AXIAL SEALING

Abstract: The invention concerns an axial sealing for pumps or motors, in which a medium is pumped into a chamber (7), limited by a first side wall (5) and a second side wall (6). The medium is pumped by a rotating element (9), preferably a pump wheel driven by a rotatable shaft (2). Due to the use of new pump media having a lower viscosity than previously used pump media, and due to the detrimental corrosive effect of these pump media, among others on the rotatable shaft, it is necessary to provide new sealings. The axial sealing according to the invention comprises a sealing element (19) extending around the rotatable shaft (2). In the radial direction the sealing element (19) is arranged between the rotatable shaft (2) and an inlet (12) and/or an outlet (13). The axial sealing according to the invention is able to maintain sufficient pressures in the chamber at high speeds of the rotating element, under which pumps and motors for the new pump media are working. The axial sealing according to the invention is also able to maintain the sealing in case of a leak of pump medium between the side walls (5, 6) and the rotating element (9), and is also able to maintain the sealing during a standstill of the pump.

Description: Axial sealing The present invention concerns an axial sealing in a pump or a motor, comprising a housing (1) with side walls (5, 6) forming the limits in axial direction of a chamber (7), where at least one of said side walls (5, 6) has an inlet (12) and optionally an outlet (13), said pump or motor also including a rotatable shaft (2) extending through at least one shaft hole (11) in one of the side walls (5) , a rotating element (9) arranged between the side walls (5, 6) and provided with a first lateral face (9' ) opposite to one side wall (5) , and a second lateral face (9'' ) opposite to the other side wall (6), said rotating element (9) being rotatable by the rotatable shaft (2), and at least one sealing element (19) arranged between and bearing against one inner side of a side wall (5, 6) and a lateral face of the rotating element. DE 26 06 172 describes a pump with a sealing of the type mentioned above. The pump comprises a pump housing with an orbiting tooth wheel driven by a shaft. A sealing element is arranged between a lateral face of the tooth wheel and a side wall of the pump chamber. The sealing element is meant for maintaining a given pressure on the tooth wheel m the direction of the opposite side wall, in a way that the risk of leakage between the first lateral face of the orbiting tooth wheel and the first side wall of the pump chamber is reduced. However, the pump with sealing involves the disadvantage that the sealing between the first lateral face and the first side wall is very much depending on the surfaces being closely adjacent to each other. As long as the speed of the shaft and thus of the tooth wheel is limited, and as long as the medium to be pumped has a sufficiently high viscosity, the risk of a leak is small. However, if the speed is increased, and/or the medium to be pumped has a low viscosity, the risk of a leak is increasing. An occurring leak will also involve the risk of a damage of the shaft and possible bearings of the shaft, for instance through corrosion, by the medium to be pumped. Also, the sealing is arranged between metallic surfaces, which demands that the medium to be pumped has lubricating qualities . Previously, these disadvantages have not been recognised. The use of pump media, such as water, having a low viscosity compared with the more conventional pump media, and which may also damage rotatable shaft and bearings, and the demand for pumps with higher speeds required to establish sufficient pressure in media with low viscosity, have given rise to problems with regard to the durability, the operational security and the efficiency of known pumps. The purpose of the present invention is thus to produce a sealing providing a higher degree of tightness than a surface sealing between the lateral face of a rotating element such as a rotating tooth wheel and the side wall of the pumping chamber, in order to prevent leaks from the pump chamber to the rotatable shaft and thus to the environment. This is reached with a sealing characterised in that the sealing element extends around the rotatable shaft and that m the radial direction the sealing element is arranged between the rotatable shaft and the inlet, optionally the outlet . A sealing with these characteristics is efficient for the sealing between a pump chamber and a rotatable shaft, where it is required that in the case of a leak, the pumped medium does not reach the rotatable shaft, any bearings for the rotatable shaft or the surroundings. This sealing is generally suited for sealing at rotatable shafts and especially well suited for pumps with a high speed rotatable shaft. Tolerances between the lateral