WO2006027548A1

WO2006027548A1 - Rotary pump with resiliently deformed seal

Info

Publication number: WO2006027548A1
Application number: PCT/GB2005/003300
Authority: WO
Inventors: Richard Paul Hayes-Pankhurst; Graham Keith Lacy; Christopher Earl Nightingale
Original assignee: Carbonate Ltd; PDD Innovations Ltd
Current assignee: Carbonate Ltd; PDD Innovations Ltd
Priority date: 2004-09-07
Filing date: 2005-08-25
Publication date: 2006-03-16
Anticipated expiration: 2007-03-07
Also published as: CN101027484B; IL181393A; JP2008512595A; EP1787027A1; MX2007002719A; JP5053848B2; ES2453494T3; IL181393A0; USRE44841E1; USRE47590E1; GB0419848D0; US20060051228A1; CN101027484A; EP1787027B1; CA2578296A1; US7674100B2; CA2578296C

Abstract

A pump is formed by a housing (10) having an inlet (11) for connection to a source of fluid and an outlet (12) for pumped fluid. A rotor (15) is rotatable within the housing and the inlet (11) and the outlet (12) are spaced apart around the path of the rotor (15) in the housing. The rotor (15) has surfaces (16a, 16b, 16c, 16d) that form, with the housing (10), closed chambers (18a, 18b, 18c, 18d) which travel around the housing (10) to convey fluid from the inlet (11) to the outlet (12). The housing (10) carries a seal (14) that is located between the inlet (11) and the outlet (12) in the direction of travel of the rotor (15). The seal (14) co-operates with the rotor surfaces (16a, 16b, 16c, 16d) as the surfaces (16a, 16b, 16c, 16d) pass between the outlet (12) and the inlet (11) to prevent the formation of a chamber during said passage and so prevent fluid flow from the outlet (12) to the inlet (11). Such a pump is easily and cheaply produced and is particularly useful in medical applications.

Description

ROTARY PUMP WITH RESILIENTLY DEFORMED SEAL

The invention relates to pumps.

A known form of pump comprises a housing with an inlet for connection to a source

of fluid and an outlet for pumped fluid with the inlet and the outlet being spaced apart

around a path of a rotor within the housing. The rotor includes at least one surface

forming, with the housing, a closed chamber travelling around the housing to convey

fluid around the housing.

In such pumps, a problem is the prevention of direct communication between the

outlet and inlet. In JP-A-60240890, a flexible film is fixed to a partition wall between

the outlet and the inlet and engages partitioning pieces on the rotor. In GB-A-482750,

the rotor carries sections that seal against an arcuate surface of the housing. In US-A-

3282496 slidable elements are forced by pressure against the chamber-forming

surfaces of the rotor. In JP-A-60111078, the rotor carries movable seals formed by

various deformable bodies that seal against the housing between the outlet and the

inlet. In GB-A-1109374, the rotor carries seals that seal against the housing between

the inlet and the outlet

According to the invention, there is provided pump comprising a housing, a rotor path

defined within the housing, an inlet formed in the housing at a first position on said

rotor path, an outlet formed in the housing at a second position on said rotor path spaced from said first position, a rotor rotatable in said housing, at least two apices

formed on the rotor and sealing against said rotor path, at least one surface formed on

said rotor between said at least two apices, a chamber formed by said at least one rotor

surface between the at least two apices and the housing and travelling around said

rotor path on rotation of the rotor to convey fluid around the housing, a resilient seal

carried by the housing located on said rotor path and extending between the outlet and

the inlet in the direction of rotation of said rotor that each apex seals with, and

resiliency deforms, the seal, as each apex passes between the outlet and the inlet to

prevent fluid flow from said outlet to said inlet past the seal.

The following is a more detailed description of some embodiments of the invention,

by way of example, reference being made to the accompanying drawings in which:-

Figure 1 is a schematic cross-section through a pump including a housing provided

with an inlet and outlet and a rotor rotatable within the housing and sealing against a

seal provided by the housing, the rotor being shown in a first angular position,

Figure 2 is a similar view to Figure 1 but showing the rotor rotated by about 30° from

the position shown in Figure 1,

Figure 3 is a similar view to Figure 1 but showing the rotor rotated by about 60° from

the position shown in Figure 1, Figure 4 is a schematic side elevation partly in section of a first form of pump

incorporating a housing and a rotor of the kind shown in Figures 1 to 3 with the rotor

in a first axial position,

Figure 5 is a partial view of the pump of Figure 4 showing the rotor in a second axial

position,

Figure 6 is a similar view to Figure 4 omitting parts of the rotor and housing and

showing the rotor of the pump of Figure 4 in a third axial position

Figure 7 is a similar view to Figure 6 but showing an alternative embodiment of the

housing and the rotor.

Figure 8 is a side elevation of a further embodiment of the rotor.

