Pump assembly with a rotational to reciprocal action transmission and a diaphragm pump

Abstract

A pump assembly has a motor, a gearbox, a rotational to reciprocal action transmission and a diaphragm pump, in which a shaft of the motor, an output shaft of the gearbox, a reciprocal movement axis of the transmission, and a pump shaft of the diaphragm pump are all aligned on a main axis.

Claims

1. A pump assembly comprising: a motor, a gearbox, a rotational to reciprocal action transmission, and a diaphragm pump, in which a shaft of said motor, an output shaft of said gearbox, a reciprocal movement axis of said transmission, and a pump shaft of said diaphragm pump are all aligned on a main axis, in which said output shaft of said gearbox comprises a rotor, in which said transmission comprises a sleeve rotationally connected to said rotor and freely axially moveable relative thereto, and an annular track arranged around said sleeve, in which said sleeve comprises a plurality of radially extending arms, in which said track comprises an annular path with axially extending formations, in which outer ends of said arms are disposed on said track, and in which said sleeve is axially statically connected to said pump shaft.

2. The pump assembly as claimed in claim 1 in which said gearbox comprises a planetary gearbox.

3. The pump assembly as claimed in claim 1 in which said pump assembly comprises an outer casing comprising a first part and a second part, in which said first part comprises a first part of a screw thread connection on an outer surface thereof, and in which said second part comprises a second part of said screw thread connection on an inner surface thereof.

4. The pump assembly as claimed in claim 3 in which said second part defines a chamber of said diaphragm pump, in which said second part comprises a fluid inlet aperture, in which a first fluid line connector is mounted to said fluid inlet aperture, in which an inlet valve is provided in said fluid inlet aperture, in which said inlet valve comprises a first umbrella valve comprising a first support frame with a plurality of first apertures and a first resilient umbrella valve member for closing said first apertures under positive pressure from said diaphragm pump and opening said first apertures under negative pressure from said diaphragm pump, and in which said first support frame is disposed between a first end of said first fluid line connector and a shelf provided in said inlet aperture.

5. The pump assembly as claimed in claim 4 in which said second part comprises a fluid outlet aperture, in which a second fluid line connector is mounted to said fluid outlet aperture, in which an outlet valve is provided in said fluid outlet aperture, in which said outlet valve comprises a second umbrella valve comprising a second support frame with a plurality of second apertures and a second resilient umbrella valve member for closing said second apertures under negative pressure from said diaphragm pump and opening said second apertures under positive pressure from said diaphragm pump, and in which said second support frame is disposed between a first end of said second fluid line connector and a shelf provided in said outlet aperture.

6. The pump assembly as claimed in claim 1 in which a rotational bearing is provided between said sleeve and said pump shaft.

7. The pump assembly as claimed in claim 6 in which said track comprises an upper surface and a lower surface comprising corresponding axially extending formations such that a path is defined for said outer ends to travel along.

8. The pump assembly as claimed in claim 7 in which said sleeve comprises four radially extending arms, in which said lower surface and said upper surface each comprise an annular sequence of four troughs, each one extending through 90 degrees of said path, and in which said upper surface is axially offset from said lower surface by 45 degrees.

9. The pump assembly as claimed in claim 8 in which said four radially extending arms comprise a first pair of 180 degree opposed arms at a first axial level relative to said sleeve, and a second pair of 180 degree opposed arms at a second axial level relative to said sleeve, in which the second axial level is axially spaced from said first axial level by a clearance distance, in which said path between said upper surface and said lower surface has a height which is equal to a combination of a height of said outer ends and said clearance distance, in which said first pair of arms is in contact with said upper surface and said second pair of arms is in contact with said lower surface.

10. The pump assembly as claimed in claim 8 in which said motor is configured to run at 3,000 rpm, in which said gearbox comprises a two-stage planetary gearbox with a combined gear ratio of 30-1, such that said output shaft rotates at 100 rpm, which is converted by said transmission into 400 reciprocal actions per minute of said diaphragm pump.

11. The pump assembly as claimed in claim 3 in which said second part comprises a first part of a bayonet fixing on an outer surface thereof.

12. The pump assembly as claimed in claim 3 in which said screw thread connection is axially coincident with at least a portion of said transmission on said main axis.

13. The pump assembly as claimed in claim 12 in which said first part comprises a chamber for housing said gearbox and a mounting for holding said motor, and in which said second part defines a chamber of said diaphragm pump.

