GB2126491A

GB2126491A - Mixing machine

Info

Publication number: GB2126491A
Application number: GB08316682A
Authority: GB
Inventors: Paul Hanss; Herbert Kunz
Original assignee: Elba Werk Maschinen GmbH and Co
Current assignee: Elba Werk Maschinen GmbH and Co
Priority date: 1982-07-06
Filing date: 1983-06-20
Publication date: 1984-03-28
Also published as: FR2529822A1; GB2126491B; JPH0368805B2; IT1168880B; JPS5920616A; IT8348377A0; ES8403364A1; FR2529822B1; ES522912A0; GB8316682D0; DE3225207C1

Abstract

A mixer, particularly for concrete, comprises, within a mixing trough (11), a horizontal mixing shaft (14) with two helical strips (25, 26) curving in opposite directions, the strips being formed with a plurality of flat support surfaces (29) for wear resistant plates (28) which are mounted obliquely thereon. The space thus formed between each plate (28) and the helical support (25, 26) may be advantageously used to provide a mounting boss (42) on the underside of each plate (28) to hold the head of a mounting screw (43) (Fig. 3) so that the upper surfaces of the wearing plates (28) form a smooth surface. <IMAGE>

Description

SPECIFICATION Mixing machine, particularly for concrete mixers The present invention relates to a mixing machine, particularly for concrete mixers.

The invention particularly relates to a mixing machine for concrete mixers with a drumshaped mixing trough, in which is horizontally mounted at least one mixing shaft which comprises two helical strips continuous in one piece and curving in opposite directions with a right helicoid orientated perpendicularly to the tangent of the trough and with a corresponding pitch, the helical strips being constructed as helical supports which are divided in such a way into receiving sections for wearing plates arranged side-by-side without gaps that they comprise flat partial surfaces at an angle to one another, and the side of the wearing plates remote from the delivery side being joined to the helical strips in an adjustable and positively locked manner.

A mixing machine of this type is the subject matter of the German Patent No. 23 11 579, which is essentially concerned with the problems of adjusting the wearing plates in a simple manner.

Since the helical strips or the helical supports forming them respectively, and hence the wearing plates, are orientated perpendicularly to the tangent of the mixing trough drum, these wearing plates are subjected to an intensified flow of mixing material and hence increased wear during the upward movement of the mixing blades. Furthermore, fastening holes passing through the wearing plates have also been found to contribute to wear, since channels starting from these holes erode the surface of the individual wearing plates.

The present invention aims to improve a mixing machine of the type described above in such a way as to prevent or reduce wear with respect to the wearing plates and thus to increase their durability and service life.

This is achieved according to the invention in that the wearing plates are arranged obliquely with respect to the helical supports, more particularly with respect to the right helicoid of the helical supports, namely in such a way that the edge towards the mixing trough drum leads.

Accordingly, the present invention provides a mixing machine, comprising a drum-shaped mixing trough, in which is horizontally mounted at least one mixing shaft which has two helical strips curving in opposite directions, the helical strips being constructed as helical supports for wearing plates arranged side-by-side and joined to the helical strips in an adjustable and positively locked manner, wherein the wearing plates are arranged obliquely with respect to the helical supports such that the edge towards the mixing trough drum leads.

The free space gained by virtue of the altered setting angle between the wearing plate and the helical support may be advantageously used for securing the wearing plate in such a way that a fastening element is fitted into a cavity corresponding to the shape thereof and so a simple assembly is made possible without the fastening element having to be inserted through the wearing plate from above.

The invention will be further described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a sectional view of a complete mixing machine; Figure 2 shows a helical support of the mixing machine with wearing plates formed according to the invention; and Figure 3 is a sectional view transverse to the helical support and wearing plate.

A complete concrete mixer is illustrated diagrammatically in Fig. 1. A drum-shaped, horizontally positioned mixing trough 11 extends between two mixing machine columns.

