EP1597741B1 - Switching shaft for a rotary switch - Google Patents

Abstract

According to one embodiment of the invention, a switching shaft (11) comprising molded-on cams (17) or cam disks (15) can be created for a rotary switch. A reinforcement rib (25) which extends close to the ends of the switching shaft is provided on the outside of the switching shaft (11). Said reinforcement rib (25) is able to absorb tensile stress caused especially in the central area of the switching shaft (11) by pressure generated by switching contacts (19), allowing bending of the switching shaft (11) to be prevented.

Description

Field of application and state of the art

The invention relates to a switching shaft for rotary switch according to the preamble of claim 1. The switching shaft may have molded cams or cams and trigger switching contacts of the rotary switch.

From EP 1 239 504 A1, a multi-layer shift shaft is known, which has a core with a flattened D-profile, which can be inserted therein. From this, rib-like formations emerge at one end, which can serve to trigger switching functions.

DE 10044046 A1 shows a switching shaft with a shaft in which longitudinal webs are formed, wherein on the switching shaft lever parts are pushed. In this case, the webs on the shank engage in grooves in the lever parts in order to ensure a security against rotation. The webs are arranged around the shaft and evenly distributed.

Task and solution

The invention has for its object to improve a switching shaft mentioned above, in particular to improve the stability with optimized use of materials and production costs.

This object is achieved by a switching shaft with the features of claim 1. Advantageous and preferred embodiments of the invention are the subject of the other claims and will be in the following explained in more detail. The wording of the claims is incorporated herein by express reference.

According to the invention, an aforementioned switching shaft on its outer side on a rib-shaped or rib-like reinforcement. This runs in the axial direction and can absorb compressive stresses and, above all, tensile stresses in order to avoid bending of the selector shaft. Although it is possible on the one hand, several such reinforcements form side by side in the same direction. With suitable dimensioning, however, in many cases already a single reinforcement rib suffices. Particularly advantageous here is a one-piece molding of the reinforcement. As a result, the strength can be further increased.

The reinforcement can advantageously extend over a wide central region of the selector shaft, for example until shortly before the respective end of the selector shaft. For example, it can occupy 70% to 90% of the length of the selector shaft.

The switching shaft advantageously has a substantially constant cross section, apart from the cams or cams. In the region of the reinforcement, this cross-section is widened only by the additional cross-section of the reinforcement.

The reinforcement in rib form should preferably be continuous and integral with no breaks. On the one hand, it is possible to form the reinforcing rib with constant thickness or constant cross section. On the other hand, in certain areas in which local tensile stresses occur to an increased degree, a second reinforcing rib or a reinforcing rib with a larger 'cross section may be formed. It has proven to be advantageous if the reinforcement protrudes to an extent of the shift shaft, which is about 10% to 30%, in particular about 20%.

Advantageously, the reinforcement extends at a longitudinal region, which is opposite to a region particularly stressed by the cams or cams. This means that in order to be able to absorb the tensile stresses, the reinforcement should point in the direction of the force in which the strongest forces are exerted on the cams or cams in a specific rotational position. These forces Stirring of switch contacts or the like forth, which are operated or moved by the cams. In many cases, although switching contacts are moved in certain different rotational positions. Mostly, however, there is a particularly concentrated or central area in which the aforementioned strongest forces can be detected.

The switching shaft is made such that it consists of plastic in an outer region or has an outer plastic layer. Thus, the switching shaft on a core, which consists for example either of different and more stable material or with a constant cross-section and thus simpler. Shift shaft and / or core may be made of plastic, such as thermoplastic material. Particularly advantageously, the contour of the switching shaft or the outer region or the outer layer are applied to a core in a spraying process. As a shape of the core according to the invention has a flattened round profile, for example in D-shape. By deviating from a circular shape design an anti-rotation of the core and outer region or outer layer is achieved.

According to the invention, the reinforcement is formed in the region of the flattening of the round profile of the core or the core is arranged in this manner within the switching shaft. It is advantageous if the reinforcement does not protrude over the cross section of the round profile, which would correspond without flattening the steady course of the cross section. In other words, the shape and protrusion of the reinforcement should be tuned with the flattening of the core.

For a distortion-free as possible injection molding an aforementioned switching shaft made of plastic, it is advantageous if essentially the Thickness of an outer layer of the switching shaft, which is injected around a core, remains the same. Only in the area of the flattening of the core can this deviate. Finally, the reinforcement is advantageously injection-molded here. In addition, the contour of the cams or cams should be attached to the shift shaft in this injection process.