Figures 9 to 11 are similar views to Figures 1 to 3 but showing an alternative form of

the housing.

Figure 12 is a similar view to Figure 1 but showing a first modified form of the

housing in which the inlet and the outlet are parallel but offset and in which the seal is

formed by a resilient membrane. Figure 13 is a view of the pump of Figure 12 showing the membrane acted on by a

pressurised fluid or gel;

Figure 14 is a view of the pump of Figure 12 showing the membrane acted on by a

spring;

Figure 15 is a view of the pump of Figure 12 showing the membrane acted on by an

adjustable screw;

Figure 16 is a similar view to Figure 12 but showing a second modified form of the

housing in which two inlets and two outlets are provided, with each inlet offset from

the associated outlet, and with two resilient seals each formed by a respective resilient

membrane, and

Figure 17 is similar view to Figure 16 but showing a third modified form of the

housing in which four inlets and four outlets are provided, four seals are provided and

the rotor forms eight chambers.

Referring first to Figures 1 to 3, the pump is formed by a housing indicated generally

at 10 which may be formed by a plastics moulding of, for example, polyethylene or

polypropylene. The housing 10 is formed with an inlet 11 for connection to a source of fluid and an outlet 12 for pumped fluid. The interior of the housing 10 is

cylindrical. The portion of the interior of the housing 10 between the outlet 12 and the

inlet 11, again in clockwise direction as viewed in Figures 1 to 3, carries a seal 14 that

will be described in more detail below.

The housing 10 contains a rotor 15. The rotor 15 may be formed of stainless steel or as a precision injection moulded plasties part formed from a resin such as acetal. As seen in the Figures, the rotor 15 is generally of circular cross-section and includes four recessed surfaces 16a, 16b, 16c and 16d of equal length equiangularly spaced around the rotor and interconnected by apices 17a, 17b, 17c and 17d formed by unrelieved portions of the rotor 15. Accordingly, each apex is rounded with a curvature that matches the curvature of the cylindrical housing surface 13 so that the rotor 15 is an interference fit within the cylindrical housing surface 13. As a result, each recessed surface 16a, 16b, 16c and 16d forms a respective chamber 18a, 18b, 18c and 18d with the cylindrical housing surface 13 as each surface 16a, 16b, 16c, 16d travels around that housing surface 13. If the housing 10 is formed from a resilient plastics material that deforms under load, the rotor 15 may be arranged to distend slightly the housing 10, so ensuring a fluid-tight seal around each surface 16a, 16b. 16c. 16d.

The rotor 15 is rotated in a clockwise direction in Figures 1 to 3 by a drive (not shown in the Figures). The seal 14 is formed by a block of elastomeric material that is compliant, flexible and resilient such as that sold under the trade mark Hytrel. The seal 14 is connected to the housing 10 to prevent fluid passing between the seal 14 and the housing 10. This may be by use of an adhesive. Alternatively, the seal 14 could be moulded with the housing 10 in a 2-shot injection moulding process. In this latter case, the material of the seal 14 must be such that it welds to the housing to prevent leakage. The seal 14 has a first axial edge 19 adjacent the inlet 11 and a second axial edge 20 adjacent the outlet 12. The seal 14 has a rotor engaging surface 21 that has a length between the first and second edges 19, 20 that is generally equal to the length of each of the recessed surfaces 16a, 16b, 16c and 16d between the associated apices 17a, 17b, 17c, 17d and is shaped to match the shape of each recessed surface 16a, 16b, 16c, 16d. The axial extent of the seal 14 is that at least the same as the axial extent of the recessed surfaces 16a, 16b, 16c, 16d. The seal 14 projects into the space defined by an imaginary cylinder described by a continuation of the cylindrical surface 13 between the inlet 11 and the outlet 12. The seal 14 may be flexed between the first and second axial edges 19, 20 so that it bows outwardly relatively to the seal 14 towards the axis of the rotor 15 where the recessed surfaces 16a, 16b, 16c, 16d are concave.

The natural resilience of the material will tend to return the seal 14 to the undistorted disposition after distortion by the rotor 15 and this may be assisted by a spring (not shown) acting on the radially outer end of the seal 14. The operation of the pump described above with reference to Figures 1 to 3 will now

be described. The inlet 11 is connected to a source of fluid to be pumped and the

outlet 12 is connected to a destination for the pumped fluid. The rotor 15 is rotated in

a clockwise direction as viewed in Figures 1 to 3. In the position shown in Figure 1,

the rotor surface 16a engages resiliently the seal surface 21. In this way, the space

between the housing 10 and the rotor 15 is closed in this zone and the passage of fluid

from the outlet 12 to the inlet 11 is prevented. In this position, the apex 17a is aligned

with the inlet 11 while the rotor surfaces 16b, 16c, 16d form respective sealed

chambers 18b, 18c, 18d with the cylindrical housing surface 13. As a result of earlier

revolutions of the rotor 15, these chambers 18b, 18c and 18d are filled with fluid in a

manner to be described below.