A horizontally positioned mixing shaft 14 is mounted in the two end walls 12 and 1 3 of the mixing trough opposite one another and the respective machine columns. The shaft 1 4 has a plurality of mixing arms 1 5 to 1 8 which extend radially to near the walls of the mixing trough and at the end portions of which are formed two helical strips which are curved at the same pitch in opposite directions and which are formed as helical supports 25 and 26, which, beginning in each case from one of the two end walls 1 2 and 1 3 of the mixing trough, extend diametrically to one another in the longitudinal direction of the mixing trough 11 beyond the centre thereof to a distance from the opposite end wall of the mixing trough in each case, the gap forming a deflection space for the material to be mixed.

The helical supports 25, 26 are secured in each case to mixing arms revolving in the region of the end walls 1 2 and 1 3 of the mixing trough. The helical supports 25, 26 are each further secured over their length to two additional mixing arms 15, 1 6 and 17, 1 8 respectively in the same way. During operation the material to be mixed in the region of the trough wall is moved with a horizontal conveying action according to the counterflow principle alternately from one end wall 1 2 or 1 3 respectively of the mixing trough to the other and is then mixed with the remaining mixing material in the circulating process. The interchange of the material to be mixed takes place rapidly and intensively at any consistency.

The conveying side of the helical supports 25 and 26 comprise a series of immediately adjacent receiving sections 27, to which may be secured wearing plates 28, which consist of a particularly hard metal alloy tempered to a high degree of wear-resistance and which may be arranged side-by-side without gaps.

Flat surfaces 29 at an angle to one another and raised guide strips 30 and elongate holes 31 are arranged inside the receiving sections 27. In the case of the subject matter of the German Patent No. 23 11 579 the rear sides of the wearing plates 28 facing away from the conveying surfaces correspond to the guide and fastening elements 30, 31. In this connection, the wearing plates 28 are set to the correct distance from the mixing trough wall in their clamped state and are secured.

The conveying surfaces of the wearing plates 28 clamped side-by-side in a helical line form a uniformly curved, continuously extending right helicoid which at the end walls 1 2 and 1 3 of the mixing trough further extends along the respective mixing arms as far as the bearing positions of the mixing shaft 14.

This known and generally successful arrangement has now been improved and further deveioped according to the present invention so that the rear sides of the wearing plates 28 now no longer rest flat on the helical supports 25, 26 or the flat surfaces 29 respectively, but are arranged obliquely in such a way that, relative to the direction of rotation of the mixing shaft 14, the edge towards the mixing trough drum leads. In this way the flow of mixing material flowing off over the wearing plates 28 is or will be positively affected with respect to its flow behaviour, as a result of which the service life of the wearing plates is substantially increased.

From the structural point of view such inclination is achieved in that the wearing plates 28 rest with their edges facing the interior of the mixing trough on the helical support 25, 26 and correspond to the guide strips 30 thereof, and supports 40 are provided on the underside of the wearing plates 28, namely in the rear area. In this way the wearing plates 28 are orientated obliquely to the plane defined by the helical support surface.

In a further development of this wearing plate arrangement which is more advantageous in terms of wear, the free space 41 gained by the inclination between the underside of the wearing plates 28 and the upper surface of the helical supports 25, 26 is utilized inasmuch as the releasable connection between the wearing plates 28 and the helical supports 25, 26 is produced by way of a mounting joined to the wearing plates 28 on the one hand and fastening means engaging thereon and extending through the elongate holes 31 into the helical supports 25, 26. In this way, it is possible to dispense with bores which pass completely through the wearing plates 28 together with the edges and corners associated therewith on the surface of the wearing plates 28.

In accordance with the embodiment illus trated in the drawing the mounting is pro duced by providing a frusto-conical attach ment 42 slotted as shown. This frustum is internally hollow, namely in such a way that the head of a screw may be inserted through the opening in the attachment 42. The free end face of the frustum is formed in such a way that it provides a shouldered abutment surface for the screw head. Furthermore, the free end face of the frustum is inclined in such a way that when there is nominal inclina tion of the wearing plates 28, the free end face rests flat upon the corresponding flat partial surface 29 of the helical support 25, 26.

The wearing plates 28 thus rest upon the associated receiving sections 27 by way of their front edge, the supports 40 and the attachment 42. The optimum facility for ad justing the wearing plates 28 is retained, as described in the German Patent No.

