GB2202506A - Pneumatic transfer of particulate material - Google Patents

Abstract

A method of pneumatically transferring particulate material from a bulk comprises disposing a tubular device (2) in the bulk (3), the tubular device (2) having a longitudinal opening (7) for the ingress of the particulate material, an air and particulate material outlet (4b) at or towards one end and an air inlet (4a) at or towards its other end, applying suction to the outlet (4b) to draw air from the inlet (4a) and so entrain particulate material from the bulk (3) and simultaneously applying fluid pressure from a pressurised source to the inlet (4a). The method has been found to have particularly advantageous application in sand box and ejector equipment for railway locomotives in which the tubular device (2) is disposed in the sand box (1) for transferring sand from the sand box (1) to the ejector.

Description

Pneumatic Transfer of Particulate Material This invention relates to the pneumatic transfer of particulate material from a bulk at one location to a second location. Such transfer has appplication in large size installations for the transfer of, for example, sand, cement, fly ash, sugar, grain to and from railway vehicles, down to small installations such as coffee dispensing machines. It also has application in sand box and ejection equipment of railway locomotives.

One object of the invention is to provide a pneumatic transfer system in which particulate material can be transferred even though it may contain a relatively high degree of dampness.

According to one aspect of the invention a method of pneumatically transferring particulate material from a bulk comprises disposing a tubular device in the bulk, the tubular device having a longitudinal opening for the ingress of the particulate material and a fluid particulate material outlet at or towards one end and a fluid inlet at or towards its other end, applying suction to said outlet to entrain particulate material from the bulk and simultaneously applying fluid pressure from a pressurised source to said inlet. In many applications the fluid will be air.

According to a second aspect of the invention, there is provided an apparatus for transferring particulate material from a bulk at a first location to a second location comprising a tubular device adapted to be disposed in the bulk and having a longitudinal opening for the ingress of particulate material, an outlet at or towards one end for particulate material, a fluid inlet at or towards the other end, means for applying suction to said outlet and a pressurised fluid source for applying a fluid pressure to said fluid inlet.

The invention has been found to have particularly advantageous application in sand box and ejector equipment for railway locomotives. Such equipment must be capable of operating for short periods at a controlled rate and be reliable despite variations in the condition of the sand. The invention will now be further described in this context.

In order to improve traction under certain railway track conditions (under wet or greasy conditions), a small quantity of sand or other grit is placed between the rail and the driving wheel of the locomotive. The sand is stored in boxes on the locomotive from which it is carried to a sand ejector and directed towards the wheel and rail.

Various methods have been used to deliver the sand from its box. The early methods worked largely by a gravity feed from the bottom of the box. Later methods operate on a suction principle and all have devices suspended in the sand with an opening through which the sand can be collected from the box. In each of these devices one end, i.e. the inlet end, is open to the atmosphere and the other is connected to the sand ejector which has a venturi to create a suction pressure.

When the ejector operates it therefore causes a fall in air pressure which draws air through the device picking up grains of sand and carrying them to the ejector. All of these devices have difficulty in removing from the box, sand that will not flow due to damp or compaction, and some are prone to blockages.

In applying the invention to a sand box and ejector equipment for a railway locomotive, the aforesaid tubular device is disposed in the sand box for transferring sand from the sand box to the ejector.

It has been found, very surprisingly, that applying a positive pressure, i.e. an above atmospheric pressure, to the inlet of the device is very effective in providing a very consistent sand delivery to the ejector irrespective of whether the sand is dry or damp.

Existing designs of ejector contain a nozzle through which pressurised air is allowed to escape at high velocity into and along the barrel of the ejector. This causes a partial vacuum within the barrel, in the vicinity of the nozzle, which is used to draw in sand at an angle to the ejector barrel and hence into the stream of escaping air as shown in Figure 1 of the accompanying drawings. After several hours of continual use the case hardened barrel opposite the sand inlet is worn to the extent that replacement becomes necessary. Furthermore the changes in section and direction of the sand path make this type of ejector prone to blockage.

In further development of the invention and in order to overcome these problems a new design of ejector has been produced which allows the sand to travel in a straight path.