Referring next to Figure 2, on rotation of the rotor 15 by about 30°, the chamber 18d

is now connected to the outlet 12. The associated apex 17d contacts the seal surface

21 and seals against that surface. Accordingly, the rotating rotor 15 forces fluid from

the chamber 18d out of the outlet 12. In addition, the apex 17a previously aligned

with the inlet 11, moves away from the inlet 11 and allows the rotor surface 16a to

separate from the sealed surface 21 to begin to form a chamber 18a (Figure 3) with the

cylindrical housing surface 13 and with the apex 17d against the seal surface 21.

Referring next to Figure 3, a further rotation of the rotor 15 by about 60° from the

position shown in Figure 1, results in the rotor surface 16d that previously formed the chamber 18d adjacent with outlet 12 begins to contact the seal surface 21 and sealing

against that surface 21. Thus, the chamber 18d reduces in volume until it no longer

exists and fluid from that chamber is forced through the outlet 12. At the same time,

the rotor surface 16a formerly in contact with the seal surface 21 is now clear of that

surface 21 and forms a chamber 18a with the cylindrical housing surface 13 and the

chamber 18a receives fluid from the inlet 11. The apex 17d between the surfaces 16a

and 16d moves out of engagement with the seal surface 21 and starts to align with the

inlet 11.

The rotor 15 then moves to a position equivalent to the position shown in Figure 1 and

pumping continues. In this way, fluid is pumped between the inlet 11 and the outlet

12.

It will be appreciated that the rate of flow of liquid is proportional to the rate of

rotation of the rotor 15 and the volumes of the chambers 18a, 18b, 18c and 18d.

Although the rotor 15 is shown as having four surfaces 16a, 16b, 16c, 16d, it could

have any number of surfaces such as one or two or three surfaces or more than four

surfaces. The surfaces 16a, 16b, 16c, 16d may be planar, or may be, for example,

convexly or concavely curved. Preferably they are shaped as indentations formed by

the intersection with the rotor 15 of an imaginary cylinder having its axis at 90° to the

axis of the rotor and offset to one side of the rotor axis. As described above, the rotor engaging surface 21 of the seal 14 may be shaped to compliment the shape of the

surfaces 16a, 16b, 16c, 16d.

At all times, the seal 14 acts to prevent the formation of a chamber between the outlet

12 and the inlet 11 in the direction of the rotor 15. The resilience of the seal 14 allows

it always to fill the space between the inlet 11 and the outlet 12 and the portion of the

rotor 15 in this region. As the pressure differential between the inlet 11 or the outlet

12 increases, there is an increased tendency for fluid to pass between the seal 14 and

the rotor 15. The use of a spring acting on the seal 14, as described above, will

decrease that tendency and so allow the pump to operate at higher pressures. Thus,

the force applied by the spring determines the maximum pump pressure. Pumps are

known in which the outlet and the inlet are separated by a thin vane extending from

the housing and contacting the rotor. In such pumps, there is a volume of fluid

between the outlet and the inlet and a large pressure gradient across the vane that will

increase as the speed of rotation of the rotor. As a result, there is an increased liability

to leakage across the vane. In the pump described above with reference to the

drawings, although there is a pressure differential between the inlet and the outlet,

there is a much more gradual gradient as the fluid is gradually squeezed out of the

chambers 18a, 18b, 18c and 18d into the outlet 12 and then, after further rotation of

the rotor 15, gradually introduced into a chamber 18a, 18b, 18c and 18d on the inlet

side. This reduces the possibility of leakage and allows the pump to provide an accurate metered flow. The seal 14 acts as a displacer displacing the fluid between the

inlet 11 and the outlet 12.

Referring next to Figure 4, this Figure shows a pump operating on the principles

described above with reference to Figures 1 to 3. Parts common to Figures 1 to 3 and

to Figure 4 are given the same reference numerals and will not be described in detail.

In this embodiment, the rotor 15 is formed in two parts; an outer cylindrical sleeve 25

and an inner rod 26. The rod 26 is provided with a radially extending pin 27 that

engages a helical slot 28 provided in the sleeve 25.

The sleeve 25 is provided with a first set of surfaces 16a, 16b, 16c, 16d as described

above with reference to Figures 1 to 3 co-operating with the housing 10 having an

inlet 11 and an outlet 12 as also described above with reference to Figures 1 to 4.

