Vane for a vane cell pump and vane cell pump

A vane for a vane cell vacuum pump. The vane can be rotated about an axis of rotation by a rotor in a pump chamber and guided in the longitudinal direction in the rotor, with an upper side and a lower side to abut against the bottom and the ceiling of the pump chamber, with a rear side opposite a front side to limit the pressure chambers, with at least one face to slidably abut against an inside wall of the pump chamber on the casing side. The vane comprises a base body of a first plastic material and a vane end molded of a second plastic material to the base body forming the face. The base body comprises a mounting section around which the vane end is formed. The mounting section comprises at least one recess transverse to the front side and/or the rear side.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of German Patent Application No. 10 2015 213 098.3 filed Jul. 13, 2015, the entire disclosure of which is incorporated herein by reference.

BACKGROUND

The invention relates to a vane for a vane cell pump—in particular, for a vacuum pump—as well as a vane cell pump—in particular, a vacuum pump.

A vane cell pump with generic vanes is known, for example, from WO 02/25113 A1. The vanes shown there comprise an upper side and a lower side to abut against the bottom and against the ceiling of a pump chamber, wherein the vanes also provide a front side and a rear side opposite the front side to limit the pressure chambers formed in the pump chamber. The vane also provides two faces to slidably abut against an inside wall of the pump chamber on the casing side, wherein the vane comprises a base body made of a first plastic material and a vane end that is molded to the base body, forms the face of the vane, and consists of a second plastic material. The base body is preferably made of a thermosetting plastic that is comparatively inexpensive, wherein the vane end preferably consists of a thermoplastic that has favorable wear and tear and friction properties. The base body comprises a mounting section around which the vane end is formed and which comprises grooves running parallel to the face of the vane. These grooves are filled, in particular, by the material of the second plastic during the molding of the vane end.

Starting with such a vane, as previously known from WO 02/25113 A1, the present task of the invention consists in creating a vane and a corresponding vane cell pump that, in particular, also operates reliably at higher temperatures and with which higher pump performances can also preferably be provided.

BRIEF SUMMARY

This aim is achieved by a vane having the features of claim1. In particular, such a vane provides that the mounting section comprises at least one recess that runs in a direction transverse to the front and/or rear side. The provision of such a recess in the mounting section has the advantage that the front side can be molded securely to the base body, so that the pump can be safely operated even at higher temperatures and/or when the pump's dimensions are larger, and, in particular, when the vanes are built higher. For the known vanes, it has, in particular, been discovered that at higher operating temperatures, the vane ends are no longer securely fixed to the base body due to the different coefficients of expansion of the different plastics, but conditionally move, in particular, in the direction orthogonal to the upper or lower side with respect to the base body. By providing at least one recess—and, preferably, several recesses—which are provided in a transverse direction on the mounting section and in which the second plastic material of the vane end engages when the vane end is molded, an improved arrangement of the vane ends on the mounting section is achieved. A vane cell pump equipped with such a vane can be used at higher operating temperatures. Moreover, the vane may also be built higher in the direction orthogonal to the upper or lower side, without compromising the secure mounting of the vane ends on the base body. Overall, an increase in the performance of the vane cell pump can thereby be provided.

The at least one recess preferably comprises holding surfaces running parallel to the upper and/or lower side. In particular, forces acting orthogonally to the upper and/or lower side on the vane end can be diverted into these holding surfaces in the base body. A movement or separation of the vane end in the direction orthogonal to the upper and/or lower side of the vane is thereby prevented.

The vane may preferably provide vane ends made of the second plastic material on both faces; such a vane is then used in a vane cell pump with one vane.

The slidable abutment of the faces on the inside wall of the pump chamber on the casing side may be direct, or a sliding agent, such as an oil film, may be provided between the faces and the inside wall.

Advantageously, when viewing the upper or lower side of the one face from above, the contour of the one vane end is axially symmetrical to the contour of the other vane end, wherein the axis of symmetry is then, in particular, the axis of rotation or the center vertical axis of the vane.

The at least one recess is preferably provided vertically in the middle region of the mounting section. This results in an even fixation of the vane end to the base body.

