GB2158727A

GB2158727A - Mixing apparatus

Info

Publication number: GB2158727A
Application number: GB08411359A
Authority: GB
Inventors: Gerald Gobert; George Ricketts
Original assignee: CHEM PLANT STAINLESS Ltd
Current assignee: CHEM PLANT STAINLESS Ltd
Priority date: 1984-05-03
Filing date: 1984-05-03
Publication date: 1985-11-20
Also published as: GB8411359D0; GB2158727B

Abstract

The apparatus comprises a cylindrical container (2) having an outwardly dished base (4). A shaft (14) extends vertically through the vessel and is supported at one end by an external bearing (16) located on the underside of the base (4) and at the other end by a motorised driving assembly (8). The shaft carries counter-rotating stirrers (20,22) and agitating members (26,30,32) arranged so that when rotated they effect a generally uniform mixing action throughout the container (2). Further rotating stirring or agitating members (24) are located in the lowermost region of the container to effect an additional local mixing action in that region and so prevent the components being mixed to form a solid mass there. An exit orifice (40) is located in the latter region and a scraper (52) mounted on the stirring member (24) wipes over the orifice to assist the discharge through the orifice. <IMAGE>

Description

SPECIFICATION Mixer vessels The present invention relates to mixer vessels.

Mixer vessels have been proposed comprising a hemispherical kettle or other form of container accommodating an agitator mounted on a shaft. The shaft is coupled to a motor for rotation, and the agitator supports a plurality of scrapers. In operation when the agitator is rotated it mixes the contents of the vessel and the scrapers constantly scrape the contents off the mixer surface of the kettle. The shaft enters the top of the vessel and passes through a PTFE gland located centrally in the bottom of the vessel.

Also located in the vessel are counter-rotating stirrer blades which together with the agitator ensure a generally uniform mixing action throughout the vessel.

A disadvantage of this arrangement is that when only small quantities of the components for a mix are fed into the vessel or during the initial phase of pouring larger quantities of components into the vessel, the components congregate in a central region in the bottom of the vessel and so are not very effectively mixed. Where the components are arranged to form a sticky or viscous mix there is a tendency for the components to form into a "solid" mass which remains in this state without further mixing occuring during the remainder of the mixing period.

According to the invention there is provided a mixer vessel comprising a container defining a generally cylindrical or hemispherical chamber having a dished base, a central shaft extending coaxial with the vessel, an agitator rotatable about the axis of the shaft in one sense and stirrer blades rotatable about the axis of the shaft in the opposite sense, the agitator having a configuration which generally follows the side walls of the container and the base but extends away from the central region of the base to define an inverted well, at least one of said stirrer blades being located within the inverted well whereby to provide a local counter-rotating mixing action in the lowermost region of the chamber.

According to the invention there is further provided a vessel including a lid closing the top of the chamber and a motor coupled to said shaft and supported on said-lid, said motor being arranged to rotate both said agitator and stirrer blade in said opposite senses.

According to the invention there is still further provided a mixer vessel comprising a container defining a cylindrical chamber, rotary stirring or agitating members arranged so that when rotated, they effect a generally uniform stirring action throughout the chamber, and further rotary stirring or agitating members located in the lowermost region of the chamber to effect an additional local mixing action in the region.

A mixer vessel embodying the invention, will now be described, by way of example, with reference to the accompanying diagrammatic drawing in which: Figure lisa section through the mixer vessel; and Figure 2 is a fragmentary perspective view of the lower part of the vessel.

The mixer vessel to be described is intended for use in the catering industry to mix the components of cheese, bacon and flour to produce a mix for pizza fillings and pies. While the vessel is particularly suitable for mixing such viscous or sticky products it can equally be used for mixing other compounds for the food, cosmetic, pharmaceutical or adhesive industries.

The mixer vessel as shown in Figure 1 and where appropriate in Figure 2 comprises a cylindrical container 2 defining a chamber having a dished base 4which may be part-spherical. The container 2 is a composite of a stainless steel jacket encased in a lagging and clad with a stainless steel cladding. A cover 6 closes the top of the container 2 and supports a motorised drive assembly 8 incorporating a electric motor 10. Instead the motor can be supported on a separate bridge. A pivoted hatch or lid 12 in the cover 6 provides access to the chamber defined by the container 2.

The drive assembly 8 carries a downwardly depending shaft 14 which extends coaxially of the container 2 through an opening in the base 4 of the container for support in a bearing 16. The bearing 16 is a glass-filled PTFE bearing which is readily removable externally of the chamber for cleaning and sterilisation after a mixing operation.

A pair of axially-spaced diametrically extending stirrer blades 20 and 22 are rigidly secured to the shaft 14 for rotation therewith when the motor is energised.

An anchor or agitator 26 defining a loop which conforms generally to the walls of the chamber (when viewed in longitudinal section) is supported on said shaft 14 by PTFE bearings 28 (only one being shown). Instead the bearings may be lined with materials other than PTFE. The agitator 26 is coupled to the drive assembly 8 to be driven about the shaft axis in the opposite sense to that in which the shaft 14 is rotated. The agitator 26 supports a pair of inwardly directed blades 30 and 32 which lie between the stirrer blades 20 and 22 mounted on the shaft 14.

