CA2057067A1

CA2057067A1 - Bellow-type pump with a plurality of radially arranged bellows

Info

Publication number: CA2057067A1
Application number: CA 2057067
Authority: CA
Inventors: Norbert Hoehn; Hartmut Runge; Hans-Juergen Banfer
Original assignee: Individual
Current assignee: Siemens AG
Priority date: 1989-05-23
Filing date: 1990-05-08
Publication date: 1990-11-24
Also published as: EP0473616A1; WO1990014517A1

Abstract

(57) Abstract A bellow-type pump comprises a plurality of bellows (51) to (54) grouped radially about the drive axis and driven simul-taneously so that the torque is applied uniformly. Asymmetrical loading of the bellows, which reduces their service life, is prevent-ed by improved coupling of the eccentric movement of the drive shaft (34) with the bellows. The outlets (62) from the individual bellows can be connected in parallel or in series, as desired, so that a greater delivery volume or higher delivery pressure can be attained, depending on requirements. The pump housing (1) consists of a double-cross piece used as an assembly unit in ultra-high vacuum technology. To ensure complete evacuation of the pump, for example to allow subsequent introduction of ultrapure gases, spring-loaded valves (82) which block the direction of flow are maintained temporarily in an open position during normal operation. To this end, the closure bodies of the valves are made from a magnetic material and can be influenced by a magnet (84) mounted on the outside of the pump housing (1, 73), which is made from non-magnetic material. The valve returns to its closed position immediately the magnet (84) is brought into, and possibly stopped in, a remote position.

Description

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BELLOWS PUMP HAVING A_PLURALITY OF

RADIALLY DISPOSED FOLDING BELLOWS

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The present invention relates to a bellows pump, having a plurality of radially disposed bellows, around a common drive shaft provided with an eccentric and actuatable by means of separate piston rods secured to the eccentric, and having separate inlets and outlets for the pumped fluid.
~, In its German Utility Model 87 02 659, the present applicant has described an encapsulated bellows pump that can be used in particular to pu.mp ~9Xi~ Dr ~adioac~i~e flvids, or ; fluids for which increased demands in terms of purity are made.
This pump has a motor-driven shaft on which an eccentric is secured. In turn, a piston rod is pivotably connected to the eccentric and alternatingly contracts and expands the bellows.
The effect of the arrangement of the piston rod described is that not only an axial motion but a transverse motion as well is , imparted to the b&llows, causing an asymmetrical compression on i the bellows that can shorten its service life. The fact that the torque a}so to be imparted to the shaEt is rather inconstant ; over the course of one revolution of the shaft is also unfavorable.
A pump of the above-addressed type is known from US Patent 4,179,244, in which a number of bellows can be actuated .~: "
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'`~' '~" .' -` 2~7~7 si~ultaneously from a central shaft that is provided with an ; eccentric. However, since the piston rods are secured pivotably to the eccentric, lateral deflection of the eccentric occurs, ; which causes an asymmetrical compression of the bellows.
To prevent possible leakage, the passage of drive or adjusting devices through the housing wall is avoided completely, so that safe trapping of the pumped fluid is assured even if the bellows effecting the pumping action should break because of material fatigue. The housing of such a pump is preferably made of a corrosion-resistant or in other words austenitic steel, which is known to be nonmagnetic. Lines serving to deliver and remove the pumped fluid have suitably oriented check valves incorporated in them, which prevent the return ~low into the intake line when the bellows is pressed ; together and the return flow out of the pressure line when the bellows is relaxed. These check valves may take the form of elastic metal flaps, which in accordance with the desired operative direction are pressed against the valve seat as a result of their intrinsic spring properties.
If pumps of this type are to be used to pump high-purity gases, then the pumps must of course be reliably evacuated be~ore being put into operation, to avoid contamination of the gases with air ingredients. This evacuation is now hindered by the action of the valves described: Even in the case of evacuation via the pressure line, the valve built into this line will return prematurely to its closing position toward the end .
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~ ~0~70~7 of the evacuation process if there is even only a slight pressure difference between the interior of the housing and the suction chamber of the vacuum pump.
The object of the present invention is to create a bellows pump in which the disadvantages described above are avoidPd and which moreover has increased capacity with only insignificantly increased dimensions. Moreover, the pump should be adapted to changing requirements in terms of the pumpin~ pressure and pumping quantity. The object of the present invention is also a valve control that makes it possible, without sacrificing the integrity of the housing, to keep the valves and in particular the valve .In the pressure line open when the pump is stopped even if there is no longer any significant pressure drop from the interior to the outside across the valve seat.
The first of these objects is attained in that in that the individual piston rods are secured rigi.dly to the outer ring of the eccentric and are slidingly disposed in guides, which are fixedly attached with respect to a housing enclosing the pump.
As a result, the bellows are actuated practically only in the axial direction, so that thexe is no longer any asymmetrical compression of the bellows.
With a view to an economical form of the housing of such a pump described in further detail hereinafter, providing four bellows, each offset from one another by 90C, appears especially suitable. Since each of these bellows is located in a different stage of contraction or expansion, the torque to he .: - .
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r brought to bear by the drive is made largely constant. Both this drive and the housing containing the pump need to be reinforced or enlarged only insignificantly compared with the "one-cylinder pump" described above.
In an embodiment of the pump according to the invention, the outlets for the pumped fluid can be connected one after another in series, whereby a corresponding increase in the pumping pressure by n times (n = number of bellows) is attained.
In an alternative embodiment of this, the outlets for the pumped fluid can be connected side by side in parallel, whereby with a constant pumping pressure a corresponding multiplication of the pumping volume is attained. It is within the scope of the invention to embody the pump in such a way that both these connection possibilities can be achieved in alternation and arbitrarily.
A further improvement according to the invention of the pump described is that the length of the piston rods is variable. As a result, the attainable pumping pressure can be varied within certain limits, by varying the ratio of the bellows, contracted to a more or less large residual volume, to that of the expanded bellows. This also makes it easier to provide accurate adjustment of the various bellows to attain an overall constant pumping pressure.
In another feature of the invention, the bellows pump is disposed in a housing, which comprises a double-cross piece known per se in ultra-high-vacuum technology. In this kind of _,;~_ - ` ; - . . . . .. .

