US 3898022 A
A valveless rotary displacement pump comprising a cylindrical housing having inlet and outlet openings, a movable tubular membrane within said housing extending axially thereof with the forward edge of the membrane sealingly engaging the front wall of the housing, means sealing the membrane against the inner wall of the housing between the inlet and outlet openings, and a rotor mounted inside the membrane, said rotor pressing the membrane against the inner wall of the housing at substantially diametrically opposed axial lines, as the rotor rotates within the housing.
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Description (OCR text may contain errors)
[ 1 Aug. 5, 1975 7/1972 Rosenberg.....................l 417/477 X FOREIGN PATENTS OR APPLICATIONS 551.541 ltaly......l. 417/477 ABSTRACT A valveless rotary displacement pump comprising a 2 Drawing Figures Primary [;.\'u/mm'rC. Jr Husar Ass/stun! EmminerLeonard Smith Arm/7w Age/1! or FirmSalter 84 Michaelson cylindrical housing having inlet and outlet openings a movable tubular membrane within said housing extending axially thereof with the forward edge of the membrane sealingly engaging the front wall of the housing. means sealing the membrane against the inner wall of the housing between the inlet and outlet openings, and a rotor mounted inside the membrane said rotor pressing the membrane against the inner wall of the housing at substantially diametrically opposed axial lines, as the rotor rotates within the hous ing.
VALVELESS ROTARY DISPLACEMENT PUMP Inventor: Otto Lutz, Bienroder Weg 53, 33
Braunschweig. Germany Filed: July 17, 1973 Appl. No.1 379,929
Foreign Application Priority Data July 20 1972 Germany....,...l.W.........v...
Field of Search References Cited UNITED STATES PATENTS 8/1950 5/1959 11/1968 McMillan...
United States Patent Lutz l l l VALVELESS ROTARY DISPLACEMENT PUMP BACKGROUND AND SUMMARY OF THE INVENTION The present invention concerns a valveless rotary displacement pump comprising a cylindrical housing and a movable membrane arranged within the interior of the housing and extending axially thereof so that the forward edge of the membrane makes a tight seal against the front wall of the housing. and means sealing the membrane against the inner wall of the housing between the inlet opening and the outlet opening of the pump, and a rotor mounted inside the membrane pressing the membrane against the inner wall of the housing along at least two rotating lines axial to the casing.
Known pumps of this type usually include a rotor with two pressure rollers which press a membrane against two rotating lines axial to the casing by centrifugal forces or by the force of springs, in such a way that two rotating delivery pockets are formed between the membrane and the inner wall of the housing by means of which gases, liquids. or plastic solids-for instance, cement slurries-can be delivered from the suction to the pressure side of the pump. ln known pumps, the suction and pressure sides are separated from each other by means of a clamping device which holds a ledge formed in the membrane, or. in another case, the free ends of a membrane band which lie one upon another, stationary and at the same time seals the suction side of the pump from the pressure side along this stationary line axial to the casing.
Although this pump is simple in its fundamental construction and its manufacture is relatively cheap, known pumps of this type have not, up to the present time, proved successful in practice, since it is only possible to operate them at low r.p.m.s, and, thus, only low delivery powers can be achieved, The reason for this is that, especially at high r.p.m.s of the pump, the membrane is subjected to high peripheral forces and tends to tear rapidly. Under these conditions, tearing occurs chiefly in the region of the stationary clamping of the membrane by the known clamping devices. These clamping devices have an additional disadvantage that when the pressure rollers of the rotor roll across this position, the membrane is subjected to sharp bending at this point, which readily causes premature destruction of the membrane.
Another factor that makes prior art pumps of the above type not practical where fast-running characteristics are desired is that, up to the present, it has not proved possible to prevent vibration of the membrane, especially at high r.p.m.s.
The basic object of this invention is, therefore, to provide a pump of the type described above which can be operated at high r.p.m.s with correspondingly high powers of delivery and which has a sufficiently long working life in normal operation.
This object is achieved, according to the present invention, by fabricating the membrane in the form of a tube with a constant Wall thickness which is braced against the smooth surface of the inner wall of the housing between the inlet opening and the outlet opening of the pump, by means of a sealing strip with a smooth surface,
A primary advantage of the pump according to the present invention arises from the use of a membrane in the form of a tube. with no projections or thickened extensions. in conjunction with the method of bracing the membrane against the inner wall of the housing by the use of smooth surfaces, according to the invention. Bracing may occur along one or more lines axial to the casing and can be produced by one or more sealing strips. in either case, according to the invention. sharpedges clamps, which can easily cause damage to the membrane. are avoided.
it is advantageous that the sealing strip should press the membrane resiliently against the inner wall of the housing so that, on the one hand, the seal between the input opening and the output opening is insured while. on the other hand, the membrane can slip or move in a circumferential direction. In this way it is possible for the membrane to partially compensate for the cxces sively high peripheral forces. The friction between the membrane and the inner wall of the housing is also decreased by this arrangement.
