IE831748L - Milling peat. - Google Patents

Abstract

A means for milling peat off a bog surface, said means comprising a milling drum attachable to a towing means known in itself, such as a tractor, and rotating substantially transversally to the direction of driving and of which the surface is provided with one or several milling cutters disposed obliquely with reference to the tangent of the milling drum's surface. With a view to achieving optimum coarseness of the peat that is detached, the invention is mainly characterized in that the cutting direction of the milling cutter or cutters in the plan of the bog surface is substantially the same as the miller's direction of travel. [CA1199649A]

Description

'1'tie present invention concerns a raaana for milling peat from the surface of a bog, said means comprising a milling drum attachable to a towing means known in itself, such as a tractor, and rotating substantially transversally to the direction of driving and of which the surface has been provided with one or several milling cutter(s) positioned obliquely with reference to the tangent on the surface of the milling drum.

The appellation "milling drum" refers to the way in which the blades move, not so much to the frame design of the miller; therefore, the milling drum is understood in peat technology to mean various kinds of rotating milling members.

In the production of milled peat, the first actual work step is the milling, whereat a surface course of the peat field usually 10 to 20 mm in thickness is milled to powder. It would be desirable with a view to drying and later use i !° the grain size of ttio milled pent were comparatively large, on the order of 10 to 20 mm.

Present-day millers fall far short of this objective, owing to inhomogeneity of the peat and to the miller designs among other things.

The so-called spike cutter millers, commonest in the field, usually comminute the peat to less than 'i am grain size. Harrows produce coarser peat, but the dispersion is too wide. Koreover, the surface of the field is made soft and uneven, thus impeding the collection of the milled peat and the movements of machines.

The most advantageous millers today, as far as known, are the Rauss miller and the so-called screw miller according to the Finnish Patent Bo. 58509. The first-mentioned is a harrow-type so-called passive miller of which the frame serves as a float, whereby the surface of the field reaina even. This machine does not operate well on a tough-surface, hard field. The screw miller yields coarser peat than any other active Miller ( "Turveteollisuus" 197i>/3 p. 17-22), but the result Is not as good as could be desired.

On closer scrutiny of the screw Miller one nay observe that In this miller type the load acts on the cutter mainly In the direction of the flat, and therefore the cutter has to be made of comparatively thick material and the cutting takes place in practice with a blunt cutter. The result is a high milling resistance and a grinding effect.

The object of this invention la to improve the durability of a cutter of screw miller type so that the principal load bearing on the cutter acts in the direction of Its plane and not against the cutter flat as is the case in present millers. An attempt is made at the same time to improve the milling quality by using a high peripheral velocity for cutting but a low axial speed for transporting the peat. Such slicing cut produces, when the moisture content Is appropriate, with certain peat types a favourable work pattern resembling a plough cut, with the cuts oriented in the direction determined by the axial and travelling speed vectors.

According to the invention there is provided means for milling peat off the surface of a bog, said means comprising a milling drum attachable to a towing means known in itself, such as a tractor, and rotating substantially transversally to the direction of driving and the surface thereof being provided with one or several helical cutter(s), which ls/are optionally discontinuous, obliquely positioned with reference to the tangent of the surface of the milling drum, the cutting direction of the or each helical cutter in the planu of the bo g surface bein gsubstantially the same as the direction of travel of said Billing drum.

In the means of the present Invention the cutter meets the peat and the hard constituents therein, such as wood constituents, mainly In the direction of the cutter plane, in which direction thus the greatest stresses act on the cutter. This aeans that we are approaching the peat milling mode mentioned above In which the peat is actually transported at a low axial speed, while the cutting Itself takes place In slicing fashion at a high peripheral velocity.

According to an advantageous embodiment of the Invention the pitch angle of the or each helical cutter is less than 10° with reference to the tangent to the sectional circle of the milling drum. In this manner a 4 low axial transporting spaed is simply achieved. The peat material is frequently inhomogeneous, containing e.g. wood substance and tough fibres which would require a high cutting speed, as well as brittler, frequently amorphous matter which should be detached at 5 low speed in order to obtain coarse granules- Low axial speed is obtained even at high speeds of rotation by giving the helix of the or each cutter a low pitch.

According to another advantageous embodiment of the invention the axis of the milling drum is swivellable with reference 10 to the direction of travel of the means for the purpose of achieving an appropriate cutting angle. It is then possible also to use milling drums of which the cutters have a pitch angle even ir excess of 10°. Since on most bogs the quality of the peat layer is greatly variable, the machining characteristics of the miller can 15 in this way be simply adjusted, even from the driver's c.ib of the tractor if need be.

In a further advantageous embodiment of the invention the speed of rotation of the milling drum, and/or.its direction of rotation is controllable. Milling with a helical or screw-20 type cutter produces the coarsest goods when the peat barely be comes detached from the field surface. The setting of milling parameters consistent with this point varies according to peat type. Among the milling parameters to be varied are the 3peed of propagation of the milling drum and the working depth, in addition 25 to the turning of the milling drum's axis already mentioned.

In another advantageous embodiment of the invention the milling drum Is conical. In this way the chipping angle of the or. each cutter in the asdally carried section can be reduced.

In another advantageous enbodlment of the invention 30 a plurality of milling drums are towable after each other, provided with either equal-handel or opposite-handed cutter cutting angles. If two milling units one after the other in the direction of travel are used, one of them should preferably have a left- handcl and the other a right-handed helix.

The screw cutter Bay be serrated and/or provided with cutting elements. The cutting may in this manner he enhanced with a view to cutting through wood and tough fibres.

The flanks of the cutters Bay be covered with a material, such as Teflon for instance, having low friction against peat. This serves to reduce even further the load acting against the cutter's flat owing to the detaching of peat as well as the comminution of the peat.

