METHOD AND DEVICE TO VERIFY AND MEASURE DOUBLE-TOOTHING OF A SPROCKET WHEEL

Abstract: Method to verify and measure double-toothing sprocket wheels used to verify the position of the teeth (24) of the two toothed rings (27a, 27b), a pair of contacting elements (23a, 23b) being made to cooperate respectively with one groove (25) of the first ring (27a) and one groove of the second ring (27b), a first contacting element (23a) having a position radially fixed with respect to the axis (17) of the sprocket wheel (14), the second contacting element (23b) being progressively displaced in a radial direction with respect to the axis (17) until it reaches the position of maximum possible advance, said position being compared with the reference position defined by the first contacting element (23a). Device carrying the method as above comprises a supporting assembly (21) radially movable with respect to the supporting plane (12), the supporting assembly (21) supporting two contacting elements (23a, 23b), the relative terminal ends (123) of which are shaped so as to cooperate with the grooves (25) between two adjacent teeth (24), one of the two contacting elements (23a) including a radially fixed position of reference cooperating in abutment with the groove (25) of a toothed ring (27a), the other contacting element (23b) being radially movable to approach a position wherein it abuts with a groove (25) of the other toothed ring (27b), there also being included means to compare the position of maximum radial advance of the second contacting element (23b) with respect to the reference position of the first contacting element (23a).

Description: METHOD AND DEVICE TO VERIFY AND MEASURE DOUBLE-TOOTHING OF A SPROCKET WHEEL * * * * * FIELD OF APPLICATION This invention concerns a method to verify and measure double-toothing sprocket wheels, and also the device which achieves the method, as set forth in the respective main claims . The invention is applied in the production of sprocket wheels, or pulleys for drive belts, with a straight or bihelical double-toothing. The sprocket wheel or pulleys to which the invention refers are advantageously of the type used together with the so-called positive drive belts such as those produced by the Good Year Company and known by the trade name of "Eagle". The invention is used to verify the accuracy of the correct reciprocal positioning of the teeth of two toothings so as to guarantee the production of sprocket wheels with extremely high mechanical characteristics. The sprocket wheels to which the invention refers may include teeth which coincide with respect to the center line or are offset, the offset distance being advantageously 50% of the pitch. STATE OF THE ART The state of the art covers sprocket wheels with a straight or bi-helical double-toothing . The latter comprise two coaxial rings of oblique and converging teeth , arranged substantially symmetrically with respec t to the int ermedi ate plane o f separat ion , substantially in a herringbone design . The sprocket wheels , according to the shape of the teeth , may be used to transmit movement by means of positive drive belts . In this type of sprocket wheel it is well known that the relative position of the two rings must conform with the utmost precision to that of the design, so as to guarantee the absolute coincidence of the positions of the teeth of the two rings . This is so that the sprocket wheel can collaborate with the utmost efficiency in transmitting movement, whether it engage with a mating sprocket wheel or is associated with a double-toothing drive belt. It becomes even more important to verify the reciprocal position of the two toothed rings quickly and easily when they are made separately in two successive steps and the partly worked piece is transferred from one machine to another . Traditional systems which have been proposed until now, even in those rare cases where they have found a practical application, on the one hand lack speed, simplicity and economy of use, and on the other hand are not able to ensure with the required precision the minimum tolerances such as will guarantee that high quality products with optimum mechanical characteristics will be obtained. The present applicants have designed, tested and embodied this invention in order to solve this problem by adopting a relatively simple solution, which is efficient, quick, and economical, and will guarantee extremely precise results. DISCLOSURE OF THE INVENTION This invention is set forth and characterised in the respective main claims, while the dependent claims describe variants of the idea of the main embodiment. The purpose of the invention is to achieve a method, and the relative device, to verify and measure, quickly and accurately, the correct positioning of the two toothed rings in a double-toothing sprocket wheel. The invention will be described hereinafter in one of its uses on