AU757195B2 - Method of preparing compacted sphagnum moss sheets and a press therefor - Google Patents

Description

Regulation 3.2

AUSTRALIA

PATENTS ACT, 1990 COMPLETE SPECIFICATION o r FOR A STANDARD PATENT

ORIGINAL

cc Name of Applicant: Actual Inventor: Address for service in Australia: Invention Title: THE CHRISTIAN CHURCH COMMUNITY TRUST Perry JUST A J PARK, Level 11, 60 Marcus Clarke Street, Canberra ACT 2601 METHOD OF PREPARING COMPACTED SPHAGNUM MOSS SHEETS AND A PRESS

THEREFOR

The following statement is a full description of this invention, including the best method of performing it known to me/us -2- The present application is a divisional application of Australian Patent Specification 60637/98 concerning a method of preparing compacted sphagnum moss sheets which are free of viable seed and yet able to be readily reconstituted with water. The present invention relates to apparatus used for such compaction. While the present invention has been particularly described in relation to sphagnum moss, it is not restricted thereto and may be applied to other liquid absorbent or reconstitutable vegetable/plant material.

Sphagnum moss is a natural product of certain high rainfall regions of New Zealand and other parts of the world. For economic transportation to markets it is normally dried and packed lightly into bags. When removed from the bags, the moss is in loose form. A feature of this compacted moss is its ability to reabsorb water, to expand, and to return by and large to its original form as wet moss.

Attempts have been made at producing compacted sphagnum moss in sheet form. Such attempts have involved pressing sphagnum moss in a press at pressures up to 1200psi and temperatures between 90'C and 100 C. However, it has been found that temperatures of 1000C and lower are ineffective to eliminate viable seed. Sphagnum moss sheets compacted at 100°C or below have been found to contain viable seed and for this reason have been refused importation rights by quarantine authorities of certain countries in which sales of compacted moss are desirable.

Further trials have been conducted whereby the harvested sphagnum moss has been substantially dried before being compacted. The drying is generally achieved with the use of a batch drying kiln. It has been found that dry moss can withstand heat compaction at high pressures without affecting the ability of the resulting product to reconstitute with the addition of water. It has however been found that with substantially predried moss, viable seeds are still retained in the sphagnum moss sheet and can germinate. The results of such trials are commercially undesirable.

It has now been discovered that the use of a higher moisture content in the moss plays a key role in the production of satisfactory compacted sphagnum moss which is free of viable seed. The reason for this is presently considered twofold. Firstly, any seeds in the damp or partially dried moss will also be damp and hence have a softer outer shell which makes them more vulnerable to penetration and hence to sterilisation. In contrast, it will be appreciated that when harvested moss is dried, the outer coating of any seeds contained therein become hard and resistant to penetration. Secondly, the presence of a significant degree of moisture in the damp or partially dried moss allows for the production steam during heat and compaction. Under confined conditions, the steam can penetrate the already soft outer shell of the seeds and thus sterilise the seeds. Thus, under the right conditions it is possible to create a compacted sphagnum moss which is free of viable seed and yet still able to be reconstituted.

oooo The governments of countries in which the compacted moss would ideally be sold have demanded as a condition of importation into their country that the ministry of agriculture S"of export country endorse a phytosanitary certificate accompanying the exported compact moss with an additional declaration that the moss is clean and free of viable seed and has been produced by a manufacturer approved by that ministry. Shipments of compact moss which contain any viable seed will be refused importation rights into such countries. Thus the importance of producing sphagnum moss which is free of viable seed will be apparent.

The object of the present invention is to provide a press which can be used to sterilise harvested liquid-absorbent vegetable material at a pressure which causes minimal degradation of the plant material, or at least to provide the public with a useful choice.

-4- Described herein and claimed in parent application No. 60637/98 is the invention of a method of preparing harvested liquid-absorbent plant material, wherein the method includes: processing the harvested material in order that the moisture content thereof is sufficient to generate steam when heat and pressure is applied thereto; applying heat and pressure to the material, the pressure on the plant material being at a level so as to minimise the potential for denaturing of the plant material and wherein the temperature/pressure combination is sufficient to generate steam through boiling of the moisture content, the heat and pressure being applied for a time sufficient to sterilise substantially all of any viable seed contained within the plant material.

Suitably, the liquid absorbent plant material comprises sphagnum moss. The sphagnum oo ~moss may be processed in batches to produce sheets of sphagnum moss. The moss layer o• may be of varying thickness, depending upon varying factors including the pressure applied and the time of application. For example, 70 mm of moss could be compressed to a preferred thickness of 2.5 mm in the final product.

The pressure may be applied by opposing platens of a press. The pressure on the moss itself may in fact be as low as 7psi. The preferred range of pressures is from 7psi to S170psi exerted on the moss itself (48kPa to 1171 kPa), although in a more preferred form of the invention, the pressure will be below 43psi. In a most preferred form of the invention, the pressure on the moss is in the range of 7 to 23psi.

