GB2313387A - Greenhouse - Google Patents

Abstract

A weather-resistant plant-growing enclosure to replace conventional greenhouses and consisting of a line of arched supporting members (10) anchored in the ground at spaced intervals and clad with a plastics membrane (17) of sufficient thickness to be durable and weather resistant while capable of transmitting the necessary frequencies of sunlight to afford the required growing conditions for vegetation planted within the structure. The structure is made up of arched and straight lengths of plastics tube (10, 12) all connected together with screws or connectors (20, 23) and readily assembled and dismantled. The structure is maintained upright by bracing members or tie bars (15) extending between each end arched member (10) and an adjacent arched member (10). The structure is anchored to the ground by pins (11) inserted into the base regions of the arched tubular members (10), and set in the ground.

Description

GROWING ENCLOSURES THIS INVENTION concerns weather-resistant plant-growing enclosures, and is particularly concerned with structures which replace conventional greenhouses. One such known structure is often referred to as a "polytunnel" and consists of a line of arched supporting members anchored in the ground at spaced intervals and clad with a plastics membrane of sufficient thickness to be durable and weather resistant while capable of transmitting the necessary frequencies of sunlight to afford the correct growing conditions for vegetation planted beneath the structure. Such structures may be used for agricultural and horticultural purposes, and the arched members are usually produced from tubular steel formed into generally semicircular supports anchored into the ground at the base and linked together at the top of the structure by one or more ridge members or purlins. The number and spacing of the arched members determine the overall length of the enclosure which may be further strengthened by the addition of timber or metal frameworks at the respective ends of the structure and by diagonal struts or ties to maintain the arch members in an upright configuration.

Polytunnels made as described above are heavy and cumbersome and cannot readily be packaged and transported for domestic or DIY assembly. The present invention seeks to overcome this difficulty.

According to the present invention there is provided a growing enclosure comprising at least two arched supporting members to be anchored upright in spaced relationship in the ground and to be clad with a plastics membrane to form opposed end walls, arched side walls and a roof, with at least one inclined bracing member to be attached to and extend between said supporting members to maintain them upright, and at least one ridge member or purlin to be attached to and extend between the supporting members in the uppermost region thereof; characterised in that each supporting member is provided in the form of at least two lengths of plastics tube and means for connecting them together in longitudinal alignment to form an arch.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figs. 1 and 2 are end and side elevations respectively of a polytunnel of the type to be described; Fig. 3 is a horizontal cross-section taken on line III-III of Fig. 1, illustrating a feature required with a conventional polytunnel; Fig. 4 is an enlarged view taken at position A of Fig. 1; Fig. 5 is an enlarged view taken at position B of Fig. 1; and Figs. 6 and 7 are perspective views respectively of two connectors to be used in the assembly of the polytunnel.

The structure consists of spaced upright arched members 10 anchored by pins 11 at the base of each member, and attached to a common purl in 12 to form the ridge of the structure. Inclined bracing members or tie bars 15 are attached at 13a to one or more pairs of the arched members 10 to maintain them in a vertical configuration.

Typically, a timber framework 14 is provided at or adjacent one or both ends of the structure for additional rigidity and to provide an end support. This may also form a frame for a door.

The entire structure is clad with a plastics membrane 17 forming the arch or tunnel of the structure and secured or buried, in the regions of the pins 11. A similar or the same membrane provides a closure at each end.

Conventionally, the arched members and purl in are made of steel or a metallic alloy and, become very hot in summer causing the plastics membrane 17 to melt or stretch, or in winter becoming very cold and acting as a heat sink causing the membrane to become brittle and crack where it touches the steel members. To overcome this problem it is common to place a strip as shown at 16 in Fig. 3 of a thermally insulating material on the outer surfaces of the arches and purl in to prevent the membrane from touching the metal surfaces.

In accordance with the present invention a structure of similar kind is produced in which the arched members 10 are produced from a lightweight plastics tubing such as PVC having an internal diameter in the region of 30mm. The members 10 are not preformed into complete arches but rather are supplied as two or more straight lengths which by the nature of the material can be bent to shape during assembly. As illustrated in Fig. 1, in one embodiment, each arched member 10 is preferably made up from three lengths of tubing 10a, 10b, 10c each representing approximately one third of the extent of the arch, and these are secured together in longitudinal alignment by tubular connectors 20, engaging the respective tube ends with a friction fit and secured if necessary by screws or a suitable adhesive.

As illustrated in Fig. 4 the lowermost ends of each arched member 10 are secured to the ground by pins 11 which may be located in concrete or be of sufficient length to be driven into the ground to provide adequate support for the arched member. The length of each pin 11 above the ground is selected such that the sides of the arched member assume a substantially vertical attitude as indicated in Fig. 1 to a height equivalent to approximately one half of that of the structure.

Referring now to Fig. 2, it will be seen that the ridge member or common purlin 12 extends along the top of the structure and is attached to the arched members 10 at each end thereof by a screw driven through the purl in and into the arched member.

Alternatively, or in addition, as illustrated in the right-hand end of Fig. 2 the purlin may be received within a tubular socket 22 which itself is attached to the underside of the adjacent arched member.

