GB2320296A - A drive device and a vacuum cleaner incorporating such a device - Google Patents

Abstract

A fluid-pressure-operated reciprocating motor comprises a housing 11 defining a chamber separated into two parts 20a,20b by a movable partition, such as a diaphragm 21 or a piston, which carries a valve 32 resiliently biased to a closure position. The diaphragm 21 is movable by a partial vacuum in chamber 20b against a return spring 40 until it is at, or in the vicinity of, an end position of its stroke when a metal disc on the valve 32 is attracted by a magnet 44 on the housing 11, closing the vacuum inlet port 18 and venting chamber 20b through the valve 32. The valve 32 remains in this position during the return stroke of the diaphragm 21, until the magnetic attraction is overcome by the force of the spring 40. The vacuum-operated motor may be used to drive a pump piston 27 for delivering wash fluid in a vacuum cleaner.

Description

A DRIVE DEVICE AND A VACUUM CLEANER INCORPORATING SUCH DEVICE The present invention relates generally to a drive device, and particularly to a drive device operating on fluid pressure. As used in this specification the term "fluid pressure" will be understood to refer not only to a fluid pressure above atmospheric pressure, but also to a fluid pressure below atmospheric, that is a so-called depression or partial vacuum.

In a number of applications it would be of value to have available a drive device acting on fluid pressure without requiring other energy sources such as electricity or a combustible fuel. Drive devices acting solely on a fluid pressure are, of course, known, particularly so-called air motors. These largely operate from a large positive pressure, however, such as a source of compressed air, and require turbines to produce a high speed of rotation.

Not all applications are suitable for such drive devices, especially those which inherently require reciprocating motion. The present invention seeks, therefore, to provide a reciprocating motion drive device which can be used for driving any one of a range of mechanisms.

One application for which a reciprocating drive device would be particularly suitable is to drive a fluid pump.

Although rotary fluid pumps are known, reciprocating pumps, especially of the positive-displacement type, have advantages in many applications, especially where it is required to deliver a liquid at a determined pressure.

Drive devices for this purpose must be self-starting in the sense that, upon cessation of motion, they must adopt a position in which, immediately upon application of the fluid pressure, they will commence to reciprocate without requiring a "priming" or initiating trigger motion.

It is also a requirement of such drive devices that they be reliable, economic to produce and robust, and they must have the ability to function over a relatively wide variation in drive pressure and load conditions without stalling. This is especially true of the exemplary application to a vacuum cleaner where the drive device may be formed as a pump to deliver a wash liquid to the surface being cleaned, via an outlet on or in the vicinity of the vacuum cleaner suction inlet. This may be a hose nozzle in the so-called cylinder type of vacuum cleaner or an opening in the body of a so-called "upright" type of vacuum cleaner.

The present invention seeks to provide a fluid pressure drive device in which the above-listed requirements are met.

According to one aspect of the present invention a fluid pressure-operated reciprocating drive device comprises a housing defining a chamber separated into two parts by a movable partition member carrying a valve resiliently biased to a closure position in which the two parts of the chamber are isolated from one another by the partition member, the partition member being movable between two end positions and there being means for opening the valve when the partition member is at or in the vicinity of one of the two end positions whereby to open communication between the two parts of the chamber.

In another aspect the present invention provides a pressure-operated reciprocating drive device having a movable partition member displaceable between opposite end positions, which member separates a chamber into first and second parts sealed from one another, and a valve movable between open and closed positions in the first of which it opens communication between one of the first and second parts of the chamber and a fluid pressure source, and in the second of which it closes such communication, the commutation of the valve between the said open and closed positions being at least initiated by the movement of the movable partition member between the said two end positions.

In a preferred embodiment of the invention the valve is carried on the partition member itself.

Likewise, it is preferred that the valve-opening movement is encouraged by a magnetic attraction between a part of or a member carried by the valve and a part of or a member carried by the chamber within which the partition member is housed.

The present invention also comprehends, in another aspect, a pressure-operated reciprocating drive device in which the application of fluid pressure to drive the reciprocating motion is controlled by opening and closing a valve, in which valve commutation at least in one sense is caused by magnetic attraction of elements brought into proximity with one another by the reciprocating motion itself.

The valve commutation in a sense opposite the said one sense is preferably caused by resilient biasing means.