In addition, however, the sleeve 25 is also provided with a second set of recessed

surfaces 29, a 29b, 29c, 29d at a position on the sleeve 25 axially spaced relative to the

first mentioned surfaces 16a, 16b, 16c, 16d. These second surfaces 29a, 29b, 29c, 29d

have a smaller circumferential extent than the first-mentioned surfaces 16a, 16b, 16c,

16d. In addition, the sleeve 25 is also formed with a circumferential groove 30 spaced

axially from the first mentioned surfaces 16a, 16b, 16c, 16d and the other side of the

surfaces 16a, 16b, 16c, 16d from the second surfaces 29a, 29b, 29c, 29d. In use, rotation of the rotor 15 in a direction shown in Figure 4 causes the pump to

operate as described above with reference to Figures 1 to 3. However, if the rotor

drive is reversed, with the rod 26 held in a fixed axial position relative to the housing

10, the pin 27 will travel along the slot 28 and move the sleeve 25 axially relative to

the rod 26 to a position in which the second surfaces 29a, 29b, 29c, 29d are aligned

with the inlet 11 and the outlet 12. Reverse rotation of the rod 26 will then cause the

second surfaces 29a, 29b, 29c, 29d to pump fluid as described above with reference to

Figures 1 to 3. In this case, however, since the second surfaces 29a, 29b, 29c, 29d

have a smaller angular extent, the pump volume will be smaller so allowing lower

flow rates.

It will be appreciated that, since the pump is symmetrical about a plane including the

rotor axis and midway between the inlet 11 and the outlet 12, the pump would operate

on reverse rotation of the rotor 15 to draw fluid from the outlet 12 and deliver it to the

inlet 11. It will also be appreciated that the surfaces 16a, 16b, 16c and 16d will need

to have a curvature that is similar to a corresponding portion of the curvature on the

seal 14 however because the surfaces are smaller the seal with have a permanently

bowed disposition.

The end 32 of the sleeve 25 remote from the rotor drive projects from the housing 10.

It is possible manually to push this end 32 so moving the sleeve 25 into the housing 10 until a groove 30 is aligned with the inlet 11 and the outlet 12. When in this position,

as shown in Figure 6, direct communication is permitted between the inlet 11 and the

outlet 12.

An alternative proposal is shown in Figure 7 in which the housing 10 includes two

inlets 11a and l ib and two outlets 12a and 12b. The first mentioned rotor surfaces

16a, 16b, 16c, 16d are aligned with the first inlet 11a and the first outlet 12a and the

second rotor surfaces 29a, 29b, 29c, 29d are aligned with the second inlet l ib and the

second outlet 12b. In this way, as the rotor rotates, additional volume is pumped so

increasing the flow rate. As seen in Figure 7, in this case, the second surfaces 29a,

29b, 29c, 29d are sized similarly to the first surfaces 16a, 16b, 16c, 16d. Of course,

the second surfaces 29a, 29b, 29c, 29d need not be sized similarly to the first surfaces

16a, 16b, 16c, 16d; they could have any relative size. It will be appreciated that by

displacing the rotor 15 axially relative to the housing 10, the first-mentioned rotor

surfaces 16a, 16b, 16c and 16d could be aligned with the second inlet l ib and the

second outlet 12b with the second rotor surfaces 29a, 29b, 29c and 29d being

inoperative and covered by the housing 10 and the first inlet 11a and the first outlet

12a being closed. Alternatively, the rotor 15 could be displaced in the opposite

direction relative to the housing so that the second rotor surfaces 29a, 29b, 29c and

29d are aligned with the first inlet 1 Ia and the first outlet 12a with the first-mentioned

rotor surfaces 29a, 29b, 29c and 29d being inoperative and covered by the housing 10

and the second inlet 1 Ib and the second outlet 12b being closed. In the embodiments described above with reference to the drawings the rotor 15 is

shown as a solid cylinder with the recessed surfaces 16a, 16b, 16c and 16d formed in

that surface. This need not be so. As shown in Figure 8, the rotor 15 may be formed

with a central cylindrical land 30 in which the recessed surfaces 16a, 16b, 16c, 16d are

formed with two annular ribs 31 arranged on respective opposite sides of the land 30.

The land 30 and the ribs 31 seal against the housing 10 using the elasticity of the

housing 10 to ensure fluid- tight seals. The radially relived areas between the ribs 31

and the land 30 reduce the frictional forces.

In Figures 1 to 3, the inlet 1 1 and the outlet 12 are shown at opposite axial ends of the

seal 14. As an alternative, the inlet 11 or the outlet could be formed in the seal 14.

This is shown in Figures 9 to 11. The pump of Figures 9 to 11 has parts in common

with the pump of Figure 1 to 3. These common parts will not be described in detail

and will be given the same reference numerals in Figures 9 to 11 as in Figures 1 to 3.

Referring to Figures 9 to 11, in this embodiment, the inlet 11 and the outlet 12 are

formed in the seal 14. The angular spacing between the inlet 11 and the outlet 12

remains the same as in Figures 1 to 3, but the width of the seal 14 is increased. The

pump of Figures 9 to 11 operates as described above with reference to Figures 1 to 3.

