METHOD FOR MANUFACTURING CUTTING BLADES FOR A ROTOR TYPE MOWER

Abstract: Method for manufacturing cutting blades (16) for a mower, especially a so-called cyclo mower, whereby departing from a material strip (10) of which the thickness corresponds to the thickness of the cutting blades, and of which the width corresponds to the length of the cutting blades, successive transections are made approximately in transversal direction across a significant part of the width of the strip such that the section of the strip between two successive transections forms a cutting blade, and that suitable tools (18, 19) are used such that simultaneously with the transection operation a shaping operation of the edge(s) (17) of the blank is performed resulting into a cutting blade having ready made cutting edge(s).

Description: 1 Method for manufacturing cutting blades for a rotor type mower The invention relates to a method for manufacturing cutting blades for a mower, especially a so-called cyclo mower, whereby - departing from a material strip of which the thickness corresponds to the thickness of the cutting blades, and of which the width corresponds to the length of the cutting blades, - successive transections are made approximately in transversal direction across a significant part of the width of the strip such that the section of the strip between two successive transections forms a cutting blade. A method of the above-mentioned type is known from US 2521059. The blanks manufactured by this method need some further processing before they can be assembled together with spiders to form a cutter reel for a lawn mower. After the cutting operation a cuutmg edge has to be formed by any suitable means along one edge of the blade. Then the blade has to twisted slightly to obtain its desired final form. Thereafter a number of these blades are combined with spiders into a cutter reel which is detmed to rotate around a horizontal axis wherby in general the blades remain paral¬ lel to said rotational axis. From EP-0310693 a method for manufacturing cutting blades is known, which method is carried out using an elongated material strip. The edges of said strip are preshaped in a rolling operation and if necessary undergo a final processing. After making the necessary holes by means of a punching operation, a shortening operation is performed to separate the cutting blades from the end of the strip. This method comprises a relatively large number of operating processes, each having an influence on the price of the final product. An object of the invention is now to provide a method which uses only a relatively small number of method steps so that a relatively cheap product can be made. A further object of the invention is to extend the effective working life by providing the product with a special shape. In an indirect manner therewith the price/performance ratio is influenced in a favourable way. The above-mentioned objects are fulfilled by a method of the type mdi- cated in the first paragraph which according to the invention is character¬ ized in that suitable tools are used such that simultaneously with the transection operation a shaping operation of the edge(s) of the blank is performed resulting into a cutting blade having ready made cutting edge(s). By means of this method it is possible to start with usually available relatively cheap material of a suitable type, and to avoid finishing ope¬ rations. The invention will be explained in more detail with reference to the attached drawings. Figure 1 illustrates in which way rectangular cutting blades according to the invention are made from a material strip. Figure 2 illustrates a schematical cross section through an embodiment of a tool, which can be used to cut off the cutting blades from the strip material. Figure 3 illustrates a schematical cross section through a preferred embodiment of the tool which can be used to transect the cutting blades from the material strip Figure 4 illustrates schematically how trapezium shaped cutting blades according to the invention can be made out of a material strip. Figure 5 illustrates other shapes of cutting blades which can be made within the scope of the invention Figure 6 illustrates in a perspective view a ready made cutting blade which has an undulated profile in cross section Figure 7 illustrates an embodiment of a method according to the inven¬ tion whereby the transections are not made over the whole width of the material strip. Figure 8 illustrates a cutting blade with twisted central section. Figure 9 illustrates a variant of the method illustrated in figure 7. Figure 1 illustrates schematically in which way rectangular cutting blades can be made from a material strip The material strip, which m figure 1 is referenced by 10 has a width which corresponds to the length of the cutting blades to be made and has a thickness corresponding to the thickness of the cutting blades to be made. The material strip is moved stepwise in the direction 12 and passes thereby in region A a punching machine or another suitable apparatus by means of which the holes 14 are punched in the strip. Dependent on the desired embodiment each ready cutting blade has one or more of these holes 14 functioning for mounting the cutting blade to the rotor of the mowing machine. After leaving region A the strip is further transported to a region B in which an apparatus is installed for separating the cutting blades from the end of the strip by means of a shortening operation. In figure 1 the last cutting blade, produced in this manner, is indicated by 16. The dash and dot lines mark the locations where the successive transections are carried out to make clear in which way the strip is divided into cutting blades. There are various ways to perform the shortening operation in region B. Conceivable is a grinding or sawing operation, but these operations are relatively