Positive Displacement Pump Including Detectable Composite Non-Metallic Components

Abstract

A positive displacement pump is disclosed which includes a case that defines a pump cavity. A shaft and rotor, which are detachably connected together, are also included wherein the rotor is disposed within the pump cavity and the shaft passes through an opening in the proximal end of the case. The distal end of the shaft, in addition to being connected to the rotor, is also coupled to a fastener that couples a cover plate over the distal end of the shaft and over at least part of the base portion of the rotor. The opening in the proximal side of the case through which the shaft passes also accommodates a seal assembly. Access to the seal assembly is easily made by removing the head from the case and removing the rotor from the shaft. The seal assembly can be changed or serviced without removal of the shaft.

Description

TECHNICAL FIELD

This disclosure relates to pumps that may be cleaned and with seals that may be replaced without a complete disassembly of the pump. This disclosure also relates to pumps that include components made from composite materials that may be detected in the same manner in a product stream that metallic materials can be detected.

BACKGROUND

Positive displacement pumps are used in food processing, chemical, pharmaceutical and other industries. In many applications, the pump must be hygienic or sanitary, meaning that the pump must not contaminate the product. Further, the pump must be readily cleanable and therefore the pump must be easily disassembled so the part may be cleaned on the pump must be designed so it can be suitably cleaned with minimal or no disassembly.

Typically, sanitary pumps used in the food and chemical industries must be readily cleanable. Such sanitary pumps have been formed from stainless steel, because it is durable, substantially chemically inert and typically does not contaminate the product. However, in certain pump designs, use of stainless steel can result in rapid wear and/or galling of close-fitting, frictionally engaging parts. Not only does this wear and galling result in loss of efficiency, the operating life of the pump is shortened and the product is subject to contamination. In order to overcome these problems, such stainless steel pumps must be designed to prevent materials which might otherwise gall upon contact from engaging one another. Non-galling stainless steel have been used in the past but such designs are not entirely satisfactory because of the need for additional parts, multiple interfitting pieces and special casing and rotor designs which may substantially add to the cost of the pump.

Other problems associated with currently available sanitary pumps include seal replacement and cleaning. Specifically, sanitary internal gear pumps are typically designed with a one piece shaft/rotor. To clean the pump or replace the seal through which the shaft passes, the pump must be completely disassembled. That is, the shaft/rotor must be removed in order to gain access to the seal behind the rotor. One procedure to remove the seal disposed behind a unitary rotor/shaft and/or clean a sanitary pump behind the rotor requires numerous steps.

Specifically, because the shaft must be removed, any lock washers or lock nuts must be removed from the proximal (inboard) end of the shaft. Then, the bearing assembly that supports the proximal end of the shaft may need to be removed, which may be quite complicated, depending upon the bearing assembly design. Further, a seal assembly is typically disposed towards the distal end of the shaft near the case or pump cavity. Often, seal assemblies include flush or barrier fluid tubes which must be disconnected and then the seal assembly must be removed, which may also might be quite complicated, depending upon the particular design of the seal assembly. Then, from the distal side of the pump, the head and idler are removed and, because the bearing and seal assemblies have been removed, the rotor and shaft can be removed and the pump may be cleaned. Then, the entire process is reversed before the pump may be placed back into service.

Accordingly, there is a need for improved sanitary pumps that are both easier to clean, inspect and service, and that will not contaminate the product with metallic or plastic particles.

SUMMARY

In one aspect, a positive displacement pump is disclosed. The pump may include a case that may include a proximal end with an opening and an open distal end that is detachably covered by a head. The pump may also include a rotor that includes a base. The base of the rotor may include a proximal side, a distal side and an opening in the proximal side of the base. The pump may further include a shaft that may include a proximal end and a distal end that extends through the opening in the proximal end of the case before being coupled to the opening in the base of the rotor. The distal end of the shaft may be coupled to the base of the rotor by a fastener. The fastener may sealably couple a cover plate to the distal end of the shaft. The cover plate may extend radially outward from the shaft and sealably cover at least part of the distal side of the base of the rotor. The opening in the proximal end of the case may accommodate a seal assembly. The distal end of the shaft may pass through this seal assembly. The seal assembly may sealably engage the opening in the proximal end of the case, the shaft and the proximal side of the base of the rotor.

