GB2234321A

GB2234321A - Mounting pump rotor on drive shaft

Info

Publication number: GB2234321A
Application number: GB8915311A
Authority: GB
Inventors: Brian William Hubbard; John William Blaxill; David Farrer
Original assignee: ITT Industries Ltd
Current assignee: ITT Industries Ltd
Priority date: 1989-07-04
Filing date: 1989-07-04
Publication date: 1991-01-30
Also published as: GB8915311D0; WO1991000429A1

Abstract

A pump rotor (3) is splined onto a drive shaft (5) and runs in a sealed pump casing (1). An extension (4) of the rotor is screwed into a retainer (8) which is normally free to rotate around the shaft to pull the rotor onto the shaft. Axial movement of the retainer along the shaft is prevented by pins (12) fitting into annular groove (11) in the shaft. The retainer may be split with one of the pins formed as a screw which can be used to tighten the retainer and cause it to grip the shaft. Sealing between the rotor and the casing is achieved firstly by a sealing assembly (15, 16) and secondly by a ring (19).

Description

PUMPS This invention relates to pumps and in particular to pumps for pumping food and similar fluids where strict standards of hygiene have to be observed.

According to one aspect of the invention, there is provided a pump comprising a casing, a drive shaft, a rotor which can be slid onto the shaft for rotation thereby within the casing, an extension of the rotor terminating outside the casing, and retaining means outside the casing engaging the rotor extension to secure the rotor to the shaft, characterised in that the retaining means is rotatably attached to the shaft and engages the rotor extension with a screw thread so that rotation of the retaining means relative to the shaft results in axial sliding movement of the rotor along the shaft into or out of the casing.

According to a further aspect of the invention there is provideda pump comprising a casing, a pair of parallel drive shafts, a pair of intermeshing rotors which can be slid onto respective shafts for rotation thereby within the casing, extensions of the respective rotors terminating outside the casing, and separate retaining means outside the casing engaging the respective rotor extensions to secure each rotor to its respective shaft, characterised in that each retaining means is rotatably attached to a respective shaft, and engages the respective rotor extension with a screw thread so that rotation of the retaining means relative to the shaft results in axial sliding movement of the rotor along the shaft into or out of the casing.

Two embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a diagrammatic sectional elevation of part of a pump in accordance with a first embodiment, Figure 2 is a diagrammatic sectional end elevation on the line II-II of Figure 1, and Figure 3 is a view, similar to Figure 1, of a pump in accordance with a second embodiment.

Figure 4 is a diagrammatic sectional view similar to Figure 2 showing an alternative locking configuration.

Referring to Figure 1, the pump comprises a casing 1 onto which is bolted an end cover 2. Within the casing is a pump rotor 3 which is provided with an integral cylindrical extension 4. The rotor and its extension are mounted on a drive shaft 5 and have an internal cylindrical blind bore provided with splines engaging external splines 6 on the drive shaft so that when the latter is rotated by a motor (not shown), the rotor is rotated within the casing to perform a pumping operation.

Behind the casing is an open space 7 in which is a circular retainer 8 in the form of a collar.

This retainer has at its left hand end (as seen in Figure 1) an internal screw thread 9 mating with an external screw thread on the rotor extension 4.

At its right hand end, the retainer 8 is provided with one or more tangential holes 10 corresponding to an external annular groove 11 in the drive shaft 5.

As seen in Figure 2, two pins 12 are inserted in holes 10 and extend tangentially to the annular groove 11. They thus prevent the retainer 8 from moving axially relative to the drive shaft although they do not, at this stage, prevent rotation of the retainer on the shaft. Two pins are desirable but not essential.

In assembling the pump, prior to bolting the end cover 2 to the casing 1, the right hand end of the rotor extension 4 (Figure 1) is pushed over the left hand end of the drive shaft 5, with the splines interengaging, until the external thread 9 on the extension meets the end of the internal thread on the retainer 8. The collar is then rotated to engage the threads and thereby to move the extension 4 axially to the right until the lefthand end of the blind bore in the rotor abuts against the lefthand end of the drive shaft.

The foregoing process can be reversed when it becomes necessary to dismantle the pump, rotation of the retainer in the opposite direction resulting in positive axial movement of the rotor out of the housing, thus overcoming any resistance due to accumulated deposits in the pump.

It is to be noted that, even when the rotor is removed from the casing the retainer remains in position on the drive shaft.

In the case of a unidirectional pump it may be sufficient for the retainer 8 to remain free to rotate relative to the drive shaft, the direction of rotation of the latter being, of course, such as to enhance the threaded engagement between the rotor extension and the retainer. However, in accordance with a preferred feature of the invention, the collar is split as shown at 18 (Figure 2) and at least the lower pin 12 is formed as a bolt engaging in a threaded portion of the hole 10 on one side of the split. Tightening of the bolt in the hole turns the retainer into a clamp around the drive shaft and prevents the latter from unscrewing relative to the rotor extension.

Alternatively as can be seen in Figure 4 the retainer may be prevented from unscrewing relative to the rotor extension by using grub screws (27) tightening onto the pins (12) as shown in Figure 4.