bi-helical double-toothing sprocket wheels in a herringbone design, with the teeth oblique and converging towards the median plane of the sprocket wheel, wherein the two toothed rings are separated by a central groove. For the purposes of our explanation, we shall refer here also to the situation where the device comprises a horizontal supporting plane wherein the worked sprocket wheel is arranged with its axis orthogonal to the supporting plane, since the invention is immediately transferable to devices with a vertical or oblique plane, or to different types of sprocket wheel. It is also supposed that the two toothed rings, made in two different steps, are concentric and that the relative pitch circles coincide. A further working hypothesis adopted in the description is that the offset distance between the teeth of one ring with respect to the teeth of the other ring is 50% of the pitch. The invention is used when the bi-helical sprocket wheel has already been worked and is associated with a supporting plane . According to the invention, the verification and measuring device comprises a supporting assembly including a first waiting position remote from the finished sprocket wheel and a second working position near the sprocket wheel . According to one embodiment , the supporting plane of the sprocket wheel can be moved radially towards the supporting assembly . According to a variant, the supporting assembly can be moved radially with respect to the supporting plane. According to another variant, both the supporting assembly and the supporting plane are reciprocally movable in a direction radial to the longitudinal axis of the sprocket wheel . At least two contacting elements, arranged on relative different horizontal planes, are mounted on the supporting assembly. In one embodiment of the invention, the contacting elements extend substantially orthogonal to the longitudinal axis of the sprocket wheel . The terminal end of the contacting elements faces the sprocket wheel and is arranged so as to cooperate with one of the grooves defined between two adjacent teeth of the two toothed rings . The horizontal positioning planes of the two contacting elements are such that a first contacting element can cooperate, in the working position, with the teeth of a first toothed ring, while the other contacting element can cooperate with the teeth of the second toothed ring. According to a variant, the supporting plane of the sprocket wheel is vertically movable and can be adjusted in height so as to define a precise position so that the median plane of the sprocket wheel coincides, during the working step, with the median plane of separation between the two contacting elements for all the diameters of the sprocket wheel . According to another variant, at the beginning of the working step, the supporting plane of the sprocket wheel is fixed in position and the assembly supporting the two contacting elements is displaced vertically so as to align the median plane of the sprocket wheel with respect to the median plane of the two contacting elements. According to another variant, at least one of the two contacting elements can be moved vertically with respect to the other contacting element. The terminal end of the contacting elements, in one embodiment, is rounded or curved. According to a variant, the terminal end of the contacting elements is spherical. According to another variant, the terminal end of the contacting elements is shaped like a polygon. According to the invention, the vertical planes containing the longitudinal axis of the two contacting elements are arranged according to the alignment, that is the reciprocal staggering, of the teeth of the toothed rings. In the situation dealt with hereinafter as an example, therefore, the offset distance between the vertical planes containing the two contacting elements is 50% of the pitch, the pitch being the distance between two adjacent teeth of the toothed rings . According to the invention, moreover, one of the two contacting elements has a radially fixed and defined position with respect to the supporting assembly while the other contacting element is movable, with respect to the supporting assembly, in a direction radial to the axis of the sprocket wheel. According to the invention, during the verification step the movable support takes up the working position radially near the periphery of the sprocket wheel until the terminal end of the first fixed contacting element cooperates with a desired groove of the sprocket wheel. The second contacting element is arranged in a retracted position with respect to the first contacting element. The median plane of the sprocket wheel is moreover aligned precisely with the median plane of separation between the two contacting elements. According to a variant, the sprocket wheel is not made to lie directly on the supporting base, but on supporting guides which define