Thus the reliability of the ejector and the useful life of the barrel are thereby increased. In this new design of ejector the sand passes along a straight duct to an inlet port on the axis of the barrel, the said duct and the barrel being co-axial. The barrel is of slightly larger diameter than the inlet port and high pressure air is arranged to enter the barrel around the outside of the sand inlet, to produce a partial vacuum that draws the sand into the high velocity air blast.

This design of ejector produces a more uniform pattern of wear on the barrel than is achieved with the previous type of ejector shown in Figure 1.

The invention will now be further described by way of example as applied to sand box and ejector equipment on a railway locomotive and with reference to Figures 2 to 4 of the accompanying diagrammatic drawings in which: Figure 2 illustrates the equipment with the sand box shown in section, Figure 3 shows a preferred form of ejector in accordance with the invention, and Figure 4 shows a cross-section through a preferred form of tubular device for collecting sand from the sand box.

Referring to Figures 2 to 4 of the drawings, sand box 1 contains a sand collecting device 2 embedded in the sand 3.

The device 2 comprises a horizontal sand collecting tube extending substantially horizontally and linearly between opposite sides of the sand box adjacent the bottom of the sand box 1 and connecting with ports in these sides. At these ports inlet tube 5 and outlet tube 6 are sealed into the inlet and outlet ends 4a and 4b of the collecting tube 2. Along its lower side the tube is provided with a slit 7 through which the sand is drawn from the box 1 into the tube 2. The slit may, for example, extend over 1200 of arc about the centre of the tube 2. However, this angle may vary to suit the desired characteristics of the material being delivered.

The inlet tube 5 tees into a line 8 which leat from a source of air pressure. The outlet -tube 6 leads to a sand ejector 9 which also connects via the line 8 to the source of air pressure. Chokes 11 and 12 are fitted in the inlet tu 5 and in the line 8 adjacent the ejector 9. The choke 11 controls the air flow to the device 2 via the inlet tube 5 and the choke 12 controls the air flow to the ejector 9 which creates a suction pressure in outlet tube 6 to draw air and sand from the sand box I through the device 2.

In this particular example the pressure applied by the air source is between 50 and 100 p.s.i. (345 - 690 kN/m2). The range of the chokes 11 and 12 is 1 to 2 mm. The vacuum produced by the ejector is 2"-6" of mercury. The flow of sand through the outlet tube 6 and out of the ejector is between 300 and 700 grams per minute.

In operation, as the sand. ejector 9 applies suction to the outlet tube 6 a positive air pressure is simultaneously applied to the inlet tube 5 from the source of air pressure.

The air movement caused within the sand box 1 is rapid and turbulent and may extend beyond the confines of the collecting tube 2. A slight positive pressure is thus produced which helps to prevent the ingress of atmospheric air into the box 6 and reduces compaction of the sand.

It was observed that the speed and turbulence of the air through the device 2 is very effective in dislodging sand grains from around it and the slight positive pressure bursts any cavities so formed. By control of air pressures and tube and choke sizes the rate of delivery is reliably controlled.

It is ts be noted that this method will work for other material than sand and with other fluid media than air.

As seen in Figure 3, the ejector 9 comprises straight air and sand duct 21 extending co-axially with the ejector barrel 22. The duct 21 is of smaller diameter than the barrel 22 and connects with the barrel 22 via annular shoulder 23.

Surrounding the duct 21 is an annular air duct 24 which connects via supply duct 25 to the high pressure air supply line 8. Leading from the duct 24 are a series of ducts 27 which have orifices in the shoulder 23 opening into the barrel 22. The ducts 27 are regularly spaced about the axis of the duct 21 and are inclined towards the axis of the barrel 22 so that the air issuing from the orifices makes an angle if of about 150 with the axis of the barrel 22 to create areas of vacuum 28 in the barrel 22 as shown in dotted line adjacent the shoulder 23 to cause sand and air to be drawn along duct 21 and into the barrel 22. Since the sand is not drawn in at a significant angle with respect to the barrel axis, there is no significant short term wear on the barrel by the direct impingement of sand.

Figure 4 shows a cross-section of a particular form of tubular device 2 for collecting sand from the sand box 1. In the device 2 of Figure 4 the inlet for the sand instead of being a slit is a throat 31 formed by shaping the material of the device 2 and through which the sand must pass in order to enter the device 2. This throat 31 providing that its width is appropriately sized in relation to the particulate material can act as a valve to prevent back feed of the material. Thus if the pressures are removed, and the weight of the material tends to push the material back, the throat 31 becomes blocked with the material.

