EP3786416A1

EP3786416A1 - Self-aligning gear pump

Info

Publication number: EP3786416A1
Application number: EP19194371.1A
Authority: EP
Inventors: Thomas Michael Wollmann
Original assignee: Individual
Current assignee: Individual
Priority date: 2019-08-29
Filing date: 2019-08-29
Publication date: 2021-03-03
Anticipated expiration: 2039-08-29
Also published as: DK3786416T3; ES2902419T3; EP3786416B1

Abstract

Disclosed herein is a gear pump (100) for pumping a fluid (404). The gear pump comprises: a sealed internal chamber (102); a pumping chamber (104) within the sealed internal chamber; a first pump port (122) fluidically connected to the pumping chamber; a second pump port (114) fluidically connected to the pumping chamber; a drive gear (120) within the pumping chamber; an idler gear (122) within the pumping chamber, wherein the drive gear and the idler gear are configured for pumping the fluid between the first pump port and the second pump port; a drive shaft (124) coupled to the drive gear, wherein the drive shaft is configured for rotationally driving the drive gear, wherein the drive shaft is within the sealed internal chamber; an idler shaft (126) coupled to the idler gear, wherein the idler shaft is within the sealed internal chamber, wherein the idler gear is coupled to the idler shaft; a pump housing (106, 108, 110) formed from a first housing element (106), a central housing element (108), and a second housing element (110), wherein the central housing element is positioned between the first housing element and the second housing element, wherein the first housing element, the second housing element and the central housing element form at least a portion of the sealed internal chamber, wherein the pumping chamber is formed entirely within the central housing; a first drive shaft bearing (128), wherein the first drive shaft bearing is mounted partially within the first housing element; a second drive shaft bearing (130), wherein the second drive shaft bearing is mounted partially within the second housing element, wherein the first drive shaft bearing and the second drive shaft bearing both partially extends into and align the drive gear with the pumping chamber; a first idler shaft bearing (132), wherein the first idler shaft bearing is mounted partially within the first housing; a second idler shaft bearing (134), wherein the second idler shaft bearing is mounted partially within the second housing element, wherein the first idler shaft bearing and the second idler shaft bearing both partially extends into the pumping chamber and align the idler gear with the pumping chamber.

Description

Field of the Invention

The present invention relates to pumps and pumping systems, in particular to gear pumps.

Background

Gear pumps use a drive gear and an idler gear to pump a fluid between a first pump port and a second pump port.
European Patent EP 2 282 059 a pump with a gear pump assembly having an adapter spool mounted to an electric motor. The pump assembly is designed to reduce manufacturing costs and to provide access for many service and maintenance tasks to be performed without breaking any of the pipe connections. The pump assembly also includes a splined shaft system and a lubricating fluid circulation system with spiral grooves located inside a pair of bearings disposed on opposite sides of the gear flights. The assembly also includes a replaceable precision liner that surrounds the gear flights to maintain a tight tolerance for optimal performance of the pump. Also, an O-ring disposed inside the front cover of the assembly provides for operation of the pump over a wide temperature variation with relatively loose manufacturing tolerances.

