The present invention relates to an air control valve, and in particular to a valve for controlling the velocity of air at an intake hood of a trim handling system serving a high speed winder.

The system is particularly applicable to paper trim handling in the paper industry.

Typically in such systems air is drawn in through a long entry duct, which may be 6 metres in length, by a fan. In prior art systems, a damper is provided to control the air speed, but this can have the effect of increasing the amount of air which is actually pumped by the fan.

Many systems require a constant air flow to avoid overloading the apparatus, such as a filter, downstream of the fan.

The present invention provides a control valve between a fan and. an entry duct of a trim handling system, the valve comprising means for restricting the passage between the entry duct and the fan, and means for

bleeding air into the passage downstream of the restriction. Preferably the valve comprises a flap, and in particular two flaps, a first being provided for restricting the passage and a second controlling an opening for bleeding in air.

It has been found that the valve of the invention can control the air speed whilst at the same time allowing for a more even or substantially constant air flow past the fan.

Other preferred features and advantages of the invention will be apparent from the following description and the accompanying claims.

The invention will be further described by way of example with reference to the accompanying drawings, in which:

Figure 1 shows schematically an air handling system incorporating a valve in accordance with the invention; and

Figure 2 is a more detailed side view of the valve of Figure 1.

Figure 1 shows an air handling system 2 particularly

designed for handling paper trim, comprising an entry duct 4 which may typically be 6 to 8 metres long and of rectangular cross-section. The duct 4 feeds air to a fan 6 housed in an acoustic box 8 for reducing noise emission. The duct 4 may also act as or incorporate a silencer.

Positioned just outside of the acoustic box, in series between the entry duct 4 and the fan 6, is an air velocity control valve 10 in accordance with the invention.

As seen more particularly in Figure 2, the valve 10 comprises a first flap 12 which is motorised and arranged to be pivoted about one end 14 so as to extend into the passage 15 between the duct 4 and fan 6. In its "off" position, the flap 12 lays along the top of the passage 15. The flap 12 extends across the width of the passage 15 which is seen in side view in Figures 1 and 2.

The positioning of the flap 12 controls the operation of a second flap 16 which pivots freely and controls the opening of a bleed aperture 18. Bleed aperture 18 is connected by a conduit 20 to the acoustic box 8 and an air stream is drawn into the passage 15 by the flow of the main air stream A from the duct 4.

The movement of the flap 16 is limited by an adjustale stop 22, whilst the motorised flap 12 may be swung further into the passage 15.

Flap 16 bears .on flap 12 by an adjustable stop 24 and so the valve can be tuned to the requirements of the air handling system by adjustment of the stops 22, 24.

The flaps 12, 16 are shown in full outline in their closed position and in dotted outline with the flap 16 fully open.

By drawing air in from the acoustic box 8, the cooling of the fan motor can be enhanced.

Various modifications may be made to the described embodiment and it is desired to include all such modifications as fall within the scope of the accompanying claims.