WHEEL AND METHOD FOR PRODUCING THE WHEEL

Abstract

A wheel, in particular a counting wheel for a meter, includes a bearing bush and a wheel rim. The bearing bush and the wheel rim are produced from different materials. The bearing bush and the wheel rim can move relative to one another in the rotational direction through a guide having complementarily corresponding guide elements on the bearing bush and the wheel rim extending continuously in the circumferential direction of the counting wheel.

Claims

1-21. (canceled)

22. A counting wheel comprising: an outer wheel rim; a bearing bush, wherein the bearing bush and the wheel rim are formed as injection-molded parts made of different plastic materials; and a guide connecting the bearing bush and the wheel rim and allowing relative rotatable movement between the bearing bush and the wheel rim.

23. The wheel according to claim 22 wherein the bearing bush and the wheel rim are connected detachably to one another by the guide.

24. The wheel according to claim 22 wherein the guide includes a pair of guide elements that engage one another, one of the pair of guide elements being a molding and another of the pair of guide elements being an indentation complementary to the molding.

25. The wheel according to claim 24 wherein the one guide element is formed as an associated component of the bearing bush or of the wheel rim, and the another guide element, being complementary to the one guide element, is formed as an associated component of the wheel rim or of the bearing bush respectively, and wherein at least one of the bearing bush and the wheel rim is formed in one piece with the associated component.

26. The wheel according to claims 24 wherein the guide elements each have a polygonal cross-sectional.

27. The wheel according to claim 24 wherein each of the guide elements has a contour that is triangular in cross section.

28. The wheel according to claim 27 wherein the guide elements are of acute-angled contour.

29. The wheel according to claim 22 wherein the bearing bush and the wheel rim are separated by a gap having a width in a range of 0.01 mm to 0.1 mm.

30. The wheel according to claim 22 wherein the plastic material of at least one of the wheel rim and the bearing bushing is a thermoplastic material being one of polyoxymethylene (POM), polyphenylene oxide PPO), polyamide (PA), polyimide (Pl), polyurethane (PUR) and polytetrafluoroethylene (PTFE).

31. The wheel according to claim 22 wherein the plastic material of the bearing bush has a higher processing shrinkage than the plastic material of the wheel rim.

32. The wheel according to claim 22 wherein the bearing bush is made of POM material and the wheel rim is made of PPO material.

33. The wheel according to claim 22 including an evaluation device disposed on the wheel for determining a numerical value represented by a rotational position of the wheel.

34. The wheel according to claim 33 wherein the evaluation device generates a light pulse, wherein a beam path of the light pulse can be measured or changed by at least one of position, shape and length of recesses on the wheel, and the beam path is a measure of the numerical value represented by the rotational position of the wheel.

35. The wheel according to claim 22 with a gap between the bearing bush and the wheel rim, wherein the wheel is formed by a method comprising the following steps: producing the wheel rim by injecting a first plastic material into a mold; producing the bearing bush by injecting a second plastic material different from the first plastic material onto the wheel rim in the mold, wherein the first and second plastic materials have different processing shrinkages; and producing the gap between the wheel rim and the bearing bushing by the second plastic material having a shrinkage greater than the first plastic material when the first and second plastic materials are being cooled.

36. A meter having at least one of the wheel according to claim 22 as a counting wheel.

37. A method for producing a counting wheel, the wheel having an outer wheel rim and an inner bearing bush, wherein the bearing bush and the wheel rim are rotatable relative to one another in a direction of rotation of the wheel by a guide extending between the wheel rim and bearing bush in the direction of rotation, the method comprising the steps of: providing a mold with a first core for producing the wheel rim; injecting a heated first plastic material into the mold to produce the wheel rim with a first guide element of the guide; providing the mold with a second core in exchange for the first core for producing the bearing bush; injecting a heated second plastic material into the mold to produce the bearing bushing with a second guide element of the guide being complementary to the first guide element; and wherein the second plastic material is different from the first plastic material.

38. The method according to claim 37 wherein the first and second plastic materials have different processing shrinkages, whereby a gap is formed between the wheel rim and the bearing bushing because the processing shrinkage of the second plastic material is higher than the processing shrinkage of the first plastic material.