However, the formation of the inlet 11 and the outlet 12 in the seal 14 has the

advantage that the apices of the rotor 15 can remain in contact with the seal 14 before the outlet 12 and provide more precise delivery of the volume of fluid in the

associated chamber 18a, 18b, 18c, 18d. Another advantage is the edge 20 of the outlet

12 is coincident with the end of the seal 14 which allows all the liquid to be expelled

(scavenging) as the rotor surfaces 16a, 16b, 16c, 16d assume face to face contact with

the seal 14.

The pumps described above with reference to the drawings can be used for pumping

any fluid preferably containing no particulates. Such pumps may, however, find

particular application in the pumping of medical fluids and may be used with

intravenous administration sets. Such pumps allow aseptic pumping and metering of

fluid to high volumetric accuracies. In this case, the inlet 11 and the outlet 12 may be

connected in line before the housing 10 and the rotor 15 assembly are connected to a

drive. The housing 10 and rotor assembly 15 may be supplied with the inlet 11 and

the outlet 12 aligned with the groove 30 so that a delivery tube of the set is in a free

flow condition and able to be primed as soon as the housing 10 and rotor 15 assembly

is connected in-line. When the rotor 15 is connected to the drive, the making of the

connection moves the rotor 15 to a position in which the rotor surfaces 16a, 16b, 16c,

16d are aligned with the inlet 11 and the outlet 12 so that the pump 10 is ready for

metered operation. It is thus mechanically impossible for the rotor 15 to be in the free

flow position when connected to the drive so that, should the drive fail, free flow is

not possible. Referring next to Figure 12, parts common to Figures 1 to 11 and to Figure 12 will not

be described in detail and will be given the same reference numerals. The housing 10

of Figure 12 has the inlet 11 formed by a tube 35 extending in a direction generally

tangential to the circular path described by the rotor 15. In addition, the outlet 12 is

formed by a tube 36 also extending in a direction generally tangential to the circular

path described by the rotor 15. The directions of the inlet tube 35 and the outlet tube

36 are thus parallel but, as seen in Figure 12, are also offset. The effect of this is that

the inlet 11 is spaced around the housing 10 from the outlet 12 by a distance such that

the chamber 18a is fully exhausted through outlet 12 before the inlet 11 is open (so

that the inlet 11 is closed by the apex 17a). This has the advantage of reducing the

possibility of leakage between the outlet 12 and the inlet 11 and ensuring the

chambers 18 are fully evacuated.

In the arrangement shown in Figure 12, the outlet 12 is shown closer to the mid-point

of the seal 13 that the inlet 11. This arrangement could be reversed with the inlet 11

being the nearer to the mid-way point of the seal 14.

In this embodiment, the seal 14 is formed by a membrane 37 that extends between the

first and second axial edges 19, 20 of the housing 10 and between the outlet 12 and the

inlet 11. The membrane 37 is supported by a member 38 that applies a resilient force

to the membrane 37. This member 38 can have a number of forms. Some examples

of this are shown in Figures 13, 14 and 15. Parts common to Figure 12 and to Figures 13, 14 and 15 are given the same reference numeral and will not be described in detail.

First, referring to Figure 13 the member 38 could be formed by a resilient container 40

of gel or other fluid or gas that is held under pressure either by overfilling the

container in manufacture. Secondly referring to Figure 14, a movable cap 41 may

bear against the membrane 27 under the action of a spring 42. Thirdly, referring to

Figure 15, the cap 41 may bear against the membrane 27 with a force determined by

the adjustment of a screw 43.

The membrane 37 has a low coefficient of friction with the rotor 15 but is sufficiently

stretched to prevent the formation of wrinkles when deformed outwardly by the apices

17. The membrane 37 seals closely against the rotor 15 to displace fluid in the

chambers 18 and prevent leakage between the outlet 12 and the inlet 11.

The problem of communication between an outlet and an adjacent inlet is not confined

to the case disclosed above where a single inlet and a single outlet are provided with

fluid being conveyed between the single inlet and the single outlet. It is possible to

have two or more inlets and two or more outlets spaced around the housing 10. In this

case, the problem will still exist of preventing fluid communication between an outlet

and a succeeding inlet, in the direction of rotation of the rotor, but the outlet and the

inlet will not be associated with the same flow paths. An example of this will now be

described with reference to Figure 16. Referring next to Figure 16, parts common to Figure 12 and to Figure 16 will not be

described in detail and will be given the same reference numerals. The housing 10 of

Figure 16 has, in comparison with the arrangement of Figure 12, a second inlet 11a

and a second outlet l ib. The second inlet 11a is formed by a second inlet tube 35a

and the second outlet is formed by a second outlet tube 36a. The second inlet 1 Ia is

located on the housing 10 diametrically opposite the first inlet 11 and the first-

mentioned and second inlet tubes 35, 35a are parallel. The second outlet 12a is

located on the housing 10 diametrically opposite the first outlet 12 and the first

mentioned and second outlet tubes 36, 36a are parallel. A second membrane 37a and

resilient container 38a are provided, in any of the forms described above with

reference to Figure 12. The second membrane 37a is diametrically opposite the first-

mentioned membrane 37.

