FR2492934A1 - TRANSMISSION BELT, IN PARTICULAR FOR CONTINUOUS SPEED DRIVE - Google Patents

Abstract

TRANSMISSION BELT FOR CONTINUOUS VARIATOR. THIS BELT IS CONSTITUTED BY A BODY 1 IN ELASTOMERIC MATERIAL WHICH COVERS A TENSILE RESISTANT REINFORCEMENT CONSTITUTED BY FLEXIBLE AND INEXTENSIBLE CABLES 6, PARALLEL AND CONTAINED IN THE SAME PLANE, AND INSIDE THE BODY OR FIXED RIGID 7, THE DISTANCE BETWEEN THE CONTIGUOUS RIGID BODIES BEING VARIABLE. THE INVENTION ALLOWS TO REDUCE THE VIBRATIONS OF BELTS OF THIS TYPE AND TO CORRELATIVELY INCREASE THEIR SERVICE LIFE.

Description

The present invention relates to a cour-

  transmission belt and more particularly to a belt

  transmission for continuous speed variator.

  Various types of conveyor belts are known

  mission for continuous speed variators and, in general, the transmission belts in question are constituted by a ribbon of polymer material and more specifically material

  elastomer, closed on itself in a ring, which encapsulates a structure

  a tensile strength formed by a set of flexible and non-extensible cables parallel to each other and

contained in the same plan.

  In this ribbon of polymeric material are furthermore

  preferably embedded in the mass of this ribbon

  seems to be rigid elements used to confer

  ribbon stiffness in the transverse direction and to increase

  consequently, the transmission capacity of the couple.

  Transmission belts known for va-

  continuous speed riders have many disadvantages

  vantages. A first disadvantage is in the weak

  service life of these transmission belts for varia-

  This disadvantage is so serious that it has hampered the development of continuous drives, despite the fact that the use of these drives is theoretically able to bring considerable advantages and energy savings to the machines that adopt them or which could

adopt them.

  To overcome this drawback, we have already pro-

  many types of drive belts that differ greatly in

  essentially form each other by the shape of the rigid inserts, by the shape of the strip of polymeric material and by the way in which the assembly of the rigid inserts and the strip of polymeric material has been achieved

  or coating these elements in the polymeric material. always

  However, none of these solutions has been able to overcome

  the disadvantage of the low service life of the belts

for already known variators.

  A second disadvantage is the high noise of these belts when working in said variable speed drives and, despite all the

  improvements made to the various elements of the variations

  it was not possible to significantly reduce this

excessive noise.

  The object of the invention is to eliminate the inconveniences

  the above-mentioned known drive belts so as to provide these belts with a long service life and to enable quiet operation of the drives

of speed that use them.

  The subject of the invention is a conveyor belt

  mission comprising a belt body of polymer material

  closed on itself in a ring which encapsulates a structure

  aunt to traction formed of a set of cords parallel to each other and contained in the same plane, while

  rigid bodies spaced apart from each other along the

  the belt are attached to the body of the walking belt.

  to define in it two series-of segments

  different transverse stiffnesses, the belt being characterized in that the length of the segments of a series is variable while the length of the segments of

the other series is constant.

  The figures of the annexed drawing, given by way of non-limiting example, will explain how

the invention can be realized.

  Figure 1 is a perspective view of a

  belt for variable speed drives according to the invention.

  FIG. 2 shows a side view of a variant embodiment of a belt for variable speed drives.

speeds according to the invention.

  Following the most general principle of

  a belt for variable speed drives, following

  the invention, this course comprises an annular body

  elastomer which has a section normal to its de-

  development a trapezoidal shape and which encapsulates a tensile-resistant structure constituted by a set of cables

  parallels between them and contained in the same plane and a

  appears to be substantially rigid bodies that are spaced apart

  others in the direction of development of the belt.

  The element that is essential for the invention consists in the principle of solving the problem principle

  according to which, of the two series of segments having

  different cross-cutting priorities, which are defined by

  the rigid bodies attached to the belt, the segments of a series have a variable length while the segments of

  the other series have a constant length.

  The sequence in which the segments of different lengths succeed each other along the development of the belt is not necessarily purely random but,

  preferably, it is carefully designed with modalities

  which fall within the limits of the object of the invention.