Claims (1)

1. A method of transferring particulate material from a bulk at a first location to a second location comprising disposing a tubular device in the bulk, the tubular device having a longitudinal opening for the ingress of the particulate material, a fluid and particulate material outlet at or towards one end and a fluid inlet at or towards its other end, applying suction to said outlet to entrain particulate material from the bulk and simultaneously applying fluid pressure from a pressurised source to said inlet.

2. A method according to claim 1, wherein said fluid is air.

3. An apparatus for transferring particulate material from a bulk at a first location to a second location comprising a tubular device adapted to be disposed in the bulk and having a longitudinal opening for the ingress of particulate material, an outlet at or towards one end for particulate material, a fluid inlet at or towards the other end, means for applying suction to said outlet and a pressurised fluid source for applying a fluid pressure to said fluid inlet.

4. A sand box and ejector equipment for a railway locomotive and comprising an apparatus according to claim 3 disposed in the sand box for transferring sand from the sand box to the ejector.

5. An equipment according to claim 4, wherein said tubular device extends substantially horizontally and linearly adjacent the bottom of the sand box.

6. An equipment according to claim 4 or 5, wherein said pressurised fluid source also connects with said ejector to create the suction at the outlet of said tubular device.

7. An equipment according to any of claims 3 to 6, wherein the longitudinal opening in said tubular device comprises a throat through which the sand has to pass in order to enter the device.

8. An equipment according to any of claims 3 to 7, wherein the ejector comprises an ejector barrel and an air and sand duct extending coaxially with the ejector barrel, the duct being of smaller diameter than the barrel and connecting with the barrel via an annular shoulder, and a plurality of air ducts connecting with the pressurised source and having orifices in the shoulder, which orifices are spaced from one another around the shoulder whereby air flowing through said orifices from the pressurised source creates suction in the barrel to cause air and sand to be drawn along said air and sand duct.

10. An equipment according to claim 9, wherein said air ducts are inclined towards the axis of said barrel.

Amendments to the claims have been filed as follows CLAIMS 1. A method of transferring particulate material from a bulk at a first location to a second location comprising disposing a tubular device in the bulk, the tubular device having a laterally or downwardly directed longitudinal opening for the ingress of the particulate material, a fluid and particulate material outlet at or towards one end and a fluid inlet at or towards its other end, applying suction to said outlet to entrain particulate material from the bulk and simultaneously applying fluid pressure from a pressurised source to said inlet.

2. A method according to claim 1, wherein said fluid is air.

3. An apparatus for transferring particulate material from a bulk at a first location to a second location comprising a tubular device adapted to be disposed in the bulk and having a longitudinal opening for the ingress of particulate material, an outlet at or towards one end for particulate material, a fluid inlet at or towards the other end, means for applying suction to said outlet and a pressurised fluid source for applying a fluid pressure to said fluid inlet.

4. A sand box and ejector equipment for a railway locomotive and comprising an apparatus according to claim 3 disposed in the sand box with the longitudinal opening laterally or downwardly directed for transferring sand from the sand box to the ejector.

5. An equipment according to claim 4, wherein said tubular device extends substantially horizontally and linearly adjacent the bottom of the sand box.

6. An equipment according to claim 4 or 5, wherein said pressurised fluid source also connects with said ejector to create the suction at the outlet of said tubular device.

7. An equipment according to any of claims 3 to 6, wherein the longitudinal opening in said tubular device comprises a throat through which the sand has to pass in order to enter the device.

8. An equipment according to any of claims 3 to 7, wherein the ejector comprises an ejector barrel and an air and sand duct extending coaxially with the ejector barrel, the duct being of smaller diameter than the barrel and connecting with the barrel via an annular shoulder, and a plurality of air ducts connecting with the pressurised source and having orifices in the shoulder, which orifices are spaced from one another around the shoulder whereby air flowing through said orifices from the pressurised source creates suction in the barrel to cause air and sand to be drawn along said air and sand duct.

10. An equipment according to claim 9, wherein said air ducts are inclined towards the axis of said barrel.