US2119479A - Lug strap - Google Patents

Description

May 31, 1938.

H. M. BACON v 2,119,479

LUG-,STRAP Filed March l2, 1936 .2. @m4 4' ,IiHlHglllHlljHlgf ,Nillllmllllirlll II l.. 1;H!!!fi-Ml.'iilil Patented May 31, 1938 UNITED STATES PATENT oFEicE LUG STRAP Henry Miles Bacon, Warren, Ohio, assigner to The Dayton Rubber Manufacturing Company, Dayton, Ohio, a corporation of Ohio Application March 12, 1936, Serial No. 68,534 2 Claims. (Cl. 139-153) This invention relates more particularly to imand its life would be materially shortened. Parprovements in lug straps of laminated constructicularly in the case of straps constructed of fabtion wherein superposed plies of fabric are united ric and glue some layers of the fabric became by a bonding material to form the strap. stretched and others became wrinkled so that Important objects of the invention are, to proonly the middle layers were in a normal condition 5 vide a very durable lug strap of the said characof tension, with consequent concentration of ter; to provide such a strap constructed for even stress and injurious strain. Efforts were made distribution of working stress throughout the difto overcome this defect but they involved laboriferent plies of fabric; to provide for improved ous and costly methods of construction and failed simplified construction of the bend or bow porto avoid liability of flawed construction. The 10 tion of such a strap; and to provide an improved employment of glue in the structure of the strap method of making a lug strap of the said lamiis also objectionable for the reasons that the glue Hated tYDetends at times to soften under the humidity of Other objects of the invention will appear herethe weave room and at other times it cracks under inafter. the shocks and flexure to which the strap is subl5 In the drawing, Fig; 1 is a perspective view of jected in service and in handling. a core member employed for winding thereon My invention overcomes the defects noted and a fabric sheet coated with a bonding material, provides a strong, durable lug strap and a conas a step in lug strap manufacture; vcnient and comparatively inexpensive method Fig. 2 a cross sectional viewI of the said core for manufacturing lug straps in large quantities 20 and showing diagrammatically the fabric wound and with minimum liability of flawed constructherearound; tion. The invention also provides a lug strap Fig. 3 a plan view of the sleeve formed by the made of such material as to render the strap wound fabric, with dot and dash lines indicating free from attack by rodents and having other the transverse severing of the sleeve to form a advantages Which Will appear hereinafter 25 multitude of double straps; In the manufacture of ,lug straps embodying Fig. 4 a sectional view showing the molding of the improved construction I select a wide sheet l a double lug strap; of square-woven textile fabric with maximum Fig. 5 a transverse section on the line 5 5 cf warp strength and with pick strength consistent Fig- 4; y with easy handling. Both sides of this sheet I 30 Fig 6 a plan View 0f a molded double strap; coat with a bonding material 2 which is prefer- Fig. '7 a perspective view of a finished single ably a rubber composition capable of being vui- Stlap; canized to a hard state and having a low viscosity Fig. 8 a partial sectional View similar to Fig. 4, prior to vulcanization. Other bonding materials but on a central plane at a right angle thereto, having the required therme-flowing and Setting 35 showing the molding cf a double lug strap with properties may `be employed but rubber is preintegral convex cushions within its bends; ferred, for reasons which Will appear hereinafter. Fig. 9 a detail sectional view of an end of the The Sheetl. Coated with the rubber COmPOSimold core, taken on the line 9--9 of Fig, 8; and tion is wound around a core 3 whose cross section Fig. 10 a perspective view of the lug strap with conforms substantially to the interior of an elon- 40 such a convex cushion. gated loop such as would be defined by placing aLug straps in use heretofore have customarily two U-shaped lug straps end to end. The side been made of leather or wood, bent into shape, edges of the core are rounded, as at 4, in accordor of canvas duck or ticking. In the employance with the curvature of the interior of the ment of the latter material it has been customary bend or bow of the lug strap. An oak plank so 45 to roll the fabric spirally, cement it with glue and formed will serve satisfactorily for the core. As then bend and mold the roll so formed into the the sheet is wound it is kept sufficiently taut for desired U form. In the employment of any of smoothness, and the winding is continued to form said materials the bending thereof into U-shape a number of superposed plies sufficient to build materially impaired their strength owing to the the structure up to a desired thickness exceeding 5u fact that the material at the outside of the bend that of the finished lug strap. The sheet should would be stretched and the material at the intebe wound with its warp threads or strands, desigrior of the bend would be compressed or cramped. nated W in Fig. 3, running straight lengthwise of Consequently the lug strap would be incapable of the windings, around the core 3. Thus the coat-- uniformly distributed resistance to working stre-ss ed sheet l is formed into a flat, multi-ply sleeve with the plies lying smoothly one upon' another. 'I'his sleeve is removed from the core I and severed along the transverse lines 5 equally spaced along the sleeve to thereby provide va multitude of elongated flat loops each conforming substantially to a pair of lug straps arranged end to end. Preferably the width of these partly formed double straps cut from the sleeve, that is, their Width between the lines 5l is about one thirtysecond of an inch finished strap.

