GB2142990A

GB2142990A - A lower bearing for a screw pump

Info

Publication number: GB2142990A
Application number: GB08412705A
Authority: GB
Inventors: Willem Veenstra
Original assignee: LANDUSTRIE MASCHF
Current assignee: LANDUSTRIE MASCHF
Priority date: 1983-06-24
Filing date: 1984-05-18
Publication date: 1985-01-30
Also published as: GB8412705D0; DE3419038A1; NL186593B; NL186593C; NL8302255A; GB2142990B

Abstract

The invention concerns a lower bearing for a screw pump, and comprises a slidebearing 3 arranged in a bearing housing 9 and allowing longitudinal displacement of a stub axle 2 which is aligned with the screw pump body axis and is supported by said housing 9. Either said bearing housing or said stub axle is connected to a fixed support 10, a ball joint being arranged inside the bearing housing between the slide bearing and said bearing housing, said joint consisting of two rings 5, 8 having mutually contacting spherical surfaces 6, 7 with substantially the same radius of curvature, the inner ring 5 being connected to said slide bearing 3 and the outer one 8 to said bearing housing 9. <IMAGE>

Description

SPECIFICATION A lower bearing for a screw pump For raising large quantities of water, in many cases, so-called screw pumps are used, which comprise a pump body provided with screw turns in the form of one or more radially extending helical ridges, said body lying in an inclined conveying gutter, the outer edges of said ridges being arranged at a distance from the gutter wall which is as small as possible, so that, when the screw pump body is rotated, water can be conveyed upwards between two adjacent screw turns and the gutter, the leakage between the extremities of the helical ridges and the gutter being negligible in respect of the conveyed quantity.

In practice screw pumps have great advantages, one of the most important advantage of which being their insensivity to coarse contaminations and their operational capacities, so that pumps of this type are very suitable for pumping waste and drainage water.

The screw body is supported at both extremities.

At its upper side where the drive means are situated, an upper bearing is provided adapted to carry the full longitudinal load of said body, as well as a part of the transversal load, said upper bearing generally being constructed as a self-adjusting bearing. The lower bearing which is situated under water at the opposite extremity has to support the remainder of the transverse load, and is constructed as a slide bearing adapted to take up length variations caused by temperature fluctuations.

The lower bearing comprises a bearing housing surrounding the slide bearing, a stub axle supported thereby and aligned with the screw body, a supply for pressurised lubricating grease, and a resilient seal between the bearing housing and the butt axle or the screw body, the grease lubricating the bearing and sealings and, moreover, contributing to the sealing.

If the lower bearing is rigidly mounted, it has to be aligned very accurately. Furthermore the screw body, when rotating, will be exposed to the same temperature around its circumference, but, when at rest, temperature differences between different sides may arise, and said body will become slightly warped as a consequence thereof. When starting the pump, the screw body will start to slightly oscillate, and the lower bearing will be heavily loaded thereby.

In order to remove this load, the lower bearing can be supported on a horizontal pivot allowing a vertical swinging movement of the screw shaft, said pivot itself sometimes being supported on another pivot which is transversely directed thereto so as to also allow a horizontal swinging movement.

Although, in this manner, the influence of slight oscillation of the screw body on the slide bearing can be eliminated, this construction has the draw-back that the pivot points are exposed to the generally polluted water; mounting said pivot or pivots in a completely sealed manner is, however, complicated and expensive.

The invention provides an improvement of a lower slide bearing for a screw pump of the abovementioned type, which slide bearing is provided with hinge means allowing some swinging move ment in respect of the fixed support, in which either the stub axle or the bearing housing is connected to said support, a ball joint being arranged between said slide bearing and the bearing housing, said joint consisting of two rings having mutually contacting spherical surfaces with substantially the same radius of curvature, the inner ring being connected to the slide bearing, and the outer one to the bearing housing.

The advantage of these features is that the ball joint surfaces are completely situated within the bearing housing so that said surfaces are shielded from the surrounding water without requiring additional sealing means. The allowed movements are very small and can be taken up by the resilient seals which are, for the rest, unloaded.

In particularthe resilient seal comprises a ring arranged in a groove in the bearing housing or the stub axle, there being a sealing contact between the lateral parts of said ring and the groove walls and between the end face and the other part, said ring being slideable in said groove transversely to the longitudinal axis of the bearing. In this manner greater angular deviations can be dealt with, which, for instance, will occur in the case of sinking of the lower bearing support.

More particularly a resilient seal is provided between the bearing sleeve of the slide bearing and the stub axle, said groove being provided in the vicinity of this seal, the end face of said ring bearing on a surface of the bearing sleeve.

