US2716324A - Bonded knife head and knife assembly for reciprocating mowers - Google Patents

Description

Aug. 30, 1955 R, 1, M|| LER 2,716,324

BONDED KNIFE HEAD AND KNIFE ASSEMBLY FOR RECIFROCATING MOWERS Filed NOV. 16, 1955 Patented Aug. 30, 1955 United States ce 2,716,324

' in for the `reception of-rivets 11 which mount conventional i knife sections 12 and a knife head 13 to the vbacking 2,716,324 strip inconventional fashion. However, in accordance l, with this invention, additional securing means for 'both the noNEgFElggmDglgm 5 knife seetiens 12 and the knife head 13 is provided in the y formof athin layer of shock absorbing flexible bonding Raymond J. Miller, Detroit', Mich., assigner to Ford ymaterial 14 which is interposed between the abutting sur- Mofor Company, YDoni-bou Mich a corporation of faces of the backing. strip 10, the knife sections i12, and Delaware t the .knife head 13.

y y y t The bonding material is preferably fabricated from a Apphcatlon November 16 i953. senal Nm 392,289 10 class of synthetic resin adhesives known as'ethoxylenes 1f. 2-Chlms-V :(Cle 's6-*306) These compounds are obtained by etherification of dihyf droxy compounds or diphenols with epichlorohydrin. A

postulated chemical structure for this class `of resins Iis This invention relatesvto-an improved Vknife construction indicated below:

,I- ene on -I ons o\ l e 0:-om-dn-oni-o i: o-Cnrc/H-*oni .I H3 i v "rk y for agricultural mowers of the reciprocating knife type. These adhesives are suitably catalyzed for curing by For many years, substantially the same knife conthe addition thereto of urea-formaldehyde, melaminestruction has been utilized inall commercially successful formaldehyde and phenol-formaldehyde resins. Other agricultural mowers, namely, the individual knife elements curing agents include polyamides and amines such as and theso-called knife head, by which the knife was contriethylamine, diethylene triamine vand benzyld'imethyl'- nected to the driving Pitman, were secured to an elongated amine. t backing strip by the utilization of oneror more rivetsor i Other metal to metal adhesives of 'the synthetic resin similar types of mechanical fasteners. However, it has -type are also applicable'to usev in 'the present invention been long recognized that this type of fastening left much and include the butadiene-acrylonitrile copolymer modito be desired in that shearing or other failure of the rivets tied phenolics, related synthetic resin-rubber-type adduring operation of the mower has been a continuous probhesives, and the like. lem, resulting in relatively limited service life for any When using the resins disclosed, in accordance with the particular knife assembly before one or more rivets would present invention, the knife head 13 is preferably assembled have to be replaced. to the backing strip 10 under heat and pressure. First Accordingly, it is an object of this invention to provide the surfaces of the parts to be joined are cleaned and an improved knife assembly for reciprocated knife type coated with the catalyzed resin and clamped in an assemmowers characterized by the utilization of both rivets bled relationship for curing. Curing may be effected at and a layer of shock absorbing flexible bonding material o a temperature in `the range from room temperature to to effect the securement of the knife sections and the knife 250 C., preferably in a range from about 90 to 150 C head to the backing strip. for a period of time from about 0.25 to 2 hours. A tern- The specific nature of this invention, as well as other perature of about 100 C. was employed for curing the objects and advantages thereof, will become apparent knife heads used in the tests hereinafter described at a to those skilled in the art from the following detailed de- Cure time of about l hour. scription taken in conjunction with the attached drawings With the aforedescribed construction it has been found onwhich, by way of preferred example only, is illustrated that greatly improved service life can be obtained from one embodiment of this invention: the knife assembly. For example, a knife assembly which On the drawings; was secured only by rivets was found by accelerated field Figure 1 is a partial perspective View 0f a knife con- 50 eSt t0 haVe a SeIViCe life 0f Only 4.7 hOurS before One 0I' struction embodying this invention; more rivets failed, resulting in the disassembly of the knife Figure 2 is an enlarged Scale plan View of the knife of head. It is even more interesting` to note that tests of Figure 1; knife assemblies wherein the aforedescribed elements Fig 3 is a Sectional View taken on lthe plane 3 3 of were lsecured together only by the shock absorbing flexible Figure 2; 55 bondlng mztlerialsl1 had much shorltlerthserviceblife averaglng o y our. owever, wit e com ine ofligree 42-lldsectlonal new taken on the plane 4 4 rivet and shock absorbing flexible bonded construction em- F. 5 1t. 1 t 1 k th 1 bodylng th1s invent1on, the average service life of the asigure 1Samu 1p ane Sec 101121 VleW ta en on e me sembly before one or more elements thereof became 5 5 of Figure 2' 60 disconnected averaged 63.3 hours, or an increase of ap- As shown on drawmgs:

