JPS6217389A - Machine pump - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oil-less mechanical pump, and in particular to an oil-less mechanical pump having at least two stages each containing meshed rotors in one pump chamber (a pu+wping chaa+ber ).

One problem with such mechanical pumps arises from the significant differences in gas pressure that can occur between adjacent stages.

In such cases, a high incidence of back leakage of pumped gas is likely to occur between stages. In particular, this high incidence of back leakage is likely to occur through the annular gap between the drive shaft and the hole in the inner wall of the stage separating adjacent pump chambers.

The back leakage of gas through the annular gap in the inner wall of the stage effectively causes a backflow of gas from the pump outlet to the pump inlet, effectively increasing the volume of gas to be pumped again and increasing the volumetric efficiency of the pump. That is, the degree of vacuum obtained is significantly reduced.

Co-pending British Patent Application N12.111.126A discloses and claims a mechanical vacuum pump having multiple pump stages each including meshing rotors in independent pump chambers. The pump of this prior application is characterized by the absence of internal lubrication and the presence at the outlet end of the pump of at least two adjacent stages with interlocking melon-shaped rotors.

The relatively high gas compression associated with the absence of internal lubricant in the internal annular gap further increases the incidence of back leakage.

Therefore, one object of the present invention is to prevent such back leakage from
In particular, the aim is to reduce the negative effects on the vacuum obtained in dry mechanical pumps.

According to its broadest aspects, the present invention is a mechanical pump having at least two stages each including an intermeshing rotor in a pump chamber, the rotor being separated by a wall separating one chamber from an adjacent chamber. A duct device is attached to the shaft passing through the pump and transfers the gas that enters the annular gap between the shaft and the partition or shaft support in the wall in the relatively high pressure region of the pump to the relatively low pressure region of the pump. A mechanical pump is provided.

In a preferred embodiment of the invention, the duct arrangement is arranged to transport gas from the annular gap in the high pressure region of the pump chamber to the lower pressure region of the same chamber.

In this case, the invention relates to a mechanical vacuum pump of the type disclosed and claimed in the pending British patent application, i.e. a melon type in which two adjacent pump stages at the outlet of the pump are respectively mounted in opposite directions. The present invention exhibits particular advantages when implemented in a mechanical vacuum pump having an intermeshing pair of rotors.

The duct arrangement has an annular groove in the partition wall between the stages, ideally provided in the partition wall, the annular groove completely or partially surrounding the shaft and at a relatively low pressure of the pump. It is appropriate to communicate with the area.

Conveniently, in one stage of the pump, the duct communicates with a similar annular groove provided in the partition in the relatively low pressure region of the same stage and with the inlet of that stage. Thus, gas leaks are directed back to the inlet side of the stage from which the gas comes instead of entering the inlet side of the previous stage.

Embodiments of the invention will now be described in detail, by way of example only, with reference to the accompanying drawings.

Referring to Figure 1 of the drawings, a mechanical pump, designated generally at 1, has a pump housing 2 through which a pair of parallel drive shafts 3 extend. Axis 3
supports three pairs of rotors 4, 5°6 so as to rotate together with the shaft 3.

The rotors 4, 5.6 are arranged longitudinally on their respective shafts 3 in complementary intermeshing pairs, as shown more clearly in FIG.

Referring again to FIG. 1, the pump housing 2 is divided by partition walls 8.9 into three spaced independent pumping chambers 10.11.12, each pumping chamber 10.11. includes a pair of intermeshing rotors that produce the pumping of gas.

At one end of the pump housing, each of the shafts 3 carries a timing gear 13, and at the other end of the housing, one of the shafts is connected via a suitable coupling (not shown) of a type well known in the art. It can be driven by being connected to a motor.

As can be seen in FIG. 2, the pair of intermeshed rotors 4 in the pump chamber 10 are of the Roots type, well known in the art, and are one of the first high vacuum or inlet stages of the multistage pump 1. form a section.

The profile of the Roots rotor 4 is such that the carry over volume of pumped gas is minimized. This means that the rotor 4 that cooperates with
This means that during their interaction, the profile is such that the volume of gas captured on the exhaust side of the rotor and transported to the inlet side of the rotor is kept to a practical minimum. Gas carried over from the exhaust side to the inlet side of chamber 10 tends to expand, thus reducing the volumetric efficiency of the pump.

The gas exhausted from the pump chamber 10 is transferred to the pump chambers 10 and 1.
The inlet of the pump chamber 11 is entered through a suitable duct provided in the wall 9 forming a partition between the pump chamber 11 and the pump chamber 11 and terminating in an inlet opening 54 of the chamber 11.

Referring again to FIG. 1, the rotor 5 within the pump chamber 11 is of an interlocking melon shape as is well known in the art. The gas entering the intermediate pressure chamber 11 through the inlet opening 54 is provided in the wall 8 forming the partition between the pump chambers 11 and 12;
It is pumped to an outlet opening 22 which also serves as an inlet opening of the pump chamber 12. Although not shown, the inlet and outlet openings of the pump chamber are in the form of bow slots.

