Patent Application
20120255339
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1. Field of the Invention
The present invention relates to a sickle bar mowers or crop harvesting machines and more particularly to a method of making integrated forged sickle guard fingers.
2. Description of the Related Art
Sickle guards are well known in the art and are sometimes referred to as cutter guards. Sickle guards are typically associated with mowing and cutting machines such as harvesters, mowers, thrashers, swathers, or agricultural machines as well as lawn and trimming devices of all types and purposes which involve a shearing action requiring cooperation between a stationary guard and an associated reciprocating sickle bar.
Originally, the great majority of the guards for reciprocating cutters were generally made from cast malleable iron with a steel ledger plate riveted to the body of the guard to provide a hard and lasting cutting edge to cooperate with the reciprocating knife of the cutters. Under especially hard cutting conditions, especially in stony fields, cast malleable guards have often proven to be unsatisfactory as such guards were easily bent and when straightening often broke or fractured. In an attempt to overcome these disadvantages, the guards have also been made from cast steel and drop forged steel. A well known objection to such processed guards is that they are massive, heavy, and much more expensive to make than the ordinary cast malleable guard due to the nature of the process of manufacture. A further objection to the cast or forged steel guard is that breakage of these guards will often occur because the steel guard has very little elasticity due to its great strength and rigidity. Therefore, breakage will often occur in the event a stone or hard object is caught between the guard and a portion of the reciprocating knife or cutter. Ordinary malleable iron will yield sufficiently under impact to prevent breakage of the knife section but will fracture more easily when attempts are made to straighten the guard after yielding. Steel guards however will yield very little and break upon impact with a stone or hard object.
Because of these known problems with guards manufactured from either malleable iron or steel castings, various processes have been proposed to impart to the sickle guards the required degree of strength required as well as at the same time, give the sickle guard a sufficient degree of elasticity to enable it to yield under impact and have it spring back to its initial shape after a stone or hard object obstruction which has lodged between the guard and the cutter has been removed.
Vutz, U.S. Pat. No. 2,278,393, proposes a sickle guard having a main body portion made from flat stock such as steel sheet or strip steel, heat treated to provide the proper strength as well as to allow it to spring or become deformed under the strain of an obstruction and spring back to its original shape after the obstruction has been removed. A blank is formed, in either hot or cold conditions, to the desired contour of the main portion of the guard. A forward lip portion has sides inclined inwardly in a forward direction to assume a trough form which is V-shaped in cross-section with the edges thereof in the same horizontal plane. After hardening the edges formed on the sidewalls, there is attached to the outer end of the lip a pointed steel tip or nose having a rearwardly extending portion which overhangs the edges of the lip. The nose and its overhanging part are formed by drop forging, casting, or stamping, and thereafter, rigidly attached to the forward end of the lip by welding.
Mills, U.S. Pat. No. 2,619,787, discloses a forged and thereafter machined sickle guard wherein a steel bar of a length determined by the number and spacing of the fingers of the guard is raised to the required forging heat and then placed over the lower forging die. The upper and lower dies are brought together to cause the blank to be formed to the desired shape. The partially completed forging is turned 180° and acted upon by bringing the dies together again to complete the guard forging. During the forging, a web will be formed and this commonly called “flash” is then removed by a shearing die. After the punching operating for the mounting stud openings, slots are saw or mill cut in the fingers of the guard to receive the cutting knives of the mowing machine. As the slots are cut, the stress in the forging is such that the lip portion of the guard fingers spring away from the body portion resulting in a wedge shaped slot. After the slots have been cut in the guard fingers, the cutting edges are subjected to heat treatment to harden the cutting edges and if desired, it is preferred to case harden the whole guard unit.
Because of the great deal of labor costs involved in the above procedure as well as the high costs of one-piece forgings which required separate machining operations to provide shaped edges and ground bevels, Haban, U.S. Pat. No. 3,682,021, proposed the formation of specially shaped fingers in a stamping die in such a manner that there is a flat V-shaped marginal portion on the top of each finger which can be ground in a single operation to provide shearing edges in conjunction with bevels on the underside of the blade which are produced simultaneously with the forming operation without any additional machining.
As is well known to a person skilled in the art, each step in the processing of the sickle guard unit adds significant cost to the overall cost. Therefore, what is needed is a process to fabricate a sickle guard that completely eliminates any machining cost and yet provides a sickle guard that imparts maximum strength to the body portions of the guard and at the same time produce a region along the peripheral surface of the ledger surface which is formed into a cutting edge.
The present invention provides a novel method of manufacturing a sickle guard which completely eliminates any machining requirements in the process of making the sickle guard. In order to affect economy in the manufacture of the sickle guard, the method of manufacturing provides for the forging of the lower body portion of the guard and the upper body portion of the fingers as separate parts which after processing of the separate parts are MIG welded to create the integral sickle guard. By processing the lower body portion separate from the upper body portion, the ledger surface of the lower body portion can be processed through a coining operation wherein the ledger surface is subjected to a sufficiently high stress to induce plastic flow of the entire ledger surface material, work hardening the surface, and thereby creating a sharp cutting edge about the entire periphery of the ledger surface.
Both lower body and upper body portions are thereafter heat treated and hardened. Following through hardening, the cutting edge of the lower body portion is induction hardened to provide a sharp cutting edge for the life of the sickle guard. Lastly, the lower and upper body portions are located in a welding fixture such that the complimentary beveled surfaces adjoin each other and a MIG welding operation joins the upper and lower body portions into a single cutter guard. The completed process may be followed by a coating step which is dictated by customer choice.
