EP0888811A2

EP0888811A2 - Mixing apparatus

Info

Publication number: EP0888811A2
Application number: EP98305267A
Authority: EP
Inventors: George Stewartson c/o Fillworth Limited Cockbain
Original assignee: Fillworth Ltd
Current assignee: Fillworth Ltd
Priority date: 1997-07-03
Filing date: 1998-07-02
Publication date: 1999-01-07
Also published as: GB9713967D0; EP0888811A3

Abstract

Mixing apparatus comprises a container (2) and a mixing mechanism (8) mounted within the container (2), the mechanism (8) including a driven shaft (10) and a mixing disc (22) mounted on said shaft (10) to be movable axially relative to the shaft (10) and so arranged that, on initial rotation of the shaft (10) in one direction, the disc (22) moves from a predetermined upper position on the shaft (10) to a predetermined lower position on the shaft (10) where it remains on continued rotation of the shaft (10) in said one direction, and, on initial rotation of the shaft (10) in the opposite direction, the disc (22) moves from said predetermined lower position on the shaft (10) to said predetermined upper position on the shaft (10) where it remains on continued rotation of the shaft (10) in said opposite direction. Preferably the disc (22) is bladed, co-operating helical means (20,28) reacting between the shaft (10) and the disc (22) to control the axial movement of the disc (22) along the shaft (10).

Description

This invention relates to industrial mixing apparatus, and has particular application to such apparatus for mixing powder-based materials such as adhesives, paints, inks and the like into homogeneous liquid solutions.

When mixing powders into liquid solutions, the powders are initially fed into the upper regions of a container or bowl containing the liquid with which the powder is to be mixed. The container houses a mixing mechanism comprising a mixing disc mounted on the end of, to be rotatable with, a driven shaft. In order to ensure thorough mixing, or wetting out, of the powder as it enters the liquid, it is conventional practice for the shaft and attached disc to be movable vertically within the container between a normal operating position, in which the disc is located in the lower/central regions of the container for the fundamental mixing operation, and a raised position in which the disc is located in the upper regions of the container to ensure initial mixing or wetting out of the incoming powder.

This raising and lowering of the rotatable shaft and disc can be achieved by means of, for example, a hydraulically-operated hoist external of the container and to which the shaft is attached for the necessary vertical movement.

However, such an arrangement has a number of disadvantages, not the least of which are that hoists are expensive pieces of equipment, the headroom above the container needed to accommodate the hoist in its raised position is substantial, and the raising and lowering of the shaft/disc is a laborious and time consuming exercise, while the constant vertical and rotational movement of the shaft relative to the seal through which it passes in the lid of the container can result in damage to or breakage of that seal, and consequential environmental problems.

It would be desirable to be able to provide mixing apparatus incorporating a mixing disc which can be raised and lowered in the associated container in a quicker, simpler and less expensive manner than heretofore.

According to the present invention there is provided mixing apparatus comprising a container and a mixing mechanism mounted within the container, the mechanism including a driven shaft and a mixing disc is mounted on said shaft, characterised in that the mixing disc mounted on the shaft to be movable axially relative to the shaft and is so arranged that, on initial rotation of the shaft in one direction, the disc moves from a predetermined upper position on the shaft to a predetermined lower position on the shaft where it remains on continued rotation of the shaft in said one direction, and, on initial rotation of the shaft in the opposite direction, the disc moves from said predetermined lower position on the shaft to said predetermined upper position on the shaft where it remains on continued rotation of the shaft in said opposite direction.

It will be appreciated that, with such an arrangement, movement of the mixing disc between a lower normal mixing position at or adjacent one end of the driven shaft in the lower/central regions of the container, and a raised position at or adjacent the other end of the driven shaft in the upper regions of the container can be achieved merely by reversing the direction of rotation of the driven shaft. Thus, as and when it is necessary to ensure initial mixing or wetting out of powder being fed into the upper regions of the container, the shaft is driven in a direction to ensure movement of the mixing disc to its upper position thereon.

In a preferred embodiment of the invention, the disc includes a central hub having a bore through which the driven shaft extends, co-operating helical means reacting between the external surface of the shaft and the internal surface of the hub of the disc, the radially outer regions of the disc comprising a plurality of circumferentially spaced blades the plane of each of which makes an acute angle with a transverse plane centrally through the disc, the blades extending symmetrically to each side of said central plane.

