GEAR PUMPS AND METHODS FOR USING GEAR PUMPS

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application Serial No. 61/123,545 filed April 09, 2008, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

[0002] The invention relates generally to pumps and particularly to gear pumps and methods of using the gear pumps.

Description of the Related Art

[0003] When compared to conventional pumps (e.g. centrifugal, rotary lobe, piston, diagram and screw pumps), gear pumps can function at higher operating pressures (>600 psi) and have the advantage of improved flow stability over a wide pressure range. Gear pumps are typically used in applications that require high pressure pumping of viscous materials. Gear pumps are also used in processes that have a varying range of flowable material viscosity such as a recirculation loop for a polymer reactor. Examples of pumping applications using include: (1) booster pump in plastic extrusion, (2) polymers and gums, (3) resins and glues, and (4) asphalt, tar and other extremely viscous materials. [0004] Existing gear pumps that operate at high pressures require that the bearings be placed at each side of each gear shaft to evenly support the hydraulic load. Typically, the bearings are placed in the product stream near the gears to affectively carry the load and allow the product to lubricate the bearings. Although this allows for lubrication, it does have two major disadvantages: (1) bearings can be susceptible to wear, particularly when the product being pumped contains hard or abrasive particles, and (2) the pumps are difficult to clean. These disadvantages become more apparent if the materials being pumped contain solids that are abrasive and/or materials that require sanitary equipment design (e.g. food or pharmaceutical products).

SUMMARY OF THE INVENTION

[0005] The present invention is generally directed to gear pumps and methods of using the gear pumps. In a general embodiment, the invention provides a pump comprising a gear housing defining a passage and having an inlet and an outlet and one or more gears contained within the gear housing. The gear comprises one or more bearings that are

movably engaged with the gear and allow the gear to freely rotate while providing a support for the gear. The bearing(s) can be separated from the passage of the gear housing by a seal.

[0006] In an embodiment, the bearing is contained within a bearing housing attached to the gear housing. In another embodiment, the bearing housing defines an inlet and an outlet and a reservoir containing the bearing.

[0007] In an embodiment, the gear comprises a shaft attached to a motor. In another embodiment, the bearing is part of a bearing assembly surrounding the shaft.

[0008] In an embodiment, the seal surrounds the shaft and is positioned between the gear and the bearing assembly.

[0009] In an embodiment, the pump further comprises a spring assembly surrounding the shaft and positioned between the seal and the bearing assembly.

[0010] In an embodiment, the gear comprises a studded, spur, helical or herringbone shape.

[0011] In another embodiment, the invention provides a pump comprising a gear housing defining a passage and having an inlet and an outlet and a first gear comprising a first shaft and contained within passage of the gear housing. The first gear comprises a first bearing assembly surrounding the first shaft. The first bearing assembly is separated from the passage of the gear housing by a first seal. The pump further comprises a second gear comprising a second shaft and contained within passage of the gear housing. The second gear comprises a second bearing assembly surrounding the second shaft. The second bearing assembly is separated from the passage of the gear housing by a second seal.

[0012] In an embodiment, the first bearing assembly and the second bearing assembly are contained within a bearing housing attached to the gear housing.

[0013] In an embodiment, the bearing housing defines an inlet and an outlet and a reservoir containing the bearing assemblies.

[0014] In an embodiment, at least one of the first shaft and the second shaft is attached to a motor.

[0015] In an embodiment, the first seal comprises a first seal surrounding the first shaft and positioned between the first gear and the first bearing assembly and the second seal comprises a second seal surrounding the second shaft and positioned between the second gear and the second bearing assembly.

[0016] In an embodiment, the pump further comprises a first spring assembly surrounding the first shaft and positioned between the first seal and the first bearing

assembly and a second spring assembly surrounding the second shaft and positioned between the second seal and the second bearing assembly.