As a result of this invention, dangerous vibrations of the membrane, especially in fast-running pumps, are avoided since the membrane in the form of a tube is continuously maintained under tensile pre-stress by means of tensioning elements arranged within the membrane. in a preferred form of the invention. these tensioning elements are formed at the sides of the seal ing strip in such a way that the transition between the tensioning surfaces of the sealing strip and the tensioning elements at its side is rounded off.
An important feature of this invention is the fact that the tubular membrane nowhere has a radius of curvature less than that imposed by the pressure rollers of the rotor. in this way, the working life ofthe membrane is prolonged, which is especially true when the radius of curvature of the rounding-off at the transistion between the tensioning surface of the sealing strip and the tensioning elements at the side is the same as that of the rollers of the rotor, and when the radius of curvature of this rounding-off and of the rollers is, respectively, greater than the least permissible bending radius of the membrane.
In a pump according to the present invention, the membrane consists of a tube of metal or of a synthetic material which is resilient to bending. Special advantages occur when the membrane is of multilayer construction, Such membranes may, for instance, be manufactured from a coiled steel band or fabricated from two or more tubes of synthetic material, for instance. which are pushed one inside the other. Membranes of multilayer construction, according to the invention, are capable of withstanding higher pressures in the delivery pockets of the pump and have the additional advantage that the seal between the front edge of the membrane and the front wall of the pump housing is considerably improved. Owing to the multilayer construction of the membrane, a seal of a labyrinth type is produced in this position.
Another advantage of the present invention is that the interior of the membrane is connected to the highpressure side of the pump. As a result of this, the membrane is better able to resist the pressure in the delivery pockets.
In summary, 1 produce a pump, according to the present invention, which can be operated at relatively high r.p.m.s, and thus has relatively high power of delivery, and whose membranes are long lasting in use. The pumps can be economically produced, since they require neither close tolerances in manufacture nor expensive construction of bearings or housing because of their practically complete mass balance.
Other objects, features and advantages of the invention will become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.
DESCRIPTION OF THE DRAWINGS In the drawing which illustrates the best mode presently contemplated for carrying out the present invention:
FIG. I is a cross section through a pump according to the invention with the rotor in a transverse position. and
FIG. 2 is a longitudinal section through the pump according to FIG. 1 with the rotor in a vertical position.
DESCRIPTION OF THE INVENTION The valveless rotary displacement pump, according to the invention, as illustrated, consists essentially of the pump housing 3. the rotor 4, and the membrane 5.
The housing 3 is closed by a front cover 6 and has an inlet opening 7 and an outlet opening 8 in the surface of its casing. The membrane is pressed, to provide a seal, against the inner wall of the housing along a fixed line axial to the casing by means of a sealing strip 9, fabricated in two parts.
Pressure rollers 10 rotatably carried by the rotor 4 provide rotating axial lines along which a seal is made between the membrane 5 and the inner wall of the housing 3. The axial sealing lines, the inner wa l of the housing 3, and the membrane 5 define delivery pocket ll, as can be most clearly seen in FIG. 1. PK]. 1 repre sents one extreme position of the rotor 4. in this position the delivery pocket 11 is sealed off from the inlet and outlet openings 7 and 8 and has the maximum suction volume which will be sucked in twice during each rotation of rotor 4. The delivery capacity of the pump, as illustrated, can, however, be further increased if the rotor axle 12 is mounted not, as illustrated, on the central axis of the cylindrical housing 3, but somewhat above this position. The suction volume of the pump will be increased by such an arrangement.
Another extreme position of the rotor is attained when the latter has reached the position shown in FIG. 2. In this position, the fixed axial sealing line is coinci dent with one of the rotating axial sealing lines so that the membrane is pressed against the inner wall of the housing 3 to form a seal at two positions only. The advantage of providing the two-part sealing strip 9, according to the invention, with tensioning elements 13 at the sides, is particularly apparent at this position of the rotor. The membrane 5 bears against a mounting support and is thus held continuously under a tensile pre-stress, so that any vibration of the membrane 5 is eliminated.
ln particular, it can be seen from FIG. 1 that the sealing strip 9, which is attached to the front wall 6 of the housing by means ofa tension anchor 14, has a smooth surfaced tensioning face 15, which is essentially parallel to the curved inner wall of the housing 3. The transitions from the tension face 15 of the sealing strip 9 to the tensioning elements 13 at the side is provided with rounded-off portions 16, which, in a preferred form of the invention, have a radius of curvature equal to the radius of curvature of the rollers 10. In this way the flexible membrane 5 is not subjected at any point to bending to a larger extent than is permissible. The membrane 5 can slip or slide between the tensioning face 15 and the inner wall of the housing 3 without breaking the seal between the suction side and the pres' sure side of the pump, so that the membrane is not subjected to excessive peripheral forces arising from the rotation of the rotor 4.