14. The pump assembly as claimed in claim 13 in which said diaphragm pump comprises a diaphragm, and in which a peripheral portion of said diaphragm is sealingly secured between a first end of said first part and a shelf provided in said second part adjacent to said second part of said screw thread connection.

15. The pump assembly as claimed in claim 14 in which said chamber comprises a plurality of air vents.

16. The pump assembly as claimed in claim 15 in which said mounting comprises a platform provided at a second end of said first part for axially supporting said motor, and a lip portion for laterally supporting said motor.

17. The pump assembly as claimed in claim 16 in which said platform comprises an aperture through which said shaft passes, and in which an impeller is mounted to said shaft and is located in said aperture.

18. The pump assembly as claimed in claim 17 in which said gearbox comprises a plurality of latches which are a snap-fit inside said chamber of the first part.

Description

(1) The invention can be performed in various ways, but one embodiment will now be described by way of example and with reference to the accompanying drawings, in which:

(2) FIG. 1 is a perspective view of a pump assembly according to the present invention;

(3) FIG. 2 is a side view of the pump assembly shown in FIG. 1;

(4) FIG. 3 is a side view of the pump assembly shown in FIG. 1, with an outer casing thereof removed:

(5) FIG. 4 is an exploded view of the pump assembly shown in FIG. 1;

(6) FIG. 5 is a cross-sectional perspective view of the pump assembly shown in FIG. 1;

(7) FIG. 6 is a perspective view of the pump assembly shown in FIG. 1 with a motor thereof removed;

(8) FIG. 7 is a perspective view of the pump assembly as shown in FIG. 6 with a first part of an outer casing thereof also removed;

(9) FIG. 8 is a perspective view of the pump assembly as shown in FIG. 7 with a first stage and Saturn gear of a planetary gearbox thereof also removed;

(10) FIG. 9 is a perspective view of the pump assembly as shown in FIG. 8 with a planetary gearbox thereof also removed;

(11) FIG. 10 is a perspective view of the pump assembly as shown in FIG. 9 with all parts of a transmission thereof, save for a lower housing, also removed;

(12) FIG. 11 is a perspective view of the pump assembly as shown in FIG. 10 with a lower housing thereof also removed;

(13) FIG. 12 is a perspective view of the pump assembly as shown in FIG. 11 with a diaphragm of a diaphragm pump thereof also removed; and,

(14) FIG. 13 is a perspective exploded view of second fluid line connector and fluid outlet valve components of the pump assembly as shown in FIG. 1.

(15) As shown in the Figures a pump assembly 1 comprises a motor 2, a gearbox 3, a rotational to reciprocal action transmission 4 and a diaphragm pump 5, in which a shaft 6 of the motor 2, an output shaft, in the form of rotor 7, of the gearbox 3, a reciprocal movement axis of the transmission 4 and a pump shaft 8 of the diaphragm pump 5 are all aligned on a main axis A-A.

(16) Starting from the top of the stack of drive components 2-5, the motor 2 is a known standard electrical motor, which spins at 3,000 rpm. As is clear in the Figures the motor 2 is annular and axially compact. The gearbox 3 is a planetary gearbox, and the shaft 6 of the motor 2 extends down into it, with the sun gear 9 of the first stage 10 thereof at its end. As such, the shaft 6 of the motor 2 drives the sun gear 9 directly.

(17) Referring to FIG. 4, the planetary gearbox 3 comprises the first stage 10 and a second stage 11 below it. Referring to FIGS. 4 and 7, the first stage 10 comprises the sun gear 9 at its centre, with three planetary gears 12 mounted around it, which are supported by Saturn gear 13. The Saturn gear 13 is provided on an inner surface 3a of outer casing 3b of the planetary gearbox 3 (visible in FIG. 7). The planetary gears 12 are mounted on spindles 14 which are statically connected to carrier 15. The sun gear 9 comprises nine teeth, each planetary gear 12 comprises eighteen teeth, and the Saturn gear comprises forty five teeth. As the sun gear 9 rotates under drive from the motor 2, it turns the planetary gears 12, which then travel around the sun gear 9 in an orbital path due to their connection with the static Saturn 13 gear outside them. In other words, the sun gear 9 drives the planetary gears 12 along the annular Saturn gear 13. The orbital rotation of the planetary gears 12 rotates the carrier 15. The carrier's rpm is a proportion of the rpm of the sun gear 9, and is determined by the orbital rotational speed of the planetary gears 12, which is a factor of both the diameters and the numbers of teeth of the sun gear 9 and the planetary gears 12.

