Cylinder assembly for a mini air compressor

Abstract

A cylinder assembly for a mini air compressor includes a cylinder, a discharge check valve, a piston, a supply check valve and a piston rod. The cylinder has two open ends, and the piston with an open end and a closed end is slidably mounted in the cylinder. A supply check valve is mounted on the closed end of the piston. A discharge check valve is adapted to mount on and seal one end of the cylinder. At least one of the supply check valve and the discharge check valve has with a flexible, resilient disk. Two check valves are configured such that only one valve opens at a time when the piston slides in the cylinder.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a cylinder assembly for a mini air compressor and more particularly to a cylinder assembly for a mini air compressor with at least one simplified check valve that uses a resilient disk to open and close the valve.

[0003] 2. Description of Related Art

[0004] Air compressors increase the pressure of air for application in other devices or systems. A reciprocating air compressor has at least one cylinder assembly to compress the air. With reference to FIG. 5, the cylinder assembly (70) includes a piston rod (71), a cylinder (72), a piston (73), a supply check valve (74) and a discharge check valve (75). The cylinder (72) has an open end and a closed end. The piston (73) is cylindrical with two ends, one open and one closed, pivotally attached to the piston rod (71) near the open end and is slidably mounted in the cylinder (72) with the closed end facing the closed end of the cylinder (72). The supply check valve (74) is mounted in the closed end of the piston (73). The discharge check valve (75) is mounted in the closed end of the cylinder (72). The piston rod (71) drives the piston (73), and the piston (73) moves reciprocally in the cylinder (72). The reciprocating motion of the piston (73) draws air into the cylinder (72) through the supply check valve (74) during one stroke and compresses the air when the piston (73) slides toward the discharge check valve (75). The compressed air passes through the discharge check valve (75) and is accumulated in a storage container such as an air tank.

[0005] A conventional discharge check valve (75) is composed of a valve port (751), a valve spring (752) and a valve disk (753). Air passes out of the cylinder (72) and into the discharge check valve (75) through the valve port (751), and the valve disk (753) selectively opens the valve port (751) to allow air to flow into the discharge check valve (75) only. The valve spring (752) presses the valve disk (753) against the valve port (751) to keep the discharge check valve (75) normally closed unless pressure is applied to the face of the valve disk (753) to overcome the force of the valve spring (752). When the piston (73) is traveling away from the discharge check valve (75), the supply check valve (74) is open and the discharge check valve (75) is closed.

[0006] This mechanical structure has the following shortcomings:

[0007] Expensive and complex:

[0008] Because this kind of check valve has numerous parts several of which must be machined to ensure a tight fit, the valve is expensive, and the structure is more complex than necessary especially for low pressure applications. The valve disk (753) has a special shape including a device around which the valve spring (752) is mounted and the surface that abuts and closes the valve port (751). The precision required to is make the valve keeps cost of the cylinder assembly from being reduced significantly.

[0009] Efficiency issue:

[0010] The valve spring (752) presses the valve disk (753) against and closes the valve port (751). Each cycle of the piston (73) compresses the valve spring (752), which causes the valve spring (752) to lose its resilience and reduce the elastic force pressing the valve disk (753) closed. Consequently, air will escape back into the cylinder (72) before the valve port (751) is closed completely, and the compression efficiency of the cylinder assembly is reduced.

[0011] To overcome the shortcomings, the present invention provides an improved cylinder assembly to mitigate and/or obviate the aforementioned problems.

