IE893937A1 - Processing of peat for horticultural purposes - Google Patents

Abstract

In a peat processing system, milling apparatus for granulating the peat of a surface layer of a bog includes power-driven milling rollers (5), each of which is provided with a multiplicity of milling members (12). Each milling member (12) is of a generally L-shaped configuration and has a first limb extending outwardly from the peripheral surface of the milling roller and a second limb extending substantially at right-angles to the first limb from the free end of the first limb in a direction substantially parallel to the axis of the roller. The milling members (12) are preferably formed with sharp or pointed ends directed inwardly towards the axis of travel of the milling equipment. Each milling cutter (12) also suitably has a bevelled or oblique cutting edge on the leading side of the cutter in the direction of rotation of the roller. The cutters are suitably laid out on the periphery of the roller drum in a multi-start helical or spiral array. In a further aspect of the invention, the peat processing system includes a power-driven mixing drum of hexagonal cross-section, for mixing granulated peat removed from a bog with other ingredients to provide typically a peat formulation for horticultural use.

Description

This invention relates to the production and processing of peat. In particular, the invention relates to the processing of horticultural peat, i.e. peat for horticultural purposes.

In the production of peat for horticultural purposes, it is 5 important that the degree of granulation is controlled so that the peat is not over-granulated. For horticultural peat, it is necessary to maintain an open or coarse structure in the granulated peat product. Hence, it is necessary to provide for control of granulation size at every stage of the peat production process, including not only the initial production phase, when the peat is first broken up for removal from the bog, but also subsequent processing steps, to ensure that the desired fibrous structure, once achieved at the initial stage, is not damaged during the subsequent processing.

British Patent Specification No. GB 2,148,082A describes an arrangement for milling peat from a bog surface, in which a milling drum is attachable to a towing tractor and rotates substantially transversely to the direction of driving. The surface of the milling drum is provided in one embodiment with a helical milling cutter disposed obliquely with reference to the tangent to the surface of the - 2 IE 893937 milling drum. In an alternative embodiment, said to be appropriate for cutting peat of tough quality, the helical cutter blade is provided with serrations. As shown in Figure 5 of the drawings of this specification, the serrated blade defines a toothed structure extending in the general longitudinal direction of the cutter blade. In a further variant of the serrated blade embodiment, not illustrated, it is stated that the serration may also consist of integral or detachable cutting pieces to be mounted on a standard miller only when conditions require.

British Patent Specification No. 1,601,904 provides an earthworking tool in which a rotatably mounted plate carries a number of radially extending arms. At the free ends of the radial arms, actual working portions then extend laterally, substantially at right-angles to the general radial direction of the arms. Each working portion carries tool elements preferably of hard wear-resistant material, such as cemented tungsten carbide.

It is an object of the present invention to provide improved apparatus for processing peat for horticultural purposes which will enable the establishment and retention of appropriate levels of granulation in the finished product.

According to the invention, there is provided a peat processing system comprising milling means for granulating the peat of a surface layer of a bog, said milling means having at least one power-driven milling roller and said roller being provided with a multiplicity of milling members, each milling member being of a generally L-shaped configuration having a first limb extending outwardly from the peripheral surface of the milling roller and a second limb extending substantially at right-angles to said first limb from the free end of the first limb in a direction substantially parallel to the axis of the roller.

In a favoured configuration, the second limb ends in a point or sharp end. Suitably at least a portion of at least said second limb is tapered in the direction of said point or sharp end. Said point or sharp end is preferably inwardly directed towards a central - 3 IE 893937 axis of said milling means extending substantially in the direction of advance or travel of said roller during use of the milling means. In a favoured construction, said milling member is of unitary construction and has a bevelled side surface providing a cutting edge on the leading region of said milling member during drive of the milling roller(s).

Suitably also, said milling members are located on the periphery of said at least one milling roller in spiral or helical-type arrays of multi-start configuration. The milling roller preferably forms part of a peat milling machine which also comprises carrying rollers, each carrying roller having a plastics cylindrical portion extending between and mounted by metal end plates.

In another aspect, the invention also provides a peat processing system comprising means for mixing granulated peat removed from a bog with other ingredients, said mixing means including a power-driven mixing drum of hexagonal cross-section.