faces of the rotating element and the side walls of the pump housing can be maintained independently of whether the pumps or motors work with low or high speeds. When pumping fluids with a low viscosity, i.e. viscosities lower than those of many hydraulic oils, the sealing according to the invention is also well suited. Leaks caused by insufficient bearing between a lateral face of a rotating element and a side wall of the pump chamber are avoided, and the risk of capillary tube effect between such surfaces is eliminated. Thus, during standstill, the sealing prevents that pump medium is led to the rotatable shaft . In a preferred embodiment the sealing according to the invention is characterised in that at least one of the first, or the second lateral face of the rotating element, respectively, is provided with a track extending around the rotatable shaft, and that one sealing element is arranged in the track and bearing against the opposite side wall. In a further preferred embodiment the sealing according to the invention and according to the preferred embodiment mentioned above is characterised m that the sealing element consists of a wear element and an adjacent elastic element, that the elastic ring has a smallest diameter being smaller than or equal to the smallest diameter of the track, that the elastic ring has a largest diameter being smaller than the largest diameter of the track, that the elastic ring is arranged in a bottom of the track, and that the massive ring is arranged between the elastic ring and an opening of the track. Wear element and elastic element can be assembled in one unit. A sealing element consisting of a combination of a wear- resisting element and an elastic element has turned out to be useful to obtain sufficient sealing m the type of pumps and motors, in which the sealing according to the invention is primarily used. The wear-resisting sealing element can also be covered with or made of a material reducing the friction between the ring and the side wall, such as polytetraflourethen, sold under the trademark TEFLON®, alternatively PEEK. However, it is important that the smallest diameter of the elastic element is smaller than or equal to the smallest diameter of the track, to secure that the elastic element, when placed m the track, is bearing against the inner diameter of the track, and not against the outer diameter of the track. Pump medium under pressure led m the direction of the sealing element will be led into the track at its outer diameter. The pressure exerted m the track by the pump medium will then press m the elastic element towards the inner diameter of the track. At the same time the pressure exerted m the track by the pump medium will press out the wear-resisting element towards the side wall. The efficiency of the sealing will then be increased for both the elastic element and the wear-resisting element when the pressure in the pump medium is increased. An alternative axial sealing according to the invention is characterised in that the sealing is arranged between a first surface and a second surface meant for making a relative movement, that the sealing between the surfaces is placed in a recess in the first or the second surface, that the sealing is formed of a flexible element bearing against the first surface and a stiff element bearing against the second surface, and that the flexible element exerts a pressure force against the stiff element. In the following the invention is described m detail on the basis of the enclosed drawings, m which fig. 1 is a section through a pump with a first embodiment of an axial sealing according to the invention fig. 2 is a section through the pump shown m fig. 1 illustrating an internal tooth wheel and an external tooth wheel forming the pump wheel fig. 3 is a section through part of a pump chamber and a pump wheel in a pump as shown in fig. 1 fig. 4 is a section through part of a pump chamber and a pump wheel in a pump as shown m fig. 1, and with a second embodiment of an axial sealing according to the invention fig. 5 is a section through part of a pump chamber and a pump wheel in a pump as shown m fig. 1, and with a third embodiment of an axial sealing according to the invention fig. 6 is a section through part of a pump chamber and a pump wheel m a pump as shown in fig. 1, and with a fourth embodiment of an axial sealing according to the invention fig. 7 is a section through first embodiments of a massive ring and a flexible ring in an axial sealing according to the invention fig. 8 is a section through other embodiments of a massive ring and a flexible ring in an axial sealing according to the invention fig. 9 is a section through other embodiments of a massive ring and a flexible ring in an axial sealing according to the invention By means of a section, fig. 1 illustrates a pump with an axial sealing according to the invention. The pump