Harrowing device

Abstract: A harrowing device for harrowing a ground surface includes a haulable frame (1). A plurality of blade holders (2) are secured to the frame (1), and extend downward from the frame (1). The blade holder (2) has a cavity, a pair of holes (8), a pair of inclined interior face in the cavity. The inclined interior faces are arranged so as to become close to each other the further away from the holes (8). A plurality of blades (3) are fitted to the blade holder (2), each blade (3) having a shank (3a) inserted into the cavity and a blade portion (3b) for harrowing the ground. The shank (3a) has a pair of holes (9) corresponding to the holes (8) of the blade holder (2), and a protrusion for contacting the inclined interior faces. A pin (10) is inserted into the holes (8,9) of the blade holder (2) and the shank (3a) to pivotably support the blade (3).

Description: BACKGROUND OF THE INVENTION Field of the Invention This invention relates to a harrowing device for harrowing topsoil of a race track field for horse racing, agricultural land or the like. Description of the Prior Art Conventionally, harrowing devices have been used for crushing and leveling the topsoil of a race track field for horse racing before starting the race in order to facilitate the racing of horses on the track and to maintain the beauty of the race track. The conventional harrowing devices are generally provided with a frame, a plurality of blade holder, a plurality of blades and a hauling member. In the harrowing devices with this configuration, when the devices are hauled on the field using the hauling member, the blades harrow and crush the topsoil of the field to level the ground. In this harrowing operation, the front edges of the blades are inclined to wear away more than the rear edges of the blades. When the front edge wears away, the efficient of the harrowing operation is reduced. Therefore, to equalize the rate of abrasion of the front edge and the rear edge, when the abrasion advances a little, the blade is reversed so that the front edge and the rear edge are used alternately. In the turning operation, first a plurality of bolt and a plurality of nut which mount the blade to the blade holder are loosened, and then the blades are removed from the blade holders. After that, the blade is reversed so that the front edge becomes the rear edge of the blades, and then the blades are remounted on the blade holders and the bolts and the nuts are tightened. However, because there are many blades, bolts and nuts, this turning operation is very troublesome. Further, in the theoretical case where the cross section of the blade holder has a rhombic shape or a shape of opposing wedges, and the cross section of the shank of the blade for inserting into the blade holder has a rhombic shape or a shape of opposing wedges, the blade cannot be easily removed from the blade holder. Moreover, in the conventional harrowing devices of the type using bolts and nuts, the bolts and the nuts can become loose, so that the blade will frequently fall away from the blade holder during the harrowing operation. In addition, the blade cannot be easily removed because of rusting of the bolts and the nuts. From AU-B-55 01 92, a harrow is known in accordance with the preamble of claim 1 having a frame and a plurality of holders secured to said frame, each of them extending downward from said frame. Each holder receives a cultivating member for harrowing a ground surface. The cultivating member has a flange being in contact with rubber bushes so that the cultivating member is free to move pivotably relative to the holder. SUMMARY OF THE INVENTION It is an object of the present invention to provide a harrowing device which facilitates removal of the blade from the blade holder to simplify the turning operation or exchanging operation of the blade in a short time. Another object of the present invention is to provide a harrowing device which can prevent play developing in the blade, or the blade from falling away from the blade holder during the harrowing operation. These and other objects can be achieved according to the present invention by providing a harrowing device for harrowing a ground surface, comprising: a haulable frame; a plurality of blade holders secured to said frame, extending downward from said frame; each of said blade holders having a cavity extending coaxial to said downwardly extending blade holder; a plurality of blades, each having a shank for inserting into said cavity and a blade portion for harrowing the ground; and a means for pivotably supporting said blade. Said harrowing device being characterized in that each of said blade holders has a pair of holes, a pair of inclined interior faces in said cavity, said faces being inclined in a plane perpendicular to said downwardly extending direction; said inclinded interior faces are arranged so as to become close to each other the further away from the holes; said shank has a hole corresponding to the holes in said blade holder and protrusions for contacting said inclined interior faces; and said means being a pin inserted into said holes of said blade holder and said shank to pivotably pressure-support said blade. