GB1588952A

GB1588952A - Driving belt

Info

Publication number: GB1588952A
Application number: GB2018578A
Authority: GB
Original assignee: Industrie Pirelli SpA; Pirelli SpA
Current assignee: Industrie Pirelli SpA; Pirelli and C SpA
Priority date: 1977-05-27
Filing date: 1978-05-17
Publication date: 1981-05-07
Also published as: BE867480A; DE2823062A1; JPS53148651A; ES470513A1; FR2392286A1; BR7803315A; IT1092253B; AR212952A1

Description

(54) DRIVING BELT (71) We, INDUSTRIE PIRELLI SpA, an Italian Company of Centro Pirelli, Piazza Duca d'Aosta No 3, 20100 Milan, Italy, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention refers to a driving belt and, in particular, to a trapezoidal driving belt, that is to a belt trapezoidal-shaped in a crosssection perpendicular to its development, i.e.

longitudinal direction, and preferably having the form of an isosceles trapezium, intended to be coupled with at least a couple of pulleys, each of them provided with a groove, such as to form a drive; in particular, the driving belt according to the present invention is especially fit for obtaining those drives known under the name of speed variators.

Different types of trapezoidal driving belts are known and such known trapezoidal driving belts show several inconveniences.

One of the principal inconveniences of the known trapezoidal driving belts consists in their incapacity of transmitting high powers with the drives which employ them.

Another inconvenience of the known trapezoidal driving belts is that their lifetime decreases with the increasing of the power transmitted and, so, to be able to guarantee a long useful lifetime to the belt the transmittable power of the drives which employ them is considerably limited.

The present invention aims at providing a trapezoidal driving belt capable of transmitting high powers, giving at the same time a long lifetime for the belt.

Accordingly the present invention provides a trapezoidal driving belt comprising a body of elastomeric or plastic material embedding a tension resistant insert formed by a plurality of flexible and inextensible threads or cords parallel and coplanar to one another characterised by the fact of comprising, embedded in the body of the belt, at least a continuous longitudinally-extending member, rigid in a direction transverse to the longitudinal axis of the belt and flexible in the direction of the longitudinal axis of the belt.

The present invention will be better understood from the following detailed description, by way of example and therefore not limitative, with reference made to the figures of the enclosed drawing sheet, in which: Figure 1 shows in perspective view and in transverse cross-section a portion of a belt according to the invention; Figure 2 shows a perspective view and in transverse cross-section a portion of a belt according to another embodiment of the invention; Figure 3 shows in perspective view and in transverse cross-section a portion of a belt according to a further embodiment of the invention; Figure 4 shows in perspective view a portion of a component part of a belt according to one embodiment of the invention;; Figure 5 shows in perspective view a portion of a component part according to a further embodiment of the invention Figure 6 shows in perspective view a portion of a component part of a belt according to another embodiment of the invention; Figure 7 shows in perspective view a portion of a component part of a belt according to a still further embodiment of the invention.

A portion of a driving belt according to the invention is shown in Figure 1.

As can be seen in Figure 1 a belt according to the present invention comprises a body 1 of the belt in elastomeric or plastic material, trapezium-shaped in a cross-section perpendicular to the longitudinal axis of the belt and, particularly, having the form of an isosceles trapezium. The body of the belt shows, therefore, a minor base 2, a major base 3 and two sides 4 and 5.

A tension resistant insert formed by a plurality of cords 6 parallel and coplanar to one another of flexible, inextensible material, for example of steel, nylon, glass-fibre, polyamide fibres, aromatic polyamide fibres, polyester material, rayon and the like, is embedded within the body of the belt.

In one embodiment of the invention a continuous longitudinally-extending member which shows a high rigidity, that is at least three times the rigidity of the elastomeric material, under the action of stresses transversely directed to the belt and a high flexibility, that is a flexi biiity equal to the elastomeric material in the direction of the longitudinal axis of the belt itself, is embedded within the body 1 of the belt in elastomeric material.

More in particular, the above-mentioned continuous member is situated within the part of the belt subjected to compressive stresses during the working, so that the barycentre of each section of the member corresponds to the barycentre of the part of the belt subjected to compressive stresses during the working and so that the lateral dimensions of said member are, in their direction perpendicular to the bases, greater than a half of the corresponding dimension of the compressed portion of the belt and in their direction parallel to the bases, greater than 0.3 times the width of the said compressed portion of the belt.

As can be seen in the embodiment represented in Figure 1 a continuous member 7 formed by a helicoid of diameter included between 4 and 40 mm of metallic material thread of diameter included between 0.3 and 2 mm is embedded in the body of the belt.

