Endless belt power transmission systems or components – Means for adjusting belt tension or for shifting belt,... – Gravity actuated guide roll for tensioning belt
Patent
1996-04-29
1998-07-28
Schoeppel, Roger J.
Endless belt power transmission systems or components
Means for adjusting belt tension or for shifting belt,...
Gravity actuated guide roll for tensioning belt
474101, F16H 712
Patent
active
057856206
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a drive assembly comprising an endless rotating drive element which runs over a driving gear of a motor and a driven gear of a machine, and a tensioning means for the drive element.
BACKGROUND OF THE INVENTION
Very different types of drive assemblies of the above-described kind are known; for instance, the drive element may be formed as a V-belt, a flat belt, a chain, etc.
Especially with belt drives, an exact adjustment of the belt tension is required. Excessive belt tension leads to an overload of the motor and the working device and to premature wear of bearings, seals and the belt. With V-belts, a pretension which is too high by 10% reduces the service life by 20%; an increase in pretension by 20% reduces the service life by more than 50%. When the belt tension is too low, the belt may slip, resulting in heating and short-term wear of the belt. Moreover, the efficiency of the machine is reduced considerably.
As for the tensioning of the drive element, different solutions follow from the prior art. One solution is that the axes or shafts of the motor and the machine which are parallel with each other are varied by a tensioning device as to their spacing, i.e., either the motor or the machine is moved on a slide. To this end the shafts of the motor and the machine must each be adjusted in an exact manner. This presents great difficulties, especially when the belt is changed. Furthermore, it is only possible under great difficulties to tension the drive element/the belt in the desired manner.
Another principle consists in tensioning the drive element/belt by means of a tension pulley. The latter may be arranged internally or externally. It has been found to be of disadvantage that an additional tension pulley produces an additional bending stress in the belt/drive element, thereby additionally stressing the latter. Such an additional stress or load is, for instance, created by a kneading of the belt, so that the belt will heat up and wear. Furthermore, the tension pulley excludes an enclosing angle of the driving gear and of the driven gear, thus possibly leading to undesired forces and loads.
Another variant consists in supporting the motor stationarily on a frame and in arranging the machine of a considerably smaller weight on a rocker. To tension the drive element/belt, the rocker is tensioned away from the motor by means of a spring. It is here disadvantageous that the pretension must be adjusted accurately and controlled frequently. An elongation of the belt will change the pretension, which may lead to slip. It is also disadvantageous that fatigue phenomena may be observed, resulting in a reduced pretensioning force.
SUMMARY OF THE INVENTION
It is the object of the present invention to provide a drive assembly of the above-mentioned type which, being of a simple structure and usable in a simple, reliable manner, permits an exact pretensioning of the drive element at which the drive element can be easily exchanged and which prevents damage during transportation of the drive assembly.
In accordance with the invention, this object is achieved in that the motor is arranged on a support which is supported in a positionally variable manner on a frame that carries the machine, and which is pretensioned vertically downwards by both the weight of the motor and by a pretensioning force of a pretensioning unit which acts substantially in parallel with the weight of the motor.
The drive assembly of the invention is characterized by a number of considerable advantages. Since the weight of the motor pretensions the drive element, one obtains a defined tensioning force throughout the service life of the drive element. Elongations of the drive element are compensated automatically. Since the weight of the motor does not change, a pretensioning force which is always constant is applied by the motor.
Another essential advantage is that the accelerating torque supports the pretension of the drive belt during start of the motor. The pretension might thus be
REFERENCES:
patent: 1194010 (1916-08-01), Goodyear
patent: 2570773 (1951-10-01), Davis
patent: 4094205 (1978-06-01), Cook
patent: 4568030 (1986-02-01), Weichel
patent: 4761154 (1988-08-01), Beauchamp et al.
patent: 4781662 (1988-11-01), Walker
Beutel Wolfgang
Ewertowski Julius
Boge Kompressoren Otto Boge GmbH & Co. KG
Schoeppel Roger J.
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