The subject invention concerns a method to be per¬ formed in connection with a compartment for receiving powder material for the purpose of reducing the arching tendency of the powder material inside the compartment by actuating the material and/or the container enclosing the compartment so as to cause movement of said material.

One problem encountered in the discharge of particulate bulk material through an outlet at the bottom of a container into the interior compartment of which the material is intended to be received, is to avoid arching of the material at the discharge end of the container. One solution used in the past to solve this problem is to actuate the material and/or the container enclosing the material-receiving compartment in such a manner as to induce movement of the material. This is achieved either with the aid of scraping elements arranged to move continuously backwards and forward inside the container to induce movement of the material enclosed therein, or else by subjecting the container to continuous impacts. However, these methods tend to cause compacting of the material at the lower part of the com¬ partment with resulting difficulties in discharging the powder material. The purpose of the subject invention thus is to solve this problem in a simple and efficient manner.

This purpose is achieved by means of a method in accord ance with the subject invention which is essentially characterized therein that the material-affecting operation is carried out intermittently.

A further purpose of the subject invention is to provide a device which operates in a simple and efficient manner and which is adapted for performing the method of the kind outlined in the aforegoing.

This further purpose is achieved by means of a device in accordance with the subject invention which device is characterized essentially therein that the movement - inducing means acting on the material and/or the housing is connected to an intermittently operating feeder unit via drive transmission means.

One embodiment of the invention will be described in closer detail in the following with reference to the accompanying drawings, wherein Fig. 1 illustrates a powder material receiving container together with its associated operating device and powder material metering apparatus,

Fig. 2 is a sectional view through the operating device, Fig. 3 illustrates the various components incorporated in the device when interconnected, and

Fig. 4 is a sectional view through the discharge part of the container and the powder material metering apparatus.

With reference to the drawings, the container 1 illu- strated therein which preferably has a frusto-conical con¬ figuration and is adapted to receive in its interior com¬ partment 2 particulate bulk material 3, is equipped at its lower part with a powder material metering apparatus 4 or other suitable conveyor apparatus adapted to discharge the desired quantity of powder to the intended reception station, the latter preferably being removably attachable to the device. On one of the external housing walls 5 of the container or in any other desired position externally of and/or in the interior of the container 1 is arranged _a percussion piston unit 6 or other suitable movement- inducing mechanism, which is secured e.g. by fastening elements, such as fastener bolts 7 extending through the container wall 5, or in any other way to ensure that the powder material 3 inside the container 1 may be affected whenever desired. For example, the piston unit 6 may consist of a cylinder 8 in the interior cylindri- cal space 9 of which is mounted a piston 10 for movement therein. The

piston 10 is adapted to be actuated by air 11 which is supplied into said cylindrical space 9 for the purpose of discplacing the piston 10 with a view to induce movement of the material 3 contained in the interior of the container 1 and/or the housing enclosing the container compartment for the purpose of causing movement of said means and con¬ sequently to reduce the risk of arching of the powder mate¬ rial 3 inside the container 1. Preferably, the piston 10 is arranged to be driven by air 11 against the action of a spring 14 or other means which provides a yieldable force and which actuates the piston 10 in such a manner that the latter is displaced away from the container 1 or from the intended point of impact as the air is being evacuated, for example through a passage 15 leading to the exterior. A combined attachment and impact plate 16 may serve as the place of impact of the piston 10. The plate 16 could be connected on the one hand to the cylinder 8, for instance by means of screws 17 and on the other it could be posi¬ tioned so as to abut against and be closely affixed to the container wall 5 by means of bolts 7, as is shown for example in Fig. 2.

