GB2235396A - Hammer mill with adjustable sieve casing - Google Patents

Abstract

A hammer mill for grain, fodder and other agricultural products and foodstuffs comprises a rotor (1) with articulatedly suspended beaters, and a sieve casing (2), which extends around the rotor (1) and bounds a milling space (3). The casing consists of two halves, which are pivotably mounted in a vertically adjustable lower sieve mount (5). At their upper ends, the sieve halves have lugs (4) with bolts (6) extending through slots (8) in side walls (9) of the mill. The radial spacing of the sieve relative to the beater circle of the boaters can thus be adjusted. <IMAGE>

Description

1 HAMMER MILL WITH ADJUSTABLE SIEVE CASING -. - I -.:. -- ' L. -.

The present invention relates to a hammer mill.in particular with an adjustable sieve casing, which mill is used for the comminution of materials such as grain, long-fibred and chopped raw fodder, combi-cornmix (CCM) and other products in agriculture and the foodstuffs field.

Known hammer mills consist of a rotor and beaters articulated thereto. The beater circle largely encloses a sieve casing of the mill and thereby forms a milling space. The feeding of the mill takesplace radially from above in the case of a high performance type and partially also axially in the case of a low performance type.

A defined gap is present between the beater circle and sieve casing and results from the difference between the two radii. The size of the gap is varied by wear of the beaters during operation of the mill. Optimum gap dimensions depend on sieve mesh size and the product to be milled. The known machines with constant play are constructed so that the machine operates at an optimum after a short running-in time; however, the quality of the finished product deteriorates and the specific energy consumption increase after wear has occurred, so that a changein direction of rotation of the rotor or a change of beaters may be necessary even after relatively little beater wear. Moreover, adaptation of the working gap to suit the product is not possible.

For that reason, known hammer mills operate with optimum spacing between the beater circle and sieve casing only for a short time span and for a limited range of products.

There is thus a need for a hammer mill, in which the gap between the beater circle of the beaters and the sieve casing can be adjusted over, for example, about 50% of rotor circumference.

According to the present invention there is provided a hammer mill for comminuting materials, comprising a rotor provided with beater elements, and a sieve casing extending around the rotor to bound a milling space, the sieve casing comprising two halves each pivotably mounted at a lower end thereof on vertically adjustable mounting means and connected at an upper end thereof to a respective locating pin adjustable in a guide slot, and the mounting means and the pins being movable to vary the radial spacing of the casing and the locus of the beaters relative to each other in a lower region of the casing.

In such a hammer mill, the sieve casing can be adjusted radially towards the rotor axis. At the same time, the sieve casing halves, on movement of the casing in direction of the rotor, pivot inwardly in direction of the rotor, whereby a rel4tively constant gap to the beater is formed above wall in the lower portion of the sieve casing halves. The two sieve casing halves enclose the rotor and can be moved radially as a whole or each sieve half of its own. When the lower mounting means moves towards the rotor, the sieve halves must also pivot towards the rotor. The sieve halves are preferably retained at their upper end by way of bolts in an elongate hole guide. If the lower mounting means is moved upwardly in direction of the rotor, the upper sieve ends are pivoted towards the rotor in correspondence with the guide. After setting of the gap has taken place, the upper sieve ends are clamped fast in order to avoid vibration.

The construction of the sieve halves can be of various forms. Thick metal sieve plates can be articulated directly, whereas thin metal sieve plates are preferably supported by a frame and sieve guide. In this case, the sieve casing must be moved together with frame and sieve guide. Moreover, the sieve casing can be divided into two or more differently large parts. The movement can take place steplesly in that the lower mounting means sits in a guide and is adjusted by way of a spindle or an eccentric.

A abutment is preferably provided to prevent the sieve casing, in the case of new beaters, being disposed in the path of the beaters.

An embodiment of-the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which:

Fig. 1 Fig. 2 Fig. 3 Fig. 4 is a vertical section of a first hammer mill embodyin 9 the invention; is a cross-section on the line A-A in Fig. 1; is a cross-section on the line B-B in Fig. 1; and is a vertical section of a second hammer mill embodying the invention.

