Diaphragm pump

Abstract

A pump (10) comprising an inlet (12), an outlet (14) and a pumping chamber (16) between the inlet (10) and the outlet (12). The pumping chamber (16) has first and second opposed interior pumping chamber surfaces (18, 20) extending from the inlet (12) to the outlet (14) in a pumping direction (PD). The pump (10) also has a flexible diaphragm (22) between the first and second pumping chamber surfaces (18, 20) which is adapted to substantially sealingly separate the first and second pumping chamber surfaces (18, 20) from one another. The diaphragm (22) has first and second layers (24, 26) adjacent the first and second pumping chamber surfaces (18, 20) respectively. A means (38) is also provided which induces substantially sinusoidal motion in the diaphragm (22) in the pumping direction (PD) without inducing relative movement between the diaphragm (22) and the pumping chamber (16) in the pumping direction (PD). The amplitude of the sinusoidal motion is approximately equal to the distance between the first and second pumping chamber surfaces (18, 20) in a direction normal to the pumping direction (PD) minus the distance between the sides of the diaphragm first and second layers (24, 26) adjacent the pumping chamber surfaces (18, 20). The length of the pumping chamber (16) in the pumping direction (PD) is greater than or equal to one wavelength of the sinusoidally shaped diaphragm (22) and the motion inducing means (38) is, at least in the region of the diaphragm (22) adjacent the first and second pumping chamber surfaces (18, 20), disposed within the first and second layers (24, 26) of the diaphragm (22).

Description

TECHNICAL FIELD

[0001] The present invention relates to a pump and particularly to a pump which utilises a travelling wave to drive a fluid.

BACKGROUND OF THE INVENTION

[0002] Known travelling wave pumps either used internal mechanical moving parts to drive a fluid or enclose the driven fluid within a flexible envelope in which cavities are formed and progressed by application of external mechanical moving parts. An example of the former are known as MONO (Trade Mark) pumps, which suffer from the disadvantage that the internal mechanical moving parts are exposed to possible damage whilst pumping corrosive fluids or from any abrasive solids suspended within the pumped fluids. An example of the latter are peristaltic pumps, which suffer from the disadvantage that the pressure that can be contained by the flexing envelope is limited which correspondingly limits the pumping pressure the pumps are able to generate.

OBJECT OF THE INVENTION

[0003] It is an object of the present invention to substantially overcome or at least ameliorate the disadvantages of the prior art pumps discussed above.

SUMMARY OF THE INVENTION

[0004] Accordingly, in a first aspect, the present invention provides a pump comprising:

[0005] an inlet;

[0006] an outlet;

[0007] a pumping chamber between the inlet and the outlet, the pumping chamber having first and second opposed interior pumping chamber surfaces extending from the inlet to the outlet in a pumping direction;

[0008] a flexible diaphragm between the first and second pumping chamber surfaces and adapted to substantially sealingly separate the first and second pumping chamber surfaces from one another, the diaphragm having first and second outer layers disposed adjacent the first and second pumping chamber surfaces respectively; and

[0009] means to induce substantially sinusoidal motion in the diaphragm in the pumping direction without inducing relative movement between the diaphragm and the pumping chamber in the pumping direction, the amplitude of the sinusoidal motion being approximately equal to the distance between the first and second pumping chamber surfaces in a direction normal to the pumping direction minus the distance between the sides of the diaphragm first and second layers adjacent the pumping chamber surfaces,

[0010] wherein the length of the pumping chamber in the pumping direction is greater than or equal to one wavelength of said sinusoidally shaped diaphragm and said motion inducing means is, at least in the region of the diaphragm adjacent the first and second pumping chamber surfaces, disposed within the first and second layers of the diaphragm.

[0011] The motion inducing means preferably includes at least one rotatable shaft extending in the pumping direction with a helical section in the region of the first and second pumping chamber surfaces, the helical section being disposed between the first and second layers of the diaphragm, the periphery of the helical section travelling along a circular path about its rotational axis.

[0012] The motion inducing means desirably includes two said rotatable shafts extending in the pumping direction, said shafts being spaced apart in said diaphragm and arranged for synchronous, and most preferably counter, rotation relative to one another.

[0013] The pump desirably has two opposed pump casing halves each having a recess therein respectively defining one of said two said pumping chamber surfaces.

