CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional Patent Application No. 62/337,346 filed 17 May 2016, which is hereby incorporated in its entirety by reference.

FIELD OF THE INVENTION

The present invention relates to the field of compressors, and more particularly to the field of axial double piston compressors.

BACKGROUND OF THE INVENTION

Compressors for compressing fluids, i.e., liquids and gases, typically comprise a piston, or a multitude of pistons, that move within a cylinder to compress the fluid. The pistons are operated by a connecting rod that is connected to a lower side of the piston by means of a piston pin, or a gudgeon pin, that is directed transversely to a piston axis. The piston pin passes through a ring at the small end of the piston rod such that the piston rod can rotate with respect to the piston pin. The pistons have a relatively large longitudinal extension in order to prevent tilting of the piston with respect to the longitudinal axis and possible sticking in within the cylinder.

A big end of the connecting rod is freely connected to a crank that is driven by another mechanism, e.g., an electrical motor or an internal combustion engine.

Such types of compressors suffer from a disadvantage that they are formed from a large number of parts, a fact that requires precisely produced parts, thus increasing their cost, and, a laborious assembly, which takes a lot of time and costs more. Furthermore, this structure creates large transverse force between the piston and the cylinder.

It is the object of the present invention to provide a compressor that significantly reduces or overcomes the aforementioned disadvantages.

It is a further object of the present invention to provide a compressor wherein the pistons, the piston pin, and the connecting rod are formed from a single piece, which may be produced by injection molding or using other techniques known in the art. In that manner, the compressor according to the present invention acquires the following advantages: reduced number of parts, no need of exact precision between assembled parts, and no need of laborious assembly.

It is still a further object of the present invention to provide a compressor wherein the motor is connected directly to the cam, thus saving weight, money, and reduces operation noise.

It is yet another object of the present invention to provide a compressor that significantly reduces or eliminates any transverse forces between the piston and the cylinder during operation.

SUMMARY OF THE INVENTION

The invention provides a compressing unit having an integral flexible pivot between a connecting rod and one piston. This is enabled due to relatively large length of the connecting rod with respect to a crank that is connected thereto.

This construction enables to eliminate, or reduce to a minimum, any transverse forces exerted by the pistons on the cylinder. Thus, the longitudinal extension of the sliding surface of the pistons may be reduced to a minimum.

There is provided, in accordance with an embodiment of the present invention, a compressing unit including a cylinder, a first piston configured to slide along the cylinder, and a connecting rod attached to the first piston at a first end and to a crank at a second end. The crank is configured to be directly attached to a motor shaft.

In some embodiments, a length L of the connecting rod is substantially greater than an operating radius R of the crank. Optionally, the length L of the connecting rod is at least five times greater than the operating radius R of the crank. Optionally, the length L of the connecting rod is at least ten times greater than the operating radius R of the crank.

In some embodiments, the first end of the connecting rod includes an integral flexible pivot. Additionally, the integral flexible pivot is integral with the first piston.

In some embodiments, the first piston includes a sliding surface with a substantially reduced longitudinal extension in contact with the cylinder. The sliding surface may be integral with the first piston.

In some embodiments, the compressing unit includes a second piston configured to slide along the cylinder.

In some embodiments, the compressing unit includes a piston rod connecting the first piston to the second piston.

In some embodiments, the length L of the connecting rod is greater than half the length of the piston rod.

In some embodiments, the motor shaft includes an electric motor shaft.

There is further provided, in accordance with an embodiment of the present invention, a method of producing a compressing unit, the method including integrally. The connecting rod is integral with the first piston at a first end and connects to a crank at a second end. The crank is configured to be directly attached to a motor shaft. A length L of the connecting rod is substantially greater than an operating radius R of the crank.

In some embodiments, the method includes using injection molding to integrally mold the first piston with the flexible pivot and the connecting rod.

In some embodiments, the method includes integrally molding a piston rod with the first piston.

In some embodiments, the method includes integrally molding a second piston with the piston rod.

There is further provided, in accordance with an embodiment of the present invention, a method of using a compressing unit, the method includes rotating a crank connected directly to a motor shaft at a substantially high speed, translating rotational motion from the crank to linear motion using a connecting rod attached to a first piston at a first end and to a crank at a second end, and sliding the first piston forward and backward inside a cylinder. BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention and to show how the same may be carried out in practice, reference will now be made to the accompanying drawings, in which:

Fig. 1 is a side cross-sectional view of the compressing unit of a compressor according to the present invention;

Fig. 2 is a perspective view of the compressing unit of Fig. 1 according to the present invention; and

Fig. 3 is a side cross-sectional enlarged view of the crank of Fig. 1 according to the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

Attention is drawn to Figs. 1 , 2 and 3 that show a compressing unit 10 of a compressor 12 (that, for a matter of simplicity, is not shown as a whole) according to the present invention. The compressing unit 10 comprises an elongated cylinder 14 having a longitudinal axis A. A pair of pistons 16 is located within the cylinder 14 and are co-axial with the longitudinal axis A.