expensive. A much cheaper operation is cutting off the end sec¬ tion of the strip such that the resulting blade 16a has in any case one bevelled side edge 17 which can be used as cutting edge. Figure 2 illu¬ strates very schematically how such a cutting operation can be performed using a cutting knife 18 and an anvil 19. The cutting knife 18 could even- tually make an inclined downwards movement such that the respective cutting edge 17 is indeed obtained. Preferred, however, is the application of an apparatus in which a com¬ bination of a lower die and an upper die is used for punching the cutting blade from the remainder of the strip. Figure 3 illustrates such an appa- ratus very schematically. The apparatus comprises a lower die 20a and an upper die 20b, both comprising an elongated ridge with an approximately sinusoidal cross sectional shape. The dies 20a and 20b are mounted in the schematically indicated parts 22 and 24 of a press, which press can be operated such that the dies 20b and 20a are moved towards each other. It will be clear from figure 3 that thereby the end section is pinched off from the strip 10 thereby forming the cutting blade 16b of which the elon¬ gated edges, forming the cutting edges, have the shape as is schematically illustrated in figure 3. With this operation not only the cutting blade 16b is separated from the strip but simultaneously the edges of the cutting blade are shaped such that these edges can be used perfectly as cutting edge. To increase the effective life of each cutting blade during the use thereof it is preferable to provide that part of the cutting blade which in fact is subject to the strongest wear during use of the blade, with a larger width so that more material can be worn off before the cutting blade has to be replaced. It is preferred therefore to embody the cutting blades not with a rectangular shape but with a trapezium shape in a way as sche¬ matically is illustrated in figure 4. In correspondence with an adapted method according to the invention the strip 10 is transported in the direc- tion of the arrow first again through a station A where the necessary holes 14a are made in the strip by means of a punching operation. The pattern of holes 14a is in this case different because now the cutting blades will be separated from the strip m a head-tail-pattern. After the operation in region A the strip is transported further to region B where the shortening operation is performed in such a manner that the transecting lines extend not exactly in width direction but in an alternating order make a positive or negative angle with the transversal direction. The result thereof is that in the way illustrated in figure 3 trapezium-shaped cutting blades are separated from the end of the strip. The positions of the succeeding tran¬ sections are indicated by dash and dot lines which make clear how the cut¬ ting blades are formed out of the strip. For performing a shortening operation one could use a cutting knife according to figure 2, however, the press operation illustrated in figure 3 is preferred. The resulting cutting blades 16c have near the holes 14a a relatively small width. This part of the cutting edge is not or hardly subject to any wear. With increasing distance from the hole 14a also the width of the blade increases so that at the side of the cutting blade, where the wear of the blade is the most heaviest, the most material is present. Because there is a lot of material to wear off the effective work¬ ing life of the cutting blade is increased significantly. Instead of trapezium-shaped cutting blades it is within the scope of the invention also possible to make differently shaped blades from an elongated strip. Figure 5 illustrates three examples of differently shaped blades. Figure 5a illustrates a knife 16d whereby the transition between the small section and the broad section is made stepwise. Figure 5b illustrates a knife 16e, whereby the transition between the small section and the broad section is made fluently with a sinusoidal shape. Figure 5c illustrates a knife 16f whereby the transition between the small section and the broad section is made through a sloped intermediate section. In general it counts for all these blades that the succeeding transections, by means of which the knives are separated from the strip and by means of which the cutting edges are shaped, have a mirror-symmetrical pattern in relation to a line transverse to the length direction of the strip. However, taking into account a shortening operation by means of a press for all these blades dies are necessary which are much more complicated and therefore more expensive to manufacture than the simple rectilinear die used for making the trapezium-shaped blades. Therefore the trapezium-shaped blade is preferred. Figure 6 illustrates in a perspective view a knife 16g with a trapezium shape and furthermore provided with an undulation in length direction of the blade. How such an undulation is made is considered to be known and such an undulation is in many cases necessary to be able to correctly mount the blade to the rotor of the mowing machine. Such an undulation can be realized very easily by using a strip material 10 which as such is already provided with this undulation. The operation of manufacturing the blades can be performed further as described in relation to the figures 1 or 4 with the difference that the shortening operation has to be performed with a suitably shaped cutting knife 18 and anvil 19 or suitably shaped dies 20a and 20b. To reduce the therewith corresponding costs it can have its advan¬ tages to amend the method in some way. In this respect the attention is drawn to figure 7. Shown again in figure 7 is the strip 10 which is transported m the direction of the arrow 12 stepwise along the operating stations. It is assumed that trapezium-shaped blades are made from