GB2101663A

GB2101663A - A greenhouse ventilator

Info

Publication number: GB2101663A
Application number: GB08112671A
Authority: GB
Inventors: Gillian Maureen Fitzpatrick; William Stanley Fitzpatrick
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-04-24
Filing date: 1981-04-24
Publication date: 1983-01-19
Also published as: GB2101663B

Abstract

A ventilator for the plastics sheeting wall of a tunnel-type greenhouse (11), includes a frame (19) forming a border for an opening in the sheeting, each limb (19a, 19b, 19c, 19d) of the frame being formed from two cooperating parts, (1, 2) which interengage to trap the sheeting between them to reinforce the edge of the opening. The frame (19) comprises independent limbs (19a, 19b, 19c, 19d) coupled by resilient couplings at the corners of the frame (19) to permit flexing of the sheeting as this is moved by the wind thereby avoiding tearing where the ventilator opening is formed. <IMAGE>

Description

SPECIFICATION A ventilator The present invention relates to a ventilator, and particularly to a ventilator for ventilating a space enclosed by a relatively flexible membrane.

In particular, the present invention finds utility in connection with tunnel-type greenhouses the cover of which is usually made from a transparent flexible plastics material which, because of its flexibility, presents a number of problems for the provision of ventilators. For example, the plastics wall of the tunnel-type greenhouse, apart from the two flat ends, is curved and supported only on spaced hoops. For this reason ventilators have previously only been provided at the ends of such tunnel-type greenhouses since it is only at these ends that a flat wall and sufficiently strong support for the ventilator was available. It was though that the curved plastics material wall of the main part of the tunnel would provide inadequate strength to support a ventilator, or that, because of its flexibility, it would tear where a ventilator opening was formed.This belief was reinforced by the fact that traditional materials for the manufacture of the frame and cover of a ventilator are relatively heavy. For example, a wooden frame or even a frame made from aluminium section would be considered too heavy to be supported solely by the plastics material which is under slight tension in order to form it to its curved tunnel-like shape.

Ventilator openings at the ends of the tunnel, however, even if of relatively large dimensions, do not have the same ventilating effect as an opening at or near the top of the curved section of the tunnel, since an end ventilator cannot take advantage of the convection effect due to the heating of the space within the greenhouse. For this reason it has been necessary to install means for forced circulation of the air within a tunnel greenhouse, or to site them in such a way that they extend along the direction of the prevailing winds to that advantage can be taken of these to create air circulation within the greenhouse area in order to prevent over heating.

In conventional glass greenhouses where a plurality of panes of glass are supported on rigid frames, it is possible to provide ventilator openings at or near the top of the greenhouse so that when the temperature conditions within the greenhouse should rise to a level which is too great for the plants growing therein, it is a simple matter to open the ventilators and allow excess hot air to vent to the atmosphere simply by convection, cooler air being drawn in through the openings at or adjacent the ground level, or simply through the gap between the door and its frame. Partial opening of the ventilators can allow a degree of controllability in the temperature of the interior of the greenhouse when the excess temperature is not so great as to require full ventilation.A disadvantage of tunnel-type greenhouses in the past has been that relatively little control of the ventilation is possible since, even with a forced circulation fan, the degree of circulation within the greenhouse has been relatively limited; such fans are not usually provided with speed controls and are either switched on or off so that any degree of control of the air circulation has to be effected by running the fans for a short period and allowing a period when they are switched off. This requires constant supervision, and, particularly for an amateur, is not possible because of the constant attention required.

The present invention seeks to provide a ventilator which can be fitted to a flexible membrane such as the cover of the tunnel-type greenhouse, which will provide adequate ventilation because it can be positioned at any required height and at any location along the greenhouse, and which avoides the disadvantages of the previous ventilation systems for such greenhouses.

According to one aspect of the present invention there is provided a ventilator for a flexible membrane (such as the plastics sheeting wall of a polythene tunnel-type greenhouse) including a frame forming a border for an opening in the membrane, in which each limb of the frame is formed from parts which trap the flexible membrane between them to reinforce the edge of the said opening.

The limbs of the frame are preferably shaped to cooperate with one another to trap the membrane between them and it is envisaged that the two parts of each limb may be made from an integral moulding and hinged together along a line extending parallel to their length, for example, by means of one or more ligament hinge, so that the two parts can be folded over and clipped over the edge of the opening in the membrane when forming the reinforcing frame.

Indeed, it is preferred that the limbs of the frame are snap engageable together with the membrane between them so that the parts of the membrane can be fitted together immediately without requiring any further operations such as adhesive or the application of fixing means. The limbs of the frame may be formed by parts which together constitute a closed box-section member or may have some other form.