2 ~ 7 part, which is commercially available as a relatively inexpensive ready-made part, a particularly favorable arrangement of the various pump parts can be achieved, as will be described hereinafter in greater detail in the description of an exemplary embodiment.
In another feature of the invention, a bellows pump having intake and pressure lines that emerge from a fluid-tight housing and that can be blocked off by check valves against a return flow of the pumped fluid, wherein the valves are pressed into their closing position by spring pressure, is characterized in that the housing is fabricated from a nonmagnetic material while contrarily the closing bodies of the valves are fabricated from a magnetic material, and the latter can be opened by means of magnets attached movably to the outside of the housing.
In a further feature of the invention, the magnets have the shape of ring magnets disposed longitudinal displaceably on the lines. This assures the exact guidance of the magnets in a simple manner, specifically from a first position in which they do not affect the valves into a second position, to be defined by construction, in which they open the applicable valve.
Typically, the first position will be located at some distance from the pump housing. A further feature of the invention is therefore characterized in that the magnets can be fixed in a position remote from the valves, in which they remain as long as the valves do not have to be actuated separately in an evacuation procedure or for other reasons.

- 2~7~7 In accordance with the further feature of the invention, the magnets are magnetized in the axial direction, so that they will develop their maximal operative force in the same axial direction where the valves are intrinsically located.
An exemplary embodiment of the invention is shown in the drawing, specifically:
Fig. 1, a perspective view of the pump without its drive;
Fig. 2, a longitudinal axial section through it;
Figs. 3 and 4, circuit diagrams ~or the inlets and outlets of the pump; and ; Fig. 5, on a larger scale, the detail V of Fig. 2 with additional devices.
The pump is disposed in a housing 1 of the kind described as a so-called double-cross piece on page 11.8 of the catalog HV
200 issued by Leybold A. G. in November 1987. This shape results substantially from a central, spherical part 10, four connection pieces 11-14 formed onto it at right angles to one another, and two further connection pieces 15, 16, which are disposed vertically to the plane of the connection pieces 11-14.
Each of these connection pleces 11-16 has a flange 21-26 on its end, by way of which the double-crossi piece can be joined to adjoining pipelines and the like, not shown here.
A drive unit 30, not visible in Fig. 1, is secured tv the flange 25 and among other elements ~see Fig. 2) comprises an electric motor 31 having the necessary power, by means of which ~irst magnets 32 are set into rotation. These magnets carry .

