The present invention relates to a roller of a support arrangement for a rotary milking platform, wherein the support arrangement comprises a first rail member fixedly connected to the rotary platform, a second rail member stationarily arranged in a position below the platform, and a plurality of rollers arranged in a vertical space between the first rail member and the second rail member, wherein said roller is one of said plurality of rollers, and comprises a peripheral surface to be in contact with a contact portion of the first rail member and a contact portion of the second rail member. The roller rolls on the stationary second rail member at the same time as it supports and provides a rotary motion of the first rail member and the platform above the stationary second rail member. The roller is a support roller which forms an underlying support of the platform. The support rollers of the support arrangement are to support the whole weight of the platform and the animals on the platform during a milking process. Conventional support arrangements for rotary milking platforms comprise rollers with cylindrical contact surfaces rolling along a substantially flat contact surface of a rail member connected to the platform. The rollers may be provided with flange portions. In this case, the support arrangement comprises rollers which rotate around a respective horizontal axis such that they form a vertical support of the platform at the same time as the flanged portions provide a positioning of the platform in a horizontal plane. A support arrangement comprising rollers without flange portions includes support rollers which rotate around a horizontal axis and side rollers which rotate around a vertical axis. The support rollers form a vertical support of the platform and the side rollers provide a horizontal positioning of the platform.

A rotary milking platform supporting cows is heavy and the load on the rollers is high. The rollers are many times manufactured by a plastic material such as nylon. Especially the side portions of the contact surface of the rollers may become worn out. The side portions of the contact surfaces can start to crack and parts of them can fall off. Furthermore, it is difficult and time consuming to exchange worn out rollers supporting a rotary milking platform.

SUMMARY OF THE INVENTION The object of the present invention is to provide a roller of a support arrangement for a rotary milking platform which has a design such that it obtains a longer life than prior art rollers.

This object is achieved by the initially defined roller which is characterised in that the peripheral surface of the roller comprises two bevelled surfaces arranged at opposite sides of the contact surface which are located at a smaller distance from a rotary axis of the roller than the contact surface. A roller of a support arrangement for a rotary platform is subjected to large loads, which results in stresses in the roller. Cracks and other kinds of deformations are usually initiated in areas with high stress concentration. Consequently, it is important to distribute the stresses substantially evenly in the roller such that stress concentrations are avoided. Stress concentrations are formed, for example, in sharp edge portions of a material body. In conventional cylindrical rollers without flange portions, the transition areas between the contact surface and the side surfaces are edge portions in which stress concentrations are formed. In conventional cylindrical rollers with flange portions, the transition areas between the contact surface and the flange portions are edge portions in which stress concentrations are formed. In said edge portions, the adjacent surfaces form an angle of about 90 degrees.

The stress concentration is related to the angle between the adjacent surfaces in the edge portion. The stress concentration is higher in sharp edge portions than in less sharp edge portions. In the present roller, the contact surface is surrounded by two bevelled surfaces. Thereby, the angle in the transition area between the contact surface and the adjacent bevelled surfaces will be larger than 90 degrees. Preferably, the angle between the contact surface and the bevelled surfaces will be 135 degrees or larger. Consequently, the present roller has less sharp edge portions in the transition areas between the contact surface and adjacent surfaces than a conventional roller. Thereby, the present roller will obtain less stress concentrations in the transition areas and a longer life time than a conventional roller.

According to an embodiment of the invention, the contact surface has a convex shape in an axial direction of the roller. The convex shape of the contact surface allows for some margin of error during a mounting process of the roller in relation to a flat surface of rail member. Furthermore, the convex shape of the contact surface ensures that the main load on the roller will be created on a central area of the contact surface and at a distance from the transition areas between the contact surface and the bevelled surfaces. Thereby, the stresses in the transition areas will be further reduced. The contact surface may be located at the longest distance from the rotation axis of the roller in a midway position between the bevelled surfaces. In this case, the contact surface may have a symmetric convex shape on opposite sides of said midway position.

According to a further embodiment of the invention, the entire contact surface of the peripheral surface is located at the same distance from the rotation axis of the roller. In this case, the contact surface has a cylindrical surface surrounded by bevelled surfaces. A roller with a cylindrical contact surface is relatively easy to manufacture. The bevelled surfaces may be located at a distance from the rotation axis which increases linearly from an outer end portion to an inner end portion located adjacent to the contact surface. In this case, the bevelled surfaces also have a simple design.