precisely a horizontal plane of reference . When the first radially fixed contacting element, associated with the first ring, is located inside the groove between two teeth, a linear measuring assembly associated therewith defines a precise and defined radial position of reference, or zero. Advantageously, the terminal end of the contacting elements is shaped so that the point of maximum radial advance allowed should coincide with the pitch circle of the teeth of the toothed rings. Then, the second contacting element associated with the second ring is displaced radially, so that its terminal end part shall be located inside the groove defined between two teeth of the second ring, as far as the point of maximum advance allowed. In this position, a comparator associated with the second contacting element compares the position of the second contacting element and the position of reference defined by the first contacting element . In this way the comparator can immediately supply an indication of the correct reciprocal positioning of the two rings, verifying the correct radial position of the two contacting elements, or can supply an indication of error if the second contacting element is displaced to a greater or lesser radial degree with respect to the zero position. A display associated with the comparator can supply the operator with an immediate indication with a plus or minus sign according to the extent of the deviation from the zero position. The invention not only verifies the reciprocal position of the toothings, it also measures the real extent of the staggering, by using a table in which the reading taken by the display showing the deviation between the two contacting elements is transformed into a measurement of the angular or circumferential staggering between the teeth of the toothings . ILLUSTRATION OF THE DRAWINGS The attached Figures are given as a - non-restrictive example, and show a preferential embodiment of the invention as follows: Figs 1, 2 and 3 show respectively from the front, the side and from above the verification device -for double- toothing sprocket wheels according to the invention; Fig. 4 shows an enlarged detail of Fig. 2 ; Figs. 5a, 5b and 5c show the device from Figs. 1-3 from above and in three possible situations. DESCRIPTION OF THE DRAWINGS The verification device 10 shown in the attached figures comprises a supporting tripod 11 supporting a supporting plane 12 equipped with a vertical pin 13 to position the sprocket wheel 14. The sprocket wheel 14 is of the type with a bi-helical double-toothing with a central groove 15 defining the median plane 16 of the sprocket wheel 14. The sprocket wheel 14 is arranged with its longitudinal axis 17 orthogonal to the supporting plane 12. In this case, the sprocket wheel 14 rests on two guide elements shaped like steel bars 18 to define a correct horizontal plane of reference. In this case, the supporting plane 12 can be adjusted in height so as to set the vertical position of reference of the sprocket wheel 14 defined, as we shall see hereafter, according to the diameter. The assembly to adjust the height 19 of the supporting plane 12 is associated with a measuring instrument 20 which visually displays the value of the vertical position of the median plane 16 of the sprocket wheel 14. The verification device 10 comprises a verification assembly 22 including a supporting assembly 21 on which two contacting elements are mounted; the first contacting element 23a and the second contacting " " element 23b are arranged on different horizontal planes astride the median plane 16 of the sprocket wheel 14; the first lower contacting element 23a cooperates with the lower toothed ring 27a and the second upper contacting element 23b cooperates with the upper toothed ring 27b. The vertical distance between the two contacting elements 23a, 23b may have a desired value and is a function at least of the pitch "p" of the sprocket wheel 14 and the inclination of the teeth 24 thereof. In this case, according to the type of sprocket wheel 14, the two contacting elements 23a and 23b are arranged on different vertical planes (see Fig. 3) with an offset distance of 50% of the pitch with respect to the teeth 24 of the sprocket wheel 14. The terminal end 123 of the contacting elements 23a, 23b is rounded, advantageously semi-spherical, so that it can adapt to the shape of the groove 25 between two adjacent teeth 24 and come into contact with the walls of the teeth 24. In this case, at the point of maximum advance, the terminal end 123 is located substantially in contact with the pitch circle 26 of the sprocket wheel 14. In this case, the first lower contacting element 23a is radially fixed with respect to the axis 17 of the sprocket wheel 14, while the second upper contacting element 23b is radially movable. According to a variant, at least one of the contacting elements 23a or 23b is vertically