Each double strap is next subjected to a molding and preliminary vulcanizing operation. This molding and vulcanizing operation is performed to mold the strap to the desired shape and cross sectional dimensions, bond together the plies and vulcanize the rubber composition to a preliminary soft rubber state.

In preparation for the molding and vulcanizing operation a mold core 6 of steel or other suitable material is fitted into the loop defined by the double strap. This the shape and dimensions desired for vthe interior of the strap. As shown, and properly rounded ends. The strap and core are placed between opposed blocks 1 of a split mold. Said blocks have in their opposed faces elongated cavities 8 with rounded ends and conform exactly to the desired shape and dimensions of the exterior of the strap. The plane of separation of the blocks occurs at thel center of the bends of the.strap, and the dimensions of the cavities 8 and of the core 6 are so correlated that when the mold is closed the space between the rounded ends'of the core and the rounded ends of the cavities between the flat sides of the core and the flat bottoms of the cavities.

'I'he molding operation is performed under heat and pressure to vulcanize the liminary, soft rubber state. Due to the shape and proportions of the parts of the mold, when the mold is closed, the flat, leg-forming portions of the strap will be subjected to greater compression than the bends of the strap, and excess bonding material will be flowed from said at portions into the bends. Thereby the bends, while also compressed, are made thicker and less dense than the leg-forming portions. 'I'he pressure throughout the entire strap is sufficient to unite the plies intimately and evenly.

The molded double strap is next removed from the mold.' the core 6 is withdrawn, the strap is cooled and excess, overflow rubber is trimmed off. The double strap is severed in the middle to form two single straps S. Also, the usual slots 9 are made in the legs of the strap either before or after severance. Finally the vulcanization of the rubber is completed to bring it to a, hard state, This may be done by l formed straps to dry heat in a suitable oven.

The` employment of the materials and the method described produces a superior strap which satisfies all service requirements. Hard rubber is a very satisfactory material because of its nonbrittle nature, its high tensile strength, its imperviousness to weave, room humidity and also because rodents will not eat it. 'I'he arrangement of the fabric with its warp threads running of the strap contributes to tensile less than that desired for the materially exceeds the space rubber to a pre-` subjecting the completely is performed in a. manner to reduce liability of unevenness in the plies to a minimum. 'Ihe usual stretchingvof the plies at the outside of the bow of the strip and the cramping and buckling of the plies at the inner side of the bow is entirely avoidedin a simple manner by my preforming method. Substantially all fabric'plies employed in the structure of the strap extend continuously throughout the length of both legs of the strap andaround the bow. A desired excess thickness of the bow of the strap is obtained by flowing excess bonding material into the bow. This avoids employment of short plies of fabric to build up the thickness of the bow. The thickened bow provides the required cushioning effect. Also while of less density than the legs of the strap the bow has adequate total strength due to its increased thickness.

Due to the fact that the fabric is coated upon both sides with the rubber composition and due also to the fact that the composition is confined in the molding operation the finished strap contains much more of the composition than is required for mere bonding. It comprises a large part of the strap, as shown, and forms a matrix enveloping the fabric. 'I'his matrix is hard, tough, non-friable, resilient and moisture-impervious. It surrounds the individual threads of the fabric and is reinforced the fabric plies. v

If a plug, not shown. is required for the interior of the bow of the strap it may be tted, drilled and riveted into place.

It is also possible to form a satisfactory convex cushion in the bow of the strap in. a very 'I'his maybe done as shown in F1g.,8 by provision of a mold core 6a similar to the core 6 except that it has concave ends 6b conforming to the desired shape of the cushion. The molding pressure causes the fabric and excess bonding material to iill the concavities of the core and form the integral cushions l0. Otherwise the strap with the convex cushion is formed in precisely the same manner as the strap previously described.

What I claim is:

1. A lug strap comprising a U-shaped body formed of a moldable composition of controllable hardness having a rubber base, and a multiplicity of reinforcing plies of woven fabric laid in U-form, one within another successively Within4 v closed spaced warp threads running straight longitudinally of the strap, said moldable composition being compressed, molded and vulcanized and impregnating the fabric of the plies and forming a hard, tough, non-friable, resilient and moisture-impervious matrix enveloping the plies and surrounding' the individual threads of the fabric of the plies and reinforced by the plies throughout the entire strap, the number of plies in the bow being the same as in the legs, the moldable composition being of greater thickness in the bow than in the legs of the strap, and the bow being less hard than the legs.

2. A lug strap comprising a U-shaped body formed of a moldable composition of controllable hardness having a rubber base, and a multiplicity of reinforcing plies of. woven fabric laid in U- form, one within another successively within the U and evenly distributed in closely spaced relation throughout the thickness of said body and each throughout the strap by ply extending the length of both legs of the strap the plies and reinforced by the plies throughout and around the bow, said moldable composition the entire strap, the number of plies in the bow being compressed, molded and vulcanized and being the same as in the legs, the moldable comimpregnatng the fabric of the plies and forming position being of greater thickness in the bow a hard, tough, non-friable, resilient and moisturethan in the legs of the strap, and the bow being 5 impervious matrix enveloping the plies and surless hard than the legs;

rounding the individual threads of the fabric of HENRY MILES BACON.

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