GB2091672A

GB2091672A - Bucket wheel-type entrance lock

Info

Publication number: GB2091672A
Application number: GB8201546A
Authority: GB
Original assignee: Waeschle Maschinenfabrik GmbH
Current assignee: Waeschle Maschinenfabrik GmbH
Priority date: 1981-01-23
Filing date: 1982-01-20
Publication date: 1982-08-04
Also published as: IT8219186A0; IT1150116B; DE3102153A1; NL8105513A; LU83884A1; BE891869A; SE8200188L; ZA82142B; FR2498574A1; DK28482A; NO820196L; CH654273A5; AU7921782A; JPS57141321A

Abstract

A gravity-operated, bucket wheel-type entrance lock has a feeding and discharge duct (3) of a substantially rectangular cross section. The mouth of the discharge duct (3) is covered with a partition (3a to 3f) provided with a discharge cut- out (10) the cross-sectional area of which is smaller than that of the discharge duct (3). Jets of pressurized air are directed from a lateral wall (5) of the lock housing in the bucket situated above the discharge cut-out (10) to assist in uniform discharge of the loose material from the bucket. <IMAGE>

Description

SPECIFICATION Bucket wheel-type entrance lock The present invention relates in general to entrance locks or valves, and in particular to an entrance lock having a housing defining a chamber bounded by a cylindrical wall and two lateral walls, a bucket wheel supported for rotation on the lateral walls, an inlet duct of rectangular cross section, an outlet opening opposite the inlet duct, and means for introducing pressurized air into the bucket or compartment adjoining the outlet opening.

Bucket wheel entrance locks in pneumatic devices are generally known for transporting and, if desired, for dosing loose material. Such prior-art entrance locks or valves are made either in the form of discharge locks in which the loose material is fed perpendicularly from above in the lock housing and is discharged also perpendicularly by the force of gravity from the outlet opening in the lower part of the housing upon the rotation of the bucket wheel exactly by half its cycle (German Patent 608 765). Also known are flowthrough entrance locks in which the fed-in loose material, upon a half rotation of the bucket wheel, is immediately discharged in a stream of conveying air which is horizontally blown-in through a lateral flanged cover and escapes from an opposite flanged cover into a conveying duct (German published patent application 1 926915).

Each of the two types of entrance lock has its specific advantages and disadvantages. The gravity-operated lock enables high charges, can be easily adjusted by means of suitable adapter pieces arranged between the discharge opening of the lock and the feeding duct to almost any diameter of the feeding conduit, and is relatively abrasion-resistant. On the other hand, when used for loose material which has a tendency to adhere on the walls of the lock, an incomplete discharge of the buckets of the wheel takes place even if a relatively large pressure difference between the inlet and outlet sides is available. In contrast, the blow-through types of entrance locks, due to the discharge of the pressurized air, are less sensitive to adherent loose material.In spite of higher pressure differences between their inlet and outlet, relatively small charges can be loaded into the lock, and the free selection of the diameter of the feeding conduit is possible only within low limits, and the outlet of the lock is prone to wear.

Accordingly, without adverse operational conditions, usually the gravity-type entrance lock is preferred to the blow-through type.

Also known are hybrid forms of the two kinds of entrance locks. For example, German Patent 597 492 teaches a gravity entrance lock in which, for improving the discharge of respective buckets and for keeping a clean gap between the inner wall of the housing and the bucket wheel, the latter is closed at its end and both end walls of each bucket are provided with a channel opening at the bottom of the bucket in such a manner that, when the latter is rotated into its discharge position, it is brought into register with a pressurized air-feeding channel arranged in the lower part of both lateral flanged covers of the housing, and consequently the loose article is discharged from the bucket by the force of gravity under the assistance of the blown in pressurized air.

From the Swiss patent 339 963 a gravity-type entrance lock is known in which the buckets of the wheel are open and, in order to improve the discharge of adhesive loose material, the buckets when brought to their discharge position register with an opening in one of the flanged covers of the housing which communicates with a horizontally directed pipe through which all pressurized air needed for the subsequent transportation of the material is blown into the bucket.

