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Piston vacuum pumpRelated Patent Categories: Pumps, Expansible Chamber Type, Pumping Member Position Controlled PortPiston vacuum pump description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060280634, Piston vacuum pump. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND [0001] The invention relates to a piston vacuum pump with a gas inlet in a cylinder side wall. [0002] In piston vacuum pumps and in small piston vacuum pumps with a pumping output of less than 4 m.sup.3/h in particular, the construction of the gas inlet and the dead volumes associated therewith play a great part for the structural size and the efficiency of the pump, respectively. Since the gas inlet cannot be arranged in the region of the cylinder bottom for lack of structural space, particularly in small vacuum pumps, the gas inlet is arranged in a side wall. Such a piston vacuum pump is described in DE 196 34 517. For balancing the pressure at the beginning of the intake stroke, an equalizing conduit is provided between the exhaust and the compression chamber, the mouth of the equalizing bore being arranged in the compression chamber near the cylinder bottom. In the course of the equalizing conduit, a non-return valve is arranged which needs structural space. The non-return valve is not arranged in the cylinder wall plane so that a dead volume degrading the efficiency is formed in the equalizing conduit. [0003] Against this background, it is an object of the invention to provide an improved piston vacuum pump with a gas inlet in the cylinder side wall. SUMMARY [0004] According to the invention, the piston substantially forms the equalizing conduit and the valve. This is to mean that the piston forms the equalizing conduit and the valve at least partially, but not necessarily alone. Since the equalizing conduit is formed by the piston, the equalizing conduit does not require any space in the region of the cylinder bottom or the cylinder side. A compact construction of the cylinder is made possible thereby. The valve is also formed substantially by the piston so that the valve effect is produced at the piston end wall or in the immediate neighborhood of the piston end wall. Thereby, a dead volume outside the cylinder chamber is avoided so that the efficiency of the pump is not degraded. The equalizing conduit and the valve can be formed by the piston in different ways. The valve can be configured as a mechanical non-return valve but also as a gas throttle. The equalizing conduit can be formed by the piston only, but also by the piston and the cylinder in common. [0005] According to a preferred embodiment, the equalizing conduit is formed in the piston between a piston end wall opening and a piston bottom wall opening, the piston side wall opening and the gas inlet being connected with each other at the beginning of the intake stroke. Hence, at the beginning of the intake stroke, there exists a connection from the gas inlet to the compression chamber although the piston is still at the level of the gas inlet and does not permit a direct escape of gas from the gas inlet into the compression chamber. [0006] Preferably, the valve is a non-return valve blocking in the direction of the gas inlet and opening in the direction of the compression chamber. Thereby, a reflux of compressed gas via the equalizing conduit is prevented during the compression stroke. The non-return valve may be arranged in the plane of the piston end wall so that the dead volume practically equals zero. [0007] According to a preferred embodiment, the gas inlet has an annular groove in the cylinder side wall and/or in the piston side wall allocated thereto. Thereby, an enlargement of the gas inlet is effected or, if the piston is not guided, a gas transfer between cylinder and piston is made possible in any rotational position of the piston. The annular groove may also be enlarged in axial extension with respect to the gas inlet to extend the gas entry during the intake stroke. [0008] Preferably, the equalizing conduit and the valve are formed by a gap between the piston side wall and the cylinder side wall, the gap width ranging between 10 to 100 .mu.m. The equalizing conduit and the valve are thus defined by the piston side wall and the cylinder side wall. The gap width is selected such that a sufficient gas flow occurs between the gas inlet and the compression chamber during the intake stroke, the gas flow from the compression chamber to the gas inlet during the compression stroke, however, is so small that it does not substantially degrade the efficiency of the pump. The gap between the piston side wall and the cylinder side wall is an equalizing conduit and a valve at the same time. This is guaranteed with gap widths of 10 to 100 .mu.m, the gap width being required to be below 50 .mu.m with differential pressures of more than 100 mbar (1.45 psi). [0009] Preferably, a storage chamber is provided in the course of the equalizing conduit in the piston. With a piston position about the dead center between intake stroke and compression stroke, the storage chamber is filled so that a pressure compensation between the storage chamber and the compression chamber can be effected by the piston end wall directly at the beginning of the intake stroke while the gas inlet is simultaneously closed. [0010] Preferably, the equalizing conduit and the valve are formed by a substantially axial groove in the piston side wall or in the cylinder side wall. The groove may extend axially, but may also be formed obliquely in the form of a helical line in the piston side wall or the cylinder side wall. Thus, an equalizing conduit is also formed which does not need any mechanical elements and can be produced easily. The valve effect results from a corresponding selection of the cross section of the groove which is selected such that a sufficient pressure compensation is guaranteed during the intake stroke, but no reflux losses occur during the compression stroke which are too great. [0011] According to a preferred embodiment, the valve is configured as a throttle. This means that the valve is implemented without any movable parts, whereby a high reliability is achieved and low manufacturing costs are realized. [0012] Hereinafter, several embodiments of the invention are explained in detail with reference to the drawings. [0013] Still further advantages of the present invention will be appreciated to those of ordinary skill in the art upon reading and understanding the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS [0014] The invention may take form in various components and arrangements of components, and in various steps and arrangements of steps. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. [0015] FIG. 1 shows a first embodiment of a piston vacuum pump with an equalizing conduit and a valve arranged in the piston and in the dead center of the piston between the compression stroke and the intake stroke, [0016] FIG. 2 shows the piston vacuum pump of FIG. 1 during the intake stroke, [0017] FIG. 3 shows a second embodiment of the piston vacuum pump with a circumferential gas inlet groove, [0018] FIG. 4 shows a third embodiment of the piston vacuum pump with a circumferential gas inlet groove in the piston side wall, [0019] FIG. 5 shows a fourth embodiment of the piston vacuum pump with a gap between the piston side wall and the cylinder side wall, which forms the equalizing conduit and the valve, and [0020] FIG. 6 shows a fifth embodiment of a piston vacuum pump where the equalizing conduit and the valve are formed by an axial groove in the piston side wall. DETAILED DESCRIPTION Continue reading about Piston vacuum pump... Full patent description for Piston vacuum pump Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Piston vacuum pump patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Piston vacuum pump or other areas of interest. ### Previous Patent Application: Tube pummp Next Patent Application: Arrangement and method for the mixing of particulate filling such as pieces of nougat or fruit into consumer ice mass Industry Class: Pumps ### FreshPatents.com Support Thank you for viewing the Piston vacuum pump patent info. 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