GB2088956A - Rotary Positive-displacement Fluid-machines; Valves - Google Patents

Abstract

A machine, which may be a pump or a motor, has a substantially longitudinally inextensible flexible diaphragm clamped at its periphery between housing parts 12, 16 which support a rotary member 17 with members e.g. rollers 18, to deflect the diaphragm so as to form a working-fluid chamber 10 that travels between a fluid inlet 13 and a fluid outlet 14. At least three rollers (or other deflecting members) are provided, the sum of the distances along the diaphragm between the clamping points 12C, 16C and the deflectors 18 adjacent thereto and, depending upon the angular position of the rotary member, also between mutually adjacent deflectors being substantially constant, thus allowing a substantially longitudinally inextensible membrane to be used. The machine may be adapted for use as a selector valve by adding an intermediate port 20. <IMAGE>

Description

SPECIFICATION Material Handling Device The present invention relates to material handling devices such as pumps or motors.

Rotary pumps have already been proposed, the so-called peristaltic type, which use a flexible tube bent in the arc of a circle, the tube being squeezed by a plurality of rollers carried on a rotating member which makes contact with the tube at angularly spaced positions. This results in "slugs" of the fluid carried in the tube being carried forward from the inlet of the tube to its outlet.

Such pumps are particularly suitable for services which require the fluid being pumped to be kept isolated from the mechanism itself, but its disadvantage is that the tube, if not restrained, "walks" in the direction of the outlet. In consequence, the anchoring of the tube to prevent this is a problem which increases with the size of the tube and the viscosity of the fluid being pumped. It is a further disadvantage of this type of pump, that, when pumping "heavy" substances, such as concrete, the tube tends to collapse at the inlet end and it is necessary to evacuate the chamber in which the pump tube operates in order to overcome this tendency.

Another disadvantage of this type of pump is the large effort required to distort the tube, especially when heavy duty tubes are used, e.g. in pumping concrete, which results in low mechanical efficiencies.

Diaphragm pumps have also been proposed, such as in German Patent 6243, British Patent Nos. 208,477; 562,409 and United States Patent No. 2,794,400. These pumps include a housing having an internal surface, and a flexible resilient diaphragm mounted within the housing and secured thereto to form with the internal surface a chamber. First and second ports communicate with the chamber and a number of deflectors are each operable sequentially on the face of the diaphragm remote from the chamber, to urge the diaphragm towards the internal surface to form a closure or constriction which traverses the chamber. The closures or constrictions each move from the first to the second port, one of the closures being terminated after the succeeding closure has been initiated.A disadvantage of such a construction is that there is a necessity for the diaphragm to be resilient, to enable it to take up the necessary shapes, and there is a tendency for the diaphragm to flex towards the low pressure side of the pump, thus causing the "slug" of material being pumped to be of small volume. For this reason, pumps of this nature are limited both in their size and by the low rotational speeds at which they can operate.

It is now proposed, according to the present invention, for the pump configuration to be such that, as said deflectors move sequentially along a path on said surface of the diaphragm remote from the chamber, the sum of distances, measured along the diaphragm, between the clamping points of the diaphragm and the deflectors adjacent thereto, and, where appropriate, between the adjacent deflectors, remains substantially constant.

With such a construction, it is possible for the diaphragm to be substantially longitudinally inextensible, and preferably the diaphragm is substantially longitudinally inextensible.

The result of the construction of the present invention is that the length of the diaphragm remains substantially constant, whatever the position of the deflector means, and this prevents the diaphragm from collapsing from the reduced pressure zone or extending into the housing interior. This enables the pump to be operated at relatively high speeds and pressures for lighter materials including slurries. The pump is also capable of handling very heavy materials, such as mortars, and even concrete quite adequately.

The inextensibility can be produced by reinforcement fibres which extend longitudinally, that is in the direction of movement of the deflectors and transverse thereto. The reinforcement is preferably near the surface remote from the chamber, to keep the inextensibility as close as possible to the deflector means and to reduce wear.

In a preferred construction those portions over which the deflectors do not run are provided with a reinforcement in the form of fibres which extend at an angle, for example 45 , to the direction of the longitudinal direction, these providing strength but allow flexing of the diaphragm. An additional flexible sheet may be provided on this face remote from the chamber, and secured at least at the inlet port end, to provide a wear sheet for the deflectors and to give adjustment to cempensate for any inaccuracies in casting or in the thickness of the diaphragm and thus to ensure that the diaphragm fits snugly against the internal surfaces, when deflected by the deflector means.

