US 3704964 A
A hermetic refrigeration compressor of the low-side type is provided with an improved, low-cost low-side or intake muffler having tubular inlets particularly effective for eliminating noise frequencies of 100 cycles per second and up.
Description (OCR text may contain errors)
United States Patent Phelps Dec. 5, 1972  HERMETIC REFRIGERATION  References Cited COMPRESSOR UNITED STATES PATENTS  Invent Wuisvme, 3,387,774 6/1968 Gannaway et al ..417/312 As ignee: General Company 3,504,762 Valbjorn Gt 3| ..4 l l 2  Filed: 1971 Primary Examiner-Robert M. Walker 21 APPL 170 113 Attorney-Walter E. Rule et al.
 ABSTRACT  U.S. Cl. ..417/312, 417/415, 417/902 I  Int. CLMFMb 21/00, F04b 39/00 F04b 17mm A hermetic refrigeration compressor of the low-side F04b 35/00 type is provided with an improved, low-cost low-side  or intake muffler having tubular inlets particularly ef- Field of Search ..4l7/312, 415, 902
fective for eliminating noise frequencies of 100 cycles per second and up.
4 Claims, 3 Drawing Figures P'ATENTEDHEB 1912 3.704.964
INVEENTOR DOLPHUS H. PHELPS F I BY X \K 5 ATTORNEY 1 I-IERMETIC REFRIGERATION COMPRESSOR BACKGROUND OF THE INVENTION The present invention relates particularly to fractional horsepower hermetic refrigerant compressors of the low side type, that is of the type in which the hermetic casing is filled with refrigerant gas at suction pressures.
Compressors of this type are generally employed in household refrigerators. Many of them operateat 3600 RPM, this high speed operation presenting noise problems of a different nature from those encountered in the older and slower speed compressors. In a reciprocating compressor, the valves controlling the flow of gas to and from the compressor cylinder and the pulsating movement of the gas to and from the cylinder due to theoperation of the valves normally requires both intake and exhaust mufflers to dampen the pulses and thereby avoid resonance of other parts of the system such as the compressor case.
The intake gas flow system of a reciprocating compressor is a transient, compressable flow system. While the equations that describe the dynamics of such a system, that is the so-called Navier-Stokes equations, are known, these equations arexnonlinear, partial differential equations and have not been solved for the general case even with high speed computers. Accordingly in the absence of a good analytical tool, the compressor designeris forced to search almostblindly for a configuration which will provide a good balance between compression noise, refrigeratingpcapacity and cost. In other words a muffler providing the desired balance of these characteristics for one type of compressor may not besuitabl e for another.
The present invention is an improvement on a Scotch-yoke type compressor of the general structure disclosed in. US. Pat-No. 2,836,349 Scheldorf, which comprises a compressor cylinder, a hollow piston reciprocating within the cylinder and means for admitting gas to be compressed into the piston and through an intake or suction valve in the head. of the piston into the cylinder.
SUMMARY OF THE INVENTION More specifically, the present invention relates to a compressor comprising a cylinder, a hollow reciprocating piston in the cylinder and means comprising cooperating or registering openings in the side walls of the cylinder and the piston for admitting gas to the piston. Valve means in. the head or top wall of the piston are provided for admitting suction gas from the piston into the cylinder during the suction stroke of the piston. The compressor includes a bowl-shaped muffler having its bottom wall ridgedly mounted on the side wall of the cylinder overlying the opening in. the cylinder side wall. Suction gas is admitted to the cylinder through a cooperating opening in the muffler bottom wall. The muffler also has a top wall including a a spaced gas inlet in the form' of tubes extending inwardly from the top wall on diametrically opposite sides of the center of the top wall, the inner ends of these tubes being spaced a short distance from the bottom wall of the muffler and being offset from the muffler bottom wall opening.
2. BRIEF DESCRIPTION OF THE DRAWING DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to the accompanying drawing, there is illustrated a hermetic refrigeration compressor comprising a: case 1 containing a motor unit 2 and a compressor unit 3 mounted on one end wall of the motor unit- The compressor unit3 comprisesa cylinder 5 and a hollow piston 6 reciprocally arranged within the cylinder 5. T he motorunit 2 is connected through: a drive shaft 7 and an eccentric 8to the piston 6.:
As shown in FIG. 2 of the drawing, the piston. 6 is hollow and includes a top wall or ahead portion 9provided with a plurality of the intake or suction gas passages 10 served by an intake valve 11 for controlling the flow of low pressure gas from the interior of the casing 1 to the interior of the cylinder 5.: The compressed refrigerant is discharged from the cylinder 5' through discharge passages 12 served by a discharge valve l4 to a discharge conduit 15.
The piston 6 receiveslow pressure refrigerant gas through a hole 16 provided in one wall of the piston and a passage 17 in theadjacent cylinderwall which registers with the slot 16.
In accordance with the present invention, the compressor is providedwith an. intake orsuction: gas muffler in the form of a bowl-shaped body'l8 havingan arcuate depression 19 in the bottom wall thereof adapted, as shown in FIG. 3, to conform to. the exterior surface of the adjacent cylinder wall portion, the muffler body 19 being-brazed or otherwise ridgedly secured to the exterior surface of the cylinder 5.. The bottom wall of the muffler body also: has an opening'2l registering with the opening l7inthe cylinder side wall.
