GB2155807A

GB2155807A - Mounting and adjusting beaters of a hammer mill

Info

Publication number: GB2155807A
Application number: GB08505211A
Authority: GB
Inventors: Werner Sauermann; Jurgen Stohr; Eberhard Meissner
Original assignee: Nagema VEB
Current assignee: Nagema VEB
Priority date: 1984-03-06
Filing date: 1985-02-28
Publication date: 1985-10-02
Also published as: GB2155807B; CH665569A5; DD230697A3; GB8505211D0; FR2560790A1; DE3504175A1; NL8500502A; FR2560790B1

Abstract

Each beater 3 has a slot in the form of a straight portion connecting two mounting bores having diameter 10, a rotor shaft (2, Fig. 4 not shown) being located in a selectable one of the bores. The width of the straight portion of the slot is smaller than the diameter of each bore but greater than the radius of the shaft, one side of the straight portion contacting the bores tangentially. The shaft is provided with milled grooves (6), the depth of which is such to give a shaft width equal to the width of the straight portion of the slot so that when the slot is aligned, by rotation of the respective beater, with one of the grooves the beater can be slid across the shaft to relocate the shaft in the other one of the bores. The axial position of the beaters on the shaft is determined by spacer sleeves (4). <IMAGE>

Description

SPECIFICATION Rotor for a hammer mill The present invention relates to a rotor for a hammer mill, for example a mill of the kind used in the fodder industry and agriculture for the production of coarsely granular products.

In known hammer mills operating on the principle of impact comminution, the hammer mill beaters are highly stressed in use. Impact effect and friction lead to high wear in the region of the effective impact edge of the beater and require relatively frequent changing of the beaters depending on the quality of the beater material. The foreign bodies, for example stones or non-ferromagnetic parts, inevitably appearing in the product to be processed oblige a pivotable suspension mounting of the beaters. This functionally advantageous mounting entails particular problems in the dimensioning of the beater shaft for the avoidance of burrs in the region of the mounting.

Due to wear and consequently necessary beater exchange for utilisation of the four straight beating edges in the case of a straight beater or the four arcuate edges in the case of rondes, each with two mounting bores, the known arrangements represent compromises.

In the case of the rotors described in DE-OS 29 35 768 and DE-OS 30 11 427, the time for beater exchange is prolonged through additional heat treatment of the beater edges and the suspension of the beaters takes place on a shaft. These arrangements have the disadvantage that in the case of a worn beater edge and reversal of the rotational direction, re-mounting of the beaters is necessary by removal of the shaft from its fastening.

As a result, the suspension bores of the beaters are freed so that the beaters fall into the housing and are mixed up. Thereafter, the beaters can be individually plugged onto the shaft in reverse sequence by the hitherto unused bore. This procedure represents a considerable amount of work for the operator. When mechanically- locking spacer sleeves or friction-locking spring elements are used for positional fixing of the beaters on the shaft, the work increases and the time for the beater exchange rises and is at the expense of effective production.

It would thus be desirable for the beaters to be mounted on the shaft in such a way that the four beater edges of beaters in the geometric shape of a flat member or the four arcuate sections of beaters in the geometric shape of a ronde can be utilised one after the other as effective impact edges without disassembly of the rotor According to the present invention there is provided a rotor for a hammer mill, the rotor comprising a shaft on which one or more beater members are retained on defined circulatory tracks each time between two rotor disc elements, which retain the shaft radially, by mechanically-locking spacer sleeves or friction-locking spring elements, wherein slots in the beater members have a shape which is asymmetrical with respect to the longitudinal axis of the beater member and milled grooves in the shaft each have the shape of a circular segment and lie at the same height in the case of use of the spacer sleeves or, in the case of use of the spring elements, are arranged as desired outside the block length of the spring elements, the slot and the milled groove in this case lying opposite each other in the plane of rotary thrust and an additional milled groove for the reception of a plate being arranged in the shaft.

By means of the arrangement of the slots in the beater members and grooves in the shaft as well as an additional fixing of the shaft, sharp impact edges of the beater members can be brought into operative position without disassembly of the entire rotor and rotation of the shaft into a particular position.