It is advantageous if the layer thickness of an outer layer is small compared to the diameter of the core. Thereby, a possible risk of distortion of the entire shift shaft is reduced after the encapsulation of the core due to cooling.

Another aspect of the design of the shift shaft or the arrangement of the gain is that with the mass concentration representing a reinforcing rib other mass concentrations can be compensated, which can otherwise cause distortion during spraying of the shift shaft. Such warping may be caused, for example, by the cams or cams typically being rigidly oriented in one direction or in one area. It is possible to determine a center of mass line of the cams or cams. With respect to the axis of rotation, as seen from this center of mass line, the reinforcement should extend to prevent or at least reduce warping by its own mass upon cooling of the stem after injection. In this way, long control shafts can be formed which better resist both warping during operation due to compressive forces and after an injection molding operation due to the rib-shaped reinforcement in certain embodiments of the invention.

These and other features of preferred embodiments of the invention will become apparent from the claims and from the description and drawings, wherein the individual features are realized individually or in each case in the form of sub-combinations in an embodiment of the invention and in other fields and can represent advantageous and protectable versions for which protection is claimed here.

Brief description of the drawings

Fig. 1

eine Seitenansicht einer möglichen Schaltwelle mit Verstärkungsrippe und einer Vielzahl von Nockenscheiben,

Fig. 2

einen Querschnitt durch die Schaltwelle an der Stelle einer im wesentlichen umlaufenden Nockenscheibe und

Fig. 3

einen weiteren Querschnitt durch die Schaltwelle an einer Stelle, an der sie lediglich eine abstehende Nocke aufweist.

An embodiment of the invention is illustrated in the drawings and will be explained in more detail below. In the drawings show in schematic form:

Fig. 1

a side view of a possible switching shaft with reinforcing rib and a plurality of cams,

Fig. 2

a cross section through the switching shaft at the location of a substantially rotating cam and

Fig. 3

a further cross section through the shift shaft at a location where it has only one protruding cam.

Detailed description of the embodiment

In Fig. 1, a shift shaft 11 is shown in side view. In FIGS. 2 and 3, sectional drawings are shown at different locations with differently shaped cams. It can be seen how the long shift shaft 11 is formed by a base profile 13. At the base profile 13 different types of cams 15 are formed. The cams 15 have in the illustrated embodiment, in principle, a maximum radius or are formed out of a circular disc with this maximum radius. In the cam 15 of FIG. 2, an incision 16 is taken out of the cam 15. In Fig. 3, the cam plate 15 consists essentially of a disc with a very small radius over the base section 13 also. At this disc, a projection 17 is formed.

Press against the cams 15 from below the switch contacts 19. Their compressive force or switching force is represented by the upward-pointing arrows on all cams 15. The switching contacts 19 may be a pure switching contacts, which open or close. Furthermore, as a switch contacts and variable-distance switch may be provided, for example, for thermal expansion switch with default setting of a switching path. In this case, the cams 15 not only graded radii, but a uniformly increasing or decreasing radius. Thus, depending on a rotation angle, the switching contacts 19 can be moved slowly and continuously.

In the cross-sectional views of Fig. 2 and Fig. 3 it can be seen how the shift shaft 11 is constructed in detail. A core 21 with a flattened D-profile is surrounded or overmolded with the base profile 13. The base profile 13 has a flattening 23, which is directed upward in the drawings. Thus it can be seen how the basic profile 13 with uniform wall thickness surrounds the core 21.

In the middle of the flattening 23, a reinforcing rib 25 is formed upwardly facing. This has an approximately rectangular cross-section. From Fig. 3 it can be seen that it does not protrude beyond the radius of the other basic profile 13. From Fig. 1 it can be seen how it extends over the entire central region of the length of the switching shaft 11 and thus about 70% to 80% of the length of the switching shaft.

Thus, it can be seen that it is basically possible to arrange such a reinforcing rib 25 at any point of the base profile 13 of the switching shaft 11. Particularly advantageous is the use of a flattened round profile with D-shape of core and / or base profile. This makes it possible to provide the reinforcing rib in the region of the flattening in such a way that it does not project beyond the other radius of the base profile. Instead of a single reinforcing rib, it is also possible to arrange two or more reinforcing ribs in the region of the flattening.

Furthermore, it can be seen from the figures how the reinforcing rib 25 in the position according to the figures is arranged exactly opposite the switching contacts 19 and the forces caused by them. Thus, it can effectively prevent bending of the shift shaft 11. Since the shift shaft 11 is usually mounted at both ends, this risk of bending in the middle is greatest. In this respect, the reinforcing rib 25 is in any case particularly advantageous in the middle region.