Such resilient biasing means may comprise first and second springs the combined force of which is sufficient to overcome the force of the magnetic attraction closing the valve but the individual force of at least one of which is not sufficient to overcome the force of the said magnetic attraction.

Preferably the partition member is a diaphragm sealed across the chamber and separating it into the said two parts. The valve may be carried on the movable diaphragm and, when in the position closing communication with the fluid pressure source, it preferably acts to open communication across the movable diaphragm between the two parts of the chamber separated thereby.

In an alternative embodiment, acting in substantially the same way, the partition member may be a piston slidable sealingly within a chamber and sealingly separating it into two parts.

The said means for opening the valve may comprise a magnet located in one of the two parts of the chamber at or adjacent the said one of the two end positions of the partition member. Alternatively of course, the magnet may be located on the valve, the chamber being provided with a suitable ferromagnetic member to complete the magnetic circuit.

The valve is preferably formed so that it remains held open by the valve-opening means as the partition member returns towards its other end position.

Preferably the valve is closed, against the action of the valve-opening means, when the partition member reaches or as it approaches the said other end position. Valve closure may be effected by, for example, resilient biasing means and the action of the valve-opening means may be overcome by contact between the partition member or a member carried thereby and a part of the valve or a member connected thereto.

Likewise, the partition member may be resiliently biased towards the said other end position and urged towards the said one position by a pressure differential applied between the two parts of the chamber.

The said pressure differential is preferably achieved by applying a depression to a first of the said two parts of the chamber, the second of the two parts of the chamber preferably being vented to atmosphere.

The movable partition member may be connected to a drive output of the device, and in particular this drive output may be connected to a pump whereby to effect pumping when the reciprocating motion takes place.

The drive device of the present invention is particularly suitable for use in a vacuum cleaner of the type having a subsidiary wash fluid delivery circuit. Such vacuum cleaners typically utilise a hydrocyclone to separate the liquid and gas components after they have been drawn in by suction. The present invention is to be seen as comprehending a vacuum cleaner of such type incorporating a drive device as defined herein as the pump for the fluid circuit.

Embodiments of the present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic axial section through a vacuum-operated drive device having an integral pump and formed as a first embodiment of the invention, shown in the rest condition; Figure 2 is a sectional view similar to Figure 1 showing the pump in a first operational position; Figure 3 is a similar axial view corresponding to those of Figures 1 and 2, showing the device in a second operational position; Figure 4 is an axial section through a second embodiment of the invention; Figure 5 is a section like Figure 4, showing the pump in a different configuration; Figure 6 is an exploded view of the pump of Figure 4; Figure 7 is a general perspective view of a vacuum cleaner formed as an embodiment of the present invention illustrating the location of the device; and Figure 8 is a partial sectional view taken on the line VIII-VIII of Figure 7.

Referring first to Figure 1, the drive device shown will be described in the orientation illustrated although it will be appreciated that it will operate equally well in any orientation. The device shown comprises a cylindrical body 11 having a radial wall 12 at one end thereof, terminating in an axial flange 13 which mates circumferentially with a similar annular flange 14 at the periphery of a radial wall 15 extending from a cylindrical body 16 of a housing cap. The housing cap body 16 has an axial projection 17 forming a spigot for connection to a vacuum source, defining a cylindrical passage 18 which is coaxial with the cylindrical bodies 11, 16. The cap 16 and the body 11 are held together by clamping means (not shown) acting around the peripheries of the radial walls 12, 15 at the region of the annular flanges 13, 14. Such clamping means may, for example, be integral parts of a plastic moulding ring or may comprise a ring of bolts threadedly engaged in one of the annular flanges 13, 14 or passing right through both and secured by nuts.

Within the body 11 is a chamber 20 separated into a first chamber part 20a and a second chamber part 20b by a diaphragm 21.

The diaphragm 21 has a central circular flat disc-like reinforced body part 22 reinforced by flat circular plate 23 of a valve body generally indicated 24 and which will be described in more detail below. Around the annular periphery of the circular flat disc-like part 22 of the diaphragm 21 is an annular curved roll-section 25 having a peripheral bead 26 captive in a housing (not referenced) in the internal face of the annular peripheral flange 14 of the housing cap 16. The peripheral bead 26 is sealed between the annular flange 14.

