FI68454C - TRANSMISSIONSSYSTEM MED EN KUGGFOERSEDD REMSKIVA OCH EN FLEXIBEL KUGGFOERSEDD REM - Google Patents

Description

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C (45) Patent filed 10 09 1935 Patent aeddolat »(51) Kv.lk.4 / int.a.4 F 16 H 55/08, F 16 G 1/28 i FINLAND - · FINLAND (21) Patent application - Patentansöfcnlng 78391 1 (22) Application date - Ansöknlngsdag 19.12.78 (F ») (23) Starting date - Giltlghetsdag 19.12.78 (41) Has become public - Blivit offentllg 2i | 06.79

National Board of Patents and Registration of Finland Date of publication and date of publication. - i Qj- or

Patents and Registration in the United States of America and in the Public Administration 7 '3 * -7 (32) (33) (31) Privilege claimed - Begärd priority 23.12.77 USA (US) 8640A5 (71) Uniroyal, Inc., 1230 Avenue of the Americas, New York, NY 10020, USA (72) Frank Leonard Wujick, New Haven, Connecticut, USA (7k) Berggren Oy Ab (5A) Transmission system with toothed pulley and flexible toothed belt - Transmissionssystem med en kuggförsedd remskiva och en flexibel kuggförsedd rem This invention relates to a transmission system comprising a toothed pulley and a flexible toothed belt.

U.S. Pat. No. 2,507,852 discloses a transmission belt comprising an inextensible traction member having teeth and a protective sheath fabric covering the teeth attached to one side. The teeth are preferably made of an elastomeric material, such as rubber, and the belt may further comprise a support layer of the same or similar material as that from which the teeth are constructed.

Many different elastomeric materials have been used to construct the belts of U.S. Patent 2,507,852, the most common of which are e.g. neoprene and polyurethane. These belts are designed to interleave with toothed pulleys constructed of a material with a higher Young’s modulus than the elastomeric material used to construct the belt. A conventional toothed belt, as described in U.S. Patent 2,507,852, uses a cross-sectional shape of the tooth that is substantially trapezoidal in shape and quite similar to a conventional rack tooth. Many attempts have been made to change the shape of the belt and pulley teeth to alleviate the problem of belt breakage.

2 68454 With such trapezoidal toothed belts, the usual breakage is the tooth shearing due to the concentration of the load. With a view to reducing tooth leikkautumisten U.S. Patent No. 3 756 091 is described a belt tooth having a cross-sectional shape approximating to the rated load determined under the belt tooth isochrome half the magnitude of the rim contour. The pulley grooves of U.S. Patent 3,756,091 are paired with the belt teeth and substantially conjugate thereto. A belt with substantially arcuate teeth according to U.S. Patent 3,756,091 reduced the shear load on the belt teeth and increased energy transfer capacity.

One break in the belt shape according to U.S. Pat. No. 3,756,091 may occur due to wear of the spacers in the belt, especially when used with small diameter pulleys. The space wear between the belt teeth is due to the abrasion of the protective layer and the exposure of the traction member due to the action of the pulley tooth against the belt. This interstitial wear results in premature fracture due to detachment of the teeth from the traction member and / or rupture of the traction member.

U.S. Patent 4,037,485 proposes a solution to the wear problem of intermediate spaces. As described in U.S. Patent 4,037,485, the aspect ratio of the belt teeth and grooves and the pulley teeth and grooves is such that at the belt length dimension between the pulleys, the height of the belt teeth is greater than the depth of the belt grooves outwardly of the belt pulleys. the parts in contact with the parts of the toothed pulley which form the bases of the pulley grooves. At the same time, U.S. Patent 4,037,485 explains that the belt teeth are compressed so that their height is reduced so that the radially outermost portions of the pulley teeth come into contact with the portions of the belt located between the belt teeth and forming the bases of the belt grooves.

Relatively early, during the life of the toothed transmission belt and pulley described in U.S. Patent 4,037,485, the pressing contact of the elastomeric teeth against the bases of the pulley grooves causes a substantially permanent deformation of the pulley. This deformation accelerates at the high operating temperatures found in 3,684 5 4 motor vehicle applications. The deformation causes a significant, permanent decrease in tooth height. The deformed tooth no longer supports the traction member as desired in U.S. Patent 4,037,485. Thereafter, the toothed belt and pulley drive of U.S. Patent 4,037,485 develops the same wear pattern as the toothed transmission device of U.S. Patent 3,756,091.

