Improved sock having an earthboard and a process for its manufacture

Technical Field

The invention relates to an agricultural device for soil cultivation, particularly for ploughing. More particularly, the invention relates to an improved sock having an earthboard, and to a process for manufacturing same.

Background Art

It is common knowledge that plaughing is one of the most energy-consuming techniques in agriculture. Ploughing is mainly directed towards trenching of the soil whereby stem-rests, roots, natural dung and chemical fertilizers are mixed and worked in into the soil.

In order to reduce soil resistance and friction during ploughing several different solutions have been developed and experiments aiming at resistance and friction reduction are still in progress. Commonly known socks of ploughing devices include three main component parts, in general. Cutting and lifting of soil strips is performed by a plough-share. The cut and lifted soil strip is cracked, mixed and partly turned by the so called earthboard, the front part of which facing the furrow wall may be a separate part removably fastened to the board itself. By a third important component part of the sock the so called spade substantial support and rectilinear track guidance of the plough are provided.

Experiments and research work towards finding improved socks of minimal traction force demand are generally directed to a reduction of friction forces caused by and acting against the earthboard. However, a solution, that would meet all requirements has not become known so far. Known earthboards resulting from the above mentioned experimental activity are all ve y costly to manufacture and friction coefficient could not be reduced significantly.

The Hungarian Patent Specification No. 145 669 discloses a known pϋsughing device that is, in principle, a so called roller-plough. Experiments in practice have revealed that the objects of the invention as set forth in the above specification could only be achieved when soil of good quality characteristics is cultivated.

In the British Patent Specification No. 1183 062, the G-FR Patent Specification No. 1163 588 and in the SU Patent No. 219 305 ploughing devices are disclosed where on one part of the earthboard positively driven cracking rollers or discs are rotatably mounted. The main disadvantage of such socks is that additional energy for driving said rollers is needed.

Socks with perforated earthboard are also known. Such earthboards have sέrip-shaped openings, i.e. perforations whereby increased specific surface pressure between soil and earthboard surface and, as a consequence, better self-cleaning of the earthboard are achieved.

A similar basic idea has led to further known earthboard designs consisting of suitably bent individual bars or rods that are fastened to the plough beam by means of support elements. A common disadvantage of the above described known ploughing devices and socks lies in the fact that none of them provides considerable traction force reduction while manufacturing costs are still very high. This is resulting from the fact that the earthboards are subject to very high bending load and to wear while working. Because of this, the earthboards are generally made with multiple layers whereby complicate and costly manufacturing processes using steel of best quality are needed. Despite of said facts, the service life of such known devices has proved to be very short, being generally within the range of 2 to 3 years only.

The most intensive wear appears at the vertical front edge of the earthboard, said edge facing the furrow wall. Therefore, earthboards are generally provided with a wear-resistant front member releasably attached to the earthboard itself, whereby worn front members may be replaced periodically. The application of such separate front members however, does not effect the traction force demand when compared with earthboards without such member.

Socks with plastic earthboard have also been subject to investigations. Some experiments have been carried out - by mixing polyethylene with urea granulate- in prder to increase the wear-resistance of the plastic material used. However, practical results have revealed that as a consequence of local variations in the wear-resistance the surface of the earthboard soon became rough resulting in increased friction coefficient and traction force demand. Experimental socks with plastic coated, especially with polyethylene coated earthboards have also been investigated. Because of certain plastic material properties said plastic coated earthboards have turned out to be not successful. The same applies for tephlone coated earthboards. Due to the sensitivity of tephlone against damage, small gravels and other hard particles of the soil would hurt tHe earthboard surface causing thereby significant reduction of the service life of such devices.

Disclosure of Invention

An object of the present invention is to provide an improved ploughing device, particularly a sock having a plastic earthboard, whereby considerable reduction of the friction coefficient and of the traction force demand can be achieved. Another object of the present invention is to provide a simple and economical process for the manufacture of the improved sock earthboard of plastic material as will be disclosed herebelow.

The above and certain other objects are achieved by providing an improved sock having an earthboard wherein the invention lies in the fact that at least the eartchboard consists of plastic, preferably of a wear- resistant thermoplastic material.

