Mixing apparatus

Abstract

 The drum of a rotatable mixer comprises at least two sections 11 and 41 of which one section 11 has a closed end wall 12 and a cylindrical wall 13 and internal ribs 21 extend continuously on the inside of the cylindrical wall and the plane end wall. This contrasts with many prior art drums which have internal ribs on one wall only and the end section (41) of such drums are usually frusto-conical.

Description

[0001] In mixing apparatus which comprises a drum which is rotated about its axis in order to mix the materials inside the drum, such as a cement mixer, it has been proposed to form the drum as two frusta of cones joined at their widest portions. Usually such a drum has a closed end at one end of the axis and an open end at the other for loading and unloading of the materials. The open end normally has an aperture which is smaller than the maximum diameter of the drum.

[0002] According to the present invention there is provided a mixing device comprising a drum rotatable about an axis, the drum being formed generally cylindrical in shape, the drum having an open en and a closed end, the drum at the closed end being cylindrical and being provided with mixing ribs on its internal surface, the mixing ribs extending continuously between she curved side wall of the drum and the plane end wall of the drum. The ribs at their ends remote from the plane end wall may have an end wall which is not radial of the the drum.

[0003] The drum may comprise further ribs onits internal cylindrical surface, the end faces of which ribs are preferably not radial. The drum preferably comprises an axial portion free of ribs at which portion the drum can be supported externally.

[0004] At its open end the drum preferably tapers inwardly towards the open end. A detachable cover may be provided for the open end.

[0005] An example of the invention will now be described with reference to the accompanying drawings in which:

FIGURE 1 is a side elevation of a drum, and

FIGURE 2 is a side elevation of a cap for use with the drum of Figure 1.

[0006] The mixing drum illustrated in the drawings is generally cylindrical, with a closed end section 11, having a circular plane end wall 12 and a cylindrical side wall 13. The drum is formed with internal mixing ribs 21 whose depth increases from zero at the ends 15 remote from the wall 12 to a maximum valve (in this case 4. 5cm) and then continued at that maximum value until the junction with the end wall at which the rib continues in a radial direction (at a depth of 2.5cm) across the end wall 12 to taper to nothing at their ends closest to the axis of the drum. The first mentioned end face 15 of the rib 21 is inclined at about 10° to the radius of the drum. The drum is formed by blow moulding, the ribs 21 being formed as part of the side wall 13 of the drum, with open mouths on its exterior. Longer drums can be formed by using a mould with one or more intermediate sections which are added for lengthening the drum.

[0007] The external face of the drum is also formed with a V-groove 24 to receiving a drive pulley belt (not shown) for rotating the drum. The groove 24 is located closer to the closed end of the section than to the open end.

[0008] There are a further series of mixing ribs 33 aligned with the ribs 21 at the closed end, the end faces of the ribs 33 being non-radial. At the end facing the closed end of the drum, the walls 34 of each rib 33 are inclined at about 10° to the radius of the drum. Between the series of ribs 21 and 33, the drum has a plain cylindrical portion 35 (free of mouths 16 present in the ribbed areas) for engagement by a supporting bearing such as a roller (not shown).

[0009] The drum tapers inwardly to a final plain cylindrical portion 45 at an open end 42 having a radius of approximately half the bore of the main cylinder. The plain cylindrical portion 45 would be used to engage supporting pulleys as an alternative to the portion 35 described above. The open end 42 may be provided with a cover 46 for closing the open end which can be fixed in position by a twist-and-lock mechanism. The frusto-conical section 41 has no internal ribs.

[0010] On the axis of the drum at its closed end 12, the drum is supported for rotation by a shaft. The shaft 61 is of steel mounted on a transverse base plate 62. The base plate and the adjacent part of the shaft are covered in plastics material and the shaft assembly is welded to the plastics material of the drum by spinning the shaft assembly about the axis of the drum while bringing the base plate slowly into contact with plane exterior surface of the drum until the heat generated by the friction of contact causes the members to fuse together. The welding step preferably takes place with the axis of the drum vertical so that the welded components can be left in position without danger of falling apart while they cool down. An alternative method of securing the shaft assembly to the drum is by bolting the base plate to the plane end wall of the drum. Bolts are passed through the end wall of the drum from the inside and the bolt heads secured against rotation by injection moulding plastics material around them after which the base plate of the shaft assembly is secured in position by screwing nuts onto the protruding bolt shafts. The ribs 21 stop short of the radius of the base plate 62 so that the latter fixes on to a plain central portion of the end wall 12 (not distorted by ribs).

[0011] It will be seen that the drum is supported for rotation at the shaft 61 and at the plain exterior portion 35 or 45 which is free of hollow ribs and is driven for rotation by a belt passing around the groove 24 between the shaft 61 and the plain portion 35 or 45. A ball race can support the shaft 61. A set of rollers or pulleys can support the portions 35 and 45.

[0012] The drum can be rotated by hand if desired, in which case handles can be fitted to the periphery of the drum, preferably by welding to the external slots formed by the ribs 21 (and possibly 33).

[0013] Rotation of the drum by a motor can be achieved by driving the belt in the groove 24. Water or other fluids can be introduced through a bore (not shown) in the shaft 61.

[0014] The shaft 61 and rollers bearing on the plain portion 34 provide the support for the drum. Axial movement of the drum can be prevented by a radial shoulder such as a circlip secured to the shaft 61.

Claims

1. A mixing device comprising a drum rotatable about an axis, the drum being formed generally cylindrical in shape, the drum having an open end and a closed end, the drum at the closed end being cylindrical and being provided with mixing ribs on its internal surface, the mixing ribs extending continuously between the curved side wall of the drum and the plane end wall of the drum.

2. A device as claimed in Claim 1 wherein the ribs at their ends remote from the plane end wall have an end wall which 5 not radial of the drum.

3. A device as claimed in Claim 1 or Claim 2 comprising a further series of internal ribs.

4. A device as claimed in Claim 3 wherein the end faces of the further internal ribs are not radial of the drum.

5. A device as claimed in any one of the preceding claims wherein the dum comprises an axial portion free of ribs.

6. A device as claimed in any one of Claims 1 to 5 wherein the drum tapers inwardly towards the open end.

7. A device as claimed in Claim 6 comprising a detachable cover for said open end.

8. A device as claimed in any one of the preceding claims comprising mounting means for mounting said drum for rotation about its axis, the mounting means comprising means to support an axial shaft extending from the closed end portion of the drum and means to support the periphery of the drum at a point spaced from said end.

Drawing