In order to enable the diaphragm to be replaced readily, and to hold it securely, the diaphragm needs to be clamped properly. This is achieved by the housing including a first housing part having an internal surface and a peripheral first clamping surface surrounding the internal surface, and facing in substantially the same direction as the internal surface, and a second housing part having a peripheral second clamping surface clamping the periphery of the diaphragm against the first clamping surface.

The clamping surface on the first housing part is, preferably not flat, but includes a curved portion, which is preferably curved along an arc centred upon the axis of rotation of a rotary member carrying the deflector means, such as rollers. The clamping surface will thus be generally concave, as viewed perpendicular to the direction of movement of the deflector means, and the clamping surface on the second housing part is of cooperating convex form.

The diaphragm is preferably moulded so that its shape is such that it remains substantially undistorted when it is clamped in place and before the deflectors are placed in contact with the surface of the diaphragm remote from the internal surface of the housing. This construction means that the diaphragm only has to flex a small amount. As indicated the reinforcement may include, in addition to the longitudinal fibres, other fibres which are arranged at an angle thereto in other parts of the diaphragm to give strength, but do allow the slight flexing necessary for the diaphragm to distort without stretching in the direction of movement of the deflectors.

Further, to reduce wear it is possible to provide means to cause the rollers to continue rotation, even when they are not in contact with the diaphragm.

An additional port may be provided in the chamber at a location intermediate the first and second ports, means being provided to set the deflector means in predetermined positions relative to the ports whereby the device can be used not as a pump, but as a diverter valve for multiport diaphragm valve. This is a simple construction of valve and the arrangement could be such that the pump is operated, first of all, as a pump, with the intermediate port shut off, the intermediate port is then opened with the deflector in the fixed position, so that flow will continue to maintain a syphon.

In order that the invention may be more clearly understood, the following description is given, merely by way of example, reference being made to the accompanying drawings, in which: Figure 1 is a section through one embodiment of pump made according to the invention; Figure 2 is a section in two parts, the first on line A-A and the second on line B-B of the pump illustrated in Figure 1; and Figure 3 is a perspective view of a diaphragm as used in the pump of Figures 1 and 2.

Referring first to Figures 1 and 2 of the drawings, the pump comprises a first housing part 12 and a second housing part 1 6 mounted thereon. The housing part 12 includes the central dished portion having an upper internal surface 1 2A blending into a first port 13 and a second port 14. As can be seen from Figure 2, the curved portion 1 2A has associated therewith, on each side, a raised clamping surface 1 2B which faces generally upwardly, that is in the same direction as the surface 12A. Curved surfaces 1 2B end with a straight surface at 12C at each end which extends over the ports 1 3 and 14.

Thus, the clamping surfaces 1 2B and 12C completely surround the periphery of the internal surface 1 2A and the ports 13 and 14.

The second housing part 16 is provided with surfaces 1 6B which cooperate with the curved surfaces 1 2B and straight surfaces 16C which cooperate with the end portion of the surface 12C so that the surfaces 1 6B and 16C together define a second peripheral clamping surface. These clamping surfaces 12B,12C and 16B, 16C, are used to clamp the edge portions of a diaphragm 15 which is of the premoulded structure illustrated in Figure 3. As will be seen it has a corrugation at 15E on each side and a central portion 21 which is lower than the edge portions 21 A beyond the corrugations.The diaphragm is moulded with a reinforcement therein, including fibres 15C (Figure 3) which extend longitudinally, that is from left to right in Figure 1, in the central zone and includes other reinforcements 15D in other parts which are preferably at 45 , thus on the bias, to allow for some flexing, the longitudinal ones preventing extension in the longitudinal sense. These reinforcements are preferably placed on orjust below the upper surface at 1 SB.

Referring again to Figure 1 and 2, it will be seen that a rotary member 1 7 is rotatable about a central axis 1 7A and is mounted in bearings 25 in the second housing part 1 6. Member 1 7 carries three rollers 1 8 which can bear on the upper surface 1 5B of the diaphragm. The rollers urge the diaphragm at spaced locations towards, and preferably against, the upper surface 12A. In this condition, the surface 1 2A and the diaphragm lower surface 1 5A form a pumping chamber 10.

The particular manner in which the diaphragm is mounted enables it to be held very firmly and prevents any tendency of the diaphragm to "walk" as the rotary member 17 rotates in the direction indicated by the arrow.

