This invention relates to a slot ventilator, for example for use in a room with a sealed window or double glazing wherein it is desirable to provide ventilation without having to open the window.

Slot ventilators are known but they have always required a substantial dimension perpendicular to the face containing the slot in order to achieve effective opening of the slot by moving a facing strip for closing the slot by movement essentially parallel with the face containing the slot.

For some applications a slot ventilator is desirable with a very short dimension perpendicular to the face containing the slot and that is achieved in accordance with the present invention. According to the present invention there is provided a slot ventilator comprising an elongate slotted backing member and an elongate facing strip mounted by a spaced parallel-motion link to the backing member such that longitudinal movement of the facing strip also produces movement thereof towards or away from the backing member between a closed position obstructing a slot in the backing member, and a forward open position; the link being pivoted at one end to a rib extending from the facing strip into the slot, and at the other end to the backing member, the rib being cut away or otherwise shaped to accommodate the pivotal connection between the link and the backing member.

The cutaway enables the pivotal connections respectively to the rib and the backing member to be separated by only a short distance in a direction perpendicular to the plane of the slot while the, or each, link need only be a little longer than the desired amount of opening movement of the facing strip away from the backing member.

Each link is conveniently of "U" cross-section being pivoted to the backing member at the bottom of the "U" and pivoted to the rib at the top of the "U" where the two arms are on either side of the rib. The two arms of the ^■ *U" may be closely spaced on either side of the rib to provide an adequate support when the facing strip is in the open position. Inspite of the cutaway to accommodate the pivot to the backing member, the rib can be of sufficient extent into the slot to provide adequate engagement surfaces for the arms of the "U" of the, or each, link.

Preferably both the backing member and the facing strip are formed from extruded sections of uniform cross- section, possibly from aluminium or an aluminium alloy or of a suitable plastics material.

The invention may be carried into practice in various ways and one embodiment will now be described by way of example with reference to the accompanying drawings in which:

Figure 1 is a perspective view of a slot ventilator.

Figure 2 is a diagrammatic plan view to an increased scale showing the relationship between the backing member and the facing strip and a link in each of the closed and the open positions, and

Figure 3 is a sectional end view of Figure 2 with the facing strip in the open position to the left of the centre line and in the closed position to the right of the centre line.

The slot ventilator shown generally at 1 comprises a 0 backing member 3, a facing strip 7 and a parallel motion linkage supporting the facing strip on the backing member.

The backing member 3 comprises an elongate strip with a slot 4 extending lengthwise along it, and two parallel 5 flanges 5 extending rearwardly from the slotted strip. The flanges 5 are disposed close to the longitudinal edges of the slotted strip, on either side of the slot 4.

The facing strip 7 has a rearwardly extending o longitudinal rib 8 which at all times projects into the slot.

The parallel motion linkage comprises two parallel links 12 made of a tough, resilient plastics material such as that sold under the trade mark ^ll Delrin". Each link 12 is "U" shaped, the gap between the arms of the 5 "U" accommodating the rib 8, and the outer faces of these arms lying between and adjacent to or in contact with the flanges 5 of the backing member 3. Pivot pins

13 are provided to connect the ends of the links 12 to the flanges 5, and further pins 14 to connect the free ends of the arms of the links 12 to the rib 8, to allow movement of the facing strip 7 parallel to the backing member 3.

A handle 9 is provided protruding from the facing strip 7 in order to provide more manual purchase.

The links 12 are disposed so as to lie obliquely to the plane containing the axes of the pivot pins 13 when the facing strip 7 lies against the slotted strip portion of the backing member 3, closing the slot in the latter. By applying a force to the facing strip 7, by pushing the handle 9 in the direction of the arrow, (see Figure 2) the obliquity of the links 12 causes the facing strip 7 to move outwardly as well as longitudinally relative to the backing member 3 while remaining parallel to the latter, to an open position as shown in chain lines in Figure 2 and to the left of Figure 3.

The rib 8 serves also as a stop. Its edge 10 is positioned so that it butts against one end of the slot 4 at the fully open setting. The length of the rib 8 is such that the ventilator can thus be opened to the point where the links 12 have just passed through the position in which they are disposed in the dead-centre position, in order that deliberate longitudinal movement of the facing strip 7 in the reverse direction is required to close the ventilator, and the facing strip 7 cannot normally be slammed shut by a gust of air.

Both the facing strip and the backing member may be made from extrusions of uniform cross-section, e g of aluminium, and machined as necessary.

Adjacent the pivot pins 13, the rear edge of the rib 8 is cut away at 18 so that in the closed position, shown in solid lines in Figure 2, the pivot pins do not interfere with the rear edge of the rib and that means that the pivot pins 13 can be mounted close to the outer face of the backing member, which both reduces the dimension of the ventilator in the vertical direction in Figures 2 and 3 and incidentally reduces the amount of material necessary in both the backing member and the facing strip.

Figure 2 also shows how in the closed position in solid lines the links 12 are only a little oblique to the face of the backing member containing the slot. In fact in the example shown in Figure 2 the angle is about 30 degrees.

In that particular example with links with a length of 10.5 mm between the centres of the pivots 13 and 14, an opening movement of a half that length is permissible, ie about 5.2 mm away from the face of the back i.ng member, while the total depth of the backing member need only be about 13 mm. This compact arrangement is achieved by virtue of the cutaway 18 allowing for

effective positioning of the pivot pins 13 in the arms 5 of the backing member 3 without interfering with the rib 8 on the facing strip 7 in the closed position.

Accordingly, the present embodiment provides a ventilator having an opening movement of about 40% of the overall ventilator depth. Other embodiments (not shown) could have corresponding values of for example 30% or 50%.

The cutaway portion 18 could be semi-circular rather than rectangular.

The slot ventilator is conveniently installed in a passage in a window frame or sash.