Referring now to the drawings, there is shown inFig. 1 a hammer mill comprising a rotor 1 provided with articulated beaters, the tips or free endsof which define a locus or beater circle on rotation of the rotor. The rotor and beaters are partly encircled by a sieve casing 2, which bounds a milling space 3 for about 75% of the rotor circumference. The sieve casing comprises sieve halves which are mounted to be pivotable on bolts 12 in a lower sieve mount 5. The bolts can be moved axially by way of levers so as to permit rapid sieve casing change (cf. Fig. 2). The sieve halves consist of metal sieve plates which are thicker than 3 millimetres, so that there is no need for a C supporting frame. Lugs 4 with bores are provided at the sieve half lower ends. The bolts 12 of the lower sieve mount 5 are engaged in the bores in the lugs 4, whereby the sieve ca-sing is radially and axially located.

The lefthand sieve half is illustrated in initial setting and the righthand half in a displaced setting.

Lugs 4 with bores are also provided on the upper ends of the sieve halves. A respective bolt 6 with threaded shank projects outwardly from the inside through the bore in each upper lug and through an elongate hole guide or slot 8 in a side wall 9 of the mill. Nuts screwed onto the threaded shanks serve to firmly clamp the upper sieve end (Fig. 3). The lower sieve mount 5 sits in a guide consisting of two guide bolts. Radial adjustment of the lower sieve mount 5 takes place by way of spindle 7, which is actuated by way of a four-cornered member.

For adjustment of the sieve casing, the nuts of the bolts 6 are loosened and the lower sieve mount 5 is pivoted radially in an elongate hole guide through turning of the spindle 7. The sieve halves thus carry out a vertical and a pivotal movement.

It is also possible for the lower sieve mount 5 to be divided so that separate adjustment of the two sieve halves is possible. Moreover the sieve casing 2 can consist of two or more differently sized sieve parts. The movement of the sieve parts takes place radially in the mount.

Fig. 4 shown a sieve casing in which the sieve halves consist of thin metal sieve plate. The halves sit on a sieve frame 10 and are clamped against an inner guide 11. This unit can pivot in its entirety in the sieve mount 5. Adjustment takes place analogously as described 1 for Fig. 1.

By reason of the curvature of the sieve casing, a constant gap width is not settable over the entire circumference. Since the most intensive milling takes place in the region below the rotor axis, the gap is sufficiently uniform there. Thereby, it becomes possible within certain limits to adapt the gap width between beaters and sieve casing to the product and to compensate in part for the beater wear.

Claims (1)

1. A hammer mill for comminuting materials, comprising a rotor provided with beater elements, and a sieve casing extending around the rotor to bound a milling space, the sieve casing comprising two halves each pivotably ted at a lower end thereof on vertically adjustable mounting means and connected at an upper end thereof to a respective locating pin adjustable in a guide slot, and the mounting means and the pins being movable to vary the radial spacing of the casing and the locus of the beaters relative to each other in a lower region of 10 the casing.

2. A mill as claimed in claim 1, wherein the beaters are articulated to the rotor. - 3, A mill as claimed in either claim 1 or claim 2, wherein the pins are mounted in lugs on the casing halves and the guide slots are 15 disposed in side walls of the mill.

4. A mill as claimed in any one of the preceding claims, the mounting means comprising two mounting members which are each associated with a respective one of the sieve casing halves and which are movable independently of each other to permit independent adjustment of the 20 halves.

5. A mill as claimed in any one of the preceding claims, wherein the two halves are unequal in size.

6. A mill substantially as hereinbefore described with reference to the accompanying drawings.

London Wc I R 417. Further copies may be obtained from Eublished 1991 atThe Patent Office, State House, 66171 High Holbo, W- W-t NPI 7M7Printed hvMulUDlextechnJQues ltd. St Mary Cray, Kent.

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