Door drive mechanism including belt transmission for doors

A motor driven door drive mechanism is provided having a belt transmission including a flat belt or a round belt which passes around two rotating guide wheels of which at least one is driven to take along the belt. The driven wheel is embodied by a gear and another gear is provided which loosely meshes with the drive gear, partly pressing the belt into the gaps between the teeth thereof. This arrangement offers a sound compromise between the amount of drive force that can be transmitted, and the manufacturing cost and results in low noise level in operation.

FIELD OF THE INVENTION 
The instant invention relates motor driven door drive means, especially for 
garage doors or workroom doors of the wing or panel type or of sectional 
or over-the-head design, comprising a drive belt transmission. The 
invention further relates to an automobile garage door or a workroom door 
with such door drive means. The invention still further relates to a belt 
transmission comprising a transmission belt which is passed around two 
rotating guide wheels or other guide members, at least one of which is 
driven to take along the belt. The drive of said one guide wheel may serve 
to drive also the other guide wheel, through said belt. The guide wheels, 
on the other hand, may serve to drive merely the belt if the latter is 
provided with an engagement piece or other pickup means from which to 
derive the driving force for the door leafs, panels, or sectional members 
or wings. 
BACKGROUND OF THE INVENTION 
Door drives comprising belt transmissions, belt transmissions, and doors 
operated by belt transmissions of the type mentioned above have been known 
for a long time in the most varied forms. The belt transmission may 
comprise a flat belt which is passed under tension around cylindrical 
pulleys, whereby the drive force is transmitted from the driven pulley to 
the belt by force or friction lock. Greater forces can be transmitted if V 
belts are used which are passed around grooved V belt pulleys (JP 
2-173,436 A, Patent Abstracts of Japan, Vol. 14, No. 436, Sep. 18, 1990). 
It is likewise known to devise the transmission belt as a toothed belt for 
cooperation with a drive wheel provided with complementary teeth along its 
periphery (DD 238,093 A1; FR 1,379,737 A). Other comparable drive means 
operate with round belts, such as smooth steel cables which are guided 
around grooved pulleys, or steel cables on which balls or the like are 
fastened at certain intervals for engagement in complementary, grooves 
with cavities formed in corresponding guide wheels. Moreover, chain drives 
comprising suitable sprockets are used as door propelling means. Many of 
these measures are intended to warrant that the drive force is transmitted 
in form lock. The fields of application of these drive means partly differ 
from one another, while they overlap in other respects. The strengths and 
weaknesses, or the advantages and disadvantages, of all these drives are 
well known. Those skilled in the art likewise dispose of sufficient 
knowledge concerning materials which are suitable for flat belts, round 
belts, and V belts. 
SUMMARY OF THE INVENTION 
It is the object of the invention to provide a novel door drive, a novel 
belt transmission, and a novel door comprising a door leaf which is driven 
by such novel belt transmission. 
It is a further object of the invention to offer a satisfactory compromise 
between the transmissible drive force, operational reliability, 
manufacturing cost, and low noise level in operation of the belt 
transmission. 
The invention resides within this means in the drive wheel being embodied 
by a motor driven gear and at least another gear being provided which 
meshes loosely with said gear to take along a belt made of deformable 
fiber material, during rotation, by the tips of the teeth of one gear 
pressing the belt into the gaps between teeth of the other gear to such an 
extent that the belt is driven practically without slip. 
The pliable, partly yielding belt may be a flat or round textile band made 
of synthetic fibers or in particular of synthetic filaments, in other 
words it may be a woven, braided, or twisted belt which, moreover, can be 
treated, untreated, rubberized or not. A great variety of flat belts are 
known. 
However, the only suitable materials are those which can be permanently 
deformed or stretched. Polyethylene filaments are not very well suited in 
this context. Good results, on the other hand, are achieved if the belts 
are made of cold-stretched polyester, polyamide or polypropylene cord 
filaments. The admissible peripheral or running speed is inherently 
limited. The belt should be made of a material which gradually becomes 
permanently deformed, being stretched and becoming stabilized by the great 
number of passes between gears. 
Flat belts preferably are made of a woven or braided fabric, the thickness 
and width of which depend on the force to be transmitted and the desirable 
performance. 
Any inexpensive, commercially available belt or rope of synthetic 
filaments, such as known for slatted roller blinds is sufficient if the 
belt transmission is used to drive a garage door or a workroom door or if 
it is employed in a gate drive means or a garage or workroom door 
comprising means to transmit the driving force for opening and closing the 
door leaf. 
The gears may be conventional gears having teeth which are rounded at the 
outer edges, or they may be matched gears. The driven gear is formed with 
a circumferential groove if the belt used is a round belt. A plurality of 
such round belts can be used in order to increase the drive force than can 
be transmitted. In the latter event, the gear includes a corresponding 
number of grooves in each of which approximately one half of a round belt 
is accommodated. 