The membrane 5 is flexible and bendable but has no extensibility in a circumferential direction. it may be fabricated as an endless tube from metal or synthetic material, for example, snythetic material strengthened with glass fiber, and can be easily replaced in the pump according to the invention as it only needs to be pushed over the rotor 4 and the sealing strip 9 in the pump housing 3. An especially good seal between the forward edge of the membrane 5 and the front wall of the housing 3for example, the housing cover 6is produced when multiple-layer membranes are employed.
The rotor 4 of the pump according to the invention is fixedly mounted on the rotor axle 12 by means of a pin 17. The rotor axle 12 is mounted in the front wall of the housing 3 in roller bearings l8. It is obviously possible to use other types of bearings if desired. Rollers 10 are fixedly mounted in needle bearings 20 at the side ends of the transverse carrier 19 of the rotor 4. These needle bearings 20 may also be replaced by bearings of other types-for instance, slide bearings, carbon bearings or the like. In this way, the roller surfaces of the rollers 10 are fixed at a distance from the inner wall of the housing 3 which corresponds with the thickness of the membrane 5. It would be possible to mount the rollers 10 in bearings on the transverse carrier 19 of the rotor 4 so as to be movable in such a way that they are urged against the inner wall of the housing 3 by centrifugal forces or by the force of springs (not shown). However, the rollers 10 may also be advantageously mounted in fixed bearings on the transverse carrier l9 of the rotor 4. By correct adjustment of the rollers relative to the inner wall of the housing, the friction between the membrane and the inner wall of the housing can be considerably lessened so that the working life of the membrane is once again increased.
As further shown in FIG. 1, the interior of the membrane 5 is connected to the high pressure side of the pump through a passage 22 that extends through one of the end walls of the pump, whereby a pressure balance between the interior of the membrane and the pressure outlet 8 is always maintained.
While there is shown and described herein certain specific structure embodying the invention, it will be manifest to those skilled in the art that various modifications and rearrangements of the parts may be made without departing from the spirit and scope of the unde rlying inventive concept and that the same is not lim ited to the particular forms herein shown and described except insofar as indicated by the scope of the appended claims.
What is claimed is:
l. A valveless rotary displacement pump, comprising a housing formed with an interior chamber defined by an inner cylindrical wall and relatively flat end walls, inlet and outlet openings formed therein in said cylindrical wall in angular spaced apart relation, a movable membrane located in said housing having a tubular configuration and having a constant wall thickness, the longitudinal axis of said membrane being parallel to the longitudinal axis of said chamber, wherein the edges at both ends of the membrane sealingly engage the end walls of said chamber, the outer surfaces of said mem brane sealingly engaging the cylindrical inner wall of the chamber between the inlet and outlet openings thereof. a rotor rotatably mounted in said housing and located within the interior of the membrane. transversely spaced roller means mounted on said rotor for continuously engaging the interior surfaces of said membrane for urging the membrane against the cylindrical wall of the chamber along at least two rotating lines that are located in parallel relation to the axis of said cylindrical chamber, said sealing elements being secured to said end walls and engaging the inner surface of said membrane with a smooth surface for urging the membrane against the inner wall of the chamber between the inlet and outlet openings thereof to effect a seal between said openings, and allowing free circumferential movement of said membrane between the inner wall of said chamber and surfaces of said sealing elements.
2. A pump as claimed in claim l, the interior of said membrane communicating with the pressure side of said pump.
3. A pump as claimed in claim 1, said sealing element including tension elements that are joined thereto. said tension elements having rounded surfaces that engage the inner surface of said membrane for tensioning said membrane during rotation of said rotor and rollers mounted thereon.
4. A pump as claimed in claim 3, said tensioning elements being located at each circumferential end of said sealing element and the surface of said sealing element with which said membrane engages being rounded at said ends.
5. A pump as claimed in claim 4, a carrier mounted on said roller and extending transversely with respect thereto, said rollers being mounted on said carrier on opposite ends thereof.
6. A pump as claimed in claim 5, the radii of curvature of the rounded portions of the surfaces of said sealing element at its ends and tension elements that en' gage said membrane being substantially equal to the radii of curvature of the rollers of the rotor.