[0017] In an alternative embodiment, the invention provides a pump comprising a gear housing defining a passage and having an inlet and an outlet. The pump also comprises a first gear attached to a first shaft extending from both sides of the first gear and contained within the passage of the gear housing. The first gear comprises a first bearing assembly and a second bearing assembly attached to the shaft on each side of the first gear. The first bearing assembly and the second bearing assembly are separated from the passage of the gear housing by a first seal and second seal, respectively. The pump further comprises a second gear attached to a second shaft extending from both sides of the second gear and contained within the passage of the gear housing. The second gear comprises a third bearing assembly and a fourth bearing assembly attached to the shaft on each side of the second gear. The third bearing assembly and the fourth bearing assembly are separated from the passage of the gear housing by a third seal and fourth seal, respectively. [0018] In an embodiment, the first and second bearing assembly and the first and second seal are contained within a first bearing housing attached to the gear housing and wherein the third and fourth bearing assembly and the third and fourth seal are contained within a second bearing housing attached to the gear housing.

[0019] In an embodiment, at least one of the first bearing housing and the second bearing housing defines an inlet and an outlet and a reservoir containing the bearing assemblies. [0020] In an embodiment, at least one of the first shaft and the second shaft is attached to a motor.

[0021] In an embodiment, the pump further comprises a first spring assembly surrounding the first shaft and positioned between the first seal and the first bearing assembly, a second spring assembly surrounding the first shaft and positioned between the second seal and the second bearing assembly, a third spring assembly surrounding the second shaft and positioned between the third seal and the third bearing assembly, and a fourth spring assembly surrounding the second shaft and positioned between the fourth seal and the fourth bearing assembly.

[0022] In yet another embodiment, the invention provides a method for pumping a material. The method comprises providing a pump comprising a gear housing defining a passage and having an inlet and an outlet and at least one gear contained within the gear housing, the gear comprising at least one bearing assembly movably engaged with the gear.

The bearing is separated from the passage of the gear housing by a seal. The method further comprises moving the material through the pump by rotating the gear.

[0023] In an embodiment, the bearing assembly is contained within a bearing housing attached to the gear housing. The bearing housing defines an inlet and an outlet and a reservoir containing the bearing.

[0024] In an embodiment, the method further comprises pumping a barrier fluid thorough the inlet of the bearing housing to control at least one of the temperature and the pressure within the bearing housing.

[0025] In an embodiment, the method further comprises monitoring the barrier fluid using a barrier fluid control system.

[0026] In an embodiment, the gear is rotated using a motor attached to a shaft attached to the gear.

[0027] An advantage of the invention is to provide an improved gear pump. Another advantage of the invention is to provide a gear pump in which the bearings of the pump do not come into contact with the product stream. Yet another advantage of the invention is to provide a pump that has improved sanitary conditions when used. Still another advantage of the invention is to provide an improved pump that can withstand high pumping pressures.

Yet another advantage of the invention is to provide an improved pump that can withstand high pumping temperatures. Another advantage of the invention is to provide an improved method for pumping a viscous material.

[0028] Other and further objects, features, and advantages of the invention will be readily apparent to those skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 illustrates a front perspective view of the pump in an embodiment of the invention.

[0030] FIG. 2 illustrates a cross-section view H-II of the pump in an embodiment of the invention.

[0031] FIG. 3 illustrates a front perspective view of the first bearing house and the second bearing house in an embodiment of the invention.

[0032] FIG. 4 illustrates a front perspective view of the gear housing in an embodiment of the invention.

[0033] FIG. 5 illustrates a cross-section view V-V of the pump in an embodiment of the invention.

[0034] FIG. 6 illustrates a front perspective view of the seal in an embodiment of the invention.

[0035] FIG. 7 illustrates a front perspective view of the spring assembly in an embodiment of the invention.

