in fig1 a sickle or knife assembly for cutting hay , grain or other crop plants is indicated generally at 10 and is made up of a plurality of sickle modules , for example , a drive head sickle module 11 , and intermediate sickle module 12 , and an outer end sickle module 13 . the knife assembly 10 , and each of the sickle modules 11 , 12 and 13 are made to be used with conventional knife guards ( not shown ) and driven from a reciprocating drive pitman or crank . the sickle modules include a standard cross - sectional size knifeback or bar and standard size knife sections , except that in the splice areas between sickle modules , a knife section having additional holes for fasteners for making the splice is provided . the knifeback , as used herein , is the elongated bar member on which the knife sections are mounted , through the use of rivets or bolts . as shown in fig1 the drive end sickle module 11 has a plurality of standard knife sections 16 thereon , and also has a knife drive head 17 mounted at the end of the sickle bar assembly 10 in a conventional manner . the knife drive head 17 has a drive hub member 18 that is coupled to a reciprocating drive so that the knife assembly is reciprocated back and forth along its longitudinal axis during operation as indicated by the double arrow 20 . it should be noted that the knife head 17 has an elongated shank 21 that is attached to the modular sickle section 11 through a substantial number of bolts indicated generally at 22 which are sufficient in number so that the frictional holding force between the shank 21 and the knife sections , and thus with respect to the knifeback , will be adequate to carry the loads needed for reciprocating the knife assembly of the desired length when in use . a substantial number of bolts 22 are needed to provide the friction loading between mating surfaces to transmit the loads encountered in using a long knife assembly . the intermediate sickle module 12 is coupled to the drive end sickle module 11 at a splice covered by a splice knife section 25 , at the end of the intermediate sickle module adjacent the knife head module . the intermediate module 12 is also coupled with a splice knife 25 at its outer end to the outer sickle module 13 . the outer sickle module 13 and the intermediate or center sickle module 12 are both of length to have a plurality of knife sections 16 thereon . the drive head module will be long preferably , and so will the intermediate modules . these long modules will be between six and eight feet . for example , sickle modules in six , seven and eight foot lengths can be utilized , and the outer or end sickle modules 13 and drive head modules 11 will be separately constructed from the center sickle modules 12 , which can be universal and used with different types of outer or knife head modules . the outer module 13 will usually have a half knife section at its outer end as shown in fig1 . half knife sections can be at either end of the knife assembly . the end module can be made very short and can be selected so when a long drive end module and a reasonable length second module is used , the outer module will provide the desired overall length of the knife assembly . the junction or splice knife sections 25 overlie the splices of the adjacent individual sickle modules , and as shown in fig2 and 3 , the knife sections 16 are preassembled and mounted onto knifeback portions 30 and 31 , respectively . the knifeback portion 31 forms the outer end of the drive sickle module 11 , as shown , and the knifeback portion 30 forms the knifeback for the intermediate sickle module 12 . these knifeback portions 30 and 31 each have an integral splice plate 30a and 31a , respectively , formed therein as can be seen in fig3 . the splice plates are made by reducing the thickness of the knifeback to one - half the normal thickness and making the splice plate portions complemental so the splice plates form overlapping splice portions . when the splice plates are overlapped , one on top of the other , the total thickness of the knifeback in the splice area is equal to that of the individual knifeback portions 30 and 31 . the integral splice plates 30a and 31a join with the main parts of the knifeback portions through smooth radius junction areas 30b and 31b , respectively , so there are no sharp corners that result in stress raisers at the splices . the individual sickle modules are factory fabricated , as stated , with the knife sections 16 fastened onto the respective knifeback portions through the use of fasteners such as bolts indicated at 33 , or with suitable rivets , as desired . the sickle modules are preferably factory assembled for reduced costs , and when the individual sickle modules are to be joined together , the complemental splice plates formed at the adjoining ends of the knifeback portions 30 and 31 are overlapped , so that openings indicated at 34 and 35 in the splice plate 31a , and at 34a and 35a in the junction plate 30a , align . the knifeback portions 