This invention relates to an apparatus for growing plants contained in a plurality of troughs which are supplied with nutrient solution and which in parallel relationship and in succession are to be intermittently advanced in a generally horizontal direction perpendicular to the longitudinal directions of the troughs themselves over a bed by driving means permitting increasing of the spacings between the troughs as the plants develop.

Such apparatuses are mainly used in hothouses where the development of the plants is forced by the use of favourable temperature and atmosperic conditions as well as, at least to a certain extent, of artificial light. Particularly well are such apparatuses suited for commercial growing on a large scale of lettuce and other vegetables as well as of decorative plants.

An apparatus of the kind referred to is previously known through the U.S. Patent Specification No. 4,216,618, in'which the displacement of the troughs is effected by means of a kind of screw means having different pitch along different portions of their lengths. In another known apparatus of the kind in question, disclosed in the publicly available Norwegian Patent Application No. 814355, the troughs are supported and moved by means of a plurality of partly overlapping belt conveyors arranged in succession and all being driven by individual motors.

Common to both these known apparatuses is that all the troughs are moved solely in one single predetermined direction from one end of the bed to the other in a single plane. This gives rise to several inconveniences, particularly in view of the facts that in practice the number of troughs is very high, commonly many hundreds, and that the lengths of the troughs is often considerable, say in the order of about ten meters. One such inconvenience is that the troughs must be returned from the outlet end of the bed to the inlet end thereof before they can be re- _used,which in view of the length and slenderness of each trough requires special aids. Another inconvenience is that the apparatus requires a tremendous floor space, which is highly objectionable particularly in hothouses, in which the building costs as well as the costs for heating etcetera is highly dependent on the size of the floor space.

Apart from this, the screw means of the apparatus disclosed in the beforementioned US 4,216,618 are extremely expensive and operate poorly, especially when a high pitch is used, and in addition, since all the troughs in the apparatus are to be moved simultaneously, there is an intermittent need for an extremely high driving power, which is highly objectionable from several points of view. On the other hand, the apparatus disclosed in the beforementioned NO Application 814355 needs a plurality of belt driving motors each capable of accelerating its own conveyor also when the latter carries a full load of troughs, and in addition a complicated sensor and switch system for controlling the operation of these motors. Apart from the fact that the troughs in this latter apparatus may easily slip on the conveyors and thereby accidentally change their relative positions so that their proper advance is disturbed, the troughs when being transferred from one conveyor to the next are subjected to lateral tilting movements in combination with abrupt deceleration and acceleration whereby they may easily tumble over and loose their contents.

Accordingly it is the aim of the present invention to provide an improved apparatus of the kind defined in the introductory paragraph which in the first place permits an optimum utilization of the occupied floor space, i.e. makes it possible to grow a great number of plants within a limited area in a hothouse, and which further is highly convenient in use by making it possible to harvest matured' plants and to insert new small plants in the emptied troughs at one end of the apparatus, thereby eliminating all the need for transporting empty troughs outside the apparatus from one end thereof to the other.

Basically this aim is achieved by the fact that the apparatus according to the invention presents the features set forth in the appended claim I, preferred embodiments of the apparatus being defined in the subclaims.

A further object of the invention is to provide improved means for advancing the troughs on the bed and for increasing the spacings between them, so that only moderate motor power will be required for such purpose and the troughs may be moved smoothly, carefully and accurately one by one while being positively prevented from tumbling over during their transports to selected new positions. Such meεns are specifically set forth in claims 4-8 and may be used also in modified forms of apparatuses, although with less advantage.

For further elucidation of the invention a preferred embodiment thereof will now be more closely described with reference to the accompanying drawings, in which

• Fig. 1 is a diagrammatic illustration of the plant growing cycle taking place in a preferred form of apparatus embodying the invention,
• Fig. 2 is a shortened and simplified side view of a preferred form of apparatus embodying the invention, and
• Fig. 3 is a shortened cross sectional elevation taken along the line III-III in Fig. 2.