Preferably the mixing drum is rotatably mounted with its axis of rotation sloping downwardly from an infeed or front end of the drum to an outfeed or rear end thereof. The drum may be formed from a plurality of generally rectangular plates, together defining the hexagonal periphery of the drum, and each hexagonal, wall-defining plate portion may be provided with a feed bar for advancing product towards the discharge end of the drum during a mixing operation.

An embodiment of a system incorporating the features of the invention will now be described, having regard to the accompanying drawings, in which Figure 1 is a diagrammatic pictorial view of a milling machine in accordance with the invention, Figure 2 is a diagrammatic pictorial view of two of the milling rollers of the machine of Figure 1, Figure 3 is a detailed view of a single roller showing some of the locations at which the milling members or hooks are welded on, - 4 IE 893937 Figure 4 is a pictorial view of a milling member or hook of the roller of Figure 3, Figure 5 is a side view of an oppositely-handed milling member or hook to that of Figure 4, Figure 6 is a diagrammatic development of the periphery of the milling or hook roller showing the locations where hooks are to be welded on, Figure 7 is a detail of the development of Figure 6, showing the manner of mounting lefthand and righthand hooks respectively, Figure 8 is a representation of a method by which six milling members or teeth suitable for the roller of Figures 1 to 3 are obtained by cutting-off sectoral portions from a metal disc, Figure 9 is a diagram showing the bend line used to convert the sectoral cut-off portions of the disc of Figure 8 into teeth or hooks for welding onto the hook roller, Figure 10 is a sectional view of a carrying roller for the machine of Figure 1, Figure 11 is a diagrammatic pictorial view of a hexagonal section mixing drum in accordance with the invention, Figure 12 is a schematic side view of a mixing installation incorporating a drum in accordance with the invention, Figure 13 is a cross-sectional view of the mixer drum of Figure 11, and Figure 14 is a plan view of one of the plates defining the hexagonal drum, showing a feed bar.

As shown in Figure 1, a peat miller 1 according to the invention has a frame structure, generally indicated by reference 2, - 5 IE 893937 having a forward or pulling end 3 for attachment to a tractor, unpowered carrying rollers 4, by which the machine is supported on the bog, power-driven milling rollers 5, subsequently described in more detail, and adjustable unpowered rollers 6 of large diameter mounted at the rear of the unit for varying the depth of milling action during use of the apparatus. The height of rollers 6 relative to the frame 2 is adjustable for this purpose. The carrying rollers 4 and the milling rollers 5 are mounted to define respective elongate carrying and milling arrays. The assemblies of both the carrying rollers 4 and the milling rollers 5 are each articulated in the axial direction for relative pivoting at least in the vertical direction, so as to accommodate undulations in the surface of the bog. A power take-off (PTO) shaft 7 drives the milling rollers 5 during forward movement of the unit across the bog in the same direction of rotation as the unpowered carrying rollers 4, which are unpowered and rotate by contact with the bog surface, but at a slightly greater rotational speed than the rotational speed which would correspond to the travelling speed of the miller if the milling rollers were also unpowered and rotated only by frictional contact with the bog surface. The drive is transmitted 2o from PTO shaft 7 through a central right-angle drive gearbox 8 and flexible drive linkages between the rollers 5 to cope with the articulated structure.

Referring now to Figures 2 and 3, each milling roller 5 has radially upstanding flange portions or rings 11 by which the roller may pass over obstructions on the bog such as rail tracks, and also over surfaced roadways, without the milling members or projections snagging or suffering damage on the rails or roadway surface, as the case may be. The actual granulating members provided on the milling roller take the form of angled projecting members or hooks 12, also referred to as teeth, the construction of which is shown in more detail in Figures 4 and 5. An exemplary number of these teeth are shown in Figure 2, while a number of the locations on the peripheral surface of the roller 5 at which the hooks 12 are welded onto the roller are indicated by dots 13 in Figure 3. Again only a small number of the total of these locations are indicated in Figure 3, by way of example.

Referring now to Figures 4 and 5, each milling member or hook - 6 IE 893937 consists of a vertically extending limb 21 standing upwardly from the outer peripheral surface 14 of the generally tubular milling roller, and an end limb 22 extending at right-angles to the vertical limb 21 from the free end of the vertical limb and being at least in part of generally tapering configuration to terminate in a sharp end 23. This hook end limb 22 accordingly extends generally parallel to the axis of rotation of the milling roller. The leading surface 23a, relative to the direction of roller rotation, of the tooth or hook 12 over both limb 22 and limb 21 is bevelled rearwardly from its outermost edge 24 as shown in Figure 4 in particular. Thus, the radially outermost tooth surface is of greater area and circumferential dimensions than the inner surface of the hook cutter. This edge 24 of the hook serves as a cutting edge in operation of the miller, to bite into the peat as the roller is driven in rotation. The formation of the bevel or chamfer 23a and point 23 is explained in regard to a subsequent drawing.