  In particular, the invention is based on the

  the realization of segments of different lengths

  by making variable along the development of the cour-

  see the distance between the centers of continuous rigid bodies, a distance which will be called the step. The variation of pitch can be obtained in two ways: a) by using as bodies rigid bodies whose dimensions vary in the direction of the development of the belt and by placing these rigid bodies in the belt so that the distance which separates them be constant; b) using as rigid bodies

  bodies whose dimensions are identical in the direc-

  development of the belt and placing these rigid bodies in the belt in such a way that the distance

which separates them is variable.

  Of the two aforementioned modes of variation of the distance between the centers of the adjacent rigid bodies, that

  which is preferred, is that indicated above in b).

  In Figure 1, there is shown as -

  non-limiting example, in a perspective view, a segment of a belt for speed variator according to the invention. As can be seen in FIG. 1, the drive belt comprises a belt body 1 of elastomeric material having a trapezoidal shaped body in its normal section for the development of the belt and therefore has a large base 2, a small based

3 and two flanks 4 and 5.

  In the mass of the body of the belt 1 is

  embedded in a tensile-resistant structure formed of a

  seems of 6 cords, flexible, inextensible and contained in

  - the same plane whose axes are contained in a parallel plane

at the base of the belt.

  In the case of materials, cords may be made of glass fiber, aliphatic or aromatic polyamide steel, carbon fiber or

  other material having a high tensile strength.

  In the mass of the body 1 of the belt are

  drowned a set of rigid inserts 7 all identi-

between them.

  Each rigid insert is constituted by a piece of folded sheet as will be indicated below and which should be considered as an embodiment and not as being likely to limit the invention. Each inner element has two wings 8 located in planes parallel to the sides 4 and 5 of the belt and a core 9 parallel to the base of the belt and disposed inside thereof so as to be adjacent

  reinforcement cords; In addition, zones 10 of the

  reported where the connection between the wings and the core are U-shaped, with the concavity directed towards the

small base of the belt.

  A feature that is important according to the invention to achieve the proposed goals is to determine the number of inserts 7 to be embedded in the body 1 of the belt or any

way, related to this body.

  It has been found experimentally that the condition

  to complete for the best results is to find

  ver the number of interior elements 7 by the following formula:

SM

  N = (1 + E) where N is the number of reported elements 7 to be found; Sm is the average development of the belt, defined by the length of the circumference which passes through the middle of the thickness of the elements reported at the level of the soul of these elements; a is the length of the inserts, measured in the direction of development of the belt; is a coefficient deduced experimentally and whose values can be chosen in the range whose limits are 0.6 and 1.4 The choice of the value of the coefficient cx is made by the technician on the basis of the stiffness characteristics at the bending and transverse rigidity that one

wants to give the strap.

  In particular, if we want to obtain

  rigid belts, one chooses for the coefficient a

  their neighbors the smallest value of the interval between

  experimentally while, if we want to obtain belts with a lower stiffness, we choose for the coefficient a values close to the higher value

of the aforementioned interval.

  As mentioned above, the characteris-

  The fundamental feature of a belt according to the invention is that it avoids giving an orderly succession to the rigid inserts embedded in the belt or otherwise attached to the belt, all of which are

  dimensions and arranged at mutual distances between

  (that is, avoiding a provision

constant pitch).

  However, among the infinite number of modes in which pitch variability can be obtained, the best results with regard to simplicity of construction can be obtained by choosing two values.

  of steps determined as described below.

  Of the two aforementioned steps, one will be smaller than the other and in this memo, the smallest step will be called not short and will be designated by the symbol Pc while the large step will be called not long and will be designated by the

symbol pe.

  The total number of steps; not short plus not - long is equal to the number N of reported items that has been

defined above.

  The distribution between long and short steps should be established as follows: total number of long steps Ne is determined by the relation: Ne = EN Therefore, the number of short steps Nc is Nc = (1 - 3) NOT

  o the coefficient 3 has a value chosen in the inter-

  range between 0.3 and 0.7 and preferably 0.5.

  The length of the different steps can be

denies as follows:

  the short pitch Pc can be determined by the

  next mule Sm Pc (i + XX) No Sm is the average development of the belt; N is the number of rigid inserts embedded in the belt or attached to the belt in any way; X is a coefficient selected from the range of values whose limits are 0.1 and 0.9 and is preferably selected in the range of from 0.25 to 0.50;

  f is the coefficient indicated above.