In Fig. 1 numeral 1 designates elongate troughs extending away from the viewer, and each such trough contains a long row of spaced apart pots 2, say about fifty or more, of which only one in each trough is visible in the figure. As illustrated, the troughs 1 are arranged in a generally closed circuit in which they are intermittently moved in a counterclockwise direction away from and back to a plant harvesting and trough reloading station, situated to the left in the figure, where the matured plants 3, assumed to be lettuce heads in the instant case, are removed from the troughs 1 together with their respective pots 2, and new pots containing seedlings 4 are inserted in each emptied trough before the latter is again circulated. Although, for the sake of simplicity, Fig. 1 shows only a limited total number of parallel troughs 1 it should be understood that in practice this number may be many hundreds depending on the desired production capacity and on the time it takes for the plants to mature.

As illustrated, the troughs 1 form successive groups, each occupying a different section A, B, C, D, E, F or G of the support on which they are rested (not shown), the troughs within section A containing plants which are still only little developed and need no more horizontal space than the pots 2, and the troughs of group G containing fully matured plants 3 ready for harvesting and needing considerably more space each in order not to interfere with each other. For this reason the spacings between adjacent troughs 1 are increased in a manner known per se as the troughs are advanced through the circuit. Thus within section A the troughs 1 stand close to each other in the same manner as they were put in to the left of the lower level of Fig. 1 after having received new pots 2 with seedlings 4, whereas the troughs 1 in section B are slightly spread apart, in section C a little more spaced and so on until the spacings between them have reached a maximum within section G. As can be seen the number of troughs 1 is the same within all the sections A to G, and it is to be understood that all the troughs of each group are moved over at selected time intervals from section to section as the plants in them grow up.

Although Fig. 1 may simply be understood to illustrate, within a limited drawing space, the mere advance of the troughs 1 from a loading station, where potted seedlings are inserted in them, to a separate harvesting station, where the grown-up plants are removed, on one and the same level, the emptied troughs being then returned from the harvesting station to the loading station in any suitable known manner, it also illustrates an important part of the present invention, namely the idea that the troughs 1 may be advanced on two vertically spaced apart levels, one above the other, and be transferred one by one between these two levels by suitable elevator means. By such an arrangement considerable floor space may be saved within a hothouse without any reduction of the number of troughs or of the production capacity.

In Figs. 2 and 3 there is shown an apparatus for growing plants in which the concept just referred to is realized and in which also novel and improved means for advancing the troughs containing the plants to be grown and for simultaneously increasing the spacings between said troughs are used. Also in Figs. 2 and 3 the troughs are designated by numeral 1, the pots by numeral 2 and some, only partially developed, plants by numeral 3','the pots and plants being for the sake of simplicity shown only in Fig. 3.

In the apparatus of Figs. 2 and 3 the troughs 1 are distributed and rested on two vertically spaced bed sections arranged straight above one another and having the same lengths, the lower bed section being formed by a first group of spaced apart, parallel beams 5A, and the upper bed section being similarly formed by a second group of spaced apart beams 5B. The beams 5A and 5B are supported by a common post-and-beam structure generally designated by 6 and extend substantially horizontally in a direction perpendicular to the longitudinal directions of the elongate parallel troughs 1. The lengths of the beams must well exceed the combined widths of the troughs to be received thereon and may in practice frequently be in the order of fifty to a hundred meters, whereas the lengths of the troughs 1 for practical reasons preferably should not exceed about ten meters.

At a suitable height above each bed section 5A and 5B, respectively, there are provided a plurality of lamps 7 having light sources capable of emitting a growth promoting radiation evenly over the plants to be grown. If the apparatus is used in a greenhouse covered with light admitting material the lamps above the upper bed section 5B may be switched off during daytime or be entirely dispensed with.

