US2671605A

US2671605A - Unloader and overload protector for rotary compressors

Info

Publication number: US2671605A
Application number: US112787A
Authority: US
Inventors: Victor J Grumblatt
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1949-08-27
Filing date: 1949-08-27
Publication date: 1954-03-09
Anticipated expiration: 1971-03-09

Description

M r 9, 1954 v. J. GRUMBLATT UNLOADER AND OVERLOAD PROTECTOR FOR ROTARY COMPRESSORS Filed Aug. 27, 1949 Inventor- F ww w J. m m m H V9 .D

Patented Mar. 9, 1954 UNLOADER AND OVERLOAD PROTECTGR FOR ROTARY COMPRESSORS Victor J. Grumblatt, East Cleveland, Ohio, assignor to General Electric Company, a corporation of New York Application August 27, 1949, Serial No. 112,787

12 Claims. 1

My invention relates to compressors and more particularly to rotary compressors.

In the operation of compressors it is frequently desirable to make provision for unloading, particularly during the starting operation in order to reduce the load on the motor used for driving the compressor. Such unloading may be accomplished, for example, by providing free communication between the inlet and discharge ports of the compressor. Similarly, it may be desirable to provide such communication during the subsequent operation of the compressor in the event an overload should occur for any reason. By my invention I have provided a simple arrangement which facilitates unloading of a compressor and also protects'the motor against undesirable overloads.

It is an object of my invention to provide an improved unloading arrangement for a rotary compressor.

It is another object of my invention to provide an improved overload protector for a rotary compressor.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

In carrying out the objects of my invention, I provide an arrangement for automatically moving the blade of the rotary compressor out of engagement with the rotor during all or a portion of each revolution of the rotor in response to the load on the driving motor. Alternatively, only one part of a multi-part blade may be moved to reduce the load. More specifically, the position of the blade or the movable part of the blade is controlled by a solenoid whose energization is dependent on the load on the motor.

For a better understanding of my invention reference may be had to the accompanying drawing in which Fig. 1 is a schematic diagram illustrating an embodiment of my invention; Fig. 2 is a view of a portion of the apparatus of Fig. 1 under different conditions; Fig. 3 is a schematic diagram illustrating a modified form of my invention; Fig. 4 shows another modified form of my invention; Fig. 5 is a view similar to Fig. 4 illustrating the position of the parts under different conditions; Fig. 6 shows another modified form of my invention; and Fig. 7 is a view similar to Fig. 6 illustrating the position of the parts under'different conditions.

Referring to -Fig. 1, there is shown a rotary compre'ssoriwhich is driven by an electric motor 2. The electric motor includes a starting winding 3 and a running winding 4. Power is supplied to these windings from any suitable power source through lines 5, 6.

The rotary compressor includes a housing 1 within which a rotor t is eccentrically mounted and is driven by the motor 2. The rotor 8 rotates within a chamber S provided within the housing I of the compressor. The compressor includes an inlet port ill and a discharge port ll both of which are in communication with the chamber d. Fluid pumped by the compressor is supplied to the inlet port [0 through a conduit l2 and is discharged from the discharge port ll through a conduit [3.

In order to block communication between the inlet and discharge ports in and H during the normal operation of the compressor 'a conventional blade I is slidably received within the housing '5 and engages the periphery l5 of the rotor. The blade It is biased into engagement with the periphery it of the rotor by a compression spring It, one end of which bears against a stationary stop I? and the other end of which bears against a shoulder 18 of the blade I l.

