US3125285A - Safety device for refrigeration compressors - Google Patents

Description

March 17, 1964 N. E. B. LARSSON SAFETY DEVICE FOR REFRIGERATION COMPRESSORS Filed May 15. 1961 INVENTOR. W31: 57% 6P7 a Lama United States Patent 3,125,285 SAFETY DEVIQE FOR REFREGERATEON COMPRESSORS Nils Erik Birger Larsson, Finspang, Sweden, assignor to Sta] Refrigeration Aktieholag, Norrkoping, Sweden, a

Swedish corporation Filed May 15, 1961, Ser. No. 110,176 3 Claims. (Cl. 230-230) The invention relates to refrigeration compressors, and more particularly to means by which such devices are prevented from damage due to surge.

There is the possibility in refrigeration compressors, and especially in those of the high speed type, that fluid refrigerant may be forced from the evaporator into the cylinder by a surge and in such case the quantity of fluid may burst the cylinder or disc, unless some sort of a protective means is employed. Surge is likely to occur upon starting up, when excessive boiling occurs in the refrigerator. It is known that the disc may be provided with a spring-loaded device which allows it to lift from the valve seat and permit an increased flow to the compressor pressure chamber. However, such a safeguard is not always completely satisfactory.

The present invention relates to compressors of the type provided with a spring-loaded valve disc and it is an object of the invention to make such compressors safer and more reliable in the event of surge. The invention is characterized by the fact that the valve disc is divided into two spring-loaded parts movable relatively to one another and to the compressor cylinder head and which, at a surge the return plate having pressure val es, such valves can open into the pressure chamber, allowing refrigerant to pass from the cylinder, while the other springloaded part can open into the compression suction chamber, permitting a return flow to the cylinder. Since the capacity of the first cylinder stroke to move the refrigerant is thus reduced, excessive boiling in the evaporator is also reduced and a dangerous quantity of fluid refrigerant in the compressor is avoided.

With these and other objects to be hereinafter set forth in view, I have devised the arrangement of parts to be described and more particularly pointed out in the claims appended hereto.

The invention is illustrated in the accompanying drawings, in which the figures there shown represent sectional views taken through the cylinder axis, showing the upper portion of the compressor. FIGURE 1 shows the valve disc in its normal operating position, while FIGURE 2 shows the position of the valve disc during surge.

Referring to the drawings, 1 indicates the wall of the cylinder and 2 indicates the piston movable in the usual manner within the cylinder. The valve disc, which is generally indicated at 4, is positioned in an opening in the cylinder wall and it is interposed between the top of the piston 2 and the pressure chamber 14. The disc 4 is composed of two main parts, one of which is indicated at 4a, and the other being indicated at 5, these parts having limited movement relatively to one another. The part 5 constitutes a return plate for pressure valves 6 which are interposed between the plate 5 and an apertured head 12 fastened to the part 4a by the central bolt 16. Openings 7 are provided through the plate 5 for the passage of refrigerant.

The part 4a is in the form of a spider having an outer ring 17 connected by spokes 18 to the central hub 19. A coil spring 9 is positioned between the compressor cylinder head 8 and the hub 19 of the disc 4 which spring normally urges the disc to its seated position. The disc 4 is movable away from seated position, as shown in FIGURE 2 and to the extent permitted by the stop ring inserted in the opening in the cylinder wall in which 3,125,285 Patented Mar. 17, 1964 ice the disc is located. A spring shown at 11 is mounted between the return plate 5 and the hub portion 19 of the disc 4 which spring keeps the return plate 5 urged against the head 12 on the part 4. i

Normally, the refrigerant is forced by the piston 2 through the openings 13 in the head 12 and past the pressure valves 6 and through the openings 7 in the plate 5 and into the compressor pressure chamber 14. However, when a surge occurs, the return plate 5 will be lifted so that the refrigerant can enter the pressure chamber 14. At about the same time, the whole disc 4- will be elevated against the biasing force of the spring 9 and to the extent permitted by the stop ring 10, so that an opening establishing communication between the pressure chamber 4 and the suction chamber will be the result. A return flow of fiuid and gas passes through such opening, and this immediately reduces the capacity of the compressor. Compressor capacity reduction thus reduces excessive boiling in the evaporator and the compressor is relieved of any extreme stresses caused by a surge.

A further and important advantage of the present construction is that by dividing the movable mass of the valve disc in the manner herein described there is an increase in the mechanical strength, since the impact force occasioned by the return of the disc is reduced, due to the fact that the return is spread out over a certain period of time.

Having thus described a single embodiment of the invention, it is obvious that the same is not to be restricted thereto, but is broad enough to cover all structures coming within the scope of the annexed claims.