39. The method according to claim 37 wherein the first and second plastic materials are thermoplastic materials selected from polyoxymethylene (POM), polyphenylene oxide (PPO), polyamide (PA), polyimide (Pl), polyurethane (PUR) and polytetrafluoroethylene PTFE).

40. The method according to claim 37 including selectively varying connecting properties and friction properties within the gap between the wheel rim and the bearing bush by introducing at least one selected additive during the production of the counting wheel.

41. The method according to claim 37 including adjusting a temperature or a temperature gradient during cooling of at least one of the wheel rim and the bearing bush with regard to respective processing shrinkages of the first and second plastic materials.

Description

DESCRIPTION OF THE DRAWINGS

[0029] Further advantageous refinements and embodiments arise from the following Figures and the invention is explained in more detail below with reference to examples.

[0030] FIG. 1: shows an inventive counting wheel for meters in a perspective representation;

[0031] FIG. 2: shows the counting wheel of FIG. 1 in a partially cut-away view;

[0032] FIG. 3: shows and inventive counting wheel in a sectional view;

[0033] FIG. 3A: shows an enlarged view of details of the counting wheel of FIG. 3 (Section A of FIG. 3);

[0034] FIG. 4: shows an inventive method in a simplified representation and in a sectional view;

[0035] FIG. 5: shows a sectional drawing of the wheel with a laterally disposed evaluation unit.

DETAILED DESCRIPTION

[0036] FIG. 1 shows an inventive counting wheel 1 for a meter in a perspective representation, comprising a wheel rim 2 and a bearing bush 3. The wheel rim 2 is made, for example, of Noryl™ 731 granulate and the bearing bush 3 is made of Hostaform® C 9021 material. The wheel rim 2 consists of an inner part 4 and an outer edge 5. On one side 7 of the outer edge 5, a gear rim 6 is arranged for installation in a transmission. A hub 8 is disposed in the inner part 4 of the wheel rim 2. The bearing bush 3 is integrated into this hub 8. The inner part 4 of the wheel rim 2 has recesses 9. There are printed members 10 on the outer edge 5.

[0037] FIG. 2 shows the meter wheel 1 of FIG. 1 in a partially cut-away view with the wheel rim 2 consisting of the inner part 4, the outer edge 5, the side 7 bearing the toothed rim 6, the hub 8 as well as the recesses 9 and the bearing bush 3. The different plastics of the bearing bush 3 and the wheel rim 2 are characterized by different shading. The wheel rim 2 is made in one piece. The bearing bush 3 has a cylindrical shell 11, on which a sliding surface 12 of the bearing bush 3 is formed. The bearing bush 3 is also formed in one piece. A guide 13 between the wheel rim 2 and bearing bush 3 can be seen in the center of the counting wheel 1. This guide 13 is arranged continuously in the circumferential direction of the counting wheel 1. The guide 13 has complementarily corresponding guide elements 13a, 13b with a triangular contour. These guide elements 13a, 13b consist of a molding 13a of FIG. 3 and an indentation 13b, as shown in FIG. 3. A gap 14, which allows the bearing bush 3 and the wheel rim 2 to rotate with respect to one another, remains. The wheel rim 2 and the bearing bush 3 are connected to one another inseparably, that is to say that they cannot be separated from one another in a nondestructive manner. Numbers 10 are printed on the outer edge 5 of the wheel rim 2.

[0038] FIG. 3 shows the counting wheel 1 of FIGS. 1 and 2 in a sectional view. Identical reference numbers denote the same parts as in FIGS. 1 and 2. The guide 13, as shown in FIG. 2, consists of guide elements 13a, 13b in the form of a protrusion 13a for the molding and a notch 13b for the indentation. The indentation 13b is disposed on the bearing bush 3 and is connected therewith in one piece. The molding 13a is disposed on the wheel rim 2 and is connected therewith in one piece. However, it is also conceivable that the indentation 13b is disposed on the wheel rim 2 and the molding 13a is disposed at the bearing bush 3. The molding 13a and the indentation 13b are complementary to one another and each has a triangular contour or a corresponding contour, which is complementary thereto. A gap 14 remains between the wheel rim 2 and the bearing bush 3.

