JPH04259691A - Mechanical pump - Google Patents

Abstract

PURPOSE: To facilitate pump assembling by providing a first main body portion housing a supporting/control/driving means for driving a shaft synchronously in an opposite direction, and protruding the shaft from the first main body portion to a second main body portion where a pump chamber is located. CONSTITUTION: This pump is operated by vertically directed shafts 2 and 3. In other words, a lower (first) main body portion houses a motor 13 for driving bearings 4 to 7, a timing gear 12 and the shafts 2 and 3 as supporting/control means synchronously in opposite directions, and the shafts 2 and 3 are protruded from the lower main body portion 1 to an upper (second) main body portion 21. Thus, the assembling of an upper pump main body composed of an inner wall 17 and a stator outer wall component 16 is carried out together with a sealing component, and then attached to the upper portion 21. Thus, the assembling of the pump is facilitated.

Description

[Detailed description of the invention]

0001

TECHNICAL FIELD This invention relates to mechanical pumps, and more particularly to mechanical pumps having at least a pair of interdigitated rotors, particularly of the type known as "claw" rotors, or "Northey" rotors.
A mechanical vacuum pump incorporating a rotor having a shape.

0002

BACKGROUND OF THE INVENTION Mechanical vacuum pumps of the type described above generally have one rotor of each pair mounted on a first common shaft and the other rotor of each pair mounted on a second common shaft. The shafts are positioned within the pump body and the rotors attached to the shafts are held in correct phase relationship by gears at one end of each shaft and by bearings generally positioned at each end of each shaft. The shafts are thus arranged to rotate synchronously in opposite directions and fit between each pair of rotors, usually without contact.

In single-stage pumps, a pair of rotors is forced to rotate in the manner described above within a single chamber. Generally, however, this type of pump is multi-stage, with each pair of rotors operating in respective chambers connected by ports in the walls of adjacent chambers. According to the disclosure of British Patent Specification No. 2,111,126, pairs of rotors in adjacent chambers are advantageously mounted on their respective shafts in opposite orientations with respect to pairs in the next chamber; This provides better overall length and positioning of the ports, particularly the rotors, within the pump compared to pumps that mount the rotor pair in the same orientation within the shaft.

Typically, this type of pump is operated with a pump chamber free of oil and lubricants, with a motor driving one of the shafts, a timing gear (or something else) providing synchronous rotation of the shaft, and a pump chamber that is free of oil and lubrication. The oil or lubricant associated with the bearings that hold them in place within the body is kept away from the pump chamber. Generally, pumps are operated with horizontally oriented shafts or with vertically oriented shafts. In some cases, for example, in semiconductor vacuum processes such as CVD and other particle-generating processes, horizontal operation is preferred because it increases reliability during long-term operation. In other cases, a vertical arrangement of the shaft is often preferred, for example when exhausting vapors that tend to condense or liquefy during the pumping process.

This type of pump typically has a bearing at the end of each shaft associated with the motor and timing gear, and an additional bearing at the other end of each shaft to position the rotor between the respective set of bearings. There is. The present invention relates to an improved vacuum pump that specifically uses a pump primarily designed to operate with a vertically oriented shaft.

[0006]

However, this type of vacuum pump is generally expensive to manufacture, especially when three or more stages are required to obtain the desired vacuum. A significant portion of the cost is precisely mounting each pair of rotors on their respective shafts so that each pair of rotors fits closely together without contact, and operating within the volume of an associated chamber within the pump housing. Depends on need.

The invention also simplifies manufacturing and assembly;
The present invention relates to an improved pump that can reduce costs.

[0008]

SUMMARY OF THE INVENTION In accordance with the present invention, there is provided a mechanical vacuum pump comprising at least two stages and having a pair of interdigitated rotors operating within a pump chamber associated with each stage. Each pair is on a respective shaft extending through the chamber and rotatably arranged in opposite angular directions, the pumps having a plurality of shafts housing support, control and drive means for synchronously driving the shafts in opposite directions. 1
A mechanical vacuum pump is provided, characterized in that it has a body part, the shaft projecting from the first body part into a second body part in which a pump chamber is located.

Preferably, the support, control and drive means each consist of a bearing, a gear and a motor. Advantageously, all support, control and drive means are housed within the first body part and sealed there to the second body part. Preferably the drive means comprises a motor. Such a seal structure can be used with any type or configuration of rotor.
It is beneficial with respect to maintaining a "clean" environment in the vicinity of the pump chamber.

[0010] The pump of the present invention has associated with each shaft,
Preferably, the bearing has two (or more) spaced apart bearings, and the shaft portion is housed within the first body portion. Usually one of these bearing means (
The lower side) is positioned at one end of the shaft to allow axial movement of the shaft, in particular to allow for thermal expansion, while the other (upper side) is positioned as close as possible to the second body part (but not the first body part). (within), particularly the axial position of the shaft.

