NZ299057A - Ventilation fan unit has a fan motor, casing and adjustable telescoping ducting - Google Patents

Description

299057 r Priority Date(s): Comptet# Specification Filed: Cite*: $). EaUJED/ofi E^MLj.oa. fufcflsartkm D«te: P.O. Journal No: .JftiCa t Patents Form No. 5 PATENTS ACT 1953 COMPLETE SPECIFICATION A FAN UNIT FOR A VENTILATION SYSTEM We, THERMOPLASTIC ENGINEERING LIMITED, a New Zealand company, of 151 Park Road, Miramar, Wellington, New Zealand do hereby declare this invention to be described in the following statement: FIELD OF INVENTION 299057 The invention comprises a fan unit for a ventilation system or similar which allows for adjustment of the volume of air driven through the ventilation system by the fan unit. The 5 invention also comprises a method of adjusting the volume of air driven through a ventilation system by a fan unit.

BACKGROUND Ventilation systems including air conditioning systems, in buildings, factories or similar generally include at least one fan unit which drives the air through the ventilation system. Typically the fan unit comprises a fan motor and a fan box or casing which houses the rotating fan rotor. The fan box has an inlet to which is connected the piping or ducting of the ventilation system on one side from which air is to be drawn, and an outlet to which 15 piping or ducting of the ventilation system on the other side is connected, through which the air is expelled or driven.

In a particular application which is the ventilation of fumecupboards in laboratories, factories or elsewhere where fumecupboards are provided to house chemicals or similar, the 20 fumecupboard typically comprises an associated extraction ventilation system including a fan unit as described, which draws air from the fumecupboard and expels it, often after passing through chemical scrubbers or similar to outside the building. 299057 SUMMARY OF INVENTION The present invention provides an improved or at least alternative fan unit for such a ventilation system, which enables adjustment of the volume of air driven through the 5 ventilation system, and a method of adjusting the volume of air driven through the ventilation system.

In broad terms in one aspect the invention comprises a fan unit for a ventilation system, comprising: a fan motor, a fan casing having an inlet and an outlet and housing a rotating fan rotor, a first section of pipe or duct having a forward end engaging through the inlet to the fan casing, and into the casing and which is positionable such that the forward end of the first section of pipe partly covers the blades of the fan rotor to reduce the volume of air driven through the ventilation system by the fan unit, the position of the first section of pipe being adjustable relative to the fan rotor to adjust the flow rate of air driven through the 20 ventilation system by the fan, and a second section of pipe or duct couplable to or coupled to or forming part of the piping or ducting of the ventilation system, and to which the other end of the first section of pipe or duct is adjustably coupled. , 299057 In broad terms in another aspect the invention comprises a method of adjusting the volume of air driven through a ventilation system by a fan unit comprising a fan motor and a fan casing housing the fan rotor, comprising extending the forward end of a section of pipe or duct of the ventilation system which connects to the inlet to the fan casing, into the fan 5 casing to cover part of the blades of the fan rotor to reduce the volume of air driven through the ventilation system by the fan.

In fan units incorporating a variable speed motor, the volume of air driven by the fan unit may be controlled by adjusting the motor speed. However in many situations the added 10 cost of a more expensive variable speed motor is not justified. When a fumecupboard and associated ventilation system are installed in a laboratory for example, it is desirable to be able to initially adjust and set the flow rate of air extracted by the ventilation system of the fumecupboard when the fan is operating. However it is not economic to install a variable speed fan motor simply for the purpose only of enabling this initial adjustment or setting 15 up of the ventilation system. The present invention provides a simple means whereby the air flow rate of the ventilation system may be initially adjusted in setting up the fumecupboard, to match the airflow requirements of the fumecupboard, without requiring that a variable speed fan motor be utilised.

BRIEF DESCRIPTION OF DRAWINGS The invention is further described with reference to the accompanying drawings, which show preferred forms of fan units of the invention by way of example and without intending to be limiting. In the drawings: u»|, ~ v 0 J Figure 1 is a schematic cross-section through the roof structure of a building housing a fumecupboard showing the fan unit of the invention installed in the ceiling cavity of the building, Figure 2 is a cross-sectional view of the fan casing and air flow rate adjustment means of one preferred form fan unit, Figure 3 is a view of the preferred form air flow rate adjustment means of the fan unit of Figure 2, and Figure 4 is a cross-sectional view similar to Figure 2, of another preferred form fan unit.

DETAILED DESCRIPTION OF PREFERRED FORMS Referring to Figure 1, a fumecupboard 1 installed in a building is ventilated through the roof of the building via a fan unit of the invention. Pipe or ducting 2 from the fumecupboard passes through the ceiling 3 and connects to the fan unit generally indicated at 4 in Figure 1, which ventilates through the roof of the building via a cowl 5. Typically the fan unit 4 is suspended from the rafters of the building via a cradle 6 within the ceiling 20 cavity of the building. The fan unit comprises an electric fan motor 7 and fan casing 8. The ducting 2 from the fumecupboard connects to the inlet of the fan box 8. Air ventilated from the fumecupboard is driven from the exit of the fan casing to the external environment through ducting from the outlet of the fan casing to the cowl 5. 299057 In the preferred form fan unit described the fan motor 7 is a fixed speed or direct drive fan motor. Referring to Figure 2, the fan motor drives a rotor comprising an impeller (or propeller) 9 housed within the fan casing 7. As the impeller 9 rotates, air is drawn into the fan casing through the inlet 10 and expelled from the outlet 11. The inlet to the fan casing is connected to the ducting 2 from the fumecupboard via an airflow adjustment means also shown in Figure 3, comprising a first section of pipe 12 which is telescopically mounted within a second pipe section 13, which is in turn connected to the ducting 2 via a circumferential bracket 14 which is bolted or screwed or otherwise suitably secured to the end of the ducting 2.