(18) Referring to FIG. 4, the carrier 15 has second sun gear 16 on an underside 17 thereof, which forms a part of the second stage 11. Therefore, the sun gear 16 of the second stage 11 is driven directly by the carrier 15. Three second planetary gears 18 are mounted around the second sun gear 16, and are supported by the Saturn gear 13, which is the same along the axial length of the planetary gearbox 3. The second planetary gears 18 are mounted on second spindles 19 which are statically connected to second carrier 20. The second stage 11 is the same as the first stage 10 in that the second sun gear 16 comprises nine teeth and the second planetary gears 18 comprise eighteen teeth. Again, as the second sun gear 16 rotates under drive from the carrier 15, it turns the second planetary gears 18, which then travel around the second sun gear 9 in an orbital path due to their connection with the static Saturn 13 gear outside them. The orbital rotation of the second planetary gears 18 rotates the second carrier 20. The second carrier's rpm is a proportion of the rpm of the second sun gear 16, and is determined by the orbital rotational speed of the second planetary gears 18, which is a factor of both the diameters and the numbers of teeth of the second sun gear 16 and the second planetary gears 18.

(19) The second carrier 20 has rotor 7 mounted on an underside 21 thereof, such that the rotor 7 is the output shaft of the planetary gearbox 3. The first stage 10 and second stage 11 of the planetary gearbox 3 have a combined gear ratio of 30-1, such that the rotor 7 rotates at 100 rpm under drive from the motor 2.

(20) The rotor 7 is hexagonal in cross-section, and comprises ribs 22 at each outer corner. Referring to FIGS. 4 and 9, the transmission 4 comprises sleeve 23, an inner surface 24 of which has a hexagonal shape corresponding to that of the rotor 7, and has slots 25 at inner corners thereof to receive the ribs 22. This complex shape ensures that the sleeve 23 is securely rotationally static in relation to the rotor 7, and that the rotational loading applied to the sleeve 23 by the rotor 7 is spread equally around the connection between the two. However, the sleeve 23 is freely axially moveable relative to the rotor 7, such that it can move reciprocally on the main axis A-A while still being rotated by the rotation of the rotor 7.

(21) The sleeve 23 comprises four radially extending arms 26, which are circumferentially spaced at 90 degree intervals. The arms 26 each have an annular slider 27 at an outer end 28 thereof, and as shown in FIG. 4 they also each have a lower bracing section 29 to provide axial support. Furthermore, the sleeve 23 comprises an annular skirt 30 which extends between the arms 26 to provide further support and load bearing potential.

(22) Referring to FIGS. 8 to 10, the sliders 27 are disposed in an annular track 31 arranged around the sleeve 23. The annular track 31 is defined by an upper housing 32 and a lower housing 33 which are held together inside the pump assembly 1, as described further below. The upper housing 32 comprises an upper surface 34, and the lower housing comprises a lower surface 35, each of which comprises an annular sequence of four troughs 36, each one extending through 90 degrees, such that four peaks 37 are also formed. The upper surface 34 has the same shape but is axially offset from the lower surface 35 by 45 degrees, such that an annular path 38 is defined between the two of them which has a consistent axial depth. In other words, where the lower surface 35 is formed as a peak 37 the upper surface 34 is formed as a corresponding trough 36. Therefore, as described further below, for each 360 degree rotation of the rotor 7, the sleeve 23 performs four reciprocal actions as the sliders 27 travel on the annular track 31 along the axially undulating path 38. As such, the 100 rpm of the rotor 7 is converted by the transmission 4 into 400 reciprocal actions.

