COMPOSITE AUTOMOTIVE CONNECTING

ROD AND METHOD OF MANUFACTURE

RELATED APPLICATIONS

This application claims benefit of U.S. Provisional Application No. 61/979648, filed on April 15, 2014, which is herein incorporated by reference in its entirety.

BACKGROUND

Replacement of dense metals with relatively lightweight polymeric components in the bodies of automotive, aircraft, and other vehicles has made such vehicles lighter, increasing fuel efficiency and performance. Substitution of metallic components with polymeric or composite components within an internal combustion engine presents unique challenges due to the combination of high temperature and formidable forces to which such components are routinely subjected. Development of engine components constructed of polymeric or composite materials that can reliably endure such forces and temperatures without failure is thus an important yet challenging step to continue current trends toward lighter, more efficient vehicles.

A connecting rod is a component of a reciprocating internal combustion engine that connects a piston to a crankshaft, and functions to transfer the reciprocating translational motion of the piston into rotational motion of the crankshaft. As such, a connecting rod in an engine is subjected to considerable heat, intense force, and continuous, multidirectional acceleration of large magnitude. In particular, due to the very large, multidirectional acceleration to which a connecting rod is continuously subject, the connecting rod, like other rapidly moving components, consumes engine output to an extent which belies its relatively small size. For this reason, replacement of metal with plastics and other lightweight components in connecting rods and other rapidly moving parts can be expected to particularly improve engine and vehicle efficiency. SUMMARY

Methods for fabricating composite connecting rods are provided. Also provided are connecting rods composed substantially of lightweight, composite materials while yet possessing functional tensile strength and endurance

In one aspect, a method for fabricating a composite connecting rod is disclosed. The method includes encircling displacement disks of a connecting rod mold with a reinforcing tape and injecting a molding-composite material into the connecting rod mold. The composite material comprises a mixture of organic polymer and reinforcing fiber.

In another aspect, a connecting rod is disclosed. The connecting rod is composed substantially of a moldable composite material. The moldable composite material includes organic polymer and reinforcing fiber. BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects and advantages of the disclosure will become apparent and more readily appreciated from the following description of the embodiments taken in conjunction with the accompanying drawings, of which:

FIG. 1 describes an exemplary method for fabricating a connecting rod composed substantially of composite material;

FIG. 2 is a top plan view of an exemplary connecting rod mold that can be employed for fabricating the connecting rod;

FIG. 3 is a perspective view of the connecting rod mold of FIG. 2 with an exemplary band of reinforcing tape extending around a pair of displacement disks used to form apertures in the connecting rod;

FIG. 4 is a perspective view of the connecting rod mold of FIG. 2 with an exemplary band of reinforcing tape applied to an inner circumference of the mold;

FIG. 5 is a longitudinal cross-sectional view of a connecting rod mold including a movable displacement disk;

FIG. 6 is a longitudinal cross-sectional view of a connecting rod mold including an alternately configured movable displacement disk;

FIG. 7 is a longitudinal cross-sectional view of a connecting rod mold including yet another alternately configured movable displacement disk;

FIG. 8 is a plan view of an exemplary connecting rod composed substantially of composite material and including inner and outer reinforcing tapes; FIG. 9 is a plan view of an alternately configured exemplary connecting rod composed substantially of composite material and including inner and outer reinforcing tapes; and FIG. 10 is a graph of exemplary data from tensile strength tests of a connecting rod of the type illustrated in FIG. 8, fabricated with and without reinforcing tape. DETAILED DESCRIPTION

A method for fabricating a connecting rod, a connecting rod so fabricated, and a connecting rod composed of a composite material are disclosed. As explained in the following description, the method involves injection molding of a composite material. The composite material can include an organic polymer and reinforcing fiber. As used herein, the term "reinforcing fiber" describes a material that can comprise any or a combination of carbon fiber, aramid fiber, or carbon nanotubes. Also disclosed is a mold for forming a composite connecting rod, the mold having a movable/removable displacement disk.

FIG. 1 describes a method 100 for fabricating a connecting rod, with optional steps contained within dashed lines. Method 100 includes a step 102 of injecting a composite material into a connecting rod mold. The composite material used in the injecting step will be referred to hereinafter as "molding-composite material", and can include an organic polymer and reinforcing fiber. The organic polymer will typically be a thermoplastic or thermosetting polymer and can be of any suitable type, including but not limited to, polyetheretherketone (PEEK), polyether sulfone (PES), polyethylenimine (PEI), polyamide- imide (PAI), and polyphenylenesulfide (PPS). In some particular variations, the organic polymer contributing to the molding-composite material will be PEEK. In other variations, the organic polymer comprised by the molding-composite material will be PES.