The flat circular support plate 23 is integrally formed at one end of a cylindrical valve body 27 having two axially extending slots 28, 29 in its side wall 30. This side wall 30 defines a cylindrical valve chamber 31 within which is located a valve shutter member 32 comprising a solid cylindrical body having a transverse pin 33 projecting laterally into each of the slots 28, 29 of the side wall 30 of the valve body 27.

The valve shutter 32 projects through an opening 33 in the end of the valve body 27 carrying the flat reinforcement plate 23, with an annular space 34 (which could alternatively be defined by grooves in either the valve shutter 32 or the cylindrical side wall 30) and has an enlarged head 35 which is greater in diameter than the opening 33. The valve shutter 32 is typically made from plastics material, as are all the components of the drive device unless specified herein, and secured to the head 35 is a ferromagnetic disc 36. The fixing is made by means (not shown) such as adhesive, fixing screws or the like. The valve shutter is free to move axially within the chamber 31 parallel to the cylindrical side wall 30 of the valve body 27, with its movement being limited by engagement of the transverse pin 33 with the ends of the two slots 28, 29. The projecting arms of the pin 33 are engaged by a biasing spring 38 which reacts against the upper face of the diaphragm 22.

Projecting from the lower face of the diaphragmreinforcing plate 23 and surrounding the opening 33 therein, is a small annular rib 39 which serves to locate one end of a coil spring 40, and fulfils a secondary function as will be described in more detail below. The other end of the spring 40 is housed in an annular recess 41 in the cap housing body 16.

The axial passage 18 through the spigot 17 and the cap housing body 16 terminates in an opening 42 into the second chamber part 20b and around the rim of this opening is a resilient annular seal 43.

Radially surrounding the seal 43, but radially inwards from the annular channel 41, is housed an annular magnet 44 the diameter of which is slightly less than the diameter of the ferromagnetic disc 36 carried at the end of the valve shutter 32.

The end of the cylindrical body 11 of the drive device is connected to a pump generally indicated 50, comprising a cylindrical pump body 51 defining a pump chamber 52 housing a piston defined by the end of the valve body 33 which is secured to a diaphragm 53 reinforced by a circular plate 54 and secured in position by a screw 55 passing through the plate 54 and the centre of the diaphragm 53, and being screwed into the end of the valve body 33.

The periphery of the diaphragm 53 is trapped between the end of the cylindrical drive device body 11 and the mating end of the pump body 51.

The pump body 51 has a transverse end wall 56 through which pass two openings 57, 58. Across the end of the transverse wall 56 is a resilient diaphragm 59 secured in place by a pump end cap 60 having inlet and outlet connector spigots 61, 62. The opening 58 has a counterboned enlargement 63 and the diaphragm 59 has a suitably shaped incision (not shown) defining a flap 64 which acts as an inlet flap valve as will be described below. Correspondingly the hollow passage 65 in the spigot 62 has a counterboned enlargement 66 and the diaphragm 59 has a shaped incision defining a flap 67 in register with the counterboned enlargement 66 enabling the flap 67 to act as an output flap valve as will be described below.

The operation of the drive device and pump is as follows: in its rest condition, as shown in Figure 1, the diaphragm 22 is pressed against the end of the cylindrical body 11 by the biasing spring 40. Likewise the biasing spring 38 urges the valve shutter 32 upwards (as seen in the drawings) so that the enlarged head of the valve shutter 32 is pressed against the under face of the diaphragm-reinforcing plate 23 of the valve body 27.

The two chambers 20a and 20b are therefore entirely isolated from one another. If, now, a partial vacuum or depression is applied to the passage 18 (for example by opening of a valve in a line connected to the spigot 17) the pressure in the chamber 20b is caused to fall. The pressure in the chamber 20a remains at atmospheric pressure, this chamber communicating with the outside through a vent valve 49, and correspondingly the diaphragm 21 is urged downwards towards the position shown in Figure 2.