the strip 12 in a simi¬ lar manner as is illustrated in figure 4. For that purpose first of all the strip is transported along a punching machine in region A, where the holes 14b are made in the desired pattern Thereafter in region B the transec¬ tions are made. In contrast with the method as illustrated in figure 4 not the complete shortening operation is performed, but transections are made along almost the complete width of the strip 12 such that at least one not transected location remains. This location is referenced by 22 in figure 7. Instead of one not transected location also two or if necessary more not transected locations can be realized. As a result of these non completed transections the various parts remain connected and can be transported stepwise to a next operation region, indicated by C in figure 7. In this operating region the band is for instance transported through a press by means of which the undulation is pressed in the material. This press can be embodied such that during the pressing operation the last knife 16h is simultaneously separated from the strip However, the press can also be embodied such that the strip after the pressing operation still is integrally intact so that the various blades 16h still have to be separated from the strip. After this operation the blade 16h has the same shape as the blade 16g which is illustrated in figure 6. Instead of knives with an undulated shape also knives with an other non- flat shape can be applied. An example thereof is illustrated in figure 8. The cutting blade 16k which is illustrated in a perspective view has a twisted central section such that the smaller part, wherein the mounting hole is punched and the broader part, will not be in the same plane and will not extend parallel to each other. For such a shape a similar order of operating steps can be applied as described with reference to figure 7, i.e. the holes are punched in region A, the non- complete transections are made in region B, and the shape pressing operation and separating ope¬ rations are carried out in region C. The concept of initially making non complete transections can be brought into practice in other different manners. Figure 9 illustrates how, after punching the necessary holes 14c in region A, in region B transections are made which end at a short distance from the edge of the strip material 10. The transections are in this case embodied such that in fact a small strap of material is removed between the succeeding blades whereby the blades are only connected at their both ends This embodiment of the transections can have advantages during the following operation in region C. In region C the shaping operation is performed to obtain for instance blades of the type illustrated in figure 8 It will be clear that the press, used for this operation, can be embodied such that during the shaping process the blade is also separated from the strip.

Claims: Claims 1. Method for manufacturing cutting blades for a mower, especially a so-called cyclo mower, whereby - departing from a material strip of which the thickness corresponds to the thickness of the cutting blades, and of which the width corresponds to the length of the cutting blades, - successive transections are made approximately in transversal direction across a significant part of the width of the strip such that the section of the strip between two successive transections forms a cutting blade, characterized in that suitable tools are used such that simultaneously with the transection operation a shaping operation of the edge(s) of the blank is performed resulting into a cutting blade having ready made cutting edge(s) . 2. Method according to claim 1, characterized in that the transec¬ tions are made mutually parallel 3. Method according to claim 1, characterized in that m alternat- mg order the transections make a positive or negative angle with the transversal direction of the strip. 4. Method according to one of the preceding claims, characterized in that the transections are made over the full width 5. Method according to claim 4, characterized in that the material strip is profiled in width direction. 6. Method according to one of the claims 1-3, characterized in that the transections are made across a part of the width and that thereafter the material strip by means of a suitable tool is subjected to a shaping operation in width direction after which the cutting blades are separated from this preshaped material strip 7. Method according to claim 6, characterized in that the transec¬ tions are made such that after removing small material sections the blades, disregarding the non transected locations, are loose from each other. 8. Method according to one of the preceding claims, characterized in that preceding the transecting operation holes are punched in the strip such that each of the blades has one or more holes functioning for fixing the blade to the mower. 9. Method according to one of the preceding claims, characterized in that the transections are made by a shortening device. 10. Method according to one of the preceding claims, characterized in that the transections are made by means of a press and dies of which the shape corresponds to the desired shape of the cutting edges of the blades. 11. Method according to claim 10, characterized in that the dies are embodied such that the transitions between both surfaces of the cutting blade and the actual cutting edge obtain a corresponding predetermined desired shape. 12. Method according to claim 11, characterized in that the ultimate shape of the cutting edges is obtained in a number of stages using a number of pressing operations.

Inventors: VAN MAURIK WILHELMUS, VAN MAURIK, WILHELMUS
Applicants: MAURIK WILHELMUS VAN, THIEL UNITED B V VAN, VAN MAURIK, WILHELMUS, VAN THIEL UNITED B.V.
Application year: 1997
Main classification: B21D53
IPC codes: B21D53