A common feature of all known bucket wheeltype entrance locks, however, is the fact that the discharge of loose material, due to the dosed or intermittent charges into respective buckets of the wheel, is not uniform but its frequency depends on the rotary speed of the bucket wheel and on the number of individual buckets. It is true that this intermittent or pulsating discharge is acceptable in most applications; nevertheless, in certain applications, for example in feeding pulverized solid fuels such as coal dust into burners, such situations cannot be toleranced since, for achieving an economic burning operation, a stable flame is necessary.

There is thus a need for a generally improved bucket wheel-type entrance lock, particularly one which, while preserving the characteristic advantages at the outlet of a gravity-operated lock, provides for a uniform and constant, with respect to time, stream of loose material.

According to the present invention there is provided a bucket wheel-type entrance lock comprising a housing enclosing a chamber bounded by a cylindrical wall and two lateral walls; a bucket wheel supported on said lateral walls for rotation in said chamber; a feeding duct communicating with an upper part of said chamber; a discharge duct communicating with a lower part of said chamber opposite said feeding duct; a partition arranged at the mouth of said discharge duct in said chamber, said partition defining a discharge cut-out the cross-sectionai area of which is smaller than the cross-section of said discharge duct. Preferably the lock has a rectangular outlet channel for a loose material, with a discharge opening or cut out which, in the range facing the buckets of the wheel, has a smaller cross-sectional area than that of the outlet channel.

In contrast to conventional designs, in which the cross section of the discharge opening is held as large as possible, that is with respect to structural characteristics of the lock, the cross section of the outlet has been made equal to the cross section of the feeding duct in order to achieve a prompt and complete discharge from the consecutive buckets of the wheel orbiting across the outlet duct, the construction according to this invention has surprisingly proved that a certain reduction of the cross-sectional area of the discharge opening relative to the outlet duct, in connection with pressurized air injected into the bucket when the latter is in its discharging position, either completely or at least almost completely eliminates any pulsation and time fluctuations resulting from such pulsations of the load of loose material in the subsequent conveying conduits, even at relatively low rotary speeds of the bucket wheel. The cause of this effect is not yet known in detail.

The degree of uniformity of the discharge of the loose material is also affected by the blown in air, namely by the kind and the location of the pressurized air stream in the buckets of the wheel and by the configuration of the open discharge area.

Particularly advantageous is the embodiment in which the pressurized air is introduced into the discharging bucket from both lateral flanged covers so that the feeding of pressurized air from two opposite directions causes a particularly intensive whirling of the loose material. In addition, loose material is kept apart from the end wall of the bucket in the range of the rotary axle and from the inner walls of the flanged covers, and consequently any wear in these areas is substantially reduced.

Of particularly advantage is also the embodiment in which the reduced outlet opening has a symmetric configuration of its boundary edges relative to a central line directed perpendicularly to the axle of the bucket wheel.

This symmetrical configuration, in connection witlS the two-sided feeding of pressurized air, ensures an optimum time uniformity of the discharged stream of loose material, even if the bucket wheel is constructed with relatively few buckets and operated at low rotary speed.

For a better understanding of the present invention itself, however, both as to its construction and its method of operation, reference will now be made, by way of example, tc the accompanying drawings, in which: FIG. 1 is a perspective view illustrating a first embodiment of an entrance lock of this invention; FIG. 2 is a sectional side view of the embodiment of FIG. 1; and FIGS. 3-7 are bottom views in the direction of arrow X of the embodiment of FIG. 2 illustrating respectively modifications of the outlet opening of the lock.

The bucket wheel-type entrance lock or valve is assembled of a housing 1 formed with an inlet duct 2, an outlet or discharge duct 3, a cylindrical space closed at each end thereof by flanged covers 4 and 5 which support for rotation a shaft 7 of a bucket wheel 6. The individual buckets of the wheel 6 are formed by radial vanes 8 secured to the shaft 7 by welding for example. The bucket wheel 6 rotates counterclockwise in the direction of arrow 9, whereby the open edges of vanes 8 sweep successively past the inlet duct 2 where the buckets between the vanes are charged with the loose material, whereupon the buckets are discharged through the juxtaposed outlet duct 3.