[0011] In such a case, it is preferable not to support the part of the shaft within the second body part (thus avoiding lubrication etc. which is essential in connection with bearings), and therefore:
Shaft configuration is "cantilevered" or "overhang"
It can be considered that the design of For ease of manufacture, the pump of the present invention preferably has an integral rotor assembly associated with each shaft.

In one preferred embodiment, the multi-stage rotor assembly and its shaft are integrally molded as a single piece from, for example, an aluminum alloy body. In certain other preferred embodiments, the multi-stage rotor assembly is attached to a non-integral shaft made of a material such as steel, for example by press fit, shrink fit, or bolting.

A preferred embodiment of the invention has individual inner wall parts so as to define at least some of the dividing walls between the pump chambers, and preferably to form at least part of the outer wall of the pump chambers. Assembly of the pump is facilitated by having the pump body close to the rotor or second body part so as to have separate stator parts.

[0014] In such a preferred embodiment of the invention, the inner wall part and the stator part are conveniently assembled alternately around individual rotor pairs of respective aligned shafts during assembly of the pump. Most preferably, each inner wall part is split into two parts, for example, so that each inner wall part can be mounted directly around the aligned shaft during assembly of the pump.

In the most preferred embodiment, the pump is designed to operate with a vertically oriented shaft. That is, the lower (first) body portion houses associated support and control means, bearings, timing gears, and means for synchronously driving the shaft in opposite directions;
The shaft projects from the lower body portion to an upper (second) body portion. Therefore, the assembly of the upper pump body consisting of the inner wall part and the stator outer wall part, together with the associated sealing parts, is carried out directly and the upper part is then installed.

Advantageously, the pump inlet is housed in such an upper part, and the inner wall part has slots through which the exhaust gas flows through the individual chambers of the pump to the outlet, which is preferably located in the lower region of the pump body. or other ports in general. Overall, the pump of the present invention is designed to have optimal operating characteristics in conjunction with a rotor pair with oppositely oriented adjacent pairs in a preferred embodiment, with a simple Allows for generally short, duct configurations. The pump of the present invention is a multi-stage pump in which the rotor pair has a completely "claw" shape.
It is preferable to mainly design, but it is not limited to this.

For purposes of illustrating the invention only, the invention will now be described with reference to the accompanying drawings, in which:

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, the pump of the invention comprises a lower body part 1 in which shafts 2 and 3 are positioned by end bearings 4, 5 and positioning bearings 6, 7, respectively. . The upper end of shaft 2 is
four individual "claw" rotors 8, 9, 10,
11, and furthermore, the upper end portion of the shaft 3 is
four individual "claw" rotors 8', 9', 10',
11' is integrally molded. Each pair of rotors 8, 8';
9,9';10,10' and 11,11' are arranged rotatably about their respective shafts in a manner known as a "Northe" pair. The rotation of the shafts 2, 3 in respective bearings 4; 5 and 6; 7 is controlled by a pair of timing gears 12;
and is driven via the shaft 2 by the drive means 13,
This drive means 13 is actuated by belt means (not shown) which engage an annular groove 14 in the drive means.

The annular central body portion 15 is connected to the lower body portion 1.
, surrounding the bearing means 6, 7 and sealed to the lower body part 1 by an O-ring. The upper body part is formed from individual circular stator parts 16 alternating with individual inner wall parts 17, which are fixed to the central body part 15 and to each other by a series of O-rings.

The shape of the individual stator parts 16 is most clearly shown in FIG. 2 together with the pair of rotors 11, 11', which are designed to "sandwich" the inner wall part 17 between adjacent stator parts. It is located rotatably about the respective shaft 2, 3 within a hole 18 which intersects the flange located at the shaft 2, 3. The shape of the individual inner wall parts 17 is shown most clearly in FIG. Each inner wall component 17 is
During assembly, the two parts are inserted around the shafts 2, 3 and then "sandwiched" between adjacent stator parts 16. In addition to the split circular hole 19 for receiving the shaft 2, the inner wall part has another hole 2 enlarged to act as a transport port between the chambers on each side of the part, for receiving the other shaft 3.
has 0.

The position of this enlarged hole 20 is opposite to the smaller hole 19 in the adjacent inner wall part, so that in use the port provided by the enlarged hole 20 allows the flow of exhaust fluid in the direction of the arrow in FIG. Become. In an alternative stator construction, the individual stators 16 and inner wall parts 17 may all be integral or axially split (as part 17) to form a two-part stator.

[0022] An upper body portion 21 is positioned above the uppermost stator part 16 and sealed thereto by another O-ring. This upper body portion has a pump inlet 22 configured therein. This arrangement therefore forms four pump chambers separated by an inner wall part 17 in which the rotor pair operates. Exhaust gas pumped from the inlet passes through each of the four chambers to the central body portion 15.
It exits from the outlet 23 located at. In particular, there are no bearings or other parts requiring lubrication (or anything else) in conjunction with the upper body part, ie within the pump chamber.