It is to be noted that the injecting step referenced above, describing an injection molding process, could be replaced with an alternative molding process, such as compression molding. As such, step 102 can be described as a "molding" step rather than an "injecting" step. It has been found, however, that an injection molding process tends to confer an enhanced tensile strength. Without being bound to any particular theory, this is believed to be due to a more effective alignment of reinforcing fibers resulting from the injection process.

In some instances, the molding-composite material will be more than 10% reinforcing fiber by weight and the remainder will include organic polymer. In some instances, the molding- composite material will be 20-50% reinforcing fiber by weight and the remainder will include organic polymer. In some instances, the molding-composite material will be 30- 102 40% reinforcing fiber by weight and the remainder will include organic polymer. In some

103 instances, the molding-composite material will be 30-40% reinforcing fiber by weight and

104 the remainder will be organic polymer. In some instances, the lengths of reinforcing fibers

105 included in the molding-composite material will range predominantly from about 0.1 mm to

106 about 12 mm.

107 An example of a suitable connecting rod mold 200 is illustrated in FIG. 2. The connecting

108 rod mold 200 may include a face 202, and injection port 204, and a recessed cavity 206.

109 The recessed cavity 206 represents the space occupied by the molding-composite material

110 after injection. For purposes of clarity, the connecting rod mold 200 is shown without a

111 cover that attaches to face 202 to enclose the recessed cavity 206. The cover includes

112 various contours for forming a side of the connecting rod. The connecting rod mold 200

113 further includes a cavity perimeter 208 for forming an outer circumference of the

114 connecting rod. The interior cavity perimeter 208 will typically comprise a curved planar

115 surface that can be orthogonal to the face 202. Disposed within the cavity 206 are a first

116 displacement disk 210 and a second displacement disk 212, configured to exclude molding-

117 composite material from volumes which will become apertures in the connecting rod. For

118 example, the first displacement disk 210 forms an aperture in the connecting rod for

119 receiving a crankshaft and the second displacement disk 212 forms and aperture for

120 receiving a piston connecting pin.

121 With reference also to FIGS. 3 and 4, some variations of the method 100 can include an

122 additional step 104 of encircling the first and second displacement disks 210 and 212,

123 respectively, with an inner reinforcing tape 214 and an outer reinforcing tape 216. When

124 the encircling step 104 is employed, it may be desirable that the inner reinforcing tape 214

125 tightly encircle the displacement disks 210, 212, without substantial slack. The same or

126 other variations of the method 100 can include an additional step 106 of layering at least a

127 portion of the perimeter 208 of the connecting rod mold 200 with the outer reinforcing tape

128 216.

129 For clarity, the reinforcing tape 114 used in the encircling step 104 will be referred to

130 hereinafter as an "inner reinforcing tape" and a reinforcing tape 116 used in the layering

131 step 106 will be referred to hereinafter as an "outer reinforcing tape". When either is or

132 both are employed, the encircling and layering steps 104 and 106 will typically precede the

133 injecting step 102. When both are employed, the encircling and layering steps 104 and 106

134 can be performed in any order relative to one another. For example, while FIG. 1 describes 135 the encircling step 104 as preceding the layering step 106, the layering step 106 can

136 alternately precede the encircling step 104.

137 With continued reference to FIGS. 3 and 4, the connecting rod mold 200 is shown

138 subsequent to an encircling step 104 (see FIG. 3) and subsequent to a layering step 106 (see

139 FIG. 4). In FIG. 3, the inner reinforcing tape 214 is shown tightly encircling the first and

140 second displacement disks 210 and 212. In FIG. 4, the outer reinforcing tape 216 is shown

141 layering the cavity perimeter 208 (see FIG. 1) of the connecting rod mold 200.

142 In many instances, an inner reinforcing tape 214, an outer reinforcing tape 216, or both may

143 be configured as a cyclic tape. As used here, the term "cyclic tape" refers to a tape having

144 no longitudinal ends, but instead forming a closed loop such, as a circumference or other

145 cyclic structure. A cyclic tape can be formed, for example, by fixedly adjoining the

146 longitudinal ends of a linear or otherwise longitudinally-ended tape. For increased strength

147 of the cyclic tape, the cyclic tape can be directly fabricated as a closed loop rather than

148 being fabricated as a linear or otherwise longitudinally-ended tape with subsequent joining

149 of the longitudinal ends. A cyclic tape that is formed as such directly, rather than being

150 formed by adjoining longitudinal ends, can be referred to as an "incipiently cyclic tape".

151 When used, the reinforcing tape (for example, inner reinforcing tape 114 and outer

152 reinforcing tape 116) can be composed of any suitable material, such as metal or organic

153 polymer. In many instances, the reinforcing tape will be composed substantially of a

154 composite material, which will be referred to hereinafter as "tape composite material".