Summary

The invention provides for a gear pump, a chemical feed system for a waste water treatment plant, and a waste water treatment plant in the independent claims. Embodiments are given in the dependent claims.
A problem which most gear pumps exhibit is the need to maintain tight tolerances between the gears and the wall of the pumping chamber. If the gears are too close they will contact the wall and the gears and/or the pumping chamber will become worn. If the gears are too far away from the wall, then the pump will not function efficiently or pump well. In European Patent EP 2 282 059 a replaceable liner surrounds the gear flights to maintain this tolerance. The liner is a standard component on such gear pumps.
Embodiments may provide for a pump that maintains a tight tolerance between the gears of the gear pump without the use of a replaceable liner. This is achieved by modifying the design of the gear pump. The housing is divided into three portions first housing element, the central housing element, and the second housing element.
The drive gear is mounted on a drive shaft and the idler gear is mounted on an idler shaft. The drive shaft is supported by a first drive shaft bearing and a second drive shaft bearing. The first drive shaft bearing and the second drive shaft bearing sets the tolerances between the drive gear and the wall of the pumping chamber. The first drive shaft bearing is partially mounted in the first housing element and the second drive shaft bearing is partially mounted in the second housing element. A portion of the pumping chamber has a profile that matches the profile of the first drive shaft bearing and the second drive shaft bearing. The first drive shaft bearing and the second drive shaft bearing both partially extend into the pumping chamber. his has two effects. Firstly, it aligns the first housing element, the central housing element, and the second housing element. More importantly, this causes the tolerance between the drive gear and the wall of the pumping chamber to be fixed. This eliminates wear between the drive gear and the wall of the pumping chamber and eliminates the need for a replaceable liner. Likewise, The idler shaft is supported by the first idler shaft bearing and a second idler shaft bearing. The first idlers shaft bearing and the second idler shaft bearing control the tolerance between the idler gear and the wall of the pumping chamber in an analogous fashion.
In one aspect the invention provides for a gear pump for pumping a fluid. The pump comprises a sealed internal chamber. The gear pump further comprises a pumping chamber within the sealed internal chamber. The gear pump further comprises a first pump port fluidically connected to the pumping chamber. The gear pump further comprises a second pump port fluidically connected to the pumping chamber. The gear pump further comprises a drive gear within the pumping chamber. The gear pump further comprises an idler gear within the pumping chamber. The drive gear and the idler gear are configured for pumping fluid between the first pump port and the second pump port. The direction of the pumping may be dependent upon the rotational direction of the drive gear and the idler gear.
The gear pump further comprises a drive shaft coupled to the drive gear. The drive shaft is configured for rotationally driving the drive gear. The drive shaft is within the sealed internal chamber. The gear pump further comprises an idler shaft that is coupled to the idler gear. The idler shaft is within the sealed internal chamber. The idler gear is coupled to the idler shaft. When the drive shaft rotates it causes the drive gear to rotate also. The drive gear and idler gear mesh together and rotation of the drive gear causes the idler gear to rotate also.
The gear pump further comprises a pump housing formed from a first housing element, a central housing element, and a second housing element. The central housing element is positioned between the first housing element and the second housing element. For example there may be bolts which run through the three housing elements and cause the first housing element and the second housing element to compress the central housing element.
The first housing element, the second housing element, and the central housing element form at least a portion of the sealed internal chamber. The pumping chamber is formed within the central housing.
The gear pump further comprises a first drive shaft bearing. The first drive shaft bearing is mounted partially within the first housing element. The gear pump further comprises a second drive shaft bearing. The second drive shaft bearing is mounted partially within the second housing element. The first drive shaft bearing and the second drive shaft bearing both partially extend into and align the drive gear with the pumping chamber. The gear pump further comprises a first idler shaft bearing. The first idler shaft bearing is mounted partially within the first housing. The gear pump further comprises a second idler shaft bearing. The second idler shaft bearing is mounted partially within the second housing element. The first idler shaft bearing and the second idler shaft bearing both partially extend into the pumping chamber and align the idler with the pumping chamber.