(23) Referring to FIG. 9, the four arms 26 comprise a first pair of 180 degree opposed arms 26a at a first axial level relative to the sleeve 23, and a second pair of 180 degree opposed arms 26b at a second axial level relative to the sleeve 23, which second axial level is axially below the first axial level by a small clearance distance. It is effectively the sliders 27 of the first pair of arms 26a and the second pair of arms 26b which are axially offset from one another in this way. The path 38 has an axial depth which is equal to a combination of a height of the sliders 27 and the small clearance distance, such that sliders 27 of the first pair of arms 26b ride on the upper surface 34 in use and the sliders 27 of the second pair of arms 26b ride on the lower surface 35 in use. This construction ensures that there is sufficient clearance at the peaks 37 and troughs 36 of the upper surface 34 and lower surface 35 to allow the sliders 27 to pass without jamming. As the upper surface 34 is axially offset from the lower surface 35 by 45 degrees, the sliders 27 of the first pair of arms 26a reach a peak 37 on the upper surface 35 when the sliders 27 of the second pair of arms 26b reach the bottom of a trough 36 on the lower surface 34. Without any axial clearance gap there would be a danger of the sleeve 23 jamming in the track 31 at this point. This construction also means that the loading carried by the transmission 4 in use is divided between the first pair of arms 26a and the upper surface 34 on the one hand, and the second pair of arms and the lower surface 35 on the other.

(24) Referring to FIG. 5, the sleeve 23 comprises an internal socket 23a in which is located a rotational roller bearing 23b. The sleeve 23 also comprises an aperture 23c on an underside 23d thereof. Located in the aperture 23c is an annular socket 41a provided at a centre of the diaphragm 41.

(25) The roll of the pump shaft 8 is performed by a pin-like structure comprising a head section 8a and a tail section 8b. The pump shaft 8 is mounted to the inside of the sleeve 23 with the tail section 8b passing through the bearing 23b and the aperture 23c, such that the tail section 8b extends into the socket 41a. The tail section 8b is secured in the socket 41a by a screw thread. This axially secures the sleeve 23 to the diaphragm 41, by clamping the head section 8a to the bearing 23b, and consequently the bearing 23b to the socket 41a. However, due to the bearing 23b the sleeve 23 can rotate freely around the pump shaft 8 and the socket 41a, such that its rotational movement is not transmitted thereto. Instead, that rotational movement is carried by the bearing 23b.

(26) Referring to FIGS. 5, 11 and 12, the diaphragm pump 5 comprises pump chamber 40, inside which is securely located the resilient diaphragm 41, as explained further below. The pump chamber 40 comprises a fluid inlet aperture 42 and a fluid outlet aperture 43. (In the Figures the fluid inlet aperture 42 is on the right and the fluid outlet aperture 43 is on the left, save for in FIG. 5, which depicts the pump assembly 1 from the opposite side.)

(27) Therefore, each time the sleeve 23 travels upwardly on the main axis A-A the pump shaft 8 lifts the diaphragm 41 such that it performs a priming stroke, and fluid can be drawn into the pump chamber 40 through the fluid inlet aperture 42. Likewise, each time the sleeve 23 travels downwardly the pump shaft 8 depresses the diaphragm 41 such that it performs a dispensing stroke, and fluid can be pumped from the pump chamber 40 through the fluid outlet aperture 43.

(28) As is clear from FIG. 3, the stack of drive components 2-5 is axially very compact. This is mainly due to the short axial length of the planetary gearbox 3, but also due to the fact that the track 31 which converts the rotational movement into a reciprocal action is radially arranged around the rotor 7 rather than being below it. Therefore the input rotation and the output reciprocation of the transmission 4 are co-axial on the main axis A-A.

(29) The pump assembly 1 comprises an outer casing 44 comprising a first part 45 and a second part 46. The first part 45 comprises a first part of a screw thread connection 47 on an outer surface 48 thereof, and as shown in FIG. 11 the second part 46 comprises a second part of the screw thread connection 49 on an inner surface 50 thereof. With this arrangement the first part 45 and the second part 46 overlap with one another where they connect together. The area of axial overlap is illustrated at 51 in FIG. 2 and FIG. 5. FIGS. 2 and 3 are to scale with one another, with the components shown at the same level. As such, it can be seen that this area of overlap 51 extends internally from the diaphragm 41 to the region of the track 31.

(30) What this overlap does is it eliminates any axial length being taking up by the connection between the first part 45 and the second part 46. The connection is radially outside the stack of drive components 2-5, and can therefore be co-axial with it. This construction of first part 45 and second part 46 is also advantageous because it allows for the pump assembly 1 to be easily constructed and dismantled, and it provides ready access to the stack of drive components 2-5. In particular, removing the first part 45 from the second part exposes the transmission 4 and the underside of the planetary gearbox 3.