Each group of beams 5A and 5B forming the respective bed sections is so adapted and designed that the troughs 1 resting thereon will slightly slope in their longitudinal direction towards one side of the apparatus as illustrated - in Fig. 3. Above the upper ends of the sloping troughs 1 there is provided along the length of the respective bed section a tube 8 through which nutrient solution is pumped out from a source not shown and distributed to the various troughs through spout-like outlets 9, possible waste solution being collected in a first longitudinally extending chute 10 mounted immediately below. A similar, second longitudinally extending chute 11 mounted along the lower ends of the troughs takes care of the excess of nutrient solution having passed through the various troughs. The waste and excess solutions may be returned for recirculation to the source from which the tube 8 is supplied. The entire system for distributing and recirculating nutrient solution is old in the art and should need no further elucidation.

The troughs 1 are all freely rested on their respective bed sections and adapted to be individually displaced in sliding contact with the latter in a direction perpendicular to the troughs. Such displacement of each individual trough on each of the two bed sections is carried out by means of a single motor-driven carriage 12A and 12B, respectively. Each such carriage comprises an elongate, rigid truss structure 13 entending over the full width of its respective bed section in a direction generally parallel to the troughs I thereon. At its respective ends said truss structure 13 has wheels 14 rolling on a pair of guide tracks 15 extending along the length of the bed section, one on each side thereof, but being separated therefrom and supported by the post-and-beam structure 6. Each carriage 12A and 12B, respectively, is free to be independently reciprocated along the full length of its respective bed section 5A and 5B well above the troughs 1 and under the lamps 7, as shown in Fig. 3.

The respective carriages 12A and 12B are independently driven by suitable motors, not shown, to move at only a moderate speed, usually only a few meters per second, so that they can readily be halted in accurately selected positions along their respective bed sections. The manner in which they are driven is not important, but suitable measures must be taken to assure that they always maintain their positions parallel to the troughs. Thus, for example, each carriage may carry one or several remotely controlled electric motors driving suitable gears engaging with racks on the guide tracks 15, or each carriage may by means of a suitable system of ropes or chains be pulled backwards and forwards as required by stationary motors. Other driving alternatives well known per se may also be resorted to if so desired.

Each carriage 12A and 12B, respectively, has a plurality of driving dogs 16 mounted on its truss structure 13 in substantially uniformly spaced positions therealong. These driving dogs 16 of each carriage are vertically adjustable in unison relative to the truss structure 13 by remotely controllable means, such as electrically or pneumatically operated actuators, in order to occupy either an elevated position, shown in the lower right hand corner of Fig. 2 and in Fig. 3, or a lowered position, shown in the upper left hand part of Fig. 2. In their elevated positions the driving dogs 16 are able to freely pass over the troughs 1 resting on the related bed section 5A and 5B, when the carriage is reciprocated along the latter, whereas in their lowered positions they are able to drivingly engage any selected one of said troughs from above.

In the apparatus shown in the drawings the driving dogs 16 are frusto-conical in shape, thus resembling the pots 2 in which the plants to be grown are contained, and, when _beinz lowered, they are adapted to seek themselves into and to thus enter the trough to be driven from above in order to thereby stabilize said trough and prevent it from tumbling over when the same is moved by the carriage in sliding contact with the bed. It is to be noted that all the driving dogs 16 of each carriage 12A or 12B are arranged to engage only one trough 1 at a time, and the number of driving dogs l6 must be sufficiently high in relation to the stiffness of the troughs to make certain that the troughs are not subjected to undue lateral bending during their sliding movements over the bed. If so desired, there may be provided two independently and alternatingly operable sets of driving dogs on each carriage, one on each side of the truss structure thereof, so that one of said sets may be used when the carriage is operative over one end portion of its related bed section, and the other set may be used when the carriage is operative over the opposite end portion of the bed.

As will be readily understood, any selected trough 1 on any one of the two bed sections may be moved by first positioning the related carriage in a manner to let its driving dogs engage the trough and by then lowering said driving dogs and repositioning the.carriage, before the driving dogs are again disengaged from the trough. Since the trough is moved in sliding contact with the bed, the carriage will not be loaded by the weight of the trough, and the vertical position as well as the slope of the trough will remain unchanged throughout the operation. In order to increase the lateral spacings between the troughs when their positions on the bed are changed, the troughs must be individually moved in succession, and, of course, no trough should be repositioned unless the bed is free from other troughs over the full distance each trough is to be moved.