While in conventional bucket wheel locks of this kind the entire cross-sectional area of the discharge duct 3 constitutes the discharge openings in the entrance lock of this invention, the mouth of duct 3 is partially covered to define an opening 10 having a smaller cross-sectional area than the cross section of the subsequent discharge duct 3. The outline of respective buckets corresponds substantially to the full crosssectional area of the inlet and outlet ducts 2 and 3, and loose material in the bucket which is rotated into its discharging position opposite the discharge opening 10 is acted upon by pressurized air V, which is introduced in horizontal direction, as shown by arrow 1 8 in Fig. 1 , through opening 11 in the lateral flanged cover 5.This horizontally directed pressurized air stream, together with the vertically acting force of gravity, combine to discharge loose material from one compartment or bucket of the wheel 6 through the relatively small cut-out 10 into the larger discharge duct 3.

From the vertical cross section according to FIG.

2, it can be seen that the lateral opening 11 for the stream of pressurized air is formed in the lower part of housing 1 below the shaft 7 of the wheel.

In this embodiment, the opposite flanged cover 4 is also formed with a similar connecting piece 1 5 for an oppositely directed pressurized air stream V', introduced in the upper part of housing 1 above the shaft 7. The connecting piece 1 5 communicates with a recessed annular space 14 in the flanged cover 4 delimited by an end partition 1 3 which in the range of the mouth of the discharge duct 3 is formed with an air outlet opening 12 facing the air outlet of the connecting piece 1 The outlet opening 12 is directed upwardly toward the shaft 7.In this manner, the second stream of pressurized air is directed past the bearing of the shaft 7 of the bucket wheel, so as to entrain any dust from the loose material and to build up an overpressure in the chamber 14, which prevents entry of dust from the buckets.

Thereupon, the discharged air jet through the opening 12 joins the first air jet through the connecting piece 11 in imparting a whirling movement to the loose material to be discharged.

FIGS. 3-7 show respectively a bottom view (seen in direction of arrow X) of the bucket wheel entrance lock of FIG. 2. The direction of rotation of the bucket wheel 6 is indicated by arrows. It will be seen that the mouth of discharge duct 3 in housing 1 is reduced in cross section relative to the larger rectangular cross section of the duct 3 by partitions 3a-3f defining cut-outs 10 of different shapes. The cross-sectional area of each cut-out 10 is always smaller than the total cross section of the discharge duct 3. The partitions 3a-3f are either an integral part of the discharge duct 3, as is the case in the embodiment according to FIG. 2, or they can be formed in the bottom wall of housing 1 (FIG. 1).The cut-outs 10 can be shaped either asymmetrically with respect to a central line of the cross section of the duct 3 (FIGS. 3 and 4) or symmetrically (FIGS. 5-7).

The symmetric configuration of the cut-outs 10 is advantageous particularly in connection with the two-sided introduction of pressurized air into the bucket to be discharged. In any of these configurations, the length "a", corresponding to the maximum length of the cut-out in direction perpendicular to the axis of rotation of the bucket wheel, should be almost equal to the corresponding side of the discharge duct 3, whereas the length "b", corresponding to the maximum length of the cut-outs in the direction parallel to the axis of shaft 7 equals approximately the other side of the rectangular cross section of the duct 3.The discharge opening 10 in the embodiment of FIG. 3 has the shape of a right triangle with a straight hypotenuse, in the embodiment of FIG. 4 of a right triangle with a curved hypotenuse, in the embodiment of FIG. 5 the opening 10 is in the form of an equilateral hyperbolic sector, in FIG. 6 of an equilateral triangle, and in FIG. 7 is in the form of a square with diagonals corresponding to the maximum dimensions "a" and "b". In all these embodiments it is essential, for achieving a time uniformity of the discharged stream of the loose material, that the maximum breadth b of the cut-out lObe decreased in size along the length a, that is perpendicularly to the axis of rotation of the wheel 6.The decrease of the breadth b depends on construction and operational parameters of the entrance lock, and also the resulting shape of the cut-out 10 in relation to the rotational direction of the bucket wheel 6 determines optimum results as regards the uniformity of the discharged stream. It will be seen from FIGS. 3-6 that the opening 10, when viewed in the direction of rotation of the shaft 7, increases from a minimum cross-sectional area to a maximum value, whereas in FIG. 7 there is shown an embodiment in which the crosssectional area of opening 10 initially increases to a maximum value in the range of the axis of rotation of the shaft 7 and then again decreases to a minimum value.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in specific examples of an entrance lock, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.

