LIQUID RING SCREW PUMP DESIGN

"Liquid ring screw pump design"

The present invention relates to a liquid ring screw pump design, including a housing with a suction inlet part and a pressure outlet part and within the housing rotatably provided Archimedes screw driven by a motor via a shaft.

Pumps of the above-mentioned kind are now commonly used in vacuum sewage systems onboard ships, aero planes and trains. However, such systems are also increasingly being used on land due to reduced water requirement and easy handling and treatment of waste water, as well as its flexibility as regards installation of piping and layout given by such systems.

The applicant of the present application introduced in 1987, cf. EP patent No. 0 287 350, for the first time the novel vacuum sewage system where the vacuum in the system was generated by means of a liquid ring screw pump of this kind where the pump is used as well to discharge the sewage from a vacuum tank or the like to which it is connected.

EP patent No. 0 454 794, also filed by the applicant, further shows a revolutionary improvement of a vacuum sewage system where the liquid ring screw pump is provided with a grinder or macerator and is connected directly with the suction pipe of the system, whereby vacuum is generated in the sewage suction pipe and sewage is discharged directly from the system by means of the pump.

The present invention may, or may not include such grinder provided at the inlet end of the Archimedes screw rotor.

Liquid ring screw pumps of the above-mentioned type commonly comprise a housing with a suction inlet part at one end and a pressure outlet part at the other end and within the housing rotatably provided Archimedes screw which is driven by an electric motor via a shaft. The known prior art pump and motor, as for instance shown in the above EP patent No. 0 454 794, is commonly provided with four or more separate legs or supports by which the pump and motor is attached to the floor ground where it is provided.

With the present invention is provided a liquid ring screw pump solution which is based on a much simpler design which is much simpler to produce and install.

The invention is characterized by the features as defined in the attached independent claim 1.

Advantageous embodiments of the invention are further defined in the attached dependent claims 2 - 5.

The invention will be further described in the following by way of examples and with reference to the drawings where: Fig. 1 shows a liquid ring screw pump according to the known (prior art) design including a common support solution,

Fig. 2 shows a liquid ring screw with a support design according to the invention. Fig. 3 shows a cross section of the pump as shown in Fig. 2. Fig. 1 shows, as stated above, an example of a known liquid ring screw pump 1 including a housing 2 with a suction inlet section 4 at one end and a pressure outlet section 3 at the other end and within the housing 2 rotatably provided Archimedes screw (not shown) driven by a motor 6 via a shaft (neither not shown). The inlet section 4 further includes a suction chamber which is provided with a front cover or lid 5 which is fastened to the suction chamber by means a flange connection 7 with a plurality of screw and nuts 8. In the present known example the pump including the motor is provided with two pairs of legs or supports 9, whereof one leg or support 9 for each pair is shown in the figures (the legs on the other side are not shown). In this connection it should be noted that some known solution even may have three or more pair of legs including at least one for the motor 6. The legs or supports 9 of this known prior art solution are provided on intermediate ring elements 14.

The housing 2 with the suction inlet section 4 and pressure outlet section 3 are detachably held together by means of longitudinally provided bolts 13 through these intermediate elements 14.

Fig. 2 shows a liquid ring pump according to the invention. The novel and inventive design feature of the solution as shown in this figure is the use of only one pair of legs or supports 10 provided preferably at a weight balance point between the motor 6 and pump 1 . In the example shown in Fig. 2 each leg or support 10 is designed with two wings or flaps 1 1 longitudinally arranged in relation to the pump 1 and motor 6, each with through going screw holes 12 for the attachment of the pump/motor to the floor or ground where it is supposed to be placed or used.

In the example shown in Fig. 2 the leg or support 10 is constructed as an integrated part of the pressure outlet section 3 of the pump 1 and may preferably be made of metal such as aluminium or steel by casting in one piece and then machined to finished product. On the other hand to reduce material and manufacturing costs the inlet suction section 4 and pump housing 2 may be made of polymer composite material such as composite Poly Amid (PA) or Poly Propylene (PP) materials. The inlet section 4, housing 2 and outlet sections are detachably screwed together by means of longitudinal bolts 13. The electrical motor 6 is in turn attached to the pump's pressure section 3 by separate screws 17 (see Fig. 3).

Even though the pump according to the preferred embodiment of the invention as described above may be made of a combination of metal and polymer composite material, the whole pump (all sections 2, 3 and 4 of the pump) may be made of metal or it may be made completely of a composite polymer or other suitable material.

Further, as defined within the scope of the claims, the leg or support 10 does not have to form part of the pressure section 3 as shown in Fig. 2 and explained above, but may be made as part of the pump section 2 or even as part of the motor 6. It is however important that the design of the leg or support is provided such in relation to the pump and rotor that it weight wise establishes a weight balance between this pump and motor.

Fig. 3 shows a cross section of the pump and motor as shown in Fig. 3. In a preferred embodiment of the invention, the pump is provided with only two bearings for the pump and motor, one 17 at the rear end of the electrical motor 6 and the other 16 at the pressure outlet section 3 of the pump 1 . More precisely, as can be seen from Fig. 3, the bearing 16 is provided in a recess 18 of the pressure outlet section 3 of the pump. This represents a very simple and cheap, but still strong and reliable bearing solution.

With the present invention as described above and defined in the claims, is provided a liquid ring pump with motor which is simple and cheap to produce.