[0036] FIG. 8 illustrates an exploded front perspective view of the spring assembly in an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0037] The present invention is generally directed to gear pumps and methods of using the gear pumps. In a general embodiment, the gear pump has its bearings placed outside of the product stream of the gear pump. The product can be any suitable flowable material such as, for example, a material having a high solids content. The bearings do not contact the product as it flows through the pump and therefore are not susceptible to wear and tear caused by the product, particularly by abrasive particles in the product. Additionally, the design of the gear pump in alternative embodiments makes the pump easy to clean, and therefore sanitary conditions can be maintained when using the pump. This provides an improved gear pump that allows for one or more of the following: 1) reduced maintenance costs, 2) reduced factory downtime, 3) operation at extremely high operating pressures and temperatures, 4) ability to handle viscous products, and 5) improved flow stability [YA] [0038] The gear pumps of the invention can convey highly viscous materials. These materials may be in the form of light to heavy heating oils, lubricating oils, hydraulic fluids and synthetic oils. The materials may also be animal or vegetable fats and oils, sugar solutions, highly viscous polymers, viscous or acetate cellulose.

[0039] The gear pumps of the invention can also be used to convey and/or make food products such as, for example, food or pet food products in various manufacturing processes. For instance, the gear pumps can be used to pump or transport a food or pet food from one location to another during the manufacturing process. The gear pumps can also be used to manufacture food products by pressing a food or pet food mixture through one or more heat exchangers and/or extrusion dies using the gear pump. The food or pet food mixtures can be in the form of a dry, semi-moist or moist material having a high solids content.

[0040] In a general embodiment illustrated in FIGS. 1-5, the invention provides a pump 10 comprising a gear housing 20 defining a passage 22 and having an inlet 24 and an outlet 26 for a product to flow into and out of, respectively. The pump 10 also comprises a first

gear 30 attached to a first shaft 40 extending from one or both sides of the first gear 30. The first gear 30 is rotatable to move the product stream through the passage 22 of the pump 10. All or a portion of the first gear 30 is contained within the passage 22 of the gear housing 20.

[0041] The first gear 30 comprises one or more bearings 32. The bearings 32 can be part of a bearing assembly 34 that surrounds the first shaft 40. The bearing assembly 34 can support and hold the first shaft 40 in place while allowing the first shaft 40 to rotate freely. In another embodiment, the first gear 30 can also comprise one or more bearings 36 that are part of a separate bearing assembly 38 attached to the shaft 40 on an opposite side of the first gear 30.

[0042] The shaft 40 can be attached to the gear 30 in any suitable manner (e.g. adhesive, weld, mechanical faster). In an embodiment, the shaft 40 and the gear 30 comprise a single unitary piece made from the same material (e.g. iron, steel, high strength polymer). [0043] The bearing assembly 34 and/or the bearing assembly 38 can be separated from gear 30 and the passage 22 of the gear housing 20 by seals 50 and 52, respectively. The seals 50 and 52 can surround the first shaft 40. For example, the seals 50 and 52 can be located on the first shaft 40 between the bearing assemblies 34 and 38 and the flanks of the gear 30. By having the seals contacting or being near the flanks of the gear 30, a tight seal can be formed between the bearing assemblies 34 and 38 and the gear 30 located in the gear housing 20. Because of the design, any product stream moved by the rotating gear 30 will not be able to contact the bearing assemblies 34 and 38 as the product passes through the pump 10.

[0044] In an embodiment, the seals 50 and 52 can be mechanical ring-shaped seals that provide an air/fluid tight separation between the gear(s) and the product stream that is moved through the passage of the gear housing. These seals are designed to keep material from the product stream from entering a bearing housing or place where the bearings for the pump are located. These seals can also be used prevent barrier fluid from the bearing housing from entering the product stream in the pump passage. The seals 50 and 52 can be any suitable shape and configuration that separates the bearings 32 and 36 and the bearing assemblies 34 and 38 from the passage 22 of the gear housing 20.

