Gate drive assembly

Details Gate drive assembly Gate drive assembly

1999-07-26

2001-08-28

Bucci, David A. (Department: 3682)

Endless belt power transmission systems or components

Plural turns of same belt about pulley axis

Plural turns of same belt about axis of each of laterally...

C474S067000, C074S089220, C254S387000

Reexamination Certificate

active

06280358

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention refers to a drive, preferably a gate drive, with a belt transmission comprising of a drive pulley and an output pulley.
2. Description of the Related Art
Such belt transmissions as gate drives are familiar from the prior art as toothed belt transmissions. A motor-driven cog drives a corresponding toothed belt which is led over an idler pulley at the other end consisting of a cog wheel. Due to the size of the individual teeth of the toothed belt and of the corresponding cog, a certain minimum diameter must be maintained in the design of the drive pulley so that the whole drive unit is rather large. As well as this, the toothed belts used are relatively expensive.
A cheaper version consists in the use of roller chains led over corresponding cog wheels. Although roller chains are capable of transmitting very high forces, they cause unacceptable noise emissions in operation. In addition to this, the cog wheels used here also have to have a certain minimum diameter which means that the overall unit is relatively large.
Thus, the task of the present invention is to create a gate drive which, on the one hand can be realised cost-effectively and, on the other hand, can transmit large forces in a compact size.
SUMMARY OF THE INVENTION
In the invention, this task is solved by a drive, preferably a gate drive with a belt transmission having a drive pulley and an output pulley. Accordingly, a drive pulley is formed from at least one cylinder which has flanges tapering inwards at its ends. As a drive element a round belt, rope or similar is wound a number of times around the cylinder. The return strand of the round belt, rope or similar can be held continuously under tension.
In the design of the drive according to the invention the same principle is applied as in electrically driven idler pulleys used particularly in shipping. The corresponding belt is wound around this electrically driven idler pulley a number of times. The belt slips through while the electrically driven idler pulley is rotating until the end of the return strand is subjected to tension. Due to the tension on the return strand a frictional grip is generated between the belt and the electrically driven idler pulley. The force that can be taken up by such a contact transmission with the load strand is expressed after Eytelwein by the following equation:
F
1
=F
2
·e
&mgr;&agr;
where F
1
, is the force acting on the load strand, F
2
the force acting on the return strand, &mgr; the coefficient of friction and &agr; the wrap in radian measure.
Up to now there was no simple way of transferring this contact transmission familiar from shipping to a garage gate drive, as in a garage gate drive the reversal of the direction of rotation meant that the load switched between the return strand and the load strand, whereby the belt is forced to slip on the drive pulley when the load is reversed. Due to the design of the drive according to the invention it is now ensured that the round belt, rope or similar serving as the drive element always remains in frictional contact with the drive pulley even when the direction of rotation changes.
In a first preferred version of the invention, the drive pulley consists of two cylinders with flanges tapering inwards on their respective ends, whereby the round belt, rope or similar is wrapped a number of times around each cylinder and whereby the end respectively forming the return strand is led around a spring-loaded idler pulley. This design means that the necessary tension is exercised in a simple manner on the return strand. In this, the idler pulley around which the respective return strand is led, can be arranged between the respective ends of the round belt, rope or similar which respectively form the load strand. Alternatively, the idler pulley may also be arranged outside of the ends of the round belt, rope or similar forming the load strand. The springs exercising the spring force may be realised either as tension or compression springs.
Another alternative version of the drive according to the invention entails the drive pulley consisting of only one cylinder with flanges tapering inwards at its ends. Here the two ends of the round belt, rope or similar are also led over fixed idler elements, between which two idler pulleys are arranged on a moveable carriage arranged perpendicular to the direction of the round belt, rope or similar, around which the round belt, rope or similar is also led. The distance between the pulleys arranged on the carriage is smaller than that between the idler elements opposite each other. In this version when the load strand is tightened it is drawn through on the load side for the most part straight between the rigid idler elements and the idler pulley. The cross-sliding carriage is drawn across to the side to the load strand. The load strand which runs mainly straight along the idler elements and the idler pulley has only a minor contact with the fixed idler elements so that only a negligible frictional force is exercised. The idler element on the return strand of the carriage is drawn inwards by sliding the carriage to the load strand side thereby taking the return strand with it so that the angle of wrap of the return strand around the fixed idler elements on the return strand is enlarged. This generates a relatively large frictional force which is sufficient to generate the required frictional contact between the belt and the drive pulley.
A further design principle for further development of the drive according to the invention consists in the fact that the tension on the return strand is generated by two staggered tensioning elements which work on the principle of a bicycle chain adjuster.
It is an advantage when, at the end of the round belt, rope or similar respectively forming the load strand, there is fixed a carriage with an articulation point, for example for a sectional gate, which can slide back and forth.
It is especially advantageous when an additional tension spring is integrated in the load strand. With this version, a torsion spring, required in the prior art and integrated on the usual spring shaft to roll up the sectional gate, can be replaced. Instead of the usual take-up pulley on which the belt would also be wound up here, in this case the design with the diameter of the correspondingly motor-driven pulley can be retained. With this design the large-diameter take-up pulley as was required in the prior art can be replaced. As well as this, the relatively expensive torsion spring required by the prior art can be replaced by a low-cost linear spring.


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