GB2228973A

GB2228973A - Ventilation of cloches

Info

Publication number: GB2228973A
Application number: GB9000366A
Authority: GB
Inventors: Edward Lawrence Crompton
Original assignee: GRIMALDER Ltd
Current assignee: GRIMALDER Ltd
Priority date: 1989-01-07
Filing date: 1990-01-08
Publication date: 1990-09-12
Also published as: GB8900327D0; GB9000366D0

Abstract

A cloche 1, Fig. 1, has hoops 3 covered by a sheet 5, e.g. of polyethylene, which is clamped in channel-section members 5, 7, 9, 11 by inserts. A ventilator, of similar channel-sheet construction, is positioned between members 7, 9 and is bodily raisable, Fig. 3, on scissors linkage 29 by wire or rod 43. Alternatively, a pivoted ventilator may be raised at one side by such scissors linkage. <IMAGE>

Description

Title: Ventilation of Polyhouses DESCRIPTION The present invention relates to the ventilation of Polyhouses including a ventilator for a Polyhouse and a Polyhouse provided with the ventilator.

Polyhouses have established themselves as economical way for covering relatively large areas of ground for such as horticultural purposes. They consist of longitudinally spaced hoops or the like, usually interconnected by longitudinal runners, and over which hoops is fitted a covering, usually of sheet material such as Polyethylene to form what is in effect a covered tunnel having one or more spans. Fixing such sheeting in position does present difficulties and therefore it has long been the practice to minimise the number of fixing locations and one way of doing this is to present the covering in continuous sheets extending over the hoops and merely located along opposite longitudinal edges.The provision of such continuous sheeting does create problems with providing adequate ventilation in such Polyhouses and historically sacrifices have been made to ventilation requirements by dispensing with roof vents which are typical of glass houses and relying on ventilation from the ends and/or side ventilation, This avoids aperturing of the covering and the insertion of additional framing for securing the covering along sides of the aperturing and that then keeps down the cost of construction and avoids sacrificing the integrity of the one piece covering. Where small areas are concerned end or side ventilation is tolerable, but for larger areas unacceptable temperature gradients can result.

Accordingly there is a requirement for a ventilation system which is more efficient and yet which does not compromise the economical construction of a Polyhouse nor introduce problems with membrame fixing.

According to one aspect of the present invention then there is provided a ventilator construction for a Polyhouse comprising a movable framework and actuating means for the framework, and wherein the actuating means operates on a scissor action.

According to another aspect of the invention there is provided a Polyhouse construction comprising a plurality of longitudinally spaced hoops having applied thereover a covering of sheet material, and where the passage of the sheet material over the hoops is interrupted by spaced longitudinal members to which the sheet material is secured, and where a ventilator is positioned between those spaced members running lengthwise along the Polyhouse, either spaced at intervals along the length of the house or more preferably as a continous run.

The provision of the longitudinal member provides for interruption of the skinning at any desired location in the span, but we prefer to place the ventilator at centrally, straggling the apex of the house. A particular convenient implementation, although not essential arises where the longitudinal member takes the form. of an open channel member, formed for example from sheet steel, strip or plate, bent in to the required shape, as this can be constructed sufficiently strongly to permit fixing directly to the spaced longitudinal hoops. Membrame fixing is then provided by inserting a retention member into the open mouth of the channelling with the membrame disposed therebetween and which is thereby drawn into the channel.

Where the sheeting to be fixed in position is a relatively flexible membrane of polyethylene then we find that a particular convenient retention member takes the form of elongate batten of wood or other material with similar compliant surface properties which does not damage the membrame material on insertion into the channel member. Certain plastics material can suffice in this regard. The insert member is preferably dimensioned to fit snugly within the channel member so that the membrame is trapped between cooperating parts of the channel and the retention member.It will be understood then that the membrame is caused to be deflected into the channel member and around the insert member such that it resists pulling out.It is further preferred to have means for securing the retention member in position and for the case of a wood batten this can be convenient done by screws passing through a hole in a base part of the channel and being screwed into the wooded batten.

For less flexible materials the retention member will take the form of a more robust elongate member, possibly made from pressing from sheet metal and in a general top hat section in cross section to reflect the shape of the channel and a protruding part for fitting into the channel with clearance to allow for introduction of the less flexible sheet material in to the channel member with deflection on fixing of the retention member such as by nuts and bolts between the channel member and retention member.

It is preferred for the channel member to have a radiused edge to its open mouth at least to one side and preferably to both sides which edge allows for drawing in of the sheet material without damage thereto. The above described fixing provides a particularly effective means of fixing the edge of the covering material and thereby allows for interruption of the material in its passage over the hoops.

The preferred ventilator comprises a framework of a size at least equal to the spacing between the spaced longitudinal members of the Polyhouse so as to provide for blocking the opening in the Polyhouse or providing a ventilation opening according to the position of the framework. The framework can be constructed in discrete lengths spaced at intervals along the length of the Polyhouse with intervening spaces filled in by fixed covering material, or may form a continuous frame running the length of the Polyhouse. The opening movement of the framework may be arranged as a hinging action from one edge of the framework or from an end thereof but it is much preferred if the framework operates with a lifting action so as to provide maximum ventilation on opening.That can be achieved in a particularly effective manner if the actuating means operates on a scissor action principle with two or more scissor action mechanisms disposed along the length of the Polyhouse and interconnecting the framework with structional members of the Polyhouse. A particularly advantageous construction arises where the aforedescribed longitudinal channel member of the Polyhouse carries the scissor actuating mechanism.