Preferably, the hooks or milling members are laid out on the surface of the milling roller in a pattern as shown in part in Figure 3, and in more detail, in the developed views of the periphery of the hook roller of Figures 6 and 7. As shown in diagrammatic form in Figure 6, the developed surface is marked out in an array of notional squares. In a roller of 1150 mm length and 200 mm diameter, the circumference of the outer peripheral surface is 638 mm and is divided into fifteen equal sectors. In the axial direction, each circumferential run of hooks is spaced at a pitch of 40.5 mm in the arrangement shown. The dots 13 designate the corners of each notional square where a hook is welded on in the orientation shown in Figure 7.

Referring now also to Figure 7, a hook member 12 is welded into every sixth notional square along the axial length of the drum in each axial row of squares. The sharp or barbed ends 23 of the hooks or milling members in each case point towards the centre of the machine, that is, its longitudinal axis of travel along which PTO shaft 7 extends. Thus in Figure 7, the points 23 of the hooks 12 to the left of the centre line point to the right, while the sharp ends of the hooks to the right of the centre line are directed towards the left.

Thus left-handed and right-handed hooks are required, and can be formed - 7 IE 893937 by a method to be described. The generally planar rear face of each hook member is also skewed by approximately five degrees relative to a plane transverse to the roller axis and passing through the notional reference point 13 designating the corner of each notional square which receives a hook. A complicated array of welded-on hooks laid out on the periphery of the drum 5 in the manner of a multistart thread is therefore provided by this process, the approximate location of the lower lefthand corner of each hook being indicated in the development of Figure 6 by the dots 13 at the intersection of the notional axial and circumferential grid lines.

Figures 8 and 9 show a method of obtaining six teeth per disc, three righthand teeth and three lefthand teeth, from a single planar metal disc 25, of suitable diameter, typically 170 mm, chamfered at an angle of 30° over its outer peripheral surface region as far as an inner boundary line 25a defining the inner periphery of the chamfered or bevelled portion. This chamfering provides the bevelled surface 23a and outer cutting edge 24 in the formed tooth. Teeth of the required shape are provided by cutting peripheral sectors from this plate as delineated by the cutting lines 26 and 27 indicated in Figure 2q 8. Each sectoral segment is then bent along the fold line 28 line indicated in Figure 9, to provide a hook of the configuration shown in Figures 4 and 5. The bevelled-off region of the sector designated 23a defines the cutting edge 24 where it meets the outer flat surface of the sector and also in part serves to define the sharp end 23 of the fully-formed hook member 12. Typically the hooks stand about 40 millimetres high over the surface of the drum and the hooked end 22 is about 30 millimetres long from vertical portion 21, measured along its outer surface.

Thus the general cross-section of each hook portion is 3q substantially trapezoidal, having major and minor parallel surfaces, a first side surface extending substantially at right-angles between the major and minor surfaces, and a second or bevelled side surface, extending obliquely or at an angle between the major and minor parallel surfaces. The hook member also has a generally tapering section, defined for the most part in the outer or laterally extending end limb 22, in which region the side surfaces of the hook member gradually - 8 893937 converge towards the point or end of the hook, the parallel surfaces of the generally trapezoidal-section hook member remaining however at all times substantially parallel.

As will also be apparent from Figure 8, the cut-out disc portions provide both left-hand and right-hand teeth. Figure 9 shows a portion suitable for a right-hand tooth, limb end section 22 to be bent relative to base section 21 in a direction as it were to extend upwardly from the plane of the drawing in the finally formed condition of the tooth or cutter.

As shown in Figure 1, five milling rollers and five carrying rollers are provided to each side of the central axis of the machine in a favoured construction. However, units of lesser transverse dimension may be provided by the removal of one or more roller sections. The preferred speed for the power take-off shaft is 540 rpm. When driven at this speed, and with a suitable travel speed for the unit as a whole, appropriate granulation is achieved, providing long and fibrous particles of peat for horticultural use. The gearbox ratio is selected to give a drive speed for the rollers of approximately 400 rpm, for the PTO speed of 540 rpm.