comprises a pump housing 1. A rotatable shaft 2 is supported m bearings 3, 4 and extends into the pump housing 1 through a first side wall 5. Together with a second side wall 6, side wall 5 forms the axial limitation of a pump chamber 7. The pump housing 1 comprises a chamber wall 8. The chamber wall 8 forms the bearing ring of an external toothed rim 26, which is also the limitation of the pump chamber 7. A rotating element in the shape of an inner tooth wheel 9 is arranged m the pump chamber 7. The inner tooth wheel 9 is mounted on the rotatable shaft 2 and meant for being driven by the rotatable shaft 2. Therefore, a groove is arranged between the rotatable shaft 2 and the inner tooth wheel 9. The pump shown in the figure is a gerotor pump functioning by a medium being pumped by successive meshing between the teeth of the inner tooth wheel 9 and the outer toothed rim 26, respectively (see fig. 2) . In the following the inner tooth wheel will be called the pump wheel. The first side wall is provided with a through-hole 11 for the rotatable shaft. The second side wall is provided with an inlet 12 to the pump chamber 7 and an outlet 13 from the pump chamber 7 for the medium to be pumped. An end cover 14 bears against an outside 15 of the second side wall o and is provided with thread holes 16 for the connection of hoses or pipes (not shown} to lead the medium to and from the pump. Between the first side wall 5 and the chamber wall 8, between the chamber wall 8 and the second side wall 6 and between the second side wall 6 and the end cover 14 the sealing element 17 is arranged in track 18. Between the rotatable shaft 2 and the pump wheel 9 a further sealing element 27 is arranged. The sealing element 27 is arranged in a track 28 in the rotatable shaft. In the pump shown the sealing elements 17 and 27 are sealing rings, preferably 0- rings . Between the first side wall 5 and the pump wheel 9 a sealing element 19 is also arranged. The sealing element 19 is the axial sealing according to the invention. In the embodiment shown, the sealing element 19 consists of a massive ring 20 and an elastic ring 21. The sealing element is arranged m a track 22 m the pump wheel 9. The elastic ring 21 is arranged in a bottom 23 (see fig. 3) of the track 22, and the massive ring 20 is arranged between the elastic ring 21 and the first side wall 5 m a way that the massive ring 20 extends outside an opening 24 (see fig. 3) of the track 22 and bears against the first side wall 5. The massive ring 20 is meant for providing the sealing between the ring 20 and the first side wall and for absorbing wear loads during the rotation of pump wheel 9 in the pump chamber 7. The elastic ring is meant for providing sealing between the pump wheel 9 (7? se dansk) and the massive ring and for establishing sufficient bearing power for the bearing of the massive ring 20 against the first side wall 5. The massive ring 20 is preferably made of a material containing coal, coal fibres or graphite, or of a material covered with or made of Teflon® or PEEK, to minimise the friction between the ring 20 and the first side wall 5. The elastic ring 21 is preferably made of rubber. Fig. 2 shows a section through the gerotor pump in fig. 1. The section is made vertically in relation to the section in fig. 1 and runs through the pump chamber 7. The figure shows the rotatable shaft 2, the inner pump wheel 9, the outer tooth rim 26 and the pump chamber 7 between the inner pump wheel 9 and the outer tooth rim 26. The chamber wall 8 and the second side wall 6, the inlet 12, the outlet 13 and the track 22 are also shown. In fig. 3 a section shows a magnified part of the pump illustrated m fig. 1. Fig. 3 shows the rotatable shaft 2, the first side wall 5, the second side wall 6 w th inlet 12, the chamber wall 8, the pump chamber 7, the pump wheel 9, the sealing element 17 between the chamber wall 8 and the first side wall 5 or the second side wall 6, respectively, and the sealing element 27 between the rotatable shaft 2 and the pump wheel 9. The axial sealing 19 according to the invention is also shown. The pump wheel 9 has a first lateral face 9' opposite to the first side wall 5 and a second lateral face 9' ' opposite to the second side wall 6. As mentioned, the axial sealing comprises a massive ring 20 and an elastic ring 21. The elastic ring 21 is placed in the bottom 23 of track 22 and has a smallest diameter d 2 ι which is almost equal to the smallest diameter d ? of the track 22, and a largest diameter D ? which is smaller than a largest diameter D 22 of the track 22. The massive ring 20 is placed at the opening 24 of the track 22 and has a smallest diameter d A and a largest diameter D , the sizes of which are between the smallest diameter d z and the largest diameter D,, of the track 22. Fig. 4 shows a second embodiment of the axial sealing according to the invention. In this embodiment the