In another aspect, a positive displacement pump is disclosed. This pump may include a case having a proximal end with a through opening and an open distal end that is detachably covered by a head. The pump may also include a rotor that includes a base with a plurality of teeth extending distally from a periphery of the base. The base may also include a proximal side and a distal side connected to the teeth. The base may also include an opening in its proximal side for receiving a shaft. The shaft may include a proximal end supported by a bearing assembly and a distal end coupled to the opening in the proximal side of the rotor. The distal end of the shaft may also include an opening for receiving a fastener. The fastener may be used to couple a cover plate to the distal end of the shaft. The cover plate may extend radially outwards from the shaft and cover at least part of the distal side of the base of the rotor thereby coupling the rotor to the shaft. The pump may further include at least one seal disposed between the cover plate and the rotor and at least one seal disposed between the fastener and the cover plate. The distal end of the shaft passes through and is supported by a seal assembly before passing through the opening in the proximal end of the case. The opening in the proximal end of the case may also accommodate a seal assembly. The distal end of the shaft passes through the seal assembly before being coupled to the opening in the proximal side of the base of the rotor. The seal assembly may sealably engage the opening in the proximal end of the case, the shaft and the proximal side of the base of the rotor.

A method for replacing a seal assembly of a pump is also disclosed. The disclosed method may include removing a head, pin and idler from a distal end of a case of the pump. The head may be coupled to the pin and the idler and removal of the head, pin and idler may expose a fastener. The method may further include removing the fastener from a distal end of a shaft that is detachably coupled to a proximal end of a rotor and removing a cover plate that was trapped between the fastener and the distal end of the shaft. The rotor may then be removed thereby exposing the seal assembly disclosed in an opening in the proximal end of the case and through which the shaft passes. The method may then further include removing the seal assembly without removing the shaft.

In any one or more of the embodiments described above, a pin may be coupled to the head. The pin may be received in an idler. Further, the rotor may include a plurality of distally extending teeth disposed around a periphery of the base of the rotor. The idler may include a plurality of radially outwardly extending teeth, with each idler tooth rotatably disposed between two of the rotor for part of a revolution of the rotor and idler.

In any one or more of the embodiments described above, the case, rotor, idler and head may be fabricated from a metal-detectable polymer.

In any one or more of the embodiments described above, the case, rotor, idler, cover plate and head may be fabricated from a metal-detectable polymer.

In any one or more of the embodiments described above, the case, rotor, idler and head may be fabricated from a metal coated with a metal-detectable polymer.

In any one or more of the embodiments described above, the case, rotor, idler, cover plate and head may be fabricated from a metal coated with a metal-detectable polymer.

In any one or more of the embodiments described above, removal of the head, pin and idler from the case provides access to the fastener and removal of the fastener enables the cover plate and rotor to be pulled out of the head through the open distal end thereby providing access to the seal assembly without removal of the shaft.

In any one or more of the embodiments described above, a seal ring may be trapped between the cover plate and the rotor.

In any one or more of the embodiments described above, a seal ring may be trapped between the fastener and the cover plate.

In any one or more of the embodiments described above, the proximal end of the shaft may extend through a bearing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side plan view of a disclosed internal gear pump.

FIG. 2 is a sectional view taken from above and substantially along the line 2-2 of FIG. 1.

FIG. 3 is a right end view of the pump shown in FIGS. 1-2.

FIG. 4 is an enlarged partial sectional view of the area labeled 4 in FIG. 2.

FIG. 5 is a perspective view of another disclosed internal gear pump made in accordance with this disclosure.