The pitch of the helical cutter in the case of a single helix miller is at the most fourfold compared with the working depth and eightfold in the case of a two-helix miller. A design of this kind is a prerequisite for o'btaining a work pattern resembling the slice after a plough.

The peripheral velocity of the cutters' cutting notion may be at least five tins the axial velocity. In the case of fibrous anl wood-containing peat a high cutting speed, over 15 m/s, in usually needed for a successful cut, while the detaching speed should he as low as possible, at least below 3 m/s, in order to avoid unnecessary comminution. The detaching speed should be still lower in the case of brittle peat.

The milling principle presented is also advantageous in bog clearing milling and in screwing for profiling and levelling, in which jobs the peat course is manipulated at greater depths than in milling for production: to more than 0.5 m depth oven. The peat material is then wotter and softer than on the surface and therefore t!ie difference from tough fibres such as cotton-grass (Eriophorura), (Scheuchzeria) etc. and from wood materi- 6 al is emphasized. It is therefore benoficial to successful work to be able to do it with high cutting speed and with a sharp cutting blade which is not susceptible to blocking and causes no high cutting pressure and great lateral movement during operation. This 5 is fairly well feasible with the miller of the invention.

The invention is more closely described in the following with the aid of an example with reference being made to the attached drawing, wherein:- Fig. 1 presents a miller according to the invention provided with a 10 single-helix screw cutter, Fig. 2 presents a miller according to the invention provided with separate milling blades, Fig. 3 presents a miller according to the invention with conical milling drum, Fig. 4 presents two millers according to the invention, to be towed one after the other, Fig. 5 presents a miller as in Fig. 1 in which the screw cutter has been provided with serration.

In Figs 1 and 2 is depicted a rotating drual belonging to the 20 milling means and which is attached behind a tractor- substantially transversally to the direction of travel. On the surface of the drum 1 may be fastened a helical cutter blade 2 or helically curved discontinuous blade 3 as shown In Figs 1 and 2. The essential thing independent of the kind of cutter blade used is the pjtch angle; £ 25 , also indicated in Figs 1 and 2. With the aid of the proper pitch angle is achieved the correct proportion of the peripheral velocity and axial speed velocity components V and V . This angle k a must be less than 10°( this being achievable directly by the pitch angle of the cutter< s) or by placing the miller at an angle with 30 reference to the direction of progress so that even a miller having a greater pitch angle will meet the condition specifying not mora than 10° differential angle between cutting and travelling directions in the plane of the field's surface.

One way to reduce the axial peat transporting resistance of the miller is to use a conical milling drum 4, as illustrated in fig. '}. The taper of the drum 4 reduces the chipping angle of the cutter blades in the axial section even though the above-mentioned angle condition is met.

Efficient peat detachment is achieved by an arrangement as shown in Fig. 4, where two different-handed millers 5,6 have been disposed to run one after the other.

Ib Fig. 5 is shown a miller appropriate for cutting tough-quality peat, its cutter blade 7 being provided with serration, k serration like this may also consist of integral or of detachable cutting pieces which one may mount on a standard miller only when conditions require.

The milling means presented here are proper as such for efficient peat milling. Increased flexibility and efficiency are obtained if the millerB are made Such that they can be modified as required during operation, e.g. directly from the tractor's driving cab-Parameters worth while to vgry are e.g. the angular position of the miller axis with reference to the driving direction, the speed and direction of rotation of the milling drum and the working depth of the miller.

It is obvious to a person skilled in the art that different embodiments of the invention are got confined to tha example above presented and that they may vary within the scope of the claims stated below. 8

Claims (12)

CLAIMS:

1. Means for Billing peat off the surface of a bog, said Beans comprising a milling drum attachable to a towing means known in itself, such as a tractor, and rotating substantially transversally 5 to the direction of driving and the surface thereof being provided with one or several helical cutter.(s), which is/are optionally discontinuous, Obliquely positioned with reference to the tangent of the surface of the milling drum, the cutting direction of the or each helical cutter in the plane of the bog surface being substantially the same 10 as the direction of travel of said milling drum.

2. Means according to claim 1, wherein the pitch angle of the o or each helical cutter is lees than 10 with reference to the tangent of the sectional circle of the milling drum.

3. Means according to claim 1 or 2, wherein the axis of the milling 15 drum is turoable with reference to the direction of travel of the means In order to achieve a suitable cutting angle.

4. Means according to claim 1, 2 or 3, wherein the speed of rotation and/or tho direction of rotation of the milling drum is controllable. 20

5. Means according to any one of claims 1-4, wherein the milling drum is conical.

6. Means according to any one of claims 1-5, wherein there Is a plurality of milling drums that can be towed, provided either with equal-handed or different-handed cutting angles of their cutters. 25

7. Means according to any one of claims 1-6, wherein the or each helical cutter is serrated and/or provided with cutting elements.

8. Means according to any one of claims 1-7, wherein flanks of the or each cutter have been covered with a substance having low <r" 9 friction against peat.

9. Means according to clala 8, wherein the substance is a tetra-fluoroethylene or tluorlnated ethylene-propylene resin.

10. Means according to any one of clalas 1-9, wherein the pitch of the screw cutter in the case of a single-helix miller is at the no at fourfold as coapared with the working depth and in the case of one with two helices, eightfold.

11. Means according to any one of claias 1-10, wherein the peripheral velocity (Vfc) of the cutting aoveaent of the or each cutter is at least fivefold compared with the axial speed (Va).

12. Means for Billing peat off the surface of a bog, as clalaed in clain l, substantially as hereinbefore described with reference to or as Illustrated in the acco^ianylng drawings. F. R. KELLY I CO., AGENTS FOR THE APPLICANTS.