155 Tape composite material can include reinforcing fiber and an organic polymer. In some

156 instances, the tape composite material will include a unidirectional carbon fiber structure

157 embedded in an organic polymeric matrix. The organic polymer will typically be a

158 thermoplastic or thermosetting polymer and can be of any suitable type, including but not

159 limited to, polyetheretherketone (PEEK), polyether sulfone (PES), polyethylenimine (PEI),

160 polyamide-imide (PAI), and polyphenylenesulfide (PPS).

161 In some variations, the organic polymer comprised by the tape composite material will be

162 selected so that it has a lower melting point than the melting point of the organic polymer

163 comprising the molding-composite material. Such a selection can cause the tape composite

164 material to be at least partly melted or softened by the heat contained in the injected

165 molding-composite material, thereby improving adhesion or fusion of the reinforcing tape

166 with the molding-composite material. In some particular variations, the organic polymer

167 comprised by the tape composite material will be PPS. 168 In some instances, the tape composite material will be more than 10% reinforcing fiber by

169 weight and the remainder will include organic polymer. In some instances, the tape

170 composite material will be 20-50% reinforcing fiber by weight and the remainder will

171 include organic polymer. In some instances, the tape composite material will be 30-40%

172 reinforcing fiber by weight and the remainder will include organic polymer. In some

173 instances, the tape composite material will be 30-40% reinforcing fiber by weight and the

174 remainder will be organic polymer.

175 The first displacement disk 210 and the second displacement disk 212, or both displacement

176 disks 210 and 212 of the connecting rod mold 200, may be configured to be selectively

177 movable relative to one another to facilitate mounting of the inner reinforcing tape 114 on

178 the first and second displacement disks 210 and 212. For example, with reference to FIG. 5,

179 the second displacement disk 212 may be configured to be moveable relative to the first

180 displacement disk 210 between a tape mounting position 212A and a tape tensioning

181 position 212B. A first distance Dl between a center axis 213 of the first displacement disk

182 210 and a center axis 215 of the second displacement disk 212 when the second

183 displacement disk 212 is arranged in the tape mounting position 212A is less than a second

184 distance D2 when the second displacement disk 212 is arranged in the tape tightening

185 position 212B. The second displacement disk 212 may be infinitely moveable between the

186 tape mounting position 212A and the tape tightening position 212B. The first displacement

187 disk 210 may be similarly configured to be moveable relative to the second displacement

188 disk 212.

189 With continued reference to FIG. 5, to facilitate positioning of the second displacement disk

190 212, a threaded rod 220 may be threadably attached to the second displacement disk 212.

191 The threaded rod 220 being movable (rotatably and reversibly engageable) with a

192 complementarily threaded aperture 222 appropriately positioned in the connecting rod mold

193 200. The threaded rod 220 may rotatably engage an aperture 224 formed in a shank 226 of

194 the second displacement disk 212. A locking pin 228, or another suitable fastener, may be

195 used for securing the threaded rod 220 to the second displacement disk 212. The position of

196 the second displacement disk 212 may be adjusted by rotating the threaded rod 220 to move

197 the second displacement disk between the tape mounting position 212A and the tape

198 tensioning position 212B. The first displacement disk 210 may also employ a similar

199 mechanism for adjusting a position of the first displacement disk 210 relative to the second

200 displacement disk 212. 201 Movability of either or both displacement disks 210 and 212 can facilitate deployment of

202 the inner reinforcing tape 214 that encircles the displacement disks 210 and 212 tightly. For

203 example, the inner reinforcing tape 214 may be positioned in the mold 200 by first moving

204 the second displacement disk 212 to the tape mounting position 212A (see, for example,

205 step 101 of FIG. 1) that allows for relatively easy mounting of the inner reinforcing tape

206 214 to the first displacement disk 210 and the second displacement disk 212. Slack in the

207 inner reinforcing tape 214 may be substantially eliminated by rotating the threaded rod 220

208 to move the second displacement disk 212 from the tape mounting position 212A to the tape

209 tensioning position 212B (see, for example, step 103 of FIG. 1), thereby increasing the

210 distance between the two first and second displacement disks 210 and 212.

211 FIG. 6 illustrates an alternately configured adjusting mechanism 229 for controlling a

212 position of the second displacement disk 212 relative to the first displacement disk 210.

213 The adjusting mechanism 229 may include a threaded rod 230 that threadably engages a

214 threaded aperture 232 formed in the shank 226 of the second displacement disk 212. The

215 threaded rod 230 rotatable engages an aperture 234 formed in the mold 200. A locking tab

216 236 may be used to secure the threaded rod 230 to the mold 200. A bolt 238, or another

217 fastener, may be used to secure the lacking tab 236 to the mold 200. The position of the

218 second displacement disk 212 relative to the first displacement disk 210 may be adjusted by

219 rotating the threaded rod 230 to move the second displacement disk 212 between the tape

220 mounting position 212A and the tape tensioning position 212B. The first displacement disk

221 210 may also employ a similar mechanism for adjusting a position of the first displacement

222 disk 210 relative to the second displacement disk 212.