As the diaphragm 21 moves downwards it carries with it the valve body 27. At this stage the spring 38 maintains the valve shutter 32 in its raised position with the pin 33 close to the upper ends of the slots 28, 29 so that no communication between the chambers 20a and 20b can take place. As the diaphragm 21 reaches the lowermost end of its stroke, however, the metal disc 36 is brought into the vicinity of the magnet 44 until the magnetic attraction between the two overcomes the force of the spring 38 and draws the valve shutter 32 downwardly with respect to the valve body 27 and the diaphragm 21. The annular ridge 39 insures that the diaphragm 21 comes to rest, with the ridge 39 engaging the inner face of the diaphragm cap 16, with a small space between the disc 36 and the magnet 44 to ensure that, even at its lowermost position, the diaphragm 21 does not prevent relative motion between the valve shutter 32 and the valve body 27 from taking place. The drive device is now in the position illustrated in Figure 2.

In this position, as will be seen, the valve shutter 32 is displaced slightly from its uppermost position, which can be seen by comparing the position of the pin 33 and the head 35 of the shutter in comparison with their positions in Figure 1. As will be seen the pin 27 has moved slightly along the slots 28, 29 and the head 35 of the valve shutter 32 has become displaced from the lower face of the diaphragm-reinforcing plate 23. This movement of the valve shutter 32 is sufficient to open communication, through the passage 34, between the chambers 20a and 20b. At the same time the metal disc 3 is pressed firmly against the O-ring seal 43 not only by the magnetic attraction exerted by the magnet 44, but also by the vacuum in the passage 18. The combined forces actions on the plate 36 ensure that this closes off communication between the chamber 20b and the vacuum source connected to the passage 18. The pressure across the diaphragm 21 can, therefore, quickly equalise, with air being drawn into the chamber 20b from the chamber 20a, and air being drawn into the chamber 20a through the passage 49 from the atmosphere.

The pressure differential previously holding the diaphragm 21 in the lower position is thus quickly nullified and the spring 40 therefore starts to urge the diaphragm-reinforcing plate 23, and therefore the diaphragm and the valve assembly carried thereon, upwardly. However, the magnetic attraction between the metal disc 36 and the magnetic 44 holds the valve shutter 32 closed so that the drive device reaches the position shown in Figure 3.

As will be appreciated the spring 40 is substantially stronger than the spring 38 so that it can overcome the force of the spring 38 in driving the diaphragm 21 upwardly notwithstanding the fact that the valve shutter 32 is held in its lowermost position by combined forces of the magnet 44 and the vacuum in the passage 18 (strictly speaking the pressure difference across the disc 36). The valve body 27 is thus urged back towards the position it occupied in Figure 1. Just before the valve body 27 reaches this position, however, the spring 38 becomes entirely compressed and transmits the full force of the spring 40 to the transverse pin 33 thus lifting the valve shutter 32 away from the seal 43 and carrying the metal disc 36 sufficiently far from the magnet 44 for the magnetic attraction decaying in accordance with the inverse square law, to fall to such a value that the force exerted by the spring 38 is now greater than the magnetic attraction between the disc 36 and magnet 44 so that the shutter is rapidly urged upwardly from the position shown in Figure 3 towards the position shown in Figure 1.

The communication between the chamber 20b and the vacuum source is now reinstated and the cycle of operations can repeat. Reciprocation of the valve body 27, which acts as the piston in the pump chamber 5, causes the inlet valve 64 to open as it moves downwards from the position shown in Figure 1 to the position shown in Figure 2, drawing liquid in through the spigot 61, and correspondingly, during its rising motion from the position shown in Figure 2 to the position shown in Figure 3 it acts to drive liquid out through the delivery valve 67, closing the inlet valve 64. The pump delivery is thus made with a force determined by the force of the spring 40 which is charged by the energy extracted from the vacuum in the displacement of the diaphragm 21 from its upper to its lower position.

The drive device and pump illustrated in Figures 1 to 3 can therefore be totally immersed within a liquid source (providing a suitable breather connection is made, for example by a breather line (not shown) to the passage 49.

This, of course, could be dispensed with providing the energy required to expand and compress the air sealed in the chamber 20a could be provided by the vacuum and the spring 40, that is if there is sufficient energy to perform the extra work.

Figures 4 to 6 illustrate a second embodiment of the invention which has been developed to be incorporated into a vacuum cleaner machine and to operate from the vacuum pressure within the machine. The pump delivers cleaning solution to the cleaning head for the specific cleaning purpose.

This pump overcomes the need to incorporate an additional electric motor to drive a pump. Electric motors have been found to be unreliable in operation and require high levels of safety and protection from the working conditions present within such machines.

