US20130302201A1 - Gear Pump - Google Patents

Abstract

A gear pump has a face plate2 cooperating with central plate24 defining a pump chamber21 holding gears16. The pump chamber21 is in fluid communication with drive chamber32 holding the rotor40 of an electric motor. An O-ring18 may be used to seal the face plate2. Other elements may be sealed using a permanent seal such as glue.

Description

FIELD OF INVENTION
• The invention relates to a gear pump.
BACKGROUND OF THE INVENTION
• A gear pump is a type of pump in which two intermeshed gears rotate within a chamber. The teeth of the gears entrain liquid between the gears and the inner surface of the chamber and as the gears rotate pump liquid in the chamber is pumped from an inlet to the chamber to an outlet to the chamber.
• Gear pumps can be used in many applications. Of particular interest are applications where long term reliability is required, for example where a pump is to be installed in a location where access is difficult, making service or replacement difficult, or in a consumer product where long term reliability avoids product failure and customer dissatisfaction.
• There is accordingly a need for gear pumps that are designed for long life.
SUMMARY OF INVENTION
• According to the invention there is provided a gear pump for pumping a pump fluid, comprising:
• a pump chamber having a first port and a second port, and a pair of gears mounted for rotation in the pump chamber for driving pump fluid from the inlet to the outlet;
• a motor comprising a rotor and a drive shaft connected to the rotor to drive the pair of gears, the drive shaft and rotor being arranged in a drive chamber, the motor further comprising a stator arranged around the drive chamber;
• wherein the pump chamber and the drive chamber are in fluid communication to allow pump fluid to pass between them.
• In this way, the pump fluid can provide lubrication for the rotor in the drive chamber.
• The inventors have realised that it is not necessary to completely seal the chamber of a gear pump from a motor, and that by not doing so the longevity of the pump can be improved.
• In an embodiment, the gear pump includes a face plate having the first port and the second port; an inner plate, the inner plate and the face plate defining the pump chamber between them; a seal around the pump chamber between the inner plate and the face plate, for example an O-ring, and the inner plate has a central opening within the seal to provide a fluid path between the pump chamber and the drive chamber and wherein the drive shaft passes through the central opening to drive the gears.
• In this way, the pump chamber is sealed with a removable seal so that the pump can be manufactured by providing suitable gears and then mounting the face plate to the inner plate and sealing.
• A motor plate may be provided on the opposite end of the gear pump to the face plate, the stator being provided between the motor plate and the rotor plate. The stator may be a sealed unit extending around the drive chamber, one end of the drive chamber being sealed by the motor plate and the other end of the drive chamber being externally sealed against the motor plate.
• The motor chamber may sealed with a permanent seal, since it is not generally necessary to provide separate access. The permanent seal may be glue.
• Screws passing through the motor plate and face plate may be used to compress the motor plate towards the face plate to hold the gear pump together.
• Conveniently, the screws may pass longitudinally through flanges extending radially outwards from the inner plate and motor plate.
BRIEF DESCRIPTION OF DRAWING
• For a better understanding of the invention, an embodiment will now be described, purely by way of example, with reference to the accompanying drawing.
• FIG. 1 shows an exploded perspective view of a gear pump according to an embodiment of the invention.
DETAILED DESCRIPTION
• Aface plate2 is formed to have opposedflanges4 and throughholes6,8 which function as ports to the gear pump. Location throughholes14 are provided forlocation pins28 which keep the different components of the gear pump in alignment.
• An O-ring seat10 is formed on the inner face of theface plate2, together withaxle holes12 for holdingaxle26 and driveshaft48 which supportgears16.
• Inner plate20 hascentral cutout22 for holding thegears16 as well as location throughholes14.
• Central plate24 has a central throughhole26 for thedrive shaft48 as well as location throughholes14 and anaxle hole12 for holdingaxle26 supporting one of thegears16.
• Stator30 is mounted oncentral plate24 and is a fully sealed unit arranged as a cylinder around acentral drive chamber32. Thestator30 includes a plurality of electrical coils.Motor plate34 forms the opposite end of the gear pump toface plate2 and is provided withflanges36 with threaded throughholes38.
• Rotor40 is shaped to rotate inside thedrive chamber32 and mounted on bushes42, one of which is mounted inmotor plate34 and the other of which is incentral plate24.
• The gear pump is held together withscrews44 which pass through theflanges4 on theface plate2 and screw into the threadedholes38 onmotor plate34. A pump chamber21 is formed, sealed by O-ring18 in O-ring seat10 which defines the lateral extent of the pump chamber21 and allows theface plate2 to be assembled separately during manufacture. This allows the use of different gears for different applications.
• Inlet46 and outlet47 mountings with end fittings for a tube are mounted to connect to inlet andoutlet ports6,8.
• One of thegears16 is mounted onaxle26, theaxle26 having one end supported onaxle hole12 in theface plate2 and the other onaxle hole12 in thecentral plate24.
• Theother gear16 is mounted on thedrive shaft48 which has one end supported on theother axle hole12 in theface plate2 and which is connected to therotor40.
• Theface plate2,inner plate20 andcentral plate24 are kept in alignment bylocation pins28 passing through location throughholes14 in those plates.
• The motor, i.e. thecentral plate24,stator30 andmotor plate34 are sealed using glue. Further, thecentral plate24 is sealed to theinner plate20 with glue.
• In use, thestator30 is driven electrically to driverotor40 which turns thegears16 in thepump chamber22 to pump fluid from the inlet to the outlet.
• Conventionally, seals have been provided in gear pumps to fully seal the motor from the pump chamber. In the present case however a fully sealedstator30 is used, thedrive chamber32 in which therotor40 sits is sealed bymotor plate34 but there is no seal alongdrive shaft48 between thepump chamber22 and thedrive chamber32.
• This allows fluid to enter thedrive chamber32 to act as a lubricant.
• The design is arranged for easy manufacture using standard components. Indeed, the various component parts are commercially available. In particular, the motor formed by thecentral plate24,stator30,drive rotor40 andmotor end plate34 is commercially available.
• Further, the use of glue for the motor to sealinner plate20,central plate24,stator30 and motor plate (34) is cheap and provides an efficient seal while the use of an O-ring to seal the pump chamber allows for flexible manufacturing with different gears for different applications.
• The design delivers a reliable long life by the use of a brushless electric motor.
• Those skilled in the art will realise that different components, plates and motors may be substituted for those described above.