[0045] The gear housing 20 can be designed to have a shape that eliminates any dead spaces, is streamlined and has highly polished surfaces to make it clean-in-place. This allows the pump 10 to have a highly hygienic design. The gear housing 20 can be made of

any suitable material suitable (e.g. iron, steel, high strength polymer). The inside of the gear housing can be coated with suitable material to prevent wear.

[0046] In an embodiment, the pump 10 further comprises another gear 60 attached to a second shaft 70 extending from both sides of the second gear 60 and contained within the passage 22 of the gear housing 20. The second gear 60 can work in conjunction with the first gear 30 to more effectively and efficiently move a product through the pump 10. The second gear 60 can comprise one or more bearings 62 in a manner similar to the first gear 30. For example, the bearings 62 can be part of a bearing assembly 64 that surrounds that second shaft 70. In another embodiment, the second gear 60 can also comprise one or more bearings 66 that are part of a separate bearing assembly 68 attached to the shaft 40 on an opposite side of the second gear 60.

[0047] The bearing assembly 64 and/or the bearing assembly 68 can be separated from the passage 22 of the gear housing 20 by seals 80 and 82 in a similar manner as previously discussed. The seal 80 can be any suitable shape and configuration that separates the bearings 62 and 66 and the bearing assemblies 64 and 68 from the passage 22 of the gear housing 20.

[0048] Any of the seals used in the pump in alternative embodiments can have a configuration as shown in FIG. 6, which shows a perspective view of a seal 150. In this embodiment, the seal 150 expands in diameter towards the outer side. The seal 150 comprises one or more recesses 152 to accommodate various mechanisms such as pins that are part of a spring assembly (see FIGS. 6-7) that can hold the seal in place as discussed in detail below. In another embodiment, the seal 150 may be used in conjunction with an O- ring that surrounds the outside circumference of the seal 150. The O-ring can be used to provide an additional seal.

[0049] Depending on the application, the gear(s) can have any suitable size and shape such as studded, spur, helical, herringbone or combinations thereof. The gear(s) can be made of any suitable materials and comprising any suitable coatings depending on the application. For example, different gear size diameters and widths can be utilized to optimize the pump design for different applications.

[0050] In an embodiment, the bearing assembly 34 and the bearing assembly 64 are contained within a bearing housing 90. The bearing housing 90 can be permanently or removably attached to the gear housing 20 using any suitable mechanism (e.g. screws,

fasteners, or adhesives). The seals 50 and 80 can also be contained within the bearing housing 90.

[0051] In another embodiment, the bearing assembly 38 and the bearing assembly 68 are contained within a bearing housing 92. The bearing housing 92 can be permanently or removably attached to the gear housing 20 using any suitable mechanism (e.g. screws, fasteners, or adhesives). The seals 52 and 82 can also be contained within the bearing housing 92.

[0052] In an embodiment, the bearing housing 90 and/or the bearing housing 92 define inlets 94 and 96 and corresponding outlets (not shown) and a reservoir. The reservoir within the bearing housings 90 and 92 can house the bearing assemblies and be used to house fluids such as barrier fluids for lubricating the bearings and/or controlling and maintaining temperatures and pressures within the bearing housings 90 and 92.

[0053] The bearing housings 90 and 92 can be uniquely designed to allow for easy assembly and disassembly for replacement of the bearings. In addition, the flow path of the barrier fluid used to lubricate and maintain the temperature of the bearings can be designed to maintain consistent barrier fluid flow. The barrier fluid flow path can also be changed depending on the orientation of the pump head. This flexibility allows the pump barrier fluid flow path to be optimized for different pump orientations.

[0054] In an alternative embodiment, the use of a separate bearing housing on the pump allows for the use of a suitable barrier fluid control system that tracks and controls the qualities and characteristics of the barrier fluid in the bearing housing. For example, if equipped with the pump, the temperature and pressure of the barrier fluid can be controlled precisely using the barrier fluid control system thereby maximizing bearing life. In addition, the pressure of the barrier fluid can be controlled to supplement the back pressure on the seal to prevent seal failure at high suction pump inlet pressures. The temperature and pressure of the barrier fluid can be controlled automatically, for instance, by using a Proportional-Integral-Derivative (PID) controller. The barrier fluid control system can also be equipped with a site glass or automated method to determine and monitor the quality of the barrier fluid over time. Inside of the gear housing can be coated with suitable to prevent wear.