In use, as the rotor 15 rotates, starting from the rotor position shown in Figure 16, the

apices 17a, 17b, 17c and 17d can cover the associated inlets and outlets 11, 12a, 11a

and 12. Fluid in the chamber 18d passes to the second outlet 12a and fluid in the

chamber 18b passes to the first outlet 12. The fourth apex 17d seals against the first

membrane 37 and the second apex 17b seals against the second membrane 37a. The

first chamber 18a then connects to the first inlet 11 while the third chamber 18b

connects to the second inlet 11a. When the rotor 15 has rotated through 90° the

configuration of the pump is again as shown in Figure 16 and the above steps are repeated as rotation continues to pump fluid between the first inlet 11 and the first

outlet 12 and between the second inlet 1 Ia and the second outlet 12a.

It will be appreciated that, in this configuration, the seals formed by the membranes

37, 37a act to prevent fluid flow not between the inlet 11 and the associated outlet 12

and between the second inlet 11a and the associated second outlet 12a, but between

the first outlet 12 and the second inlet 1 Ia and between the second outlet 12a and the

first inlet 11. The problem overcome is, however, the same as described above with

reference to Figures 1 to 11 namely the prevention of fluid communication between an

outlet and the seal succeeding inlet in the direction of rotation of the rotor.

It will be appreciated that the pump described above with reference to Figure 16 could

be used to pump two different fluids so that the two fluids will be accurately pumped

at the same rate. Alternatively, the pump could be used to pump a single fluid at

double the rate of the pump described above with reference to Figure 12.

It will be appreciated that any of the pumps described above with reference to the

drawings may have more or less than four chambers 18a, 18b, 18c, 18d. A single

chamber is possible but will only give an output once per rotation of the rotor 15. A

number of smaller chambers having a total volume of one large chamber may provide

a smoother (less pulsed) output flow per revolution. In relation to the embodiment of

Figure 16, there may be more than two inlets and outlets where one or are a plurality of chambers is provided. The radial position and number of the inlets and outlets and

seals can be chosen to be non-synchronous with the number of the chambers on the

rotor (for example if there are 3 equi-spaced chambers on the rotor and 2 diametrically

opposing inlets, outlets and seals) to provide a smoother flow. An example of such a

pump is shown in Figure 17 where parts common to Figure 16 and to Figure 17 are

given the same reference numerals and are not described in detail. In the embodiment

of Figure 17, the rotor 15 forms eight chambers with the housing 10. Four pairs of

inlets and outlets, 11, 11a, l ib, l ie and 12, 12a, 12b, 12c are provided. Foul seals are

provided each formed with a respective membrane 37, 37a, 37b, 37c supported by a

respective member 38, 38a, 38b, 38c. The members 38, 38a, 38b, 38c can have any of

the forms described above with reference to Figures 13 to 15. As in Figure 16, each

membrane 37, 37a, 37b, 37c is located between an outlet 12c, 12, 12a, 12b of one pair

and the inlet 11, 11a, l ib, 1 Ic of the next succeeding pair of inlets and outlets. The

pump of Figure 17 operates as described above with reference to Figure 16 but with

the addition of two further pairs of inlets and outlets.

It will be appreciated, that the pumps described above with reference to the drawings

are formed from few parts - effectively, the housing 10, a rotor 15 and a seal 14. It is

possible to form the housing 10 and seal 14 in a two-shot injection moulding process.

Alternatively all three elements can be produced in a single assembly injection

moulding process in which the rotor 15 is moulded first with the housing 10 then

being moulded around the rotor 15 and finally the seal 14 moulded into the housing. The use of such a moulding process allows a pump to be manufactured cheaply and

simply to an extent that may allow the pump to be used as a disposable pump.

