AU2008101032A4 - Shaft Guard - Google Patents

Description

AUSTRALIA

ORIGINAL

COMPLETE SPECIFICATION INNOVATION PATENT Invention Title: Name of Applicant: Address for service: Shaft Guard Alcoa of Australia Limited

WRAYS

Ground Floor, 56 Ord Street West Perth WA 6005 Attorney code: WR The following statement is a full description of this invention, including the best method of performing it known to me:- -2oo 00 c Shaft Guard 0 Field of the Invention This invention relates to a guard for a rotatable shaft of a machine, and to a Cmachine incorporating such a guard.

0 5 The invention has been devised particularly, although not solely, as a guard for 00 the drive shaft of a rotodynamic machine such as a centrifugal pump.

Background Art The following discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.

A centrifugal pump is used for pumping fluids such as liquids and slurries.

Typically, a centrifugal pump comprises a pump body having a casing defining a pump chamber which accommodates an impeller mounted a pump shaft. The pump shaft extends from the pump body for connection to a rotatable drive mechanism such as a motor. A gland seal is provided between the pump body and the pump shaft. Typically, the gland seal comprises a stuffing box accommodating compression packing and a gland follower for compressing the packing within the stuffing box. It is necessary when excessive leakage occurs to adjust the gland follower to increase the extent of compression on the packing until the leakage is decreased to a tolerable minimum.

Typically, the adjustment to the gland follower needs to be made while the pump is operating. Accordingly, a person performing the adjustment needs to exercise caution to avoid contact with the rotating pump shaft while adjusting the gland follower.

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O It is against this background, and the problems and difficulties associated therewith, that the present invention has been developed.

0 N Disclosure of the Invention According to a first aspect of the invention there is provided a guard for a rotatable shaft of a machine having a body from which the shaft extends, the guard comprising a first portion adapted to be mounted on the machine and a 00 second portion adapted to be mounted on the first portion, the second portion 0 0 being configured to provide a barrier for location adjacent at least a section of the shaft to impede contact therewith.

Preferably, the second portion is configured as a sleeve adapted to extend about said section of the shaft.

Preferably, the sleeve is formed as a plurality of sleeve sections. Conveniently, the sleeve sections comprise two sections, typically an upper sleeve section and a lower sleeve section.

Preferably, the sleeve has an aperture to provide a drainage port through which fluid can drain from within the sleeve when the sleeve is disposed about said section of the shaft. With such an arrangement, the sleeve is so oriented in use that the aperture is disposed at the bottom of the sleeve.

Preferably, machine body incorporates a gland seal through which the rotatable shaft extends and the first portion is adapted to be mounted on the body in association with the gland seal. Typically, the gland seal includes a gland follower and the first portion comprises the gland follower.

Preferably the first portion comprises an inner section defining an opening through which the shaft is adapted to extend and an outer section defining a flange adapted to be bolted in position on the machine body, the inner section being configured for engagement with the sleeve.

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O Preferably, the inner section is configured to define a first engagement element for mating engagement with a second engagement element on the sleeve, O whereby the first and second engagement elements are adapted to cooperate to mount the sleeve on the inner section of the first portion.

N 5 Preferably, the first engagement element comprises an annular lip and the Ssecond engagement element comprises circumferential groove for receiving the lip.

00 SPreferably, the inner section further comprises a catchment area and a drainage hole, the arrangement being that fluid leakage past the gland seal is thrown outwardly by the rotating shaft and contained within the catchment area to subsequently drain therefrom through the drainage hole.

Preferably, the first portion is formed as a plurality of sections adapted to be fastened together. Conveniently, the sections comprise two sections, typically an upper section and a lower section.

According to a second aspect of the invention there is provided a guard for a rotatable shaft of a machine having a body from which the shaft extends through a gland seal, the guard comprising a portion configured as a gland follower for the gland seal and a sleeve adapted to extend from said portion to provide a barrier for location adjacent at least a section of the shaft to impede contact therewith.

According to a third aspect of the invention there is provided a fluid pump comprising a pump body, a rotatable pump shaft extending from the pump body through a gland seal, the gland seal including a gland follower, and a sleeve mounted on the gland follower to extend therefrom provide a guard about the shaft at a location adjacent the gland follower.