The gear pump may have the advantage that wear between the drive gear and the idler gear with other components of the gear pump is reduced. When gear pumps are manufactured they typically use a liner to surround and fill the pumping chamber. This is a piece which may be removed when it becomes worn. For a gear pump to function there needs to be a tight tolerance between the drive and idler gear and the surrounding pumping chamber. This is so that there is sufficient pumping pressure. If the space between the drive gear and idler gear and the pumping chamber is too large then the gear pump will not be able to effectively pump fluid. To ensure this a liner is typically installed. However, tolerances within the pump mean that the gear liner may become worn and may need to be replaced. Embodiments of the gear pump may not have this problem because the various shaft bearings align the drive and idler gears with the pumping chamber. This enables to have extremely close tolerances that will avoid the problem of the drive gear and the idler gear wearing away the pumping chamber. This may for example eliminate the need for the use of a liner. This may in turn reduce the maintenance costs in maintaining the gear pump.
In another embodiment the first drive shaft bearing has a cylindrical profile. The second drive shaft bearing has the cylindrical profile. The first idler shaft bearing has the cylindrical profile. The second idler shaft bearing has the cylindrical profile. The central housing element has a first cylindrical cut out configured for receiving the first drive shaft bearing and the second drive shaft bearing. The central housing element has a second cylindrical cut out configured for receiving the first idler shaft bearing and the second idler shaft bearing. The cylindrical profile defines the clearance between the drive gear and the pumping chamber and between the idler gear and the pumping chamber. In this embodiment the relation of the bearings to the pumping chamber enable close tolerances for the drive and idler gear with respect to the pumping chamber to be maintained.
In another embodiment the first drive shaft bearing comprises a first flat surface parallel to a rotational axis of the drive shaft. The second drive shaft bearing comprises a second flat surface parallel to the rotational axis of the drive shaft. The first idler shaft bearing comprises a third flat surface parallel to the rotational axis of the idler shaft. The second idler shaft bearing comprises a fourth flat surface parallel to the rotational axis of the idler shaft. The first flat surface mates with the third flat surface. The second flat surface mates with the fourth flat surface. This embodiment may be beneficial because each end of both the drive shaft and idler shaft have independent bearings. However, these bearings have flat surfaces which mate with each other. This enables the bearings and the shafts to have a slight misalignment within the first housing element and the second housing element. However, this flexibility in the tolerances enables the tolerances between the drive gear and the idler gear in the pumping chamber to be very accurate and to be maintained. The pump is constructed in such a way that the tolerances between the pumping chamber and the drive gear and idler gear are very accurate and any misalignments are compensated for in the other components of the pump.
In another embodiment the first flat surface comprises at least one fluid channel. The second flat surface comprises the least one fluid channel. The third flat surface comprises the at least one fluid channel. The fourth flat surface comprises at the least one fluid channel.
In another embodiment the first pump port and the second pump port are mounted on one of the first housing element and the second housing element. The one of the first housing element and the second housing element comprises a first fluid conduit connecting the first pump port with the pumping chamber. The one of the first housing element and the second housing element comprises a second conduit channel connecting the second pump port with the pumping chamber. This embodiment may be beneficial because the first housing element or the second housing element may be larger or structurally more stable than the central housing element. This may also enable the mounting of the first pump port and the second pump port in a more convenient location.
In another embodiment the first housing element is formed from a cylinder. The central housing element is also formed from a cylinder. The second housing element is also formed from a cylinder. For example the pumping chamber and/or portions of the sealed internal chamber can be machined from the first housing element, the central housing element, and the second housing element.
In another embodiment a first O-ring seals the first housing element and the central housing element to form at least a portion of the sealed inner chamber. A second O-ring seals the second housing element and the central housing element to at least partially form the sealed inner chamber. The use of the O-rings may provide for a convenient means of sealing the first housing element, the central housing element, and the second housing element to form the sealed inner chamber.
In another embodiment the central housing element is compressed between the first housing element and the second housing element by bolts to seal the first O-ring seal and the second O-ring seal. This may provide for a convenient means of assembling the gear pump.
