WO1982003428A1

WO1982003428A1 - A screw pump

Info

Publication number: WO1982003428A1
Application number: PCT/SE1982/000082
Authority: WO
Inventors: Ab Gustav Terling
Original assignee: Bjoernberg Nils
Priority date: 1981-03-24
Filing date: 1982-03-22
Publication date: 1982-10-14
Also published as: EP0086781A1; SE8101863L; SE426975B

Abstract

A screw pump comprising a driving screw (12) and a toothed, rotatable sealing disc (15) meshing therewith, the teeth (20) of the disc meshing with recesses formed between the threads (22) of the screw and seal against these, the teeth (20) of the sealing disc (15) having substantially parallel side edges (22) and triangular gaps (19) between the teeth. The purpose of the present invention is to provide a screw pump, which has a high pump effect, which exerts the sealing disc (15) to a substantially less wearing, which effectively can keep the pump screw clean from adhering substances, which can be manufactured by casting and thus obtains a low weight simultaneously as it is simple from a constructional point of view and thus can be easily disassembled for cleaning, service and repair. These tasks have been solved by the features that the flanges, which form the thread (21) of the screw have a substantially constant or, in the direction towards the top of the flange, tapering thickness with the exception of the threaded part of the screw (12) situated in front of the central part of the sealing disc (15), which threaded part is partially formed as a bead or a ridge, and that the bead or the ridge (18) has a measure in the rotational direction of the screw which substantially corresponds to the shifting distance of the screw (12) in moving the sealing disc (15) from a position at which one tooth seals to a position at which a second, next following tooth seals.

Description

A screw pump

The present invention relates to a screw pump comprising a driving screw and a toothed, rotatable sealing disc meshing therewith, the teeth of the disc meshing with recesses formed between the threads of the screw and seal against these, the teeth of the sealing disc having substantially parallel side edges and triangular gaps between the teeth.

Background of the invention

Screw pumps of the kind mentioned above shall be able to handle pump mediums, for example oils, having a low viscosity as well as material having an extremely high viscosity, such as thick tarlike substances from the discharge of oil in the sea which have been in contact with water for a long time. Furthermore, the pump shall also be able to handle solid impurities which are present for example in connection with oil clearence, such as seaweed, plastics, dead birds or the like without being blocked.

Especially when the pump medium comprises tarlike substances having a high viscosity mixed with water the tendency is great that the substance, i.e. clods of heavy oil or the like, adheres to the threads of the screw without being expelled towards the outlet of the pump. In such cases the purpose of the sealing disc is to keep the screw fairly clean from adhering substances. Due to the fact that the threads of the pump screw are chamferred or helical the gaps between the teeth of the sealing disc must have a corresponding chamferred form, which means that the sealing disc must be manufactured in two parts to be able to be mounted in the pump housing in engagement with the driving screw. This also results in the fact that the disassembly of the sealing disc is relatively complicated, which is a great disadvantage when the pump must be quickly disassembled if for example a breakdown has occured or a too large object has entered the pump. In other screw pumps of this kind previously known (the German Patent Specification 434.327 or the French Patent Specification 1.386.020) the screw is constructed in such a way that the teeth of the sealing disc always have four side edges in active cooperation with the screw, which results in a relatively fast wearing down and thus frequent replacements of the sealing disc. Further, this construction results in the fact that the screw will get a very varying thickness of material, which makes the manufacture thereof substantially difficult. Since the disc cannot be cast it must be prepared from a solid material, which requires a heavy machining such as milling and grinding to obtain the necessary fit and thus a moderately good sealing.

By the fact that the pump is constructed usually with varying pitch in the direction towards the outlet the gaps between the teeth must be made relatively large, which brings about that the scraping effect decreases and so the pump effect.

Purposes of the invention and the most important features thereof

The purpose of the present invention is to provide a screw pump, which has a high pump effect, which exerts the sealing disc to a substantially less wearing, which effectively can keep the pump screw clean from adhering substances, which can be manufactured by casting and thus obtains a low weight simultaneously as it is simple from a constructional point of view and thus can be easily disassembled for cleaning, service and repair. These tasks have been solved by the features that the flanges, which form the thread of the screw have a substantially constant or, in the direction towards the top of the flange, tapering thickness with the exception of the threaded part of the screw situated in front of the central part of the sealing disc, which threaded part is partially formed as a bead or a ridge, and that the bead or the ridge has a measure in the rotational direction of the screw which substantially corresponds to the shifting distance of the screw in moving the sealing disc from a position at which one tooth seals to a position at which a second, next following tooth seals.

Discription of the drawings

Fig. 1 is a view from above of a screw pump according to the invention, the pump housing and the screw being shown partially in section.

Fig. 2 shows the screw and the sealing disc according to fig. 1 in another position.

Fig. 3 is a side view of the screw according to fig. 1 and 2.

Discription of embodiments The screw pump according to the invention consists of a pump housing 11, in which a driving screw 12 in the form a modified Archimedes' screw is centrally provided. The inlet of the pump has the reference numeral 13 and its outlet the reference numeral 14. The thread 21 of the screw 12 meshes with a toothed, rotatable sealing disc 15, for example made of glass fiber reinforced epoxy resin. The sealing disc is rotatable around a shaft 16 and is encased in an extension 17 of the housing projecting from the pump housing. The screw 12 is driven by a motor which is not further shown and which for example can comprise an hydraulic motor connected to the shaft end 24 of the screw turned away from the outlet.

The part of the thread 21 of the screw 12 which is situated in front of the central part of the sealing disc 15, is formed with a part 18 in the form of a bead or a ridge, which has a dimension along the thread 21, which corresponds to the displacement movement of the tooth 20 in engagement with the screw, when it changes its position shown in fig. 1 beside the central part of the disc 15, into the position shown in fig. 2 in front of said central part of the part of the screw which is situated in front of said central part. Correspondingly the sealing disc 15 is formed with ridge like gaps 15. provided between the teeth 20 of the sealing disc which are formed with substantially parallel side edges 22. Each tooth 20 is along its side edges formed with bevels 25 one at each side of the sealing disc.

By the special design of the screw and the sealing disc an effective, continuous sealing is obtained in the screw-like transport channel 23 of the pump screw and thus a good pump effect and a good scraping effect simultaneously as the sealing disc is easy to disassemble.

The screw 12 can be cast as a hollow shaft, the walls and flanges of which having substantially equal thicknesses.

Claims

1. A screw pump comprising a driving screw (12) and a toothed, rotatable sealing disc (15) meshing therewith, the teeth (20) of the disc meshing with recesses formed between the threads (22) of the screw and seal against these, the teeth (20) of the sealing disc (15) having substantially parallel side edges (22) and triangular gaps (19) between the teeth, c h a r a c t e r i z e d i n that the flanges, which form the thread (21) of the screw have a substantially constant or, in the direction towards the top of the flange, tapering thickness with the exception of the threaded part of the screw (12) situated in front of the central part of the sealing disc (15), which threaded part is partially formed as a bead or a ridge, and. that the bead or the ridge (18) has a measure in the rotational direction of the screw which substantially corresponds to the shifting distance of the screw (12) in moving the sealing disc (15) from a position at which one tooth seals to a position at which a second, next following tooth seals.

2. A screw pump according to claim 1, c h a r a c t e r i z e d i n that the screw (12) is formed as a hollow shaft, the walls and flanges of which having substantially equal thicknesses.