Typically, the pump includes a bearing assembly for supporting the pump shaft at a location spaced from the gland seal, the sleeve extending from the gland follower towards the bearing assembly and terminating adjacent thereto. With 00 this arrangement, the sleeve provides a guard for the section of the shaft between the gland follower and the bearing assembly or at least for most of that o section of the shaft. In this way, the guard serves to isolate the pump shaft from Ngland follower such that an operator is able to adjust the gland follower while the pump is running without concern about the need to avoid contact with the N rotating shaft.

0Brief Description of the Drawings oO 00 The invention will be better understood by reference to the following description of one specific embodiment thereof as shown in the accompanying drawings in which: Figure 1 is a schematic perspective view of a shaft guard according to the embodiment, the shaft guard comprising a first portion and a second portion; Figure 2 is a schematic plan view of the shaft guard, illustrating in particular a lower section of the first portion and a lower section of the second portion; Figure 3 is an exploded perspective view of a sleeve providing the second portion of the shaft guard, the sleeve comprising an upper sleeve section and a lower sleeve section; and Figure 4 is a schematic elevational view of the shaft guard according to the embodiment installed on a centrifugal pump.

Best Mode(s) for Carrying Out the Invention Referring to the drawings, there is shown a shaft guard 10 for a centrifugal pump 11 which is adapted to be driven by a drive mechanism such as a motor 13. The centrifugal pump 11 comprises a pump body 15 and a pump shaft 17 which extends from the pump body 15 for coupling to the motor 13. The pump body 00 -6- O comprises a pump casing 18 defining a pump chamber (not shown) which accommodates an impeller (also not shown) mounted on the inner end of the O pump shaft 17. A gland seal is provided between the pump body 15 and the pump shaft 17.

N 5 A bearing assembly 19 is provided to support the pump shaft 17 at a location Cadjacent the motor 13 and thus spaced from the pump body 15. With such an 0 arrangement, there is a section 17a of the pump shaft 17 exposed between the OO gland seal and the bearing assembly 19. The shaft guard 10 according to the Sembodiment is intended to provide a barrier against contact with the exposed shaft section 17a, as will be explained in more detail later.

The gland seal comprises a conventional stuffing box (not shown) and a gland follower 21. The stuffing box accommodates compression packing for establishing a seal about the rotating pump shaft 17 and the gland follower 21 is adapted to apply compression to the packing to establish a fluid seal about the rotating shaft, as is well known to persons skilled in the art.

The gland follower 21 is mounted on two studs 23 projecting from the pump body 11 (as shown in Figure 4) and is retained in position by nuts 25 threaded onto the studs 23. With this arrangement, the position of the gland follower 21 can be adjusted in known manner for the purposes of varying the compression of the packing by tightening or loosening the nuts 25 as necessary.

The gland follower 21 comprises an annular body 27 formed in two sections, being an upper section 28 and a lower section 29 adapted to be connected together by bolts 31. The annular body 27 comprises a radially outer section 31 which defines a flange 33 incorporating mounting holes 35 for accommodating the studs 23, as shown in Figure 4. The annular body 27 further comprises a radially inner section 37 defining a central opening 39 though which the pump shaft 17 can extend. The radially inner section 37 is configured to define an abutment 41 on one side thereof for contacting packing in the stuffing box of the gland seal to apply compression thereto. The radially inner section 37 further comprises a first engagement element 43 on the other side thereof, the first -7o00 0 engagement element 43 being configured as an annular lip 44. A catchment area 45 is defined within the inner section 37 between the abutment 41 and the O first engagement element 43, the arrangement being that fluid leakage past the gland seal is thrown outwardly by the rotating shaft 17 and contained within the catchment area 45. A drainage hole 47 is provided in the radially inner section 37 N at the bottom of the catchment area 45 to allow captured fluid to drain from the 0 gland follower.

00oo The shaft guard 10 according to the embodiment comprises the gland follower 21 as a first portion thereof and a sleeve 50 as a second portion thereof. The sleeve 50 is formed of a plastics material and is of annular cross-section. Further, the sleeve 50 is of two-part construction, comprising an upper sleeve section 51 and a separate lower sleeve section 52. Construction of the sleeve 50 in the two parts facilitates positioning of the sleeve about the shaft section 17a.

The sleeve 50 is dimensioned to be snugly received at one end 50a thereof within the central opening 39 of the radially inner section 37 of the gland follower 21. Adjacent that end 50a of the sleeve 50 there is provided a second engagement element 53 adapted to cooperate with the first engagement element 43 on the gland follower 21 to facilitate mounting of the sleeve 50 on the gland follower 21. The second engagement element 53 is configured as a circumferential groove 55 adapted to receive the annular lip 44 on the gland follower 21. With this arrangement, the sleeve 50 is captively retained within the gland follower 21, as shown in Figure 2.