Preferred embodiments of the sock according to the invention are characterized by a plastic earthboard having a lower part of along a slightly curved line reduced shape. Said curved line should start from the upper portion of a plough-share adjacent and attached to the earthboard itself, and the width of said shape reduction is within the range between 5 to 10 cm, amounting preferably to 8 cm. In further embodiments of the present invention the plastic earthboard is associated with a plastic trench board, said trenchboard being substantially integral with, i.e. forming one and the same component part with the plastic earthboard. Alternatively, the trenchboard may also be releasable fastened- preferably by means of one or more screw joints - to the earthboard itself. The plastic eartdϋboard may further be substantially strengthened by means of reinforcing and/or supporting ribs.

Yet another embodiment of the sock with plastic earthboard according to the present invention is characterized in having at least one nozzle or jet of preferably elongated orifice shape for earth or soil moisturization during ploughing. Said at least one nozzle or jet is arranged in at least one of fitting slots between the earthboard and the plough-share attached thereto and/or between the earthboard and a wear-resistant front member of the latter.

It has proved to be advantageous in practice, when the plastic earthboard is releasable fastened - preferably by means of plastic screw joint(s) again - to the sock.

A very simple and economicalprocess for the manufacture of improved socks according to the present invention is characterized by the steps of cutting thermoplastic sheet material to a size matching with the shape of the earthboard to be formed, of heating the cut to size plastic sheet up to a temperature within the range between 80°C and 100°C, preferably to 90°C, by applying heat using hot water or hot air so as to heat the plastic sheet to plasticity; of pressing said heated cut to size sheet of plastic into a forming die, and of cooling down the pressed sheet to ambient temperature. The above process may also be performed and carried out in a slightly modified manner of placing first the cut to size plastic sheet onto a forming die having the shape of an earthboard to be manufactured, of heating said forming die up to a temperature within the range between 80°C and 100°C, preferably to 90°C, i.e. up to the range of plasticity of said plastic sheet; of pressing said sheet into said heated forming die so as to form the earthboard of desired shape, and of cooling down the whole forming assembly to normal, ambient temperature.

Brief Description of Drawings

The invention will be more particularly shown and described with reference to the attached drawing. In the drawing show

Fig. 1 an elevational front view of a preferred embodiment of a sock having an earthboard according to the invention as an example only, and Fig. 2 an elevational front view of another preferred embodiment of a sock with an earthboard as invented by way of another example only.

Modes of Carrying out the Invention

In the following description of preferred embodiments of the invention reference is made to the attached drawings. An earthboard 1 of a sock has been manufactured, in accordance with the invention and by way of example only, of a wear-resistant thermoplastic material, preferably of the brand name W0RBLEX PE 7473, in a manner of having cut a suitable plastic sheet to a size and a shape conforming with those of the earthboard to be manufactured. Following this, the cut to to size plastic sheet has been heated to plasticity temperature within the range between 80°C and 100°C, preferably to 90°C by means of hot water or hot air. Thereupon, the heated sheet is placed into a suitable shaped forming die and pressure is applied. Finally, the formed sheet is cooled down to normal, ambient temperature, whereby cooling is performed during a period of 10 to 15 minutes.

The above process may also be performed in a slightly modified manner by placing first the cut to size plastic sheet onto a heatable forming die having the shape of the earthboard 1 to be manufactured, by heating said forming die up to a temperature within the range between 80°C and 100°C, preferably up to 90°C which is the range of plasticity of the plastic sheet material used; by pressing said sheet into the heated forming die so as to form the earthboard 1 to have the shape desired, and by cooling down either the whole assembly or the ready-made earthboard 1 only to normal, ambient temperature.

The earthboard as manufactured above is fixed then to a support surface of the sock and further to a supporting rod of the share-beam in a well-known manner (not shown) . The earthboard is secured to the component parts as listed above preferably by a releasable fastening, especially by means of plastic screw joints 2.