Sealing between the rotor 3 and the casing 1 is effected by the means now to be described.

The face of the rotor remote from the end cover 2 is provided with a cylindrical recess 14 (Figure 1) surrounding the lefthand end of the extension 4. In this recess is a ring 15 of rigid, for example, ceramic, material constituting a front sealing member. Interposed between the ring 15 and the interior of the recess 14 is a sealing ring 16 of resilient material, for example, rubber, whose resilience retains the rigid ring 15 within the recess so that it rotates with the rotor 3.

Interfacing with the front sealing member 15 is a rigid, generally cylindrical, rear sealing member 17 of, for example, ceramic material slide into the casing 1 from the left and provided with an 0 ring 19 which seals the rear sealing member to the casing. The sealing member 17 is urged into sealing contact with the ring 15 by a spacer 13 which in the assembled condition abuts the left hand end of the retainer 8. The spacer is preferably resilient and may comprise a spring loaded cartridge.

It will be appreciated that, for cleaning purposes, the rotor can be withdrawn, once the end cover 2 has been removed, and the rings 14 and 15 taken out of the recess in the rotor. Furthermore, the rear sealing member 17 can be withdrawn to the left. The end cover 2, the pump casing 1 and the bearing housing 20 are normally held tightly together by bolts 21.

It will be noted that the sealing arrangements described do not seal against the sleeve and that they are readily accessible for cleaning.

Additional sealing can be provided by the construction shown in Figure 3 wherein the spacer 13 is provided with an extension 22, the rest of the pump being identical to that shown in Figure 1.

Interfacing with extension 22 is a rigid ring 23 of, for example, ceramic material housed in a cylindrical recess 24 in the retainer 8 and sealed thereto.

Although described in relation to a pump having a single rotor in the casing, the invention is equally applicable to pumps of the kind having a pair of parallel drive shafts carrying respective interlocking rotors rotating in opposite directions in the same casing, e.g. a pump of the lobe rotor type.

Claims

CLAIMS:

1. A pump comprising a casing, a drive shaft, a rotor which can be slid onto the shaft for rotation thereby within the casing, an extension of the rotor terminating outside the casing, and retaining means outside the casing engaging the rotor extension to secure the rotor to the shaft, characterised in that the retaining means (8) is rotatably attached to the shaft (5) and engages the rotor extension (4) with a screw thread (9) so that rotation of the retaining means relative to the shaft results in axial sliding movement of the rotor (3) along the shaft into or out of the casing (1).

2. A pump comprising a casing, a pair of parallel drive shafts, a pair of intermeshing rotors which can be slid onto respective shafts for rotation thereby within the casing, extensions of the respective rotors terminating outside the casing, and separate retaining means outside the casing engaging the respective rotor extensions to secure each rotor to its respective shaft, characterised in that each retaining means (8) is rotatably attached to a respective shaft (5), and engages the respective rotor extension (4) with a screw thread (9) so that rotation of the retaining means relative to the shaft results in axial sliding movement of the rotor (3) along the shaft into or out of the casing (1).

3. A pump as claimed in claim 1 or 2 characterised in that the retaining means comprises a retainer (8) in the form of a collar having, at one end, an internal screw thread (9) to engage an external screw thread on the rotor extension (4) and, at the other end, one or more tangential holes, (10), the shaft (5) having a corresponding external groove (11) and the retainer being provided with one or more tangentially-extending pins (12) which fit into groove (11) to prevent axial movement of the retainer in relation to the shaft.

4. A pump as claimed in claim 3 characterised in that the retainer (8) is split and that at least one of the pins (12) traverses the split and is at least partially in the form of a bolt which can be tightened to close the split and prevent rotational movement of the retainer in relation to the shaft.

5. A pump as claimed in claim 3 where the pins (12) may be locked with grub screws (27) to prevent rotational movement of the retainer in relation to the shaft.

6. A pump as claimed in claim 3, 4 or 5, characterised in that the rotor (3) is provided with a cylindrical recess (14) surrounding one end of the extension (4) and that the rotor and its extension are sealed relative to the casing (1) by a rigid annular first sealing member (15) disposed in the recess and an annular resilient sealing element (16) interposed between the sealing member (15) and the rotor 3 and an annular rigid second sealing member (17) disposed within the housing (1), surrounding the extension (4) and abutting against the first sealing member (15) the second sealing member (17) being axially withdrawable from the casing (1) on the same side thereof to the rotor (3) and sealed to the casing by an 0 ring (19).

7. A pump as claimed in claim 6, characterised in that the second sealing member (17) is held in contact with the first sealing member (15) by a spacer (13) which abuts the retainer (8).

8. A pump as claimed in claim 7, characterised in that the spacer (13) is resilient and urges the second sealing member (17) in the axial direction into abutment with the first sealing member (15).

9. A pump as claimed in claim 8, characterised in that the spacer (13) is a spring loaded cartridge.

10. A pump as claimed in any one of claims 7 to 9, characterised in that the spacer (13) has an annular extension (22) and abuts a sealing member (23) which is sealed to the retainer by an O ring (25) and rotates with the retainer.