Claims (9)

1. A gear pump for pumping a pump fluid, comprising

a pump chamber (21) having a first port (6) and a second port (8), and a pair of gears (16) mounted for rotation in the pump chamber for driving pump fluid between the first port (6) and second port (8);

a motor comprising a rotor (40) and a drive shaft (48) connected to the rotor to drive the pair of gears, the drive shaft and rotor being arranged in a drive chamber (32), the motor further comprising a stator arranged around the drive chamber (30);

wherein the pump chamber (21) and the drive chamber (32) are connected to allow pump fluid to pass between them.

2. A gear pump according toclaim 1, comprising:

a face plate (2) having the first port (6) and the second port (8);

an central plate (24), the central plate (24) and the face plate (2) defining the pump chamber (21) between them;

wherein the central plate (24) has a central opening to provide a fluid path between the pump chamber and the drive chamber and wherein the drive shaft passes through the central opening to drive the gears.

3. A gear pump according toclaim 2 further comprising an inner plate (22) sealed to the face plate with an O-ring (18).

4. A gear pump according toclaim 2, further comprising a motor plate (34) on the opposite end of the gear pump to the face plate, the stator (30) being provided between the motor plate (34) and the central plate (24).

5. A gear pump according toclaim 4, wherein the stator (30) is a sealed unit extending around the drive chamber (32), one end of the drive chamber being sealed by the motor plate (34) and the other end of the drive chamber being externally sealed against the central plate (24).

6. A gear pump according toclaim 4 wherein the central plate (24) and motor plate (34) are sealed to the stator (30) with a permanent seal.

7. A gear pump according toclaim 6 wherein the permanent seal is glue.

8. A gear pump according toclaim 4, further comprising a plurality of screws (44) passing through the motor plate (34) and face plate (2) arranged in tension to hold urge the face plate (2) towards the motor plate (34).

9. A gear pump according toclaim 8 wherein the face plate (2) and the motor plate (34) have flanges (4,36) extending radially outwards from the plate, the screws (44) passing through the flanges.

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