GB2290117A - Improvements relating to airlocks - Google Patents

Abstract

An airlock comprising a duct 2 and valve means 4, 6, which valve means is/are operable to assume an open or closed condition in response to the flow of particulate material e.g. tobacco through the duct. During periods of continuous material flow, the rate of material supply and the rate of material removal are controlled relative to one another in order to ensure that a body of particulate material is maintained within the duct. <IMAGE>

Description

Improvements Relating to Airlocks The subject invention relates to airlocks.

Industry is constantly striving to improve safety standards for its employees within the working environment, the key reason for this being to reduce accidents. One particular cause of accidents within the workplace is airlocks. A commonly used airlock at the present time contains a rotating component comprising several equiangular spaced blades. The component rotates within a housing in such a manner as to produce a continuous seal between each side of the airlock. The nature of the rotary type airlock is such that it produces a situation where accidents are likely to occur. An example of such an accident might be a person getting their fingers caught between the rotating bladed component and a wall of the housing.

An object of the subject invention is to provide an airlock with improved safety aspects relative to conventional airlocks. In addition, the subject invention provides a method of feeding material, for example tobacco, through an airlock.

The subject invention provides an airlock comprising downwardly extending duct means, a portion of the lengthwise extent of the interior of said duct means being bounded at the upper end thereof by first valve means and at the lower end thereof by second valve means, each of said first valve means and said second valve means being operable to obturate said duct means, said first valve means being operable also to assume an open condition upon there becoming present in said duct means at the upper side of said first valve means a first, pre-set amount of particulate material, and said second valve means being operable to assume an open condition upon there becoming present in said duct means at the upper side of said second valve means a second, pre-set amount of said material. Such airlock is hereafter referred to as "an airlock as defined".In regard to practical considerations, and as will be readily appreciated by those skilled in the art, it is preferable that the second amount is greater than the first amount.

The first and/or second valve means could, for example, be operable to assume an open condition by the weight or volume of a material to the upper side of the valve means. The volume of material may be considered to be represented by the height of material in the duct, assuming a constant cross-section of the duct.

It is possible that the first and/or second valve could take the form of a hinged flap. Much by preference, valve means utilised for the purposes of the subject invention are so-called full-bore, or substantially fullbore valves.

The subject invention further provides a method of feeding particulate material through an airlock as defined, wherein during periods of continuous material flow through said airlock said first valve means alternates between open and closed conditions, said second valve means is maintained in an open condition, and a body of said particulate material is maintained in said duct means, which body of material substantially prevents gas flow through said duct.

Advantageously, control means is associated with supply means, operable to supply particulate material to the duct means at the upper end thereof, and/or with receiving means, operable to receive the material from the lower end of the duct means and to transfer the material therefrom, the control means being operable to ensure that said body of particulate materials is maintained in the duct means. The control means may be operable to vary the flow rate of the material into and/or out of the duct.

The material may be, for example, particulate tobacco.

The body of material should not extend, heightwise in the duct, above the location of the first valve means.

In order that the subject invention may be easily understood and readily carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings herewith, which depicts tobacco feed apparatus.

The apparatus depicted in the drawings comprises an airlock 1, which airlock 1 comprises a downwardly extending duct 2 having a rectangular horizontal crosssection, a portion 3 of the duct 2 being bounded at the upper end by a flap 4 (providing first valve means), the flap 4 being hinged at point 5 on the drawing. The lower end of the portion 3 of the duct means 2 is bounded by a second flap 6 (providing second valve means), the flap 6 being hinged point 7. Both hinges 5 and 7 are operable so as to allow movement of flaps 4 and 6 respectively, as indicated by the broken lines. The operation of both flaps 4 and 6 is controlled by the presence of counter weights 5' and 7' attached to hinges 5 and 7 respectively.

Particulate tobacco is directed into the duct 2 by a separator (constituting supply means), generally designated by reference numeral 8. The tobacco/air separator 8 comprises an inlet 9, a mesh screen 10, and two outlets 11 and 12. The tobacco is removed from the end of the duct means 2 by a band conveyor 13 (constituting receiving means), which conveyor 13 operates in a direction designated by the arrow A, and is driven by a drive means (not shown).

In operation of the tobacco feed apparatus, tobacco entrained in air enters the separator 8 through inlet 9.

The mesh screen 10 deflects the tobacco downwards in a direction indicated by the arrow B through the outlet 12, the air passing through the screen 10 and exiting the separator 8 through the outlet 11. The tobacco from outlet 12 feeds into the upper end of the duct means 2.