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view showing a harrowing device for a race track for horse racing according to the present invention; Fig. 2 is an enlarged fragmentary view showing a supporting structure of the blade of the harrowing device shown in Fig. 1; Fig. 3 is a cross sectional view taken along lines A-A in Fig. 2; Fig. 4 is a cross sectional view corresponding to Fig. 3 of the second embodiment according to the present invention; Fig. 5 is a partial sectional view showing a cap fitted to a tip of a check pin of the third embodiment according to the present invention; and Fig. 6 is a modification of the cap shown in Fig. 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to Fig. 1, a harrowing device is provided with a frame 1 having a plurality of blade holders 2. A plurality of blades (harrowing nail) 3 are fitted into the blade holders 2 respectively. The frame 1 has a plurality of lateral shafts 1a arranged substantially perpendicular to the advancing direction X and a plurality of bars 1b which interconnect the lateral shafts 1b. The bars 1b are arranged substantially parallel to the advancing direction X. The lateral shafts 1a and the bars 1b are preferably made from hollow tube and are interconnected for example by welding. Consequently, the lateral shafts 1a and the bars 1b form the rectangular frame 1. The frame 1 is provided with a pair of dampers 4 on the lateral side of the frame 1, and each damper 4 has a spring 5 for absorbing shock when the frame 1 strikes object such as a fence. The blade holders 2 extend downward from the lateral shafts 1a. The blade holders 2 are preferably made through forging as one body, and secured to the lateral shafts 1a, for example, by welding. The blade holders 2 are arranged so as to prevent the blades 3 from overlapping one another in the advancing direction in order to widely and properly harrow the ground. As shown in Figs. 2 and 3, the blade holder 2 is integrally made of one material such as a steel and the cross section of the blade holder 2 has a rectangular external form. The blade holder 2 is provided with a cavity 7 for permitting the insertion of a shank 3a located at one end of the blade 3. The blade holder 2 has a hole 8, while the blade 3 has a hole 9 corresponding to the hole 8 of the blade holder 2, and a check pin (lock pin) 10 is removably inserted into the holes 8, 9, so that the blade 3 is pivotably supported by the blade holder 2 through the check pin 10. The check pin 10 is prevented from falling out from the blade holder 2 by a split cotter pin or the like. The blade 3 is preferably made of steel through forging and consists of the shank 3a held in the blade holder 2 and a blade portion 3b for harrowing the ground. The blade portion 3b is reversible and is provided with a front edge and a rear edge which exchange positions. The blade holder 2 has a pair of opposing inclined interior faces 12, 13. The blade holder 2 also has a pair of thin wall portions 2a close to the check pin 10 and a pair of thick wall portions 2b away from the check pin 10. The thick wall portions 2b are interconnected through a pair of side walls 2c. The inclined interior faces 12, 13 form a wedge-like pressure holding portion. The shank 3a has a pair of parallel faces 15, 16, which extend in the right-left direction in Fig. 3. On the right end and the left end of the parallel faces 15, 16, an inclined faces 17 and an inclined faces 18 are formed respectively at an angle which is more obtuse than that of the inclined interior faces 12, 13. A pair of crossing portions C of the parallel faces 15, 16 and the inclined faces 17, 18 are provided with a slight gap between the crossing portion C and the inclined interior faces 12, 13. The inclined faces 17, 18 are interconnected through a pair of side faces 20, 20. A predetermined space D is produced between the side face 20 and a interior face of the side wall 2c. In Fig. 1, reference numeral 22 designates a hauling chain as a hauling member. Both ends of the hauling chain 22 are connected to the front lateral shaft 1a of the frame 1. The frame 1 can be