(31) The first part 45 of the outer casing 44 comprises an internal chamber 45a, which is visible in FIG. 5, principally for housing the planetary gearbox 3. It also has a mounting 52 for holding the motor 2. The planetary gearbox 3 comprises a plurality of latches 53 which are a snap-fit with formations 43b inside the internal chamber 45a. This ensures that the planetary gearbox 3 is held securely in place relative to the motor 2 above it, and also relative to the transmission 4 beneath it.

(32) Referring to FIG. 6, the mounting 52 for holding the motor 2 comprises a platform 54 provided at a second end 55 of the first part 45 for axially supporting the motor 2, and a lip portion 56 for laterally supporting the motor 2. The first part 45 comprises three radially extending buttress formations 57, each of which comprises a platform portion 58 and a lip portion 59 at upper ends 60 thereof. The three platform portions 58 define the platform 54, and the three part-circumferentially extending lip portions 59 defined the lip portion 56. Each platform portion 58 comprises an aperture 61 for receiving a screw to secure the motor 2 thereto. With this construction the motor 2 is held in place at the second end 55 of the first part 45 rather than being inside it. Also, the minimal physical connection between the motor 2 and the first part 45 minimises the build-up of heat in use as the motor 2 operates.

(33) The platform 54 comprises an aperture 62 through which the shaft 6 passes in order to reach the planetary gearbox 3 inside the first part 45. As shown in FIG. 6 an impeller 63 is mounted to the shaft 6 and is located in the aperture 62. The impeller 63 creates air flow around the motor 2 and inside the internal chamber 43a, to help cool the components in use. Further, the first part 45 comprises a plurality of air vents 64, which facilitate such cooling air flow.

(34) Referring to FIGS. 11 and 12, the second part 46 of the outer casing 44 defines the pump chamber 40, which is located below the second part of the screw thread connection 49. A shelf 65 is provided in the second part 46, on which a peripheral portion 66 of the diaphragm 41 is disposed. A mounting plate 67 (shown in FIG. 4) is disposed on the peripheral portion 66, which mounting plate 67 comprises a central portion 68 for supporting the lower housing 33 of the transmission 4, and a flange portion 69 for overlying the peripheral portion 66. When the first part 45 and the second part 46 of the outer casing 44 are fully screw threaded together, a first end 70 of the first part 45 is applied to the flange portion 69, thereby to sealingly secure the diaphragm 41 between the shelf 65 and the first end 70. (This arrangement of components is also clear from FIG. 5.) Therefore, the diaphragm 41 is actually held in place between the first part 45 and the second part 46, meaning that the screw thread connection between these parts of the outer casing 44 is also the means by which the diaphragm 41 is retained for reciprocal motion. As such, the screw thread connection serves two purposes, and eliminates the need for further axial length to be taken up by separate features.

(35) In addition, the upper housing 32 and the lower housing 33 of the transmission 4 are also held together between the first part 45 and the second part 46. In particular, these parts of the transmission 4 are held between the central portion 68 of the mounting plate 67 and the outer casing 3b of the planetary gearbox 3. (This arrangement of components is also clear from FIG. 5.) Therefore, the screw thread connection between the first part 45 and the second part 46 also serves to affix the two opposing parts of the transmission 4 together, and therefore also takes some of the loading applied to the track 31 by the sleeve 23 in use.

(36) The second part 46 comprises the first part of a bayonet fixing 71 on an outer surface 72 thereof. This is for fixing to a co-operating mount (not shown) designed to support a plurality of pump assemblies like pump assembly 1.

(37) A first fluid line connector 73 is mounted to the fluid inlet aperture 42 and a second fluid line connector 74 is mounted to the fluid outlet aperture 43. The first fluid line connector 73 and the second fluid line connector 74 are identical, and each comprises a tail section 75 to which a resilient fluid hose (not shown) can be connected in order to plumb the pump assembly 1 into a chemical dispensing system. Namely, a fluid supply hose (not shown) can be connected to the first fluid line connector 73, in order to supply chemical to be pumped by the pump assembly 1, and a fluid delivery hose (not shown) can be connected to the second fluid line connector 74, in order to facilitate the delivery of chemical from the pump assembly 1. The tail sections 75 comprise three ribs 76 over which these hoses can ride when they are connected thereto, and which service to retain the hoses in place thereon.