In another embodiment the pump housing further comprises a containment can for forming a magnetic coupler receptacle with the sealed internal chamber. The pump housing further comprises an internal magnetic coupler located within the magnetic coupler receptacle. The internal magnetic coupler is cylindrical. The internal magnetic coupler is connected to the drive shaft. The pump housing further comprises an external magnetic coupler located outside of the sealed internal chamber. The external magnetic coupler comprises a cylindrical cavity. At least a portion of the containment can is located within the cylindrical cavity. The external magnetic coupler is configured for rotationally coupling to the internal magnetic coupler. The gear pump further comprises a motor configured for rotating the external magnetic coupler.
In another embodiment the gear pump is configured for pumping a corrosive fluid. The use of a gear pump may be beneficial because the flow rate of the gear pump can be readily controlled by controlling the rotation rate of the drive gear and the idler gear. This means that the gear pump may be useful for dispensing both very small amounts of the fluid as well as larger amounts.
In another embodiment the first drive shaft bearing, the second drive shaft bearing, the first idler shaft bearing, and the second idler shaft bearing are formed from any one of the following: a conductive plastic, a plastic, a non-conductive plastic with conducting particles, a semi-conducting ceramic, and carbon graphite. The use of any one of these materials may be beneficial because they are electrically conductive. This may mean that the gear pump can be used in a location where there is a danger of sparks igniting gases or other fluids.
In another embodiment the first housing element, the second housing element, the central housing element, the gear drive, the idler gear are formed from any one of the following: the conductive plastic, a non-conductive plastic with conducting particles, the semi-conducting ceramic, and combinations thereof. The use of these materials also may be useful for reducing the chances of a spark causing a fire or explosion.
In another embodiment the drive shaft and the idler shaft is formed from the semi-conducting ceramic. This again may be beneficial in reducing the chances of a spark causing a fire or explosion due to use of the gear pump.
In another embodiment, the non-conducting plastic is Teflon. Teflon is also known as PTFE or polytetrafluorethen. The use of Teflon or PTFE may be beneficial because Teflon has an extremely high resistance to corrosive materials.
In another embodiment, the non-conducting plastic is polypropylene. Polypropylene is not as resistant to a larger variety of corrosive fluids as Teflon is but may have the advantage of being less expensive.
In accordance with embodiments of the invention, the non-conducting plastic is a thermoplastic polymer. In general, thermoplastic polymers may have some degree of corrosion resistance to a variety of corrosive fluids such as ammonia, sulfuric acid, chlorine, sodium hydroxide solution, organic or inorganic chemicals, catalysts and/or sea water. Thermoplastic polymers comprise polypropylene (PP), poly(methyl methacrylate) (PMMA), Acrylonitrile butadiene styrene (ABS), Polylactic acid (polylactide), Polycarbonate (PC), Polyether sulfone (PES), Polyetherketone (PEEK), Polyetherimide (PEI), Polyethylene (PE), in particular Ultra-high molecular weight polyethylene (UHMWPE), Polyp Polyvinyl chloride (PVC) henylene oxide (PPO), Polyphenylene sulfide (PPS), and polymer polytetrafluoroethylene (PTFE) that is also referred to as Teflon, or a combination thereof. Depending on the electrical properties of the selected thermoplastic or mixture of thermoplastics the addition of conductive particles may or may not be required for the explosion prevention.
In another embodiment, the conducting particles comprise graphite. In particular the non-conducting plastic may be a Teflon with 25% graphite suspended or dispersed within the surface. The graphite can also be mixed into polypropylene or into thermoplastic polymers in general. The combination of the graphite may provide for a material that both has high resistance to corrosive fluids and is also able to conduct electricity to disperse static buildup of electricity.
In another embodiment, the conducting particles may comprise carbon-nanotubes. The use of carbon-nanotubes is comparable to the use of graphite as the carbon-nanotubes have a high conductivity and thus enable a discharge of static electricity.
In another embodiment, the semi-conducting ceramic is a silicon carbide material, such as sintered and/or carbon fiber reinforced silicon carbide and/or carbon fiber reinforced silicon carbide composite. The use of silicon carbide ceramics may be beneficial because silicon carbide is both a semi-conductor which allows the dispersion of static electricity and also has extremely high resistance to a wide variety of corrosive fluids. This enables the construction of a pump that is safer than known pumps.