FIG. 6 is a right side view of the pump shown in FIG. 5.

FIG. 7 is a sectional view taken substantially along line 7-7 of FIG. 6.

FIG. 8 is a right end view of the pump shown in FIGS. 5-7.

FIG. 9 is an enlarged partial sectional view of the head, idler, rotor, shaft, case, seal assembly and bearing of the pump shown in FIGS. 5-8.

FIG. 10 is an enlarged partial sectional view of the area labeled 10 in FIG. 7.

FIG. 11 is a partial enlarged sectional view of the area labeled 11 in FIG. 9.

FIG. 12 is yet another disclosed internal gear pump made in accordance with this disclosure.

FIG. 13 is a right side view of the pump shown in FIG. 12.

FIG. 14 is a sectional view taken substantially along line 14-14 of FIG. 13.

FIG. 15 is a right end view of the pump shown in FIGS. 12-14.

FIG. 16 is a partial sectional view taken substantially along line 16-16 of FIG. 15.

FIG. 17 is a partial enlarged section view of the area labeled 17 in FIG. 16.

DESCRIPTION

FIG. 1 is a side plan view of a pump 10 made in accordance with this disclosure. The pump 10 includes a shaft 11 that includes a proximal end 12 that is coupled to a motor or other power source (not shown). As shown in FIGS. 2 and 4, the shaft 11 also includes a distal end 13 that is coupled to a rotor 14. Returning to FIG. 1, the pump 10 also includes a bracket assembly 15 disposed between a bearing housing assembly 16 and a case 17. The case 17 includes two ports 18, 19 which may be inlet and outlet ports, depending upon the direction of rotation of the rotor 14 and shaft 11. The case 17, as shown in FIG. 2, provides a pump chamber and houses the rotor 14, an idler 21, an idler pin or shaft 22 and a seal assembly 23 which will be discussed in greater detail in connection with FIG. 4. The idler pin 22 may be secured to a head 24 in a number of different ways that would include material from getting between the idler pin 22 and the head 24. For example, soldering, secure press-fit and threaded connections with seals are but a few ways to secure the idler pin 22 to the head 24 in a sanitary manner. The head 24 covers the open distal end 25 of the case 17. The idler 21 may be rotatably secured to the idler pin 22 with the bead 50 and groove 54 as shown in FIG. 4. The case 17 also includes a proximal end 26 that includes an opening 27 (FIG. 4) through which the distal end 13 of the shaft 11 passes and which also accommodates the seal assembly 23. The open distal end 25 of the case 17 is enclosed by the head 24 which, as shown in FIGS. 1 and 3, can be secured to the case 17 via a plurality of conventional fasteners 28. While not shown in FIGS. 1-4, the fasteners 28 may also pass through the case 17 to secure the head 24 and case 17 to the bracket assembly 15. Also as shown in FIGS. 1 and 3, the pump 10 may include a stand 31.

Turning to FIG. 4, the distal end 13 of the shaft 11 may be splined and the opening 32 in the base 33 of the rotor 14 may also be splined to form a secure spline connection between the shaft 11 and rotor 14. Numerous other means for detachably connecting the rotor 14 to the shaft 11 are known as will be apparent to those skilled in the art and need not be listed here. The distal end 13 of the shaft 11 may also feature a threaded opening 34 for receiving a threaded fastener 35. The threaded fastener 35 may be used to secure the cover plate 36 to the distal end 13 of the shaft 11 as well as to part of the distal side 37 of the base 33 of the rotor 14 thereby securing the rotor 14 to the shaft 11. Leakage from the pump cavity 38 that passes the cover plate 36 to the distal end 13 of the shaft 11 may be prevented from further migration by the ring seal 41. Another ring seal 42 may also be provided to prevent leakage from migrating from the pump cavity 38 to the threaded opening 34 in the distal end of the shaft 11

Thus, the cover plate 36 includes an outer ring portion 43 and an inner ring portion 44. The outer ring portion 43 of the cover plate 36 and the recess 45 in the distal side 37 of the base 33 of the rotor 14 may prevent leakage from the pump cavity 38 towards the seal assembly 23 and vice versa. Similarly, the head 46 of the fastener 35 is disposed in the recess 47 formed in the cover plate 36. The seal 42 prevents migration of material from the pump cavity 38 towards the threaded opening 34 and vice versa.

