RU1820035C - Two-rotor screw oilless vacuum pump - Google Patents

Abstract

SUMMARY OF THE INVENTION: screw rotors with the same profile form with the housing working cavities of the first and second stages communicating with each other by a channel. The rotors of the first and second stages are interconnected in pairs and are made with different pitch of the helix, the rotors of the first stage with a large one, the rotors of the second stage with a smaller pitch. The rotors are connected so that the edge formed by the intersection of the helical surface with the end surface of the screw with a large pitch overlaps the similar edge of the screw with a smaller pitch. An exhaust valve is installed on the housing on the discharge side of the first stage. 1 s.p. f-ly, 5 ill.

Description

The invention relates to the field of vacuum technology, in particular to oil-free screw vacuum pumps and can be used to pump gas and air.

In FIG. 1-5 shows the proposed pump rotor.

The vacuum pump (Fig. 1) consists of a housing 1, end caps 2 and 3, rotors 4 with a rectangular groove profile on them, synchronizing gears 5, inlet 6 and pressure windows 7, exhaust valve 8. The rotor (Fig. 2) consists of two screws 9 with a smaller step (second stage) and 10 with a large step (first stage). A smaller pitch screw is located on the discharge side of the pump. The screws 9 and 10 are interconnected so that the edge 11 (Fig. 3) of the screw with a smaller pitch overlaps the similar edge 12 of the screw with a large pitch. This allows you to separate the working cavity of the two stages and at the same time form on the opposite side of the rotor channel 13

(Fig. 4) for pumping compressed gas from a first stage to a second.

When the rotors are turned one revolution each of the turns with a large step on the suction side, a gas volume equal to the volume of the screw grooves of one turn is captured. With further rotation, the gas moves towards the coil with a smaller step. After the working cavity is connected to the end surface of the screw with a smaller pitch, gas compression begins due to the mutual engagement of the last screws of the first stage with the corresponding grooves. Compressed gas through channel 13 is pushed into the working cavity of the second stage, where further compression occurs (similar to the first stage) and gas is injected through the window 7. When the pump is operating at high inlet pressures, even after the first stage, the pressure may be higher than atmospheric. In this case, the valve 8 connected to the compression cavity of the first stage opens and the pressure is released to atmospheric.

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The proposed technical solution allows increasing the compression ratio of the pump in proportion to the ratio of the maximum suction volume of the first stage to the suction volume of the second stage or in proportion to the ratio of the steps of their helical lines and, thereby, to reduce the maximum residual pressure created by the pump.

SUMMARY OF THE INVENTION 1. A two-rotor screw oil-free vacuum pump comprising a housing with inlet and discharge windows, screw rotors with the same profile, forming working cavities of the first and second stages communicating with each other by the channel, and rotors of the first and

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the second stages are interconnected in pairs, characterized in that, in order to reduce the maximum residual pressure, the rotors of the first and second stages are made with different pitch of the helix, the rotors of the first stage with a larger one, and the rotors of the second stage with a smaller pitch, and the rotors are connected with each other so that the edge formed by the intersection of the helical surface with the end surface of the screw with a large pitch overlaps the similar edge of the screw with a smaller pitch.

2. A pump according to claim 1, characterized in that an exhaust valve is installed on the pump casing on the discharge side of the first stage.

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