The internal and external magnetic couplers can be formed in a variety of different ways. In many instances the internal magnetic coupler and the external magnetic coupler both use permanent magnets. This however is not necessary. There may for example be permanent magnets in just the internal magnetic coupler or the external magnetic coupler and the other uses a material which is able to be magnetized. In yet other examples, the external magnetic coupler uses an electromagnetic which then either couples to a permanent magnet in the internal magnetic coupler or to a magnetizable material.
In some examples the permanent magnets, particularly within the internal magnetic coupler are in the form of rare earth magnets and/or ceramic magnets. The use of a rare earth and/or ceramic magnet may be beneficial because it may have more resistance to the corrosive fluid.
In one example an NdFeB permanent magnet is used within the internal magnetic coupler and/or the external magnetic coupler.
In one example the permanent magnet within the internal magnetic coupler is Samarium Cobalt (SmCo).
These types of magnets may be advantageous because of both a high resistance to corrosion and also a high resistance to heat. The use of a rare earth magnet and/or ceramic magnet, such as a NdFeB permanent magnet and/or samarium cobalt magnet, within the internal magnetic coupler may enable a greater range of operational temperatures and also the use of better or more aggressive corrosive fluids that are being pumped with or even without encapsulation of the magnets.
In another embodiment, the containment can is non-metallic. This may have the advantage that no magnetic or any current losses occur which would cause a heat input to the pump.
In another embodiment, the magnetic coupler receptacle is cylindrically-shaped. The cylindrical axis of rotation may for example be identical with the axis of rotation of the drive shaft. The magnetic receptacle comprises an end cap. The end cap may be dome-shaped. This embodiment may be beneficial because the dome shape may provide for higher operating pressures within the pump.
In another embodiment, the pump housing is formed by machining. This may be beneficial because it may provide for a means of reducing the cost of producing custom for individual pumps.
In another embodiment, the rotational pumping element is formed by machining. This also may be beneficial because it may reduce the cost of producing low numbers or custom pumps.
In another embodiment, the pumping chamber is formed by machining. This embodiment may be beneficial because it may provide for a cost-effective means of reducing the cost of small number or custom pumps.
In another embodiment, the sealed internal chamber is formed by machining. This embodiment may be beneficial because it may provide for a means of reducing the cost of producing low numbers of pumps or custom pumps.
In another embodiment, the at least one bearing may be constructed by machining. This may have the advantage of being able to provide for reduced cost when manufacturing custom or low quantities of particular pumps.
In another embodiment, the pump has a pumping capacity of 1 liter per hour or greater.
In another embodiment, the pump has a pumping capacity of 100 liters per minute or greater.
In another embodiment, the pump has an operating temperature of at least 65°C. In some embodiments, this temperature may be much higher.
In another embodiment, the system pressure of the pumping chamber may be n bars or less.
In another embodiment, the system or operating pressure may be 15 bars or less.
In another embodiment, the system pressure may be 16 bars or less.
In another embodiment, the system pressure may be 20 bars or less.
In another embodiment, the differential pressure between the pump inlet and the pump outlet may be 5 bars or less.
In another embodiment, the differential pressure may be 10 bars or less.
In another embodiment, the differential pressure may be 20 bars or less.
In another embodiment, the flow or pumping rate of the pump may be 4.5 m³ per hour or less.
In another embodiment, the flow or pump rate may be 10 m³ per hour or less.
In another aspect the invention provides for a chemical feed system for a waste water treatment plant that comprises a pump according to an embodiment and a chemical reservoir configured for storing a fluidic chemical. The pump is configured for pumping the fluidic chemical from the chemical reservoir to a flow stream of the waste water treatment plant. This embodiment may be beneficial because the gear pump may have an ability to pump a large difference in the volume of the fluidic chemical. For example if the drive gear is rotated at a low rate then a very slow flow rate of the fluidic chemical is produced. If however the rate of rotation of the drive gear is increased, then this pumping rate of the fluidic chemical will increase.
This is useful in waste water treatment plants because during rain or other situations where there is an increase in the water going through the plant, the amount of the fluidic chemical might need to be greatly increased. This is typically accomplished by having a large number of pumps available to the waste water treatment plant that are not used very often. The use of the gear pump may enable fewer pumps to be installed into a waste water treatment plant. The use of a fewer number of pumps is also beneficial because this reduces the amount of maintenance needed to maintain the pumps in a ready state.
In another aspect the invention provides for a waste water treatment plant that comprises the chemical feed system.