[0014] In one form, when viewed in the pumping direction, the recesses are of a curved concave shape. In this form, the diaphragm includes longitudinal edges that extend in the pumping direction and the diaphragm is sealingly clamped between said casing halves along said edges.

[0015] In another form, when viewed in the pumping direction, the recesses are of a rectangular concave shape. In this form, the diaphragm includes longitudinal edges that extend in the pumping direction adapted to sealingly slide along opposed walls of the pumping chamber.

[0016] The pump preferably also includes at least one resilient axial beam within said diaphragm extending in a direction parallel to said pumping direction, said beam(s) compressed along its/their length(s) into a substantially sinusoidal configuration and adapted to deform adjacent regions of said diaphragm to said sinusoidal configuration. More preferably, the pump includes at least one pair of said resilient axial beams within said diaphragm, one of said beams in said pair(s) disposed between the motion inducing means and said first diaphragm layer and the other of said beams in said pair(s) disposed between the motion inducing means and said second diaphragm layer.

[0017] The pump can also include at least one resilient lateral beam within said diaphragm extending in a direction normal to said pumping direction, said lateral beam(s) biased to a substantially flat configuration and adapted to deform adjacent regions of said diaphragm to a curved configuration replicating an adjacent said pumping chamber surface when the beam(s) is/are driven towards said pumping chamber surface by said motion inducing means. More preferably, the pump can include a plurality of said lateral beams disposed in a parallel and spaced apart relationship between said pump inlet and outlet.

[0018] A spacing means is preferably provided within said diaphragm which is adapted to maintain said first and second layers of the diaphragm a constant distance apart.

[0019] The pump preferably also includes a drive means adjacent one of the inlet or outlet and a bearing journal adjacent the other of said inlet or outlet, the drive means adapted to rotate one end of said shaft and the journal adapted to support the other end of said shaft. More preferably, the drive means is adjacent the inlet and the journal is adjacent the outlet.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Preferred embodiment of the invention will now be described, by way of examples only, with reference to the accompanying drawings, in which:

[0021] FIG. 1 is a cross sectional side view of a first embodiment of a pump according to the invention;

[0022] FIG. 2 is a cross sectional end view of the pump shown in FIG. 1;

[0023] FIG. 3 is a cross sectional end view of a second embodiment of a pump according to the invention;

[0024] FIG. 4 is a cross sectional end view of a third embodiment of a pump according to the invention;

[0025] FIG. 5 is a cross sectional end view of a fourth embodiment of a pump according to the invention;

[0026] FIGS. 6A and 6B are bending moment diagrams of a lateral beam employed in fifth and sixth embodiments of pumps according to the invention;

[0027] FIGS. 7A to 7I are schematic end views of the fifth embodiment of a pump according to the invention employing lateral beams shown in FIG. 6B at varying positions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] FIG. 1 shows a cross sectional side view of a first embodiment of a pump 10 in accordance with the invention. The pump 10 comprises an inlet 12, an outlet 14 and a pumping chamber 16 therebetween. The pumping chamber 16 has first and second opposed interior pumping chamber surfaces 18 and 20 respectively, that extend from the inlet 12 to the outlet 14 in a pumping direction indicated by arrow PD.

[0029] A flexible diaphragm 22, preferably formed from a strong plastic material, is disposed between the first and second pumping chamber surfaces 18 and 20. The diaphragm 22 is adapted to substantially sealingly separate the first and second pumping chamber surfaces 18 and 20 from one another, in the region of the pumping chamber 16. The diaphragm 22 has first and second layers 24 and 26 respectively which are respectively adjacent the first and second pumping chamber surfaces 18 and 20 respectively.

[0030] The sealed separation of the first and second pumping chamber surfaces 18 and 20 by the diaphragm 22 is best described with reference to FIG. 2, which is a cross sectional end view of the pump 10 shown in FIG. 1. More particularly, FIG. 2 shows that the pump 10 has a metal pump casing formed from two opposed pump casing halves 28 and 30 that each have a curved concave recess therein respectively defining the two pumping chamber surfaces 18 and 20. When viewed in the pumping direction, the curved recesses give the pumping chamber 16 a substantially elliptical shape.

[0031] The diaphragm 22 includes longitudinal edges 32 and 34 extending in the pumping direction which are sealingly clamped, by bolts 35, between the casing halves 28 and 30. In this way, the first and second pumping chamber surfaces 18, 20 are sealed from one another. Also best seen in FIG. 2 is that the majority of the interior of the diaphragm 22 between the edges 32 and 34 is filled with a flexible spacing material 36, preferably a plastic concertina-like insert, which is adapted to maintain the first and second layers 24 and 26 of the diaphragm 22 a predetermined constant distance apart.