The shaft 11 is supported by two sets of bearings including the proximal bearings 51 shown in FIG. 2 as well as the distal bearings 52 shown in FIGS. 2 and 4. The proximal bearings 51 are disposed within the bearing housing assembly 16 that may be connected to or formed integrally with the bracket assembly 15. The distal bearing 52 are disposed within the bracket assembly 15 and abut the plate 53 are disposed between the bracket assembly 15 and the proximal end 26 of the case 17.

The seal assembly 23 is multifunctional. Specifically, the seal assembly 23 includes a distal ring 55 which is encircled by a ring seal 56. The distal ring 55 and ring seal 56 provide a sealing engagement against the rotor 14. Then, to provide a seal between the case 17 and the rotor 14, a ring 57 is provided which includes a distally extending tab 58 that engages the distal ring 55. Another ring seal 59 is provided to prevent fluid migration from the rotor 14 into the seal assembly 23 and vice versa. A bracket 61 biases the ring 57 and ring seal 59 radially outward against the proximal ring 62. The ring seal 59 provides a sealing engagement between the ring 57 and the proximal ring 62. Further, the ring seal 63 provides a sealing engagement between the proximal ring 62 and the case 17.

Replacement of the seal assembly 23 is simplified by the design of the pump 10. Specifically, to remove the seal assembly 23 for replacement or repair, an operator merely needs to remove the head 24 before removing the fastener 35, which may also be referred to as the rotor retaining bolt. Then, the rotor 14 can be removed using available pulling tools, as will be apparent to those skilled in the art. The cover plate 36 is removed when the rotor 14 is removed. The seal assembly 23 may then be repaired or replaced and the area behind the rotor 14 may be cleaned/sanitized. The shaft 11 does not need to be removed for this standard maintenance procedure. The head 24 and casing 17 may be connected to the bracket 15 by the fasteners 28 so that the casing 17 may also be removed for cleaning/sanitizing and replaced. The new or repaired seal assembly 23 is then inserted and the rotor 14, presumably with the cover plate 36 already installed in the recess 45, is inserted back into the pump cavity 38, the rotor or retainer screw 35 is tightened, and the case 17 and head 24 are replaced. The reader will note that the idler 21 and idler pin 22 may be removed upon removal of the head 24 as the idler pin 22 may be press fit or soldered into the head 24.

Further, when used in food processing, pumps like the pump 10 disclosed herein must not contaminate the food. Hence, not only is the seal assembly 23 and its ease of servicing and replacement important, metal on metal contact of the working parts of the pump 10 may be problematic. Specifically, rotating metal parts, such as the rotor 14, idler 21 and shaft 11 make contact with other metal parts, whether stationary or not, such as the case 17 and head 24, metal particles can be liberated and may migrate into the food product, which is obviously not acceptable. To avoid this problem, in the past, manufacturers resorted to making plastic pumps or pumps made out of non-metallic materials. However, this can be problematic because non-metallic materials can also chip or fracture and detection of plastic particles in the food product is even more problematic. Specifically, metal particles may be detected using conventional detecting mechanisms and the malfunctioning pump may be taken out of service. In contrast, non-metallic particles cannot be so easily detected.