movable with respect to the other 23b or 23a. The supporting assembly 21 is associated with radial displacement means with respect to the axis 17 of the sprocket wheel 14, in this case an articulated or multiplier command handle 28. According to a variant, the radial displacement means are automatic or in any case can be automatically activated. During the verification of the reciprocal position of the teeth 24 of the two toothed rings 27a, 27b, first of all the vertical position of the center line plane of the two contacting elements 23a, 23b is adjusted, so that it coincides precisely with the median plane 16 of the sprocket wheel 14. This adjustment can be made either by displacing vertically the supporting assembly of the contacting elements 23a, 23b, or by displacing one of the two contacting elements with respect to the other, or by displacing the supporting plane of the sprocket wheel 14 with respect to the contacting elements which are kept stationary. Then, the sprocket wheel 14 is displaced radially with respect to the supporting assembly 21, with the second contacting element 23b arranged in a radially retracted position, until the terminal end 123 of the first lower fixed contacting element 23a is taken inside the groove 25 of the first ring 27a of the sprocket wheel 14, as far as the position of maximum advance, in this case coinciding with the pitch circle 26. The radial position of the first lower contacting element 23a, which is associated with a linear displacement measurer, defines the zero position which is taken as a reference by a comparator assembly associated with the second upper contacting element 23b. Then, the upper contacting element 23b is radially displaced towards the sprocket wheel 14 until its terminal end is located inside a groove 25 of the upper toothed ring 27b, as far as the position of maximum radial advance. The comparator then compares the radial " position of the second upper contacting element 23b and the reference position defined by the first lower contacting element 23a and uses means 29 to display the extent of the deviation, if there is any. In this case, there are three possible situations: - there is a perfect alignment on a vertical plane of the terminal ends 123 of the two contacting elements 23a, 23b (Fig. 5a) : the display 29 will indicate 0 and the sprocket wheel 14 will be judged acceptable; - the second upper contacting element 23b will be further forward than the first lower contacting element 23a (Fig. 5b) : the display 29 will indicate a deviation with a minus sign and the sprocket wheel 14, if the deviation is above an allowed tolerance, will be judged unacceptable; - the second upper contacting element 23b is further back than the first lower contacting element 23a (Fig. 5c) : the display 29 will indicate a deviation with a plus sign and the sprocket wheel 14, if the deviation is above an allowed tolerance, will be judged unacceptable. The measurement shown on the display 29 can be used, if the appropriate conversion tables are available, to measure the entity of the angular or circumferential deviation between the teeth 24 of the two toothed rings 27a, 27b.

Claims: CLAIMS 1 - Method to verify and measure double-toothing sprocket wheels used to verify the reciprocal position of the teeth (24) of the two toothed rings (27a, 27b) of a sprocket wheel (14) with straight or bi-helical double-toothing, the teeth (24) of the two toothed rings (27a, 27b) being able to be aligned or offset, the sprocket wheels (14) being arranged on a supporting plane (12), the method being characterised in that a pair of contacting elements, the first lower (23a) and the second upper (23b) , lying on different parallel planes, is made to cooperate respectively with one groove (25) of the first ring (27a) and one groove (25) of the second ring (27b), the median plane (16) of the sprocket wheel (14) being aligned with the center line plane between the planes on which the contacting elements (23a, 23b) lie, a first contacting element (23a) including, when in the working position, a position radially fixed with respect to the longitudinal axis (17) of the sprocket wheel (14), the fixed position defining a radial position of reference, the second contacting element (23b) being progressively displaced in a radial direction with respect to the axis (17) of the sprocket wheel (14) until it reaches the position of maximum possible advance, the position of maximum advance being compared with the reference position defined by the first contacting element (23a), the comparison defining a condition of alignment between the terminal ends (123) of the two contacting elements (23a, 23b) with a consequent acceptance of the sprocket wheel (14), or a condition of negative or positive disalignment with a consequent monitoring of a defect in the sprocket wheel (14) . 