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second magnets 33 with them, which are secured on a drive shaft 34 and are separated from the first magnets 32 in a fluid-tight ` manner by a hood 39 ~which in turn forms part of the housing 1);
as a result, it is possible to replace the motor 31 as needed without having to open the interior of the pump housing 1.
Secured to the drive shaft 34 in the center of the spherical housing part 10 is an eccentric inner ring 35, on which an eccentric outer rinq 37, separated by ball bearings 36, is rotatable. Piston rods 41-44 (42 and 44 are not ~isible here) are secured, distributed uniformly over the circumference of the outer eccentric ring 37; they are screwed to a variable depth in corresponding threads 38 in the outer eccentric ring 37 and are fixed in the desired positions by nuts 40. On their outer end, ~7 the pi.ston rods 41-44 are secured to corresponding bellows 51-54 (52 and 54 are not visible here), which are contracted and expanded again in alternation upon rotation of the drive shaft 34. The piston rods 41-44 are provided with slide blocks 46-49 (47 and 48 are not visible here), which slide in guides 91-94 (92 and 94 are not visible here~, which are attached in stationary fashion with respect to the housing 1; as a result, it is attained that the bellows 51-54 are loaded only axially and cannot buckle laterally outward under this load. The fluid to be pumped is aspirated or expelled again through inlets and outlets 61, 62, which are provided with check valves 81: 82 not shown until Fig. 5, which block in opposite directions. The inlets and outlets 61, 62 are attached in closure lids 71-74 (72 : . . ..
,i, .. . ~ i , , , ~ 2~57~7 and 74 are not visible here), which are secured to the flanges 21-24 with screws 70. While the flange 25 serves to secure the drive unit 30, the flange 26, not needed here, is closed with a blind lid 76.
Fig. 3 shows a series-connection of the pump and Fig. 4 a parallel connection; the same reference numerals are used in both diagrams. The bellows 51-54 actuated by the drive shaft 34 each pump separately via inlets 61 and outlets 62. A common main inlet line is marked 65, and a common main outlet line is marked 66. In the view of Fig. 3, the main inlet line 65 leads ; first to the inlet 61 of the bellows 54, through its outlet 62 into the inlet 61 of the bellows 53, then out of its outlet 62 and into the inlet 61 of the bellows 52, and finally out of its . outlet 62 into the inlet 61 of the bellows 51. At its outlet 62, the main outlet line 66 finally begins. A pressure increased by four, compared to the pumping pressure oE each individual bellows, for a constant pumping quantity, prevails in the l~ne 66.
In the view of Fig. 4, stub lines lead from the main inlet line 65 to each o~ the inlet valves 61 of the individual bellows 51-54. From their outlet valves 62, in turn, stub lines lead to the common outlet line 66, in which finally, four times the pumping quantity flows at unvaried pressure, compared with the capacity of a single bellows.
Each inlet 61 can be blocked by a first valve 81, and each outlet 62 can be blocked by a second valve 82. Both valves take `
2 ~ 6 7 the form of tongue valves, are made of a magnetic, resilient material, and are oriented such that the first valve 81 opens the way into the interior of the bellows 4 when the bellows is extended or in other words its volume is increased. At the same time, the second valve 82 is pressed against its seat and blocks the outlet 62. Upon a reversal. of the bellows motion, on the .- other hand, the first valve 81 returns resiliently to its seat, and the second valve 82 yields to the pumping pressure and opens the outlet 62. If the interior of the housing 1 is to be evacuated in order to remove any residual air that would contaminate the highly pure gas (such as helium) to be pumped later with this pump, a vacuum pump 83, only schematically shown here, will be connected suitably to the outlet 62. However, a ; truly adequate evacuation can take place only if the second valve remains open continuously at that time. This is done by the action of a ring magnet 84, which is longitudinally displaceably disposed on the outlet 62. In its position shown on the closure lid 73, its field lines act through the lid upon the second valve 82 and keep it in its open position. During normal pump operation, the ring magnet 84 assumes the position shown in dashed lines, in which it is restrained by an arbitrary locking means 85. In this position, so further significant magnetic forces act upon the second valve 82.

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Claims

CLAIMS:

1. A bellows pump, having a plurality of radially disposed bellows (51 - 54), around a common drive shaft (34) provided with an eccentric (35 - 37) and actuatable by means of separate piston rods (41 - 44) secured to the eccentric, and having separate inlets and outlets (61, 62) for the pumped fluid, characterized in that the individual piston rods (41 - 44) are secured rigidly to the outer ring (37) of the eccentric and are slidingly disposed in guides (91 - 94), which are fixedly attached with respect to a housing enclosing the pump.

2. The bellows pump of claim 1, characterized in that the outlets (61, 62) for the pumped fluid can be connected one after another in series.

3. The bellows pump of claim 1, characterized in that the outlets (61, 62) for the pumped fluid can be connected side by side in parallel.

4. The bellows pump of one or more of the foregoing claims, characterized in that the length of the piston rods (41 - 44) is variable.

5. The bellows pump of one or more of the foregoing claims, characterized in that it is disposed in a housing (1), which comprises a double-cross piece known per se in ultra-high-vacuum technology.

6. The bellows pump of one or more of the foregoing claims, having intake (18) and pressure (19) lines emerging from a fluid-tight housing (1) and capable of being blocked by check valves (20, 21) counter to a return flow of a pumped fluid, the valves being pressed into their closing position by spring pressure, characterized in that the housing (1) is fabricated from a nonmagnetic material, while contrarily the closing bodies of the valves (20, 21) are fabricated from a magnetic material, and the latter can be opened by means of magnets (23) attached movably to the outside of the housing.

7. The bellows pump of claim 6, characterized in that the magnets (23) have the shape of ring magnets disposed longitudinal displaceably on the lines (18, 19).

8. The bellows pump of claim 7, characterized in the magnets (23) can be fixed (24) in a position remote from the valves.

9. The bellows pump of claim 7 or 8, characterized in that the magnets (23) are magnetized in the axial direction.