Abstract:
A spring tooth harrow for land treatment has an improved spring tooth and an improved tooth attachment clip; the tooth has a tine, a helical coil spring, and a mounting lug having an inboard leg, a semi-circular medial leg and a straight outboard leg, the legs are co-planar and have a divergent angle between them; the clip is L-shaped and has a first leg with a rear shoulder and a fastener aperture and a second leg with a taper divergent towards the first leg; the clip second leg goes in between the lug inboard and outboard ends and biases the tooth into proper position, the second leg also absorbs a significant part of the lateral loads upon the tooth, and applies these loads directly to a structure of the harrow.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention pertains to a spring tooth harrow, to a spring tooth for a harrow, and to an attachment clip for securing a spring tooth to a harrow. 
     2. The Prior Art 
     Spring tooth harrows were devised many years ago. The first designs had the helical spring coils mounted around a tubular structural member. This is an excellent and very strong method of devising a harrow and of mounting a helical coil harrow tooth. Unfortunately, if you brake a tooth, you must dis-assemble the entire harrow to replace the tooth. The customers comprising the harrow marketplace found this unacceptable. 
     Therefore, the spring tooth was mounted on the outside of the harrow frame so it could be replaced when broken, and so the harrow frames could be fabricated without teeth, and teeth added by the retailers or farmers. 
     The most commonly used cross-members in harrows are tubes and angle iron sections. The harrow teeth are fastened to these sections. The tube does not lend itself to advantagous securement of a helical coil spring tooth, if the helical coil is not around the tube. The angle iron is easy to fasten to, but it has proven very difficult to effectively fasten and mount a spring tooth to and retain strength and avoid breakage. 
     The problem is that the tooth has to be secured in both the fore-aft axis and the side-to-side axis. As the harrow is pulled over large clumps of earth, rocks, debris and the like, the teeth tend to be bent both rearward and forward, and also to either side. If the teeth turn sideways, the harrow will no longer work. It is very difficult to mount spring teeth without developing stress concentrations in the mounting eye or lug of the spring tooth. More often than not the spring tooth breaks in the mounting lug. Then the fastener will break in some instances. An example of this type of harrow is in C. B. Blair, U.S. Pat. No. 3,976,145. 
     The most recent and closest known example of prior art is a spring tooth harrow utilizing an angle iron frame to which a spring tooth having a helical coil spring is attached. The angle iron has a lower flange in which an aperture is pierced. A slot is notched in the lower edge of the angle lower flange. The tooth has a U-shaped lug in which the outboard leg of the U-shape has a forwardly bent toe that goes into the notch. A bolt and washer secure the lug to the angle iron. This device weakens the angle iron and contributes to bent frames, and gives excessive stress concentration in the lug because the mounting footprint is too small, and experiences too much lug breakage or tooth bending. This harrow is subject of H. L. Kovar, U.S. Pat. No. 3,710,872 of Jan. 16, 1973. 
     OBJECTS OF THE INVENTION 
     It is an object of the present invention to provide a spring tooth harrow having an improved attachment of a spring tooth. 
     It is an object of the present invention to provide a spring type harrow tooth having an improved mounting lug. 
     It is an object of the present invention to provide a new spring tooth attachment clip for securing a spring tooth to the frame of a harrow. 
     It is an object of the present invention to provide a new and improved harrow frame and spring tooth retainer clip for future securement of a spring tooth thereto. 
     These and other objects of the present invention will become manifest to those versed in the art upon review of the teachings herein. 
     SUMMARY OF THE INVENTION 
     According to the principles of the present invention, a spring tooth harrow has: 
     (a) a planar frame flange, 
     (b) a harrow spring tooth having a suspended tine and an intermediate spring and a cantilevered generally U-shaped mounting lug compressed against the flange, 
     (c) a tooth attachment clip having an L-shape with a first leg compressed upon the U-shaped lug, and 
     (d) a clip second leg abutting against an outer lip of the flange and extending between an inboard leg and outboard leg of the lug, and a fastener extending through the clip, lug and flange compressively mounting the lug of the tooth to the frame; with the fastener and the second leg transversely fixing the tooth. 
     A spring type harrow tooth has a single suspended tine, an intermediate helical coil spring, and a generally U-shaped mounting lug having: 
     (1) a generally straight inboard leg extending from the coil spring, 
     (2) a generally semi-circular medial leg extending from the inboard leg, 
     (3) a straight outboard leg extending generally parallel to the inboard leg, the inboard and medial and outboard legs being co-planar; and 
     (4) an outwardly divergent angle in the lug between the inboard an outboard legs. 