The pump can also operate in other applications where an existing energy source is available to activate the pump.

The present invention does not, of course, have to be configured as a pump. It may be formed just as a drive device or motor, the reciprocating action being used to drive other utilisers than a pump.

According to another aspect of the present invention, therefore, there is provided a motor comprising a number of chambers which are operated from a fluid source which has a dynamic pressure, which may be either positive or negative. A mechanism which causes the force to be transferred rapidly to each chamber in turn by means of a valve or valves controlled by magnets provides the movement to operate a diaphragm pump. The diaphragm operates as a conventional pump to transfer a fluid to the desired point.

The motor assembly uses magnetic retained valve closure to induce a magnified pressure differential acting upon the diaphragm component of the motor assembly. In other words a motor pump assembly uses different diaphragm surface areas to amplify or reduce the pressure as claimed in Claim 3 to a smaller or larger diaphragm located in the pump assembly to increase or decrease the volume of fluid displaced to give a desired volume delivery.

The proposed motor pump is housed in a spherical shaped casing that could be submerged in the cleaning solution.

Referring now to Figure 4, there are six ports: Ports 1 and 2: Air at suction pressure provided by the vacuum source.

Port 3: Fluid input Port 4: Fluid output Ports 5 and 6: Pressure relief ports.

Operation of ports 1 and 2 motor section of assembly.

1. The vacuum is applied to both ports, port 1 open, port 2 closed. The inlet to port I is sealed by a magnetic valve.

2. Air is therefore drawn from chamber b) thus applying force to a larger diameter diaphragm. The diaphragm commences movement, but is retained by the magnet.

3. Air vents into the headspace behind the diaphragm through port 5.

4. At a point where the suction overcomes the magnetic retention the diaphragm snaps across and is retained on the suction side magnet.

5. The mechanical operation is now reversed to a position shown in Figure 2.

Referring to Figure 4, operation of ports 3 and 4 pump section of assembly: fluid is drawn in through port 3 through a one way valve and out through port 4 through a one way valve.

Referring to Figure 6, the component parts consist of the motor chamber port 1, a plastic coated steel insert 2, which is secured into the chamber port 1. A magnet 3 is fixed to an assembly coupling 4 which passes through the motor diaphragm 5. Component 6 is a seal which locates onto the diaphragm locating shaft 9. The pump diaphragm 8 locates onto the diaphragm pump body 7. The diaphragm pump cover 10 locates over the pump diaphragm 8.

The assembly is completed by components 1-6 which provides the second motor assembly.

Referring now to Figure 7, there is shown a vacuum cleaner, generally indicated 70, of a known configuration comprising a lower vessel 71 mounted on wheels 72 and carrying, supported around its rim, a suspended baffle 73 separating the vessel 71 into upper and lower chambers. An electrical motor unit is housed in a cover 74 which clips onto the rim. A vacuum hose 75 connects to the vessel 71 and leads to a vacuum head 76. Such a structure is well known.

Within the vessel 71 is an inner wall 77 of impermeable material forming, as can be seen in Figure 8, a reservoir 78 for a liquid to be dispersed. A pump, having a construction such as that described in Figures 1 to 3 is mounted on one wall of the reservoir 78, which is spaced from the Outer wall of the vessel 71. The vessel 78 is sealed around its upper perimeter by the motor housing 74 when this is fitted to the vessel 71 so that the interior of the reservoir 78 remains at or near ambient pressure whilst outside the vessel 78 the pressure falls to the level of the vacuum in the lower part of the vacuum cleaner.

In Figure 8 the pump, indicated 80, is shown in an inverted position with respect to the orientation shown in Figures 1 to 3. The passage 18 of Figure 1 communicates with a suction tube 81 which extends from the pump 80 through the wall 77 of the reservoir 78 to communicate with the interior of the vessel 71. The pump inlet port 61 communicates with the interior of the reservoir 78 and the pump delivery port 65 communicates with a tube 83 leading to a coupling carried in the wall of the vessel 71. As can be seen in Figure 7 the coupling 84 can be connected to a connector 85 which is carried at the end of a liquid delivery tube 86 associated with the vacuum hose 75 and supported thereby, and terminating at or close to the vacuum head 76. A tube 90 leads from the vent port 49 of the chamber 20a to the outside. In operation, therefore, when there is sufficient liquid in the reservoir 78 to cover the inlet port 61, energisation of the vacuum cleaner motor to cause a vacuum in the lower part of the vessel 71 will start to drive the vacuum pump 80 via the port 81 and vents to deliver liquid from the reservoir 78 through the tube 83, the coupling 84, the connector 85 and the tube 86 to the vacuum head 76 where it first engages the carpet or other surface being cleaned, to dissolve stains or dirt thereon, and is then drawn by the vacuum at the head 76 through the vacuum hose 75 into the interior of the vessel 71, separating from the gas by a hydrocylone or like effect such that liquid is not drawn back into the motor housed in the casing cover 74.

