valve chamber at its opposite end, said valve chamber constituting a hydraulic cylinder having a vent passage at one end of said casing body and having a side entrance inlet for connection to said source and a side entrance outlet for connection to said point of use, a piston like valve body having one end in sealingly slidable relation in said cylinder and having its opposite end exposed to fluid entering said inlet, said valve body being mounted in said cylinder for shifting movement between an unblocking position wherein said inlet and outlet are in communication and a blocking position wherein said inlet and outlet are isolated, said valve body providing a passageway for maintaining said inlet in communication with said vent passage, a vent cap on said one end of said casing body and spanning said vent passage, a carrier plate movable in said cap and carrying a vent valve for said vent passage, means for resiliently biasing said carrier plate to a position in which said vent valve is seated in said vent passage, a pressure responsive bellows in said pressure sensing chamher and changeable in length in reponse to changes in said reference pressure, and means including compression members projecting through said casing body to transmit movement from said bellows to said carrier plate to position said vent valve in response to changes in said reference pressure such that when said vent valve unblocks said vent passage fluid flows through said inlet and out said vent passage but when said vent valve blocks said vent passage fluid pressure acts on the exposed end of said piston-like valve body to force the same to its unblocking position.

References Cited in the file of this patent UNITED STATES PATENTS 2,274,337 Ritter Feb. 24, 1942 2,275,303 Mantle Mar. 3, 1942 2,345,547 Roth et al Mar. 28, 1944 2,366,146 Martin-Hurst Dec. 26, 1944 2,524,444- Ifield Oct. 3, 1950 2,555,004 Rinehart May 29, 1951 2,555,005 Warneke May 29, 1951 2,646,814 Mueller July 28, 1953 2,668,415 Lawrence Feb. 9, 1954 2,673,025 Labus et a1. Mar. 23, 1954 2,753,882 Bottoms July 10, 1956 2,836,345 Gerteis May 27, 1958 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,033,217 May 8, 1962 Joseph Raufeisen It is hereby certified that error appeers in the above numbered patent requiring co and that the said Letters Patefitt-should read as corrected below. Q

Column 5, line zs, for "fludi" after "includi read fl id line, 51

insert means Signed and sealed this 4th day of September 1962.

(SEAL) Y- Attest:

ERNEST w. SWIDER DAVID L LADD Attesting Officer Commissioner of Patents

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