  The long step pe can be determined on the basis of the following formula: p (i Pc The dimensions of the steps, the long step pe and the short step pc Once established, the number of possible combinations of these steps is infinite and all these combinations must be considered as falling within the scope of the invention, in the sense that they are all capable of reducing to a certain extent the vibrations and of attenuating the

  noise of a drive belt according to the invention.

  However, of all the possible combinations

  Some of them are capable of providing

  AD5 ienazian 5e viTt.ons and these z.its puar all the plssan-

  these transmitted by the belt according to the invention in a speed variator and which also make it possible to obtain an advantageous simplification of a belt for a variator

  according to the invention from the point of view of the construction.

  The criterion for establishing these advantageous combinations

  taggers and their definition is as follows.

  Since the zone of contact between the belt and the pulleys is substantially shorter in length than the development of the belt itself, it is possible to subdivide the belt theoretically into several equal segments between them so as to be able to establish the same sequence.

step for all segments.

  This simplifies the construction of the

  belt for variator according to the invention.

  In each segment, the sequence which is able to ensure a reduction of the vibrations for all the speeds and all the transmitted powers is that of the criterion of symmetry obtained by symmetrical groups

steps.

  In particular, the most basic grouping is that formed by a single short step or

a single long step.

  More complex groups can be formed by using a succession of two or more short steps or two or more long steps or, finally, using in each grouping short steps and long steps arranged in a sequence. symmetrically like, for example,

  not long, not long, not short, not short.

  The groupings described constitute the ele-

  which can be used for the formation of the above-mentioned sequences, which are obtained by placing one at

  following from the other groupings of different types. AC-

  essential feature of the invention which makes it possible to reduce to a reduced and uniform value the vibrations and the noise emitted by a belt, during operation of the variator is that each group of steps is followed by a

symmetrical grouping.

  For example, if a group is formed of

  three short steps, he will immediately be followed by a group-

  three steps long and then we can insert, for example the group not short - not long - not short, which will follow the grouping not long - not short - not long.

  Another fundamental characteristic of the

  vention is the sequence that helps to reduce noise and

  decrease the vibrations with the most uniformity.

  The sequence in question is the following Pepe PP ee acPc Pe e Pccc c eee PcPc Pepe PCPC Pepe PCPc PCPc Pepe Pepe PcPc cPc Pepe PcPc Pepe Pepe PcPc Pepe Pcpc PCPc Pepe Pepe PcPc Pcpc Pepe Pepe PcPc Pepe PcPc Pepe PcPc PcPcs Pepe Pcc PCPC PCPC PCPC Pepe Pepe Pepe ee o obviously, pe indicates a long step and Pc indicates a step

short.

  All that has been said above relates to the particular embodiment shown in FIG. 1 where the rigid inserts are embedded in

  the elastomeric material body of the belt.

  However, all that has been said about the embodiment shown in FIG.

  repeated for the variant embodiment shown on the

  2, on which the rigid inserts are externally

  in the body of the belt and are fixed externally

to this last.

  As can be seen in fact in Figure 2, the variator belt shown in this figure

  has a belt body 1 made of elastomeric material which

  dress a tensile-resistant structure formed of a set

  ble of flexible and non-extensible cables 12 parallel to each other and contained in the same plane. On one side of the body There are reliefs 13 of the belt whose number, mutual distances and distribution are calculated

  means of the formulas indicated in the description of the mode of

  embodiment illustrated in Figure 1.

  Embossed elements 14 are mounted on the reliefs 13, each having the shape of a small prismatic block which has surfaces inclined in the planes of the flanks of the body 11 of the belt and which is provided with

  a cavity capable of containing a relief 13.

  In addition, each small prismatic block pre-

  two fins 15 intended to come into contact with the face of the belt body which is the opposite of that

hence the reliefs 13.

  As already mentioned above, the preferred embodiment of a drive belt according to the invention is that indicated in point b) described above, that is to say that which is obtained by assembling or embedding in the body of the belt rigid bodies of identical dimensions which are arranged so that the distances between the bodies

rigid are variable.

  Experimental formulas indicated above

  are therefore also valid in this case.

  However, the field of the invention also comprises the solution idea indicated in point a) described above, in which the rigid bodies have dimensions which vary in the direction of the development of the belt while the distances separating the rigid bodies are constant. For the solutions currently described, the formulas given above are formally identical although the meaning of the symbol a is modified and is the following:

  a denotes the width of the free spaces, that is to say the

  between an insert and the next insert.

