Geometrical instruments – Gauge – Tooth testing
Reexamination Certificate
2000-05-09
2001-09-25
Gutierrez, Diego (Department: 2859)
Geometrical instruments
Gauge
Tooth testing
C033S501150
Reexamination Certificate
active
06293025
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention concerns a method for verifying and measuring a double-toothing sprocket wheel, and to a device for carrying out the method.
The invention is concerned with the production of sprocket wheels, or pulleys for drive belts, with a straight or bi-helical double-toothing.
The sprocket wheel or pulleys to which the invention refers are advantageously of the type used together with so-called positive drive belts such as those produced by the Goodyear Company and known by the trade name of “Eagle”.
The invention seeks to enable the accuracy of the respective positionings of the teeth of two toothings to be verified and enable sprocket wheels with extremely high mechanical characteristics to be produced.
The sprocket wheels to which the invention relates may include teeth which coincide with a center line or are offset, the offset distance being advantageously 50% of the pitch.
SUMMARY OF THE INVENTION
The state of the a 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 respect to an intermediate plane of separation, substantially in a herringbone design.
Depending on the shape of the teeth, the sprocket wheels 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 intended 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 engaging with a mating sprocket wheel or being associated with a double-toothing drive belt.
It becomes ever more important to verify the respective positions of the two toothed rings quickly and easily when they are made separately in two successive steps and the partly worked pieces are 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. One such system is that according to FR-A-2463391 which makes use of a pair of contacting elements.
An object of this invention is to provide a simple solution, which is efficient, quick, and economical, and will guarantee extremely precise results in respect of the correct positioning of the two toothed rings in a double-toothing sprocket wheel.
This invention is set forth and characterized in the respective independent claims, while the dependent claims describe variants of the idea of the main embodiment.
The invention will be described hereinafter with respect to 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, and the two toothed rings being separated by a central groove. More particularly, the invention will be described with reference to a situation where the device comprises a horizontally disposed support on which the worked sprocket wheel is arranged with its axis orthogonal to the supporting plane. The invention is however readily transferable to devices lying in a vertical or an oblique plane, or to different types of sprocket wheel. The invention may be used, in particular, with two toothed rings, made in two different steps, which are concentric and whose relative pitch circles coincide. In preferred practice 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 may be used on a bi-helical sprocket wheel which has already been worked and is associated with a support device.
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 support for the sprocket wheel can be moved towards the supporting assembly. According to a variant, the supporting assembly can be moved with respect to the support. Either such displacement can be termed “radial” to indicate a relationship to the longitudinal axis of the sprocket wheel to be verified and lying on its support. Indeed, according to another variant, both the supporting assembly and the support are reciprocally movable in a direction radial to the longitudinal axis of the sprocket wheel.
At least two contacting elements, arranged on relative horizontal planes, are mounted on the support.
In another embodiment of the invention, the contacting elements extend substantially orthogonally to the longitudinal axis of the sprocket wheel. The terminal ends of the contacting elements face the sprocket wheel and are 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 surface for 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 diameters of the sprocket wheel.
According to another variant, at the beginning of the working step, the support for 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 two contacting elements.
According to another variant, at least one of two contacting elements can be moved vertically with respect to the other contacting element.
The terminal ends of the contacting elements, in one embodiment, are rounded or curved. According to a variant, the terminal ends of the contacting elements are spherical. According to the invention, the vertical planes containing the longitudinal axes of the two contacting elements are offset according to the alignment, that is the 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 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 displaceable, 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 displaceable support takes up a 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 a 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 p
Akin Gump Strauss Hauer & Feld L.L.P.
Gutierrez Diego
Smith R. Alexander
Technologies Reasearch Holding S.A.
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