As a solution to this problem, various components of the pump 10 can be fabricated from metal-detectable composite materials as opposed to metallic components or non-metallic components. In one aspect, the case 17, rotor 14, idler 21 and head 24 may be fabricated from such metal-detectable composite materials. As another option, metal-detectable composite materials can be molded over metallic bases or, in effect, used as a metal-detectable coating for a metallic component. For example, many materials can be rendered detectable by conventional metal detectors through the incorporation of particles of a metallic alloy in the material. For example, stainless steel powder may be utilized with various polymeric materials such as acetal polyurethane, polytetrafluoroethylene and other materials to make metal-detectable composite materials, as will be apparent to those skilled in the art.

Two additional embodiments are disclosed in FIGS. 5-11 and 12-18. Turning to FIG. 5, a perspective view of another disclosed pump 110 is shown with the ports 118, 119 being disposed at about a right angle with respect to the ports 18, 19 of the pump 10 as shown in FIG. 1. Like or similar parts of the pump 110 that are included and described in connection with the pump 10 will be numbered the same as those for the pump 10, except for use of a prefix “1”. Thus, the pump 110 also includes a head 124, a plurality of fasteners 128, a stand 131, a drive shaft 111, and the bearing housing assembly 116. The shaft 111 also includes a proximal end 112. A bracket assembly 115 connects the bearing housing assembly 116 to a case 117 that includes a proximal end 126. These features are also illustrated in the side view of FIG. 6.

Turning to FIG. 7, the proximal end 112 of the drive shaft 111 may include a slot 120 for receiving a key that is used to couple the shaft 111 to a motor (not shown). The shaft 111 may pass through a proximal bearing assembly 151 and a bushing 129 before it passes through a distal bearing assembly 152. The shaft 111 may also pass through an annular plate 153 before passing through the seal assembly 123. The seal assembly 123 may be coupled to the case 117 by a fastener 130 which is also shown in FIGS. 9 and 11. FIG. 9 also illustrates the use of one or more fasteners 128 to secure the head 124 not only to the case 117 but also to the bracket 115. To secure the rotor 114 to the shaft 111, a fastener 135 and cover plate 136 may be employed as illustrated above in connection with the embodiment illustrated in FIGS. 1-4. Ring seals 141, 142 may be employed to prevent the migration of material between the rotor 114 and the shaft 111 and between the shaft 111 and the fastener 135.

FIG. 10 illustrates the use of an idler pin 122 which passes through the idler 121 and which may include a distal end 137 that is received in a recess 139 in the head 124. A ring seal 140 may be employed to prevent the migration of material up into the recess 139. The idler pin 122 also passes through a bushing 148 about which the idler 121 rotates. The idler pin 122 is secured to the case 124 by the fastener 149 so that removal of the head 124 in case 117 also results in removal of the idler pin 149, idler pin 122, bushing 148 and idler 121. The rotor 114 is removed by removing the fastener 135 and cover plate 136 in a manner equivalent to that described above for the pump 10 and therefore will not be repeated here. The use of a fastener 149 and ring seal 140 to secure the idler pin 122 to the head 124 may be contrasted with the arrangement shown in FIG. 4 for the pump 10 where the idler pin 22 is not secured to the head 24 but, instead, is secured to the idler 21 with a bead 50 that is accommodated in a recess 54 in the idler 21 (see also FIG. 2).

Turning to FIGS. 12-18, yet another pump 210 is disclosed that includes many parts equivalent or the same as those describe above in connection with the pumps 10, 110. Such equivalent or identical parts will include the same reference numerals used above for the pump 10 but proceeded by the prefix “2”. Turning to FIGS. 12-13, the pump 210 also includes a shaft 211, a bearing housing assembly 216, a bracket assembly 215, a case 217, and fasteners 228 that are of the wing-nut variety. The ports 219, 218 are in the same orientation as that for the pump 10. A stand 231 is also provided.

Turning to FIG. 14, the shaft 211 includes a proximal end 212 with a slot 220 for coupling the shaft 211 to a motor (not shown). The shaft 211 passes through a proximal bearing assembly 251 before passing through the bracket assembly 215 and bushing 229. The shaft 211 then passes through the distal bearing assembly 252 before passing through the annular plate 253. A seal assembly 223 is provided for the hygienic/sanitary purposes and/or prevention of leakage purposes described above. The rotor 214 is secured to the shaft 211 by way of a cover plate 236 and a fastener 235 in a manner at least substantially similar to that of the pumps 10, 110 described above and therefore a description of this connection will not be repeated here.