According to the present invention, it has been found that the wear problem at the spacers of U.S. Patents 3,756,091 and 4,037,485 can be greatly alleviated. This relief causes an increase in the service life of the toothed belt. The service life of the dental transmission belt according to the present invention is even longer even in harsh operating conditions such as high temperatures and rotational vibration environments. This improvement is most useful when using small pulleys.

The present invention is directed to a transmission system comprising a pulley for use with a flexible toothed belt as described in U.S. Patent 3,756,091. The features of the transmission system according to the invention are set out in the appended claims.

Terms used in this specification to describe the features of the present invention are defined in U.S. Patent 3,756,091.

The present invention alleviates the problem of wear between the tooth spaces between the belt teeth by changing the shape of the pulley so that the contact area of the tooth tips of the pulley and the space between the belt teeth is reduced. In addition, it relieves pressure in the intermediate area of the pulley by providing support to the pulley in the pulley groove. The pulley of the present invention has a non-conjugate shape with respect to the belt. Each pulley groove is formed by a substantially circular arc connecting the tips of adjacent pulley teeth. As the belt passes around the pulley, the belt teeth are in pressure contact with the groove of the pulley. The longitudinal cross-sectional line of the tip of each pulley tooth is generally as described in U.S. Patent 3,756,091 and consists in part of two substantially circular arcs with centers of curvature offset from each other. Of these, the center of curvature is located on the same side of each tooth tip as the corresponding arc. The tip arches of the tooth are 4 68454 connected by a line portion which is substantially straight or slightly curved. This line portion determines the width of the tip of the pulley tooth.

According to the present invention, the surface contact ratio of the width of the belt tooth to this line portion is between 20: 1 and 1: 1. The length of this line section is between 5 and 100% of the width of the belt tooth of the belt with which the pulley is to be used, and preferably between 6 and 33% of the width of the belt tooth.

Both the compression contact of the pulley tooth with the pulley groove and the surface contact ratio defined above have an individual effect on the space wear in the belt. Together, however, as explained in more detail below, they reduce the space consumption on the belt to a greater extent than the sum of their individual effects.

The invention is explained in more detail below in connection with the accompanying drawing, in which:

Fig. 1 is a longitudinal sectional view seen in a transverse view of a preferred embodiment of the cooperating pulley wheels of the present invention interleaving with the belt so as to form a forced drive system; Fig. 2 is an enlarged longitudinal partial sectional view of a pulley according to said preferred embodiment; Fig. 3 is an enlarged longitudinal fragmentary sectional view of the pulley of Fig. 2 superimposed on the pulley view of the corresponding conjugate of U.S. Patent 3,756,091; , in no - load condition.

As shown in Fig. 1, the endless belt 10 is in contact with the drive pulley 11 and the driven pulley 12. The belt 10 is provided with a traction member 13 comprising a plurality of turns of continuous filament filament. The traction member 13 supports substantially the entire working load applied to the belt 10 and up to the maximum load for which the belt is designed, the traction member 13 is substantially inextensible. The aforementioned U.S. Patents 2,507,852 and 3,756,091 provide a more detailed description of the principles of this general class of toothed belt and belt belt systems. The entire contents of U.S. Patents 2,507,852 and 3,756,091 are hereby incorporated by reference. The belt further includes a backing layer 14 and a protective sheath (not shown) that extends over the entire toothed surface. A thin layer of elastomer or other material (not shown) may be added between the sheath and the traction member 13 to improve the adhesion of the intermediate areas of the belt. The belt may be made in many different ways, but preferably the method described in U.S. Patent 3,078,206, the entire contents of which are incorporated herein by reference, is used. An alternative method of preparation is described in the aforementioned U.S. Patent 2,507,852.