The arrangement thus far described involves a conventional rotary compressor structure in which, as the rotor 8 is rotated in the direction indicated by the arrow, fluid is taken in through the inlet port it, is moved through the chamber 9, and is discharged through the discharge port ll. However, when compressors are employed, for example, in refrigerating systems there may be a substantial difference in pressure between the low, or inlet side, and the high or discharge side, particularly during the starting operation, and this imposes a heavy load on the driving motor 2. In order to reduce this load until the motor has had an opportunity to come up to speed and is able to assume the load, I have provided an arrangement for automatically withdrawing the blade Hi from engagement with the periphery l5 of the rotor 8. It can be seen that moving the blade out of engagement with the rotor permits free communication between the inlet port and the discharge port through the chamber 9 and hence substantially eliminate the pumping load on the motor 2. To accomplish this purpose a solenoid i9 is provided about a portion 29 of the blade i l. The solenoid I9 is connected in a circuit 21 in series with the starting winding 3. In a conventional arrangement a switch is arranged in series with the starting winding, the switch being arranged to interrupt the starting winding circuit after the motor has come up to speed. The operation of the switch may be based on the speed of the motor, the current through the starting winding, etc. Such a switch has been shown at 22 in this figure but it will become apparent that, insofar as the operation of the solenoid I9 is concerned, the switch 22 could be omitted and a closed circuit utilized.

During normal operation the current through the winding 3 and the solenoid l9, even should the switch 22 be omitted, is sufliciently low that any biasing force exerted by the solenoid I9 is exceeded by the opposing bias of the spring I6, and the blade I4 is maintained in engagement with the periphery I5 of the rotor 8. However, during the starting operation a much heavier current flows through the windings of the motor 2 and hence through the solenoid I9, which is arranged in series with the starting winding 3 of the motor. Under these circumstances the force exerted by the solenoid I9 on the armature portion of the blade I4 exceeds the force exerted by the spring and the blade is moved out of engagement with the rotor to the position shown in Fig. 2, wherein the upper end of the blade I4 engages the stop II and the lower end of the blade I4 is moved out of the chamber 9 and is positioned Within the housing I. This allows communication through the chamber 9 between the ports I0 and I I and hence efiects an unloading of the compressor. As the motor comes up to speed the current through the windings decreases and hence the current through the solenoid I9 correspondingly decreases, and the blade I4 is again moved into engagement with the rotor 8 by the spring I5, instituting normal operation of the compressor. The motor, having come up to speed, is readily able to assume the necessary pumping load.

The operation of the device in the case of an overload occurring during the regular operation of the compressor is the same as that involved in the unloading operation just described. Should an overload occur for any reason the resultant increase in current through the motor windings is reflected in the energization of the solenoid I9 and the movement of the blade I 4 out of engagement with the rotor. This substantially reduces the pumping load on the motor and minimizes the danger of overload damage to the motor.

The modified form shown in Fig. 3 differs from that described above only in that the solenoid I9 is arranged in series with the running winding 4 in lieu of the starting winding 3. The same numerals have been used to designate corresponding parts. During the starting operation there is a heavier current through the running winding 4 than durin the normal operation of the compressor and hence a larger energizing current through the solenoid I 9. The resultant energization of the solenoid I9 is effective through the armature 20 to move the blade I4 out of engagement with th periphery I5 of the rotor, un-

loading the compressor in the same manner as previously described. Similarly, should an overload occur, the increased current through the winding 4 is also reflected in increased current through the solenoid I9 and the blade I4 is moved out of engagement with the rotor 8 by the solenoid I9.

