Abstract:
A system for conveying plant trays in a greenhouse having continuous conveyors, each in the form of a cable having cable ends spliced together and adapted to support and convey in an upright condition plant trays through the greenhouse, the continuous conveyor having an upper plant transport portion and a lower cable return portion. The system has first end and second end pulleys to receive the continuous conveyors and a motor attached to the first end pulleys to drive the continuous conveyors, whereby, the system is capable of transporting the plant trays through the greenhouse on the continuous conveyors from the first end pulleys to the second end pulleys.

Description:
BACKGROUND OF THE INVENTION 
     This invention pertains to a means for transporting large numbers of plant trays. In particular, this invention relates to a novel conveyor for transporting plant trays on cable conveyors powered by a motor to move the plant trays throughout and in and out of a greenhouse. 
     It is common in the nursery business to use greenhouses for germinating and growing plants. Typically, plants are planted as seeds or cuttings in 11 inch by 22 inch plastic flats. Growing of plants in greenhouses often requires frequent movement of plants from one location to another, such as from the potting shed to the germinating greenhouse, and from one area of a particular greenhouse to another to accommodate sunlight demands of the growing foliage. 
     A majority of greenhouses employ benches to provide a platform for laying out plants and keep the stock level elevated above the floor. Benches are typically constructed of steel, wood, plastic, or concrete frames with galvanized expanded metal, turkey wire, or special bench fabrics spread across the top. Galvanized expanded metal or other bench surfaces allow water to drain from the plants during frequent watering. 
     Methods currently used by greenhouses to transfer plants include the use of portable conveyors. The conveyors are typically in multiple sections with each section being ten to twelve feet long. One section, the drive section, is motorized and quite heavy. The other conveyor sections connect to the drive section through a gear mechanism at each junction. The conveyor is typically configured with numerous sections in place and sections are removed and the conveyor shortened as the benches are filled with plants. 
     The time and effort required to lay out and connect the sections of the conveyor and then remove sections as benches are filled is so substantial that most greenhouse operators have found that this is not acceptable. Most greenhouses have found that it is easier and more efficient to let people carry the flats. One person can typically only carry one or two flats at a time. Therefore, there is typically a lot of labor involved in moving plants around in a greenhouse, and multiple trips must be made up and down the aisles to distribute plants. 
     It is also known to support numerous plant trays on extended beams which stretch from inside a greenhouse to outside a greenhouse. Commercial nurseries have such facilities in order to move thousands of potted plants, supported on trays, out of the greenhouses into the natural sunlight and exposed to the rain and ambient environment. When and as the weather dictates, the trays are moved along the beams and returned to the protection of the greenhouses and, to this end, a side wall of each greenhouse is apertured to accommodate the beams thereinto. 
     These prior transport systems have numerous disadvantages. For example, typical plant conveyors known in the art are bulky, heavy, and expensive. 
     Other transport systems in the prior art include U.S. Pat. No. 4,628,631 and U.S. Pat. No. 4,547,992 which teach a cable driven system, but this is for carrying plants on hangers to a watering station. 
     U.S. Pat. No. 4,876,967 teaches a transporter for plant trays where the trays have rollers which ride on beams. Here, the first tray has a motor to pull a string of the wheeled trays. 
     U.S. Pat. No. 4,837,971 teaches a transport system in which moveable tables are provided on which plants in containers have been placed. The legs of the table have wheels that rest on rails. 
     U.S. Pat. No. 4,930,253 teaches a transport system in which channels filled with water float plant trays. Wires are used to support the trays. Here, a large and heavy, separate conveyor system is used. 
     Finally, in U.S. Pat. No. 5,974,733, a greenhouse conveyor system is taught which uses manual wheeled carts. 
     The present invention, uses relatively small diameter cables as the “belt” onto which the plant trays ride. The use of such cables has numerous advantages which will be discussed in detail below. 
     SUMMARY OF THE INVENTION 
     The present invention is for a system for conveying plant trays in a greenhouse. The system has continuous conveyors, each in the form of a cable having cable ends spliced together and adapted to support and convey in an upright condition plant trays through the greenhouse, the continuous conveyor having an upper plant transport portion and a lower cable return portion. The system has first end and second end pulleys to receive the continuous conveyors and a motor attached to the first end pulleys to drive the continuous conveyor, whereby, the system is capable of transporting the plant trays through the greenhouse on the continuous conveyors from the first end pulleys to the second end pulleys. 
     Accordingly, it is an object of the present invention to provide an apparatus for conveying plant trays in a greenhouse that overcomes the disadvantages of prior art means to convey plant trays through a greenhouse. 
     It is another object of the present invention to provide an apparatus for conveying plant trays in a greenhouse that produces a minimal shadow such that plants below and adjacent the apparatus receive maximum sunlight without substantial shadows. 
     It is yet another object of the present invention to provide an apparatus for conveying plant trays in a greenhouse that produces a minimal shadow such that plants below and adjacent the apparatus receive maximum water spray without substantial deflection of the water by the apparatus. 