Brief description of the drawings

In the following embodiments of the invention are explained in greater detail, by way of example only, making reference to the drawings in which:

Fig. 1: illustrates and example of a gear pump;
Fig. 2: illustrates an example of a bearing using in the gear pump;
Fig. 3: shows a idealized representation of the pumping chamber of the gear pump; and
Fig. 4: illustrates an example of a waste water treatment plant.

Detailed Description

Like numbered elements in these figures are either equivalent elements or perform the same function. Elements which have been discussed previously will not necessarily be discussed in later figures if the function is equivalent.
Fig. 1 illustrates an example of a gear pump 100. The gear pump 100 comprises a sealed inner chamber 102. Within the sealed inner chamber 102 is a pumping chamber 104. The sealed inner chamber 102 is formed by a first housing element 106, a central housing element 108, and a second housing element 110 at least partially. Shown is a first pump port 112 and a second pump port 114. The second pump port 114 is not visible. The first pump port 112 is connected to the pumping chamber 104 by the first fluid conduit 116. The second pump port 114 is connected to the pumping chamber 104 via a second fluid conduit 118.
The gear pump 100 further comprises a drive gear 120 and an idler gear 122. Rotation of the drive gear 120 and idler gear 122 provide the pumping action between the first pump port 122 and the second pump port 114. The drive gear 120 is mounted on a drive shaft 124. The idler gear 122 is mounted on an idler shaft 126.
The gear pump 100 is further shown as comprising a first drive shaft bearing 128 and a second drive shaft bearing 130. The first drive shaft bearing 128 and the second drive shaft bearing 130 enables the drive shaft 124 to rotate. The gear pump 100 is also shown as containing a first idler shaft bearing 132 and a second idler shaft bearing 134. The first idler shaft bearing 132 and the second idler shaft bearing 134 enable the idler shaft 126 to rotate. The first drive shaft bearing 128 and the first idler shaft bearing 132 are mounted at least partially within the first housing element 106. The second drive shaft bearing 130 and the second idler shaft bearing 134 are mounted at least partially within the second housing element 110. A portion of the first drive shaft bearing 128, the second drive shaft bearing 130, the first idler shaft bearing 132, and the second idler shaft bearing 134 extend into the pumping chamber 104. This causes the first housing element 106, the central housing element 108, and the second housing element 110 to be aligned with each other. In particular the extension of the bearings 128, 130, 132, 134 into the pumping chamber 104 causes a very precise alignment and control of tolerances between the drive gear 120 and the pumping chamber 104 as well as the idler gear 122 with the pumping chamber 104.
The pumping chamber 104 has a first cylindrical cutout 160 which matches the profile of the first drive shaft bearing 128 and the second drive shaft bearing 130. The pumping chamber 104 also has a second cylindrical cutout 162 which matches the profiled of the first idler shaft bearing 132 and the second idler shaft bearing 134.
The first drive shaft bearing 128 has a first flat surface 136. The second drive shaft bearing 130 has a second flat surface 138. The first idler shaft bearing 132 has a third flat surface 140 and the second idler shaft bearing 134 has a fourth flat surface 142. In many gear pumps the bearings 128 and 132 would be combined as one piece as well as combining pieces 130 and 134. In this pump instead these bearings are separate. The first and third flat surfaces 136 and 140 are in contact when the pump is assembled. The second flat surface 138 and the fourth flat surface 142 are also in contact when the pump is assembled. This enables a larger degree of play or misalignment between the various bearings 128, 130, 132, 134 and the shafts 124, and 126. This however enables a very tight tolerance between the drive gear 120 and idler gear 122 with the pumping chamber 104.
A first O-ring 144 is used to seal the first housing element 106 against the central housing element 108. A second O-ring 146 is used to seal the central housing element 108 against the second housing element 110. Also can be seen in the drawing are two spacers 148. The spacers are inserted into the same space that the bearings 128 and 132 are inserted into as well as bearings 130 and 134 into the second housing 110. These are used to prevent the bearings 128, 130, 132, 134 for being completely flush against the first housing element 106 or the second housing element 110. The pump 110 is further shown as comprising a motor 150 and a mounting flange 152. The mounting flange 152 adapts the other components of the gear pump 100 to mount on the motor 150.
The gear pump 100 is further shown as comprising a magnetic coupler receptacle 154 formed from a containment can 156 and an internal magnetic coupler 156. The containment can 155 is sealed to the second housing element 110 by an O-ring 158. The drive shaft 124 extends and connects to the internal magnetic coupler 156. An external magnetic coupler 160 is shown as being connected to the motor 150. When the external magnetic coupler 160 rotates it causes the internal magnetic coupler 156 to rotate also which in turn causes the drive shaft 124 and drive gear 120 to turn. The drive gear 120 in turn causes the idler gear 122 and idler shaft 126 also to rotate. This provides the pumping action. The bolts 162 go through the housing elements 106, 108, 110 and connect to the threaded holes 164 on the mounting flange 152. This compresses the elements 106, 108, 110 and seals them with the O- rings 144 and 146.
The mounting flange 152 is connected to the motor 150 using the bolts 166. The bolts go through the flange 152 and are screwed into the threaded holes 168.
Fig. 2 shows a Fig. which illustrates an example of a bearing. This bearing may be used for the first drive shaft bearing 128, the second drive shaft bearing 130, the first idler shaft bearing 132 and the second idler shaft bearing 134. The bearings all have a flat surface 136, 138, 140, 142. There is a cylindrical bearing receptacle 202 for receiving either the drive shaft 124 or the idler shaft 126. There are fluid channels 204 cut into the flat surface 136, 138, 140, 142 that enable fluid pressure to be released readily through the bearing 128, 130, 132, 134. This may for example be beneficial when the pump is running in a dry state. Within the bearing receptacle 202 there are also lubrication grooves 206. The lubrication grooves 206 enable fluid to reach the surface of the bearing receptacle 202 and help the shafts 124 and 126 to rotate.
Fig. 3 shows an idealized diagram of a gear pump 100. The drawing is not to scale and not all details are shown. Fig. 3 illustrates how the bearings 128, 130, 132, 134 control the tolerances between the gears 120, 122 and the wall of the pumping chamber 170, 172.
The drive shaft 124 is showing as having a rotation axis 300. The idler shaft 126 has a rotational axis 302.
The pumping chamber 104 has a first cylindrical cutout 170 which matches the profile of the first drive shaft bearing 128 and the second drive shaft bearing 130. The pumping chamber 104 also has a second cylindrical cutout 172 which matches the profiled of the first idler shaft bearing 132 and the second idler shaft bearing 134. The first drive shaft bearing 128, the second drive shaft bearing 130, and the first idler shaft bearing 132, and the second idler shaft bearing 134 all extend partially into the pumping chamber 104. This causes the first housing element 106, the central housing element 108, and the second housing element 110 to align. Additionally the bearings 128, 130, 132, 134 cause the gears 120, 122 to have a precise tolerance with the wall 170, 172 of the pumping chamber 104.
Fig. 4 illustrates an example of a waste water treatment plant. The waste water treatment plant comprises a chemical feed system 402. The chemical feed system 402 is configured to supply a fluidic chemical 404 from a reservoir to a flow stream 406 of the waste water treatment plant 400. The chemical feed system 402 comprises a pump 100 according to an example. An advantage of using the gear pump 100 is that by controlling the rotation rate of the motor 150 a very large or small amount of the fluidic chemical 404 can be dispensed.
Waste water treatment plants can have a large variation in how much waste water treatment plant treats or cleans. A large increase in the volume of water to be treated can for example be caused by rainfall or other surges of water into the system. To cope with these variations, waste water treatment plants typically have additional pumps on standby. This can be very expensive because the pumps need to be maintained to ensue that they will function when there is a surge of water to be treated. Using a gear pump may reduce the number of pumps which are required. A gear pump can pump at a low flow rate, or if need by the rotational rate of the motor can be increased to pump a larger volume of the fluidic chemical on demand.