In Figure 2 is shown a portion of a belt according to an alternative embodiment of the invention.

As can be seen in Figure 2 the trapezoidal driving belt includes a body in elastomeric material having the form of an isosceles trapezium in a cross-section perpendicular to the longitudinal axis of the belt. The body of the belt shows, therefore, a major base 9, a minor base 10 and two sides 11 and 12 on which there is a layer or elastomeric material charged with cut-down sizes of textile material fibres such as, for instance, rayon, glass, aromatic polyamide, cellulose and the like. Alternatively, as a substitute for the layer of elastomeric material charged with cut-down sizes of textile material fibres, may be used a rubberised woven fabric and in this case said rubberised woven fabric can advantageously cover, besides the sides of the belt, also the major and minor base of the same.

A tension-resistant insert formed by a plurality of cords 14, coplanar and parallel to one another, of flexible and inextensible material as one of the previously mentioned materials, is embedded within the body of the belt.

Still within the body of the belt is also embedded a continuous member 15, rigid under the action of stresses transversely directed to the belt and highly flexible in the direction of the longitudinal axis of the belt. In particular, as can be seen in Figure 2 the member 15 consists of a helicoid of steel strip with a width included between 0.8 and 15 mm and with a thickness included between 0.1 and lmm wherein a coil has substantially the form of an isosceles trapezium with the sides parallel to the belt ones.

For the manufacture of belts according to the embodiment of the invention represented in Figures 1 and 2 many manufacturing methods are possible.

In particular, and only by way of example, at first with the continuous member may be manufactured a tubular body, so that said member is coated with uncured or semivulcanised rubber at least on its outer surface.

Then, the tubular body is put into a mould of already known type for the manufacture of belts together with the other component parts of the belt and some elastomeric material is injected in the mould and vulcanised in the said mould.

In particular, during the vulcanisation warm air or vapour under pressure can be sent, with already known techniques, within the cavity of the tubular body.

In Figure 3 is represented a belt according to a further embodiment of the invention.

As can be seen in Figure 3 the belt comprises a belt body 16 is elastomeric or plastic material trapezoidal-shaped in a cross-section perpendicular to the longitudinal axis of the belt. The body of the belt shows therefore a major base 17, a minor base 18 and two sides 19 on which there is a layer 20 of elastomeric material charged with cut-down sizes of textile material fibres as the previously mentioned ones and, in alternative, a layer of rubberised woven fabric with which also the bases of the said belt can be advantageously covered.

A tension-resistant insert formed by a plurality of cords 21 coplanar and parallel to one another of flexible and inextensible material as previously mentioned is embedded within the body of the belt.

Furthermore, still within the body of the belt is embedded a continuous member 22, rigid under the action of stresses transversely directed to the belt and highly flexible in the direction of the longitudinal axis of the belt.

In particular, the member 22 consists of a helicoid of steel wire and within the member 22 is inserted a body 23 of a mix of low hysteresis elastomeric material.

As a mix of low hysteresis elastomeric material can be used, only by way of example, the following: Parts by Weight natural and/or styrenic 100 rubber large particle carbon black 70 zinc oxide 5 stearic acid 2 sulphur 2.5 to 1.5 accelerators 0.5 to 2 anti-agers 1 to 2 plasticisers 2 to 4 In the previously described embodiments it has been said that the body of the belts consists of a mix of elastomeric material and only by way of example we shall indicate here below a suitable mix of elastomeric material for the said body of the belt:: Parts by Weight natural rubber 100 large particle carbon black from 50 to 100 zinc oxide 5 stearic acid 2 sulphur 2.5 accelerators 1 to 2 anti-agers 1 to 2 As previously said the most general idea of a trapezoidal driving belt according to the invention consists in the presence within the body of the belt of a continuous longitudinallyextend- ing member having the characteristics of being extremely rigid and, therefore, not subjected to deformation under the action of stresses applied in the transverse direction perpendicular to the belt and, in particular, in directions incident on the sides of the belt and of being extremely flexible in the direction of the longitudinal axis of the belt.

Any type of continuous member having the above said characteristics is to be considered included in the range of the present invention.

In Figures 4, 5, 6 and 7 are illustrated some types of continuous longitudinallyextending members employable in a belt according to the invention.

As can be seen in Figure 4 the continuous member represented in it consists of a tubular body 24 of a metallic or of a high hardness plastic material, that is of a hardness equal to at least three times the hardness of the elastomeric material forming the body of the belt, having the form of an isosceles trapezium in a cross-section perpendicular to the longitudinal axis of the member wherein are made notches 25 each of them including the minor base 26, the sides 27 and 28 and part of the major base 29.