[0032] Returning to FIG. 1, the pump 10 also includes a means to induce substantially sinusoidal motion in the diaphragm 22 in the pumping direction without inducing relative movement between the diaphragm 22 and the pumping chamber 16 in the pumping direction. In the embodiment shown, the motion inducing means is in the form of a metal rotatable shaft 38 that is helical in shape in the region of the pumping chamber 16. The shaft 38 also includes one end in the inlet 12 which is connected to a rotational drive source, such as an electric motor (not shown), by a sealed right angled gear drive 40. The other end of the shaft 38 also includes a cylindrical section which is supported in a sealed bearing journal 42.

[0033] The helical section of the shaft 38 forces the flexible diaphragm into a substantially sinusoidal shape having an amplitude approximately equal to the distance between the first and second pumping chamber surfaces 18 and 20 in a direction normal to the pumping direction, minus the distance between the exterior sides of the first and second diaphragm layers 24 and 26 that are adjacent the first and second pumping chamber surfaces 18 and 20. The wavelength of the sinusoidally shaped diaphragm 22 is approximately equal to the length of the pumping chamber 16 such that a sealed volume between the peaks of the diaphragm is formed, as indicated by the hatched region 44.

[0034] In use, rotation of the shaft 38 causes the peaks and troughs of the diaphragm 22 to progressively move along the pumping chamber surfaces 18, 20 respectively, thereby driving the sealed volume 44 from the inlet 12 to the outlet 14 and inducing pumping of fluid contained therein from the inlet 12 to the outlet 14.

[0035] Generally speaking, the motion of the helical portion of the shaft 38 is transferred to the diaphragm 22 along the length of the helical portion. More particularly, the motion is transferred via a pair of resilient axial beams, which will be described in more detail below.

[0036] FIG. 2 shows a cross section through the pump 10 along line 2-2. As the helical portion of the shaft 38 is rotated the portion of the shaft shown travels, in the plane of FIG. 2, along a circular path indicated by dashed lines 48, thereby driving the diaphragm 22 adjacent that portion that from a first position (FIG. 2) where the first layer 24 of the diaphragm 22 is forced against the first pumping chamber surface 18 to an opposed second position in which the second layer 26 of the diaphragm 22 is forced against the second pumping chamber surface 20 then the first position and so on. This reciprocal movement will also be evident from FIGS. 6A to 6I, which will be described below.

[0037] As mentioned above, the diaphragm 22 also includes first and second resilient axial beams 52 and 54 which extend along the diaphragm in the pumping direction adjacent the region of the diaphragm 22 occupied by the helical portion of the shaft 38. The beams 52,54 are preferably formed from a stiff resilient material such as a hard plastic or spring steel. When straight, the beams 52, 54 are longer than a straight line between the inlet 12 and the outlet 14 of the pump 10. When they are compressed to fit between the inlet 12 and outlet 14 they deform to a substantially sinusoidal configuration adjacent the helical portion of the shaft 38. The resilient nature of the compressed beams 52 and 54 serves to assist the diaphragm 22 in maintaining its sinusoidal shape and therefore a continual sealing front against the first and second pumping chamber surfaces 18, 20.

[0038] FIG. 3 is an end cross sectional view of a second embodiment of a pump 60 according to the invention. The pump 60 is similar to the pump 10 and like reference numerals have been used to denote like features. The primary difference between the pumps 60 and 10 is that the pump 60 includes bearings, in the form of five roller sleeves 62 around the shaft 38, to provide a rolling action, and thus reduce friction, between the shaft 38 and the axial beams 52 and 54.

[0039] FIG. 4 is an end cross sectional view of a third embodiment of a pump 70 according to the invention. The pump 70 is similar to the pump 10 and like reference numerals have been used to denote like features. The primary difference between the pumps 70 and 10 is that the pump 70 includes a pair of synchronous counter-rotating shafts 38 disposed in the diaphragm 22 in a spaced apart relationship and two corresponding pairs of axial beams 52 and 54. The increased number of drive shafts 38 further enhances the sealing between the diaphragm 22 and the first and second pumping chamber surfaces 18 and 20, thereby allowing higher pumping pressures to be generated.

