Pumps – Three or more cylinders arranged in parallel – radial – or...
Reexamination Certificate
2002-06-18
2003-12-30
Yu, Justine R. (Department: 3746)
Pumps
Three or more cylinders arranged in parallel, radial, or...
C091S499000, C092S057000
Reexamination Certificate
active
06669450
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to gas compressors, and more particularly to a rotary slant shaft type gas compressor having a multi-stepped exhaust system for selectively exhausting gas compressed in a cylinder according to a pressure of an exhaust channel.
(b) Description of the Related Art
A compressor is a machine for increasing a pressure and a potential speed of a medium by applying power from the outside. Such compressors are called fluid compressors since a fluid is an object of the compressor regardless of the state of the medium being compressed. As the media which may be compressed by the compressor, there are gasses such as air, nitrogen, oxygen and the like, and liquids such as oils or refrigerants. Even though a compressor to be described hereinafter may be used for compressing liquids such as oil, a gas compressor that compresses gasses such as air will be principally described.
As a publicly known gas compressor, there is a reciprocating compressor that compresses gas with a piston that carries out a simple reciprocation motion.
In general, the reciprocating compressor is formed with a cylinder, a piston reciprocating in the cylinder, and a cylinder head comprising an intake valve and an exhaust valve at an end of the cylinder, like an engine of a vehicle. In such a reciprocating compressor, intake, compression and exhaust of gasses are carried out while opening and closing the intake valve and the exhaust valve according to a gas pressure in the cylinder as the piston rectilinearly reciprocates in the cylinder.
This reciprocating compressor has, however, a disadvantage in that the intake valve and the exhaust valve mounted in the cylinder head directly contact the cylinder head or the piston during the gas compression stroke. The collision of the valves primarily induces mechanical noise, and bending or damage of the valves occurs in long-term use. Further, the reciprocating compressor has disadvantages in that a pulsation phenomenon is generated in the case of gas compression since the intake and the exhaust of gas occurs alternately in the cylinder, and that friction noise is generated by the instant expansion of the gas when opening or closing the valves.
An intake/exhaust muffler is provided to resolve the noise problem of the reciprocating compressor. However, if a muffler is mounted on the reciprocating compressor, the compressor itself becomes complicated mechanically and the number of required parts increases. Further, the gas resistance is increased due to the mounting of the muffler, thereby degrading performance of the compressor.
A slant shaft type compressor is disclosed as another gas compressor in Japanese Laying-open Publication No. 61-65081 (Apr. 3, 1986).
In the compressor disclosed in the publication No. 61-65081, rotation force of a rotation shaft is transmitted to a swivel plate, which is connected to pistons, for converting the rotation motion to a rectilinear reciprocation motion. In the compressor, a cylinder block formed with six cylinders is fixed to the rotation shaft and respective cylinders in the cylinder block are formed in a structure such that a surface facing a piston is open. The open cylinder is closed by a float valve formed with an intake/exhaust hole and a compressor case head contacts a rear surface of the float valve. A rubber ring is interposed between the float valve and the case head for preventing leakage of gas compressed in the respective cylinders.
In this compressor, if a driving shaft is rotated by rotation force transmitted from an external power supply, the cylinder block fixed to the driving shaft rotates together with the driving shaft, and the swivel plate connected to an end of the driving shaft rotates in response to the rotation of the driving shaft, so that the respective pistons rectilinearly reciprocate in the respective cylinders, in sequence.
According to the characteristics of this compressor, the respective cylinders rotate as being opened while the float valve and the case head do not move. The respective cylinders take in the gas through the intake hole of the float valve for gradually compressing the gas while rotating, and exhaust the compressed gas through the exhaust hole of the float valve toward a gas channel formed in the case head. In the above compression stroke, the float valve moves close to the cylinder block by a difference of gas pressures applied to a sectional area of the cylinder and a sectional area of the valve.
Comparing the compressor disclosed in the publication No. 61-65081 with the prior art reciprocating compressor, the piston of the compressor of 61-60851 reciprocates in parallel with the driving shaft direction, thereby allowing the manufacture of the compressor to be compact. Further, the compressor of 61-65081 does not employ reciprocating intake/exhaust valves but a fixed float valve, so that the mechanical noise caused by the direct collision between the valves and the cylinder head may be completely prevented. Furthermore, the compressor of 61-65081 exhibits compression efficiency and noise characteristics due to the gas pressure difference equal to the prior art reciprocating compressor in the case of continuous operation under a rated load.
In spite of the advantages described above, the compressor of 61-656081 has a serious disadvantage in that the cylinder block has to rub the float valve to maintain the seal between the rotating cylinder block and the stationary float valve, thereby causing abrasion of parts due to the continuous friction therebetween. In order to remove friction heat generated by the friction, the gas to be compressed has to be lubricative. Therefore, the gasses compressed in the compressor are limited to those having the lubrication property.
Further, the compressor has a disadvantage in that additional parts for emitting heat to the inside or the outside or absorbing the heat is needed, since the compression heat generated in the process of the compression of the gas in addition to the friction heat is very high. However, the compressor of 61-65081 does not suggest any heat removal parts, so durability of the compressor is degraded and gas compression efficiency is decreased by the various heat generated in actual use.
Considering the compressor of 61-65081 aerodynamically in view of the structure of the compressor, the compressor has a very big difference between a maximum pressure (Pm) in a compression section and an exhaust pressure (Pd) in an exhaust section. In this case, as the pressure difference between the two sections becomes larger, the aerodynamic noise generated when compression gas of a high pressure is discharged to a low pressure state becomes larger. Considering the compressor of 61-65081 with the prior art compressor on this issue, the compressor of 61-65081 exhibits a larger aerodynamic noise than the prior art reciprocating compressor due to such a big pressure difference.
Considering a compression load in the cylinder generated during operation, the compressor of 61-65081 exhibits a change width of the compression load per a unit time period much larger than that of the prior art reciprocating compressor. As the change of the compression load in the cylinder becomes larger, an axial force load applied to the driving shaft becomes larger. Therefore, in the compressor of 61-65081, the axial force load which is proportional to the compression load is applied to the swivel plate connected to the end of the driving shaft, directly influencing ball bearing parts mounted between a lower part of the swivel plate and the case, thereby degrading the durability of the compressor itself.
As described above, the compressor of 61-65081 has problems caused by the structure in spite of the various advantages over the prior art reciprocating compressor, so the compressor has a commercial limitation as a gas compressor.
Therefore, the demands for a new compressor of a structure that may maintain the basic characteristics of the slant shaft type gas compressor but resolves the disadv
Airzen Co., Ltd.
Alston & Bird LLP
Liu Han L
Yu Justine R.
LandOfFree
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