     An L-shaped spring tooth attachment clip for securing a spring tooth to the frame of a harrow has: 
     (a) a first leg with an inner surface for compressing a lug of a spring tooth, 
     (b) structure in the first leg for securement of the clip to a frame of a harrow, 
     (c) a second leg at a generally right angle to the first leg, the second leg having a length greater than the diameter of wire used for the spring tooth; 
     (d) a rear shoulder on the first leg and wider than the second leg, and 
     (e) an acute angle between opposed lateral edges of the second leg, the angle being in the range of 10-30 degrees. 
     The combination of a harrow frame and a spring tooth retainer clip has a frame with first and second flanges and a lip on the first flange, an L-shaped tooth attachment clip having a first leg with a length generally the same as the first flange, a second leg at a generally right angle to the first leg and with a length greater than the wire diameter of a tooth for the frame, a first leg rear shoulder wider than the second leg and abutted against the second flange, a second leg inner surface abutted on the lip, a fastener through the first leg and first flange with the clip being rotatably fixed to the frame by the abutting shoulder and second leg, and in which the fastener and opposing lateral edges of the clip second leg jointly form structure for transversely fixing the tooth to the frame. 
    
    
     These and other objects, advantages and features of the present invention will become apparent to those versed in the art after consideration of the following detailed description and the drawing a part hereof. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a forward looking elevational view showing a part of the harrow of the present invention with the spring tooth and tooth clip of the present invention; 
     FIG. 2 is a side elevational view thereof; 
     FIG. 3 is an upward looking plan view from the bottom thereof; 
     FIG. 4 is a projected 3-view drawing of the clip of the present invention and of FIG. 1; and 
     FIG. 5 is a sectional elevational view taken through lines V--V of FIG. 1. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The principles of the present invention are particularily useful when embodied in a spring tooth harrow, a portion of which is illustrated in FIG. 1 and generally indicated by the numeral 10. 
     The harrow 10 has several flange members, one of which is shown and indicated by the numeral 12. The flanges 12 form at least part of the frame of the harrow 10. The flanges 12 are usually part of an L-shaped section 20, commonly called angle-iron. Several of these L-sections 20 are usually located one in front of the other, and fore-aft members (not shown) tie the L-sections 20 together to form a frame of the harrow 10. The L-section 20 has a second flange 22 and the previously mentioned flange 12 can be considered the first flange 12 and it has an outer lip 24 which is advantageously used as will subsequently be explained. 
     The harrow 10 has a plurality of spring teeth. One such harrow spring tooth is generally indicated by the numeral 14. Each tooth 14 is held to the planar flange 12 by an attachment clip 16 and a fastener 18 extending through an aperture 19 within the flange 12. The aperture 19 and fastener 18 are closer to the second flange 22 than to the lip 24. 
     The tooth 14 has an elongate suspended tine 26 which is suspended from a suspended end 28 of an intermediate helical coil 30 which may have its coil 30 wound in a conical form as is shown. A generally U-shaped mounting lug 32 (or mounting end) extends from a first coil 34 of the coil spring 30. 
     The lug 32 has an inboard leg 36, an outboard leg 38 and a medial leg 40 between the inboard and outboard legs 36, 38. 
     The inboard leg 36 and the outboard leg 38 have between them an acute angle 42 which is divergent from the medial leg 40 and which is preferrably less then fifteen degrees and greater than five degrees; the optimal acute angle 42 is in the range of seven and one-half to twelve and one-half degrees. The acute angle 42 is symetrical about a theoretical plane 44 which is perpendicular to a theoretical axis 46 of the coil spring 30 and which is centered between the inboard and outboard legs 36,38. The inboard leg 36 is generally straight and extends tangentially from the first coil 34 and preferrably at the same angle as the nominal pitch angle of the coil spring 30. One-half of the acute angle 42 is preferrably equal to the coil spring 30 pitch angle. The medial leg 40 is generally semi-circular and has an internal radius 48 which is greater than a radius of the diameter of the fastener 18. The medial end 40 extends beyond the largest diameter of the coil spring 30 which positively spaces the coil spring 30 from the second flange 22. The radius 48 is larger than a radius of the diameter of the wire of the spring tooth 14, and less than the diameter of the wire of which the tooth 14 is made. The mounting lug 32 lies entirely in a theoretical plane 50 which is co-planar with the flange 12 and from which the tine 26 is spaced. This spacing 52 is approximately the diameter of the wire from which the tooth 14 is made. The preferred diameter of wire for the tooth 14 is 0.375 inch. The outboard leg 38 has a straight length longer than the inboard leg 36 and longer than the height of the flange 12 so that the outboard leg 38 extends out beyond the flange lip 24. 