As an alternative or in addition, at least one recess is preferably provided in the region of the upper side and/or lower side of the mounting section. Such a recess also contributes to the firm fixation of the vane end to the base body.

The one or several recesses may be designed such that they completely extend through the mounting section in the transverse direction. However, it is also conceivable that the recesses are designed as “dead end” recesses and provide a bottom when viewed in the transverse direction that is, in particular, formed by the mounting section.

It is particularly advantageous if the at least one recess comprises undercuts when viewed in the longitudinal direction, i.e., when viewed in the direction orthogonal to the face of the vane. As a result of such undercuts, it is prevented that the respective vane end can be lifted off the base body in the longitudinal direction during operation. Overall, an additional, better fixation of the vane end to the base body is provided.

In doing so, it is advantageous if the at least one recess is designed in the shape of a T when viewed from the transverse direction and, in particular, if the cross-bars of the T form the undercuts. Such recesses can be realized easily, and nonetheless result in a secure fixation of the vane ends.

It is, in particular, conceivable that, on the mounting section, several and/or differently designed recesses are provided that are adapted to the respective requirements of the vane end or the vane.

Furthermore, it is advantageous if the mounting section comprises one groove each on the front side and the rear side of the mounting section when viewed in the transverse direction, wherein the two grooves are provided such that they run laterally offset with respect to each other. In contrast, two longitudinal grooves, which lie in the same transversal plane as the vane, are provided according to WO 02/25113 A1 from the prior art. Due to the offset arrangement of the grooves, a better fixation of the vane end to the base body can be achieved.

In doing so, it is conceivable that the groove bars limiting the two grooves and facing away from the base body are connected by a wall section that runs diagonally to the front side and/or rear side when viewing the upper side and/or bottom side from above. By providing such a diagonally running wall section, a better transmission of the forces that act on the vane ends to the base body can be provided. This also results in a better fixation of the vane ends to the base body.

The vane ends per se can preferably be designed to run asymmetrically to the center longitudinal plane of the vane when viewed from above. This results in a more optimal adaptation of the vane end to the casing-shaped inside wall of the pump chamber, as well as a favorable distribution of the forces acting on the vane ends.

When viewed from above, the vane end may comprise a first bellied section and a flat second section running diagonally to the front and/or rear side of the vane, wherein the second section is preferably facing the low pressure chamber during operation of the vane cell pump. It has been shown that precisely such a contour of the vane contributes to good pump properties.

Furthermore, it is advantageous if the second section is adjoined by at least one additional flat third section also running diagonally to the front and/or rear side, wherein the third section encloses a smaller angle with the front side and/or the rear side than the second section or runs parallel to the second section. It has been shown that such a contour results in additional positive properties of the pump.

The aim upon which the invention is based is also achieved by a vane cell pump—in particular, a vacuum pump—that provides a pump chamber, a rotor mounted rotatably in the pump chamber, and a vane according to the invention that is mounted guidably in the radial direction in the rotor.

Additional advantages and individual embodiments of the invention are to be taken from the description below, by reference to which an exemplary embodiment of the invention is described and explained in more detail.

DETAILED DESCRIPTION

FIGS. 1 through 3show a vane10according to the invention for a vane cell pump as shown inFIG. 9, for example. The vane10has an upper side12and a lower side14. Furthermore, running orthogonally thereto, it comprises a front side16and a rear side18. At its free ends24, the vane10provides two faces20. The vane10comprises a base body22, which is made of a first plastic material that is comparatively inexpensive, break-proof, and dimensionally stable, such as PPS with glass fibers. On the base body22, the vane ends24forming the faces20are provided, which are made of a wear-resistant material, such as PEK or irradiated PA66. The vane ends24are molded to the mounting section26, which can be seen especially well inFIGS. 4 through 7.

The base body22comprises a closed front side16and a closed rear side18, as shown clearly inFIGS. 1, 2, and 3, wherein the base body as a whole is designed in the manner of a lattice, with bars28running diagonally to the front side16and the rear side18.