SUMMARY OF THE INVENTION

[0012] The main objective of the invention is to provide a simplified cylinder assembly for a mini air compressor. The cylinder assembly includes a cylinder with two open ends, a discharge check valve is mounted in one open end and a strongback is mounted over the discharge check valve. A piston with an open end and a closed end is mounted in the cylinder through the other open end of the cylinder. The open end of the piston faces the open end of the cylinder, and the closed end faces the discharge check valve. A supply check valve is mounted over supply ports in the closed end of the piston, and a piston rod is connected to the piston through the open end of the piston. Besides the supply ports formed in the closed end of the piston, at l least one discharge port is formed in the discharge check valve. At least one of the supply check valve and the discharge check valve has a resilient disk attached to the valve to cover the corresponding valve port. The two check valves are configured so only one valve opens at a time when the piston slides in the cylinder. Accordingly, the structure of the cylinder is simplified, and the cost for manufacturing the cylinder is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is an exploded perspective view of an air compressor with two cylinder assemblies in accordance with the present invention;

[0014] FIG. 2 is an exploded perspective view of a cylinder assembly in FIG. 1;

[0015] FIG. 3 is an operational side plan view in partial section of the cylinder assembly in FIG. 2;

[0016] FIG. 4 is an operational side plan view in partial section of the cylinder assembly in FIG. 2; and

[0017] FIG. 5 is a side plan view in partial section of a conventional cylinder assembly of an air compressor.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

[0018] With reference to FIG. 1, a mini air compressor comprises a chassis (10), a motor (11), a gearbox (12), a driven shaft (13), an eccentric drive wheel (14) and two cylinder assemblies (20). The chassis (10) has two sides. The motor (11) has a drive shaft and is attached to one side of the chassis (10). The drive shaft extends through the chassis (10). The gearbox (12) with an enclosed gear set (122) is attached to the side of the chassis (10) opposite to the motor (11). The gear set (122) is connected to the drive shaft of the motor (11). The driven shaft (13) has two ends and passes through the chassis (10) with one end on each side of the chassis (10). One end of the driven shaft (13) is connected to the gear set (122). The eccentric drive wheel (14) is connected to the other end of the driven shaft (13). The cylinder assemblies (20) are connected to the eccentric drive wheel (14) and are mounted on the chassis (10).

[0019] To operate the mini-air compressor, the motor (11) generates the power, and the drive shaft drives the gear set (122) in the gearbox (12). The gearbox (12) adjusts the power and outputs the power to the driven shaft (13). The driven shaft (13) rotates the eccentric drive wheel (14), and the eccentric drive wheel (14) drives the cylinder assemblies (20).

[0020] With further reference to FIGS. 2 and 3, the cylinder assembly (20) in accordance with the present invention comprises a cylinder (21), a piston (22), a piston rod (23), a supply check valve (24), a discharge check valve (25) and a strongback (26). The cylinder (21) has two open ends (212, 214). The piston (22) is cylindrical with an inside and outside and has an open end (222) and a closed end (224). The piston (22) is slidably mounted in the cylinder (21) through one open end (214) of the cylinder (21) with the open end (222) of the piston (22) facing the outside of the cylinder (21). The piston rod (23) is pivotally attached to the inside of the piston (22) through the open end (222). The supply check valve (24) is mounted on the closed end (224) of the piston (22) facing the inside of the cylinder (21). The discharge check valve (25) is mounted on the open end (212) of the cylinder (21) opposite to the end through which the piston (22) is mounted. The strongback (26) is mounted over and holds the discharge check valve (25) on the open end (212) of the cylinder (21). A discharge fitting (262) is formed on the strongback (26).

[0021] The supply check valve (24) and the discharge check valve (25) have the same basic structure with minor variations. The supply check valve (24) comprises supply ports (241), a disk stub (242) and a resilient disk (243). The supply ports (241) are defined through the closed end (224) of the piston (22). The disk stub (242) is a short shaft with a slightly enlarged head (244), is formed on the closed end (224) of the piston (22) and extends into the cylinder (21). The resilient disk (243) is a circular piece of flexible, resilient material with a hole in the center to mount the resilient disk (243) on the disk stub (242) to cover the supply ports (241). The discharge check valve (25) comprises a body (251), discharge ports (252), a disk stub (253) and a resilient disk (254). The body (251) has an inside end and an outside end and is adapted to be mounted on and seal one end (212) of the cylinder (21). The discharge ports (252) are formed through the body to communicate with the inside of the cylinder (21). The disk stub (253) is a short shaft with a slightly enlarged head (255), is formed on the outside end of the body (251) and extends away from the cylinder (21) toward the strongback (26). The resilient disk (254) is a circular piece of flexible, resilient material with a hole in the center to mount the resilient disk (243) on the disk stub (253) to cover the discharge ports (252).