[0039] It can be seen from the detailed view of FIG. 3A that the guide elements 13a and 13b, which are contoured triangularly in cross-section, are in each case designed with an acute angle. The molding 13a, which is triangular in cross-section, has two planar guide surfaces 19a and 20a. The guide surfaces 19a and 20a of this guide element 13a converge towards one another at an acute angle, the angle between the guide surfaces 19a and 20a being designated by α. In the present case, the angle α is approximately 60°, but it can also be between 20° and 90°. For certain applications, even configurations with an obtuse angle are conceivable. The counterpart to the molding 13a, the indentation 13b forming the notching, obviously is complementary to the triangular molding 13a; the planar, tapering guide surfaces of the indentation 13b are designated 19b and 20b. With this embodiment of the guide elements 13a and 13b, the bearing bush 3 and the wheel rim 2 are undetachably connected with one another via the guide 13. Undetachably means that the two parts, that is to say the bearing bush 3 and the wheel rim 2, can be separated only with considerable effort and, in particular, not easily, by hand. In particular, the bearing bush 3 and the wheel rim 2 cannot be separated from one another in a non-destructive manner.

[0040] In steps a to d, FIG. 4 shows an inventive method for producing the wheel rim 2 and the bearing bush 3 by means of injection molding in a simplified representation and in a sectional view. To produce the wheel, a mold 15 of FIG. 4 step a is used, which comprises a female mold 16 and a core 17 consisting of two parts 17a and 17b. First of all, the plastic is injected between the female mold 16 and the core 17 to form the wheel rim 2 (FIG. 4 step b). Thereafter, the core 17 is removed and replaced by a core 18 of narrower diameter, as can be seen in FIG. 4 step c. The plastic for the formation of the bearing bush 3 can now be injected into the plastic for the formation of the wheel rim 2, that is to say, into the cavity between the narrow core 18 and the still warm wheel rim 2 (FIG. 4 step d). By means of selecting appropriate material and processing parameters, it can be ensured that the two materials do not combine and the advantageous rotatable bearing is achieved. The different plastics have different processing shrinkages. The processing shrinkage of the plastic of the bearing bush 3 is greater than that of the wheel rim 2, that is, during the cooling of the plastics, the bearing bush 3 shrinks more than does the wheel rim 2, as a result of which the gap 14 is produced with a particularly preferred width of 0.05 mm. After the plastics have cooled down, the narrow core 18 is removed from the wheel (not shown). Of course, depending on the materials selected and the dimensions and/or the applications, it is also possible to deviate from the above-mentioned particularly preferred gap width of 0.05 mm. An advantageous wheel can have a gap width of 0.01 to 0.1 mm in the case of a measurement in the position at rest, a gap width of 0.04 to 0.07 mm being preferably provided.

[0041] FIG. 5 shows a sectional drawing of the wheel 1 with the evaluation device 21a, 21b disposed laterally. The evaluation device 21a, 21b is used to read the numerical value indicated in each case by the position of the wheel 1, which can represent a numerical value of a counting wheel, for example, of a water meter. The evaluation device 21a, 21b preferably is an optical transmitting unit 21a and a receiving unit 21b, which, by means of the evaluation of the position and/or shape and/or arrangement and/or length of the recesses 9 of the wheel 1, disposed along the direction of rotation, determines the numerical value represented by the position of the wheel 1. The recesses 9 preferably are arranged on the wheel rim 2, but can also be arranged on the bearing bush 3 or on the outer edge 5 of the wheel 1. Several wheels 1, disposed along an axis, can also be read in each case or altogether by means of an evaluation device 21a, 21b, which device is disposed directly at the respective wheels 1, or by a complete evaluation device 21a, 21b. The transmitting unit of the evaluating device 21a can also be part of the axis, for example, as a light guide, and send a light pulse through the bearing bush 3 and, due to the position of the bearing bush 3, possibly through likewise disposed recesses 9, determine the hereby represented numerical value. Other functional principles of the evaluation device 21a, 21b, such as capacitive or inductive methods, are also applicable according to the present invention. For this purpose, the recesses 9 must be replaced or compensated by corresponding capacitive and/or inductive signal generators or components.

[0042] In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.