GB2123159A - Low energy drive for dynamic balancer - Google Patents

Abstract

A low energy, low noise drive system for a dynamic wheel balancing machine uses soft, pliant, elastic drive belts to rotate the wheel while absorbing much mechanical noise of the system. <IMAGE>

Description

SPECIFICATION Low energy drive for dynamic balancer This invention pertains to dynamic balancing machines and more particularly to a low energy, low noise drive system for dynamically rotating a wheel and tire assembly to be balanced.

Heretofore, in dynamic balancing equipment for rotating a wheel and tire assembly to balance it, the wheel and tire assembly has typically been driven at a relatively high horsepower and rate, for example, on the order of one horsepower and 500 rpm in order to maintain an appropriate signal to noise ratio. It has been observedthatthe noiseofa drive system ofthe kind described needs to be less than the square root of the rotational speed to maintain the necessary ratio. It has further been observed that the signals from the system vary with the square of the speed ofthe wheel.

The practice in the past has been to rotate wheel and tire assemblies on dynamic drive systems at the relatively high speed noted above. It has now been discovered that much ofthe difficulty in obtaining an appropriate signal to noise ratio lies in the use of inelastic drive belts and external tensioning means acting thereon.

As disclosed herein a drive system for a dynamic balancing machine has been provided wherein the rotation of the wheel and tire assembly can be reduced to a relatively low and safe speed of rotation ofthe order of 200 rpm (i.e. approximately 40% of much present day equipment) so asto provide a numberof significant advantages. A drive system as disclosed can use a motor on the order of only one-sixth horsepower compared to the usual one horsepower motor now in use. This reduction in the speed of rotation and energy permits the elimination ofthe usual safety hood which normally is located overthe rotating wheel.Additionally, the use of collateral tensioning means acting againstthe belts has also been eliminated therebyfurther reducing the noise in the drive system and in the electronics, as well as the manufacturing cost. Finally, the drive system as disclosed herein has the advantage whereby the drive motor and supporting shaft of the wheel and tire assembly can be mounted on fixed centers at a predetermined spaced relation from each other.

In short, dynamic balancing machines ofthe kind described have heretofore employed an inelastic belt requiring tensioning means acting againstthe belt whereby a motor can rotate the drive shaft. Use of a strong drivesystem of this type is noisy. Thus, to achieve an appropriate signal-to-noise ratio the rotational speed has had to be increased. This, in turn, demands a larger motor, while the higher speed requires the use of a safety hood located over the high speed rotating wheel and tire assembly.

In general, in a dynamic wheel balancing machinea drive system has been provided for rotating a wheel and tire assembly wherein the system includes a drive shaft in which one end ofthe shaft is disposed and adapted to readily removably receive a wheel to be balanced. Bearing means serve to support the shaft for rotation. The drive shaft carries a pulley on one end for receiving a belt drive therearound. A motor driving a second pulley serves to rotate the wheel and tire assembly via the belt drive means trained about and extending between the first and second named pulleys. The belt means has a modulus of elasticity sufficientto provide substantially all tensioning ofthe belt means when trained about and between the pulleys whereby the two pulleys can be rotated on fixed centers.Preferably, the belt means includes a plurality of belts disposed side by side, each belt being characterized by such modulus of elasticity.

Generally, the present invention provides an improved drive system for dynamic wheel balancing machines by providing a low energy, low noise drive system for such a machine whereby the rate of rotation ofthewheel and tire to be balanced can be sufficiently reduced to permit removal of the safety hood as well as the useofa significantlysmallerand lower powered drive motor.

Thesinglefigure of the drawing shows a diagrammatic perspective view with portions broken away of a drive system according to the invention.

Adynamicwheel balancing machine 10 carries a bearing housing assembly 15 including an elongate drive shaft 11 and bearing means such as the bearing block assemblies 12, 13 supporting shaft 11 for rotation. One end of shaft 11 is disposed and adapted to readily removably receive a wheel and tire assembly 14to be balanced.

Suitable sensor elements 16,18 paired with passive supports 17, 19 carry bearing assemblies 12,13 with respect to a wall ofthe rectangularly shaped tubular housing 21.

A suitable stationary base 22 supports housing 21 and by suitable fastening means (such as the nuts 23 and bolts 25) mounts housing 21 to base 22 so asto establish a fixed location forthe axis of rotation of shaft 11.

Means four rotating shaft 11 includes a drive motor 24 mounted upon base 22.