[0040] FIG. 5 is a cross sectional end view of a fourth embodiment of a pump 80 according to the invention. Again, like reference numerals used in describing the pump 10 will denote like features with respect to the pump 80. The casing halves 28 and 30 of the pump 80 have concave recesses that are rectangular in shape that together define a pumping chamber 16 of substantially rectangular cross section, when viewed in the pumping direction.

[0041] In the pump 80, the sealing between the first and second pumping chamber surfaces 18 and 20 by the diaphragm 22 is accomplished by the longitudinal edges 32 and 34 of the diaphragm maintaining a sliding sealing relationship with the side walls 82 and 84 of the pumping chamber 16.

[0042] FIGS. 6A and 6B will be used to describe the effect of applying a bending moment M upon a beam B. Generally speaking, when a bending moment M is imposed upon a beam B it flexes to produce a curve having a radii of curvature at points along its length which depend on the bending moment applied at that point. If the otherwise unrestrained flexing of the beam B is restrained by a surface, a reaction force is produced at those points of restraint.

[0043] FIG. 6A shows a bending moment M applied by rotating the beam B in opposite senses at each of its ends. As a result, the unrestrained radius of curvature R will be constant along the length of the beam. As illustrated in FIG. 5B restraint of the flexing of the beam B by a surface S, in which the local radius of curvature increases at each successive point towards the centre from each side, introduces a local distributed reaction force per unit length of arc p between the restrained beam and the surface. The rate of change of that increase in rate of curvature R with change of position towards the centres from each side determines the distribution of the reaction force p between the flexed beam B and the surface S.

[0044] However, the bending moment need not be applied only at the ends of the beam B. In a fifth embodiment of the invention, which is a variation of the first and second embodiments, lateral resilient beams are included in the diaphragm 22. A bending moment will arise in a beam from a force being applied to its centre, thereby pushing the beam against the surface S, as shown by arrow A in FIG. 6B. A force equivalent to A is generated by the shaft 38 shown in FIGS. 1 and 2 and FIG. 3.

[0045] A sixth embodiment of the invention (not shown) is a variation of the third embodiment. A bending moment will arise from a force being applied to two points equally distant from the centre of the beam which push the beam against the surface S, as shown by the arrows B in FIG. 6B. Such forces B are generated by the two shafts 38 shown in FIG. 4.

[0046] FIGS. 7A to 7I show schematic cross sectional end views of the fifth embodiment of a pump 90 utilising first and second resilient lateral beams 92 and 94, which are of similar construction to the axial beams 52,54.

[0047] The beam 92 is disposed between the first surface 24 of the diaphragm 22 and the axial beam 52. The beam 94 is disposed between the second surface 26 of the diaphragm 22 and the axial beam 54. FIGS. 7A to 7I show the position of a point of the helical portion of the shaft 38 in 45° increments as it completes one rotation about path 48. The lateral beams 92 and 94 are respectively and reciprocally driven towards the first and second pumping chamber surfaces 18 and 20 and, as the beams have a natural tendency to be in a substantially flat configuration, when they are pressed against the pumping chamber surfaces 18 and 20 they assist in forcing the portion of the diaphragm 22 adjacent the beam 92 or 94 to deform to a curved configuration replicating the adjacent pumping chamber surface 18 or 20. This improves sealing therebetween which again improves pumping pressure.

[0048] The primary advantage of the invention is it provides a travelling wave pump in which none of the mechanical moving parts used to drive the pump are exposed to contact with the fluids being pumped or any material suspended therein. This improves the mechanical life of the components generally and also provides the pump with particular suitability for transporting of abrasive, corrosive or otherwise component damaging material. Also, as the mechanical moving parts are sealed within the diaphragm then the diaphragm can be filled with a lubricant for the mechanical moving parts that will remain separated from the material being pumped.

[0049] Although the invention has been described with reference to the preferred embodiments, it will be appreciated by the skilled in the art that the invention can be embodied in many other forms. As an example, whilst embodiments have shown the use of one or two drive shafts and five bearings, any number of shafts/bearings can be placed within the diaphragm. Further, although the embodiment showed a sinusoidally shaped diaphragm with a wavelength equal to the length of the pumping chamber, the diaphragm and pumping chamber can be configured such that multiple wavelengths of diaphragm are disposed within the pumping chamber. Also, whilst the embodiments have been described with a pumping direction from an inlet towards the outlet it should also be appreciated that reversing the direction of rotation of the shaft also reverses the pumping direction and hence the inlet becomes the outlet and the outlet becomes the inlet. Finally, the gear drive need not be a sealed unit inside the inlet of the pump. An alternative is an external drive mechanism connected to the shaft through a sealed opening in the pump casing.