According to a further embodiment of the invention, the bevelled surfaces may have a convex shape. In this case, it is possible to form a very smooth transition area between the contact surface and the bevelled surfaces which further reduces the concentration of stress in the transition areas. The convex contact surface may have a larger radius of curvature than the convex bevelled surfaces. Thus, the bevelled surfaces will have a more curved surface than the contact surface.

According to a further embodiment of the invention, the roller comprises flange portions each having a radial outer surface located at a longer distance from the rotation axis than the peripheral surface. The flange portions may position the platform in a horizontal plane such that it rotates around a fixed central vertical axis. The bevelled surface of the roller may be connected to the respective flange portions via a concave curved connection portion. The bevelled surfaces form a relatively sharp angle to the vertical surface of the flange portions. In order to reduce stress concentrations in this area, it is suitable to use a concave curved connection portion between the bevelled surfaces and the vertical surfaces of the flange portions.

According to a further embodiment of the invention, the roller comprises a centre hole configured to receive a non-rotatable shaft defining a rotation axis of the roller. In this case, the roller rotates around the non-rotatable shaft. Such a roller may have a simple design. In this case, the ends of the shaft have fixed connections to suitable components arranged on opposite sides of the roller. Alternatively, the roller and the shaft are formed as a rotary unit. In this case, the shaft has to be rotatably arranged on opposite sides of the roller. The centre hole may be configured to receive a shaft connecting the roller to two elongated connection elements arranged on opposite sides of the roller. Such connection elements may constitute a connection between several of the rollers in the support arrangement. The connection element may have an extension corresponding to that of the rail members such that all rollers in the support arrangement are connected to each other, either as one circular element or as a number of interconnected elements which each extends between only a few of the rollers. Preferably, the rollers are connected to the connection element or elements at constant intervals around the whole circular support arrangement.

According to a further embodiment of the invention, the roller is manufactured of a material body in one piece. The roller may be a homogeneous body of a wear resistant material. The roller may be e.g. manufactured of a nylon material. Nylon rollers have excellent impact resistance, good load capacity, good chemical resistance, low coefficient of friction, good vibration absorbing properties and they can be manufactured at a low cost.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is now to be explained more closely by means of preferred embodiments, which are disclosed as examples, and with reference to the attached drawings.

Fig 1 shows a view of a rotary milking platform from below, Fig 2 shows a perspective view of a part of a support arrangement for a platform according to the invention, Fig 3 shows a sectional view of the support arrangement in Fig. 2 along the plane A-A,

Fig 4 shows the peripheral surface of the roller in Fig. 3 in more detail,

Fig 5 shows a support structure for a single roller according to the invention,

Fig 6 shows the roller In Fig. 6 in contact with a rail member and

Fig 7 shows a support structure for two side rollers.

BRIEF DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Fig 1 shows a rotary milking platform 1 for milking of cows, from below. The platform 1 is rotatably arranged around a vertical axis 2. The platform 1 has an outer edge portion 1 a and an inner edge portion 1 b. The platform 1 is driven by a drive unit 3. The drive unit 3 comprises an electric motor 3a, an integrated reduction gear box 3b and a drive wheel 3c mounted in contact with a lower surface of the platform 1 . The drive wheel 3c may be a pneumatic tyre. Such a drive wheel 3 makes the drive unit shock resistant as the tyre provides a cushioning effect. The drive unit 3 has a smooth start and stop action. The drive unit 3 may be infinitely variable in speed in either a clockwise or counter-clockwise direction. A first circular rail member 4 is fixedly attached to a lower surface of the platform 1 . The first circular rail member 4 may by attached to the platform by welding. The first circular rail member 4 may be directly connected to a lower surface of the platform 1 or indirectly via a suitable connection.

Fig. 2 shows a part of a support arrangement for the platform 1 . The first circular rail member 4 comprises a beam with an I- shaped cross section. The first circular rail member 4 comprises an upper horizontal portion 4a, a lower horizontal portion 4b and a vertical portion 4c connecting the upper horizontal portion 4a and the lower horizontal portion 4b. The first circular rail member 4 comprises an elongated contact portion 4d mounted on a lower surface of the lower horizontal portion 4b. The contact portion 4d may be welded to the lower horizontal portion 4b. The support arrangement comprises a second circular rail member 5 arranged on a stationary surface 6 below the rotary platform 1 by means of a suitable number of support legs 7. The second rail member 5 also comprises a beam with an I-shaped cross section. The second rail member 5 comprises an upper horizontal portion 5a, a lower horizontal portion 5b and a vertical portion 5c connecting the upper horizontal portion 5a and the lower horizontal portion 5b. The second rail member 5 also comprises a contact portion 5d mounted on an upper surface of the upper horizontal portion 5a. The contact portion 5d may be welded to the upper horizontal portion 5a. The second rail member 5 is arranged vertically below the first circular rail member 4.