[0055] In an embodiment, the first shaft 40 and/or the second shaft 70 is attached to a motor (not shown) that rotates the corresponding gears 30 and 60. For example, the motor can be attached to a drive shaft 100 that rotates the shaft 40 along with the gear 30. The

motor 100 can be any suitable motor used to rotate the gears within the gear housing 20 thereby providing a force to move material through the passage 22 of the gear housing 20. This motor can be driven with a variable frequency drive to adjust pump speed. [0056] In alternative embodiments, the pump further comprises one more spring assemblies surrounding the shaft of the gear. For example, as shown in FIG. 5, the pump 10 can comprise a spring assembly 200 surrounding the first shaft and positioned between the first seal and the first bearing assembly, a spring assembly 202 surrounding the first shaft and positioned between the second seal and the second bearing assembly, a spring assembly 204 surrounding the second shaft and positioned between the third seal and the third bearing assembly, and a fourth spring assembly 206 surrounding the second shaft and positioned between the fourth seal and the fourth bearing assembly.

[0057] The spring assemblies can be used to form a tight seal between the bearing assemblies and the gear(s). For example, the spring assemblies located between the seal and the bearing assemblies can thrust each corresponding seal against or near the flank of the gear(s). This can prevent the seals from moving axially along the shafts. [0058] The spring assemblies can be attached to and held in place by the bearing assemblies. For instance, when assembled as shown in FIG. 5, the bearing assemblies 34, 38, 64 and 68 can be secured or prevented from shifting axially on the corresponding gear shafts 40 and 70 using fasteners or clips (e.g. attached to the bearing housing), which further prevents the attached spring assembly 200 pressing against the seals 50, 52, 80 and 82 from shifting axially.

[0059] A more detailed embodiment of the spring assembly 200 is illustrated in FIGS. 7- 8. As shown in FIGS. 7-8, in an embodiment, the spring assembly comprises a cage 210 that has a cross-section in the shape of a lying U. One side of the cage 210, which is the side closest to the bearings during operation, is closed. Radially arranged holes 212 in the upper and lower portions of the cage 210 serve to receive one or more pins 220. The pins 220 can be used in conjunction with the seal 150 shown in FIG. 6 to prevent the seal 150 from rotating during operation. For example, the recesses 152 of the seal 150 can receive the pins 220 of the spring assembly 200 thereby preventing the seal 150 from rotating as the gears 30 and 60 are rotated.

[0060] A spring washer 230 and a force transmission ring 240 can be located behind the pins 220, whereby the spring assembly 200 can thrust or force the seal 150 against the

flanks of the gears 30 and 60 in an axial direction. The spring washer 230 lies between the force transmission ring 240 and the closed end of the cage 210.

[0061] In yet another embodiment, the invention provides a method for pumping a material. The method comprises providing a pump comprising a gear housing defining a passage and having an inlet and an outlet and one or more gears contained within the gear housing. The gears comprise one or more bearing assemblies movably engaged with the gear. The bearings are separated from the passage of the gear housing by one or more seals. The method further comprises moving the material through the pump by rotating the gear. [0062] The bearing assembly can be contained within a bearing housing attached to the gear housing. The bearing housing defines an inlet and an outlet and a reservoir containing the bearing. In an embodiment, the method further comprises pumping a barrier fluid thorough the inlet of the bearing housing to control the temperature and/or the pressure within the bearing housing. The method can further comprise monitoring the barrier fluid using a barrier fluid control system.

[0063] In the specification, there have been disclosed typical preferred embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the claims. Obviously many modifications and variations of the invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.