The sleeve 50 incorporates a rib formation 57 which accommodates the groove and which presents an inner face 59 which can slidingly contact the rotating pump shaft 17 to present an impediment to migration of leakage fluid along the pump shaft. In this way the rib formation 57 presents a wiper seal in contact with the rotating pump shaft 17. The sleeve 50 is formed of a low-friction plastics material for this purpose.

The lower sleeve section 52 incorporates an aperture 61 to provide a drainage port through which fluid (including in particular any leakage fluid that may have 0-8- O by-passed the wiper seal) can drain from within the sleeve 50 when the sleeve is disposed about shaft section 17a. With such an arrangement, the sleeve 50 is so O oriented in use that the aperture 61 is lowermost, as shown in Figure 2. It is important that there be no fluid accumulation in the sleeve 50, as the bearing assembly 19 is nearby and any fluid ingress into the bearing assembly is likely to N be detrimental to the bearing.

OThe shaft guard 10 is installed by positioning the sleeve sections 51, 52 about 00 the pump shaft section 17a to assemble the sleeve, and then positioning the Ogland follower sections 28, 29 about assembled sleeve 50, with the lip 41 on the gland follower located in the groove 55 on the sleeve. The two gland follower sections 28, 29 are then fastened together by bolts 31 to secure the gland follower 21 in position on the sleeve 50. The gland follower 21 can then be installed in position on the pump body 15 to establish the gland seal around the pump shaft 17.

When installed, the shaft guard 10 extends from the gland follower 21 towards the bearing assembly 19 to terminate closely adjacent thereto, as shown in Figure 4. With this arrangement, the sleeve 50 provides a guard for the section 17a of the pump shaft 17 between the gland follower 21 and the bearing assembly 19 (or at least for most of that section of the shaft). In this way, the shaft guard 10 serves to isolate the pump shaft section 17a from gland follower 21 such that an operator is able to adjust the gland follower 21 by turning the nuts 25 on the studs 23 while the pump 11 is running without concern about the need to avoid contact with the rotating pump shaft.

In circumstances where the shaft guard 10 is to be retrofitted onto an existing pump, it is necessary to replaced the original gland follower on the pump with the gland follower 21 used as part of the shaft guard according to the embodiment.

From the foregoing, it is evident that the present embodiment provides a simple yet highly effective arrangement for providing a guard about a rotating shaft on a centrifugal pump which allows the gland follower of the pump to be adjusted 00 oo9 O while the pump is in operation without exposing the person performing the adjustment to potential harm from the rotating pump shaft.

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SIn the embodiment descripted, the shaft guard 10 is fitted about the section of the pump shaft 17 extending from the pump body 15 towards the motor 13. In c 5 certain other pumps, the pump shaft extends through the impreller and there are Stwo glands. With this arrangement, the pump can be fitted with two shaft guards.

00oo Modifications and improvements can be made without departing from the scope of the invention.

It should be appreciated that the scope of the invention is not limited to the scope of the embodiment described; for example, the invention need not necessarily be limited to centrifugal pumps and may have application to other rotodynamic machines having a rotatable input or output shafts.

Throughout the specification and claims, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Claims (4)

1. A guard for a rotatable shaft of a machine having a body from which the shaft c extends, the guard comprising a first portion adapted to be mounted on the machine and a second portion adapted to be mounted on the first portion, the second portion being configured to provide a barrier for location adjacent at least a section of the shaft to impede contact therewith. oo 00

2. A guard according to claim 1 wherein the second portion is configured as a c sleeve adapted to extend about said section of the shaft, the sleeve being formed as a plurality of sleeve sections.

3. A guard according to claim 1 or 2 wherein the sleeve has an aperture to provide a drainage port through which fluid can drain from within the sleeve when the sleeve is disposed about said section of the shaft.

4. A guard for a rotatable shaft of a machine having a body from which the shaft extends through a gland seal, the guard comprising a portion configured as a gland follower for the gland seal and a sleeve adapted to extend from said portion to provide a barrier for location adjacent at least a section of the shaft to impede contact therewith. A fluid pump comprising a pump body, a rotatable pump shaft extending from the pump body through a gland seal, the gland seal including a gland follower, and a sleeve mounted on the gland follower to extend therefrom provide a guard about the shaft at a location adjacent the gland follower.