The support arrangement comprises a number of rollers 8 arranged in a vertical space between the first circular rail member 4 and the second circular rail member 5. Each roller 8 is provided with a first side flange 8a, a second side flange 8b and a peripheral surface 8c arranged between the side flanges 8a, 8b. A first elongated connection element 9a and a second elongated connection element 9b are arranged on opposite sides on the rollers 8. The connection elements 9a, 9b have a corresponding circular extension as the rail members 4, 5, either as circular elements or each as a number of interconnected elements which each extends between only a few of the rollers. The connection elements 9a, 9b are provided with holes at constant intervals. The rollers 8 are rotatably arranged around bolts 10 arranged in said holes. The distance between two adjacent holes of the elongated connection elements 9a, 9b defines the distance between two adjacent rollers 8. Fig. 3 shows a cross section view of the support arrangement and one of the rollers 8 in Fig. 2. The roller 8 comprises a first side surface 8d and a second side surface 8e. The roller 8 comprises a centrally arranged hole 8f extending between the side surfaces 8d, 8e. The centre hole 8f defines a rotation axis 8g of the roller 8. The peripheral surface 8c of the roller 8 is in contact with a lower flat surface 4d- _\ of the contact portion 4d of the first rail member 4 and an upper flat surface 56· _\ of the contact portion 5d of the second rail member 5. The peripheral surface 8c of the roller 8 is located at a smaller radial distance from the rotation axis 8g than a peripheral surface of the first side flange 8a and a peripheral surface of the second side flange 8b. Thus, at least a part of the contact portions 4d, 5d of the rail members 4, 5 are located in a space between the side flanges 8a, 8b of the roller 8.

During rotation of the platform 1 , the side flanges 8a, 8b prevent side movements of the first rail member 4 and the platform 1 in relation to the rolling member 8 and the stationary rail member 5. The side flanges 8a, 8b position the first rail member 4 vertically above the second rail member 5 and the platform 1 in a horizontal plane such that it rotates around the fixed vertical axis 2. The roller 8 is rotatably arranged around a non-rotatable shaft in the form of the centre bolt 10. The centre bolt 10 has a head arranged outside the first elongated element 9a. The centre bolt 10 has an elongated body extending through a hole in the first elongated element 9a, the centre hole 8f of the roller 8 and a hole in the second elongated element 9b. The centre bolt 10 is fastened by means of a nut 1 1 arranged on the outside of the second elongated element 9b.

Fig . 4 shows the peripheral surface 8c of the roller 8 in an axial plane through the roller 8. The peripheral surface 8c comprises a contact surface 8c-| . The contact surface 8ci is surrounded by two bevelled surfaces 8c ₂ . The contact surface 8c^ has a larger width than the two bevelled surfaces 8c ₂ . The contact surface 8C is located at a longer distance d from a rotation axis 8g of the roller 8 than the two bevelled surfaces 8c ₂ . The contact surface 8c- _\ has a convex shape. The contact surface 8c is located at the longest distance from the rotation axis 8g of the roller 8 in a midway position 8c ₃ between the two bevelled surfaces 8c ₂ . Each bevelled surface 8c ₂ also has a convex shape. The convex bevelled surfaces 8c ₂ have a smaller radius of curvature than the convex contact surface 8^ . Thus, the bevelled surfaces 8c ₂ have a more curved shape than the contact surface 8c-| . However, the bevelled surfaces 8c ₂ are shaped such that they are located at a successively longer distance d from the rotation axis 8g from an outer end of the bevelled surface 8c ₂ to an inner end of the bevelled surface 8^ located adjacent to the contact surface 8c<[ . The roller 8 comprises flange portions 8a, 8b having an outer surface located at a longer distance from the rotation axis 8g than the peripheral surface 8c. Each bevelled surface 8c ₂ is connected to the flange portions 8a, 8b via concave curved connection portions 8c ₄ .