It is a primary object of the novel method of manufacture to provide an improved method of manufacturing sickle guards for a mowing machine.
A further object of the present invention is to provide an improved cutter guard wherein the upper and lower body portions are forged as two separate pieces.
A further object of the present invention is to provide a method of manufacturing sickle guards which make it possible to provide a finger element of any desired length having any desired number of shear fingers thereon.
Still a further object of the present invention is to provide a method of manufacturing to provide a sickle guard which is forged in such matter that the peripheral edge of the forging coincides with the cutting edges of the guard such that the surface creating the cutting edges can be coined and hardened to provide a sharp cutting edge for the work life of the sickle guard.
It is yet a further object of the present invention to provide a method of manufacturing cutter guards which is forged as two separately processed pieces and after processing is fixtured and MIG welded into a unitary sickle guard.
Further objects of the present invention are to provide sickle guards that are simple in construction, inexpensive to manufacture, efficient in operation, and well adapted for the purposes described.
Other objects and advantages of the present invention will become apparent from the following detailed description and accompanying drawings.
Referring now to the drawings, there is shown a pair of cutter or sickle guards 5 having an integral body portion 10, 10 which consists of a plurality of fingers in a side-by-side relationship 12 which are joined at one end by an upstanding rib 14 integrally formed therewith. Any number of sickle guards 5 may be arranged side-by-side to provide the desired cutting width. The sickle guard 5 is fabricated as a forging and in the embodiment shown in
In the forging of the sickle guard 5, there is formed a transversely extending upstanding rib or trash bar 14 at the rear of the ledger surface 18. The trash bar 14 has a central portion 28 with lateral extensions 30 defining a sidewall 32 of a shallow groove 34 extending transversely to the pair of spaced apart longitudinally extending guard fingers 12. The opposing side wall 36 of the shallow groove 34 is defined by a transversely extending wear bar 37. The shallow groove 34 is suitably dimensioned for receiving a knife bar 39 to which the cutter sections 24 of the mowing machine are riveted. The integral body portion 10 also includes mounting flanges 38 each aligned with one of the fingers 12 and extending from the transversely extending trash bar 14. The mounting flanges 38 each include a through-hole 40 to mount the sickle bar to a support bar 41 of the mower or other implement.
As discussed above, in the forging of the guard fingers 12, the upper body portions 20 are forged separate from the lower body portion 16.
Following the coining operation of the ledger surface 18, the lower body portion 16 is thereafter fixtured with the beveled surface 42 located to receive the beveled surface 46 of the upper body portion 20 and processed through a MIG (metal inert gas) welding process to combine the nose portion of the fingers 12 into a unitary member. The upper body portion 20 is forged and heat treated separate from the lower body portion 20 prior to the welding process.
The advantages of the sickle guard 5 may best be appreciated from a consideration of the method by which it is manufactured. First, a steel bar blank of any type of cross-section is used having a sufficient length determined by the number and spacing of the fingers 12 of the sickle guard 5. The requisite steel bar is raised to the required forging heat temperature. The heated bar is placed over the portion of the lower forging die having the complimentary forging cavities to the number and spacing of the fingers 12 of the sickle guard 5. The upper and lower dies are then brought together under great pressure to cause the steel bar blank to be formed roughly of the desired shape of the truncated lower body portion 16. It is to be understood that the upper body portion, using an identical process is forged in a second set of dies in the same manner as the lower body portion. The dies are then separated and the hot forging is processed through upper and lower trim dies to trim the flash from each of the forgings. While processing through the trimming operation the through holes 40 for receiving mounting studs are also punched into the mounting flanges 38 at the heel of the lower body portion of the sickle guard 5.
Following the trimming and punch operation, the forging of the lower body portion 16 is processed through a coining operation wherein the entire ledger surface 18 is coined subjecting the forging to a sufficiently high stress to induce plastic flow of the entire ledger surface material, work hardening the surface, and thereby creating a sharp cutting edge along the entire periphery of the ledger surface 18.
The upper body portions 20 are processed separately from the lower body portion 16 but an identical procedure is used with the exception of punching a through hole 40 therein.
After the coining operation, both the lower body portion 16 and upper body portion 20 of the cutter guard 5 are subjected to heat treatment to through harden each of the component body portions of the sickle guard 5. Thereafter, the lower body portion 16 is induction hardened to harden the cutting edges. The final step in the process of making the sickle guard 5 is to fixture the upper body portion 20 with its beveled surface 46 located adjacent to the beveled surface 42 of the lower body portion 16 which is also located and clamped in the welding fixture and MIG (metal inert gas) weld the upper body portion 20 to the lower body portion 16 to complete the sickle guard 5 into a single cutter body. Any surface finishing applied to the sickle guard 5 is customer specific and may include paint or phosphate coatings.
It should now be apparent that, by reason of the novel method of manufacture described hereinabove, a sickle guard has been provided which is fabricated using two separate forgings, one to forge the lower body portion and a second to form the upper body portion, which are after separate processing MIG welded together into a unitary sickle guard. The novel process eliminates all machining typically practiced by the prior art method, thereby resulting in a substantial savings of time and labor because additional manufacturing steps have been eliminated reducing the overall cost of the sickle guard.
Having described the novel method of the invention,