List of Reference Numerals

100: gear pump
102: sealed inner chamber
104: pumping chamber
106: first housing element
108: central housing element
110: second housing element
112: first pump port
114: second pump port
116: first fluid conduit
118: second fluid conduit
120: drive gear
122: idler gear
124: drive shaft
126: idler shaft
128: first drive shaft bearing
130: second drive shaft bearing
132: first idler shaft bearing
134: second idler shaft bearing
136: first flat surface
138: second flat surface
140: third flat surface
142: fourth flat surface
144: first O-ring
146: second O-ring
148: spacer
150: motor
152: mounting flange
154: magnetic coupler receptacle
155: containment can
156: internal magnetic coupler
158: O-ring
160: external magnetic coupler
162: bolts
164: threaded holes
166: bolts
168: threaded holes
170: first cylindrical cutout
172: second cylindrical cutout
200: cylindrical outer surface
202: bearing receptacle
204: fluid channel
300: rotational axis of drive shaft
302: rotational axis of idler shaft
400: waste water treatment plant
402: chemical feed system
404: reservoir of fluidic chemical
406: flow stream

Claims

A gear pump (100) for pumping a fluid (404), wherein the gear pump comprises:
- a sealed internal chamber (102);

- a pumping chamber (104) within the sealed internal chamber;

- a first pump port (122) fluidically connected to the pumping chamber;

- a second pump port (114) fluidically connected to the pumping chamber;

- a drive gear (120) within the pumping chamber;

- an idler gear (122) within the pumping chamber, wherein the drive gear and the idler gear are configured for pumping the fluid between the first pump port and the second pump port;

- a drive shaft (124) coupled to the drive gear, wherein the drive shaft is configured for rotationally driving the drive gear, wherein the drive shaft is within the sealed internal chamber;

- an idler shaft (126) coupled to the idler gear, wherein the idler shaft is within the sealed internal chamber, wherein the idler gear is coupled to the idler shaft;

- a pump housing (106, 108, 110) formed from a first housing element (106), a central housing element (108), and a second housing element (110), wherein the central housing element is positioned between the first housing element and the second housing element, wherein the first housing element, the second housing element and the central housing element form at least a portion of the sealed internal chamber, wherein the pumping chamber is formed entirely within the central housing;

- a first drive shaft bearing (128), wherein the first drive shaft bearing is mounted partially within the first housing element;

- a second drive shaft bearing (130), wherein the second drive shaft bearing is mounted partially within the second housing element, wherein the first drive shaft bearing and the second drive shaft bearing both partially extends into and align the drive gear with the pumping chamber;

- a first idler shaft bearing (132), wherein the first idler shaft bearing is mounted partially within the first housing;