Claims (20)

1. A fluid-pressure-operated reciprocating drive device comprising a housing defining a chamber separated into two parts by a movable partition member carrying a valve resiliently biased to a closure position in which the two parts of the chamber are isolated from one another by the partition member, the partition member being movable between two end positions and there being means for opening the valve when the partition member is at or in the vicinity of one of the two end positions whereby to open communication between the two parts of the chamber.

2. A drive device as claimed in Claim 1, in which the partition member is a diaphragm sealed across the chamber and separating it into two parts.

3. A drive device s claimed in Claim 1, in which the partition member is a piston slidable sealingly within a chamber and sealingly separating it into two parts.

4. A drive device as claimed in any of Claims 1 to 3, in which the said means for opening the valve comprises a magnet located in one of the two parts of the chamber at or adjacent the said one of the two end positions of the partition chamber.

5. A drive device as claimed in any preceding claim, in which the valve is so formed that it remains held open by the valve-opening means as the partition member returns towards its other end position.

6. A drive device as claimed in any preceding claim, in which the valve is closed, against the action of the valve-opening means when the partition member reaches, or as it approaches, the said other end position.

7. A drive device as claimed in Claim 6, in which the valve closure is effected by resilient biasing means and in which the action of the valve-opening means is overcome by contact between the partition member, or a member carried thereby, and a part of the valve or a member connected thereto.

8. A drive device as claimed in any preceding claim, in which the partition member is resiliently biased towards the said other end position and urged towards the said one position by a pressure differential applied between two parts of the chamber.

9. A drive device as claimed in Claim 8, in which the said pressure differential is achieved by applying a depression to a first of the said two parts of the chamber.

10. A drive device as claimed in any preceding claim, in which the second of the two parts of the chamber is vented to atmosphere.

11. A pressure-operated reciprocating drive device having a movable partition member displaceable between opposite end positions, which member separates a chamber into first and second parts sealed from one another, and a valve movable between open and closed positions in the first of which it opens commutation between one of the first and second parts of the chamber and a fluid pressure source and in the second of which positions it closes such communication, the communication of the valve between the said open and closed positions being at least initiated by the movement of the movable partition member between the said two end positions.

12. A drive device as claimed in claim 11, in which the valve is carried on the partition member itself.

13. A drive device as claimed in Claim 11 or Claim 12, in which the valve-opening movement is encouraged by magnetic attraction between a part of, or a member carried by, the valve and a part of, or member carried by, the chamber within which the partition member is housed.

14. A pressure-operated reciprocating drive device in which the application of fluid pressure to drive the reciprocating motion is controlled by opening and closing a valve, in which valve commutation at least in one sense is caused by magnetic attraction of elements brought into proximity with one another by the reciprocating motion itself.

15. A drive device as claimed in Claim 14, in which the valve commutation in the sense opposite the said one sense is caused by resilient biasing means.

16. A drive device as claimed in Claim 14 and Claim 15, in which the said resilient biasing means comprise first and second springs the combined force of which is sufficient to overcome the force of the magnetic attraction closing the valve but the individual force of at least one of which is not sufficient to overcome the force of the said magnetic attraction.

17. A drive device as claimed in any of Claims 14 to 16, in which the valve is carried on a movable diaphragm and, when in the position closing communication with the fluid pressure source it acts to open communication across the movable diaphragm between the two parts of the chamber separated thereby.

18. A drive device substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

19. A vacuum cleaner having supplementary means for delivering a washing fluid to a cleaning head delivery port, in which a fluid circuit therefor includes a drive device as claimed in any preceding claim.

20. A vacuum cleaner with a fluid delivery circuit including a drive device substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.