I proximately 1300% over the performance of the conven- A kmfe constructlon embodying this invention utilizes tional riveted construction,

conventionally shaped elements to form the knife assem- This unusual increase in service life can be theoretically bly but provides a novel means for effecting the secureexplained as follows:

ment of such elements in assembly. Thus, a conventional backing strip 10 of the usual elongated configuration is 1Natura1 and S nthetic Hi h Pol e 2 H. provlded. havmg a plurallty of spaced apertures 10a thoro- Meyer, 195o, Intersenee Pnbnners, ifir. Yfliipdmlzsn.

When rivets alone are used as a securing means, at

each stroke of the reciprocating knife assembly each knife section rivet is subjected to a large radial impact force with each reversal of movement of the knife assembly. Additionally, those rivets which secure the knife head to the assemblage were subjected to an axial component of impact force due to the fact that the pitman attached to such knife head inherently tends to alternately raise and depress the knife head relative to the backing strip4 Also, the knife sections were subjected to continuous longitudinal flexing of the backing strip 10 as it Was dragged over the ground or elevated to clear obstructions. Thus it was only a question of time until one or more rivets failed under the fatigue stress induced by such repeated impact forces. At the same time, however, the rivets were suciently rigid to adequately resist any substantial vertical displacement of the elements of the assembly relative to each other due to the flexing of the backing strip 10. On the other hand, when the shock absorbing flexible bonding material 14 is used alone, the impact forces due to the reciprocations of the assembly Will be absorbed over the entire area of the bonded surfaces and hence are greatly reduced in intensity. However, such bonding material could not successively resist the relative displacements of the elements of assembly produced by flexing of the backing strip and thus would fail rapidly.

With the combination of rigid rivet-type fastenings and the shock absorbing flexible bonding material, the impact loading on the rivets was greatly reduced, hence increasing their service life and the vertical displacements of knife sections and knife heads relative -to the backing strip due to flexing action were successfully opposed by the rigid rivets, hence minimizing the deterioration of the bonding material 14 with the over all result as indicated above, of a disproportionate but most desirable increase in service life of the new assembly.

It will, of course, be understood that various details of construction may be varied through a Wide range without departing from the principles of this invention and it is,

therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claims.

I claim:

1. In a reciprocating knife-type mower, comprising in combination a knife assemblage comprising a backing strip, a plurality of cutting elements mountable along said strip, rigid fastener means traversing said backing strip and said knife head for mechanically securing said knife head on said backing strip, and a layer of shock absorbing and exible ethoxylene synthetic resin interposed between said head and said backing strip to adhesively unite said knife head and said backing strip and provide a shock absorbing flexible bond to said knife assemblage upon longitudinal flexing and radial loading.

2. In a reciprocating knife-type mower, comprising in combination a knife assembly subjected to longitudinal flexing and impact loading comprising a backing strip, a plurality of cutting elements mountable along said backing strip, a knife head mountable on one end of said backing strip, rigid fastener means respectively traversing said backing strip and said cutting elements` and said knife head for mechanically securing said cutting elements and said knife head to said strip, and a layer of phenolic resin modified with a synthetic elastomer interposed between said cutting elements and said backing strip, and said knife head and said backing strip to adhesively unite said cutting elements and said knife head with said backing strip with a shock absorbing exible bond.

References Cited in the file of this patent UNITED STATES PATENTS 2,009,339 Davis July 23, 1935 2,460,181 Marshall Jan. 25, 1949 2,521,912 Greenlee Sept. 12, 1950 2,575,558 Newey Nov. 20, 1951 2,651,589 Shokal Sept. 8, 1953

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