Gas entering pump chamber 12 at relatively high pressure is pumped by a pair of intermeshing rotors 6 to an exhaust port 14 of chamber 12 and, preferably, but not necessarily, to a
I12,111.126 A t'lri L/-
It is pumped to atmosphere via a one-way valve 16, which is effective to improve pump efficiency in a controlled manner.

If the illustrated pump is a dry pump, i.e. a pump that does not include internal fluid lubrication equipment, the gas compressed by the pair of meshing rotors 6 in the pump chamber 12 will primarily flow through the holes in the partitions 8, 9 and the shaft 3. There is a tendency for back leakage into the pump chamber 11 through the annular gap between.

Such back leakage of gas has a particular effect on the pumping efficiency in volume, since due to the opposite orientation of the paired rotors 5.6, such gas expands towards the inlet side of the pumping chamber 11.

In order to improve this reverse leakage effect, the partition wall 8 is provided with a circumferentially continuous groove 51 in the region of the shaft, as shown in FIG. The grooves 51 communicate with each other via ducts or holes 52 which are also provided in the partition wall 8 and with the transfer opening (exit opening) 22 .

During operation of the pump, when gas is being pumped from the low pressure end to the high pressure end through the pump chambers 10.11.12, the gas compressed by the rotor 6 at the highest pressure outlet end of the chamber 12 is transferred to the There is a tendency to leak into the pump chamber 11 through the annular gap, particularly through the gap closest to the high-pressure delivery outlet 14 (shown at the top of the figure).

Such reverse leakage gas, instead of leaking to the inlet side of the pump chamber 11, is captured by the groove 51 and flows into the duct or hole 52.
It passes through the cooperating groove 51 and enters the transfer opening 22, where it is pumped again in the chamber 12. Groove 51 and duct 5
The effect of gas diversion through 2 is to recirculate the back leakage gas only to pump chamber 12 rather than to both pump chambers 11 and 12, significantly reducing the loss in volumetric pumping efficiency.

Although the invention has been described with reference to a groove 51 in the shaft seal between pump chambers 11 and 12, the invention is equally applicable to other adjacent pump chambers, and in fact prevents reverse leakage. It will be appreciated that this would equally apply to other areas of the pump where this would cause a loss in pump efficiency. Although the invention has been described with reference to a dry vacuum pump, it is understood that it is equally applicable to vacuum pumps and mechanical pumps that have internal hot water facilities, but whose lubrication facilities are not sufficient to prevent back leakage of gas. Good morning.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional side view of a dry mechanical vacuum pump having three chambers each containing a pair of intermeshing rotors. 2 is a perspective view of a rotor incorporated into the pump of FIG. 1; FIG. 1...Mechanical pump, 4.5.6...Rotor, 3...Shaft, 10.11.12...
・Pump room, 8.9... Bulkhead, 51...
・Groove, 52...Duct, hole, 54-...
Inlet opening, 22...Exit opening. FIG, 2゜Procedural amendment writing method) 1. Indication of the case 1985 Patent Application No. 118967 2. Title of the invention Machine pump 3. Person making the amendment Relationship with the case Applicant 4. Agent

Claims (13)

[Claims] (1) A mechanical pump having at least two stages, each containing an intermeshing rotor in a pump chamber, which extends through and is dry supported in a wall separating one pump chamber from an adjacent pump chamber. A rotor is attached to the shaft, and a duct device is provided for transferring the gas that enters the annular gap between the shaft and the bearing part of the shaft in a relatively high pressure region of the pump to a relatively low pressure region of the pump. A mechanical pump characterized by: 2. A mechanical pump according to claim 1, wherein the duct arrangement is arranged to transfer gas from a shaft seal in a relatively high pressure region of the pump chamber to a relatively low pressure region of the same chamber. (3) The duct arrangement is arranged to transfer gas from the shaft seal of the relatively high pressure region of the pump chamber to or into the gas inlet opening of that chamber. Mechanical pump according to paragraph 2. (4) The duct arrangement is arranged to transfer gas from the seal in the relatively low pressure region of the pump chamber to or into the gas inlet opening of that chamber. Mechanical pump according to item 3. 5. A mechanical pump according to claim 4, wherein the duct arrangement is arranged to create communication between the respective shaft seals of the relatively high pressure region and the low pressure region of the pump chamber. 6. A mechanical pump according to claim 1, wherein the duct arrangement comprises an annular groove provided in the partition of the pump chamber and at least partially surrounding the shaft. (7) A mechanical pump according to claim 6, wherein the annular groove completely surrounds the shaft. (8) The mechanical pump according to claim 6 or 7, wherein the duct device comprises another hole provided in the partition wall, which hole is connected to an annular groove surrounding the shaft. . (9) the hole connects annular grooves surrounding respective shaft seals of relatively high-pressure regions and low-pressure regions of the pump chamber;
A mechanical pump according to claim 8. (10) The mechanical pump of claim 9, wherein the hole communicates with an inlet opening of the pump chamber. (11) A mechanical pump according to any one of claims 1 to 10, wherein the duct device is provided in the pump chamber at the outlet end of the pump. 12. The mechanical pump of claim 11, wherein the pump chamber at the outlet end of the pump surrounds an intermeshing melon-shaped rotor. (13) A mechanical pump according to claim 11 or 12, wherein the pump chamber at the outlet end of the pump exhausts gas via a one-way valve.