Reference is now made to FIG. 6, which depicts another pump of the present invention having a construction generally similar to that shown generally in FIGS. 1-5. However, with this pump, the first
The rotor assembly 30 associated with the shaft 31 is also integrally molded, but is not integral with the shaft 31. Instead, rotor assembly 30 is attached to shaft 31 by bolts 32 and washers 33 that engage circular cavities 34 in the top surface of rotor assembly 30 and thread into threaded holes in shaft 31. Again, there is no bearing associated with the upper end of the shaft.

Another rotor assembly 35 associated with second shaft 36 is similarly constructed and similarly attached to second shaft 36 by another bolt 37 and washer 38. 7, this figure is very similar to the pump of FIG. 6, but with the shaft bearings, timing gear and drive motor all housed in the lower body part 1, and the upper body housing the pump chamber therein. Figure 3 shows another pump of the invention sealed against the parts.

FIG. 7 shows, in particular, that the interior of the lower (first) body part 1 is sealed by shaft sealing means in the form of a piston ring 39 around the shaft 2 and by shaft sealing means in the form of a piston ring 40 around the shaft 3. means for sealing against the second body portion. Positioned within the lower body part 1 are a pair of timing gears 12 mounted on respective shafts, and a motor 41 arranged to drive the shaft 2 is provided with an annular fixed winding 42 and, in use, rotates the part 43. Rotate.

With the use of such a sealed lower body section, the upper body section has four pump chambers free of oil or lubricant associated with bearings 4, 5, 6, 7, timing gear 12 and electric motor 41. can be accommodated. Overall, the pump of the present invention provides an effective design of a dry vacuum pump that is particularly simple in construction and maintenance. The materials used for the various parts may vary depending on the size and end use of the pump. However, generally iron, steel and aluminum or aluminum alloys are suitable for the rotor assembly and associated case and shaft. However, in the case of aluminum or aluminum alloys, especially for heavy duty pumps, the lower end of the shaft, i.e. the part remote from the integral rotor assembly,
It must be made of strong material such as steel. Steel (or other) and aluminum parts are keyed together in a variety of known ways.

In all cases, the invention is particularly suited for use in multi-stage pumps using "claw" type rotors in each stage. However, particularly in pumps where integral rotor assemblies are not made on each shaft, rotor combinations, including, for example, root chamber and claw chamber combinations (particularly with a root chamber adjacent to the pump inlet) It can be used in the present invention.

[Brief explanation of the drawing]

FIG. 1 is a schematic vertical sectional view of a pump of the present invention.

2: Line II-II of FIG. 1, specifically showing a pair of rotors; FIG.
FIG.

FIG. 3: Line III of FIG. 1, showing in particular the two-part inner wall part;
-III (on the scale of FIG. 2);

4 is a perspective view of the single shaft and integrally molded rotor of the pump of FIG. 1 in isolation; FIG.

5 shows the two shafts of the pump of FIG. 1 in a synchronous position and the corresponding molded rotor in isolation; FIG.

FIG. 6 is a longitudinal sectional view of a second pump of the present invention.

FIG. 7 is a longitudinal sectional view of a third pump of the present invention.

[Explanation of symbols]

1 Lower main body part 2, 3 Shaft 4, 5 End bearing 6, 7 Lower bearing 8, 9, 10, 11 Rotor 12 Timing gear 13 Driving means 14 Annular groove 15　Annular central body part 16 Stator parts 17 Inner wall parts 18 Boa 19, 20 holes 21 Upper body part 22 Pump inlet 23 Outlet 30 Rotor assembly 31 First shaft 35 Rotor assembly 36 Second shaft 39, 40 Piston ring

Claims (9)

[Claims] 1. A mechanical vacuum pump comprising at least two stages and having a pair of interdigitated rotors operating within a pump chamber associated with each stage, each pair of rotors extending through the chamber and opposite Located on each shaft rotatably arranged in an angular direction, the pump provides support, control and support for synchronously driving the shafts in opposite directions.
A mechanical vacuum pump, characterized in that it has a first body part containing drive means, the shaft projecting from this first body part into a second body part in which a pump chamber is located. 2. The mechanical pump according to claim 1, wherein the supporting, controlling and driving means comprises a bearing, a gear, and a motor. [Claim 3] All supporting, controlling, and driving means are connected to the first
Mechanical pump according to claim 1 or 2, characterized in that it is housed within the body part and sealed therein to the second body part. 4. A mechanical pump according to claim 1, wherein the pump has an integral rotor assembly associated with each shaft. 5. A mechanical pump according to claim 1, wherein the rotor assembly and its shaft are integrally molded as a single piece. 6. A mechanical pump according to claim 1, wherein the rotor assembly is attached to a non-integrally formed shaft. 7. The inner wall part of the second body part and the stator part are assembled alternately around individual rotor pairs of respective aligned shafts during assembly of the pump. A mechanical pump described in any of the above. 8. Each inner wall component is mounted directly around the aligned shaft during assembly of the pump.
The mechanical pump according to any one of claims 1 to 7, characterized in that it is divided into parts. 9. Mechanical pump according to claim 1, characterized in that the pump is designed for operation with a vertically oriented shaft.