ROTOR FOR A SCREW ROTOR MACHINE

Abstract: A rotor for a screw rotor machine, which rotor comprises a metal shaft (3, 13) and a rotor body (1) of plastics material moulded on and around the shaft, which is provided with a number of radially and helically extending projections (4) with equal distribution around the shaft, which projections (4) are provided with essentially peripherally and helically extending wings (5) of considerable width originating from the ridge of the projections (4).

Description: ROTORFORASCREWROTORMACHINE. The present invention relates to a rotor for a screw rotor machine of the kind described in the introduction of the following claim 1. On rotors of this type, with a rotor body of plastics material moulded on a shaft, the shaft is prevented from being twisted off from the rotor body by the shaft being provided with radially protruding projections distributed in equal partition around the shaft. For especially female rotors it is thereby suitable to design the projections as helical, radial flanges with the same pitch as the lands of the rotor body, in which the flanges extend a short distance into the central part of the lands. At high rpm it has turned out that the rotor bodies in spite of these measures are inclined to be broken off or separate from the shaft and its projections. The object of the invention is to bring about an additional reinforcement of the rotor body's adhesion to the shaft and its projections. This has, according to the invention, been achieved by giving the shaft's projections the characteristic features set forth in claim 1. Additional suitable embodiments have the characteristic features set forth in claims 2 to 4. By means of the peripherally directed wings of the projections a major part of the tensile force is relieved, which otherwise at the rotation of the rotor would arise at the surface of the rotor shaft due to the mass of the part of the rotor body positioned radially outside the shaft. The wings shall suitably be placed as distant as possible from the surface of the shaft. If the shrinking of the projections can be arranged to exceed the shrinking of the plastics material during the rotor's cooling at the manufacturing, even compression of the plastics material radially inside the wings might be achieved. The projections and wings belonging to them can be designed in several ways in order to support the adhesion of the rotor body to the shaft. Especially simple and efficient even from a manufacturing point of view is to let each projection be equipped with two in opposite directions extending, similar wings, originating from the projection's ridge. In this case these should be extending without disruption between the rotor's ends, and one can easily and cheaply produce the shaft with projections and wings in an extruding operation. This is suitably done by using a suitable light metal. If the shaft's rigidity has to be reinforced a tubular shaft can be extruded which then is pressed onto a steel shaft. At die extruding operation the projections and the wings can be given a helical design with the same pitch as the intended lands of the rotor body. A male rotor should in that case have as many lands as projections, at which each projection should extend a bit into the central part of the corresponding land, where the wings have the largest tensile force reducing effect. The invention will now be described in more detail in the following with reference to the accompanying drawings, which show different examples of embodiments of rotors according to die invention and on which Figures 1 and 2, respectively, are perspective views of respectively a female and a male rotor, Figures 3 and 4 are cross section views of the rotors shown in Figures 1 and 2 and Figure 5 is a cross section view of a male rotor according to a preferred embodiment. Figures 1 and 3 show a female rotor with a rotor body 1 moulded of a plastics material on a metal core 2 in a manner known per se. The metal core comprises a circular shaft 3 provided with a number of radial projections or flanges 4, extending along almost die whole lengtii of die rotor body. Along the outer edge line of each flange 4 are extending two in opposite directions directed, peripheral wings 5. The rotor body 1 has a circular cylindrical part 6, coaxial with die shaft 3 from which part the helically designed lands 7 extend. The metal core 2 is extruded with helically designed continuous flanges 4 and wings 5, at which by symmetrical reasons a flange 4 is arranged in the line with each land 7. The flanges 4 with the wings 5 can also have anodier location with respect to d e lands 7 and anotiier number, and ti ey can also be straight. The male rotor shown in Figures 2 and 4, however, must have the same number of flanges 4 as d e number of lands 10 and be helically designed together with the wings 5 in die central parts ofthe lands 10. Possibly every flange 4 may be equipped with an additional pair of wings 11. The mass of die lands 10 is considerably larger tiian die mass of die female rotor's lands 7, which makes die invention first of all intended for male rotors. The presented preferred embodiment shown in Figure 5 is a male rotor with five lands 10. It has a shaft 13 with a mainly pentagonical cross section. The flanges of d e shaft 13, are strongly dimensioned and have strongly dimensioned wings 5 with smootii transition sections between wings 5 and flanges 4 as well between flanges 4 and shaft 13. The dimensioning of the wings 5 is chosen such tiiat the same tensile stress is caused in the plastics material at the rotation of the rotor. The metal core 13, 4, 5 is extruded from an aluminium alloy and cut to the right length, tiien the ends are turned down to form the shaft ends 3. After tiiat the rotor body has been moulded on the metal core and axially somewhat in excess of the core, such that only die shaft ends 3 of the metal core are visible. It is, as mentioned before, essential that the wings 5 are placed in the central parts of the lands 10 in order to as much as possible reduce d e tensile stresses in the plastics material along the surface of the metal core 13, 4, 5. In die embodiment shown in Fig. 5 an increased bending strength has been achieved by die metal core 13, 4, 5 being extruded in the shape of a hollow body. A circular cylindrical hole 15 with a number of inwardly directed, straight lands or splines 16 have been formed, into which hole a steel shaft 17 provided with a number of grooves 18 corresponding to me lands 16 has been pressed.

Claims: CLAIMS 1. A rotor for a screw rotor machine, the rotor having a number of helically extending lands (10) and intermediate grooves forming a working face of die rotor, d e rotor comprising: a shaft member (13); a rotor body (1) made of plastics material molded on and around the shaft member (13) so as to adhere to die surface of die shaft member (13), said rotor body made of plastics material defining said lands such tiiat said lands are substantially made of plastics material; and a plurality of radially directed projections (4) extending from die shaft member (13) with substantially equal distribution around die shaft member (13); said projections (4) being integrally formed as one piece witii die shaft member (13) characterized in that said projections (4) extend helically around die surface of the shaft member (13) with die same pitch as die lands (10), said projections (4) each being associated with and in registration witii a respective corresponding land (10); and said projections (4) further having helically extending substantially peripherally directed wings (5) of considerable peripheral widtii witii smootiily rounded edges, said wings (5) being integrally formed as one piece witii said projections (4), said wings (5) being located substantially in d e central line of die corresponding land (10) and being dimensioned to relieve during rotation of die rotor a major part of tensile stresses acting on die plastics material of said rotor body (1) adhering to d e surface of die shaft member (13). 2. The rotor of claim 1 , characterized in tiiat each of said radially directed projections (4) has two oppositely directed peripherally extending wings (5) originating from an end portion tiiereof. 3. The rotor of claim 1 or 2, characterized in tiiat said radially directed projections (4) and said wings (5) extend witii substantially no disruption along the length of die rotor between respective ends of d e rotor. 4. The rotor of claim 1, 2 or 3, characterized in tiiat said shaft member (13), said projections (4) and said wings (5) comprise a single extrusion of metal material, preferably a light metal alloy.

Inventors: WICEN JAN, WICEN, JAN
Applicants: OPCON AUTOROTOR AB
Application year: 1992
Main classification: F04C18
IPC codes: F01C1, F01C21, F04C18, F04C29, F16D1