Search

EP-4735778-A1 - A TOOTHED GEAR FOR A TRANSMISSION MECHANISM AND A METHOD FOR MAKING IT

EP4735778A1EP 4735778 A1EP4735778 A1EP 4735778A1EP-4735778-A1

Abstract

Described is a toothed gear (B), preferably designed to be included in a transmission mechanism (M1, M2), which includes a main body (R) made with an axial-symmetrical extension about an axis of symmetry (X) for the toothed gear (B) and which is designed to perform a rotary movement about the axis of symmetry (X). In the toothed gear (B) there are a plurality of teeth (A) distributed along a perimeter portion of the main body (R) and which extend according to a tapered geometry. The tapered geometry comprises a head portion (T), which has an arc-shaped perimeter extension defined by a head circumference (C1) defined by a head diameter (D1), a foot portion (P) which has an arc-shaped perimeter extension, defined by a foot circumference (02) defined by a foot diameter (D2), and a joining stretch (G) between the head portion (T) and the foot portion (P). The invention also relates to a method for making the toothed gear (B).

Inventors

  • SOLDAINI, FULVIO

Assignees

  • Elite Motion S.r.l.

Dates

Publication Date
20260506
Application Date
20240524

Claims (11)

  1. 1. A toothed gear (B) comprising: a main body (R) made according to an axial-symmetrical extension about an axis of symmetry (X) for the toothed gear (B) and designed to perform a rotary movement about the axis of symmetry (X); a plurality of teeth (A) distributed along a perimeter portion of the main body (R) and extending according to a tapered geometry; the tapered geometry comprising: a head portion (T) having an arc-shaped perimeter extension, defined by a head circumference (C1 ) defined by a head diameter (D1 ); a foot portion (P) having an arc-shaped perimeter extension, defined by a foot circumference (C2) defined by a foot diameter (D2); a joining stretch (G) between the head portion (T) and the foot portion (P)-
  2. 2. The toothed gear (B) according to claim 1 , wherein the foot portions (P) connect between two successive teeth (A).
  3. 3. The toothed gear (B) according to claim 2, wherein, during the engagement with another toothed gear (B’), the teeth (A, A’) of the two gears (B, B’) all pass through the primitive diameters of said teeth (A, A’), in such a way that the head (T) of the gear (B) works with the foot (P’) of the other gear (B’) and, simultaneously, the head (T’) of the other gear (B’) works on the foot circumference (C2) of the gear (B1 ).
  4. 4. The toothed gear (B) according to claim 2 or 3, wherein the ratio between the foot diameter (D2) and the head diameter (D1 ) is between 1.18 and 1.23, preferably between 1.19 and 1.22, inclusive, more preferably between 1 .20 and 1 .21 inclusive, even more preferably equal to 1 .20.
  5. 5. The toothed gear (B) according to claim 4, wherein each tooth (A) extends in height with a measurement substantially equal to the measurement of the second diameter (D2).
  6. 6. The toothed gear (B) according to claim 5, wherein the joining stretch (G) has a substantially linear extension.
  7. 7. The toothed gear (B) according to claim 5 or 6, wherein each tooth has an engaging surface (Si) with an undulating shape, defined by the tapered geometry, and also has two lateral surfaces (S1 , S2) facing each other and perpendicular to the axis of symmetry (X);
  8. 8. The toothed gear (B) according to any one of claims 1 to 7, wherein the teeth (A) lie and extend along a lying plane defined by the main body (R) and along a lateral perimeter surface (Sp) of the same main body (R).
  9. 9. A transmission mechanism (M1 , M2) comprising two toothed gears (B1 , B2 or B3, B4) according to any one of claims 1 to 5, wherein a toothed gear (B1 , B2 or B3, B4) is designed to transmit the motion to a further toothed gear (B1 , B2 or B3, B4).
  10. 10. A method for making a toothed gear (B) according to any one of claims 1 to 7, comprising the following steps: - one is established between module (m) and number of teeth (Z) of the toothing of the toothed gear (B) and the other is calculated from the primitive diameter (Dp) of the toothed gear (B) by means of the ratio: Dp = Z ■ m - an outer arc (a) on the foot circumference (C2) is considered, having a foot diameter (D2) equal to the chord of the outer arc (a), - the head diameter (D1 ) of the head circumference (C1 ) is calculated by means of a predetermined parameter (c), in such a way as to eliminate the interference between the teeth during the meshing of the toothed gear (B) in a transmission mechanism: D1 = D2/c - the centre of the foot circumference (C2) is identified as the midpoint of the linear segment underlying the outer arc (cc); - the foot circumference (C2) is passed through the ends of said linear segment, - the centre of the head circumference (C1 ) is identified as a point belonging to the line (Q) joining the centre of the toothed gear (B) with the foot circumference (C2), and has a distance equal to half the head diameter (D1 ) from the meeting point between the foot circumference (C2) and said joining line (Q), - the foot circumference (C2) and the head circumference (C1 ) are connected by two rectilinear segments simultaneously tangential to both said circumferences (C1 , C2).
  11. 1 1 . The method according to claim 10, wherein the parameter (c) has a value of between 1.18 and 1.23, preferably between 1.1 ,19 and 1.22, inclusive, more preferably between 1.20 and 1.21 inclusive, even more preferably equal to 1 .20.