When a pre-set weight of tobacco has accumulated on the flap 4 the downward force of the tobacco on the flap overcomes the upward force caused by the counter weight on the hinge and the flap 4 therefore assumes an open condition. This results in the tobacco falling in a downward direction off the flap 4, after which the flap 4 resumes a closed condition. Flap 4 alternates in this manner between open and closed conditions at frequent, regular intervals. When a second pre-set weight of tobacco has accumulated on the upper side of flap 6, which second pre-set weight is greater than the first pre-set weight, the flap 6 assumes an open condition. Whilst there is a continuous feed of tobacco through the duct means 2, the flap 6 remains open. As the tobacco leaves the lower end of the duct means 2 it passes onto the offfeed band conveyor 13. The rate of removal of tobacco from the lower end of the duct means 2 relative to the rate of feed of tobacco into the separator 8, is such that a body of tobacco is maintained in said duct means 2 in a region generally designated by the reference numeral 14, which body of tobacco substantially prevents gas flow through said duct means 2. It is also the presence of this body of tobacco in the region 14 which maintains the flap 6 in the open condition thereof.

Suitably, the apparatus further comprises control means (not shown), electronic control means for example, operable to vary the relative inlet and outlet flow rates by, for example, varying the drive speed of the band conveyor 13, relative to the inlet flow rate of the tobacco into the duct from the separator 8, so as to ensure that the said body of tobacco is maintained in the duct to not less than a minimum preselected height within the duct.

Whereas it is advantageous for there to be provided in the apparatus just described both first and second valve means, e.g. flaps 4, 6, it is conceivable for there to be provided only what in the described apparatus is the lower of the valve means (flap 6). As will be appreciated, in such case, and where the single valve means takes the form of a flap as per flap 6, the arrangement will be such that even at its minimum height in the duct, said body of tobacco will serve to hold the flap in its open condition.

Thus, according to another aspect of the subject invention there is provided particulate material feed means comprising material supply means; an airlock comprising downwardly extending duct means and valve means, which valve means is operable to obturate said duct means and to assume an open condition upon there becoming present in said duct means at the upper side of said valve means a pre-set amount of particulate material; and receiving means, said supply means being operable to supply particulate material to said duct means at the upper end thereof and said receiving means being operable to receive particulate material from the lower end of said duct means and to transfer the material therefrom. Such particulate matter feed means is hereinafter referred to as "a particulate-matter feed means as defined".

Another aspect of the subject invention provides a method for feeding particulate material through particulate-material feed means as defined; wherein during periods of continuous material flow through said particulate-material feed means, said supply means supplies particulate material to said duct means at the upper end thereof, said valve means is maintained in an open condition and a body of said particulate material is maintained in said duct means, which body of material substantially prevents gas flow through said duct means, and the receiving means receives the particulate material from the lower end of the duct means and transfers the particulate material therefrom.

Claims (17)

1. An airlock comprising downwardly extending duct means, a portion of the lengthwise extent of the interior of said duct means being bounded at the upper end thereof by first valve means and at the lower end thereof by second valve means, each of said first valve means and said second valve means being operable to obturate said duct means, said first valve means being operable to assume an open condition upon there becoming present in said duct means at the upper side of said first valve means a first, pre-set amount of particulate material and said second valve means being operable to assume an open condition upon there becoming present in said duct means at the upper side of said second valve means a second, pre-set amount of said material.

2. An airlock according to Claim 1, wherein said second pre-set amount is greater than said first pre-set amount.

3. An airlock according to Claims 1 or 2, wherein one or both of said first and second valve means is operable to assume an open condition by virtue of the weight of said pre-set amount of said material to the upper side of the valve means.

4. An airlock according to Claims 1 or 2, wherein one or both of said first and second valve means is operable to assume an open condition by virtue of the volume of said pre-set amount of said material to the upper side of the valve means.

5. An airlock according to any one of the preceding claims, wherein one or both of said first and second valve means comprises a hinged flap.

6. An airlock according to Claim 5, wherein a counter weight is operably connected to said hinged flap.

7. An airlock according to any one of the preceding claims, wherein one or both of said valve means is a substantially full-bore valve means.

8. A method of feeding particulate material through an airlock according to .any one of the preceding claims, wherein during periods of continuous material flow through said airlock said first valve means alternates between open and closed conditions, said second valve means is maintained in an open condition, and a body of said particulate material is maintained in said duct means, which body of material substantially prevents gas flow through said duct means.

9. A method according to Claim 8, wherein said particulate material is supplied by a supply means operable to supply particulate material to said airlock at a pre-set flow rate.