30 and 31 are placed along a straight edge to make sure that the knife assembly is straight . then , a splice knife section 25 , which has four openings or holes therein , as shown , is placed over the overlapped splice plates . the four holes in the knife section 25 are made so that two outer holes are the same spacing as the holes for receiving bolts in the standard knife section 16 , and two center holes align with , overlie , and provide for placing fasteners through the holes 34 , 34a and 35 , 35a . the fasteners can be suitable bolts that are placed through these openings and secured . these bolts or rivets 42a - 42d can be the same as the standard bolts or rivets 33 . the assembly of the two sickle modules is then completed . all that is necessary is to place the modules with the integral splice plates overlapping , straighten the modules longitudinally , put a splice knife section in place , and put in four fasteners , such as bolts , through the splice knife section 25 and aligning splice plate openings . the overlapping of the splice plates 30a and 31a provides a substantial area of mating normally flat surfaces which are frictionally held together by the splice bolts 42b and 42c . the surfaces which mate can be milled rough , roughened or knurled for added holding power . it can be seen that because the splice knife section 25 has separate bolts 42a and 42d in the respective knifeback portions 30 and 31 , as well as two bolts 42b and 42c that pass through the splice plates , any shear loads will be carried through five shear surfaces of the bolts . in other words , assuming that the drive load is on the knifeback portion 31 , the shear load is carried through a shear surface of the bolt 42a passing through one hole , in knifeback portion 31 and the hole of splice knife section 25 adjacent the knife head and through two shear surfaces on each of the splice plate bolts shown at 42b and 42c . the longitudinal reciprocating load carrying capability of the splice is kept high because the surface area for friction forces resisting longitudinal axial loads is substantial between the mating surfaces of the overlapping splice plates . the knifeback portions 30 and 31 are the same cross - sectional size as the standard knifeback , and the ability to carry necessary loads indicated by the double arrow 20 is maintained . the splice knife section overlapping the splice , also helps to strengthen the splice . for example , the breakage of a knifeback is most likely to occur where the splice plates 30a and 31a from the main knifeback portions or across one of the holes in the splice plates . if the knifeback fails at its junction with a splice plate , for example , its region 30b , bolt 42d will have to shear as well , because splice knife section 25 spans the region 30b . if failure in splice plate 30a occurs , across hole 35a , for example , bolt 42d again will have to shear and thus additional load carrying ability is provided by the splice knife section and its fasteners . another feature of having long sickle modules at the drive end ( as long as permissible shipping length ) is that the very high loads that are carried by the knife head 17 , which are proportional to the length of the knife assembly for a given cutting condition , reduce as a function of distance from the knife head , so that at the outer end of the drive sickle module 11 , the longitudinal loads on the knifeback have been reduced . if , for example , the first splice is 8 feet from the drive head , on a 16 foot sickle bar assembly , the load at the splice between the outer sickle module to the drive sickle module would only be one - half of the load carried by the knife head . thus , the splice strength not only is increased over the prior art , but the loads are reduced at the splice over the types of knife assemblies shown in the prior art where very short , individual knifeback portions are used . rigidity also is substantially increased because the splice plates have mating , longitudinally extending generally flat surfaces which can be tightly clamped together . there are three or more splices in a very long knife assembly . although the present invention has been described with reference to preferred embodiments , workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention .
a modular knifeback for a sickle knife assembly that is made into lengths that are standardized for permitting ease of shipment , storage and handling , and which lengths can be spliced into a desired extended length knife assemble for use in harvesting machinery , or the like , without sacrificing rigidity and strength where the modular sections are joined together . the modular sections are made sufficiently long so that the bolts or rivets used where the modular sections join are capable of withstanding the loads that are incurred on the knife assembly during use . the modular sections of the sickle are easily kept , and stored , and are assembled using standard components without specialized tools .