In one embodiment of the invention, the outer surface of the shaft carries a helical projection thereon and the internal surface of the hub has a correspondingly helical groove formed therein to receive said projection.

The helical projection may be continuous between the positions on the shaft determining the upper and lower positions of the disc thereon, or, alternatively, said projection may be discontinuous and comprise a plurality of spaced sub-projections.

In an alternative embodiment of the invention, the outer surface of the shaft has a helical groove formed therein, a correspondingly helical projection being provided on, to extend radially inwardly from, the inner surface of the hub of the disc to be received in said groove.

Conveniently the shaft carries abutment means thereon for engagement by the disc to determine the upper and lower positions of the disc on the shaft.

By way of example only, an embodiment of the invention will now be described in greater detail with reference to the accompanying drawings of which:

Fig. 1 shows mixing apparatus according to the invention;

Fig. 2 shows the mixing mechanism of the apparatus of Fig. 1, and

Figs. 3 to 6 show details of the mechanism of Fig. 2.

Referring to the drawings, the illustrated apparatus comprises a conventional liquid container 2 with a lid 4 having a feed inlet 6 for powder.

A mixing mechanism is indicated generally at 8 and comprises a shaft 10 which extends into the container 2 through a seal in the lid 4, the shaft 10 being driven by a reversible motor 12 through bearings and couplings 14. The motor 12 may be electrically or hydraulically powered.

The shaft 10 carries a pair of

stop members

16,18, the stop member 16 being secured to the shaft 10 adjacent the lower end of the shaft 10, and the stop member 18 being secured to the shaft 10 at an intermediate region of the shaft 10.

A helical projection or rib 20 is provided externally of the shaft 10 between the stop members 16,18 (see in particular Fig. 3), while a mixing disc indicated generally at 22 is mounted on the shaft 10 between the stop members 16,18 (see in particular Figs 4 and 5).

More particularly, the disc 22 includes a central hub 24 having a bore 26 through which the shaft 10 freely passes, a helical groove 28 being formed in the internal surface of the hub 24 to extend the length of the hub 24 as indicated in Fig. 6.

The groove 28 in the hub 24 receives therein the helical projection or rib 20 on the shaft 10 whereby the disc 22 is located on the shaft 10.

The disc 22 further includes a substantially flat, annular intermediate disc portion 30 from the radially outer regions of which extend a plurality of circumferentially-spaced blades 32. Each blade 32 is twisted relative to the disc portion 30 and has an outer edge located at an acute angle to the plane of the disc portion 30, each blade 32 extending symmetrically to each side of the plane of the disc portion 30 as best seen in Fig. 2.

The described mixing mechanism is positioned within the container 2 as shown in Fig. 1 with the shaft 10 located centrally and vertically and with the stop member 16 within the lower regions of the container 2 and with the stop member 18 within the upper regions of the container 2.

The apparatus operates as follows.

With the disc 22 abutting the lower stop member 16 and on rotation of the shaft 10 in an anticlockwise direction as indicated by arrow A in Fig. 4, the co-operation between the rib 20 on the shaft 10 and the groove 28 in the hub 24 ensures that the disc 22 rotates with the shaft 10, while the configuration of the blades 32 of the rotating disc 22 is such that the forces applied thereto by the liquid medium within the container 2 tend to urge the disc 22 downwardly. Such movement is prevented by the stop member 16 and the disc 22 therefore rotates with the shaft 10 in this lower position to effect mixing of the contents of the container 2,typically a powder fed into the container 2 through the inlet 6 to be mixed with a liquid carrier within the container 2.

If it is desired to effect mixing within the upper regions of the container 2, for example to achieve wetting out of incoming powder fed to the container 2 through inlet 6, the direction of rotation of the shaft 10 is reversed to clockwise as indicated by arrow B in Fig. 5. The forces applied to the rotating disc 22 are now such as to urge the disc 22 upwardly within the container 2 as indicated by the arrow C in Fig. 5, the result being that the disc 22 is rotated at a speed greater than that of the shaft 10 and moves upwardly relative to the shaft 10 along the helical rib 20 until it abuts the stop member 18 which determines the limit of upward movement. On continued rotation of the shaft 10 in a clockwise direction, the disc 22 is rotated therewith in its upper position to effect mixing within the upper regions of the container 2.