The muffler body portion 18 is: generally cylindrical in cross section and is provided with a cover or plate 22 forming the top wall? of the muffler, the cover plate;22
being secured to the flange edge 23 of the body portion 18 by means of a spring clip 24.
Suction gas is admitted. to. the muffler in accordance: with the present invention through a pair of spaced tubular members 25 which, as shown in FIG. 1,. are mounted in the cover 22 and are on diametrically. opposite sides of the center of this cover 221. These two tubes 25, one of which is shown in FIG... 2, extend into. the interior of the muffler, that is downwardly into the bowl-shaped body portion 18 with their lower ends 27 terminating short of the bottom wall? of themuffler.
Also as shown in FIG.. 1, the cover plate .22; is mounted on the muffler body 18 in azposition. such that the outlet ends of the tubes are off-set from. the passage" 21 and more specifically are on opposite sides ofthe the passage 21.
During operation of the compressor, that is during the reciprocating movement of the piston 6 within the cylinder 5, the gas flow through the muffler 18 is of a pulsating nature, during the suction stroke of the piston 6, gas is drawn from the interior of the hollow piston into the cylinder and hence there is a flow of gas into the muffler through the tubes 25. This results in a pulsating movement of gas through the compressor which creates frequencies in the audible range which are transmitted to the case 1 and hence exteriorly of the compressor.
By experimentation, it has been found that the provision of the two inlet tubes 25 positioned as hereinbefore described with reference to one another and with reference to the muffler outlet 21 substantially eliminate or minimize the higher frequency compressor noises to a much larger extend of either a muffler provided with similar openings free of tubes or provided with a number of tubes having substantially the same flow capacities.
While the exact reasons for this phenomenon are not known, it has been found that for a fractional horsepower compressor, as for example compressors ranging from about one-eighth to one-third horsepower and having piston displacements from about 0.312 to 0.6 cubic inches, the muffler body 18 should be approximately 2 inches in diameter and approximately onehalf inch in depth and that the tubes 25 should be about 0.45 inch in length and 0.098 inch inside diameter with a clearance between the inner ends of the tubes 25 and the bottom wall of the muffler chamber of at least onetenth inch. In accordance with the preferred embodiment of the invention, the tubes are spaced about 1 inch apart on the cover diameter.
As has been previously indicated inlet tubes in this number, configuration and size have been found to be superior from the noise elimination standpoint to a number of other mufi'ler constructions in which for example, two holes are provided in the muffler cover without tubes, the muffler cover is provided with one tube 0.5 inch long and 0.158 inch in diameter, with three tubes 0.5 inch long and 0.158 inch in diameter, with three tubes 0.5 inch long and 0.1 inch in diameter and as many as 13 tubes 0.5 inch long and 0.1 inch diameter and as many as 13 tubes 0.5 inch long and 0.038 inch in diameter. It also appears essential-that the tube placements within the cover be such that they are on opposite sides of the outlet 21 and that neither of the tubes be in alignment with the outlet 21.
While there has been shown and described a specific embodiment of the present invention, it should be understood that it is not limited thereto and is intended by the appended claims to cover all modifications that fall within the true spirit and scope of the invention.
What is claimed is:
1. In a high speed hermetic compressor comprising a casing, a compressor within said casing and including a cylinder, a hollow reciprocating piston in said cylinder, means comprising cooperating openings in the side walls of said cylinder and piston for admitting gas to said piston, and valve means for admitting gas from said piston into said cylinder during suction stroke of said piston;
an intake muffler comprising a generally cylindrical body ortion having its bottom wall mounted on the 51 e wall of said cylinder and an outlet opening in said bottom wall communicating with the opening in said cylinder side wall;
said muffler having a top wall including a pair of spaced gas inlets in the form of tubes extending inwardly from said top wall on diametrically opposite sides of the center of said top wall, the inner ends of said tubes being spaced a short distance from the bottom wall thereof and offset from said outlet opening.
2. A compressor according to claim 1 in which said tubes have an inside diameter of about 0.098 inch and the inner ends are offset from said outlet opening.
3. In a hermetic, low-side refrigerant compressor comprising a cylinder, a hollow reciprocating piston in said cylinder, means comprising cooperating openings in the side walls of said cylinder and piston for admitting low pressure gas to said piston, and valve means for admitting gas from said piston to said cylinder during suction stroke of said piston;
a generally cylindrical, bowl-shaped, intake gas muffler having its bottom wall mounted on the side wall of said cylinder and having a vertically centered outlet registering with the opening in said cylinder side wall;
said muffler having a top wall including a pair of spaced gas inlets in the form of tubes extending inwardly from said top wall on diametrically opposite sides of the center of said top wall, the inner ends of said tubes being spaceda short distance from the bottom wall thereof and offset from said outlet;
said muffler having a volume about 2.5 to 5 times the displacement of said compressor.
4. The compressor according to claim 3 in which said tubes are approximately 0.45 inch length and 0.098 inch diameter.