A further advantage arises from constructing lengthwise members of the framework from a longitudinal channel member constructed in the same or similar manner to that of the longitudinal channel member of the Polyhouse and where a similarly constructed insert member is used for holding in place skinning for the moveable framework such as polythene sheeting although other conventional frame member materials can be used.

That part of the scissor mechanism which connects with the framework can then be arranged to be supported from such longitudinal channel members of the framework.

The present invention will now be described further hereinbelow, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a perspective view of a Polyhouse incorporating a ventilator; Figure 2 is an end view showing part of a Polyhouse with ventilator; and Figure 3 is a side view of scissor mechanism for actuating the ventilator.

Referring to the drawings there is shown a Polyhouse, generally indicated as 1, and comprising a plurality of longitudinally spaced hoops 3 which are linked together by longitudinal channel members 5, 7, 9, and 11. The longitudinal channel members 7 and 9 are positioned centrally straggling the apex of the hoops to define the position of a ventilator 13 running the length of the Polyhouse. Between the pairs of longitudinal members 5, 7, 9, and 11 is positioned sheeting material 15 which is drawn taut by the action of insert members 17 which serve to fix the sheet material 15 at the longitudinal channel members 5,7,9, and 11.

It will be seen from Figure 2 that the channel members 5,7,9 and 11 are open to one side and are provided with a flange entry as at 19 which is radiused to avoid damage to the sheet material. The longitudinal members are secured to the hoops 3 by any convenient means.

The ventilator 13 comprises a framework made up of longitudinal members 21 which conveniently, as shown, corresponds in design to the longitudinal members 5,7,9 and 11 in so far as they are open channel members flanged at their mouth to receive a membrame 23 and a corresponding complimentary insert member 25.

The longitudinal members are spaced by traverse members 27.

The actuating mechanism for the ventilator comprises a scissor mechanism 29 having two equal length limbs 29a, 29b which are pivotally interconnected at 31. One of the limbs 29a is carried pivotally from longitudinal member 7 by way of pin 33 and its other end is received slidably in a groove carried from the longitudinal member 21 of the ventilator. The other limb 29b is pivotally carried from the frame member 21 at 37 whilst its other end is received slidably in a carrier 39 depending from the framework 7. It will be seen that the limb 29b also carries an actuating arm 41 to which an actuating rod or wire 4 3 is connected and which is actuated from the end of the Polyhouse. Such an arm need only project a small amount into the Polyhouse and so does not obstruct headroom. It will be understood that the scissor mechanisms are provided in pairs one each side of the framework as shown better from Figure 2 and that pairs of these mechanisms are preferably disposed along the length of the framework at spaced intervals so that the framework lifts parallel to the opening. The operating rod or wire 43 can simply connect with the respective arms or as shown in Figure 2 with a bar 45 linking the pairs of arms.

Claims

1. A ventilator for a Polyhouse comprising a movable framework and actuating means for the framework and wherein the actuating means operates on a scissor action.

2. A ventilator as claimed in claim 1, wherein opening movement of the framework is arranged on a hinging action from one edge of the framework or from an end thereof.

3. A ventilator as claimed in claim 1, wherein opening movement of the framework involves a lifting action.

4. A ventilator as claimed in claim 3, wherein the actuating means operates on a scissor action principle with two or more scissor action mechanisms disposed along the length of the Polyhouse and interconnecting the framework with structural members of the Polyhouse.

5. A ventilator as claimed in any one of claims 1 to 4, wherein lengthwise members of the framework are constructed from longitudinal channel members, whereby skinning for the ventilator is retained in said channels by insert members.

6. A Polyhouse construction comprising a plurality of longitudinally spaced hoops having applied thereover a covering of sheet material and where the passage of the sheet material over the hoops is interrupted by spaced longitudinal members to which the sheet material is secured and where one or more ventilators as claimed in any one of claims 1 to 5 is or are positioned between those spaced members running lengthwise along the Polyhouse.

7. A Polyhouse as claimed in claim 6, wherein the ventilator is placed centrally straddling the apex of the house.

8. A Polyhouse as claimed in claims 6 or 7, wherein the longitudinal members of the house take the form of open channel members, in which the sheet material is retained by retention members inserted into the channels with the sheet material therebetween.

9. A Polyhouse as claimed in claim 8, further comprising means for securing retention members in said channels.

10. A Polyhouse as claimed in claims 8 or 9, wherein the channel member has a radiused edge to its open mouth at least to one side.

11. A ventilator for a Polyhouse substantially as hereinbefore described with reference to and as illustrated in any one of the accompanying drawings.

12. A Polyhouse substantially as hereinbefore described with reference to and as illustrated in any one of the accompanying drawings.