Because of the configuration of the pump, the effective length of the upper surface of the diaphragm remains constant. That is, the sum of the distances, measured along the diaphragm, between the clamping surfaces 1 2B, 1 6B at one side of the pump, and the adjacent roller 18, and from that roller to the next roller, when two rollers are in contact with the diaphragm, and from the next roller to the other clamping surfaces 12B, 16B, remains constant regardless of the position of the rotor and regardless of whether one or two rollers are in contact. This means that the diaphragm need not elongate at all during the action of the rollers and it is for this reason that it is possible to provide the reinforcement in the diaphragm.The reinforcement in the longitudinal direction indeed prevents the diaphragm from elongating and the reinforcement arranged on the bias prevents too much distortion, but allows an adequate amount for the flexure of the diaphragm under the action of the rollers 18. As the rotary member 1 7 rotates, the constricted or closed off chamber 10 is moved from the inlet 13 to the outlet 54, and because there are at least three rollers 18, the capsule thus formed is always isolated from at least one of the ports. Because the sum of the distances mentioned above is constant, a positive pumping action can take place in an adequate manner. It will be appreciated that the closure caused by one roller is terminated after the succeeding closure is initiated.

It will be appreciated that the diaphragm clamping surfaces 1 2B, 1 6B are so arranged that they partially form arcs of a circle with substantially the same centre as the rotary member. The rollers 18 are shown as being freely rotatable, but it is contemplated that they could be caused to rotate continuously thus to reduce the wear on the upper surface. An additional wear sheet of flexible material may be secured above the diaphragm at the righthand side, as viewed in Figure 1, and extend over the full path covered by the rollers 18. This not only reduces wear, but can be used to adjust the thickness of the diaphragm to take up any manufacturing tolerances in the housing part 12.

The diaphragm is preferably moulded so that it naturally has the shape illustrated in Figure 3, that is with the lower and upper surfaces of the edge portions 21 A having the same shape as the clamping surface 1 2B and 1 6B respectively. Thus, as the roller moves, the amount of distortion will be first to one side and then to the other, without ever causing any excess distortion.

The amount of diaphragm material in the moulded and reinforced diaphragm on the surface length 15B which remains substantially constant at all positions of the rollers adjacent to the rollers is such that it is only slightly in excess of that which allows the rollers to distort the diaphragm while avoiding rupture, but does not allow the diaphragm to deform further under negative pressure. The reinforcement in the diaphragm is not elastic and is moulded to the diaphragm at or near the surface on which the rollers make contact. This not only reinforces the diaphragm to cater for negative and positive pressure developed during the pumping cycle, but also reduces wear on the diaphragm due to the action of the rollers.

If the pump is provided with the modification indicated in phantom, that is with the intermediate port 20 at the centre of the chamber 10, that is at the centre of the surface 12A, then the device can be used as a valve, by moving the member 17 to the position in which the rollers take up the position 18' and 18" as illustrated in phantom. This connects the port 20 to the port 14 and disconnects the port 1 3. A similar symmetrical position could be assumed in which the port 1 3 is connected to the port 20 isolating the port 14.It is contemplated that if one rotates the member 17 continuously to cause the pumping while shutting off the port 20, then the pump could be used to start off a syphon action, the pump then being moved to the other position communicating port 1 3 with port 20, allowing the syphon action to continue upon opening of the port 20.

It will be seen that the second housing part 16 is provided with a removable cover 26. One of the rollers 18 is also removably mounted on the member 1 7. The reason for this is that, because of the shaping of the diaphragm and the configuration of the pump, it is important to clamp the diaphragm around its full periphery before any of the rollers contact the diaphragm so that the diaphragm can take up its natural position without any distortion or strain thereon during the clamping. Thus, in order to mount a new diaphragm, the second housing part 1 6 is removed and the used diaphragm taken away and the new diaphragm put into position. The cover 26 is removed from the second housing part, and one of the rollers is then taken off.The member 1 7 is rotated until the other two rollers are at the top, that is so that the zone of the removed roller is at the bottom. The second housing part is then put in place and bolted down. The dimensions of the rotary member 1 7 are such that the zone adjacent where the roller which had been removed is located does not touch the diaphragm, so that during the clamping operation no disturbance of the diaphragm can take place. The rotary member is then rotated until the location of the removed roller is at the top and the roller put back in place whereafter the cover 26 can be fixed.

It has been found that unless this technique is used, the diaphragm is distorted and the pumping action possible with this pump reduces and indeed practically ceases.