  With the changes of meaning of the sym-

  above, the values of f and i are the same as those indicated above and the variants described for the preferred embodiment which have been indicated above.

are all valid.

  With a belt according to the invention,

  achieve the goals and this can be demonstrated experimentally.

  sprawl. The explanation of why these revisions

  Experimental results are obtained may be the following.

  A variable speed drive belt is a transmission element which, therefore, includes

  minus two pulleys with which the belt is engaged.

  The transmission of the movement between the belt and the pulleys is effected by contact between the flanks of the

  belt and the flanks of the grooves of the pulleys.

  In the variator belt are embedded or fixed in any way rigid bodies which, when in contact with the flanks of the grooves of the pulleys, produce shock phenomena which give

  birth to vibration of the belt and / or the pulley.

  The existence of these vibrations is, in the first place, a source of noise and it causes, secondly, uncontrollable overload of the belt. These surcharges He 2492934

  cause cracks in this belt and are therefore

  cause the short service life of the belt.

  It is therefore obvious that by reducing and unifying

  forming the vibrations of the belt thanks to the solution according to the invention, it is possible to increase the service life of the belt and to reduce the noise of the drives of the belt.

  speed during their operation.

  It goes without saying that modifications can be made to the embodiments which have just been described, in particular by substitution of equivalent technical means,

  without departing from the scope of the present invention.

Claims (8)

  1. Transmission belt comprising a belt body of polymer material, closed on itself ring, which surrounds a tensile structure formed of a set of cables parallel to each other and contained in the same plane, while rigid bodies spaced apart from one another along the development of the belt are fixed to the body of the belt so as to define in this belt two series of segments having different transverse stiffnesses, this belt being characterized in that the length of the segments of one series is variable while the length of the segments of the other series is constant.   2.- Transmission belt according to the   characterized in that the series of segments of constant length is that of the rigid bodies, the number of which is given by the formula Sm N = (1 + z) ao Sm is the average development of the belt, a is here   dimension of the rigid body, measured in the direction of development   of the belt and x is the coefficient selected in   the range of values whose limits are 0.6 and 1.4.   -3.- Transmission belt according to the   1, characterized in that the variation of the length   of the series of segments of variable length is a variation   bility of not rigid bodies fixed in the belt.   4.- Transmission belt according to the   3, characterized in that the variability of the pitch of the rigid bodies is due to the presence of two constant steps, one of which is of greater value than that of the other, and the ratio (1 +) linking the long pitch to the pitch short being included   between the limit values 0.1 and 0.9.   5.- Belt of transmission according to the re-   claim 4, characterized in that the ratio (1 + Y) linking the long pitch to the short pitch is preferably between limit values 0.25 and 0.50.   6.- Transmission belt following one   any of the preceding claims, characterized in that   that the short pitch (pc) is defined by the following formula: Sm pc (1 +) N   o Sm is the average development of the belt, N is the   number of rigid bodies attached to the belt, there is the report   port linking the long pitch to the short pitch, minus one and Y is a coefficient between the limit values 0.3 and 0.7   7.- Transmission belt according to the   6, characterized in that the value of the coefficient 3 is preferably 0.5.   8.- Transmission belt following one   any of the preceding claims, characterized in that   that the long pitch Pe is defined by the formula Pe = (1 + X) Pc 9.- Transmission belt following one   any of the preceding claims, characterized in that   that on the development of the belt we can distinguish repeated segments o, in each segment, there are symmetrical sequences of steps.   10.- Transmission belt according to the claim   9, characterized in that the symmetrical sequence is the following sequence:   pePe - Pcc - PePe - PcPc - PePe - PcP cPc Pc PePe -   PcPc PePe Pcpc - PePe -pcPc - PePe PePe PePe -pcPc -   pP-pe - pcP - ppe -Pepe - pcPc Pepe pppp -Pcp - c c e c e c e c e c c e c c c c   PePe - PePe pcpc -PcPc - PePe - PePe -pcpc - ePe - PCPC -   PePe PcPc -pcPc - PePe -PcPc pcPc -PcPc c- Pcpc - PePe - PePe - Pepe - Pe Pe-   O Pe is a long step and a short step.