What I claim is:

1. A safety device for refrigeration compressors comprising, a cylinder including a piston chamber, a pressure chamber and a suction chamber, a seat in the cylinder, a disc movable to and from the seat having a lower end for seating against the seat, spring means for urging the disc toward the seat, said disc having a head carried by it and having its perimeter spaced inwardly of the lower end of the disc and thus defining an annular spacing between its perimeter and the lower part of the disc, which spacing establishes communication between the pressure chamber and the piston chamber, a plate movably mounted on the disc, said plate being apertured, spring means for urging the plate toward the head, the head being apertured, pressure valves arranged between the head and plate and effective to close the apertures in the head when the plate is urged toward the head and also effective at that time to close the spacing between the perimeter of the head and the lower end of the disc, the disc when raised from its seat by refrigerant surge being effective to establish communication between the pressure chamber and the suction chamber, while raising of the plate relatively to the head also by said surge opens the annular spacing between the head and the disc and thus, establishes communication between the piston chamber and the pressure chamber.

2. A safety device for refrigeration compressors comprising, a cylinder having a piston chamber, a pressure chamber and a suction chamber, a piston movable in the piston chamber, a movable disc interposed between the piston chamber and the pressure chamber, a seat in the cylinder for receiving the movable disc, the disc having an apertured head carried by it at one end, which head defines an annular spacing between its perimeter and a part of the disc, the disc including a spider at its end remote from the head, a spring operative against the spider to seat the disc, a plate encircling the disc between the spider and head, said plate being of a diameter to cause it to close the annular spacing, said plate having apertures extending through it, pressure valves interposed between the plate and the head, said valves being effective to close the apertures through the head and to also close the annular spacing when the disc is seated and the plate is urged toward the head, and spring means interposed between the'plate and the spider and acting to bias the plate toward the head, the plate and disc when elevated by refrigerant surge serving to respectively es tablish communication between the pressure chamber and the suction chamber and between the piston chamber and the suction chamber.

3. A safety device for refrigeration compressors comprising, a cylinder having a pressure chamber and a suction chamber, a piston movable in the cylinder toward the pressure chamber, a spring-loaded disc disposed between the top of the piston and the pressure chamber, a seat in the cylinder toward and against which the disc is urged by its spring, said disc including an apertured head carried by it free of contact with the seat, a plate carried by the disc above the head, said plate carrying pressure valves interposed between it and the head and effective to closes the apertures in the head when the plate is urged toward the head, the head and a part of the disc defining an aperture between them which is also closed by the pressure valves when the plate is urged toward the head, the plate having apertures communicating with those in the head when the plate member is urged away from the head by refrigerant surge, which surge will also move the disc from its seat to establish communication between the pressure chamber and the suction chamber, and spring means for normally urging the plate member toward the head.

References Cited in the file of this patent UNITED STATES PATENTS 839,331 Stevens Dec. 25, 1906 1,475,826 Hoffman Nov. 27, 1923 1,907,478 Sutton et a1 Mar. 14, 1933 FOREIGN PATENTS 317,179 Great Britain Mar. 20, 1929 50,679 Netherlands Apr. 25, 1938

Claims (1)

1. A SAFETY DEVICE FOR REFRIGERATION COMPRESSORS COMPRISING, A CYLINDER INCLUDING A PISTON CHAMBER, A PRESSURE CHAMBER AND A SUCTION CHAMBER, A SEAT IN THE CYLINDER, A DISC MOVABLE TO AND FROM THE SEAT HAVING A LOWER END FOR SEATING AGAINST THE SEAT, SPRING MEANS FOR URGING THE DISC TOWARD THE SEAT, SAID DISC HAVING A HEAD CARRIED BY IT AND HAVING ITS PERIMETER SPACED INWARDLY OF THE LOWER END OF THE DISC AND THUS DEFINING AN ANNULAR SPACING BETWEEN ITS PERIMETER AND THE LOWER PART OF THE DISC, WHICH SPACING ESTABLISHES COMMUNICATION BETWEEN THE PRESSURE CHAMBER AND THE PISTON CHAMBER, A PLATE MOVABLY MOUNTED ON THE DISC, SAID PLATE BEING APERTURED, SPRING MEANS FOR URGING THE PLATE TOWARD THE HEAD, THE HEAD BEING APERTURED, PRESSURE VALVES ARRANGED BETWEEN THE HEAD AND PLATE AND EFFECTIVE TO CLOSE THE APERTURES IN THE HEAD WHEN THE PLATE IS URGED TOWARD THE HEAD AND ALSO EFFECTIVE AT THAT TIME TO CLOSE THE SPACING BETWEEN THE PERIMETER OF THE HEAD AND THE LOWER END OF THE DISC, THE DISC WHEN RAISED FROM ITS SEAT BY REFRIGERANT SURGE BEING EFFECTIVE TO ESTABLISH COMMUNICATION BETWEEN THE PRESSURE CHAMBER AND THE SUCTION CHAMBER, WHILE RAISING OF THE PLATE RELATIVELY TO THE HEAD ALSO BY SAID SURGE OPENS THE ANNULAR SPACING BETWEEN THE HEAD AND THE DISC AND THUS, ESTABLISHES COMMUNICATION BETWEEN THE PISTON CHAMBER AND THE PRESSURE CHAMBER.

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