The forward end 12a of the pipe section 12 passes through the inlet 10 of the fan casing. The position of the pipe section 12 may be telescopically adjusted relative to the fixed pipe section 13, so that the forward end 12a of the pipe section 12 covers part of the blade of the fan impeller as shown in Figure 2. This effectively reduces the effective area of the impeller and thus the volume of air which will be driven through the ventilation system by the fan. By adjusting the position of ihe pipe section 12 so that the forward end 12a projects more, or less, into the fan casing 7 to cover more, or less, of the fan impeller 9, the volume of air driven by the fan may be decreased or increased.

In the preferred form fan unit shown, the fan rotor is an impeller 9 is of the type having a hollow interior with a number of individual fan blades which extend along the same axis as the axis of rotation of the impeller and are arranged radially around the axis of rotation of the impeller as shown so that the impeller has a hollow interior, and the forward end 12a of the pipe section 12 covers part of the fan blades by extending into the hollow interior 299057 of the impeller. In an alternative arrangement where the fan rotor comprises a propeller having blades which extend perpendicular to the axis of rotation (like an airplane propeller), the forward end 12a of the adjustable pipe section 12 may include a peripheral annular flange which is positioned closer to or further away from the propeller blades within the fan casing, to render less effective or more effective the propeller and thus decrease or increase the volume of air driven by the fan.

Figure 3 shows the pipe sections 12 and 13 separately from the fan casing. When a fumecupboard is installed and the flow rate of the ventilation system is adjusted by slidable positioning of the pipe section 12, the position of the pipe section 12 may then be fixed by tightening one or more screws or bolts which pass through slots 15 in the pipe section 13 and into or through the pipe section 12. The slots 15 allow for the adjustment of the position of the pipe section 12.

In the arrangement shown in Figures 2 and 3 the pipe section 12 is telescopically adjustable relative to the pipe section 13 in a simple arrangement, whereby the rear end 12b of the pipe section 12 slides within the pipe section 13, but alternatively the pipe section 12 could engage over the pipe section 13 in a similar sliding arrangement or movement of the pipe section 12 could be provided for by a concertina section between the pipe section 12 and the pipe section 13 or directly between the pipe section 12 and duct 2.

Figure 4 shows an alternative arrangement where the pipe section 12 is held by a bracket 14 providing a flange on the side wall of the fan casing 8 so that the position of the pipe section 12 may be adjusted to project further into the fan casing 8, and the duct 2 is 299057 connected directly to the pipe section 12. Screws or bolts or pins 15a pass through adjustment slots 15 in the pipe section 12. Other arrangements using the principle of the invention are possible.

The invention has been described with reference to the drawings in relation to fumecupboards, but also has application to other ventilation systems such as ventilation or air conditioning systems for buildings and similar, and is not limited in application to fumecupboards only.

The foregoing describes the invention including preferred forms thereof. Alterations and modifications as will be obvious to those skilled in the art are intended to be incorporated within the scope hereof, as defined in the accompanying claims. 7

Claims (8)

WHAT WE CLAIM IS:

1. A fan unit for a ventilation system, comprising: 5 a fan motor, a fan casing having an inlet and an outlet and housing a rotating fan rotor, a first section of pipe or duct having a forward end engaging through the inlet to the fan 10 casing, and into the fan casing and which is positionable such that the forward end of the first section of pipe partly covers the blades of the fan rotor to reduce the volume of air driven through the ventilation system by the fan unit, the position of the first section of pipe being adjustable relative to the fan blades of the rotor to adjust the flow rate of air driven through the ventilation system by the fan, and a second section of pipe or duct couplable to or coupled to or forming part of the piping or ducting of the ventilation system, and to which the other end of the first section of pipe or duct is adjustably coupled. 20

2. A fan unit according to claim 1, wherein said other end of)the first section of pipe or duct engages into or over the second section of pipe or duct and the position of the first section of pipe or duct relative to the fan blades is adjustable telescopically relative to the second section of pipe or duct. -9- 2990 5 7

3. A fan unit according to either one of claims 1 and 2, where the fan rotor comprises a hollow interior defined by a multiple number of fan blades extending parallel to the axis of rotation of the rotor and radially spaced around the axis of rotation, and the forward end of the first section of pipe or duct partly covers the blades of the fan rotor by extending into the hollow interior of the rotor to cover part of the blades of the fan to reduce the volume of air driven by the fan unit.

4. A fumecupboard and ventilation system for extracting air and fumes from the fumecupboard, comprising a fan unit according to any one of claims 1 to 3.

5. A method of adjusting the volume of air driven through a ventilation system by a fan unit comprising a fan motor and a fan casing housing the rotating fan rotor, comprising extending the forward end of a section of pipe or duct of the ventilation system which connects to the inlet to the fan casing, into the fan casing to cover part of the blades of the fan rotor to reduce the volume of air driven through the ventilation system by the fan.

6. A method according to claim 5, including adjustably mounting the section of pipe or duct extending into the fan casing so that its depth of penetration into the fan casing can be adjusted to adjust the flow of air driven through the ventilation system by the fan unit.

7. A fan unit for a ventilation system, substantially as described herein with reference to the accompanying drawings. - 10- 29905 7

8. A method of adjusting the volume of air driven by a fan unit through a ventilation system, substantially as herein described with reference to the accompanying drawings. GREG WEST-WALKER & COMPANY ATTORNEYS FOR THE APPLICANT end of claims