The heat applied is preferably in excess of 100C. The heat may be applied to one or both platens of a press. Preferably both platens are heated up to a temperature of 130'C. The preferred range is between 105'C and 130'C.

Preferably, the heat and pressure are applied for a minimum of 3 minutes.

A preferred moisture content of the sphagnum moss prior to the application of heat and pressure is in the range of 18% to 80% by weight.

To achieve a moisture content of between 18% and 80% by weight of the harvested material, it may be necessary to remove some of the water from the freshly harvested material. Water may be removed in a centrifuge. Alternatively, the moss may be put through calender rolls to remove excess water. If necessary, the moss may also be dried in an air drying house or in a kiln. It is most preferred that the moss is uniformly dried.

After the processing of the moss to achieve a satisfactory moisture content, it is preferred that the moss be compacted soon after to ensure that the moss is never fully dried. It is o *o desirable that the desired range of moisture content is achieved in a manner which minimises any of the moss drying to below this range. It has been found that adding moisture to the moss after drying below the limit of 18% moisture to return the moisture content to within the desired range does not produce a satisfactory moss product but one which will not reconstitute. Further, if the moss is permitted to dry below the desired range then, the seeds will be permitted to dry, making the penetration by steam to kill the seeds, more difficult.

The most preferred method of achieving uniform drying to within the desired range without effecting drying below this range is by the use of a continuous drying kiln.

The method may also comprise the further step of venting to allow the steam to be released from the plant material during pressing. Otherwise, the moisture is retained in the material and bubbles or bulges in the material will be created. The venting may be provided such that it allows for even escape of steam throughout the quantity of material undergoing heat and pressure. In a preferred form of the invention, where the sphagnum moss is compacted into sheets in a press, an array of evenly spaced apertures may be -6provided on one or both sides of the press enabling the steam to escape through the press.

The quantity of steam vented from the plant material may be sufficient to amount to a weight loss of the material in the range of 20 to 60 percent.

In accordance with a first aspect of the present invention there is provided a press for compressing liquid absorbent plant material, the press including: a pair of platens for compressing the plant material therebetween, one or both of the platens adapted to be heated, one or both of the platens provided with a plurality of spaced apertures, each of the apertures being in fluid communication with at least one of a o 9o plurality of venting conduits extending in the direction of the plane of the platen to at least one peripheral edge of the platen.

The apertures may be evenly spaced across the platen. As such, the platen may have a perforated arrangement. In a most preferred form, the apertures are arranged in spaced rows, each of the apertures in a row venting into a linearly extending venting conduit. In a preferred embodiment of the invention, the apertures may be arranged in a regular array .i 25 mm apart the size of the apertures being 7/64 of an inch (3 mm). The conduits may be machined through the platens.

In an alternative form of the invention, each platen may be formed of two sheets engaged one atop the other with the conduits being machined into one or both sheets before the two sheets are engaged to define the finished platen. However, in a preferred form of the invention the platens are each comprised of removable metal sheets or plates which may be inserted within the opposing sides of a press. Grooves may be formed in one or both sheets on the side of the sheets which are in contact with the respective side of the press.

Such grooves when in contact with the respective side of the press define the conduits -7through which the steam can escape.

Preferably, the conduits extend in a series of spaced lines. The linear conduits may be evenly spaced and preferably are parallel to each other.

In accordance with a second aspect of the present invention, there is provided a method of pressing liquid absorbent plant material between opposing sides of a press, the method including: providing a quantity of the plant material between two metal plates, at least one of which has on the outer side thereof, a plurality of grooves extending to at least one "peripheral edge of the plate, a plurality of apertures extending through the plate, each of which intersects with at least one of the grooves; inserting the two metal plates between the opposing sides of the press such that the grooves defined in said at least one of the plates will define conduits with the ~respective side of the press; S(c) closing the press to compress the plant material and heating at least one of the metal plates.

In order that the invention may be more fully understood, one embodiment will now be described with reference to the drawings in which: Figure 1 is a schematic exploded view of a press which may be used to compress sphagnum moss according to a preferred embodiment of the present invention; Figure 2 is a perspective view of an alternative metal plate which may be inserted into the -8press shown in Figure 1.

To prepare a compacted sheet of sphagnum moss according to the invention, harvested sphagnum moss is initially processed such that it possesses between 18% and 80% by weight of water. To achieve this damp or partially dried moss, it may be necessary to dewater the harvested moss in a centrifuge. Alternatively, the moss may be put through calender rolls to reduce excess water. As an additional step, the moss may be further dried in an air drying house or kiln although such processing would be for a limited amount of time given the objective of 18% to 80% by weight of water.

