GB2192164A - Rotary valves - Google Patents

Abstract

A rotary valve 1 e.g. located on discharge cyclone 30 of a suction conveying system, has a bladed rotor 20 operating within a resiliently deformable liner 8 disposed within a perforate casing 4 enclosed by a housing 2. The blades 24 of the rotor 20, which may be helically mounted, are held, in use, in sweeping contact with the liner 8 by differential pressure across the valve. Seizure of the rotor is prevented by the rearward orientation of the blades. The housing 2 has a pressure tapping which is connected to the upstream side of the system if it is for positive pressure handling. <IMAGE>

Description

SPECIFICATION Improvements in or relating to rotary valves This invention concerns improvements in or relating to rotary valves.

Rotary valves are used extensively in pneumatic transport systems because they can provide a reasonable seal against air ingress or egress whilst allowing a continuous discharge of materials from a receptacle. In order to minimise air leakage, the clearance between the rotor tips and the valve housing needs to be of the order of 0.5 mm to 1 mm.

A greater tolerance will result in extensive air leakage, whereas a smallertolerance can result in seizure of the valve. It is usually relatively simple to adjust the clearance, however as the tips ofthe rotor wearthrough use, the air leakage increases and thus the control over the pneumatictransportsystem is reduced thereby occasioning lower conveying efficiencies.

An object of the present invention is to provide an improved rotary valve giving a better seal than has hitherto been available from conventional valves.

Accordinglythe invention provides a rotary valve including a housing, a perforated cylindrical casing disposed within and spaced from the interiorwall of the housing, the housing having a pressure tapping, a hollow resiliently deformable linerwithin the casing, an inlettothe liner, an outletfrom the liner, and a bladed rotor with in the deformable liner, the blades of the rotor being maintained in contact with the liner in use by differential pressure across the valve.

The liner is conveniently made of a semi-rigid wear resistant material such, for example, as high gum content rubber which allows for surface deformation.

The blades of the rotor may advantageously be helically mounted on the shaft of the rotor and swept back such that in operation shear-forces between the blades and the liner are minimised. The blades may be made from a lowfriction polymer material in orderto reduce shear stress further.

Aflow restrictor may be provided at the inlet to prevent overfilling of the valve pockets defined between adjacent blades.

Bywayof example only, are embodimentof rotary valve according to the invention is described below with reference to the accompanying drawing which is a transverse cross section through the valve.

Referring to the drawing, a rotary valve 1 includes a housing 2 having a pressure tapping (not shown) and enclosing a casing 4 provided with perforations 6. A resiliently deformable liner 8 is disposed within the casing 4 in close adjacency to the internal wall thereof and has an inlet 10 and outlet 12 registering with inlet port 14 and outlet port 16 respectively in the casing, the inlet port 14 being provided with a flow restrictor 18.

A rotor 20 comprises a shaft 22 on which are mounted four blades 24 arranged helically thereabout and which are swept back in relation to the rotational direction. The blades 24 define pockets 26 therebetween and may conveniently be manufactured from lowfriction polymer material.

In operation, the rotary valve of the invention would be located on the discharge cyclone 30 of a suction conveying system, which would causethe liner8 to be drawn in to the tips of the blades 24, thus providing an effective seal. As the pressure drop across the valve 1 increases, the liner is drawn closer to the tips of the blades 24. The seal is thus constantly applied through the pressure differential butseizureofthe rotor is prevented by virtue ofthe rearward orientation of the blades. The helical form ofthe blades 24 prevents excessive radial distortion, thus prolonging the life ofthe liner8.

The flow restriction 18 at the inlet part 14 serves to preventoverfilling ofthevalve pockets 26.

If the valve 1 is to be used in a positive pressure pneumatic handling system, the pressure tapping on the housing 2 would be connected to the upstream side of the system.

1. Arotaryvalveincludinga housing, a perforated cylindrical casing disposed within and spaced from the interiorwall of the housing, the housing having a pressuretapping,a hollow resiliently deformable linerwithin the casing, an inlet to the liner, an outlet from the liner, and a bladed rotor within the deformable liner, the blades of the rotor being maintained in contact with the liner in use by differential pressure across the valve.

2. A rotary valve according to claim 1 in which the liner is made of a semi-rigid wear resistant material.

3. A rotary valve according to claim 2 in which the material is a high gum content rubber.

4. A rotary valve according to any one of the preceding claims in which the blades of the rotor are helically mounted on the shaft of the rotor and are swept back.