As shown in Figure 2, the pulleys 11 and 12 of Figure 1 each comprise a body portion 20 having arcuate teeth 21 separated by arcuate notches 22. The tooth tip 23, seen in a longitudinal cross-section, has a contour shape consisting of two circular arcs 24 and 25, the centers of curvature 26 and 27 of which are offset relative to each other also with respect to the center line 28 of the tooth tip. The centers of curvature 26 and 27 of the radii 29 and 30 of the arcs 24 and 25 displaced relative to each other are offset by equally long distances on opposite sides of the centerline 28 of the tooth 21, but on the same sides as their respective arcs. Both centers of curvature are inside the pulley tooth. The non-intersecting arcs 24 and 25 are connected by a line portion 31. The arc 24 extends from point A to point B. The arc 25 extends from point C to point D. The centers 26 and 27 are equidistant from the tangent to the outer diameter of the pulley. on opposite sides of the center line 28 and equidistant radial distances from the center of the pulley. The line portion 31 is part of a circular arc drawn from a center located at an extension of the centerline 28. The center of curvature of line 31 may be on centerline 28, i. inside the pulley body. Alternatively, the center of curvature of the line portion 31 may be on an extension of the centerline 28 that is outside the pulley body. The line portion 31 is shown as a straight line, but may be concave or convex with respect to the pulley body.

Figure 3 shows an enlarged longitudinal sectional view of the pulley of Figure 2 superimposed with the pulley view of the conjugate of the corresponding U.S. Patent 3,756,091. This figure highlights the difference in the longitudinal sectional profiles of the respective pulley grooves and teeth. Figure 3 shows a groove profile 22 according to the invention consisting of an arc having a radius of 32 and a center of curvature at 33. The arcs 23 and 25, which in part form the tip of a pulley tooth according to the invention, are drawn with radii 29 and 30 having centers of curvature at 26 and 27. , which forms the outermost part of the tooth tip and connects the arcs 24 and 25, is, according to the invention, as long as the distance between points B and C. The arc forming the groove 22 may intersect the arcs 24 and 25 of the invention at points A and B.

Instead, the groove 41 of the conjugate pulley of U.S. Patent 3,756,091 is formed by an arc having a radius of 40 and a center of curvature at 39. The arcs 46 and 47, which partially form the tip of the pulley tooth of U.S. Pat. No. 3,756,091, are drawn with radii 44 and 45, the centers of curvature of which are at 42 and 43, respectively. The groove-forming arc 41 intersects the arcs 46 and 47 at points G and H.

The length of the line portion BC of the present invention is greater than the length of the line portion EF of the pulley tooth of U.S. Patent 3,756,091. According to the present invention, the centers of curvature 26 and 27 are offset on opposite sides of the centerline 28 by a longer distance than the centers of curvature 42 and 43 of the pulley tooth tip of U.S. Patent 3,756,091. The shaded area 48 represents the additive compared to the corresponding profile of U.S. Patent 3,756,091.

Fig. 4 is an enlarged longitudinal partial sectional view of the pulley of Fig. 2 in pairing with a belt constructed in accordance with U.S. Patent 3,756,091 in an unloaded condition. In longitudinal section, each tooth 49 of the belt 50 consists of two circular arcs 51 and 52, whose equally long radii 53 and 54 intersect at a point 55 on the centerline 34. The centers of curvature 56 and 57 from which the arcs 51 and 52 are drawn are offset on opposite sides of the centerline 34 68454 7 corresponding arcs, an amount generally equal to or less than 10% of the radius of curvature of arcs 51 and 52.

The depth of the groove between the adjacent pulley teeth of the pulley according to the invention is less than the depth of the groove of the conjugate pulley and thus less than the depth of the pulley tooth. This is clearly seen in Figure 4, in which the tip of the belt tooth is shown to overlap with the bottom of the pulley groove. Of course, this is not the case in practice, but the belt tooth has to change shape due to its contact with the pulley groove. The depth of the pulley groove is preferably 1-15% less than the depth of the pulley tooth.

When designing the drive according to the invention, in addition to the aspects already described above, it is desirable that the ratio of the width of the belt tooth (the width represented by the dashed line 59 between points J and K in Fig. 4) and the length of the line portion 31 (line BC in Fig. 2) is 20: 1 and Between 1: 1 and preferably between 15: 1 and 3: 1.