Claims

1. A bucket wheel-type entrance lock comprising a housing enclosing a chamber bounded by a cylindrical wall and two lateral walls; a bucket wheel supported on said lateral walls for rotation in said chamber; a feeding duct communicating with an upper part of said chamber; a discharge duct communicating with a lower part of said chamber opposite said feeding duct; a partition arranged at the mouth of said discharge duct in said chamber, said partition defining a discharge cut-out the cross-sectional area of which is smaller than the cross-section of said discharge duct.

2. A bucket wheel-type entrance lock as claimed in claim 1, wherein said means for introducing a pressurized medium includes an opening in a lateral wall for directing pressurized medium includes an opening in a lateral wall for directing pressurized air to the bottom region of a bucket of the wheel situated above said discharge cut-out.

3. A bucket wheel-type entrance lock as claimed in claim 2, wherein said pressurized air opening is in the form of a slot.

4. A bucket wheel-type entrance lock as claimed in claim 3, wherein said slot extends substantially parallel to the circular path of buckets of the wheel.

5. A bucket wheel-type entrance lock as claimed in claim 4, further including an additional opening for pressurized air formed in the other wall opposite said first-mentioned pressurized air opening.

6. A bucket wheel-type entrance lock as claimed in claim 5, wherein said lateral walls have the form of removable flanged covers, said first pressurized air opening being formed in one cover in the lower part of said housing, and said additional pressurized air opening in the opposite cover communicating via a radial channel with a connecting piece located in the upper part of said housing so that the incoming air creates an overpressure in the bearing region of said bucket wheel to rinse said bearing region.

7. A bucket wheel-type entrance lock as claimed in claim 1 , wherein said discharge cut-out has a first maximum clearance in axial direction of said bucket wheel, said first maximum clearance being slightly smaller than the corresponding clearance of said discharge duct, and a second maximum clearance in the direction perpendicular to the axis of rotation of said bucket wheel, said second maximum clearance being slightly smaller than the corresponding side of the discharge duct.

8. A bucket wheel-type entrance liock as claimed in claim 7, wherein said first maximum dimension of said cut-out continuously decreases in the direction of rotation of said bucket wheel over the entire cross-sectional area of said discharge duct.

9. A bucket wheel-type entrance lock as claimed in claim 7, wherein said first maximum dimension of said discharge-cut-out extends parallel to the axis of rotation of said wheel and continually decreases at one half of the cross section of said discharge duct when considered in the direction of rotation of said bucket wheel and continuously increases at the other half of said discharge duct.

10. A bucket wheel-type entrance lock as claimed in claim 8, wherein said discharge cut-out has a triangular configuration.

1 A bucket wheel-type entrance lock as claimed in claim 9, wherein said discharge cut-out has a square configuration with a diagonal extending parallel to the axis of rotation of the bucket wheel.

12. A bucket wheel-type entrance lock as claimed in claim 7, wherein said discharge cut-out has a configuration of a hyperbolic sector the base of which corresponds to said first maximum dimension and the height of which corresponds.

to the second maximum dimension.

13. A bucket wheel-type entrance lock substantially as hereinbefore described with reference to the accompanying drawings.