The vane ends24are preferably molded to the base body22in a two-component injection molding process.

As can be seen clearly inFIGS. 4 through 7, which show only the base body22without the vane ends24, the mounting sections26provide in the region of their front side and rear side, respectively, a groove30,32running parallel to the face20. The grooves do not lie in a common plane running orthogonal to the front or rear side16,18, but are arranged laterally offset with respect to one another.

As the top view according toFIG. 6in particular shows, the two groove bars33, which limit the two grooves30,32, are connected to one another via a wall section34, which, in the top view, runs diagonally to the front side16and the rear side18.

As is also shown in theFIGS. 4 through 7, the two mounting sections26, respectively, comprise four recesses36,38,40,42, which extend in a direction transverse to the front side16and the rear side18.

The recesses36and38, respectively, are provided in the center region of the mounting section26and comprise, respectively, two holding surfaces43running parallel to the upper and/or lower side12,14and a bottom45. The recess38is thereby introduced by the front side16of the base body22; the recess40, by the rear side18of the base body22.

As can be seen clearly inFIG. 5, there is a bar44between the recesses36and38; the recesses36and38thus do not completely extend through the mounting section26in the transverse direction. It is conceivable that recesses that extend completely through the mounting section in the transverse direction are also provided.

As can be seen clearly inFIG. 2 or 4, for example, the recesses38comprise undercuts46when viewed in the longitudinal direction of the vane10, i.e., orthogonal to the face20. The recesses38are designed in the shape of a T, wherein the undercuts46are formed by the free ends of the cross-bar of the T. When injection-molding the vane ends24, these undercuts46are filled with the material of the vane ends24. In this way, a secure fixation of the vane ends24to the base body22is achieved. At higher temperatures in particular, forces that act orthogonally to the upper and/or lower side can be diverted into the holding surfaces43and into the undercuts46. A movement or separation of the vane end24in the direction orthogonal to the upper and/or lower side of the vane ends24from the base body22can, therefore, not occur.

In vanes10that are built higher, i.e., in vanes in which the upper side12is spaced further from the lower side14, it is conceivable to provide additional recesses corresponding to the recesses38and40in the mounting section26.

As can be clearly seen in particular in the top view according toFIG. 3, the vane ends24are designed to be asymmetrical, wherein the center vertical axis48is axially symmetrical. In the section ofFIG. 3enlarged inFIG. 8, which shows a vane end24, it can clearly be seen that the vane ends24comprise a bellied section50that is provided to slidably abut the inside wall68of the pump chamber64during operation of the pump60. The bellied section50is adjoined by a flat second section52running diagonally to the front side16and the rear side18. The section52encloses an angle α with the rear side18of the vane10in the range of 30° to 60° and, in particular, in the range of 55°. During operation, the section52faces the low pressure chamber.

This second section52is adjoined by a third section54that runs parallel to the second section52, is set back, and is connected via an intermediate section56to the section52. It is also conceivable that the third section54runs parallel to the second section52and is, in particular, set back from this second section.

On the upper side and the lower side of the end sections, molding points58can be seen.

FIG. 9shows a vacuum pump60without a cover, which comprises a housing62, which surrounds a pump chamber64. In the housing62, a rotor66is rotatably mounted, in which the vane10shown inFIGS. 1 through 7is mounted movably in the longitudinal direction of the vane10in a vane slot. During operation of the pump, the vane ends24slidably abut an inside wall68of the pump chamber64on the casing side. In this way, the vane10divides the pump chamber64into different pressure chambers. During operation, the rotor66rotates about its axis of rotation along the arrow69, whereby air, or another fluid such as oil, is sucked in through an inlet opening70provided in the housing62, and air or another fluid is discharged through an additional outlet opening72.

The vane cell pump shown inFIG. 9with a vane10as shown inFIGS. 1 through 8has the advantage that the vane ends24are securely fixed to the base body22at higher temperatures. Due to different temperature coefficients of the material of the base body and of the material of the vane ends24, it can nonetheless be prevented that the vane ends24separate from or slide along the base body22at high temperatures or in vanes built high in the vertical direction.