Claims

1. A pump comprising:

an inlet;

an outlet;

a pumping chamber between the inlet and the outlet, the pumping chamber having first and second opposed interior pumping chamber surfaces extending from the inlet to the outlet in a pumping direction;

a flexible diaphragm between the first and second pumping chamber surfaces and adapted to substantially sealingly separate the first and second pumping chamber surfaces from one another, the diaphragm having first and second outer layers disposed adjacent the first and second pumping chamber surfaces respectively; and

means to induce substantially sinusoidal motion in the diaphragm in the pumping direction without inducing relative movement between the diaphragm and the pumping chamber in the pumping direction, the amplitude of the sinusoidal motion being approximately equal to the distance between the first and second pumping chamber surfaces in a direction normal to the pumping direction minus the distance between the sides of the diaphragm first and second layers adjacent the pumping chamber surfaces,

wherein the length of the pumping chamber in the pumping direction is greater than or equal to one wavelength of said sinusoidally shaped diaphragm and said motion inducing means is, at least in the region of the diaphragm adjacent the first and second pumping chamber surfaces, disposed within the first and second layers of the diaphragm.

2. The pump claimed in claim 1, wherein the motion inducing means includes at least one rotatable shaft extending in the pumping direction with a helical section in the region of the first and second pumping chamber surfaces, the helical section being disposed between the first and second layers of the diaphragm, the periphery of the helical section travelling along a circular path about its rotational axis.

3. The pump claimed in claim 1 or 2, wherein the motion inducing means includes two said rotatable shafts extending in the pumping direction, said shafts being spaced apart in said diaphragm and arranged for synchronous rotation relative to one another.

4. The pump claimed in any one of the preceding claims, further including two opposed pump casing halves each having a recess therein respectively defining one of said two said pumping chamber surfaces.

5. The pump claimed in claim 4, wherein, when viewed in the pumping direction, the recesses are of a curved concave shape.

6. The pump claimed in claim 5, wherein said diaphragm includes longitudinal edges that extend in the pumping direction and the diaphragm is sealingly clamped between said casing halves along said edges.

7. The pump claimed in any one of claims 1 to 4, wherein, when viewed in the pumping direction, the recesses are of a concave substantially rectangular shape.

8. The pump claimed in claim 7, wherein said diaphragm includes longitudinal edges that extend in the pumping direction adapted to sealingly slide along opposed walls of the pumping chamber.

9. The pump as claimed in any one of the preceding claims, further including at least one resilient axial beam within said diaphragm extending in a direction parallel to said pumping direction, said axial beam(s) compressed along its/their length(s) into a substantially sinusoidal configuration and adapted to deform adjacent regions of said diaphragm to said sinusoidal configuration.

10. The pump as claimed in claim 9, including at least one pair of said resilient axial beams within said diaphragm, one of said beams in said pair(s) disposed between the motion inducing means and said first diaphragm layer and the other of said beams in said pair(s) disposed between the motion inducing means and said second diaphragm layer.

11. The pump as claimed in any one of the preceding claims, further including at least one resilient lateral beam within said diaphragm extending in a direction normal to said pumping direction, said lateral beam(s) biased to a substantially flat configuration and adapted to deform adjacent regions of said diaphragm to a curved configuration replicating an adjacent said pumping chamber surface when the beam(s) is/are driven towards said pumping chamber surface by said motion inducing means.

12. The pump as claimed in claim 11, further including a plurality of said lateral beams disposed in a parallel and spaced apart relationship between said pump inlet and outlet.

13. The pump as claimed in any one of the preceding claims, further including spacing means within said diaphragm adapted to maintain said first and second layers of the diaphragm a constant distance apart.

14. The pump as claimed in any one of claims 2 to 13, further including a drive means adjacent one of the inlet or outlet and a bearing journal adjacent the other of said inlet or outlet, the drive means adapted to rotate one end of said shaft and the journal adapted to support the other end of said shaft.

15. The pump as claimed in claim 14, wherein said drive means is adjacent the inlet and said journal is adjacent the outlet.