This aspect of the invention is directed to the achievement of a suitably coarse level of granulation of peat for horticultural purposes. Overgranulation is not required, since an open structure in the peat is favoured for horticultural use. Very fine granulation, such as is used for milled peat for power station purposes, is not required for horticulture.

The hook miller described in relation to the present invention is used to break up the upper inch or two of peat, which is then harrowed three or four times before being gathered and stacked for collection to be brought to the factory. This granulating operation takes place on a so-called field in the bog, of approximately 50 ft. transverse dimension between drains. The unit of the invention is sized to be approximately 48 to 50 ft. in transverse dimension, to thereby enable milling of an entire field in one operation. Rotation of the power-driven milling rollers, which are to the rear of the - 9 IE 893937 carrying rollers, in the same direction as the direction of travel but at a faster speed that would correspond to the speed of rotation of an unpowered friction-driven roller, ensures that the milled peat is thrown rearwardly from the machine. In order to ensure that the depth of processing is correct, the three pairs of large diameter height adjustment rollers 6 to the rear of the unit are provided, these being capable of upward or downward displacement relative to the frame to vary the depth of cut of the hook or granulating rollers.

In summary therefore, according to the invention, the hooks are preferably arranged as shown in the drawings round the periphery of the milling drums in spiral-type arrays having multistart configurations, to break up the peat into granules of the required size. In each axial row of hooks, hook spacing is approximately 200 mm, and the circumferential spacing of the axial rows around the periphery of the drum is approximately 40 mm. A suitable drum diameter is approximately 200 mm.

In any machine operating on a bog, light weight is of great importance. Thus the present invention also provides a novel construction of carrying roller 4, formed from a plastics pipe portion 31 of large diameter, held between metal end plates 32. These end plates 32 also provide for mounting of the sleeve 31 about a central roller shaft or axle 33, so that the carrying roller construction as a whole may be rotatably supported by shaft or axle 33 being rotatably mounted on or carried by further structural portions of the granulating or milling machine. The end plates 32 are secured to a hub portion of the shaft 33 by means of bolts 34. In this way, a lightweight but highly durable and resilient construction of carrying roller is provided.

In a further aspect, the invention is addressed to the mixing of granulated peat with other ingredients following its collection from the bog. This mixing operation is an essential step in the production of, for example, upwards of three hundred different sizes and qualities of output. Typically, the granulated sphagnum peat retrieved from the upper layers of the bog by milling in accordance with the invention is used, together with a quantity of black peat from the lower layers for - 10 IE 893937 product colouration as required, as the basic ingredient(s) in a horticultural peat product. These varieties of peat are passed through the processing system in metered quantities and one or more of the following additional ingredients are then added, also in metered quantities, depending on the desired composition of the final product; fertiliser, lime, sand, wetting agent. All of these additives are placed onto a conveyor line together with the peat, in proportion to the flow of peat which is metered and weighed at the input stage.

Following this additive operation, the product may undergo a 10 further granule-reducing operation as required, i.e. to further break up the granules and possibly reducee their size, depending on whether a highly granular output or a very fine peat quality are required. For very fine output, a hammer mill and a number of screening operations serve to achieve the required particle size. A number of passes through the hammer mill may be in question. For a more granular or coarser output, only one hammer mill traverse may be required.

The final stage in the operation is end mixing of the ingredients in the novel mixer drum provided by the present invention. As shown in Figures 11 to 14, the mixer drum 41 of the invention has a hexagonal cross-section, as compared with the circular cylindrical shape of conventional mixing drums. Drum 41 is formed from six plates 42a to 42f and is mounted in the mixing installation to slope downwardly from the front, where the material is input from a feed conveyor 46, to its rear or discharge end where the product emerges onto a discharge conveyor 47. Figure 11 is a pictorial view of drum 41 seen from the rear or discharge end, while Figure 13 is an end view of the drum, also from the discharge end of the installation. The plan view of Figure 14 shows the bottommost plate of the drum as seen in Figure 13. The drum 41 is mounted on a support structure 44 for clockwise rotation, as viewed facing the rear end, by means of a drive motor 45. The hexagonal shape of the interior of the drum ensures that the material keeps folding over on itself continually during its advance through the mixer, thereby securing a very effective mixing action. The drum is mounted at a slope from the front to the rear. Feed bars 43 are provided on each hexagonal plate 42a to 42f to ensure advance of the material during drum rotation, if the drum slope is relatively shallow. However, if the inclination of the drum is sufficient, feed bars may not be required. The feed bars 43 are shown in the drawings and in particular in the plan view of the single side plate portion 42a shown in Figure 10. The feed bars extend diagonally cross each face of the hexagon from the right to the left when looking inwards to the drum from the discharge or rear end and are defined by elongate plate portions affixed by their longitudinal edges to the surfaces of the drum plates across a diagonal dimension of the .drum plate to provide upstanding radially inwardly-directed plate portions ]q or flanges of relatively low height. The leftmost end of the feed bar 43, as viewed from the rear or discharge end of the drum, is at the input or front end of the drum, which is at the right-hand end of the plan view of Figure 14, and the rightmost end of the bar is at the rear or discharge end of the drum, in its operating disposition, to achieve the required product advance during rotation of the drum.