     The L-shaped spring tooth attachment clip 16 for securing the tooth 14 to the harrow 10 has a first leg 54 and a second leg 56 at a generally right angle to the first leg 54. The first leg 54 has a generally flat inner surface 58 for compression of the mounting lug 32 to the flange 12. A rear shoulder 60 is wider than and parallel to the second leg 56. The shoulder 60 abuts against the second flange 22. An aperture 62 is provided for the fastener 18. The aperture 62 is nearer to the shoulder 60 than to the second leg 56. The second leg 56 has a length 64 between the first leg 54 and a distal end 66 which is greater than the diameter of the wire of the tooth 14 for which the clip 16 is specifically intended. The inner surface 68 of the second leg 56 abuts against the flange outer lip 24. An included angle 70 between the first leg 54 and the second leg 56 is less than ninety degrees and preferrably greater than eighty degrees; the optimal angle 70 is about eighty-five degrees. The second leg 56 has a taper 72 diverging from the distal end 66 to the first leg 54, and then along the first leg 54 toward the aperture 62. The taper 72 preferrably does not extend beyond the aperture 62. The taper 72 is an acute angle in the range of ten to thirty degrees; an optimal angle for the taper 72 is about twenty degrees. The taper 72, the second leg 56, the first leg 54 and the shoulder 60 are all preferrably symetrical about a theoretical centerline plane 74 which is perpendicular to and centered upon the first leg surface 58 at the centerline of the aperture 62 and the fastener 18 which ends up being through the aperture 62. On each side of the second leg 56 are opposed lateral edges 76 which form the taper 72 and which transversely fix and bias the tooth mounting lug 32 as will be described. The clip aperture 62 registers with the flange aperture 19 so tht the shoulder 60 abuts against the second flange 22 and so that the clip second leg 56 abuts against the flange lip 24. Between the first leg 54 and second leg 56 is an internal radius 78 which is less than the radius of the wire used for making the tooth 14. 
     In use of the harrow 10, tooth 14 and clip 16 of the present invention, the harrow 10 is utilized to break up plowed farm field, to flatten fields and for finer preparation of land for crop planting and the like. The tines 26 take a tremendous physical beating and the clip 16 and mounting lug 32 co-operatively mount the tooth 14 to the harrow 10 in an exceptionally reliable and strong manner. The tooth 14 is placed against the flange 12, the clip 16 is placed over the mounting lug 32 and the fastener 18 is loosely fastened. As the fastener 18 is tightened up, the clip lateral edges 76 are driven between the inboard and outboard legs 36, 38. The acute angle 42 between the legs 36,38 is engaged by the lateral edges 76 and the mounting lug 32 is biased upward until the medial leg 40 is against the second flange 22 and spaced above the fastener 18. As the clip 16 is finish tightened, the mounting lug 32 is compressively clamped securely between the clip 16 and the flange 12. In operation, loads from the tine 26 are passed through the coil spring 30 to the mounting lug 32 and then to the clip 16 and flange 12. The loadings imparted to the clip 16 are transferred by the rear shoulder 60 to the second flange 22 and by the second leg 56 to the first flange 12 and the clip 16 is radially fixed to the angle section 20 jointly by the abuttment of both the clip shoulder 60 and the second leg inner surface 68. Lateral bending of the tooth 14 is re jointly by the fastener 18 which contacts the inboard and outboard legs 36, 38 on their straight length and below the medial leg 40, and by the clip second leg 56 which with its lateral edges 76 picks up the outer ends of the inboard and outoard legs 36,38 and transfers their loading directly to the outer lip 24. The inboard leg 36 and outboard leg 38 both apply their fore-aft loads directly adjacent the flange lip 24 and the widest and largest possible footprint of the mounting lug 32 upon the first flange 12 is attained for minimal stress concentration in the lug 32. 
     This clip 16 and mounting lug 32 and combination of the frame with the L-shaped section 20 and clip 16 significantly expand the footprint of load application into the L-section 20 of the harrow 10, and reduce the actual and stress loads upon the fastener 18. The loads and stresses in the mounting lug 32 are minimized. The second flange 20 and the frame of the harrow 10 are now stronger because the first flange 12 no longer needs to be notched to transversely index the spring tooth 14. 
     Although other advantages may be found and realized, and various and minor modifications suggested by those versed in the art, be it understood that I wish to embody within the scope of the patent warranted hereon, all such embodiments as reasonably and properly come within the scope of my contribution to the art.