(38) Referring to FIG. 13, which shows the second fluid line connector 74, it can be seen that it comprises a fluid pathway 77, which extends therethrough from a first end 78 thereof to a second end 79 thereof, and the first part of a screw thread connection 80. As can be seen from FIG. 12, the first inlet aperture 42 and the second inlet aperture 43 both comprises the second part of the screw thread connection 81, such that the first fluid line connector 73 and the second fluid line connector 74 can be secured in place therein respectively. The fluid line connectors 73 and 74 each comprises a nut formation 82 below the first part of the screw thread connection 80, which allows for the them to be fixed securely in the fluid inlet aperture 42 and fluid outlet aperture 43 respectively by means of a suitable tool.

(39) A one-way inlet valve 83 is provided in the fluid inlet aperture 42, which allows fluid to enter the diaphragm pump 5 during a priming stroke thereof, and which prevents fluid exiting the fluid inlet aperture 42 during a dispensing stroke thereof. A one-way outlet valve 84 is provided in the fluid outlet aperture 43 which is identical to inlet valve 83, except it is arranged the opposite way around, such that it prevents fluid entering the diaphragm pump 5 during the priming stroke thereof, and allows fluid to exit the fluid outlet aperture 43 during the dispensing stroke thereof.

(40) In particular, the inlet valve 83 and the outlet valve 84 are umbrella valves of the same construction. Part of the outlet valve 84 is show in an exploded view in FIG. 13, and both the inlet valve 83 and the outlet valve 84 are shown in cross-section in FIG. 5 (FIG. 5 being an opposite view to the rest of the Figures, with in the inlet valve 83 on the left.) In both cases they comprise a first support frame 85 with a plurality of apertures 86 and a first resilient umbrella valve member 87 (only shown in FIG. 5) for opening and closing the apertures 86. Referring to FIG. 5, the umbrella valve member 87 comprises a stem 88 which is mounted in central aperture 89, and an annular flange section 90 which sits in seat area 91.

(41) In terms of inlet valve 83, the annular flange section 90 is for closing the first apertures 86 thereof under positive pressure from the diaphragm pump 5, and opening the first apertures 86 thereof under negative pressure from the diaphragm pump 5. The umbrella valve member 87 of the inlet valve 83 is resiliently biased to close the first apertures 86 thereof, but only with a force which is readily overcome by the negative pressure generated by the lifting of the diaphragm 41. In terms of outlet valve 84, the opposite is true. Namely, the annular flange section 90 is for closing the first apertures 86 thereof under negative pressure from the diaphragm pump 5, and opening the first apertures 86 thereof under negative pressure from the diaphragm pump 5. The umbrella valve member 87 of the outlet valve 84 is resiliently biased to close the first apertures 86 thereof, but only with a force which is readily overcome by the positive pressure generated by the depression of the diaphragm 41

(42) In each case, the support frame 85 is disposed between the first end 78 of the fluid line connector 73, 74 in question and a shelf 92 provided in the fluid inlet aperture 42 and fluid outlet aperture 43 respectively. This arrangement is beneficial because there is no need for a separate O-ring seal between the fluid line connectors 73, 74 and the fluid inlet aperture 42 and fluid outlet aperture 43 respectively, as in known devices. Instead, the fluid seal is provided by the support frame 85 itself.

(43) In use the pump assembly 1 operates as follows. The pump assembly 1 is meant to form a part of a chemical dispensing system for providing chemical washing fluids to industrial laundry or washing facilities. As part of such an installation, a mount is provided for supporting a plurality of pump assemblies like pump assembly 1. The first part of a bayonet fixing 71 is used to secure the pump assembly 1 in such a mount, with the motor 2 uppermost. A fluid supply hose (not shown) is then connected to the tail section 75 of the first fluid line connector 73, in order to supply chemical washing fluids to the pump assembly 1 from a drum, and a fluid delivery hose (not shown) is connected to the tail section 75 of the second fluid line connector 74, in order to facilitate the delivery of chemical washing fluids from the pump assembly 1 to associated laundry or washing machines. The motor 2 is then connected in the known way to a simplex I/O electronic interface (not shown) which is for receiving operational signals from a main dosing unit (not shown). The motor 2 is also connected to a power supply in the known way.

(44) Each of the laundry or washing machines at the installation sends periodic requests for washing chemicals to the main dosing unit according to their programmed wash cycles. The main dosing unit then sends operation signals to the pump assemblies forming a part of the system, as appropriate. If the main dosing unit determines that pump assembly 1 is to operate to dispense a particular quantity of chemical washing fluid from the drum to which it is connected to one of the machines, it sends an appropriate run time instruction to the I/O interface, which then runs the motor 2 accordingly. This kind of operational communication between components of a chemical dispensing system is well known, and will not be further described here.