The limbs of the frame may be rigid or flexible and in either case there may be provided cornerconnecting members for connecting the ends of adjacent limbs of the frame together to form a corner.

If the connections between adjacent limbs of the frame are non-rigid this will permit the reinforcing frame to accommodate at least a limited flexure of the membrane which may occur after the frame has been fitted. Likewise, if the limbs of the frame are able to flex, at least to a limited extent, the ventilator opening will not constitute a rigid region within the otherwise flexible sheet. Likewise, if the frame parts are made from a lightweight plastics material the weight of the ventilator can readily be borne by the flexible membrane even if the ventilator frame is fitted at the furthest possible point from the nearest support hoop.

Conveniently the parts which constitute each limb of the frame comprise substantially channel section member and a cover member, the former having inwardly facing limbs and the latter having outwardly directed flanges which engage under the said lips when the parts are fitted together. In order to be best adapted for mounting on a polythene tunnel it is convenient if two opposite limbs of the frame are curved in parallel planes such that the area bounded by the fame constitutes a part of a cylinder. Such a frame then matches the curvature of the membrane forming the cover of the polythene tunnel.

Preferably there is further provided a closable ventilated cover member attached to the frame, and means for selectively holding the said cover member in a closed or an open position.

Conveniently the said means for selectively holding the cover member in an open or closed position is able to hold the said cover in a pluraíit of different opening positions in order to gain the advantage of graduated opening discussed above The cover member is conveniently formed from the panel removed from the membrane when cutting the opening which is reinforced by the above defined ventilator frame. Such panel can be supported at its edges by a rigid or flexible reinforcing frame formed in the same manner as the ventilator opening frame with each limb being constituted by snap engageable component parts secured together at the corners by suitable corner reinforcing elements. The two frames can be hinged together along one side and provided with a stay or strut for holding the cover open.

The present invention also comprehends a tunnel-type greenhouse having a flexible plastics material cover, provided with at least one ventilator as defined hereinabove comprising an opening reinforced by a ventilator opening frame and provided with a cover which can be held in a closed or open position to close or open the ventilator.

In another aspect. he resent invention is constituted by a method of providing a tunneltype greenhouse having a flexible plastics material membrane cover, with at least one ventilator in the curved wall thereof. the method including the steps of: cutting an opening in the curved wall of the flexible membrane: positioning at least the outer part of at least one limb of a frame for the opening by passing it through the opening and locating it along the edge of the opening which it is intended to reinforce: bringing up the co-operating part of the limb of the frame from within the greenhouse and inter-engaging the two parts with the edge of the opening in the membrane trapped therebetween.

The method of the present invention also includes the steps of repeating the above process for each limb and, prior to positioning the outer part of the second or subsequent limb of the frame. interposing a corner-reinforcing member at least at one end of the limb.

Alternatively, the outer frame parts may all be positioned and assembled together before being offered up to the opening, the half-frame then being passed through the opening in the membrane and located over the membrane ready to have the other frame members assembled thereto. In this way the operator fitting the ventilator can work entirely from within the tunnel, which facilitates the provision of such ventilators to existing tunnels.

One embodiment of the present invention will now be more particularly described, by way of example. with reference to the accompanying drawings. in which: Figure 1 is a perspective view of a tunnel-type greenhouse having a flexible plastics material membrane cover showing the general location of the ventilator formed according to the principles of the present invention: Figure 2 is a perspective view, on an enlarged scale, of a ventilator fitted to a membrane. partly cut away to show the construction of the reinforcing frame' and Figure 3 is a cross sectional view taken on the line llllll of Figure 2 illustrating the manner in which the membrane is trapped in between the frame parts.

Referring now to Figure 1 the tunnel-type greenhouse illustrated is generally indicated with the reference numeral 1 This greenhouse comprises a plurality. in this case, four, semicircular support hoops 1 2 over which is stretched a flexible plastics material cover 13. At the ends of the greenhouse there are two semi-circular flat panels 14, 1 5 one of which (panel 1 5) has a door frame 1 6 inserted therein carrying a door 1 7.

For ventilation of the tunnel 11 a ventilator 18 is provided midway along its length and in the upper or roof portion of the membrane 13. The ventilator is shown in greater detail in Figure 2, and comprises a ventilator opening frame 19 to which is hinged a ventilator cover 20 which can be held in any one of a number of open positions by a stay 21.