In Figure 5 is represented another embodiment of the invention for a continuous member employable in a belt according to the pIesent invention.

As can be seen in Figure 5 the member 30 represented in it is a member obtained by means of folding a steel wire 31 so as to originate a series of loops having the form of an isosceles trapezium opened in correspondence to the major base.

In Figure 6 is represented a further embodiment of the invention of a member employable in a belt according to the present invention.

As can be seen in Figure 6 the member 32 represented in it is obtained by means of folding a steel strip 33 so as to originate a plurality of segments 34 having the form of an isosceles trapezium without its major base. Said segments 34 are connected to one another, alternately, by portions 35.

In Figure 7 is represented another embodiment of a continuous member employable in a belt according to the present invention.

As can be seen in Figure 7 the member 36 represented in it consists of a strip having a crenellated form, which is disposed within the body of the belt, so that the portions 37 of said member 36 parallel to one another and to the longitudinal axis of the member are turned towards the sides of the belt.

As previously said the continuous members are embedded within the body of the belt which is, as previously said, of elastomeric or plastic material and said member may or may not be connected to the elastomeric or plastic material of the belt. In the case in which the member is connected to the elastomeric or plastic material forming the body of the belt the connection can be obtained in a way already known by a technician of this field, coating said member with a mix for direct bonding such as, for example, a natural rubber of the same type as the previously mentioned one.

From the description of the embodiments of a trapezoidal driving belt and from the considerations indicated here below it may be easily understood that the objects proposed and previously mentioned can be reached.

As previously said a trapezoidal driving belt is intended to work with at least a couple of pulleys each of them provided with a groove along its revolution surface.

The belt is set on two pulleys and is inserted in the grooves of the latter.

The contact between the belt and the pulley grooves happens between the sides of the belt and the lateral surfaces of the pulley grooves and the transmission of the motion from a pulley to the other by means of the belt is effected by means of the friction existing between the sides of the belt and the lateral surfaces of the pulley grooves.

In order to be able to transmit the motion from a pulley to the other the belt must not slip within the pulley grooves and therefore, when increasing the power to be transmitted it is necessary to increase the pressure exercised between the sides of the belt and the pulley grooves. The presence within the body of a belt according to the invention of a continuous longitudinally-extending member rigid in the transverse direction perpendicular to the major dimension of the belt and therefore not subjected to deformation permits a considerable increase in the pressure between the sides of the belt and likewise the transmittable power or a belt according to the invention allowing even the transmission of powers that are twice the power transmittable under the same conditions with the trapezoidal belts of the known type.

Said continuous member allows the belt accord ing to the invention to have a high and uniform flexibility along the whole belt so as to achieve a very good resistance to fatigue and to reduce the energy dissipated through the hysteresis due to the flexion of the belt itself.

Moreover, reducing enormously the possibility of slipping between the sides of the belt and the lateral surfaces of the pulley grooves a considerable increase of the lifetime of the trap ezoidal belts according to the invention can be obtained.