(45) When the motor 2 is run it rotates the shaft at 3,000 rpm, which rotates the sun gear 9 of the first stage of the planetary gearbox 3 at the same rpm. The rotation of the sun gear 9 drives the planetary gears 12 along the Saturn gear 13, which rotates the carrier 15. As explained above the rpm of the carrier 15 is a proportion of the rpm of the sun gear 9, and is determined by the orbital rotational speed of the planetary gears 12, which is a factor of both the diameters and the numbers of teeth of the sun gear 9 and the planetary gears 12. The rotation of the carrier 15 rotates the second sun gear 16, which drives the second planetary gears 18 along the Saturn gear 13, which rotates the second carrier 20. Once again, the rpm of the second carrier is a proportion of the rpm of the second sun gear 16, and is determined by the orbital rotational speed of the second planetary gears 18, which is a factor of both the diameters and the numbers of teeth of the second sun gear 16 and the second planetary gears 18. The first stage 10 and second stage 11 of the planetary gearbox 3 have a combined gear ratio of 30-1, such that the rotor 7 mounted to the second carrier 20 rotates at 100 rpm.

(46) The rotation of the rotor 7 rotates the sleeve 23 at the same rpm. As such the sliders 27 travel around the track 31 at 100 rpm, the sliders 27 of the first pair of arms 26a riding on the upper surface 34 and the sliders 27 of the second pair of arms 26b riding on the lower surface 35. Due to the axially undulating nature of the upper surface 34 and the lower surface 35 the sliders 27 each perform four reciprocal actions for each revolution. As such, the 100 rpm of the rotor 7 is converted by the transmission 4 into 400 reciprocal actions per minute of the sleeve 23 on the rotor 7. The sleeve 23 rotates on the bearing 23b and does not transmit its rotational movement to the pump shaft 8.

(47) The axial reciprocal actions of the sleeve 23 drive the pump shaft 8 at the same rate of axial reciprocal actions. As such, the diaphragm pump 5 is driven at a speed of 400 pumping actions per minute. Each time the sleeve 23 travels upwardly on the rotor 7 the pump shaft 8 lifts the diaphragm 41 such that it flexes and performs a priming stroke. The negative pressure inside the pump chamber 40 causes the inlet valve 83 in the fluid inlet aperture 42 to open, and a volume of chemical washing fluid to be drawn into the pump chamber 40 through the fluid pathway 77 of the first fluid line connector 73, from the fluid supply hose (not shown) fitted to the tail section 75 of the first fluid line connector 73. At the same time the negative pressure causes the outlet valve 84 in the fluid outlet aperture 43 to close. At the top of the priming stroke, when the sliders 27 of the second pair of arms 26b are each located at a peak 37 on the lower surface 35 of the track 31, the diaphragm pump 5 is flooded with chemical washing fluid to be pumped.

(48) As soon as the sleeve 23 rotates further and the sliders 27 all begin to fall into the next trough 36 on the lower surface 35 of the track 31, the pump shaft 8 depresses the diaphragm 41 such that it flexes and performs its dispensing stroke. The positive pressure generated in the pump chamber 40 causes the inlet vale 83 to close, and the outlet valve 84 to open, and as such the chemical washing fluid inside the pump chamber 40 is pumped out of the outlet aperture 43, via the fluid pathway 77 of the second fluid line connector 74, into the fluid delivery hose (not shown) fitted to the tail section 75 of the second fluid line connector 74. At the bottom of the dispensing stroke, when the sliders 27 of the first pair of arms 26a are each located at a peak 37 on the upper surface 34 of the track 31, the diaphragm pump 5 is empty. As soon as the sleeve 23 rotates further and the sliders 27 all begin to rise again, the diaphragm 41 begins its next dispensing stroke, in a repeat of the above described action.