As best appears from Fig. 2, at each end of the two bed sections 5A and 5B there is provided an elevator 17A and 17B, respectively, these elevators being identical but mirror-reversed. Each such elevator comprises a shelf- like elongate platform 18 supported by two brackets 19 each of which is guided in a hollow column 20. The two brackets 19 are vertically movable in synchronism by motorized lifting mechanisms not shown because they are sheltered in the respective columns 20 but being of any suitable kind well known per se. The platform 18 is adapted to receive thereon a single trough at a time and has a length slightly exceeding that of the troughs 1. The platform 18 is arranged to move vertically along a path very close to the ends of the two bed sections 5A and 5B between a lower position, in which its top surface forms an extension of the bed section 5A, and an upper position, in which its top surface forms an extension of the bed section 5B.

The elevator 17A at one end of the apparatus is used to lift the troughs 1 one by one from the lower bed section 5-4 to the upper one 5B, whereas the elevator 17B at the opposite end thereof is used to lower the troughs from the upper bed section to the lower one, it being understood that each trough so lowered may then be emptied of matured plants and reloaded with potted seedlings while still resting on the lowered platform 18 for maximum convenience. The troughs to be lifted, and lowered respectively, are moved over to and removed from the platform 18 of the respective elevator by means of the carriages 12A and 12B in generally the same manner as they are repositioned on the bed sections as previously described.

In order to make such transfers of the troughs possible in the apparatus shown in the drawings, the tracks 15 for each carriage 12A and 12B are somewhat longer than the bed sections 5A and 5B and project with their respective end portions beyond the ends of the bed sections, so that each carriage may be moved to end positions in which its driving dogs 16 are situated in the path of the platform 18 of the elevator to be employed. Of course, as far as the lower carriage 12A is concerned, the same must then be removed from its respective end positions before the corresponding elevator 17A or 17B is operated.

The sequence of operation of the apparatus as a whole will be best understood if considered to be started from a situation similar to the one illustrated in Fig. 1, where the plants of the troughs 1 resting on the left hand portion of the upper bed section 5B are ready to be harvested and there is a free space for receiving the lowered and replenished troughs at the left hand portion of the lower bed section 5A. To begin with, the troughs on the upper bed section 5B containing matured plants are moved one by one in succession and by the upper carriage 12B to the elevator 17B to be lowered, emptied and replenished, whereupon they are pulled in by the lower carriage 12A on the free space of the lower bed section. When all the troughs containing matured plants have thus been transferred to the lower bed section 5A, they leave a similar, but in fact larger; free or empty space to the left of the upper bed section 5B.

Now the upper carriage 12B is first employed to successively reposition all the variously grouped troughs on the upper bed section 5B so that a free space, this time somewhat reduced, will result on the right hand portion of said upper bed section, to which troughs from the right hand end portion of the lower bed section 5A can be transferred, again one by one, by combined operations of both the two carriages 12A and 12B and the elevator 17A. This will leave a somewhat smaller free space on the right hand end portion of the lower bed section 5A which is in turn utilized for repositioning by means of the lower carriage 12A all of the troughs now resting on said lower bed section 5A until the situation is again the same as at the start of the entire cycle. Although such stepwise advance or repositioning of all the troughs through the apparatus may take a considerable time, this is no inconvenience since it will only be necessary to carry out the procedure once - a day or even less frequently but, of course, preferably in connection with the harvesting of matured plants.

In practice the movements of the carriages 12A and 12B and of the elevators 17A and 17B as well as the proper adjustments of the driving dogs 16 of the respective carriages are all automatically governed by means of preferably computerized control aids, so that no human attention will be needed for such purposes.

It should be readily understood that the apparatus here described and illustrated in a somewhat simplified manner in the accompanying drawings is only intended to serve as an example and may be subject to various modifications as to details within the scope of the appended claims.