hauled through the hauling chain 22 by a tractor, a horse or the like. A wire rope, a connecting shaft or the like may be used instead of the hauling chain 22. Reference numeral 24 designates a smoothing device. The smoothing device 24 may be provided to further smooth the ground surface. The smoothing device 24 is provided with a plurality of nails 25 for smoothing the ground surface, which nails 25 are arranged in the direction perpendicular to the advancing direction. The nails are held by a nail holder 26 extending parallel to the lateral shaft 1a, which nail holder 26 is secured to the rear lateral shaft 1a through a plurality of retainers 27. In the harrowing device with this configuration, when the frame 1 is hauled through a hauling chain 22 by a tractor not shown in the figure in the advancing direction X, first the front blades 3 crush the topsoil and the rear blades 3 level the ground. In the case where the smoothing device 24 is additionally provided, the ground leveled by the blade 3 is further smoothed by the nails 25. In this harrowing operation, the blade 3 slightly pivots on the check pin 10 in the rear direction through a reaction force of the ground, and abuts against the blade holder 2. Then the crossing portions C contact the inclined interior faces 12, 13 and are forced between the inclined interior faces 12, 13. Therefore, The shank 3a of the blade 3 is pressure-held by a reaction force of the thick wall portion 2b of the blade holder 2, so that the blade 3 is firmly fitted to the blade holder 2. In the case where a large pivoting force acts on the blade 3, the side face 20 of the shank 3a contacts the interior face of the side wall 2c to prevent the blade 3 from rotating. At the same time, the thin and thick wall portions 2a, 2b are resiliently deformed and are opened in a slightly outward direction by the pressing force of the crossing portion C. In particular, the thin wall portions 2a move along the check pin 10 in the axial direction, so that the outer faces of the thin wall portions 2a closely contact the head of the check pin 10 and the split cotter pin respectively to firmly fit the check pin 10 to the blade holder 2. Consequently, the blade 3 can be firmly and securely held by the blade holder 2 without using a means such as bolts and nuts. In the case where the front edge and the rear edge of the blade 3 are reversed or the blade 3 is exchanged for a new one, the blade 3 is struck by a wooden hammer or the like to cause it to pivot in the advancing direction X. By this operation, the pressure holding state between the blade holder 2 and the blade 3 is easily cancelled. Namely, the pressure holding state is substantially the point contacting state, so that the cancelling operation is easy in comparison with a planer contacting state of a conventional device. Then, by pulling out the check pin 10, the blade 3 can be very easily dislodged from the blade holder 2. Consequently, the turning operation for the front edge and the rear edge of the blade 3 because of abrasion of the edge becomes easy and simple. Therefore, the edges of the blade 3 wear away evenly to improve the efficiency of the harrowing operation. Fig. 4 shows the second embodiment according to the present invention. In Fig. 4, the same reference numbers as that of in Fig. 3 designates members corresponding to that of in Fig. 3. In this embodiment, a blade holder 2 is constituted by channel members 2A and 2B facing each other and welded together at welding portion E. According to this embodiment, manufacture of the blade holder 2 becomes easy. Fig. 5 shows the third embodiment according to the present invention. In this embodiment, the tip of the check pin 10 is provided with a groove 25 at a peripheral portion thereof. A cap 26 made of elastic material is provided instead of a split cotter pin. The cap 26 includes a cover portion 26a covering the tip of the check pin 10, an engaging portion 26b engaging the groove 25 of the check pin 10 to prevent the check pin 10 from falling away, a leg portion 26c contacting the outer surface of the thin wall portion 2a of the blade holder 2. According to this embodiment, fitting and removal of the cap 26 are more easy than that of the split cotter pin. Fig. 6 shows a modification of the cap 26. The cap 27 shown in Fig. 6 is provided with a engaging portion 27b engaging the groove 25 of the check pin 10, and a leg portion 27c contacting the outer surface of the thin wall portion 2a. The cap 26, 27 may have other modified shapes. In addition, the present invention is not limited to the above described embodiments, and may be applied to a harrow for agricultural land or the like.