Preferably, the slot in each recess is defined by two suspension bores for the shaft and a portion connecting the bores, the width of the connecting portion being smaller than the diameter and greater than half the diameter of the shaft and one side of the connecting portion contacting the suspension bores tangentially. In operative position, the groove in the shaft and the slot in the beater member lie at the same height and are disposed one opposite the other when the positional fixing of the beater members takes place through mechanically-locking spacer sleeves. If the position of the beater members is determined by friction- locking spring elements, then the grooves in the shaft can lie outside the block length of the spring elements.In the case of this positional fixing of the beater members, the groove in the shaft bolt and slot in the beater member in the rotary thrust position are in each case at the same height and lie opposite each other.

Embodiments of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which: Figure 1 is a longitudinal sectional view of part of a first hammer mill rotor embodying the invention; Figure 2 is an end view of the rotor of Fig.1; Figure 3 is a view of a beater member of the rotor; Figure 4 is a side view of part of a shaft of the rotor; Figure 5 is an end view of the shaft of Fig. 4; and Figure 6 is a longitudinal sectional view of part of a second hammer mill rotor embodying the invention.

Referring now to the drawings, there is shown part of a rotor for a hammer mill in which a product to be milled, such as cereal, is comminuted to the desired fineness through impact and friction effect by the beaters 3 arranged in sets on the shaft 2 of the rotor in a milling chamber of the mill. For mounting of the beaters 3 on the shaft 2, each beater has a slot 7 in the form of a straight portion connecting two part-circular end portions, the end portions constituting suspension bores which have a diameter 10 corresponding to the diameter of the shaft and a selectable one of which receives the shaft. Depending on the rotational direction of the rotor, only one beating edge of each beater 3 participates in the comminuting operation and is thus subject to the wear.In the operative position of the rotor, the beaters 3 extend radially due to the circumferential speed and the rotor shaft 2 in conjunction with rotor discs 1 takes up the centrifugal and circumferential forces. Spacer sleeves 4 (Fig.1) or spring elements 12 (Fig.6) hold the beaters 3 in a prescribed circumferential track. As shown in Fig.1, in operative position a milled groove 6 of the shaft 2 stands at the height of the beater 3 where the spacer sleeves 4 are used. If spring elements 12 are used, the position of the groove 6 can be outside the block length of the spring element 12.

It is thereby possible to construct the shaft 2 with its grooves 6 arranged uniformly even though the circulatory tracks of the beaters 3 may be displaced from beater row to beater row.

A further milled groove 11 in the shaft 2 serves for the reception of a plate 5 and is arranged with an axial displacement from the grooves 6 by the angle "of 90 in the mathematically positive sense of rotation. The plate 5 engaged in the groove 11 is detachably connected to one of the rotor discs 1.

As a result, the shaft 2 in the operative position is secured against axial displacement so that the grooves 6 remain at the same height as the beaters 3 and in addition the beaters 3 bear on arcuate portions of the shaft circumference as if the grooves 6 were not present. Consequently in operative position, the grooves 6 face away from the centre of the rotor, while the straight portions of slots 7 in the beaters 3 point radially towards the centre of the rotor. This means that the beater 3, on standstill of the rotor and due to the width 8, chosen in relation to the diameter 10 of the shaft 2, of the straight portion of the slot 7 in the beater 3 and the depth 9 of the groove 6, cannot by itself slip into the suspension bore which lies near to the respectively utilised beater edge.The arrangement of the grooves 6 and slots 7 in conjunction with the fixing of the shaft 2 by the plate 5 ensures the smallest areal stressing between the beaters 3 and the shaft 2 as well as the pivotability of the beaters 3 in the case of overload through, for example, contact with foreign bodies.

If a beater edge is worn out, then with unchanged position of the shaft 2 the beater 3 is axially displaced on the shaft 2 into the rotary thrust position, while groove 6 and slot 7 lie at the same height, and then pivoted through 90" relative to its operative position and pushed over the shaft 2 into the hitherto unused suspension bore. When the spring elements 12 are used, these press the beaters 3 into the original position of the circulatory track. On restarting of the rotor in the same rotational direction, the beaters 3 assume their operative position and a sharp beating edge, diagonally opposite the worn-out edge, comes into use.A change in rotational direction in the case of reversible hammer mills or resuspension of the beaters 3 is necessary only after the second beater edge is worn out in order to bring the two remaining sharp edges into the operative position.