The invention will be elucidated by reference to the accompanying drawings, wherein: Figures 1 and 2 show cross-sections of two substantially equal embodiments of a lower bearing according to the invention; and Figures 3 and 4 illustrate partial sections of a slightly modifieal embodiment of the bearings of Figures 1 and 2 resp.

In the embodiment of Figure 1, at one extremity of a screw body 1 which is only schematically indicated, a stub axle 2 is mounted coaxially thereto, which is rotatably and slideably supported in a slide bearing 3 provided with a bronze bearing sleeve 4.

The slide bearing 3 is enclosed in an inner ball joint ring 5 with a spherical surface 6, the latter contacting a corresponding surface 7 of an outer ball joint ring 8. The latter is fixed in a bearing housing 9 mounted on a fixed support 10.

A duct 11 opens into the bearing housing 9, by means of which pressurised grease can be led towards the interior of said housing 9. Between this housing 9 and the extremity of the screw body 1 or an adjacent part of the stub axle 2, elastic sealing rings 12 are provided.

The ball joint 7 - 9 allows a certain oscillating or tilting movement of the screw body 1. This movement is relatively small, and can be taken up completely by the elastic sealing rings 12 without disturbing the sealing effect thereof.

The grease lubricates the slide bearing 3 and the sealing rings, and, moreover, a weak grease flow is driven outwards, and although the sealing rings will allow said outward flow, they are, on the other hand, pressed sealingly against the stub axle 2 by the external water pressure. These sealing rings are, thus, completely enclosed so that damaging them by sharp components of the water is not possible, as these rings are separated from the water by a rather narrow slot through which the grease can escape.

The embodiment of Figure 2 mainly corresponds to that of Figure 1. The only difference is that, in this case, the stub axle 2' is fixedly mounted, and the bearing housing 9' is rotatable with the screw body 1. The grease duct 11 then opens into a longitudinal bore 13 in the stub axle 2' which, on the other hand, opens into the inner space of the bearing housing 9'.

Figures 3 and 4 show a modified construction of such a bearing which can be used in the embodiments of Figures 1 and 2 resp., and which allows a larger deviation from the axial direction. This may be required if larger subsidences of the foundation of the fixed support 10 should be taken into account.

Therein the slide bearing sleeve 4 is extended by an annular part 14, between which part 14 and the stub axle 2 or 2' resp. the elastic sealing ring 12 is provided. In the portion of the bearing housing 9 or 9' resp. situated near this extension 14, a groove 15 extending transversely to the axis of the bearing is provided, in which groove a ring 16 is arranged which is slideable in this groove. The lateral surfaces of the ring 16 bear sealingly on the lateral walls of the groove 15 through the intermediary of static sealing rings 17 arranged in recesses of said ring, and the end face thereof bears on the outer surface of the extension 14 by means of one or more static sealing rings 18. Since the ring 16 can slide in the groove 15 over a relatively large distance, a corresponding displacement of the ball joint is possible.

It is, as such, possible to have the ring 16 directly bearing, through its sealing ring 18, on the stub axle 2 or 2', but in such case the ring 16 should be secured against rotation, and the sealing ring 18 is then to be constructed in the manner of the rings 12 so that a rotational movement is possible, and grease can leak away therealong. The ring 16 can also be provided in a groove in the stub axle 2 or 2' or in the part 14.

Claims

1. A lower bearing for a screw pump, comprising a slide bearing arranged in a bearing housing allowing a certain longitudinal displacement of a stub axle which is aligned with the screw pump body axis and is supported by said housing, the latter being provided with a supply for pressurised lubricating grease, a resilient seal being provided between said bearing housing and said stub axle, either said bearing housing or said stub axle being connected to the fixed support, hinge means being provided which allow a certain swinging movement in respect of said support, whilst a ball joint is arranged inside the bearing housing between the slide bearing and said bearing housing, said joint consisting of two rings having mutually contacting spherical surfaces with substantially the same radius of curvature, the inner ring being connected to said slide bearing, and the outer one to said bearing housing.

2. The lower bearing as claimed in Claim 1, wherein the resilient seal comprises a ring arranged in a groove in either the bearing housing or the stub axle, the lateral parts thereof being, by means of sealing rings, in sealing contact with the groove walls, and the end face thereof being, by means of at least one sealing ring, in sealing contact with the other part, said ring being slideable in said groove transversely to the longitudinal axis of the bearing.

3. The lower bearing as ciaimed in Claim 2, an elastic seal being provided between the bearing sleeve of the slide bearing and the stub axle, the said groove being formed in the vicinity of said seal in the bearing housing, and the end face of said ring bearing on the outer surface of the bearing sleeve.

4. A lower bearing for a screw pump substantially as herein described with reference to the accompanying drawings.