Claims: A harrowing device for harrowing a ground surface, comprising: a haulable frame (1); a plurality of blade holders (2) secured to said frame (1), extending downwardly from said frame (1); each of said blade holders (2) having a cavity (7) extending coaxially with said downwardly extending blade holder (2); a plurality of blades (3) each having a shank (3a) for inserting into said cavity (7) and a blade portion (3b) for harrowing the ground; and a means (10) for pivotably supporting said blade (3); characterized in that each of said blade holders (2) has a pair of holes (8), a pair of inclined interior faces (12,13) in said cavity (7) said faces (12,13) being inclined in a plane perpendicular to said downwardly extending direction; said inclined interior faces (12,13) are arranged so as to become close to each other the further away from the holes (8); said shank (3a) has a hole (9) corresponding to the holes (8) in said blade holder (2) and protrusions for contacting said inclined interior faces (12,13); and said means (10) being a pin inserted into said holes (8,9) of said blade holder (2) and said shank (3a) to pivotably pressure-support said blade (3). The harrowing device according to claim 1, wherein said shank (3a) has a pair of faces (15,16) crossing the axis of said pin (10) and a pair of inclined faces (17,18) with a more obtuse angle than that of said inclined interior faces (12,13); crossing portions (C) of said crossing faces (15,16) and said inclined faces (17,18) forming said protrusions. The harrowing device according to claim 1 or 2, wherein said blade holder (2) has a pair of thin wall portions (2a) close to said pin (10), a pair of thick wall portions (2b) away from said pin (10), a pair of side wall portions (2c) interconnecting said thick wall portions (2b), an interior face of said thin and thick wall portions (2a, 2b) forming said inclined interior face (12,13), said inclined faces (17,18) of said blade (3) being interconnected through a side face (20) with a space between said side face (20) and an interior face of said side wall protion (2c). The harrowing device according to one of claims 1 to 3, wherein said frame has a plurality of lateral shafts (1a) and a plurality of bars (1b) interconnecting said lateral shafts (1a). The harrowing device according to one of claims 1 to 4, further comprising a hauling member (22) connected to said frame (1). The harrowing device according to claim 5, wherein said hauling member (22) includes a hauling chain. The harrowing device according to one of claims 1 to 6, further comprising a smoothing device (24) for further smoothing the ground, said smoothing device (24) connected to a rear side of said frame (1). The harrowing device according to claim 7, wherein said smoothing device (24) comprises a plurality of nails (25) for smoothing the ground surface, a nail holder (26) for holding said nails (25), and a retainer (27) for connecting said nail holder (26) to said frame (1). The harrowing device according to one of claims 1 to 8, wherein said pin (10) is provided with a groove (25) at a peripheral portion of a tip thereof; said harrowing device further comprising a cap (26) made of elastic material, said cap including a cover portion (26a) covering a tip of said pin, an engaging portion (26b) engaging said groove of said pin to prevent said pin from falling away, and a leg portion (26c) contacting said blade holder. The harrowing device according to one of claims 1 to 8, wherein said pin (10) is provided with a groove (25) at a peripheral portion of a tip thereof; said harrowing device further comprising a cap (27) made of elastic material, said cap including an engaging portion (27b) engaging said groove of said pin, and a leg portion (27c) contacting said blade holder.

Inventors: GOTO SEIZO C O TAIYO TANKO CO, KUBO SHINJIRO C O TAIYO TANKO, MATSUMOTO SHUNGO C O TAIYO TAN, GOTO, SEIZO, C/O TAIYO TANKO CO.,LTD., KUBO, SHINJIRO, C/O TAIYO TANKO CO.,LTD., MATSUMOTO, SHUNGO, C/O TAIYO TANKO CO.,LTD.
Applicants: TAIYO TANKO KK, TAIYO TANKO CO.,LTD.
Application year: 1991
Main classification: A01B23
IPC codes: A01B33, A01B23, A01B19, A01B35