Resuspension of the beaters 3 takes place by detaching the plate 5 from the respective disc 1 and removing it from the groove 11, whereafter the shaft 2 is pulled forward until the groove 11 is visible out of the last rotor disc limiting the rotor or the shaft 2 is immediately turned through 90" to the right or left so that the grooves 6 each point radially to the rotor centre. Then the shaft 2 can be drawn out of the rotor assembly in its entire length without great effort, since wedging of the slots 6 at the discs 1 and clamping of the beaters 3 does not occur in this position of the shaft. A prerequisite for withdrawal of the shaft without great effort is a position of the beaters 3 which deviates from the operative position.

Claims

1. A rotor for a hammer mill, the rotor comprising a shaft, a plurality of spaced disc elements arranged on the shaft, a plurality of elongate beater members arranged on the shaft between the disc elements and each provided with a closed longitudinally extending slot through which the shaft so extends as to be located at one end of the slot, and means determining a defined axial position at each beater member on the shaft, each beater member being movable relative to the shaft to so align its slot with a segment-shaped groove in the shaft as to permit longitudinal displacement of the member for relocation of the shaft at the other end of the slot.

2. A rotor as claimed in claim 1, the determining means being spacer sleeves.

3. A rotor as claimed in claim 1, the determining means being springs.

4. A rotor as claimed in any one of the preceding claims, wherein the slot of each beater member is alignable with the groove solely by movement of the member rotationally about the shaft.

5. A rotor as claimed in claim 4, wherein the slot of each beater member is alignable with the groove by movement of the member rotationally about and axially along the shaft.

6. A rotor as claimed in any one of the preceding claims, wherein the shape of the slot in each beater member is asymmetrical with respect to the longitudinal axis of the member.

7. A rotor as claimed in claim 6, wherein the sum of the width of the intermediate portion of the slot and the radial depth of the groove is substantially equal to said diameter.

7. A rotor as claimed in claim 6, wherein the slot in each beater member has two part-circular end portions each of a diameter substantially equal to that of the shaft and a straight portion which connects the end portions together and the width of which is less than said diameter but greater than the radius of the bolt, one side of the straight portion being substantially tangential to the notional circles containing the end portions.

8. A rotor as claimed in claim 7, wherein the sum of the width of the straight portion of the slot and the radial depth of the groove, is substantially equal to said diameter.

9. A rotor as claimed in any one of the preceding claims, comprising a lock plate detachably con nected to one of the disc elements and so engaged in an associated segment-shaped groove in the shaft as to secure said one disc element and the shaft against relative rotation.

10. A rotor as claimed in claim 9, wherein the groove receiving the lock plate is displaced through an angle of substantially 900 relative to the grooves for the beater members.

11. A rotor substantially as hereinbefore described with reference to Figures 1 to 5 of the accompanying drawings.

12. A rotor substantially as hereinbefore described with reference to Fig.6 of the accompanying drawings.

Amendments to the claims have been filed, and have the following effect: (a) Claims 1 & 5 to 8 above have been deleted or textually amended.

(b) New or textually amended claims have been filed as follows: (c) Claims 9 to 12 above have been renumbered as 8 to 11 and their appendancies corrected.

1. A rotor for a hammer mill, the rotor comprising a shaft, a plurality of spaced disc elements arranged on the shaft, a plurality of elongate beater members arranged on the shaft between the disc elements and each provided with a closed longitudinally extending slot through which the shaft so extends as to be located in one end portion of the slot, and means determining a defined axial position of each beater member on the shaft, each beater member being movable relative to the shaft to so align its slot with a segment-shaped groove in the shaft as to permit longitudinal displacement of the member for relocation of the shaft in the other end portion of the slot, and the slot in each beater member having its end portions disposed symmetrically, and its intermediate portion asymmetrically, of the longitudinal axis of that member.

5. A rotor as claimed in claim 4, wherein the slot in each beater member is alignable with the groove by movement of the member rotationally about and axially along the shaft.

6. A rotor as claimed in any one of the preceding claims, wherein each end portion of the slot in each beater member is part-circular and of a diameter substantially equal to that of the shaft, and the intermediate portion of the slot has a width which is less than said diameter but greater than the radius of the bolt, one side of the intermediate portion being substantially tangential to the notional circles containing the end portions.