In Figs. 4 and 5 there is illustrated a modified form of my invention in which the blade is only partially withdrawn from the chamber 9 so as to remain out of engagement with the rotor during only a portion of each revolution. The same numerals have been used to designate corresponding parts in Figs. 1, 2, and 3 and in Figs. 4 and 5. Referring to Figs. 4 and 5 there is shown the rotary compressor I including the housing 1 providing the chamber 9 within which the eccentrically-mounted rotor 8 rotates. Inlet and discharge ports I0 and II, respectively, are illustrated. A blade 23 extends through the housing I and is biased toward engagement with the periphery I5 of the rotor 8 by a spring 24. During normal operation of the compressor the blade is compressed into engagement with the periphery I5 of the rotor during the entire revolution of the rotor. In order to provide for shifting the blade under certain conditions, for example, to unload the compressor, a solenoid I9 is utilized, this solenoid being connected in series with the starting winding 3 or running winding 4 as lllustrated in Figs. 1 and 3. The solenoid I9 controls the position of an armature 25 which i arranged to engage a portion 26 of the blade 23. In the position shown in Fig. 4, which corresponds to the normal operating condition of the compressor, the armature 25 is biased downwardly against a stop 21 by a spring 28 and the engaging portion of the armature is spaced slightly below the portion 26 of the blade 23 so as not to interfere with the movement of the blade under the influence of the rotor 8 and the spring 24. During starting of the motor or during overload conditions the current through the starting or running winding and hence through the solenoid I9 increases substantially. Under these conditions the solenoid I9 moves the armature 25 to the position shown in Fig. 5 wherein a portion 29 of the armature engages the stop I! and the armature engages the portion 28 of the blade 23 and moves the blade upwardly to the position shown in Fig. 5. The stop I! and the spacing between the stop and the portion 29 of the armature 25 during normal operating conditions are arranged so that the maximum travel of the armature moves the tip or end 30 of the blade 23 only partially out of the chamber 9 of the compressor. Thus, in the position of the rotor 8 shown in Fig. 5 the blade 23 is held out of engagement with the rotor. However, it can be seen that during a portion of each revolution of the rotor the periphery I5 of the rotor will engage the tip 30 of the blade 23 and during this portion of each revolution refrigerant is pumped by the compressor in the normal manner. When the motor has come up to speed during the starting operation or when an overload occurring for any other reason has passed, the energization of the solenoid I9 is reduced and the armature 25 returns to the position shown in Fig. 4, allowing normal movement of the blade 23 and normal operation of the compressor.

In Figs. 6 and 7 there is shown another modified form of my invention which employs a two-part blade in which one part of the blade remains in engagement with the rotor at all times. The same numerals have been used to designate corresponding parts in Figs. 6 and 7 and in the preceding figures. Referring to Fig. 6 wherein the position of the parts is illustrated for normal operation of the compressor there is shown a blade 3I extending through the housing I between the inlet port I9 and the discharge port II. The blade 3I is made of two relatively

movable parts

32 and 33. The part 32 is pressed into engagement with the periphery of the rotor 8 by a spring 34 in a conventional manner. One end of the spring 34 engages a stop 35 and the other end presses against an end 35 of the blade part 32. A recess 31 is provided in one side of the part 32 of the blade and the part 32 of the blade is arranged to slide within this recess. The position of the blade part 33 is controlled by the solenoid I9 which is arranged in series with the starting winding or the running winding of the motor as illustrated in Figs. 1 and 3. The blade part 33 is normally pressed downwardly against a shoul- 5 der 38 on the blade part 32 by a spring 39 which engages the stop I! and an armature portion 40 of the blade part 33.

A transverse passage 4| is provided in the blade part 32 for permitting communication between the ports l and l I under certain conditions of operation. Under normal conditions, as illustrated in Fig. 6, the slight energization of the solenoid i9 is overbalanced by the force exerted by the spring 39 and the blade part 33 is held in engagement with the shoulder 38, blocking the passage 4|. Under these conditions the blade 3i acts in the same manner as a. solid one-piece blade of a conventional compressor and fluid is pumped by the compressor in the conventional manner. Under starting conditions or under other conditionswherein an excessive load is imposed on the motor the increase current through the solenoid l9 moves the armature 4i! and the blade part 33 upwardly beyond the end 42 of the passage il, as illustrated in Fig. '7. It can be seen that, in this position of the blade part 33, the passage 4| provides for communication through the blade between the inlet port ill and the discharge port H, unloading the compressor. When the rotor 8 has turned sufficiently to move the blade upwardly to a point where the shoulder 38 and the lower edge 43 of the passage 4| are just within the housing 1 communication through the passage M is blocked by the housing itself and hence the compressor operates to pump fluid in the normal manner during this portion of each revolution. In this respect the modified form shown in Figs. 6 and 7 operates in a manner similar to the form shown in Figs. 4 and wherein, even under unloading conditions, the compressor is effective to pump fluid during a portion of each revolution.