Turning to FIGS. 15-18, it can be seen from FIG. 16, which is a sectional view of FIG. 15, that the bearing assembly 223 is secured in place with a fastener 230 similar to the fastener 130 shown in FIG. 11 for the pump 110. In contrast to the pump 110, the idler 221 is not secured to the head 224 but, instead, the idler 221 simply rotates with the rotor 214 as the pump operates. FIG. 17 further illustrates the use of the fastener 230 to connect the seal assembly 223 to the case 217.

INDUSTRIAL APPLICABILITY

Thus, an internal gear pump with separate shaft and rotor elements are disclosed. The spline connection (or other suitable detachable connection) between the shaft and the rotor greatly facilitates the removal of the rotor and provides easy access to the seal assembly for replacement of the seal assembly and cleaning/sanitizing behind the rotor. It also allows for individual replacement of either the rotor or the shaft, whereas traditional rotor/shaft assemblies require replacement of both parts, even if only one is worn. The disclosed pump also secures the rotor to the shaft using a conventional fastener, such as a retaining bolt. The use of both a spline connection and a fastener may provide for a longer operating life.

Further, because a portion of the seal assembly is received within a recess within the rotor, upon replacement of the seal assembly, the relationship between the seal assembly and the rotor accurately repositions the rotor element thereby eliminating the need to reset the pump end clearance after servicing. Such an internal gear pump that does not require resetting the end clearance after replacement of the seal assembly or cleaning behind the rotor helps to maintain peak pump operating efficiency and reduces maintenance down time. Resetting the end clearance of the currently available pumps requires skill and time. If the end clearance on a pump is not set correctly, the pump can be damaged or become less efficient. The disclosed pump eliminates the need for resetting the end clearance after cleaning, thereby saving time and reducing operating costs.

The disclosed concepts are not limited to hygienic a sanitary internal gear pumps. The disclosed concepts are applicable to many industries where internal gear pumps are employed. Further, the seal assembly shown in FIGS. 2 and 4 is known as a cartridge seal. The ease of removal and replacement of the seal assembly is not limited to cartridge seals, but is also applicable to packing, lip, mechanical, double mechanical, dynamic single and double o-ring, and magnetic drive seal systems. While the pump disclosed in the figures is an internal gear pump, the disclosed concepts are also applicable to external gear pumps, crescent internal gear pumps, lobe pumps and circumferential piston pumps. Further, in addition to a spline connection between the shaft and rotor, a slot and key connection may be utilized as well. Numerous other methods for coupling a shaft to a rotor are known to those skilled in the art.

Claims

1. A positive displacement pump comprising:

a case including a proximal end with an opening and an open distal end that is detachably covered by a head;

a rotor including a base, the base including a proximal side, a distal side and an opening;

a shaft including a proximal end and a distal end that extends through the opening in the proximal end of the case before being coupled to the opening in the base of the rotor, the distal end of the shaft being coupled to the base of the rotor by a fastener, the fastener sealably coupling a cover plate to the distal end of the shaft, the cover plate extending radially outward from the shaft and sealably covering at least part of distal side of the base of the rotor;

the opening in the proximal end of the case accommodating a seal assembly, the distal end of the shaft passing through the seal assembly, the seal assembly sealably engaging the opening in the proximal end of the case, the shaft and the proximal side of the base of the rotor.

2. The pump of claim 1 further including a pin coupled to the head, the pin being received in an idler, the rotor including a plurality of distally extending teeth disposed around a periphery of the base of the rotor, the idler being rotatably disposed within the teeth of the rotor.