Claims

1. A pump comprising a housing (10) a rotor path defined within the housing,

an inlet (11) formed in the housing (10) at a first position on said rotor path, an outlet

(12) formed in the housing (10) at a second position on said rotor path spaced from

said first position, a rotor (15) rotatable in said housing (10), at least two apices (17a,

17b, 17c, 17d) formed on the rotor (15) and sealing against said rotor path, at least one

surface formed on said rotor between said at least two apices (17a, 17b, 17c, 17d), a

chamber (18a, 18b, 18c, 18d) formed by said at least one rotor surface between the at

least two apices (17a, 17b, 17c, 17d) and the housing (10) and travelling around said

rotor path on rotation of the rotor to convey fluid around the housing (10), a resilient

seal (14) carried by the housing (10) located on said rotor path and so extending

between the outlet (12) and the inlet (11) in the direction of rotation of said rotor (15)

that each apex (17a, 17b, 17c, 17d) seals with, and resiliently deforms, the seal (14),

as each apex (17a, 17b, 17c, 17d) passes between the outlet (12) and the inlet (11) to

prevent fluid flow from said outlet (12) to said inlet (11) past the seal (14).

2. A pump according to claim 1 wherein the seal (14) has a rotor-engaging

surface (21) having an axial and angular extent generally the same as the axial and

angular extent of the each chamber-defining surface (16a, 16b, 16c, 16d) of the rotor

(15).

3. A pump according to claim 1 or claim 2 wherein the or each chamber-defining

surface is concave in planes including the rotor axis.

4. A pump according to any one of claims 1 to 3 wherein the housing (10)

includes a generally cylindrical interior surface (13) co-operating with the rotor (15) to

form said chamber.

5. A pump according to claim 4 wherein the seal (14) interrupts said cylindrical

interior surface (13), extending axially and circumferentially relative to said surface

(13).

6. A pump according to claim 5 wherein the seal (14) projects radially inwardly

of the cylinder defined by said cylindrical surface (13).

7. A pump according to any one of claims 1 to 6 wherein the seal (14) has

angularly spaced first and second ends (20, 19) around the path of the rotor (15), the

outlet (12) being formed adjacent said first end (20).

8. A pump according to any one of claims 1 to 7 wherein the seal has angularly

spaced first and second ends (20, 19) around the path of the rotor (15), the inlet (11)

being formed adjacent said second end (19).

9. A pump according to claim 7 or claim 8 wherein the housing (10) includes a

generally cylindrical interior surface (13) forming said rotor path and co-operating

with the rotor (15) to form said chamber, the inlet (11) and the outlet (12) being

formed in said cylindrical interior surface (13) of the housing (15).

10. A pump according to claim 7 or claim 8 wherein the inlet (11) and the outlet

(12) are formed in said seal (14).

11. A pump according to any one of claims 1 to 10 wherein the seal (14) is formed

by a block of resilient material.

12. A pump according to any one of claims 1 to 10 wherein the seal is formed by a

membrane (37) and a member (40) resiliently supporting the membrane (37), the

membrane (37) sealing against the rotor (15).

13. A pump according to claim 12 wherein the resilient member is formed by a

container (40) of fluid or gas under pressure.

14. A pump according to claim 12 wherein the resilient member is formed by a

spring (41).

15. A pump according to any one of claims 1 to 14 wherein two or more chamber-

forming surfaces (16a, 16b, 16c, 16d) are provided on said rotor (15) at axially aligned

angularly spaced positions around the rotor (15), each chamber-forming surface (16a,

16b, 16c, 16d) co-operating with said seal (14) as the surface passes from said outlet

(12) to said inlet (11) in the direction of travel of the rotor (15).

16. A pump according to any one of claims 1 to 15 in which the rotor (15) is

movable axially relative to the housing (10) between a first axial position and a second

axial position, the rotor (15) including at least one additional chamber- forming surface

(29a, 29b, 29c, 29d) spaced axially from said first mentioned at least one chamber-

forming surface (16a, 16b, 16c, 16d), the first mentioned at least one chamber- forming

surface (16a, 16b, 16c, 16d) forming a chamber with the housing (10) in said first

axial position of the rotor (15) and the at least one additional chamber-forming surface

(29a, 29b, 29c, 29d) forming a chamber with the housing (10) in said second axial

position of the rotor (15).

17. A pump according to claim 16 wherein the volume of the chamber formed by

the first-mentioned at least one chamber- forming surface (16a, 16b, 16c, 16d) is

different from the volume of the chamber formed by the second at least one chamber-

forming surface (29a, 29b, 29c, 29d).

18. A pump according to claim 17 wherein the volume of the chamber formed by

the first-mentioned at least one chamber-forming surface (16a, 16b, 16c, 16d) is

greater than the volume of the chamber formed by the second at least one chamber-

forming surface (29a, 29b, 29c, 29d).

19. A pump according to any one of claims 1 to 15 in which the rotor (15) is

movable axially relative to the housing (10) between a first axial position at which the

at least one chamber- forming surface (16a, 16b, 16c, 16d) forms a chamber with the

housing (10) and a further axial position in which the rotor (15) cooperates with the

housing to provide direct communication (30) between the inlet (11) and the outlet

(12).

20. A pump according to any one of claims 16 to 19 wherein a mechanism (26, 27,

28) is provided for moving said rotor (15) axially between said first and second axial

positions.