It is thus important that the configuration of the pump should be chosen to give the necessary constant path length. This can be determined fully theoretically, but in practice it has been found possible to design the pump empirically by taking a piece of flexible inextensible material, such as cord, fitting around a model of the rotary member 1 7 and its rollers, and determining the position of the clamps which provide a fully tensioned cord at all times.

While the device has been described as a pump, it could equally well be used as a compressor or indeed as a motor.

The diaphragm must be flexible and may either be intrinsically substantially inextensible or can be rendered so by reinforcement. The reinforcement illustrated includes a central portion with fibres 15C extending longitudinally only. In practice, however, the reinforcement shown only at the sides at 1 5D will extend across the full width of the diaphragm and the central portion will have a reinforcement made of an open mesh fabric which includes the longitudinal fibres 15C and other fibres (not shown) at right angles thereto, making the diaphragm lateraliy inextensible.

Claims (1)

1. Claims

   1. A material handling device comprising a first housing part having an internal surface and a first peripheral clamping surface surrounding said internal surface and facing in substantially the same direction as said internal surface, a flexible diaphragm in a chamber forming face overlying said internal surface and said peripheral clamping surface, a second housing part having a second peripheral clamping surface shaped to overlie that part of the diaphragm overlying the first peripheral surface, effective to clamp said diaphragm sealingly against said first peripheral surface, whereby a chamber is formed between said chamber-forming face and said internal surface of said first housing part, first and second ports in said first housing part communicating with spaced portions of said chamber and at least three deflector members movabie longitudinally of the diaphragm sequentially on the face of said diaphragm remote from said chamber-forming surface to urge the diaphragm against or towards said internal surface to form a closure or constriction which traverses the chamber and to move the closure or constriction from one port to the other port, one such closure or constriction being terminated after the succeeding closure or constriction is initiated, the pump configuration being such that, as said at least three deflector means move sequentially along a path on said surface of the diaphragm remote from the chamber, the sum of distances measured along the diaphragm, between the clamping points of the diaphragm and the deflectors adjacent thereto and, where appropriate, between the adjacent deflectors remains substantially constant.

   2. A device according to claim 1, wherein said deflector means is mounted on said second housing part, whereby it can be removed when the clamping of said diaphragm is released.

   3. A device according to claim 1 or 2, wherein said first and second clamping surfaces are nonplanar.

   4. A device according to claim 2 or 3, wherein said deflector means comprise at least three deflectors mounted on a rotary member carried by said second housing part.

   5. A device according to claim 4, wherein the internal surface and portions of said peripheral surface are each arcs of circles centred on the axis of rotation of said rotary member.

   6. A device according to claim 4 or 5, wherein said deflector members are each rollers rotatably mounted on said rotary member.

   7. A device according to any preceding claim, wherein the diaphragm is moulded to a shape corresponding to the shape of the internal surface and portions of the peripheral surface, so that, when the diaphragm is placed on said peripheral surface and clamped it does not undergo any distortion.

   8. A device according to claim 7, wherein two longitudinal corrugations spaced from the longitudinal edges project over the surface remote from the chamber.

   9. A device according to claim 8, wherein a central portion of the width of the diaphragm is moulded to take up a position nearer the internal surface than the edge portion on either side thereof, to give the correct sum of distances measured along the diaphragm.

   1 0. A device according to any preceding claim, wherein a flexible sheet is interposed between the diaphragm and the deflector means.

   11. A device according to any preceding claim, wherein an intermediate port communicating with said chamber is located between said first and second ports.

   12. A material handling device substantially as hereinbefore described, with reference to, and as illustrated in the accompanying drawings.

   New Claims or Amendments to Claims filed on 25 February 1982 Superseded Claim 1 New or Amended Claims:

   1. A material handling device comprising a first housing part having an internal surface and a first peripheral clamping surface surrounding said internal surface, and facing in substantially the same direction as said internal surface, a flexible diaphragm having and a second housing part having a chamber-forming face overlying said internal surface and said peripheral clamping surface, said diaphragm being substantially longitudinally inextensible, a second peripheral clamping surface shaped to overlie that part of the diaphragm overlying the first peripheral surface, effective to clamp said diaphragm sealingly against said first peripheral surface, whereby a chamber is formed between said chamber-forming face and said internal surface of said first housing part, first and second ports in said first housing part communicating with spaced portions of said chamber and at least three deflector members movable longitudinally of the diaphragm sequentially on the face of said diaphragm remote from said chamber-forming surface to urge the diaphragm against or towards said internal surface to form a closure or constriction, which traverses the chamber and to move the closure or constriction from one port to the other port, one such closure or constriction being terminated after the succeeding closure.