Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H9/00—Gearings for conveying rotary motion with variable gear ratio, or for reversing rotary motion, by endless flexible members
  • F16H9/02—Gearings for conveying rotary motion with variable gear ratio, or for reversing rotary motion, by endless flexible members without members having orbital motion
  • F16H9/04—Gearings for conveying rotary motion with variable gear ratio, or for reversing rotary motion, by endless flexible members without members having orbital motion using belts, V-belts, or ropes
  • F16H9/12—Gearings for conveying rotary motion with variable gear ratio, or for reversing rotary motion, by endless flexible members without members having orbital motion using belts, V-belts, or ropes engaging a pulley built-up out of relatively axially-adjustable parts in which the belt engages the opposite flanges of the pulley directly without interposed belt-supporting members

Definitions

• the invention relates to V-belt drives, which includes two or more pulleys and a die cut type V-belt.
• the most typical adaptations are such drives and variators, where a reliable function and suitability to variable circum- 5 stances are preferred to a long wearing life of the belt.
• the invention will improve the function of the V-belt drive in particular at low running speeds of the belt, but besides the speed range can as well grow upwards.
• the basic idea of the invention is to make low grooves with round bottom onto the contact surfaces of pulleys.
• the teeth between the grooves can be sharp or rounded.
• the principal advantage gained by groovings is to improve efficiency and safety of the function.
• the Swedish patent application no 302545 and the US- patents 3730483 and 4093185 include compared with the former an additional insight, that the straight grooves can be inclined and it is possible to strengthen or reduce the sinking of the rope between the cones of pulley through selection of the direction of skewness.
• the Swedish patent application no 428677 (Uno Ekman 1982) and the US-patent 4151980 include further such a feature, that the teeth added or formed on the pulley cones can be shaped like a circle.
• the object of the arched form is however only to improve the grip of the cone surfaces on a rope, chain or round rod running between them. If these groovings were applied to V-belt pulleys, the function would despite of the arched form not be better compared with radially grooved cone pulleys_
• V-belt pulleys where contact surfaces have grooves or teeth arched in shape.
• the docu ⁇ ment DEPS 224180 from year 1910 includes a V-belt pulley, where identical halves are cut in such a manner, that they screw into one other.
• the boundary surfaces of the teeth are perpendicular closed screw surfaces, whose intersections on symmetrical cones are spirals, which are identical but inclined to opposite directions.
• a V-belt pulley where the contact surfaces are equipped with grooves having an exact form of the spiral of Archimedes, is introduced in the document DEPS 2324998.
• This invention is characterized by a small pitch of the spiral, pro round only ca a half of the height of the V-belt running on the pulley.
• the belief of the inventor, that a grooving like this would reduce vibrations of the belt, is based on the supposition, that the sliding 5 of the belt on the contact surfaces of pulleys would take place evenly in the whole contact sector. According to the newest investigations this theory is not valid.
• the spiral grooves according to the present invention 10 deviate from the afore described by such a manner that the spiral form is an involute or approaching it.
• the deviations from the involute forms are needful, because the belts can be made fully rigid against neither the tension nor the lateral compression.
• the needful devi- 15 ations are however so small, that they can be detected only by measuring devices, not by the eye.
• FIG. 1 diagrammatically shows a straight radial grooving on a cone pulley of a V-belt drive.
• Fig. 2 shows a spiral grooving, which is bent back ⁇ wards in relation to the rotation.
• Fig. 3 shows a spiral grooving bent forwards in 25 relation to the rotation.
• Fig. 4 diagrammatically shows the path of the belt and the variation of the tension force in a slow-running V-belt drive, where the wedge angle ⁇ of belt and pulleys is small.
• Figures 5 and 6 show cross sections of V-belts with a symmetric and an asymmetric profile.
• Fig. 7 diagrammatically shows an adjustable drive which generally lowers the rotation speed and the groovings on the contact surfaces on the pulleys, when 35 the wedge angle ⁇ is small.
• Fig. 8 shows an adjustable drive generally increasing the rotations speed, where the contact surface of driving pulley has two crossed groovings.
• Fig. 9 shows the cross section of a grooving where 5 the teeth between the grooves are sharp.
• Fig. 10 shows the cross section of a grooving with blunt teeth and Fig. 11 with rounded teeth.
• the basis of the invention is the observation, that 10 in the driving pulley where the wedge angle is small compared to the friction angle between the flanks of the V-belt and the contact surfaces of the pulley
• a static contact arch or rest angle (Ruhewinkel) is formed as well onto the arrival side ( ⁇ ) as onto the exit side (A 3 ).
• both afore mentioned torque losses can be reduced.
• a part of the power loss caused by the tangential slide is substituted by decreasing loss of torque, when the spiral form of the grooving is made slightly deviating from the involute towards the form of a logarithmic spiral.
• the spiral form for the grooving in the driving pulley shall deviate from the involute form to the opposite di ⁇ rection from the logarithmic spiral, so that the belt would have a possibility to shorten without sliding over the teeth of the groovings. Due to the deviation a force component is formed pushing the belt out from the nip between the contact surfaces and thus the rest angle A 3 is decreased or prevented from forming.
• the optimal spiral forms depend on the relations of the elastic properties of the V-belt against crosswise compression and lengthwise tension. It is a very complex and tiring task to find the right forms only by calcula ⁇ tions.
• the form In pulleys where the radius of the contact ring remains constant the form can be a circle tangent to the theoretical spiral and having the same radius. The desired deviation from the theoretical form can in these cases be achieved by a radial movement of the touch point.
• the optimal cross section profile of the grooving de ⁇ pends on how strong an influence is desired.
• a grooving with sharp teeth (Fig. 9) is the most effective, but wears the belt more than the grooving with blunt (Fig. 10) or round teeth (Fig. 11). If the V-belt drive is working in very dirty or icy environment, it can be beneficial to make two groovings crosswise to another onto some pulley of the drive.
• the additional grooving (P in Fig. 8) shall be rounded in 5 shape, lower and coarser-meshed than the proper grooving.
• the cross section of the V-belt is asymmetric (Fig. 6) the grooving on the pulley cone surfaces can also prevent the tendency of the belt to turn on its side or 10 upside_down when overloaded. That is achieved by making the directions of curvature or the inclination angles different on opposite cone surfaces or by leaving one of the surfaces smooth.

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• 1985
  • 1985-09-09 FI FI853430A patent/FI72378C/fi not_active IP Right Cessation
• 1986
  • 1986-09-08 EP EP86905302A patent/EP0269631B1/en not_active Expired
  • 1986-09-08 US US07/055,621 patent/US4810237A/en not_active Expired - Fee Related
  • 1986-09-08 WO PCT/FI1986/000095 patent/WO1987001425A1/en active IP Right Grant

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