The purl in is provided in individual lengths which are joined beneath intermediate arched members 10 by way of a tubular sleeve or socket 23 which may be attached to the adjacent arched member either by way of a screw or by way of flexible tie members 24 wrapped around the tubular socket and the adjacent arched member to maintain the socket tight against the underside of the arched member.

Also as can be seen from Fig. 2, the bracing members or tie bars 15 are produced in the form of two aligned lengths of steel strut 25 and 26 joined by a sleeve 27 and attached by screws 28.

The remote ends of the tie bars 15 are connected to the adjacent arched members by connectors 29 of the type illustrated in Fig. 6. It will be appreciated that the position at which the upper end of the inclined tie bar 15 is attached to its adjacent arched member may be part way around the curvature thereof and so the provision of the sleeve 27 permits one part of the tie bar 15 to be rotated with respect to the other about a longitudinal axis before being connected tightly together by the screws 28. Without the tie bars being split in this way they would need to be "handed" but the adjustment provided by the sleeve 27 enables the provision of a single type of tie bar for all corners of the structure.

Referring now to Fig. 5 the upright frame members 14 at the or each end of the structure are attached to the adjacent end arched member 10 by means of the brackets or connectors 30 illustrated in Fig. 7. These are passed onto and around the arched member to approximately the correct positions and subsequently screwed or bolted to the upright frame members 14.

The membrane or skin 17 is laid over the structure and may be folded back at the base on each side of the structure to form sealed open pockets which, in use, would fill with rainwater and thus help to retain the membrane in place. Such pockets thus also provide a supply of water to be used for the plants. If the structure is located on a particularly windy site, part of the pockets may be located in trenches backfilled to provide anchorage.

The framework 14 at one or each end of the structure may be produced from further lengths of plastics tubing or other nonmetallic structural materials as appropriate.

With the polytunnel supporting structure made largely from a tubular plastics material it is possible to use the structural members as ducts to carry water for irrigation. For example, the purlin 12 may be perforated such that water may be pumped periodically therethrough to water the plants at predetermined intervals.

The structure may incorporate a soil containment tray located at say 75cm from the ground providing a soil depth of 200mm whereby the device may be constructed for use by disabled or wheelchair-bound persons with access by way of a door produced from a sheet of the cover membrane located in sliding engagement with an end supporting arch, or on runners mounted on a rail.

It will be appreciated that by producing a polytunnel or support structure from tubular plastics material the need for thermally insulating strips such as those illustrated at 16 in Fig. 3 is avoided, and the tubes themselves can be used to carry water for irrigation without the risk of corrosion. Adequate structural support is provided with a significant reduction in weight when compared with steel tubes, and the device may be assembled with shorter basic lengths and smaller parts which may be packaged in such a way that they can be made available practically and economically to the DIY trade.

While in Fig. 2 the structure is illustrated for convenience as consisting of two end arched members and one central arched member, the length of the structure may be extended to include several more arched members e.g. four or five. In this case the tie bars 15 need be provided only between each end arched member and the next adjacent member, the remainder of the structure being adequately braced thereby.

The entire structure is produced from a number of manageable-sized members readily connected together by push-fit assembly and screws and easily packaged for transportation and storage producing a lightweight and rigid structure which may be readily erected and dismantled. The life of the cover sheet material is prolonged by avoiding contact with hot or cold surfaces, and the assembled structure provides a weather-resistant shelter for providing a highly suitable growing environment for flowers, vegetables and other plants.

Claims (9)

1. A growing enclosure comprising at least two arched supporting members to be anchored upright in spaced relationship in the ground and to be clad with a plastics membrane to form opposed end walls, arched side walls and a roof, with at least one inclined bracing member to be attached to and extend between said supporting members to maintain them upright, and at least one ridge member or purlin to be attached to and extend between the supporting members in the uppermost region thereof; characterised in that each supporting member is provided in the form of at least two lengths of plastics tube and means for connecting them together in longitudinal alignment to form an arch.

2. A growing enclosure according to Claim 1, wherein each arched supporting member is anchored to the ground by pins adapted to be inserted in the opposed ends of the supporting member and to be anchored in the ground.

3. A growing enclosure according to Claim 1, including an upright framework at least at one end of the structure and disposed beneath an adjacent end arched member and attached thereto by removable connectors.

4. A growing enclosure according to Claim 1, wherein said at least one inclined bracing member is provided in the form of two aligned struts each being rotatable during assembly relative to the other strut about a longitudinal axis of the member.

5. A growing enclosure according to Claim 1, wherein said at lest one inclined bracing member is adapted to be fixed to one supporting member and rotatable about a longitudinal axis with respect to another said supporting member.

6. A growing enclosure according to Claim 1, wherein the means for connecting said at least two lengths of plastics tube together comprises a tubular sleeve adapted to engage the respective adjacent ends of the two lengths of plastics tube.

7. A growing enclosure according to Claim 1, wherein said at least one ridge member or purlin comprises a plurality of lengths of plastics tube connected together in longitudinal alignment.

8. A growing enclosure according to Claim 1, wherein said at least one ridge member of purlin is attached to the underside of the respective arched members.

9. A growing enclosure substantially as hereinbefore described with reference to and as illustrated in Figs. 1, 2 and 4 to 7 of the accompanying drawings.