[0022] With reference to FIGS. 3 and 4, the cylinder assembly operates by sliding the piston (22) in and out of the cylinder (21) to generate a compression stroke (sliding in) and a suction stroke (sliding out). When the piston (22) slides out of the cylinder (21), the movement generates a lower pressure in the cylinder (21) between the closed end (224) of the piston (22) and the discharge check valve (25) than a relatively higher ambient air pressure. The relatively higher ambient air pressure presses the resilient disk (254) of the discharge check valve (25) against the body (251), which seals the discharge ports (252). This closes the discharge check valve (25). Simultaneously, the relatively higher ambient air pressure presses the resilient disk (243) of the supply check valve (24) away from the supply ports (241), which allows air to flow into the cylinder (21) through the supply ports (241).

[0023] With reference to FIG. 4, when the piston (22) reverses direction and slides into the cylinder (21) toward the discharge check valve (25), the air in the cylinder between the piston (22) and the discharge check valve (25) is compressed such that the pressure of the air in the cylinder (21) is relatively higher than the ambient air pressure. The relatively higher air pressure in the cylinder (21) pushes the resilient disk (243) of the supply check valve (24) against and seals the supply ports (241). The relatively higher air pressure in the cylinder (21) pushes the resilient disk (254) away from the discharge ports (252) and the compressed air flows through the discharge fitting to a means to store or use the compressed air.

[0024] The invention simplifies the cylinder assembly and uses a flexible, resilient disk (243, 254) to cause the check valves (24, 25) to open and close in the cylinder (21). There is no problem about elastic fatigue or a machined shape of the valve disk. The flexible, resilient disk (243, 254) is simpler and cheaper than the machined valve disk. The cylinder assembly is simpler, cheaper and more efficient. In addition, one of the simplified check valves can be instead of a different type of check valve such as the conventional check valve as shown in FIG. 5. The cylinder with a simplified check valve in accordance with the present invention and a conventional check valve can also achieve an effect of simplifying the structure of the cylinder.

[0025] Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, it will be obvious to those skilled in the art that various modifications may be made without departing from what is intended to be limited solely by the appended claims.

Claims

1. A cylinder assembly for a mini air compressor comprising: a cylinder with a first and a second open ends; a discharge check valve with a body mounted on the first open end of the cylinder and at least one discharge port defined through the body of the discharge check valve; a strongback mounted over and holding the discharge check valve on the first open end of the cylinder; a cylindrical piston with an inside and an outside, an open end and a closed end slidably mounted in the cylinder through the second open end of the cylinder with the open end of the piston facing an outside of the cylinder; a piston rod pivotally attached to the inside of the piston through the open end of the piston; and a supply check valve mounted on the closed end of the piston facing an inside of the cylinder and at least one supply port defined through the closed end of the piston, wherein at least one of the discharge and supply check valves has a disk stub with a short shaft and a slightly enlarged head formed on the valve and a resilient disk mounted on said disk stub and corresponding to the at least one port in the valve to cover said corresponding at least one port.

2. The cylinder assembly for a mini air compressor as claimed in claim 1, wherein the supply valve has a disk stub formed on the closed end of said piston and extends toward the discharge check valve and a resilient disk mounted on said disk stub to cover said supply ports to allow said supply check valve to open toward said discharge check valve.

3. The cylinder assembly for a mini air compressor as claimed in claim 1, wherein the discharge valve has a disk stub facing said strongback and formed on the body of said discharge check valve and a resilient disk mounted on said disk stub to cover said discharge ports to allow the discharge check valve to open toward said strongback.

4. The cylinder assembly for a mini air compressor as claimed in claim 1, wherein a discharge fitting is formed on the strongback.