APPARATUS AND METHOD FOR WINDING AND UNWINDING CLOTH FOR A GREENHOUSE, WHEREIN THE TORQUE IS LIMITED

Abstract: The present invention relates to an apparatus for driving a rotatable member such as a roller (8) for winding and unwinding of cloth (7), for instance for a glasshouse or greenhouse, comprising: a drive motor (17) for rotatably driving a shaft (19) thereof; transmission means (20, 21) for transmitting the rotating movement of the shaft (19) to the rotatable member (8); and torque limiting means (16) coupled operatively to the motor (17) for limiting the couple or torque exerted by the motor (17) on the transmission means (20, 21).

Description: APPARATUS AND METHOD FOR WINDING AND UNWINDING CLOTH FOR A GREENHOUSE, WHEREIN THE TORQUE IS LIMITED In a first type of glasshouse or greenhouse for horticulture it is the current practice for sun-screens to be automatically wound and unwound on the inside of a roof of glass plates in accordance with the quantity of incoming light. In a second type of so-called foil greenhouses the roof is formed by foil which can likewise be automatically wound and unwound by means of electric motors. This second type of greenhouse is usually provided in practice with curved or angled roof trusses over which the cloth or foil is pulled. A number of problems arise in the known systems, including the lack of space for the electric drive motors and the transmission between the electric motors and the rollers onto and from which the cloth is wound and unwound, while it is also necessary to prevent too much shading effect occurring in the interior of the greenhouse due to the presence of the motors . Maintenance of the electric motors is time- consuming, and the glasshouse or greenhouse cannot function optimally during the servicing time. The present invention provides an apparatus for driving a rotating member such as a roller for winding and unwinding of cloth, for instance for a glasshouse or greenhouse, comprising: - a drive motor for rotatably driving a shaft thereof; - transmission means for transmitting the rotating movement of the shaft to the roller member; and - a torque limiter coupled operatively to the motor for limiting the couple or torque exerted by the motor on the transmission means. The torque limiting means according to the present invention avoid wear caused by overload. The transmission means preferably comprise at least one chain and at least two toothed wheels, and more preferably a chain in double or triple form and two sets of two or three adjacently arranged toothed wheels, since little space is available, particularly in the ridge of a greenhouse . The number of loops in the chain depends on the power to be transmitted, i.e. on the size of the cloth and/or the motor. In a further preferred embodiment the transmission means comprise a worm wheel on the transmission so that the drive motor can be formed by a three-phase motor, while the worm wheel transmission is self-locking. The three-phase motor can be of a type normally obtainable on the market, while the occurrence of shading effect by such electric motors of any size is prevented since they are arranged transversely and substantially vertically in relation to the worm wheel transmission. Such usual electric motors are easier to replace and less susceptible to wear than so-called tube motors which, because of their slender form, are likewise applied in glass horticulture. Further advantages, features and details of the present invention will be elucidated on the basis of the following description of a preferred embodiment thereof with reference to the annexed drawings, in which: fig. 1 shows a view in perspective of a preferred embodiment of a foil greenhouse according to the present invention; fig. 2 is a partly cut-away view in perspective of detail II of fig. 1; fig. 3 is a partly cut-away view in perspective of detail III of fig. 2; fig. 4 is a side view, partly in cross-section, of the operation of the apparatus shown in fig. 1, 2 and 3 in a first position; and fig. 5 is a side view, partly in cross-section, of the operation of the apparatus shown in fig. 1-3 in a second, end position. A foil greenhouse 1 (fig. 1) comprises a number of beams 2 which are supported on a ground B via uprights 3 , and a number of channel sections 4 extending transversely of beams 2. Between channel sections 4 extend substantially arcuate (or angled) roof trusses 5, in transverse direction of which extends a ridge profile 6. Between each of the channel sections 4 and the adjacent ridge profile 6 can be tensioned a cloth 7 which can be wound and unwound over a roller 8. The rolling movement of roller 8 is exerted by respective motors 9 and 10 arranged on respective pivotable arms 11, 12. As shown particularly in fig. 2, arm 12 is pivotable relative to a pivot point 13, while on the end of arm 12 is arranged a tube profile 14 which extends transversely thereof and which is fixedly connected on the other side to a housing 15 in which a torque-limiting mechanism 16 is arranged. An electric motor 17 of standard make is also fixedly connected to housing 15. Via a self-locking worm wheel transmission 18 the output shaft of electric motor 17 drives a drive shaft 19 which extends substantially parallel to roller 8 and the rotating movement of which is imparted to this roller member via two parts 20 and 21 of a chain placed closely together. This chain is arranged between two plates 22 and 23 taking up a space of only about 40 mm. Due to the disposition wherein an electric motor extends in each case substantially transversely of the drive shaft 19 in downward direction, this construction, including the housing 15 for the torque- limiting means, will cause practically no shading effect in the wholly wound or unwound state of cloth 7, wherein the construction is situated under either channel section 4 or ridge profile 6. Electric motor 17 is connected non-rotatably via a shaft end 34 (see also fig. 3) to a first plate 25. In addition, a second plate 35 and a third plate 26 are operatively coupled in the housing to first plate 25. The three plates are held in a neutral position by means of screw springs 28 respectively 33. When plate 25 is rotated either plate 35 is rotated on pivot pin 24 or plate 26 is rotated on pivot pin 27. On the middle plate 25, which can pivot together with each of the plates 35 and 26 relative to the housing, are arranged microswitches 29 respectively 30 which are set into operation on contact with an end of adjusting screws 31 respectively 32, the length of which is adjustable. When shaft 19 encounters resistance during driving of cloth 7, for instance at the end of the process of winding or unwinding the cloth, the housing of the electric motor rotates relative to the output shaft and thereby also relative to housing 15 arranged fixedly on the arm, and plate 25 thus rotates until one of the two microswitches is activated and the electric motor is switched off in a manner not shown. Since the distance between microswitch 29 and pivot shaft 24 differs from the distance between pivot shaft 27 and microswitch 30, the respective microswitches are activated at different torques, while this torque is moreover adjustable by means of adjusting screws 31, 32. Fig. 4 shows the situation wherein cloth 7 is pulled taut under a bent profile part 41 on channel section 4. In this situation a relatively large torque must be allowed before electric motor 17 is switched off. In the embodiment of fig. 5 the cloth 7 wound onto a roller 8 is enclosed in an interior space in ridge profile 6, wherein electric motor 17 must be stopped after the electric motor encounters a relatively small resistance torque. In the situation of fig. 4 there is a torque of for instance 120 Newtonmmeter (Nm) and in the situation of fig. 5 of 40 Nm. The invention is not limited to the above described preferred embodiment thereof; the rights sought are defined by the following claims, within the scope of which many modifications can be envisaged.