The ventilator opening frame 19 is generally rectangular. comprising four straight limbs 1 9a, 1 9b, 1 9c, 1 9d each being connected by mitred corners to its neighbours. Within each mitred corner there is located a corner reinforcing element (not shown, Each limb of the ventilator opening frame 19 is composed of two parts between which the adjacent edge of the membrane 13 is trapped. As can be seen in Figure 3, which illustrates a limb 1 9d, the frame comprises a lower or channel section part 1 9d'1 and an upper or cover section part 1 9d/2, The channel section part 1 9d/2 has inwardly facing lips 22 along the slot of the channel. and the cover portion 1 9d/2 has two parallel ridges 23, 24 from which project lateral flanges 25 26 respectively. When the two frame parts 1 9d 1 and 1 9do2 are fitted together the arms of the channel section part 1 9d/l flex outwardly to allow the lateral flanges 25, 26 to pass between them and then snap inwardly to locate between the cover 1 9d/2 and the lateral flanges 25, 26 to locate the cover portion in position and hold the two parts together. As can be seen from Figure 3 the edge of the membrane 13 is trapped between the two members 1 9d/1 1 9d/2 and held firmly in position by engagement thereof. The provision of two snap engagement members provides two lines along which the edge of the membrane is held in order to reduce the risk of tearing. The material from which the frame limbs are made is preferably a lightweight plastics material so that the weight of the frame on the membrane 13 is very small. Even if the membrane should flex due to variations in wind conditions, the frame 19 will not cause tearing since the edges of the opening are reinforced and, moreover, the corner connecting elements can be so formed that they allow the frame a degree of flexural resilience to accommodate flexure of the membrane 13.

When the ventilator is being fitted it can conveniently be positioned from within the tunnel by first cutting the opening and then positioning the frame parts around the opening from within the tunnel, passing those elements which are to be located outside the tunnel through the opening and clipping them together from within the tunnel.

Claims

1. A ventilator for a flexible membrane (such as the plastics sheeting wall of a polythene tunneltype greenhouse) including a frame forming a border for an opening in the membrane, in which each limb of the frame is formed from parts which trap the flexible membrane between them to reinforce the edge of the said opening.

2. A ventilator as claimed in Claim 1, in which the limbs of the frame are each formed in two parts shaped to cooperate with one another to trap the membrane between them.

3. A ventilator as claimed in Claim 2, in which the said two parts of the limbs of the frame are snap engageable together with the membrane between them.

4. A ventilator as claimed in any preceding claim, in which the limbs of the frame are formed by parts which together constitute a closed boxsection limb member.

5. A ventilator as claimed in any of claims 2, 3 or 4, in which there are provided cornerconnecting members for connecting the ends of adjacent limbs of the frame together to form a corner.

6. A ventilator as claimed in Ciaim 5, in which the connections between adjacent limbs of the frame are non-rigid whereby to accommodate at least a limited flexure of the membrane occurring after the frame has been fitted.

7. A ventilator as claimed in any of Claims 2 to 6, in which the parts which constitute each limb of the frame comprise a substantially channel section member and a cover member, the former having inwardly facing lips and the latter having outwardly directed flanges which engage under the said lips when the parts are fitted together.

8. A ventilator as claimed in any preceding claim, in which two opposite limbs of the frame are curved in parallel planes such that the area bounded by the frame constitutes a part of a cylinder.

9. A ventilator as claimed in any preceding claim, in which there is further provided a closable ventilator cover member attached to the frame, and means for selectively holding the said cover member in a closed or open position.

10. A ventilator as claimed in Claim 9, in which the said means for selectively holding the said cover member in an open or a closed position is able to hold the said cover in a plurality of different open positions.

11. A ventilator for a flexible membrane, substantially as hereinbefore described with reference to the accompanying drawings.

12. A tunnel type greenhouse having a flexible plastics material cover, provided with at least one ventilator as claimed in any preceding claim.

13. A method of providing a tunnel-type greenhouse having a flexible plastics material membrane cover, with at least one ventilator in the curved wall thereof, including the steps of: cutting an opening in the curved wall of the flexible membrane; positioning at least the outer part of at least one limb of a frame for the opening by passing it through the opening and locating it along the edge of the opening which it is intended to reinforce; bringing up the cooperating part of the limb of the frame from within the greenhouse and interengaging the two parts with the edge of the opening in the membrane trapped therebetween.

14. A method as claimed in Claim 13, including the steps of repeating the process for each limb and, prior to positioning the outer part thereof, interposing a cover-reinforcing member at least at one end of the limb.

15. A method as claimed in Claim 13, in which the outer frame parts are all relatively positioned and assembled together outside the opening prior to connection thereto of the inner frame member, the partly assembled outer frame being passed through the opening so that the operator can work entirely from within the tunnel.

1 6. A method of providing a tunnel-type greenhouse with a ventilator, substantially as hereinbefore described with reference to the accompanying drawings.