axial sealing comprises a first sealing element 19' between the pump wheel 9 and the first side wall 5 and a second sealing element 19' ' between the pump wheel 9 and the second side wall 6. The sealing elements 19' and 19'' are the same as the sealing element 19 described m fig. 2. For a description of the sealing elements m fig. 4, see description under fig. 2. Fig. 5 shows a third embodiment of an axial sealing according to the invention. In the embodiment shown, the sealing between the first side wall 5 and the pump wheel 9 is provided by the first sealing element 19' as illustrated in fig. 3, whereas the track 22 is provided in the first side wall 5 in stead of in the pump wheel 9. The groove 22 of the second sealing element 19' ' between the pump wheel 9 and the second side wall 6 is still provided in the pump wheel 9, but m an alternative embodiment, it could be provided m the second side wall 6. The sealing elements 19' and 19'' are the same as the sealing element 19 described in fig. 2. For a description of the sealing elements in fig. 5, see description under fig. 2. Fig. 6 shows a fourth embodiment of an axial sealing according to the invention. In this embodiment the axial sealing is provided partly between the pump wheel 9 and the first side wall 5 or the second side wall 6, respectively, partly between the outer tooth rim 26 and the first side wall 5 or the second side wall 6, respectively. The sealing elements are the same as the sealing element 19 described in fig. 2. For a description of the sealing elements m fig. 6, see description under fig. 2. Fig. 7 shows a section of the sealing elements illustrated in fig. 2 to fig. 5. The sealing element 19 thus comprises a massive ring 20 and an elastic ring 21. The elastic ring 21 has a smallest diameter d 21 which is equal to, alternatively smaller than, the smallest diameter d 22 of the track 22, and a largest diameter D 2ι which is smaller than the largest diameter D 22 of the track 22. The massive ring has a smallest diameter d 20 and a largest diameter D 20 , the sizes of which are between the smallest diameter d 22 and the largest diameter D 22 , respectively, of the track 22. The fact that the elastic ring 21 has a smallest diameter d 2 ι which is almost equal to a smallest diameter d of the track 22, and a largest diameter D 21 which is smaller than the largest diameter O 22 of the track 22 improves the sealing qualities of the elastic ring 21. If the medium to be pumped is led from the pump chamber 7 past the bearing 25 of the pump wheel against the first side wall 5 and into the track 22, this medium, which is under pressure, will exert a pressure on the elastic ring 21 to the inside towards the smallest diameter d_ 2 of the track 22. As the smallest diameter d ?] of the elastic ring 21 is equal to the smallest diameter d 22 of the track 22, the pressure exerted on the ring 21 by the medium under pressure will cause a deformation of the elastic ring 21 in a way that the ring 21 is pressed to the inside against the bottom 23 of the track and to the outside against the massive ring 20. This pressure against the bottom 23 of the track 22 or the massive ring 20, respectively, increases the sealing effect of the elastic ring 21 and also the sealing of the bearing of the massive ring 20 against the first side wall 5. Besides, the pressure exerted by the medium in the track 22 will also press the massive ring further out against the first side wall 5. The elastic ring 21 provides sufficient sealing during standstill of the pump, whereas the pressure of the medium provides improved sealing during operation. Fig. 8 shows a different embodiment of the massive ring 20 being part of the axial sealing according to the invention. In this embodiment the massive ring 20 has the shape of an L. This gives an easier mounting of the elastic ring, as a correct placing of the elastic ring 21 in relation to the massive ring 20 is ensured. Fig. 9 shows yet another embodiment of the massive ring 20 being part of the axial sealing according to the invention. In this embodiment the massive ring has the shape of a U. Also here an easy mounting of the elastic ring 21 is provided, and besides it is possible to pre-mount the elastic ring 21 and the massive ring 20 m a way that these form only one unit. In the above, the axial sealing according to the invention is described with reference to one specific embodiment of a pump and one specific embodiment of a sealing element comprising a massive ring and an elastic ring. However, it will be possible to use the axial sealing in other types of pumps than the one shown. Thus, it will be possible to produce an inlet m the second side wall and an outlet in the first side wall, an inlet in the first side wall and an outlet m the second side wall, or both mlet and outlet in the first side wall. Other embodiments of the axial sealing can also be produced.