Claims: CLAIMS 1. Apparatus for driving a rotatable member such as a roller for winding and unwinding of cloth, for instance for a glasshouse or greenhouse, comprising: - a drive motor for rotatably driving a shaft thereof; - transmission means for transmitting the rotating movement of the shaft to the rotatable member; and - torque limiting means coupled operatively to the motor for limiting the couple or torque exerted by the motor on the transmission means. 2. Apparatus as claimed in claim 1, wherein the drive motor is an electric motor. 3. Apparatus as claimed in claim 1 or 2 , wherein the transmission means comprise at least one chain and at least two toothed wheels. 4. Apparatus as claimed in claim 1, 2 or 3 , wherein the transmission means comprise a worm wheel transmission for driving a shaft extending substantially transversely of the output shaft of the electric motor. 5. Apparatus as claimed in any of the claims 1- 4, wherein the electric motor, the transmission means and the torque limiting means are arranged on a pivotable arm. 6. Apparatus as claimed in any of the claims 1- 5, wherein the torque limiting means comprise at least one microswitch. 7. Apparatus as claimed in any of the claims 1- 6, wherein the torque limiting means comprise a housing in which a number of plates are arranged which define the length of the arm associated with the desired torque to be limited. 8. Glasshouse or greenhouse provided with an apparatus as claimed in one or more of the claims 1-7. 9. Glasshouse or greenhouse as claimed in claim 8 comprising substantially arcuate roof trusses between a ridge profile and a channel section. 10. Method of winding and unwinding cloth in a glasshouse or greenhouse, comprising an apparatus as claimed in one or more of the claims 1-7. 11. Method as claimed in claim 10, wherein the torque in downward direction is limited to a lesser extent than in upward direction. 12. Method as claimed in claim 11, wherein the torque for limiting in downward direction amounts to about 120 Nm and in upward direction to about 40 Nm.

Inventors: VAN KOUWEN HENRICUS WILHELMUS, VAN KOUWEN, HENRICUS, WILHELMUS
Applicants: KOUWEN HENRICUS WILHELMUS VAN, VAN KOUWEN, HENRICUS, WILHELMUS
Application year: 1999
Main classification: A01G9
IPC codes: A01G9, E06B9