WHAT WE CLAIM IS:-.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. large particle carbon black from 50 to 100 zinc oxide 5 stearic acid 2 sulphur 2.5 accelerators 1 to 2 anti-agers 1 to 2 As previously said the most general idea of a trapezoidal driving belt according to the invention consists in the presence within the body of the belt of a continuous longitudinallyextend- ing member having the characteristics of being extremely rigid and, therefore, not subjected to deformation under the action of stresses applied in the transverse direction perpendicular to the belt and, in particular, in directions incident on the sides of the belt and of being extremely flexible in the direction of the longitudinal axis of the belt. Any type of continuous member having the above said characteristics is to be considered included in the range of the present invention. In Figures 4, 5, 6 and 7 are illustrated some types of continuous longitudinallyextending members employable in a belt according to the invention. As can be seen in Figure 4 the continuous member represented in it consists of a tubular body 24 of a metallic or of a high hardness plastic material, that is of a hardness equal to at least three times the hardness of the elastomeric material forming the body of the belt, having the form of an isosceles trapezium in a cross-section perpendicular to the longitudinal axis of the member wherein are made notches 25 each of them including the minor base 26, the sides 27 and 28 and part of the major base 29. In Figure 5 is represented another embodiment of the invention for a continuous member employable in a belt according to the pIesent invention. As can be seen in Figure 5 the member 30 represented in it is a member obtained by means of folding a steel wire 31 so as to originate a series of loops having the form of an isosceles trapezium opened in correspondence to the major base. In Figure 6 is represented a further embodiment of the invention of a member employable in a belt according to the present invention. As can be seen in Figure 6 the member 32 represented in it is obtained by means of folding a steel strip 33 so as to originate a plurality of segments 34 having the form of an isosceles trapezium without its major base. Said segments 34 are connected to one another, alternately, by portions 35. In Figure 7 is represented another embodiment of a continuous member employable in a belt according to the present invention. As can be seen in Figure 7 the member 36 represented in it consists of a strip having a crenellated form, which is disposed within the body of the belt, so that the portions 37 of said member 36 parallel to one another and to the longitudinal axis of the member are turned towards the sides of the belt. As previously said the continuous members are embedded within the body of the belt which is, as previously said, of elastomeric or plastic material and said member may or may not be connected to the elastomeric or plastic material of the belt. In the case in which the member is connected to the elastomeric or plastic material forming the body of the belt the connection can be obtained in a way already known by a technician of this field, coating said member with a mix for direct bonding such as, for example, a natural rubber of the same type as the previously mentioned one. From the description of the embodiments of a trapezoidal driving belt and from the considerations indicated here below it may be easily understood that the objects proposed and previously mentioned can be reached. As previously said a trapezoidal driving belt is intended to work with at least a couple of pulleys each of them provided with a groove along its revolution surface. The belt is set on two pulleys and is inserted in the grooves of the latter. The contact between the belt and the pulley grooves happens between the sides of the belt and the lateral surfaces of the pulley grooves and the transmission of the motion from a pulley to the other by means of the belt is effected by means of the friction existing between the sides of the belt and the lateral surfaces of the pulley grooves. In order to be able to transmit the motion from a pulley to the other the belt must not slip within the pulley grooves and therefore, when increasing the power to be transmitted it is necessary to increase the pressure exercised between the sides of the belt and the pulley grooves. The presence within the body of a belt according to the invention of a continuous longitudinally-extending member rigid in the transverse direction perpendicular to the major dimension of the belt and therefore not subjected to deformation permits a considerable increase in the pressure between the sides of the belt and likewise the transmittable power or a belt according to the invention allowing even the transmission of powers that are twice the power transmittable under the same conditions with the trapezoidal belts of the known type. Said continuous member allows the belt accord ing to the invention to have a high and uniform flexibility along the whole belt so as to achieve a very good resistance to fatigue and to reduce the energy dissipated through the hysteresis due to the flexion of the belt itself. Moreover, reducing enormously the possibility of slipping between the sides of the belt and the lateral surfaces of the pulley grooves a considerable increase of the lifetime of the trap ezoidal belts according to the invention can be obtained. WHAT WE CLAIM IS:-.

1. A trapezoidal driving belt comprising a

body of elastomeric or plastic material embedding a tension-resistant insert formed by a plurality of flexible and inextensible threads or cords parallel and coplanar to one another and having embedded in the body of the belt, at least a continuous longitudinallyextending member, rigid in a direction transverse to the longitudinal axis of the belt and flexible in the direction of the longitudinal axis of the belt.

2. A belt according to Claim 1, in which the continuous longitudinallyextending member is a hollow profile.

3. A belt according to Claim 2, in which the cavity of the continuous longitudinallyextend- ing member is filled with low hysteresis elastomeric material.

4. A belt according to Claim 3, in which the elastomeric material filling the cavity of the continuous longitudinallyextending member has a natural rubber base.

5. A belt according to any of the previous claims, in which there is on the sides a layer of elastomeric material charged with textile material fibres.

6. A belt according to any one of the preceding claims, in which the continuous longitudinally-extending member consists of a helicoid of wire where every loop has substantially the form of an isosceles trapezium.

7. A belt according to any one of Claims 1 to 5, in which the continuous longitudinallyextending member consists of a helicoid of wire where every loop has circular form.

8. A belt according to any of the Claims from 1 to 5, in which the continuous longitudinally-extending member is a tubular profile provided with partial notches on its surface.

9. A belt according to any of the Claims from 1 to 5, in which the continuous longitudinally-extending member is a substantially sinusoidal profile being, moreover, zig-zagshaped.

10. A belt according to any of the Claims from 1 to 5, in which the continuous longitudinally-extending member consists of a strip having a crenellated form.

11. A driving belt substantially as hereinbefore described with reference to and as illustrated in Figure 1, 2 or 3 of the accompanying drawings.

12. A driving belt substantially as hereinbefore described with reference to and as illustratedin Figure 4, 5, 6 or 7 of the accompanying drawings.