- a second idler shaft bearing (134), wherein the second idler shaft bearing is mounted partially within the second housing element, wherein the first idler shaft bearing and the second idler shaft bearing both partially extends into the pumping chamber and align the idler gear with the pumping chamber.
The gear pump of claim 1, wherein the first drive shaft bearing has a cylindrical profile (200), wherein the second drive shaft bearing has the cylindrical profile, wherein the first idler shaft bearing has the cylindrical profile, wherein the second idler shaft bearing has the cylindrical profile, wherein the central housing element has a first cylindrical cutout (170) configured for receiving the first drive shaft bearing and the second drive shaft bearing, wherein the central housing element has a second cylindrical cutout (172) configured for receiving the first idler shaft bearing and the second idler shaft bearing, wherein the cylindrical profile defines a clearance between the drive gear and the pumping chamber and between the idler gear and the pumping chamber.
The gear pump of claim 2, wherein the first drive shaft bearing comprises a first flat surface (136) parallel to a rotational axis of the drive shaft, wherein the second drive shaft bearing comprises a second flat surface (138) parallel to the rotational axis of the drive shaft, wherein the first idler shaft bearing comprises a third flat surface (140) parallel to a rotational axis of the idler shaft, wherein the second idler shaft bearing comprises a fourth flat surface (142) parallel to the rotational axis of the idler shaft, wherein the first flat surface mates with the third flat surface, and wherein the second flat surface mates with the fourth flat surface.
The gear pump of claim 3, wherein the first flat surface comprises at least one fluid channel (204), wherein the second flat surface comprises the at least one fluid channel, wherein the third flat surface comprises the at least one fluid channel, and wherein the fourth flat surface comprises the at least one fluid channel.
The gear pump of any one of the preceding claims, wherein the first pump port and the second pump port are mounted on one of the first housing element and the second housing element, wherein the one of the first housing element and the second housing element comprises a first fluid conduit (116) connecting the first pump port with the pumping chamber, and wherein the one of the first housing element and second housing element comprises a second fluid conduit (118) connecting the second pump port with the pumping chamber.
The gear pump of any one of the preceding claims, wherein the first housing element is formed from a cylinder, wherein the central housing element is formed from a cylinder, and wherein the second housing element is formed from a cylinder.
The gear pump of any one of the preceding claims, wherein a first O-ring (144) seal seals the first housing element and the central housing element to form at least a portion of the sealed inner chamber, and wherein a second O-ring (146) seals the second housing element and the central housing element to at least partially form the sealed inner chamber.
The gear pump of claim 7, wherein the central housing element is compressed between the first housing element and the second housing element by bolts to seal the first O-ring seal and the second O-ring seal.
The gear pump of any one of the preceding claims, wherein the pump housing further comprises:
- a containment can (155) for forming a magnetic coupler receptacle (154) within the sealed internal chamber,

- an internal magnetic coupler (156) located within the magnet coupler receptacle, wherein the internal magnetic coupler is cylindrical, wherein the internal magnetic coupler is connected to the drive shaft;

- an external magnetic coupler (160) located outside of the sealed internal chamber, wherein the external magnetic coupler comprises a cylindrical cavity, wherein at least a portion of the containment can is located within the cylindrical cavity, wherein the external magnetic coupler is configured for rotationally coupling to the internal magnetic coupler; and

- a motor (150) configured for rotating the external magnetic coupler.
The gear pump of any one of the preceding claims, wherein the gear pump is configured for pumping a corrosive fluid.
The gear pump of any one of the preceding claim, wherein the first drive shaft bearing, the second drive shaft bearing, the first idler shaft bearing, and the second idler shaft bearing are formed from any one of the following: a conductive plastic, a plastic, a non-conducting plastic with conducting particles, a semi-conducing ceramic, and carbon graphite.
The gear pump of claim 11, wherein the first housing element, the second housing element, the central housing element, the drive gear, idler gear, are formed from any one of the following: the conductive plastic, the non-conducting plastic with conducting particles, the semi-conducing ceramic, and combinations thereof.
The gear pump of claim 12, wherein the drive shaft and the idler shaft is formed from the semi-conducting ceramic.
A chemical feed system (402) for a waste water treatment plant comprising:
- a gear pump (100) according to any one of the preceding claims; and

- a chemical reservoir configured for storing a fluidic chemical (404), wherein the pump is configured for pumping the fluidic chemical from the chemical reservoir to a flow stream (406) of the waste water treatment plant.
A waste water treatment plant (400) comprising the chemical feed system (402) of claim 14.