Description

A TOOTHED GEAR FOR A TRANSMISSION MECHANISM AND A METHOD FOR MAKING IT DESCRIPTION Technical field This invention relates to a toothed gear designed to be used in transmission mechanisms, reducers and the like and a relative production process. Background art The prior art is particularly rich in examples of various types of toothed gears, including gear wheels, toothed cylinders, toothed crowns and the like used for various functions. The toothed gears are important basic mechanical parts, widely used in almost all production machinery of all traditional industrial manufacturing sectors, in the aerospace sector, rail transport, building machines, precision instruments and many others. The use of these gears is so common that the prior art has for some time settled on the use of solutions which comprise various types of design of the teeth, including gears with a standard design, that is to say, which have a specific standard with regard to their geometry. For example, the ISO 6336 standard for the gear wheels indicates an entire series of parameters which are suggested to be implemented as a function of the characteristics of the gear wheels and the type of connection to be obtained. The general dimensional factors of the gear include, for example, indications on the dimensions of the basic diameter of the gear, head diameter, primitive diameter and tooth geometry, but also indications on material and gear treatment, load distribution, lubrication factors and the like. In particular, the standard toothed gears, also called unified, generally have teeth with a tapered transversal cross-section consisting of separate curves (lateral evolutions and head and foot circles), joined only by small connections, one of which, the foot one, does not participate in the contact during the meshing. The body of each of the teeth ends in a head in the form of an acute angle connection and the teeth generally have a geometry which is quite sharp, even if they are then joined in such a way as to avoid excessive concentration of forces, and therefore, risk of interference, cracks or breakages of the tooth. Disadvantageously, this type of toothed gear has a meticulous design, since the various mechanical dimensions and parameters are interconnected, limiting combinations of the features of the gears and, above all, of the teeth. It follows that these gears are very difficult to make since they require specific production steps and processes which require specific tools, including unified milling cutters, gear making machines or gear hobs, which make the processing very costly and, consequently, the production is very expensive and time-consuming. Despite their particular embodiment, the gears with unified teeth can in any case have interference phenomena or impacts between the teeth during the mutual coupling of two or more gears; this is even more true when the unified gears have very similar primitive diameters. A first consequence of such interference or impacts consists in a concentration of stresses on certain specific points of the teeth during transmission of the contact forces. It is known that this type of gear provides a maximum of the concentrations of the stresses generally at the base of the tooth, where the connection of the foot has a very small radius. Such interferences, if neglected, reduce the working life of the teeth, resulting, in extreme cases, in the breakage of the tooth. A second consequence of such interference or impacts results in the consequent noise. More specifically, this noise, which is caused by interference during gripping between coupled gear teeth, makes the gear system annoying to any operators nearby. According to the prior art there are various alternatives with respect to the use of standard teeth with the aim of improving the efficiency of the distribution of loads and/or allowing meshes which are as free as possible from interference but which allow a different design of the gears and, in particular, of the geometry of the teeth. Patent document CN1 14704609A describes a toothed gear comprising high performance teeth for withstanding the load transmitted and received, using a curvature of the tooth which follows a quadratic curved extension. Disadvantageously, even this geometry is not easily achieved and requires the same careful design of foot of the tooth and the relative radius of connection to the body of the gear, therefore being difficult to make since it requires specific tools, such as, for example, numerical control milling cutters. Aims and summary of the invention A technical purpose of the invention is to provide a toothed gear which can be implemented in transmission mechanisms which overcomes the drawbacks present in the prior art. An aim of this invention is therefore to provide a toothed gear which is able to reduce the concentration of the forces on the teeth and obtain a greater distribution of the contact force on the entire tooth, simultaneously improving th