GB2115795A

GB2115795A - Equipment for the volumetric dispensing for bulk material

Info

Publication number: GB2115795A
Application number: GB08304431A
Authority: GB
Inventors: Hans Heinzer
Original assignee: Schweizerische Industrie Gesellschaft
Current assignee: Schweizerische Industrie Gesellschaft
Priority date: 1982-02-19
Filing date: 1983-02-17
Publication date: 1983-09-14
Also published as: IT8367186A0; SE8300871L; DE3303655A1; JPS58152722A; SE8300871D0; IT1161484B; GB8304431D0

Abstract

A feed screw (20) is arranged vertically in a cylindrical housing (18) below the main body of a supply container (12), and is provided with a first drive (22) for rotation and with a second drive (28) for axial displacement. The feed screw is rotated and moved upwardly out of the feed-screw housing (18), flowable material thereby being passed into the housing (18). By opening closure flaps (15 and 16) and at the same time by moving the feed screw (20) axially towards the dispensing end (14), an accurately metered quantity of material is delivered. The axial movement of the feed screw (20) combined with its rotation prevents the formation of bridges. <IMAGE>

Description

SPECIFICATION Equipment for the volumetric dispensing of bulk material The present invention concerns equipment for the volumetric dispensing of bulk material In volumetric metering by means of a feed screw, the dispensed quantity, apart from depending upon the diameter and pitch of the feed screw, also depends upon the rate of revolution and upon the operating time. A normal metering screw is adequate for the metering of coarse material, such as sand, gravel or the like, since in this case the quantity concerned rarely has to be accurately maintained, and variations can be readily taken into account.

In packaging operations, however, the accuracy achieved in measuring out quantities in this way is not adequate, and additional measuring devices, such as weighing equipment or the like, are necessary in order to enable the required accuracy to be obtained.

For the purpose of dealing with very small quantities of material that flows very readily, such as for example powders used in the chemical or pharmaceutical industry, CH-A477,342 proposes that a perforated baffle plate should be fitted in the housing immediately to the rear of the end of the feed screw.

In this way, continued flow of the material can be prevented, and only the precise amount of material that is delivered by the feed screw is dispensed. Since the use of such metering equipment is limited to bulk material which flows readily, the formation of bridges in the material does not have to be taken into account.

If, on the other hand, the bulk material involved is substance which flows less readily and which exhibits considerable cohesion, such as for example soap flakes, or which tends to cake easily, for example, flour or other known pulverulent foodstuffs, then the quantity measured out in this way does not always correspond to the intended amount.

The invention of CH-A 505,371 is intended to prevent the formation of bridges and for this purpose, in the case of a feed screw arranged below the supply container, a knife-like edge is provided on at least those threads of the feed screw that lie below the delivery opening of the supply container. A feed screw of this kind cuts into the material but does not compress it in the manner observed when the edges are biunt. Here again, however, the material is moved along while in its particular state of denseness, so that different quantities of like volume are nevertheless dispensed.

A further method is proposed in SU-A 720,304. The metering screw, also arranged horizontally below the supply container, is provided with a drive for rotating it and with a drive for imparting translatory movement thereto.

By rotating, the feed screw turns in the material in the direction away from the delivery point, and during the axial ejection movement and simultaneous rotation, a certain quantity of material is passed into a dispensing shaft. The dispensing shaft is closed by a cut-off slide which is actuated in synchronism with the ejection movement. A bridge may also be formed in the supply container when this arrangement is used.

Because of the ejection movement, pressure is exerted on the material since the dispensing shaft is arranged at right angles to the feed direction of the screw. This is not, however, desirable in all cases.

An object of the present invention is, therefore, to provide equipment for the volumetric dispensing of bulk material, by means of which equipment precise quantities of bulk material can be dispensed in rapid sequence.

According to the invention, this is achieved by the features defined in Claim 1.

Embodiments of the invention will now be described by reference to the drawings, in which: Figs. 1 and 2 are diagrammatic sectional views of volumetric dispensing equipment in two different operating positions and comprising a single feed screw, and Fig. 3 is a sectional view of the housing with a double feed screw.

A supply container 12, charged through a duct 11, is secured to a machine part 10. The supply container 1 2 may be of pear-shaped construction and is open at the wider end 13 and closed off at the lower end 14 by a two-part closure flap 15, 16. The dispensing shaft 17, upstream of said lower end 14, takes the form of a tubular housing 1 8 for a metering screw 20 having a vertically extending axis.