23 11 579, by their linear displacement on the flat partial surfaces 29.

A wearing plate 28 shaped according to the invention and screwed onto a helical support 25, 26 is illustrated in section in Fig. 3. The inclination is characterized and defined by the angle a. The supports 40, which are suffici ently wide apart for a screw 43 to be inserted through as a fastening means, are evident from the drawing. The frustoconical attach ment 42, which is open (slotted) on the side of the supports 40, is provided approximately in the centre of the wearing plate 28. The free end face of the attachment 42 is sloped in accordance with the inclination of the wearing plate 28 and rests flat upon the helical sup port. Furthermore, the free end face is formed in such a way that it is constricted in the manner of a collar and provides an abutment shoulder for a screw head.

The screw 43 is inserted between the sup ports 40 into the frustoconical attachment 42 when the wearing plate 28 is loose and finally extends with its threaded portion beyond the free end face of the attachment 42. The head of the screw rests against the inside of the collar-shaped constriction.

The wearing plate 28 is placed with the screw 43 loosely hung therein on the corre sponding part of the helical support 25, 26.

The threaded portion of the screw 43 is guided through the corresponding elongate hole 31 in the helical support 25, 26 and secured from the rear side thereof by means of a nut. The individual wearing plates 28 are now clamped to the corresponding partial surfaces 29 of the receiving sections 27 by way of their supports 40 and the end face of the frustoconical attachment 42. By releasing the screw connection any individual wearing plate 28 may be displaced and fixed once more.

The screw connection between the wearing plates and the helical supports provides a continuously smooth surface without interruptions by screw holes for the surface of the mixing machine exposed to the flow of the material to be mixed. Since the inclination of the wearing plates also acts in such a way as to reduce the wear of the wearing plates, a considerable increase in the service life of the expensive wearing plates may be attained.

Claims

1. A mixing machine, comprising a drumshaped mixing trough, in which is horizontally mounted at least one mixing shaft which has two helical strips curving in opposite directions, the helical strips being constructed as helical supports for wearing plates arranged side-by-side and joined to the helical strips in an adjustable and positively locked manner, wherein the wearing plates are arranged obliquely with respect to the helical supports such that the edge towards the mixing trough drum leads.

2. A mixing machine as claimed in Claim 1, wherein the wearing plates are constructed such that they rest with their inner edges on the helical support and in the region of their outer edges they are provided with supports corresponding to the inclination.

3. A mixing machine as claimed in Claim 1 or 2, wherein the rear side of each wearing plate remote from the delivery side has a mounting for receiving and holding a fastening element for the connection between the wearing plate and the helical support.

4. A mixing machine as claimed in Claim 3, wherein the said mounting comprises a generally frustoconical attachment provided approximately in the centre at the rear of the wearing plate, the frustum being hollow internally corresponding to the fastening element, the end face of the frustum being inclined corresponding to the inclination of the wearing plate, the end face of the frustum being constricted in the manner of a collar towards the axis of the cone, and the frustum being slotted from the open side with respect to the inclination of the wearing plate as far as the end face so as to receive the fastening element.

5. A mixing machine as claimed in Claims 2 and 4, wherein the wearing plates together with the supports and the frustoconical attachments are formed as one-piece castings.

6. A mixing machine, particularly for concrete mixers, comprising a drum-shaped mixing trough, in which is horizontally mounted at least one mixing shaft which has two helical strips continuous in one piece and curving in opposite directions with a right helicoid orientated perpendicularly to the tangent of the trough and with a corresponding pitch, the helical strips being constructed as helical supports which are divided in such a way into receiving sections for wearing plates arranged side by side without gaps that they comprise flat partial surfaces at an angle to one another, and the side of the wearing plates remote from the delivery side being joined to the helical strips in an adjustable and positively locked manner, wherein the wearing plates are arranged obliquely with respect to the right helicoid of the helical supports, such that the edge towards the mixing trough drum leads.

7. A mixing machine according to Claim 1, substantially as herein described with reference to, and as shown in, the accompanying drawings.