The contact surface 8^ of the roller 8 is in contact with a flat surface 4d _{1 f} 5d-i of the contact portions 4d, 5d. The convex shape of the contact surface 8^ allows a small misalignment of the roller 8 in relation to the flat contact surfaces 4d-i , 5d-i of the contact portions 4, 5. Furthermore, the parts of the contact surface 8^ located adjacent to the bevelled surfaces 8c ₂ will be less loaded than a more central part of the contact surface 8^ . Due to the convex curved shape of the bevelled surfaces 8c ₂ , it is possible to provide a smooth transition area between the bevelled surfaces 8c ₂ and the contact surface 8c-| . Such a transition area has substantially no edge portions in which stress concentrations can be created.

Consequently, the convex bevelled surfaces 8c ₂ prevents stress concentrations in the transition area between the contact surface 8Ci and the bevelled surfaces 8c ₂ . Furthermore, the curved portions 8c ₄ between the flange portions 8a, 8b and the bevelled surfaces 8c ₂ reduces stress concentrations in an area located between the vertical surfaces of the flange portions 8a, 8b and the bevelled surfaces 8c ₂ . Consequently, the peripheral surface 8c of the roller 8 has a design without sharp edge portions and substantially without stress concentrations.

Fig. 5 and 6 shows a stationary support structure 12 to be arranged in a position under a rotary platform 1. The support structure 12 supports one roller 8. The roller 8 is rotatably arranged around a centre shaft 13 and a horizontal axis 8g. The roller 8 comprises a contact surface 8ci having a flat shape in an axial direction. Thus, the entire contact surface 8^ is located at the same distance from the rotation axis 8g of the roller 8. The contact surface 8c-i is located between two bevelled surfaces 8c ₂ . In this case, each bevelled surface 8c ₂ is located at a distance d from the rotation axis 8g which increases linearly from an outer end to an inner end located adjacent to the contact surface 8c-| . Such a roller 8 has a simple design and it is easy to manufacture.

The bevelled surfaces 8c ₂ connect the contact surface 8c ₁ and the side surfaces 8d, 8e of the roller 8. In this case, the transition areas between the contact surface 8c-i and the bevelled surfaces 8c ₂ comprise an edge portion. A conventional cylindrical roller without bevelled surfaces 8c ₂ has transition areas between the contact surface 8^ and the side surfaces 8d, 8e in which said surfaces form an angle of 90 degrees in relation to each other. However, the edge portions of the present roller 8 include a larger angle than 90 degrees in the transition area between the contact surface 8^ and the bevelled surface 8c ₂ . Since the stress concentration is higher in a sharp edge portion than in a less sharp edge portion, the stress concentration will be lesser in the transition areas of the present roller 8 than in the corresponding transition areas of a conventional cylindrical roller. Due to the less stress concentration in the present roller 8, it provides advantages regarding strength and life time in relation to a conventional roller. Fig. 7 shows a stationary support structure 14 to be arranged in a position under a rotary platform 1 . The support structure 14 supports two side rollers 8i. Each side roller 8i is rotatably arranged around a vertical axis 8h. The side rollers 8i are configured to come in contact with a vertical surface of a rail member fixedly connected to the platform 1 . The object of the side rollers 8i is to prevent side moments of the platform 1 such that it rotates around a fixed vertical axis. The side rollers 8i constitute a complement to the support rollers 8 shown in Fig. 5 and Fig. 6, which have no flange portions. The load on the side rollers 8i is much smaller than the load on the support rollers 8. Therefore, it is not necessary to provide the contact surfaces of the side rollers 8i with bevelled surfaces.

The above mentioned rollers 8 may be manufactured of a material body in one piece. The material may be a nylon material. Such a material has suitable properties for supporting a heavy rotary platform. However, it is possible to manufacture the rollers 8 of other materials. Furthermore, the rollers 8 may comprise different materials in different parts.

The invention is not restricted to the described embodiment in the figures, but may be varied freely within the scope of the claims. A roller may, for example, comprise a flat contact surface 8c-i surrounded by two convex bevelled surfaces 8c ₂ . On the other hand, the roller may comprise a convex contact surface 8c ₁ surrounded by bevelled surfaces located at a distance d from the rotation axis 8g which increases linearly from an outer end to an inner end located adjacent to the contact surface 8ci .