The metering screw 20 is connected by means of a drive shaft 21 to a motor 22 which has a reduction gear and is arranged above the supply container 12. The motor 22 is secured to a slide 23 which is vertically displaceable on rails 24. By means of a tie-rod 25, coupled to a double-armed lever 26, the slide is attached to a conncting rod 27 actuated by an eccentric drive 28. The eccentric drive 28 consists of a cam disc 30 having a guide channel 31 and a probe roller 32, which is secured to and rotates on a drive lever 33 coupled to the machine part 10.

The point at which the connecting rod 27 and the double-armed lever 26 are attached to each other is adjustable, since one of the lever arms, arm 40, contains a slot 41 and the connecting rod 27 is pivotally secured in this slot 41 by means of a pin 42, for example, the shank of a screw-bolt.

In the manner known to any expert in packaging technique, the parts 1 5 and 1 6 of the closure flap are connected to the eccentric drive 28 in such manner that the two parts 1 5 and 1 6 execute a movement in the direction indicated by the arrows A when the connecting rod 27 moves in the direction indicated by the arrow B.

The mode of operation of this equipment for the volumetric dispensing of bulk material is as follows: Flowable material is passed to the supply container 12 through the duct 11 until the level control means 1 9 indicates that the container 12 is full. With rotation of the feed screw 20 in direction indicated by the arrow c, said feed screw 20 is moved upwardly out of the material from the position shown in Fig. 1 to that illustrated in Fig. 2.Upon simultaneous opening of the parts 1 5 and 1 6 of the closure flap the feed screw 20 is pushed downwardly by means of the eccentric drive 28 so as to eject all of the material located in the housing 18 and between the end of the feed screw 20 and the closure flap, the feed screw 20 being displaced, without rotation, in the axial direction from the position shown in Fig. 2 into that illustrated in Fig. 1.

By suitable selection of the rate of revolution, the lift and the pitch of the turns of the feed screw 20, the feed quantity can be adjusted to suit the particular bulk material, e.g. the rotary movement and the lifting movement can be correspondingly selected, so that the feed screw is extracted from the material without relative movement, or different dimensions can be used so as either to loosen or compress the material. Furthermore, an additional feed movement can be carried out so as to offset the volume of the feed screw or to effect additional compression of the material. If on the other hand, the lifting movement is greater than the pitch of the feed screw, loosening of the material is effected.

In a variant, the lifting movement could be accompanied by rotation of the feed screw during ejection of the material in order either to supply additional material or, during rotation in the opposite direction, to hold back the material, as provided for in the initially described arrangement in accordance with CH-A 477342.

Figure 3 shows a housing 50 with two interengaging feed screws 51 and 52 for a feed arrangement comprising a double screw, the feed screws 51 and 52 rotating in opposite directions as indicated by the arrows D and E. The other parts for rotating and lifting the feed screws can be seen from Figs. 1 and 2.

Instead of an eccentric drive 28 for lifting and lowering the feed screw 20, use could be made of a pneumatic or electromagnetic drive. For the purpose of synchronizing the rotary movement, the lifting movement and the opening movement of the closure flap, an electronic control means with individual drives could be provided. A combined system would also be possible wherein the rotary movement could be derived from the lifting movement by means of a toothed rack or a coarse-thread spindle.

Claims

1. Equipment for the volumetric dispensing of bulk material in a packaging machine and comprising at least one feed screw for passing the bulk material from a supply container to a dispensing point which feed screw is contained in a cylindrical housing and is driven in the rotary and axial directions, wherein the axis of the housing extends downwardly from the supply container and at least a portion of the feed screw projects into the supply container.

2. Equipment according to Claim 1, wherein the longitudinal axis of the housing is disposed at least approximately vertically, and the point at which the longitudinal axis intersects the supply container lies at the lowermost point of the latter.

3. Equipment according to Claim 2, wherein the supply container and the housing are of rotationally symmetric shape and have a common vertical axis.

4. Equipment according to any one of Claims 1 to 3, comprising a first drive for the rotary movement of the feed screw and a second drive for the axial movement of the feed screw.

5. Equipment according to Claim 4, wherein the two drives are synchronized with each other.

6. Equipment according to Claim 5, wherein the pitch and diameter of the feed screw on the one hand, and the lift, displacement speed and rate of revolution on the other hand, are adjusted to the material being processed in order to loosen or compact the material prior to dispensing it.

7. Equipment according to Claim 5 or 6, wherein the dispensing point is located on the axis of the housing, and a closure flap actuated in synchronism with the lift-imparting drive is provided for closing off the dispensing orifice.

8. Volumetric dispensing equipment substantially as hereinbefore described with reference to the accompanying drawings.