Motor 24 includes a powertake-offspindle 26 for driving a pulley 27. Shaft 11 carries a pulley 28 on an end thereof for rotating with shaft 11. Both pulleys 27, 28 lie in a substantially common plane whereby a plurality of drive belts 29,31,32,33 can be trained about and extend between the pulleys. Each of belts 29,31-33 is sufficiently elastic to cause it to grip both pulleys 27,28 when driven by motor 24 for rotating shaft 11 without need fortensioning means to act against the belts. Preferably the drive belts have a modulus of elasticity providing an elongation of the order of 20% oftheir length whereby tensioning of these belts is derived substatially solely from the elasticity ofthe belt itself.

Means four maintaining the belts axially on both pulleys include a plurality of four sheave portions 27a, 27b, 27c, 27d formed about pulley 27 for engaging an associated one of belts 29,31-33. Pulley 28 includes bounding flanges 34,36 at the ends thereof.

Thus, pulleys 27,28 operate on fixed centers at a predetermined spaced relation from each other.

In operation as the driving pulley 27 engages the relatively elastic belts they tend to griptheirassoci- ated sheave portions 27a-27d so thattensioning of the belt from external sources is not required. For example, in conjunction with belt 33, and with pulley 27 rotating in the direction of arrow 37 the bottom reach 33a will be drawn toward pulley 27 while the upper reach 33bwill be fed toward pulley 28. At the sametime reach 33a will grip pulley 28 and cause itto rotate in the direction ofarrow38.

While apparatus ofthe kind described can be operated with a single elastic beltthe use of a plurality of such belts permits the apparatus to continue in operation should one or more ofthe belts become worn and break. Atthattime it is not necessary to shut down the use of the equipmentwhilewaiting for delivery of a replacement belt.

As noted above, each ofthe belts includes a first and second reach extending between pulleys 27,28, and it will be readily apparent from the description above that the belts are disposed in driving relation between the two pulleys under rotation of one ofthem so as to rotate shaft 11 free oftensioning means acting against the belts.

Accordingly,a primary source of noise is eliminated and the speed of rotation of anywheelltire assembly 74can be significantly reduced to a rate on the order of 40% of that previously believed necessary to achieve a proper signal-to-noise ratio. As a corollary, the drive energy is reduced by approximately 80%. Thus, a 116 horsepower motor can be used where a one horsepower motorways previously required.

Further, by deriving substantially all tensioning from the elastic drive belts both the upper and lower reaches ofthe belts remain freely supported and travel free oftensioning means acting thereagainst.

Claims (6)

1. In a dynamic wheel balancing machine, a drive system for rotating a wheel and tire assembly of a dynamic wheel balancing machine, said drive system having a drive shaft, bearing means supporting said shaft for rotation, one end of said shaft being disposed and adapted to readily removably receive a wheel to be balanced, a first pulley fixed to rotate with said shaft, a drive motor, a second pulley driven by said motor, characterized by means for mounting said first and second pulleys in predetermined spaced relation to each other, drive belt means trained about and extending between said first and second pulleys, wherein said belt means has a modulus of elasticity sufficientto provide substantially all tensioning of said belt when driven by said motor.

2. A drive system according to Claim 1 in which said belt means is characterized by a plurality of belts disposed side by side and trained about and extending between said pulleys, each said belt having a modulus of elasticity sufficient to provide substantially all tensioning thereofwhen driven by said motor.

3. A drive system for rotating a wheel and tire assembly of a dynamicwheel balancing machine according to Claim 1 wherein said modulus of elasticity provides an elongation ofthe order of 20% of its length, tensioning of said belt means derived substantially solely from the elasticity of said belt means trained about said pulleys.

4. A drive system according to Claim 2 in which said belts are sufficiently elastic to cause them to grip both said pulleyswhen driven by said motor for rotating said shaftto permit said belts to remain otherwise free of tensioning means acting against said belts.

5. A drive system according to Claim 2 wherein said plurality of drive belts aretrained about and extend between said first and second pulleys to define first and second reaches therebetween for each said belt, characterized by each said reach being freely supported between said pulleys to travel free of tensioning means acting thereagainst, said belts being sufficiently dimensioned and elasticto cause them to grip both said pulleys to rotate said shaft, one reach of each said belts being stretched by rotation of said second pulley to develop sufficient tension in said belts to cause them to maintain their grip about each pulley to rotate said shaft.

6. Adrivesystemforadynamicwheel balancing machine substantially as hereinbefore described with reference to and as shown in the accompanying drawings.