2 - Method as in Claim 1, in which, prior to verification, the supporting plane (12) of the sprocket wheel (14) is radially displaced towards the contacting elements (23a, 23b) . 3 - Method as in Claim 1 or 2 , in which, prior to verification, the contacting elements (23a, 23b) are radially displaced towards the supporting plane (12) of the sprocket wheel (14) . 4 - Method as in any claim hereinbefore, in which to obtain the alignment of the median plane (16) of the sprocket wheel (14) and the center line plane between the contacting elements (23a, 23b), the supporting plane (12) is adjusted and the value of the adjustment displayed. 5 - Method as in any claim hereinbefore, in which to obtain the alignment of the median plane (16) of the sprocket wheel (14) and the center line plane between the contacting elements (23a, 23b) , at least one of the two contacting elements (23a, 23b) is displaced, on the plane which contains them both and orthogonal to the relative positioning plane, towards or away from the other contacting elemen . 6 - Method as in any claim hereinbefore, in which, in the position of maximum advance, the terminal end (123) of the first contacting element (23a) comes into contact with the pitch circle (26) of the sprocket wheel (14) . 7 - Method as in any claim hereinbefore, in which the value of deviation between the two contacting elements (23a, 23b) is transformed into a value of measurement of the angular or circumferential staggering by means of the appropriate conversion tables. 8 - Device to verify and measure double-toothing sprocket wheels used to verify the reciprocal position of the teeth (24) of two toothed rings (27a, 27b) of a sprocket wheel (14) with a straight or bi-helical double-toothing, the teeth (24) of the two toothed rings (27a, 27b) being able to be aligned or offset, the sprocket wheels (14) being arranged on a supporting plane (12), the device being characterised in that it comprises a verification assembly (22) including a supporting assembly (21) radially movable with respect to the supporting plane (12), the supporting assembly (21) supporting at least two contacting elements, the first lower (23a) and the second upper (23b) , arranged on two planes parallel to each other astride the median plane (16) of the sprocket wheel (14) , the relative terminal ends (123) of the contacting elements (23a, 23b) facing towards the periphery of the sprocket wheel (14) and shaped so as to cooperate with the grooves (25) defined between two adjacent teeth (24) of the toothed rings (27a, 27b) , one of the two contacting elements (23a) including, in the working position, a radially fixed position of reference cooperating in abutment with the groove (25) of a toothed ring (27a) , the other contacting element (23b) being radially movable to progressively approach the position wherein it abuts with a groove (25) -of the other toothed ring (27b), there also being included comparator means to compare the position of maximum radial advance of the second contacting element (23b) with respect to the reference position of the first contacting element (23a) . 9 - Device as in Claim 8, in which the supporting plane (12) comprises guide and supporting means (18) defining a planar position of reference of the sprocket wheel (14) . 10 - Device as in Claim 8 or 9 , in which the supporting plane (12) includes position adjustment means (19) associated with display means (20) . 11 - Device as in any claim from 8 to 10 inclusive, in which the terminal end (123) of the contacting elements (23a, 23b) is at least partly rounded or curved. 12 - Device as in Claim 11, in which the terminal end (123) of the contacting elements (23a, 23b) is substantially spherical . 13 - Device as in any claim from 8 to 12 inclusive, in which the first contacting element (23a) is associated with a one- dimensional device to measure the displacement and the second contacting element (23b) is associated with comparator means . 14 - Device as in any claim from 8 to 13 inclusive, which comprises display means (29) to display the extent of the deviation of the radial positions of the two contacting elements (23a, 23b) . • 15 - Device as in any claim from 8 to 14 inclusive, in which the supporting assembly (21) is- associated with radial displacement means (28). 16 - Device as in any claim from 8 to 15 inclusive, in which the contacting elements (23a, 23b) , with respect to a plane parallel to the axis (17) of the sprocket wheel (14) , are offset according to the reciprocal staggering of the teeth (24) of the two toothed rings (27a, 27b). 17 - Method as in any claim from 1 to 7 inclusive, and device as in any claim from 8 to 16 inclusive, which adopt the contents of the description and the drawings.

Inventors: GILL SHERIDAN RALPH, GILL, SHERIDAN, RALPH
Applicants: GILL SHERIDAN RALPH, TECHNOLOGIES RESEARCH HOLDING, GILL, SHERIDAN, RALPH, TECHNOLOGIES RESEARCH HOLDING S.A.
Application year: 1998
Main classification: G01B5
IPC codes: G01B5