Claims: Patent Claims 1. Axial sealing in a pump or a motor, comprising a housing (1) with side walls (5, 6) forming the limits axial direction of a chamber (7), where at least one of said side walls (5, 6) has an inlet (12) and optionally an outlet (13), said pump or motor also including a rotatable shaft (2) extending through at least one shaft hole (11) one of the side walls (5), a rotating element (9) arranged between the side walls (5, 6) and provided with a first lateral face (9') opposite to one side wall (5) , and a second lateral face (9'') opposite to the other side wall (6) , said rotating element (9) being rotatable by the rotatable shaft (2), and at least one sealing element (19) arranged between and bearing against one inner side of a side wall (5, 6) and a lateral face of the rotating element, characterised in that the sealing element (19) extends around the rotatable shaft (2), and that in the radial direction the sealing element (19) is arranged between the rotatable shaft (2) and the let (12) , optionally the outlet (13) . 2. Axial sealing according to claim 1, characterised in that the second side wall (6) is provided with an mlet (12), that the second side wall (6) is also provided with an outlet (13), that a first sealing element (19) is arranged between the first lateral face (9' ) of the rotating element (9) and the first side wall (9) , and that the radial direction the sealing element (1) extends between the rotatable shaft (2) and the let (12) . 3. Axial sealing according to claim 1, characterised in that the second side wall (6) is provided with an let (12) , that the first side wall (5) is provided with an outlet (13), that at least a first sealing element (19) is arranged between the first lateral face (9' ) of the rotating element (9) and the first side wall (5), and at least a second sealing element (19) is arranged between the second lateral face (9'') of the rotating element (9) and the second side wall (6), and that the radial direction the sealing elements (19) extend between the rotatable shaft (2) and the mlet (12) or the outlet (13), respectively. 4. Axial sealing according to any of the preceding claims, characterised in that the sealing comprises a first circular sealing element (19') and a second circular sealing element (19''), that the first sealing element (19') is arranged between the first side wall (5) and the first lateral face (9') of the rotating element (9), and that the second sealing element (19'') is arranged between the second side wall (6) and the second lateral face (9'') of the rotating element (9), and that at least the first sealing element (19' ) extends around the rotatable shaft. 5. Axial sealing according to claim 3, characterised in that the second side wall (6) is provided with an mlet (12), that the first side wall (5) is provided with an outlet (13), that the second side wall (6) is additionally provided with a shaft hole, that the rotatable shaft (2) extends through the shaft hole (11) the first side wall (5), through the rotating element (9) and through the shaft hole m the second side wall (6), and that the first sealing element (19') extends around the rotatable shaft (2) and m the radial direction is arranged between the rotatable shaft (2) and the outlet (13), and that the second sealing element (19'') extends around the rotatable shaft (2) and m the radial direction is arranged between the rotatable shaft (2) and the mlet (12) . 6. Axial sealing according to any of the preceding claims, characterised in that the sealing element consists of a ring (20) made of a carboniferous material, alternatively made of preferably polytetraflourethen, alternatively PEEK, and an adjacent elastic ring (21) made of a different material, preferably rubber, and that the massive ring (20) and the elastic ring (21) have an approximately common circumference. 7. Axial sealing according to any of the precedmg claims, characterised in that at least the first or the second, respectively, of the lateral faces (9', 9'') of the rotating element (9) is provided with a track (22) extending around the rotatable shaft (2) , and that a sealing element (19) is arranged in the track and extends beyond an opening (24) the track (22) and is bearing against the opposite side wall (5, 6) . 8. Axial sealing according to any of the preceding claims, characterised in that the rotating element (9) is provided with a first track (22) extending on the first lateral face (9') of the rotating element (9), and a second track (22) extending on the second lateral face (9'' ) of the rotating element, that a first sealing ring (19' ) is arranged in the first track (22) and a second sealing ring (19'') m the second track (22), and that the first sealing ring is bearing against the first side wall of the housing and the second sealing ring is bearing against the second side wall of the housing . 9. Axial sealing according to any of the claims 6 to 8, characterised in that the elastic ring (21) has a smallest diameter (d 2] ) , which is smaller than or equal to a smallest diameter (d 22 ) of the track (22), that the elastic ring (21) has a largest diameter (D 2] ) which is smaller than the largest diameter (D 22 ) of the track (22), that the elastic ring (21) is arranged m a bottom (23) of the track (22), and that the massive ring (20) is arranged between the elastic ring (21) and an opposite side wall (5, 6) and extends beyond an opening (24) of the track (22) . 10. Axial sealing in a pump or a motor, characterised in that the sealing is produced between a first surface and a second surface made to make a relative movement, that the sealing between the surfaces is arranged m a recess in the first or the second surface, that the sealing is made of a flexible element bearing against the first surface, and a stiff element bearing against the second surface, and that the flexible element provides a pressure force against the stiff element.

Inventors: FROESLEV PETER, JOERGENSEN TAGE, KLAUSEN JOERN HOLGER, MADSEN INGVARD MOSBY, FROESLEV, PETER, JOERGENSEN, TAGE, KLAUSEN, JOERN, HOLGER, MADSEN, INGVARD, MOSBY
Applicants: DANFOSS AS, FROESLEV PETER, JOERGENSEN TAGE, KLAUSEN JOERN HOLGER, MADSEN INGVARD MOSBY, DANFOSS A/S, FROESLEV, PETER, JOERGENSEN, TAGE, KLAUSEN, JOERN, HOLGER, MADSEN, INGVARD, MOSBY
Application year: 1996
Main classification: F04C2
IPC codes: F04C15, F16J15