Furthermore, it can be seen from FIGS. 2 and 3, as the center of gravity of the cams 15 with the cuts 16 or the projection 17, although not in any case can be determined easily due to their shape. However, it is certainly below the center of the switching shaft 11, which forms the axis of rotation. In this respect, it can be achieved in the manufacturing process by the reinforcing rib 25 that, in comparison to an annular base profile 13, a certain center of mass is given above the center here. As a result, the center of gravity of the cams 15 can be compensated below the pivot point insofar as that warping of the shift shaft during cooling after the injection process by unilateral mass or material deposits is avoided.

Overall, it is advantageous in the design of the switching shaft 11 and the rotary switch or the switch contacts 19 to ensure that the most uniform possible alignment of the main operating switching forces is given. This allows an existing in one place reinforcing rib.

To provide training with multiple reinforcing ribs, further flattening could be present either on the core 21, which in turn allows the provision of further flattenings corresponding to the flattening 23 on the base profile 13. Here can then be provided in the region of each flattening a projecting reinforcing rib. Furthermore, it is also possible to provide reinforcing ribs for the few or individual cams 15 under the mass balance approach discussed above. In this case they should be placed opposite to their center of mass. In this case, however, it must be ensured that the center of mass does not deviate too far from the opposite side of the continuous reinforcing rib 25.

Instead of the straight continuous reinforcing rib 25 according to the figures, it is also possible to offset the reinforcing rib in the region between individual cams 15 in the circumferential direction by a small angle. However, this offset should not be too large so as not to affect the strength properties of the reinforcing rib to absorb tensile forces too much.

Thus, in one embodiment of the invention, a shift shaft for a rotary switch can be provided which has molded cams or cams. On the outside of the switching shaft, a reinforcing rib is provided, which extends in the axial direction to just before the ends of the switching shaft. This reinforcing rib can absorb tensile stresses, which are caused by pressure forces of switching contacts, especially in the central region of the switching shaft. Thus, a deflection of the shift shaft can be avoided.

Claims (10)

1. Switching shaft for rotary switch, the switching shaft (11) having shaped on cams (17) or cam disks (15) and on the outside of the switching shaft (11) in the axial direction is shaped at least one reinforcement in the form of a rib (25) for absorbing tensile stress against the bending of switching shaft (11), which has at least one outer area or outer layer (13) of plastic and a core (21) injection moulded round with plastic for producing the switching shaft (11), characterized in that the core and optionally also the switching shaft (11) has a flattened round profile, the reinforcement (25) being shaped in the vicinity of the flattening (23) of the round profile of core (21).
2. Switching shaft according to claim 1, further characterized in that the reinforcement (25) passes over a wide, central area of switching shaft (11) and preferably up to shortly before the particular end of the switching shaft and preferably in the area with a reinforcement and/or in the area without a reinforcement there is a substantially constant cross-section.
3. Switching shaft according to claim 2, characterized in that the reinforcement (25) is continuous without interruptions and preferably with a constant thickness.
4. Switching shaft according to one of the preceding claims, characterized in that the reinforcement (25) projects from the switching shaft (11) with approximately 10 to 30% of the total diameter of said switching shaft.
5. Switching shaft according to one of the preceding claims, characterized in that the reinforcement (25) is directed in the force direction which is exerted on the switching shaft (11) in a specific rotation position in which the highest compressive forces are exerted on cams (17) or cam disks (15) by switching contacts (19) or the like, which are operated or moved by the cams or cam disks.
6. Switching shaft according to claim 1, characterized in that it is made from thermoplastic material, preferably also a core (21) of switching shaft (11), which is injection moulded.
7. Switching shaft according to claim 1, characterized in that the switching shaft round profile is a D-profile.
8. Switching shaft according to claim 1 or 7, characterized in that the reinforcement does not project beyond the round profile cross-section and which, without flattening, corresponds to the continuous course of the cross-section.
9. Switching shaft according to claim 7 or 8, characterized in that, apart from the flattening (23), the thickness of an outer coating (13) injection moulded around a core (21) of switching shaft (11) is constant and is in particular small compared with the core diameter.
10. Switching shaft according to one of the preceding claims, characterized in that, considered circumferentially, the reinforcement (25) is shaped in an area of switching shaft (11) facing that area in which there is a mass concentration of cams (17) or cam disks (15) and this is in particular the centre of gravity of the cams or cam disks relative to the cross-section.

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