     It is a further object of the present invention to provide an apparatus for conveying plant trays in a greenhouse that is inexpensive to purchase and to operate. 
     It is another object of the present invention to provide an apparatus for conveying plant trays in a greenhouse that is easy to customize. 
     It is still another object of the present invention to provide an apparatus for conveying plant trays in a greenhouse that has minimal complexity. 
     It is another object of the present invention to provide an apparatus for conveying plant trays in a greenhouse that is easy and relatively inexpensive to install. 
     It is yet another object of the present invention to provide an apparatus for conveying plant trays in a greenhouse that may be easily upgraded or expanded to meet differing need of a user. 
     It is a further object of the present invention to provide an apparatus for conveying plant trays in a greenhouse that is flexible to allow easy customized installations using standard system assemblies. 
     It is a still further object of the present invention to provide an apparatus for conveying plant trays in a greenhouse that uses cables that may are adjustable to provide an appropriate amount of tension. 
     Other objects of the present invention, as well as the novel features thereof, will become more apparent by reference to the following description, taken in conjunction with the following drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an apparatus for conveying plant trays in a greenhouse in accordance with one preferred embodiment of the present invention. 
     FIG. 2 is a perspective view of the motor and drive pulley assembly of FIG.  1 . 
     FIG. 3 is a perspective view of the end pulley assembly of FIG.  1 . 
     FIG. 4 is a perspective view of a dual central support pulley assembly for supporting a center area of the upper transport portion of the cable conveyor belt and the lower return portion of the cable conveyor belt of FIG.  1 . 
     FIG. 5 is a perspective view of a single central support pulley assembly for supporting a center area of the support portion of the cable conveyor belt of FIG.  1 . 
     FIG. 6 is a front elevation view of an apparatus for conveying plant trays in a greenhouse in accordance with an alternate preferred embodiment of the present invention. 
     FIG. 7 is a bottom plan view of a tensioniong apparatus as used in the apparatus for conveying plant trays of FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the figures wherein like reference characters in the figures refer to like elements throughout the several views, there is shown in FIG. 1 an apparatus for conveying plants trays in a greenhouse  10  in accordance with one preferred embodiment of the present invention. The apparatus for conveying plant trays  10  in a greenhouse generally includes a drive assembly  12 , which includes a drive means or motor  13 , a drive means speed reducer  14 , preferably in the form of a chain driven by gears, and at least a pair of drive pulleys  16 , a continuous conveyor cable  18  for each drive pulley  16 , and an end pulley assembly  29  (see FIG. 3) which includes an end pulley  28  for each drive pulley  18 . Optionally, dual central pulley assemblies  20  (see FIG. 4) and single central pulley assemblies  22  (see FIG.  5 ), which include upper  24  and lower  26  support pulleys may be used over longer spans to minimize conveyor cable  18  sag, as will be described in more detail below. The apparatus for conveying plant trays is supported on support walls or structural posts  34  that may or may not be part of the permanent structure of the greenhouse. 
     As can be seen in FIG. 1, the drive assembly  13  (see FIG.  2 ), which includes the drive means  12  which preferably is a reversible electric motor. The required power of the drive means  12  depends upon the weight of the plant trays  11  that the conveyor system  10  is capable of carrying based on available space and the total length of the conveyor system  1   0  as well as the gear ratio of the speed reducer  14 . The size of the drive means  12  or electric motor can therefore be easily be determined by one skilled in the art of conveyor systems, depending upon the requirements of the particular system installed. The drive means  12  is connected to the speed reducer  14 , preferably variable, such that the speed of the conveyor system  10  can be adjusted to a user&#39;s requirements. Drive shaft  15  extends out from the speed reducer and causes drive pulleys  16  to rotate about bearings  40 . The speed reducer  14  may be a chain driven by gears as depicted in the figures or any other type of drive, including direct drive, as known. Rotation of the drive pulleys  16  causes continuous conveyor cables  18  to move along the path of the pulleys as described below. This assembly is attached to a drive means mounting beam  42  which is attached to a support wall or post  34  in the greenhouse. Plant trays  11  ride atop continuous conveyor cables  18  and are moved from the drive assembly  13  to the end pulleys  29 , or vice versa. 
     The continuous conveyor cable  18  is driven by drive means  12  and rides continuously from drive pulleys  16  to upper central pulleys  24  to end pulleys  28  to lower central pulleys  26  and back to drive pulleys  16 . In the present preferred embodiment, two continuous conveyor cables  18  are used. However, depending upon a the requirements for a particular greenhouse, three more continuous conveyor cables  18  may be used, with appropriate number of pulleys. 
     The total length of the apparatus for conveying plant trays  10  is entirely flexible depending upon the size of the greenhouse and the needs of the operator for conveying plants. The length of the system is limited primarily by the size of the drive means  12  in combination with the speed reducer  14 . Of course, for very large systems, the size of the continuous conveyor cables  18 , associated pulleys  16 ,  24 ,  26 ,  28  and other associated components would also have to be increased accordingly. 