The radius 32 of the cross-sectional profile of the groove 22 is much larger than the radius 29 and 30 and its center 33 is outside the pulley body, on the center line 34. The centers of the radii 26, 27 and 33 are on the same circle or at short distances on circles 35 and 36 concentric with the teeth. the outermost line portions 31 of the tips with the connecting circle and located inside it. Circles 35 and 36 are radially spaced from this circle equal to or less than 30% of the total depth of the tooth. The total depth of the tooth is at the intersection of the line portion 31 and the centerline 28, i. the radial distance between the point located at the apex circle 37 and the circle connecting the innermost points of the groove 22. The innermost point of the groove 22 is at the point of intersection of the arc drawn by radius 32 and the centerline 34, i. at a point on the root circle 38.

The groove profile 22 is formed by a circular arc having a radius of 32 and a center at 33 on the centerline 34. The arc forming the groove 22 may intersect the arc 24 on the other side of the profile pulley groove and the arc 25 on the opposite side of this profile. mainly with the adjacent 68454 8 tooth repeating around the circumference of the pulley to form other teeth and grooves.

The total depth of the pulley groove is equal to the distance measured along the center line 34 between the points of intersection of the apex circle 37 of this line 34 and the root circle 38. As shown in Figure 2, the total depth of the pulley groove is the sum of the length and distance d of the beam 32. Preferably, the total depth of the pulley groove is not more than 15% less than the depth of the pulley tooth interlocking with this pulley groove. As a result, the belt harness is subjected to compression sealing with the groove 22. Alternatively, the aspect ratio of the pulley groove depth and the pulley tooth depth may be as described in U.S. Patent 3,756,091.

When designing the shape of the pulley groove and tooth, care should be taken to ensure that the arc forming the groove 22 smoothly joins the arcs 24 and 25. However, in order to provide a smooth transition from the groove 22 to the arc 24 or 25 forming part of the pulley tooth tip, it may be desirable to use an association dash. This association line may be similar to the line portion 31.

Example

The following procedure was followed to compare powertrains with pulleys with dimensions in accordance with the present invention with pulleys with conventional dimensions. Several forced or synchronous drive belt samples were prepared by conventional methods, using conventional materials known in the art. All belts were made from a neoprene-rubber blend with a nylon fabric against the belt teeth and included a traction member consisting of fiberglass braids located substantially at the root line of the belt teeth. After fabrication, the belt samples were dynamically tested with pulleys of appropriate dimensions and shape as described below.

Three transmission systems were tested. These combinations were denoted by the letters A, B and C:

Combination A comprised belts and pulleys made exactly according to U.S. Patent 3,756,091. These belts and pulleys are sold commercially under the tradename UNIROYAL, Inc. in 8mm pitch Powergrip 9 HTD pulley and pulley system shears. 6,8454

The dimensions of the eight belt samples prepared were as follows, measured in the longitudinal section between the pulleys: spacing between the belt teeth 8 mm; belt tooth width 6.6 mm; belt tooth spacing 1.4 mm; and a tooth depth of 3.4 mm. The width of the belts was 15 mm and the dividing line length was 936 mm.

The sprockets had a tooth depth of 3.6 mm and were substantially conjugate with the sprockets. As described in U.S. Patent 3,756,091, the longitudinal sectional outline of the tooth tips consisted of two circular arcs connected by a line portion. The length of the line section was 0.3 mm. In the transmission system thus obtained, the line was 4.2% of the width of the belt tooth.

Combination B comprised a transmission system that was otherwise completely similar to Combination A except that the depth of the belt tooth was increased by 0.3 mm (8.9%) to 3.5 mm. This corresponds to the teachings of U.S. Patent 4,037,485. Seven belt samples were made.

Combination C comprised a transmission system according to the present invention. The dimensions of the belt were the same as in combination A. The depth of the helical tooth was 3.3 mm; the radius of curvature of the belt groove was 2.7 mm. The length of the line section was 0.5 mm.

Table 1 compares the main dimensions of combinations A, B, and C and the resulting tooth compression.

Table I

combinations

ABC

Belt tooth width, mm 6.6 6.6 6.6

Depth of belt tooth, mm 3.4 3.7 3.4

Depth of pulley tooth, mm 3.6 3.6 3.3

Length of line section, mm 2.8 2.8 0.5

Length of line section in% 4.2% 4.2% 7.7% (of the width of the belt tooth)

Pulley tooth compression 0% 3.4% 3.7% (belt tooth depth - pulley tooth depth) pulley tooth depth 10 68454

Each belt sample was mounted on a dead weight bending tester with a two-wheel fit consisting of a driving and driven pulley, each with a diameter of 54.9 mm. The drive pulley was driven at 350 rpm so that a force of about 1100 N was applied between the center lines of the pulleys. The test was performed at room temperature. The test was continued until fracture, unless otherwise noted. The time to breakage to the nearest hour for each group of belt samples is shown in Table II.