A plurality of scraper blades 34 for example of Nylon or PTFE are secured at intervals to the agitator 26. The blades 34 are so arranged that upon one completed rotation of the agitator 26 substantially the whole inner surface of the chamber (excluding the cover) is scraped by the blades 34.

An exit orifice 40 is provided in a central region of the base 4 at a location offset from the axis of the container. A discharge tube 42 leads from the orifice 40 to a suitable discharge point. The tube 42 houses a bufferfly valve 44 which is controlled by an operating handle 46. Instead of a bufferfly valve a stem valve or ball valve can be used.

The anchor or agitator 26 in the central region of the base 24 is directed away from the base 4 to form an inverted well 50. A diametrically extending stirrer blade 24 mounted on the shaft 14 is housed within the well 50.

The portion of the agitator 26 forming the well 50 and the stirrer blade 24 together act to provide an additional local, counter-rotating stirring action.

The stirrer blade 24 carries a scraper 52 which when the blade 24 is rotated has a locus such that it passes over the exit orifice 40.

In this manner when the butterfly valve 44 is open, the scraper 52 acts to assist the discharge of the mix from the vessel through the tube 42.

In operation the motor is energised and the anchor 26 and blades 20 to 24 are caused to rotate in opposite senses. The hatch 12 is opened and the components for a mix are poured into the vessel.

The components initially introduced undergo some mixing action as they fall to the bottom base of the chamber. At the base of the chamber the additional mixing action provided by the blade 24 and the inverted well-shaped portion of the anchor 26 ensures a thorough mixing action of the components and prevents the components from forming into a "solid" mass in this region.

Once the components have been thoroughly mixed, the handle 46 is operated to open the butterfly valve 44 and the mix empties out through the tube 42 under the assistance of the scraper 52.

It will be appreciated that the additional mixing action provided by the inverted well-shaped portion of the anchor 26 and the blade 24 can be provided by a portion and a blade of different configuration to that shown in the drawings.

In a modification the blade 24 is rotated at a higher speed than that of the blades 20 and 22.

It will be appreciated that since the bearing 16 is external it is easily removable.

The bearing is preferably jacketed to carry steam so as to heat the bearing to atemperature in excess of 121"C thereby sterilising any trapped material in the interests of hygiene.

For cleaning the chamber a c.i.p. (clean in place) hook-on brush is provided. Such a brush (not shown) is an elongate brush shaped to conform to the side and the lower region of the chamber. The brush is secured to the agitator 26 and trapped between the blades 34 and the wall of the chamber so that when the agitator 26 is rotated the brush will sweep around the chamber to clean the walls thereof.

In a modification provision, is made for an opening (not shown) in the bottom of the chamber to accept a bottom entry homogeniser.

Claims

1. A mixer vessel comprising a container defining a generally cylindrical or hemispherical chamber having a dished base, a central shaft extending coaxial with the vessel, an agitator rotatable about the axis of the shaft in one sense and stirrer blades rotatable about the axis of the shaft in the opposite sense, the agitator having a configuration which generally follows the side walls of the container and the base but extends away from the central region of the base to define an inverted well, at least one of said stirrer blades being located within the inverted well whereby to provide a local counter-rotating mixing action in the lowermost region of the chamber.

2. Avessel according to claim 1 wherein the agitator carries a plurality of scrapers arranged for engagement with the internal surface of the chamber, and wherein said at least one stirrer blade carries at least one scraper arranged for engagement with the floor of the chamber.

3. A vessel according to claim 1 or to claim 2 wherein the said shaft extends through said dished base and is supported by a bearing located externally of the chamber.

4. A vessel according to claim 3 wherein said bearing is a bearing bush which is removable externally of the container cleaning and sterilisation.

5. A vessel according to any preceding claim wherein the container is provided with an exit orifice in the base of the chamber lying within said well but offset from the axis of said shaft.

6. A vessel according to claim 5 as dependent upon claim 2 wherein the at least one scraper on said stirrer blade is mounted to pass over the exit when the stirrer is rotated and thereby assist the passage of any mix in the vessel through said exit orifice.

7. A vessel according to claim 5 orto claim 6 wherein the exit orifice contains a butterfly valve.

8. Avessel according to any preceding claim including a lid closing the top of the chamber and a motor coupled to said shaft and supported on said lid, said motor being arranged to rotate both said agitator and stirrer blades in said opposite senses.

9. A vessel according to any preceding claim wherein said agitator is supported for rotation about said shaft by at least one bush bearing of plastics material.

10. A mixer vessel comprising a container defining a cylindrical chamber, rotary stirring or agitating members arranged so that when rotated they effect a generally uniform stirring action throughout the chamber, and further rotary stirring or agitating members located in the lowermost region of the chamber to effect an additional local mixing action in that region.

11. A vessel according to claim 10 wherein the chamber has a dished or hemispherical base defining said lowermost region and an exit orifice in said lowermost region.

12. A vessel according to claim 10 or to claim 11 wherein said exit orifice is offset from the longitudinal axis of the chamber.

13. A mixing vessel comprising a container defining a generally cylindrical chamber having a dished base, an exit orifice in the dished base located offset from the longitudinal axis of the chamber, stirring or agitating means on the chamber, said stirring or agitating means supporting at least one scraper which scrapes the base and has a locus which passes over said exit orifice.

14. A mixed vessel substantially as hereinbefore described with reference to the accompanying drawings.