The damp or partially dried sphagnum moss is first placed on an aluminum sheet or plate 10 provided on a firm support (not shown). A wooden frame is placed on top of the aluminium plate or sheet 10 to define a rectangular enclosure, the approximate dimensions of which are 2.3m by 1.15m. A weighed quantity of the pre-processed sphagnum moss 12 is spread evenly on the aluminium plate 10. The wooden frame is then removed and a second aluminium plate or sheet 14 is placed on top of the moss 12. The sandwich of :i:hthe two aluminium plates 10, 14 and moss 12 held therebetween is then placed between the sides 16, 20 ofa press.

Both of the sides 16, 20 of the press 8 may be heated between 103-130 0 C while a sufficient pressure is applied to create steam in a confined environment to thereby sterilise the sphagnum moss without significant denaturing of the sphagnum moss 12. A pressure between the range of 7psi and 23psi is applied to the moss 12. A processing time of 3 minutes in the range of the above temperatures and pressures is sufficient to bring about a percentage weight loss of the sphagnum moss of between 20 and 60%. The finished compacted sheet of sphagnum moss which is free of viable seed is then ready for transportation to markets including overseas markets.

-9- Figure 2 illustrates a preferred embodiment of an aluminium sheet 22 which may be used in the press 8 shown in Figure 1 as either the lower plate 10 or the upper plate 14.

The aluminium sheet or plate 22 has a plurality of apertures extending from one side of the sheet to the other. The apertures 24 are arranged in rows extending from one edge of the sheet to the other. The sheet 22 is also provided with a number of grooves in the upper side of the sheet as shown extending from one edge of the sheet to the other. The location of the grooves 26 correspond to the rows of apertures 24.

The sheet 22 is inserted into the press 8 with the grooved side of the sheet facing the respective side of the press 8 i.e. when the sheet 22 is substituted for the upper sheet 14, the grooved side of the sheet will face upwardly towards the upper side of the press If the sheet 22 is substituted for the lower sheet 10, the grooved side of the sheet 22 will face the lower side 16 of the press 8. Of course, two of such sheets 22 may be used on both sides of the press 8. It will be appreciated that when the sheet 22 is placed in the *o press as described above, the grooves 26 will define conduits with the respective side of **the press. When the press is operated under temperature and pressure conditions such that steam is generated in the sphagnum moss 12, the steam can escape through the apertures 24 into the conduits 26 and thereby escape from the press 8 at the lateral edges thereof.

The use of aluminium sheets as described greatly speeds up the production process by substantially reducing the time taken in putting the moss into the press and taking out each compacted sheet after pressing. It also reduces loss of loose moss due to spillage as it is put into the press and damage of the compacted sheet as it is taken out of the press.

Aluminium sheets are light, safe and easy to handle and also allow for rapid transfer of heat from the heated sides of the press to the moss.

10 The foregoing describes only one embodiment of the present invention and modifications obvious to those skilled in the art may be made thereto without departing from the scope of the present invention.

*o*

Claims (9)

1. A press for compressing liquid-absorbent plant material, the press including: a pair of platens for compressing the plant material therebetween, one or both of the platens adapted to be heated, one or both of the platens provided with a plurality of spaced apertures, each of the apertures being in fluid combination with at least one of a plurality of venting conduits extending in the direction of the plane of the platen to at least one peripheral edge of the platen.

2. The press as claimed in claim 1 wherein the apertures are evenly spaced across the platen.

3. The press as claimed in claim 1 or claim 2 wherein the apertures are arranged in spaced rows, each of the apertures in a row venting into a venting conduit aligned with the row.

4. The press as claimed in any one of claims 1 to 3 wherein at least one of the platens is defined by a plate or a sheet inserted between two opposing sides of a press, together S. "with a corresponding side of the press.

The press as claimed in claim 4 wherein the plate or sheet is a removable metal plate or sheet.

6. The press as claimed in claim 4 or claim 5 wherein the venting conduits are defined on the side of the sheet facing the corresponding side of the press.

7. The press as defined in any one of claims 4-6 wherein a pair of removable metal plates or sheets are inserted between the opposing sides of the press. -12-

8. A method of pressing liquid-absorbent plant material between opposing sides of a press, the method including; providing a quantity of the plant material between two metal plates, at least one of which has on the outer side thereof, a plurality of grooves extending to at least one peripheral edge of the plate, a plurality of apertures extending through the at least one plate, each of which intersects with at least one of the grooves; inserting the two metal plates between opposing sides of a press such that the grooves defined in the at least one plate will define conduits with the adjacent side of the press on closing of the press; closing the press to compress the plant material and heating at least one of the metal plates.

9. A press for compressing liquid-absorbent plant material substantially as hereinbefore described with reference to the accompanying figures. Dated thi2' Day o9 2000 By their Patent Attorneys A J PARK SON On behalfof the\Applicant SPer: 2;-