Table II Duration in test, h Ä B C

83.4 59.0 298.4 (the test was stopped) 46.9 117.2 690.7 65.5 99.1 187.6 75.7 120.8 233.4 54.2_258.5

Average value of 6 5.1 99.0 34 5.1

The test was repeated in an ambient chamber maintained at 88 ° C. The results are shown in Table III.

Table III Duration in test, h AB C

93.0 118.2 196.2 87.9 98.5 105.7 82.0 117.5 129.3 103.4_171.8

The average value of 91.6 111.4 162.0

The results shown in Tables II and III clearly show that the combination of pulleys and belt f / C, in which the ratio of pulley to belt is in accordance with the present invention, gave a significantly longer belt life than combinations A and B. This improvement was seen in both room temperature and accelerated tests. In tests performed at temperatures of 88 ° C.

11 68454

The only significant variable in these comparative experiments was the ratio of pulley dimensions to belt dimensions. In combination B, the depth of the belt teeth was greater than the depth of the corresponding pulley grooves. In combination C, the depth of the pulley teeth was also greater than the depth of the corresponding pulley grooves. However, the length of the line portion of Combination C was substantially greater than the lengths of the line portion on the pulleys of Combination A or Combination B. In the pulleys of the previously known combinations A and B, the lengths of the line section were insufficient, exposing the belt to excessive strain on the traction members. This excessive strain caused the belt to wear between the belt teeth and the breakage was mainly caused by excessive wear in this area.

In the pulleys of the combination C, the length of the line section was sufficient to distribute the load over a larger area and thus to reduce the stress in the areas between the belt teeth. As a result, wear in the interdental belt areas was reduced and belt life was significantly increased at both room temperature and elevated temperature.

The pulley described above can be used with toothed belts other than the toothed belts of U.S. Patent Nos. 2,057,852, 3,756,091 and 4,037,485. The teeth of the belt in question may be trapezoidal, arcuate or wedge-shaped, or their shape may consist of a combination or modification of these profile shapes. The belt may also have teeth on both sides of the traction member.

Claims (8)

12 Claims 6 8 4 5 4 A transmission system comprising a toothed pulley (11 or 12) and a flexible toothed belt (10), the pulley teeth (21) comprising tip portions connected by tooth spaces (22), each of the tip portions each having a longitudinal shear contour consisting essentially of two a circular arc (24, 25) with the centers of curvature (26, 27) offset relative to each other so that the center of curvature of each arc is on the same side of the tooth center line (28) as the corresponding arc, and a line segment connecting the arcs (31), characterized in that the length of the line segment (31) is 6-33% of the width of the belt tooth (49), and that the distance between the outermost part of the pulley tooth (21) tip and the innermost part of the tooth gap (22) is less than the depth of the belt tooth (49). Transmission system according to Claim 1, characterized in that the line segment (31) of the pulley tooth (21) is an arc of a circle having a radius equal to the distance between the outermost part of the pulley tooth (21) and the center of the pulley. Transmission system according to Claim 1 or 2, characterized in that the curves (24, 25) of the tip part of the pulley tooth (21) are tangents to the line segment (31) of the tip part at their junctions with it. Transmission system according to Claim 1, characterized in that the line segment (31) of the tip part of the pulley tooth (21) is a straight line. Transmission system according to one of the preceding claims, characterized in that the longitudinal sectional contour of the tooth gap (22) of the pulley consists of a substantially circular arc. Transmission system according to one of the preceding claims, characterized in that the distance between the outermost part of the tip part of the pulley tooth (21) and the innermost part of the tooth gap (22) is at most 15% smaller than the depth of the pulley tooth (49). 13 68454 Transmission system according to one of the preceding claims, characterized in that the tooth gaps (22) of the pulley are non-conjugate with the belt teeth (49). Transmission system according to one of the preceding claims, characterized in that the belt teeth (49) are substantially arcuate in the longitudinal cutting contour.