Surprisingly enough, the earthboard 1 according to the invention, shaped and manufactured as described above, has revealed a substantially lower friction coefficient when compared with that of known earlier earthboards consisting of steel. A further advantage is provided by the fact that such plastic earthboards show a very good self-cleaning effect since the plastic material seems to be substantially water-repellent. Experimental ploughing tests have shown additionally that the soil-straps or soil-slices cut out and lifted during piughing are better gliding over the plastic earthboard surface. Hence, at equal piugh speed, the soil slices move along a different, steeper course when compared with, known earthboards of steel. As a result, the lower part of the earthboard facing the bottom of the furrow, does not participate in soil turning said part having the shape of a strip of the width between 5 to 10 cm. Therefore, as shown in Fig. 2, in preferred embodiments of the sock having a plastic earthboard 1 according to the invention the lower part of the earthboard 1 may have an along a slightly curved line reduced shape, and said shape reduction should have a width being within the range, between 5 and 10 cm, said width amounting preferably to around 8 cm. Such shape reduction results in further decrease of the iraction force demand since there is more space in the furrow accomodating the reduced, slimmer earthboard and thus, eliminating friction. Additionally, considerable saving of plastic material occurs.

As mentioned earlier, the earthboard may be further equipped with a trenchboard 3 as an important component part thereof. Fig. 2 shows a sock with an earthboard 1 as an example only whetrin a trenchboard 3 forming an integral unit simultaneously manufactured together with the earthboard 1 by the application of the process as described above is provided for. However, the trenchboard 3 nay also form a separate component part of the sock in question, and in such case, the earthboard should be substantially strengthened by means of reinforcing and supporting ribs securing the earthboard 1 to the sock itself or to support bars in a well known manner. Between earthboard 1 and the sock or the support bars releasable joints, preferably screw joints are applied. Results of ploughing testa have also shown that the friction coefficient of the earthboard depends - at least when plastic material of the type VORBLEX PE 7473 is used - on the moisture content of the soil too. The greater the moisture content of the soil is, the less or smaller is the friction coefficient.

Bearing the above fact in mind, it has turned out to be advisable, especially under dry earth conditions, to provide for a suitable moisturization of the soil slices gliding over the earthboard surface. When doing so, friction coefficient of the earthboard can further be reduced, resulting in additional decrease of the traction force demand and of fuel consumption. It should be stated that moisturization of known traditional earchboards of steel without any additives or agents is not applicable since it would lead to an increased sticking of soil to such earthboards.

Between steel earthboards and plough-shares of known socks there is a fitting gap of the width between 0,1 to 0,5 mm necessary for mounting and assembling said component parts. This fitting gap(s) will have to be maintained with socks having a plastic earthboard 1 too. Within at least one of such fitting gaps along the plough-share at least one nozzle or jet 4 having an elongated orifice of the width of preferably 0,2 mm may be arranged through which over the back surface of the earthboard water may be pumped by applying a head pressure of in the range of 7 to 30 N/cm², depending on the type and on the moisture content of the soil to be cultivated. By such water is the soil moisturized in an area adjacent to the lowest part of the plastic earthboard 1 and of the steel front member 6 during ploughing, moisturizing simultaneously the surface of the earthboard 1 and that of the front member 6 too. By applying moisturization not only saving of traction force demand and of fuel-consumption is achieved but the service life of the earthboard is considerably increased. This is due to the fact that the moisturizing water is directed to an area of the earthboard 1 which wears very rapidly when no moisture is applied. Using moisturization friction forces are reduced whereby less wear occurs.

Head pressure for moisturization may be generated by means of a pump, preferably by means of a peristaltic pump using rollers made of tephlone and by using a pressure gauge valve. A water reservoire in form of a tank or container may be placed onto the hydraulic suspension of the tractor used for plughing. As a further advantage, liquid fertilizers, extirpators, desinfectants may also be applied simultaneously to the soil, if needed.

A yet further advantage of socks having an earthboard according to the invention lies in that the earthboards of that kind are to be manufactured at low production cost level and with, a high productivity in large series. Such plastic earthboards are applicable to all types of socks known so far.

A brief summary of the advantages that are closely linked with or even generated by the invention reads as follows:

- When using an improved sock with plastic earthboard of the kind invented for ploughing, considerable saving both in traction force demand and in fuel consumption occurs since friction coefficient is re markably reduced.

- An improved soil cultivation, especially piughing can be achieved since soil sticking to the earth board surface is - due to certain favourable plastic properties - negligible.

- Besides improved soil cultivation quality an increase in ploughing speed is applicable whilst turning, trenching and mixing the soil are still in the proximity of optimum values.

- Finally, socks with plastic earthboards according to the present invention need no significant care and maintenance, and their storage over periods between subsequent plughing seasons does not require special attention.