GB2217620A

GB2217620A - Rotary mixers for granular materials

Info

Publication number: GB2217620A
Application number: GB8810015A
Authority: GB
Inventors: Richard Jenkins
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-04-27
Filing date: 1988-04-27
Publication date: 1989-11-01
Anticipated expiration: 2008-04-27
Also published as: GB8810015D0; GB2217620B

Abstract

A rotary mixer, such as a cement mixer, has a carrier 12 adapted to receive any one of a number of different sized mixing drums 30. A pair of drive pins 26 fit in a helical groove 28 impressed in the wall 30 of the mixing drum and serve to engage and drive the drum when the carrier is rotated by a motor. The groove 28 forms a rib which projects within the drum. <IMAGE>

Description

IMPROVEIENTS IN ROTARY MIXERS FOR GRANULAR MATERIALS This invention relates to rotary mixers such as are commonly (although not exclusively) used for mixing cement, sand, gravel and like granular or pulverulent materials. In general, such mixers tend to be available in relatively large sizes compared with the requirements of an average domestic user in a D.I.Y.

situation. Furthermore, it is quite common for the user to need to prepare a plurality of blends of granular or pulverulent material during the course of a job, and if only a single mixing machine having only one mixing bowl is available, every change in product specification may involve expensive and time-consuming dismantling, cleaning, and reassembly of equipment.

It is an object of the present invention to extend the range of usefulness of currently available equipment for mixing granular or pulverulent material.

A common form of commercial concrete mixing machine consists of a mixing drum or bowl mounted on an inclined axis about which it is continuously rotated by a conventional power unit until the operator decides that the contents of the drum have been sufficiently agitated for the purpose in view. The drum is then tilted about a transverse axis with its open mouth downwards to discharge the contents.

In this specification, the term "concrete mixer" will be used to describe a machine which produces mixtures of granular or pulverulent material, with or without the addition of a material in liquid form, by a process of tumbling in a rotary drum or bowl until the operator is satisfied with the result.

According to the present invention, a drum carrier or cage is rotatably mounted on an axis inclined to the horizontal and has means for engaging any one of a plurality of drums or bowls for tumbling granular or pulverulent material in a manner such that it is constrained to rotate with the carrier.

Preferably, each drum or bowl is of generally cylindrical shape having a coarse-pitch helical groove impressed on the cylindrical wall so as to form an internal strake or rib for agitating material loaded into the bowl.

Ideally, the carrier is of generally cylindrical form having an inwardly projecting peg or drive pin adapted to fit closely into the coarse-pitch helical groove in the drum.

Conveniently, a sleeve, adaptor or like device may be provided to engage the or each peg or drive pin on the drum carrier and may itself be provided with an impressed coarse-pitch helical groove in its circumferential wall to present an inwardly-facing strake or rib to be engaged by a drum of a reduced external diameter, whereby the mixer can be provided with interchangeable drums of different capacities as may be required in chemical laboratories and the like for mixing varied types and quantities of material.

A practical example of a concrete mixer according to the present invention will now be described, by way of illustration only, with reference to the accompanying drawings in which: Figure 1 is a side elevation of a complete machine; Figures 2 and 3 are side and end elevations respectively, of a carrier; Figures 4 - 6 are similar scrap side elevations showing successive stages in the mounting of an interchangeable drum in the carrier, and Figure 7 is an end elevation of an interchangeable drum.

Referring first to Figure 1, a frame 10 supports a rotatable cylindrical drum carrier 12 located by a bearing 14 with its axis of rotation inclined at an angle to the horizontal. The carrier 12 is driven by a motor 16 through an appropriate transmission 18. The carrier 12 consists of a cylindrical wall spanned at 900 intervals hy spokes 20 radiating from a hub 22 which carries a trunnion 24 adapted to rotate in the bearing 14 on the frame 10. At two diametrically opposite points around the internal periphery of the wall 12 are a pair of inwardly projecting pegs or drive pins 26 each adapted to be a snug fit in a coarse-pitch helical groove 28 impressed in the circumferential wall 30 of a mixing drum.As shown in Figure 6, this impressed coarse-pitch helical groove 28 forms an internal strake or rib 32 which projects into the space within the drum 12 and serves to agitate the contents as the drum rotates. The helical groove 28 breaks through the plane of the base of the drum so that it can be fitted over the peg or drive pin 26 when the drum is offered into the carrier or cage 20. The drum 12 has an integral conical lip 34 which serves to restrict the opening for the charging or discharging of material to be mixed.

In use, a mixing drum 12 is selected and offered up to the carrier 20 (Figure 4) so that it enters the space within the carrier (Figure 5). The drum 30 is then twisted until the open ends of the grooves 28 register with their respective peg or drive pins 26, and it is then pushed home into the carrier 20. The drum 30 is now constrained to rotate with the carrier 20 when the motor 16 is energised, The drum 30 is kept in its place by the inclination of the axis of rotation to the horizontal. Each machine may be accompanied by a plurality of drums 30 all of which may be of the same size for selective insertion into the carrier 20.Alternatively, a special sleeve or adaptor (not shown) may be provided consisting of a cylindrical wall of the same dimensions as the wall 30 of a drum but without the conical lip 34 but having both a pair of helical grooves similar to those shown at 28 in Figure 6 and a pair of inwardly projecting pegs or drive pins similar to those shown at 26 in Figures 2 and 3 for engagement with coarse-pitch helical grooves in drums (not shown) of correspondingly reduced diameter.

It is normally envisaged that a concrete mixer according to the present invention will be smaller than the conventional commercial machines normally available for builders, but it will be understood that overall physical dimensions are optional.

One advantage of a relatively small machine according to the present invention is that the ready detachability of a drum 30 from the carrier or cage 20 enables a low-volume mixture to be transported direct to the site without the necessity of transferring it from the drum to a bucket or the like. Moreover, the material of the drum 30 may be chosen to facilitate separation of the mix therefrom with a minimum of adhesion.

Claims

1. A rotary cement mixer for mixing granular or pulverulent material comprising a relatively rigid frame rotatably supporting a cage or carrier on an axis inclined to the horizontal and means for rotating the cage or carrier, in combination with a plurality of drums or bowls in which material is to be mixed, each drum or bowl being of an external shape and size to be interchangeably mounted with each other drum or bowl on the cage or carrier in a manner whereby any one drum is constrained to rotate with the cage or carrier when mounted thereon.

2. A concrete mixer according to claim 1 wherein the carrier or cage is of generally cylindrical form and has an inwardly projecting peg or drive pin on its circumferential wall, and each drum or bowl has a coarse-pitch helical groove impressed on its circumference to form an internal strake or rib projecting into the drum or bowl to act as an agitator for material loaded thereinto when the latter is rotated by the carrier or cage, the coarse-pitch helical'groove being dimensioned so as to fit snugly over the peg or driving pin on the carrier or cage.

3. A concrete mixer according to claim 1 or 2 wherein a sleeve or adaptor is provided having the same dimensions as the wall of a drum or bowl but without the conical lip surrounding the mouth thereof, and having a duplicate groove formed in its circumferential wall and a peg or drive pin projecting into the interior thereof whereby a drum of reduced diameter can be mounted in the carrier or cage.

4. A concrete mixer substantially as hereinbefore described with reference to the accompanying drawings.