10. A method according to Claim 9, wherein said flow rate of said particulate material can be varied by control means.

11. A method according to any one of Claims 8, 9 or 10, wherein said particulate material is removed from the lower end of said duct means by a receiving means, said receiving means being operable to receive said material from said lower end of said duct means and to transfer said particulate material therefrom.

12. A method according to Claim 11, wherein said receiving means is a conveyor.

13. A method according to any one of Claims 8 to 12, wherein said particulate material is particulate tobacco.

14. Apparatus as substantially described herein and with reference to the drawing.

15. A method as substantially described herein and with reference to the drawing.

16. Particulate material feed means comprising material supply means, an airlock and receiving means, said airlock comprising downwardly extending duct means and valve means, which valve means is operable to obturate said duct means and to assume an open condition upon there becoming present in said duct means at the upper side of said valve means a pre-set amount of particulate material, said supply means being operable to supply particulate material to said duct means at the upper end thereof and said receiving means being operable to receive particulate material from the lower end of said duct means and to transfer the material therefrom.

17. A method of feeding particulate material through particulate material feed means according to Claim 16, wherein during periods of continuous material flow through said particulate material feed means said supply means supplies particulate material to said duct means at the upper end thereof, said valve means is maintained in an open condition and a body of said particulate material is maintained in said duct means which body of material substantially prevents gas flow through said duct means, and said receiving means receives said particulate material from the lower end of said duct means and transfers said particulate material therefrom.

17. A method of feeding particulate material through particulate material feed means according to Claim 16, wherein during periods of continuous material flow through said particulate material feed means, said supply means supplies particulate material to said duct means at the upper end thereof, said valve means is maintained in an open condition and a body of said particulate material is maintained in said duct means which body of material substantially prevents gas flow through said duct means, and said receiving means receives said particulate material from the lower end of said duct means and transfers said particulate material therefrom.

Amendments to the claims have been filed as follows 1. An airlock comprising downwardly extending duct means, a portion of the lengthwise extent of the interior of said duct means being bounded at the upper end thereof by first valve means and at the lower end thereof by second valve means, each of said first valve means and said second valve means being operable to obturate said duct means, said first valve means being such that upon there becoming present in said duct means at the upper side of said first valve means a first, pre-set amount of particulate material said first valve means is caused to assume an open condition and said second valve means being such that upon there becoming present in said duct means at the upper side of said second valve means a second, pre-set amount of said material said second valve means is caused to assume an open condition.

2. An airlock according to claim 1, wherein said second present amount is greater than said first pre-set amount.

3. An çirlook according to Clays 1 or 2, wherein one or both of said first and second Valve means is operable to assume an open condition by virtue of the weight of said pre-set amount of said material to the upper side cf the valve means.

4. An airlock according to Claims 1 or 2, wherein one or both of said first and second valve means is operable to assume an open condition by virtue of the volume of said pre-set amount of said material to the upper side of the valve mcans.

5. An airlock according to any one of the preceding claims, wherein one or both of said first and second valve means comprises a hinged flap.

6. An airlock according to Claim 5, wherein a counter weight is operably connected to said hinged flap.

7. An airlock according to any one of the preceding claims, wherein one or both of said valve means is a substantially full-bore valve means.

8. A method of feeding particulate material through an airlock according to any one of the preceding claims, wherein during periods of continuous material flow through said airlock said first valve means alternates between opcn and closed conditions, said second valve moans is maintained in an open condition, and a body of said particulate material is maintained in said duct means1 which body of material substantially prevents gas flow through said duct means.

9. A method according to Claim 8, wherein said particulate material is supplied by a supply means operable to supply particulate material to said airlock at a pre-set flow rate.

10. A method according to Claim 9, wherein said flow rate of said particulate material can be varied by control means.

11. A method according to any one of Claims 8, 9 or sso, wherein said particulate material is removed from the lower end of said duct means by a receiving means, said receiving means being operable to receive said material from said lower end of said duct means and to transfer said particulate material therefrom.

12. A method according to Claim 11, wherein said receiving means is a conveyor.

13. A method according to any one or Claims 8 to 12, wherein said particulate material is particulate tobacco.

14. Apparatus as substantially described herein and with reference to the drawing.

15. A method as substantially described herein and with reference to the drawing.

16. Particulate material feed means comprising material supply means, an airlock and receiving means, said airlock comprising downwardly extending duct means and valve means, which valve means is operable to obturate said duct means and to assume an open condition upon there becoming present in said duct means at the upper side of said valve means a pre-set amount of particulate material, said supply means being operable to supply particulate material to said duct means at the upper end thereof and said receiving means being operable to receive particulate material from the Lower end of said duct means and to transfer the material therefrom.