3. The pump of claim 1 wherein at least one of the case, rotor and head are fabricated from a metal-detectable polymer.

4. The pump of claim 2 wherein at least one of the case, rotor, idler, cover plate and head are fabricated from a metal-detectable polymer.

5. The pump of claim 1 wherein at least one of the case, rotor and head are fabricated from a metal coated with a metal-detectable polymer.

6. The pump of claim 2 wherein at least one of the case, rotor, idler, cover plate and head are fabricated from a metal coated with a metal-detectable polymer.

7. The pump of claim 2 wherein each of the case, rotor, idler, cover plate and head are fabricated from metal.

8. The pump of claim 2 wherein removal of the head, pin and idler from the case provides access to the fastener,

removal of the fastener enables the cover plate and rotor to be pulled out of the head through the open distal end thereby providing access to the seal assembly without removal of the shaft; and

removal of the rotor enables the case to be removed from a bracket that supports the case.

9. The pump of claim 1 wherein a seal ring is trapped between the cover plate and the rotor.

10. The pump of claim 1 wherein a seal ring is trapped between the fastener and the cover plate.

11. The pump of claim 1 wherein the proximal end of the shaft extends through a bearing.

12. A positive displacement pump comprising:

a case having a proximal end with a through opening and an open distal end that is detachably covered by a head;

a rotor including a base with a plurality of teeth extending distally from a periphery of the base, the base including a proximal side and a distal side connected to the teeth and an opening for receiving a shaft;

the shaft including a proximal end supported by a bearing assembly and a distal end coupled to the opening in the rotor, the distal end of the shaft including an opening for receiving a fastener, the fastener coupling a cover plate to the distal end of the shaft, the cover plate extending radially outwards from the shaft and covering at least part of the distal side of the base of the rotor;

at least one seal being disposed between the cover plate and the rotor;

at least one seal being disposed between the fastener and the cover plate;

the distal end of the shaft passing through and being supported by a bearing assembly before passing through the opening in the proximal end of the case;

the opening in the proximal end of the case accommodating a seal assembly, the distal end of the shaft passing through the seal assembly before being coupled to the opening on the base of the rotor, the seal assembly sealably engaging the opening in the proximal end of the case, the shaft and the proximal side of the base of the rotor.

13. The pump of claim 12 further including a pin coupled to the head, the pin being received in an idler, the idler being rotatably disposed within the teeth of the rotor.

14. The pump of claim 12 wherein at least one of the case, rotor and head are fabricated from a metal-detectable polymer.

15. The pump of claim 13 wherein at least one of the case, rotor, idler, cover plate and head are fabricated from a metal-detectable polymer.

16. The pump of claim 12 wherein at least one of the case, rotor and head are fabricated from a metal coated with a metal-detectable polymer.

17. The pump of claim 13 wherein at least one of the case, rotor, idler, cover plate and head are fabricated from a metal coated with a metal-detectable polymer.

18. The pump of claim 13 wherein the case, rotor, idler, cover plate and head are fabricated from metal.

19. The pump of claim 13 wherein removal of the head, pin and idler from the case provides access to the threaded fastener, removal of the threaded fastener enables the cover plate and rotor to be drawn out of the head through the open distal end thereby providing access to the seal assembly without removal of the shaft.

20. A method for replacing a seal assembly of a sanitary/hygienic pump, the method comprising:

removing a head, pin and idler from a distal end of a case of the pump, the head being coupled to the pin and idler, removal of the head, pin and idler exposing a fastener;

removing the fastener from a distal end of a shaft that is detachably coupled to a proximal end of a rotor and removing a cover plate that was trapped between the fastener and the distal end of the shaft;

removing the rotor thereby exposing the seal assembly disposed in an opening in the proximal end of the case and through which the shaft passes;

removing the seal assembly without removing the shaft;

removing the casing from the bracket; and reassembling the casing, seal assembly, rotor, seal plate, fastener, idler and head without adjusting a rotor end clearance.