While I have shown and described specific embodiments of my invention, I do not desire my invention to be limited to the particular constructions shown and described, and I intend, by the appended claims, to cover all modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a rotary compressor and an electric motor for driving said compressor, said compressor including a housing having a chamber therein and a rotor eccentricall'y-mounted within said chamber, said housing including spaced inlet and discharge ports, a blade extending through said housing between said ports, said blade being normally biased into engagement with said rotor, and electromagnetic means connected in series with said motor for positively moving at least a portion of said blade in a direction away from said rotor to provide communication between said inlet and said discharge ports for unloading said compressor during at least a portion of each revolution of said rotor in response to a predetermined maximum current supplied to said motor.

2. In combination, a rotary compressor and an electric motor for driving said compressor, said compressor including a housing having a chamber therein and a rotor eccentrically-mounted within said chamber, said housing including spaced inlet and discharge ports, a blade extending through said housing between said ports, saidblade being normally biased into engagement with said rotor, and electromagnetic means connected in series with said motor for positively moving said blade away from said rotor to provide communication between said inlet and said discharge ports for unloading asid compressor in response to a predetermined maximum current supplied to said motor.

3. In combination, a rotary compressor and an electric motor for driving said compressor, said compressor including a housing having a chamber therein and a rotor eccentrically-mounted within said chamber, said housing including spaced inlet and discharge ports, a blade extending through said housing between said ports, said blade being normally biased into engagement with said rotor, a solenoid having an armature arranged for movement in the direction of movement of said blade for positively moving at least a portion of said blade in a direction away from said rotor to provide communication between said inlet and said discharge ports for unloading said compressor during at least a portion of each revolution of said rotor, and means dependent on the load on said motor for energizing said solenoid to move at least said portion of said blade out of engagement with said rotor.

4. In combination, a rotary compressor and an electric motor for driving said compressor, said compressor including a housing having a chamber therein and a rotor eocentrically-mounted within said chamber, said housing including spaced inlet and discharge ports, a blade extending through said housing between said ports, said blade being normally biased into engagement with said rotor, a solenoid having an armature arranged for movement in the direction of movement of said blade for positively moving said blade away from said rotor to provide communication between said inlet and said discharge ports for unloading said compressor during at least a portion of each revolution of said rotor, and means dependent on the load on said motor for energizing said solenoid to move said blade out of engagement with said rotor.

5. In combination, a rotary compressor and an electric motor for driving said compressor, said compressor including a housing having a chamber therein and. a. rotor eccentrically-mounted within said chamber, said housing including spaced inlet and discharge ports, a blade extending through said housing between said ports, said blade being normally biased into engagement with said rotor, a solenoid having an armature arranged for movement in the direction of movement of said blade for positively moving said blade away from said rotor to provide communication between said inlet and said discharge ports for unloading said. compressor, and means dependent on the load on said motor for energizing said solenoid to move said blade out of engagement with said rotor.

6. In combination, a rotary compressor and an electric motor for driving said compressor, said compressor including a housing having a chamber therein and a rotor eccentrically-mounted within said chamber, said housing including spaced. inlet and discharge ports, a blade extending through said housing. between said ports, said blade including two relatively movable parts, one of said parts of said blade being biased into engagement with said rotor, said one of said parts of said blade having a passage therein for providing communication between said inlet port and said discharge port, the other of said parts of said blade being normally biased to one position to block communication through said passage, a solenoid for shifting said other of said parts of said blade to a second position out of blocking relationship with said passage to provide communication between said inlet port and said dischargeport for unloading said compressor during at least a portion of each revolution of said rotor, and means dependent on the load on said motor for energizing said solenoid to move said other of said parts of said blade to its second position.

7. In combination, a rotary compressor and an electric motor for driving said compressor, said compressor including a housing having a chamber therein and a rotor eccentrically-mounted within said chamber, said housing including spaced inlet and discharge ports, a blade extending through said housing between said ports, said blade being normally biased into engagement with said rotor, and a solenoid for positively moving at least a portion of said blade in a direction away from said rotor to provide communication between said inlet and discharge ports for unloading said compressor during at least a portion of each revolution of said rotor, said solenoid being connected in series with said motor whereby energization of said solenoid is dependent on current flow to said motor.