(49) The continued reciprocal action of the diaphragm pump 5 drives the chemical washing fluid from the drum to the laundry or washing machine which requested it, via one or more valves, manifolds or dilution points, depending on the nature of the installation. The operation signal from the main dosing unit comprises a motor run time instruction which equates to a desired volume of chemical washing fluid. For example, the motor 2 may be run for 5 seconds. As such, one this period of time has elapsed the motor 2 stops and the pump assembly 1 falls still, until such time as it is instructed to run once again. There are various known ways to refine the exact run time requirements for pumps forming a part of chemical dispensing systems, such as using flow sensors either inside or downstream of pumps to measure the actual rather than designed pumping performance, and then using processors either in the main dosing unit or local to the pumps to increase or decrease the run times accordingly, in order to ensure that the correct quantity of washing fluid is delivered. Such control systems and mechanisms are already common in the field and will not be described herein in any further detail, save to point out that any of the known systems can be applied to the pump assembly 1. This would include the application of any known kind of flow sensors to the pump assembly 1, or at any point downstream thereof, which can communicate their findings to the main dosing unit via the I/O interface at the motor 2, using any known communication protocol.

(50) Whenever the motor 2 is run the impeller 63 is rotated, which generates air flow around the motor 2 and inside the internal chamber 43a, to help cool the components. Air travels through the air vents 64 to facilitate this.

(51) In the event that any of the components of the stack of drive components 2-5 requires inspection or replacement, the first part 45 of the outer casing 44 can be removed from the second part 46 by unscrewing the screw thread connection between these parts. Lifting the first part 45 away from the second part 46 removes the rotor 7 from the sleeve 43, leaving the lower half of the pump assembly 1 exposed. This allows inspection and repair of the transmission 4 and/or the diaphragm pump 5. The various parts of the transmission 4 and the diaphragm pump 5 can be removed, similar to as in the sequence illustrated in FIGS. 9 to 12.

(52) What this allows for is the adjustment of the performance characteristics of the transmission 4. In particular, the upper housing 32 and lower housing 33 can be switched out for an alternative pair (not shown), which can have an upper surface and lower surface respectively with or a greater or smaller number of troughs, for example just two rather than four, which would halve the frequency of the diaphragm pump 5 to 200 rpm. Alternatively, or in addition to this, the upper surface and lower surface can have a greater or lesser depth of troughs, which would increase or decrease the axial throw of the pump shaft 8, and therefore the pumping capacity of the diaphragm pump 5. It will be appreciated that making such adjustments would be a simple procedure as the upper housing 32 and the lower housing 33 are not fixed to each other, or to the second part 46. The upper housing 32 can simply be lifted free once the first part 45 is removed. The sleeve 23 is connected to the diaphragm 41 by the pump shaft 8, capturing the lower housing 33 and the mounting plate 67 therebetween, but the pump shaft 8 can be readily released from the diaphragm 41 by unscrewing the tail section 8b from the socket 41a, thereby freeing the sleeve 23, lower housing 33 and mounting plate 67.

(53) As the first part 45 is lifted free, it takes the motor 2 and the planetary gearbox 3 with it. The motor 2 can be removed from the platform 54 if required, and/or the planetary gearbox 3 can be removed from the internal chamber by releasing the snap-fit connection provided by the latches 53.

(54) The pump assembly 1 can be re-assembled in a reverse of the above described procedure.

(55) The pump assembly 1 can be altered without departing from the scope of claim 1. For example. in other alternative embodiments (not shown), the pumping performance is different due to the use of motors which run at different speeds and/or the use of planetary gearboxes with different gear ratios and/or the use of transmissions with different conversion rates and/or the use of pump chambers of different capacities. These variables are all a matter for the skilled person to determine, and are altered to suit the requirements of particular applications.

(56) In another alternative embodiment (not shown), the first part and the second part of the outer casing are connected together with resilient clamping arms. In another alternative embodiment (not shown) the motor and the planetary gearbox are both located in the internal chamber inside the first part of the outer casing. In another alternative embodiment (not shown), the inlet valve and the outlet valve are spring loaded ball valves.

(57) In other alternative embodiments (not shown), the gearboxes are of other constructions to planetary gearboxes, such as a regular constant mesh gearboxes or helical gearboxes and so on.

(58) Therefore, the present invention provides a pump assembly in which the motor 2, the gearbox 3, the transmission 4 and the diaphragm pump 5 are arranged in a convenient stack, with the shaft 6, the rotor 7, the sleeve 23 and the pump shaft 8 all aligned on the main axis A-A. Further, the pump assembly 1 is axially short and compact due to a number of other novel design features, including the arrangement of the track 31 around the sleeve 23, and the arrangement of the screw thread connection between the first part 45 and the second part 46 of the outer casing 44 around the transmission 4.