The above-mentioned movement-inducing operation is intended to be carried out intermittently with a view to reduce the risk of arching of the particulate material 3 inside the container 1, but additionally it serves to avoid compaction of the powder material 3 inside the con¬ tainer 1 and in the area of the outlet mouth 18 communi¬ cating the interior powder material-reception compartment 2 of the container with the powder metering apparatus 4. The motion-inducingimpacts or other operations in¬ tended to affect the material and/or the container could be controlled by the feeder unit 19 which operates the powder material metering apparatus 4. In accordance with the preferred embodiment illustrated in the drawings, the feeder unit 19 comprises an air-operated piston 20 which by means of a hose or other suitable drive transmission means 21, 22, 22 is directly or indirectly coupled to

the piston unit 6, and an intermittently operating step advancement mechanism 23 which actuates the powder material metering apparatus 4 and which is driven by the metering feeder piston 20. Preferbly, the metering piston 20 is connected to the percussion piston 6 in such a manner that return air from the metering piston 20 directly or via a control unit 24 is supplied to the piston unit 6 so as to intermittently actuate the latter for the purpose of shaking the powder 3 inside the container 1 by exposing the housing wall 5 of the container to percussions inter¬ mittently.

The powder material metering apparatus 4 which prefer¬ ably is a rotationally driven screw conveyor which is mounted inside a tubular conveyance tube 25 and which in- side the gap 27 defined between the tube 25 and the screw 26, receives and advances powder material 3A in the desired direction of conveyance 28. For instance, the powder metering apparatus 4 may be in communication with an associated bulk container on the external wall of which the above- mentioned powder material container 1 may be attached by means of screws passing through suitable lugs 29 formed on said powder container 1.

At one of its ends, the metering screw conveyor 26 is rotationally mounted in a suitable bearing 30. A driving wheel 32 with driving teeth 31 thereon is intended to serve as a ratchet wheel via a coupling member 33 which is con¬ nected with the metering piston 20, said wheel 32 being non-rotationally connected to the metering screw 26. A suitable protective shield 34 encloses the driving wheel 32 so as to prevent access to the same from the outside.

The control unit 24, finally, may comprise regulating means 35 arranged to regulate the amount of air that is supplied to each one of the pistons 6 and 20 and/or the intervals of air exchange concerning these pistons. A hose 36 supplying compressed air from a compressor or from another suitable source of driving power is arranged to supply compressed air to the control member 37 of the

control unit 24 for further transfer thereof to the metering piston 20 and its enclosing cover and for actuation of the piston, resulting in extension of the piston rod 20A and the coupling member 33 in the operating direction 38. As a result, the driving wheel 32 is actuated by the couplin member 33 to move in one 39 of its directions, whereupon the metering screw 26 consequently will be rotated in the corresponding operative direction 39 with consequential metered discharge of the powder in the direction of con- veyance 28 of the powder. The feeder piston 20 and its enclosing housing are connected to the control unit on the return side of the piston via the hose 22 in order to return compressed air from the piston 20 when the latter returns to its initial position illustrated in Fig. 4. In this position, it is ready to again actuate the driving wheel 32. During the return movement, the coupling member 33 can pass freely along the teeth 32 on the driving wheel because the direction of inclination of the teeth is the opposite to that of the direction of drive 39. Return air from the feeder piston 20 thus will be supplied to the operative side of the percussion piston unit 6 inside the cylindrical space 9 thereof via hoses 22, 22 , preferably from the control unit 24, at the same intermittent rate as that with which the piston 20 is actuated to move in its operative driving direction 38.

Upon spring actuation of the piston 10 in the direction indicated by numeral 40, opposite to the direction of impact 11, when the driving force of the supplied air is exhausted, the air is allowed to flow from the cylindrical space 9 of the piston via the hose 15, e.g. to the outside. Air supplied to the percussion piston 10 could be controlled to act on the latter for to-and-fro movements thereof at varying intervals and thus need not move in correspon¬ dence with the movement of the piston 20. As should be apparent from the aforegoing the inven¬ tion provides a simple and reliable device by means of which a simple and efficient method may be realized. The

invention is not limited to the embodiment illustrated in the drawings and described herein but a number of modi¬ fications are possible within the scope of the appended claims without departure from the inventive idea.