The drum may be constructed of mild steel. This may result in some adhering of the peat mixture to the interior of the drum, especially where the mixture is wet. However any such accumulated deposits may readily be removed by a spray means. Alternatively, the 2q drum may be constructed from stainless steel, which ensures no adhering of product to the drum wall under substantially any circumstances.

The drum mixer of the invention is highly effective in providing a homogeneous downstream mixture without any deterioration or reduction in granule size. It is thus ideal for the production of horticultural peat, requiring only a very low energy input as compared with for example paddle mixers, which have a high power requirement and also tend to reduce the grain size excessively. In summary therefore, this drum mixer which is a further feature of the system of the present invention provides excellent mixing while yet retaining the fibrous nature of the product achieved by the milling means forming the first aspect of the invention, so that the precisely granulated peat and the various other ingredients of the horticultural peat products are properly and thoroughly mixed in the final output of the system.

Claims (14)

1. A peat processing system comprising milling means for granulating the peat of a surface layer of a bog, said milling means having at least one power-driven milling roller and said roller being 5 provided with a multiplicity of milling members, each milling member being of a generally L-shaped configuration having a first limb extending outwardly from the peripheral surface of the milling roller and a second limb extending substantially at right-angles to said first limb from the free end of the first limb in a direction substantially 10 parallel to the axis of the roller.

2. A system according to Claim 1, wherein the second limb ends in a point or sharp end.

3. A system according to Claim 2, wherein at least a portion of at least said second limb is of a generally tapering configuration in 15 the direction of said point or sharp end.

4. A system according to Claim 2 or Claim 3, wherein each said point or sharp end is inwardly directed towards a central axis of said milling means extending substantially in the direction of advance or travel of said roller during use of the milling means. 2o

5. A system according to any preceding claim, wherein said milling member is of unitary construction and has a bevelled side surface providing a cutting edge on the leading region of said milling member during drive of the milling roller(s).

6. A system according to any preceding claim, wherein said hook 25 members are arranged on the periphery of said at least one milling roller in a spiral or helical-type array of multi-start configuration.

7. A system according to any preceding claim, wherein the milling roller forms part of a peat milling machine which also comprises carrying rollers, each carrying roller having a plastics cylindrical 3q portion extending between and mounted by metal end plates. - 13 IE 893937

8. A system according to any preceding claim, further comprising means for mixing granulated peat removed from a bog with other ingredients, said mixing means including a power-driven mixing drum of hexagonal cross-section.

9. A peat processing system comprising means for mixing granulated peat removed from a bog with other ingredients, said mixing means including a power-driven mixing drum of hexagonal cross-section.

10. A system according to Claim 6 or Claim 7, wherein the mixing drum is rotatably mounted with its axis of rotation sloping downwardly from an infeed or front end of the drum to an outfeed or rear end thereof.

11. A system according to any of Claims 8 to 10, wherein the drum is formed from a plurality of generally rectangular plates, together defining the hexagonal periphery of the drum, and each hexagonal, wall-defining plate portion is provided with a feed bar for advancing product towards the discharge end of the drum during a mixing operation.

12. A peat processing system substantially as described herein with reference to and as shown in Figures 1 to 9 and Figures 10 to 14 of the accompanying drawings.

13. Peat milling apparatus substantially as described herein with reference and as shown in Figures 1 to 9 of the accompanying drawings.

14. Peat mixing apparatus substantially as described herein with reference to and as shown in Figures 10 to 14 of the accompanying drawings.