8. In combination, a rotary compressor and an electric motor for driving said compressor, said motor including a starting winding and a running winding, said compressor including a housing having a chamber therein and a rotor eccentrically-mounted within said chamber, said housing including spaced inlet and discharge ports, a blade extending through said housing between said ports, said blade being normally biased into engagement with said rotor, and a solenoid for positively moving at least a portion of said blade in a direction away from said rotor to provide communication between said inlet and discharge ports for unloading said compressor during at least a portion of each revolution of said rotor, said solenoid being connected in series with one of said windings of said motor whereby energization of said solenoid is dependent on current flow through said one of said windings.

9. In combination, a rotary compressor and an electric motor for driving said compressor, said compressor including a housing having a chamber therein and a rotor eccentrically-mounted within said chamber, said housing including spaced inlet and discharge ports, a blade extending through said housing between said ports, a spring for biasing said blade into engagement with said rotor, a solenoid having an armature arranged for movement in the direction of movement of said blade for positively moving said blade away from said rotor in opposition to said spring to provide communication between said inlet and discharge ports for unloading said compressor, and means dependent on a load condition of said motor for energizing said solenoid to move said blade out of engagement with said rotor.

10. In combination, a rotary compressor and an electric motor for driving said compressor, said compressor including a housing having a chamber therein and a rotor eccentrically-mounted within said chamber, said housing including spaced inlet and discharge ports, a blade extending through said housing between said ports, a spring for biasing one end of said blade into said chamber and into engagement with said rotor, a solenoid having an armature arranged for movement in the direction of movement of said blade for positively moving said blade away from said rotor and out of said chamber to provide communication between said inlet and discharge ports for unloading said compressor, and means dependent on a load condition of said motor for energizing said solenoid to move said blade.

11. In combination, a rotary compressor and an electric motor for driving said compressor, said compressor including a housing having a chamber therein and a rotor eccentrically-mounted within said chamber, said housing including spaced inlet and discharge ports, a blade extending through said housing between said ports, a spring for biasing one end of said blade into said chamber and into engagement with said rotor, a solenoid having an armature arranged for movement in the direction of movement of said blade for positively moving said blade away from said rotor to provide communication between said inlet port and said discharge port for unloading said compressor, means dependent on a load condition of said motor for energizing said solenoid, and means for limiting the movement of said blade away from said rotor so that said one end of said blade rejects into said chamber when said solenoid is energized whereby said rotor engages said blade during a portion of each revolution to effect normal pumping action during said portion of each revolution.

12. In combination, a rotary compressor and an electric motor for driving said compressor, said compressor including a housing having a chamber therein and a rotor eccentrically-mounted within said chamber, said housing including spaced inlet and discharge ports, a blade extending through said housing between said ports, said blade including two relatively movable parts, a spring for biasing one end of one of said parts of said blade into said chamber and into engagement with said rotor, said one of said parts having a passage therein for providing communication between said inlet port and said discharge port, a spring for biasing the other of said parts of said blade normaly to one position to block communication through said passage, a solenoid for shifting said other of said parts of said blade to a second position out of blocking relationship with said passage to provide communication between said inlet port and said discharge port for unloading said compressor, and means dependent on a load condition of said motor for energizing said solenoid to move said other of said parts of said blade to its second position, said passage being spaced from said one end of said one part of said blade a distance such that said passage portion of said one part of said blade is moved out of said chamber into said housing during a portion of each revolution of said rotor whereby communication between said inlet port and said discharge port through said passage is blocked by said housing during said portion of each revolution of said rotor regardless of the position of said other part of said blade.

VICTOR J. GRUMBLATT.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 974,913 Von Pittler Nov. 8, 1910 1,912,463 Ploeger June 6, 1933 2,007,388 Tarleton July 9, 1935 2,020,987 Ayres Nov. 12, 1935 2,069,767 McCormack Feb. 9, 1937 2,458,018 Murphy Jan. 4, 1949 2,488,942 Schweller Nov. 22, 1949 FOREIGN PATENTS Number Country Date 209,715 Switzerland Aug. 1, 1950