21. A pump according to claim 20 and in which the mechanism (26, 27, 28) is such

that rotation of said rotor (15) in one sense acts to convey fluid from the inlet to the

outlet, rotation of said rotor (15) in an opposite sense moving said rotor (15) axially

between said first and second axial positions, reversal of rotation to rotation in said

one sense conveying fluid from said inlet to said outlet by said at least one additional

chamber-forming surface (29a, 29b, 29c, 29d) or allowing said direct communication.

22. A pump according to claim 21 wherein said mechanism (26, 27, 28) acts

between the housing and the rotor for moving the rotor axially relative to the housing

on rotation of said rotor in said opposite sense.

23. A pump according to any one of claims 20 to 22 wherein said mechanism

comprises a pin member (27) and a helical slot member (28), one member (27, 28)

being on the rotor (15) and the other member (27, 28) being on the housing (10),

rotation of the rotor (15) in said opposite sense moving the pin (27) in a helical path

along said slot (28) to move the rotor axially.

24. A pump according to any one of claims 1 to 23 wherein the housing includes a

second inlet (1 Ib) and a second outlet (12b) spaced axially along the rotor (15) from

first-mentioned inlet (11) and outlet (12), the rotor (15) including at least one further

surface (29a, 29b, 29c, 29d) forming, with the housing (10), a closed chamber

travelling around the housing (10), between the second inlet (l ib) and the second

outlet (12b) to convey fluid from said second inlet (l ib) to said second outlet (12b),

the housing (10) between the second outlet (l ib) and the second inlet (l ib) in the

direction of travel of the rotor (15), including a second seal for co-operating with said

further surface (29a, 29b, 29c, 29d), as the further surface (29a, 29b, 29c, 29d) passes

between the second inlet (1 Ib) and the second outlet (12b) to prevent the formation of

a chamber during said passage and so prevent fluid flow from said second outlet (12b)

to said second inlet (1 Ib).

25. A pump according to claim 24 wherein the rotor (15) is movable axially in one

sense to align the first-mentioned at least one chamber-forming surface (16a, 16b, 16c,

16d) and the second inlet (l ib) and outlet (12b) while closing the first inlet (11) and

the first outlet (12) and is moveable axially in an opposite sense to align said further at

least one chamber-forming surface (29a, 29b, 29c, 29d) with the first inlet (11) and the

first outlet (12) while closing the second inlet (1 Ib) and the second outlet (12b).

26. A pump according to any one of claims 1 to 25 wherein the housing (10) is

formed of a resilient material, the rotor (15) engaging and resiliently distending the

housing (10) to provide a fluid-tight seal between the housing and the housing-

contacting portions of the rotor (15).

27. A pump according to any one of claims 1 to 25 and in which the housing (10)

has a generally cylindrical interior surface (13), the rotor (15) having a co-operating

generally cylindrical exterior surface sealing against said interior surface, said at least

one chamber- forming surface (16a, 16b, 16c, 16d) being formed in said exterior

surface.

28. A pump according to claim 27 wherein said exterior rotor surface is formed by

a land (30) on the rotor (15), the land (30) having axially spaced ends and the rotor

being provided with radially relieved portions at said ends.

29. A pump according to claim 27 wherein a circumferential rib (31) is formed on

each relieved portion, each rib (31) sealing resiliently against said housing surface.

30. A pump according to any one of claims 1 to 29 wherein a single inlet (11) and

a single outlet are provided, the rotor conveying fluid from said inlet to said outlet.

31. A pump according to any one of claims 1 to 30 and including a second inlet

(1 Ib) and a second outlet (12b) spaced circumferentially around the housing (10) from

the first mentioned inlet (11) and outlet (12), the rotor (15) forming a plurality of

chambers (18a, 18b, 18c, 18d) conveying fluid from the first mentioned inlet (11) to

the first mentioned outlet (12) and from the second inlet (l ib) to the second outlet

(12b), the first mentioned seal (38) being located between the second inlet (l ib) and

the first mentioned outlet (12) and a second seal (38b) being provided between the

first mentioned outlet (12) and the second inlet (1 Ib).

32. A pump according to claim 31 wherein the rotor (15) forms at least four

chambers (18a, 18b, 18c, 18d).

33. A pump according to any one of claims 1 to 32 wherein the rotation of the rotor

(15) is reversible to pump fluid from the outlet (12) to the inlet (11).

34. A pump according to any one of claims 1 to 33 including a drive for rotating

the rotor.

35. A pump according any one of claims 1 to 34 where the housing (10) and seal

(14) is an insert moulding, over-moulding or dual shot moulding.

36. A pump according to any one of claims 1 to 35 where the housing (10), seal

(14) and rotor (15) are a single assembly injection moulding.

37. An intravenous administration set including a pump according to any one of

claims 1 to 36.