     Depending upon the length of the system, cable supports, may include dual central pulley assembly  20  (see FIG. 4) and/or single central pulley assemblies  22  (see FIG.  5 ). These assembles  20 ,  22  have upper central pulleys  24 , and, for the dual central pulley assemblies  20 , lower central pulleys  26  which may be used to aid in supporting the continuous conveyor cables  18  to reduce cable sag. In most instances, there would be a need for more upper support pulleys  24  than lower support pulleys since the weight of both the continuous conveyor cables  18  themselves and the plant trays  11  would be creating a downward load. Lower support pulleys  26  would be most useful to prevent cable sag when the system has no or a minimal number of plant trays  11 . Upper pulleys  24  may be supported on either the single central pulley assembly  22  or the dual central pulley assembly  24 . The single central pulley assembly  22  comprises a single central pulley support rail  23 , pulleys  24 , adjustable guide cable supports  30 , cable attachment plates  33  and end cable attachment plates  35 . The dual central pulley assembly  20  has a dual central pulley support rail  21 , pulleys  24 ,  26 , adjustable guide cable supports  30  and cable attachment plates  33 . The single central pulley assembly  22  has pulleys  24  mounted only adjacent to the upper transport portion  38  of the continuous conveyor cable  18 , while the dual central pulley assembly  20  has pulleys  24 ,  26  mounted adjacent both the upper transport portion  38  and the lower return portion  36  of the continuous conveyor cable  18 . The pulleys are supported on upper pulley supports  25  and lower pulley supports  27 . The end pulley assembly  29  (see FIG. 3) includes end pulleys  28  that are supported on end pulley mounting beam  44  and preferably ride in end pulley bearings that uses shafts  46  as their axle. 
     As can be seen in FIG. 1, and in detail in FIGS. 4 and 5, an optional feature of the present invention is the inclusion of adjustable plant tray guides, preferably in the form of guide rail cables  32 . The guide rail cables  32  are attached to end cable attachment plates  35  (see FIG. 3) and central cable attachment plates  33  (see FIG. 4,  5 ). These plates  33 ,  35  are attached to adjustable guide cable supports  30 . As can be seen, the adjustable guide cable supports  30  are preferably attached by a bolt to support rails  21 ,  23  through a slotted hole in the cable support  30  such that the guide rail cables  32  can be moved in and out, perpendicular to the travel of the conveyor cable  18  to accompany different widths of plant trays  11 . Guide cable attachment plates  33  are likewise attached to the cable support  30  through a slotted hole to allow the guide rail cables  32  to be raised or lowered to a desired height above the conveyor cable  18 . The guide rail cables  32  are threaded through slotted holes  37  in the cable attachment plates, thereby supporting the guide rail cables  32 . 
     In the alternate preferred embodiment of FIGS. 6 and 7, there is disclosed an apparatus for conveying plant trays in a greenhouse  10 ′ with an optional cable tensioning apparatus  50 . As can be most clearly seen in FIG. 6, the system  10 ′ is substantially the same as that of the first embodiment, but also includes at least one section where each continuous conveyor cable  18 ′ is looped through two sets of tensioner pulleys  54  that an have adjustment means, such as adjustment screws  52 . Here, either as an initial adjustment when the system is set up, or after substantial use when the continuous cable conveyor and other parts of the system  10 ′ are either stretched or worn, the cables can be tightened or loosened by an amount limited by the length of the screws. For example, if the continuous conveyor cables  18 ′ require tightening, screws  52  can be rotated to draw the tensioning pulleys  64  in direction A, as shown in FIG.  6 . Likewise, if the continuous conveyor cable  18 ′ require loosening, screws  52  can be rotated to slightly release the tensioning pulleys in direction B, as shown in FIG.  6 . 
     The continuous conveyor cables  18  are preferably constructed from a commonly available stainless steel cable or other corrosion resistant material to minimize corrosion. However, other cable materials as are known and appropriate may be used. The continuous conveyor cables  18  have ends that have been spliced together to form an endless loop. Other elements are preferably either mounted in a covered condition or made from water repellant materials such that the constant watering associated with a greenhouse does not affect performance of the system. 
     The present system is preferably permanently attached to structural posts  34  in a greenhouse. Since the system is primarily cable, relatively little shadow is cast to block light and water. Plants and plant trays may be placed directly under the system to maximize growing space. 
     Currently, costs are estimated to be five to six times less than belt driven systems as are known in the art. Additionally, it is preferable that each system is custom made to suit a particular grower&#39;s requirements. However, each system may be made from standard assemblies, including the drive assembly  13 , the dual central pulley assembly  20 , the single central pulley assembly  22 , the end pulley assembly  29  and the conveyor cables  18  as described above. Of course, with appropriate pulleys, the present system could easily be configured to go around corners or bends. 
     Without further elaboration, the foregoing will so fully illustrate my invention that others may, by applying current or future knowledge, readily adapt the same for use under various conditions of service.