It should be noted that directional terms appearing throughout the specification, e.g. "forward", "rear", "upper", "lower" etc., are used as terms of convenience to distinguish the location of various surfaces relative to each other. These terms are defined with reference to the figures, however, they are used for illustrative purposes only, and are not intended to limit the scope of the invention.

The pistons 16 are connected therebetween by means of a piston rod 18. According to some embodiments, the piston rod 18 consists of a single piece. According to other embodiments, the piston rod 18 consists of two individual rods that connect between the two pistons 16.

Each piston 16 comprises a front compressing surface 20, a rear surface 22, and, a sliding surface 24 which is in contact with the cylinder 14 and slides thereon.

Since the distance between the two pistons 16 is relatively large, it enables a stable translational movement of the pistons 16 within the cylinder 14 along the longitudinal axis A. Thus, it enables producing the sliding surfaces 24 with a minimal longitudinal extension while still providing an adequate sealing between the pistons 16 and the cylinder 14. According to some embodiments, the sliding surface 24 of each piston 16 has a longitudinal extension of 1mm.

The sealing portion between the pistons 16 and the cylinder 14 may be mounted on the sliding surfaces 24 of the pistons, or, may advantageously form an integral portion therewith.

The compressing unit 10 is operated by means of an electric motor (not shown in the figures) that is located out of the cylinder 14 and directed perpendicularly to the longitudinal axis A. The shaft of the electric motor is connected directly into an electric motor shaft seating 26 of a crank 28. The crank 28 has a crank pin 30 that is inserted into a corresponding pin hole in a first end 32 of a connecting rod 34 that is adjacent a rear surface 22 of a first piston 36. The connecting rod 34, having a length L, is relatively large and extends almost to the entire length of the piston rod 18.

A second end 38 of the connecting rod 34 is connected to the rear surface 22 of the second piston 40 through an integral flexible pivot 42. The connecting rod 34, the integral flexible pivot 42, the pistons 16 and the piston rod 18 are all formed from a single unitary piece that is formed by injection molding or other methods known in the art and which may include three- dimensional printing.

The crank 28 has an operating radius R which is defined between an electric motor axis B and a crank pin axis C. Since the length L of the connecting rod 34 is much larger than the operating radius R of the crank 28, the rotation of the first end 32 of the connecting rod 34, together with the crank 28, around the electric motor axis B causes only a little rotational and translational movements of the second end 38 of the connecting rod 34 with respect to the rear surface 22 of the second piston 40. Thus, it is possible to form the connecting rod 34, the integral flexible pivot 42 and the piston 16, and also the piston rod 18 and the other piston 16, as a single unitary piece, thus enabling to reduce production and assembling costs, from one side, and enabling long service life of the integral flexible pivot 42, from another side.

Since the crank 28 is connected directly to the electric motor shaft, and not via a speed-reducing mechanism, various advantages are obtained: (1) the crank 28 rotates at a relatively very high speed thus creating fast compression action of the pistons 16 and compensation for the small stroke, (2) money saving, due to the unnecessary speed-reducing mechanism, (3) longer service life due to the lack of a need to use a speed-reducing mechanism, (4) much quieter action of the entire compressor due to the avoidance of using a speed- reducing mechanism.

The compressing unit 10 operates efficiently with an alternating-stroke effect, i.e., when the first piston 36 makes a compression stroke, then, the second piston 40 makes a suction stroke, and, when the second piston 40 makes a compression stroke, then, the first piston 36 makes a suction stroke.

Although the present invention has been described to a certain degree of particularity, it should be understood that various alterations and modifications could be made without departing from the spirit or scope of the invention as hereinafter described.

For example, the second end 38 of the connecting rod 34 does not have to be connected to the rear surface 22 of the second piston 40 through an integral flexible pivot 42. Alternatively, the second end 38 of the connecting rod 34 may be connected to the rear surface 22 of the second piston 40 through another type of joint that is not necessarily integral therewith.

The second end 38 of the connecting rod 34 does not have to be connected to the rear surface 22 of the second piston 40 through an integral flexible pivot 42. Alternatively, the second end of the connecting rod may be connected to a connecting link that connects between the piston rods and is directed substantially perpendicular to the longitudinal axis A. According to some embodiments, the connecting link does not have to be connected to the rear surface of the piston.