When it is required to resume mixing in the lower regions of the container 2, the direction of rotation of the shaft is reversed again to anticlockwise and the disc 22 moves downwardly of the shaft 10 along the rib 20 as indicated by the arrow D in Fig. 4 until it abuts the stop member 16.

Thus it will be appreciated that movement of the mixing disc 22 between upper and lower positions within the container 2, instead of requiring the actuation of complex lifting equipment external of the container 2, merely requires the direction of rotation of the drive motor 12 to be reversed, the configuration of the disc 22 itself and the nature of its mounting on the shaft 10 then ensuring that the required displacement occurs.

The precise construction of the mixing mechanism may vary from that described and illustrated without departing from the scope of the invention claimed.

The co-operating means between the shaft 10 and the disc 22 to ensure relative axial movement therebetween on reverse rotation of the drive to the shaft may be other than helical, for example linear, while the shaft 10 may be positioned other than centrally and vertically within the container 2.

In the case of helical co-operation between the shaft 10 and the disc 22, the rib 20 on the shaft 10 may be discontinuous or intermittent with gaps between adjacent extents of the rib. An intermittent helix provides for improved cleaning efficiency and less likelihood of clogging due to product adhesion on the rib 20.

In an alternative helical arrangement, the shaft 10 may have a helical groove formed therein to extend between the lower and

upper stop members

16,18, with a corresponding helical projection being formed on the inner surface of the hub 24 to be received in said groove. Other modifications and variations will be apparent to those skilled in the art.

As well as eliminating the necessity for raising and lowering the complete mixing mechanism relative to the container 2, the apparatus of the invention considerably reduces the overall head height of the assembly, reduces the likelihood of breaking or damaging the seal through which the drive shaft 10 extends thereby reducing potential environmental problems, reduces the overall cost of the equipment, and provides for faster and more efficient mixing than heretofore.

Claims

Mixing apparatus comprising a container (2) and a mixing mechanism (8) mounted within the container (2), the mechanism (8) including a driven shaft (10) and a mixing disc (22) mounted on said shaft (10), characterised in that the mixing disc (22) is mounted on the shaft (10) to be movable axially relative to the shaft (10) and is so arranged that, on initial rotation of the shaft (10) in one direction, the disc (22) moves from a predetermined upper position on the shaft (10) to a predetermined lower position on the shaft (10) where it remains on continued rotation of the shaft (10) in said one direction, and, on initial rotation of the shaft (10) in the opposite direction, the disc (22) moves from said predetermined lower position on the shaft (10) to said predetermined upper position on the shaft (10) where it remains on continued rotation of the shaft (10) in said opposite direction.
Mixing apparatus as claimed in claim 1 in which the disc (22) includes a central hub (24) having a bore (26) through which the driven shaft (10) extends, co-operating helical means (20,28) reacting between the external surface of the shaft (10) and the internal surface of the hub (24) of the disc (22), the radially outer regions of the disc (22) comprising a plurality of circumferentially spaced blades (32) the plane of each of which makes an acute angle with a transverse plane centrally through the disc (22), the blades (32) extending symmetrically to each side of said central plane.
Mixing apparatus as claimed in claim 2 in which the outer surface of the shaft (10) carries a helical projection (20) thereon and the internal surface of the hub (24) has a correspondingly helical groove (28) formed therein to receive said projection (20).
Mixing apparatus as claimed in claim 3 in which the helical projection (20) is discontinuous and comprise a plurality of spaced sub-projections.
Mixing apparatus as claimed in claim 2 in which the outer surface of the shaft (10) has a helical groove formed therein, a correspondingly helical projection being provided on, to extend radially inwardly from, the inner surface of the hub (24) of the disc (22) to be received in said groove.
Mixing apparatus as claimed in any one of claims 1 to 5 in which the shaft (10) carries abutment means (18,16) thereon for engagement by the disc (22) to determine the upper and lower positions of the disc (22) on the shaft (10).