In operation, the belt or band is gradually deformed permanently, adopting 
a corrugated configuration which, surprisingly, does not stretch even 
under the loading of the drive pull. The drive force mainly is introduced 
in form lock, and yet no belt is needed which is profiled to begin with, 
such as a toothed belt. As a consequence, the transmission of force is 
greater than in the case of belts which remain flat and are driven solely 
by friction-lock engagement. If the belt is wider than the driven gear so 
as to project somewhat at both sides, especially by from about 5 to 10 mm, 
the embossing or stamping of the belt is restricted to the central zone. 
In this event, therefore, the two outer marginal zones do not become 
embossed and it is their task in the transmission of force to help 
maintain the length and tension in the belt transmission. The embossing in 
the central driving area of the belt occurs by stretching of the material 
during the run-in phase. The straight, undrawn side portions guarantee 
that the embossing obtained in the middle by stretching remains stable. 
This effect can be achieved most easily by providing a non-driven gear 
which is wider than the driven gear. 
Different diameter gears may prove to be convenient because, on the one 
hand, that facilitates engagement and, on the other hand, switchover is 
possible from the drive of one gear to that of another so that a kind of 
changeover gear mechanism is established by which the running speed of the 
belt can be changed from one to another. In operation, it proved that the 
drive is effected practically without slip, even when shock loading 
occurs. Three travelling speeds of the transmission belt can be obtained 
if three intermeshing gears of different diameters are provided around 
which the drive belt passes. 
The costs of the belt are relatively low when compared to chains, V belts, 
toothed belts, and the like, amounting in part to no more than about 10% 
of the former. In principle, the belt transmission can be used with 
different gears, i.e. gears having different tooth modules (different 
pitch). Usually it is unnecessary to have belts made especially for the 
purpose in question. Where the drive performance is not too high, such as 
in the case of driving doors of garages for one or two automobiles, all 
that is needed are roller blind belts or textile ropes. These belts and 
similar ones are highly elastic and, therefore, can move also around small 
gears. The top and bottom surfaces of such a belt have the same grip. In 
operation it shows how very little noise they generate since no metallic 
parts move in mutual engagement. The belts can be purchased by the yard. 
They can be made into endless belts with the aid of screws, adhesives or 
by vulcanizing. Especially in the event of using textile belts, these may 
be colored so as to specific characteristic effects. As compared to flat 
belts, round belts have the advantage that any twist occurring in the 
course of use around the longitudinal axis of the belt practically remains 
invisible.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The belt transmission comprises a drive gear 1, a driven wheel 2 disposed 
at the particular distance required, a second gear 3 which meshes loosely 
with the first gear 1 and takes over the function of embossing the woven 
drive band or transmission belt 4. The spacing between wheels 1 and 2 may 
be as great as required in any particular case. The flat drive belt 4 is a 
textile belt which is disposed under light tension around gear 1 and wheel 
2. The embossing gear 3 is moved into engagement with the drive gear 1 
under light tension or resiliently, if desired. This approach is realized 
in such a way that the teeth of the embossing gear 3 press the belt 4 
somewhat into the gaps between teeth of the driven gear 1. 
After some thousand passings or revolutions, the belt has become 
permanently corrugated. The waves are exactly identical with the tooth 
module of the drive gear. In the range of the meshing between the two 
gears, the flat belt has become a corrugated belt with permanent 
undulations. The belt material is selected in consideration of this 
desirable permanent deformation. 
In principle, it is possible also to use thin belts of which the 
corrugation achieved in operation is not permanent. However, this type of 
belt is less desirable. These belts tend to sag in the returning run. And, 
although the sag can be taken care of by tension rollers, this would 
render the drive complicated if destined for operation in two directions. 
The fact that the textile belt immerses in the space between the teeth of 
the drive gear practically excludes any slip. In principle, the big gear 1 
shown in the drawing may serve as the drive gear, or the smaller one which 
is designated embossing gear 3. If the drive can be switched between these 
two gears, the belt 4 can be operated at two travelling speeds. 
As shown in FIG. 2, the belt 4 is provided with a pickup means or an 
engagement piece 16. This engagement piece 16 will not run up on either 
one of the wheels 1 and 2 if the reciprocations operating path is smaller 
than the spacing between them, for example in the case of a garage door 
which is movable in two directions. 
As shown in FIG. 2, this embodiment comprises two gears 11 and 12 which 
cooperate with the driven gear 1. The teeth of the two additional gears 
engage somewhat in the gaps between the teeth of gear 1. A plurality of 
round belts 14, having a diameter in the range of from about 6 to 8 mm, 
pass in parallel with one another around wheel 2 as well as gears 1, 11, 
and 12. The round belts of polyamide filaments are embodied by woven round 
cords positioned in approximately semicircular grooves formed in the 
circumference of the driven gear 1 (as shown in FIG. 3) and preferably 
also in that of wheel 2. The meshing gears 11 and 12 have no grooves, 
instead their teeth merely press the round belts a little into the gaps 
between teeth of gear 1. The drive force which can be transmitted is 
increased and the safety of the belt drive enhanced by the fact that a 
plurality of round belts 14 can be arranged parallel to each other. If one 
round belt should fail, the others continue to operate.