5. A rotary valve according to any one ofthe preceding claims in which the blades of the rotor are of a iowfriction polymer material.

6. A rotary valve according to any one of the preceding claims in which a flow restrictor is provided at the inlet.

7. A rotary valve substantially gs hereinbefore described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements in or relating to rotary valves This invention concerns improvements in or relating to rotary valves. Rotary valves are used extensively in pneumatic transport systems because they can provide a reasonable seal against air ingress or egress whilst allowing a continuous discharge of materials from a receptacle. In order to minimise air leakage, the clearance between the rotor tips and the valve housing needs to be of the order of 0.5 mm to 1 mm. A greater tolerance will result in extensive air leakage, whereas a smallertolerance can result in seizure of the valve. It is usually relatively simple to adjust the clearance, however as the tips ofthe rotor wearthrough use, the air leakage increases and thus the control over the pneumatictransportsystem is reduced thereby occasioning lower conveying efficiencies. An object of the present invention is to provide an improved rotary valve giving a better seal than has hitherto been available from conventional valves. Accordinglythe invention provides a rotary valve including a housing, a perforated cylindrical casing disposed within and spaced from the interiorwall of the housing, the housing having a pressure tapping, a hollow resiliently deformable linerwithin the casing, an inlettothe liner, an outletfrom the liner, and a bladed rotor with in the deformable liner, the blades of the rotor being maintained in contact with the liner in use by differential pressure across the valve. The liner is conveniently made of a semi-rigid wear resistant material such, for example, as high gum content rubber which allows for surface deformation. The blades of the rotor may advantageously be helically mounted on the shaft of the rotor and swept back such that in operation shear-forces between the blades and the liner are minimised. The blades may be made from a lowfriction polymer material in orderto reduce shear stress further. Aflow restrictor may be provided at the inlet to prevent overfilling of the valve pockets defined between adjacent blades. Bywayof example only, are embodimentof rotary valve according to the invention is described below with reference to the accompanying drawing which is a transverse cross section through the valve. Referring to the drawing, a rotary valve 1 includes a housing 2 having a pressure tapping (not shown) and enclosing a casing 4 provided with perforations 6. A resiliently deformable liner 8 is disposed within the casing 4 in close adjacency to the internal wall thereof and has an inlet 10 and outlet 12 registering with inlet port 14 and outlet port 16 respectively in the casing, the inlet port 14 being provided with a flow restrictor 18. A rotor 20 comprises a shaft 22 on which are mounted four blades 24 arranged helically thereabout and which are swept back in relation to the rotational direction. The blades 24 define pockets 26 therebetween and may conveniently be manufactured from lowfriction polymer material. In operation, the rotary valve of the invention would be located on the discharge cyclone 30 of a suction conveying system, which would causethe liner8 to be drawn in to the tips of the blades 24, thus providing an effective seal. As the pressure drop across the valve 1 increases, the liner is drawn closer to the tips of the blades 24. The seal is thus constantly applied through the pressure differential butseizureofthe rotor is prevented by virtue ofthe rearward orientation of the blades. The helical form ofthe blades 24 prevents excessive radial distortion, thus prolonging the life ofthe liner8. The flow restriction 18 at the inlet part 14 serves to preventoverfilling ofthevalve pockets 26. If the valve 1 is to be used in a positive pressure pneumatic handling system, the pressure tapping on the housing 2 would be connected to the upstream side of the system. CLAIMS

1. Arotaryvalveincludinga housing, a perforated cylindrical casing disposed within and spaced from the interiorwall of the housing, the housing having a pressuretapping,a hollow resiliently deformable linerwithin the casing, an inlet to the liner, an outlet from the liner, and a bladed rotor within the deformable liner, the blades of the rotor being maintained in contact with the liner in use by differential pressure across the valve.

2. A rotary valve according to claim 1 in which the liner is made of a semi-rigid wear resistant material.

3. A rotary valve according to claim 2 in which the material is a high gum content rubber.

4. A rotary valve according to any one of the preceding claims in which the blades of the rotor are helically mounted on the shaft of the rotor and are swept back.

5. A rotary valve according to any one ofthe preceding claims in which the blades of the rotor are of a iowfriction polymer material.

6. A rotary valve according to any one of the preceding claims in which a flow restrictor is provided at the inlet.

7. A rotary valve substantially gs hereinbefore described with reference to the accompanying drawing.