223 With reference to FIG. 7, in yet another alternative example of a movable displacement disk

224 210 or 212, the displacement disk 210 or 212 can be slideably movable within mold 200.

225 FIG. 7 shows a longitudinal, side cross-sectional view of the connecting rod mold 200 of

226 the type shown in FIG. 2. In the example of FIG. 7, the second displacement disk 212 is

227 slideably repositionable between the tape mounting position 212A and the tape tensioning

228 position 212B. When in the tape mounting position 212A, the distance Dl between the first

229 and second displacement disks 210, 212 is smaller than the distance D2 when the second

230 displacement disk 212 is positioned in the tape tensioning position 212B, thereby

231 facilitating loose encircling of the two displacement disks 210, 212 with the inner

232 reinforcing tape 214. Subsequent movement of the second displacement disk 212 to the

233 tape tensioning position 212B causes tight encirclement of the two displacement disks 210,

234 212 by the inner reinforcing tape 214. Also in the example of FIG. 7, movement of the 235 second displacement disk 212 may be facilitated by a tri-hinged exocentric arm 240,

236 accessible from a back side 242 of the mold 200. As will be obvious to one skilled in the

237 art, other means of achieving movability of the first displacement disk 210, the second

238 displacement disk 212, or both are possible.

239 With reference to FIG. 8, disclosed is a connecting rod 300 composed substantially of a

240 moldable composite material. The moldable composite material includes reinforcing fiber

241 in admixture with a thermoplastic or thermosetting organic polymer. As above, the term

242 "reinforcing fiber" as used herein can refer to any or a combination of carbon fiber, aramid

243 fiber, or carbon nanotubes. The connecting rod 300 is operable to connect and transfer

244 motion from a piston pin to a crankshaft in an internal combustion engine.

245 With continued reference to FIG. 8, an example of a connecting rod 300 includes a shaft

246 engagement element 302 defining an aperture 305 operable to engage a vehicle crankshaft,

247 and a piston engagement element 304 defining and aperture 305 operable to engage a

248 vehicle piston pin. The connecting rod 300 additionally includes a connecting arm 306,

249 traversing the distance between the shaft engagement element 302 and the piston

250 engagement element 304.

251 The organic polymer comprised by the moldable composite material will typically be a

252 thermoplastic or thermosetting polymer and can be of any suitable type, including but not

253 limited to, polyetheretherketone (PEEK), polyether sulfone (PES), polyethylenimine (PEI),

254 polyamide-imide (PAI), and polyphenylenesulfide (PPS). In some particular variations, the

255 organic polymer comprised by the moldable composite material will be PEEK. In some

256 particular variations, the organic polymer comprised by the moldable composite material

257 will be PES.

258 In some instances, the moldable composite material will be more than 10% reinforcing fiber

259 by weight and the remainder will include organic polymer. In some instances, the moldable

260 composite material will be 20-50% reinforcing fiber by weight and the remainder will

261 include organic polymer. In some instances, the moldable composite material will be 30-

262 40% reinforcing fiber by weight and the remainder will include organic polymer. In some

263 instances, the moldable composite material will be 30-40% reinforcing fiber by weight and

264 the remainder will be organic polymer.

265 The connecting rod 300 can optionally include an inner reinforcing tape 308. When used,

266 the inner reinforcing tape 308 simultaneously encircles at least a portion of the inner

267 circumference of the shaft engagement element 302 and at least a portion of the inner

268 circumference of the piston engagement element 304 of the connecting rod 300. When 269 used, the inner reinforcing tape 308 is incorporated into the connecting rod 300 and is at

270 least partially surrounded by the moldable composite material. The inner reinforcing tape

271 308 at least partially defines the aperture 303 in the shaft engagement element 302 for

272 receiving the crankshaft and the aperture 305 in the piston engagement element 304 for

273 receiving the piston pin.

274 The connecting rod 300 can also optionally include an outer reinforcing tape 310. When

275 used, the outer reinforcing tape 310 permanently contacts outer edges 312 of the moldable

276 composite material of connecting rod 300 and encircles the periphery of connecting rod

277 300. Permanence of contact between outer edges 312 of the moldable composite material

278 and the outer reinforcing tape 310 can be achieved by the moldable composite material

279 having been cured in contact with or in partial surrounding of the outer reinforcing tape 310.

280 Permanence of contact can also be achieved by the outer reinforcing tape 310 having a

281 melting temperature sufficiently low that it is partially heat softened during curing of the

282 moldable composite material.

283 For brevity, the phrase "a reinforcing tape" will be used hereinafter to refer generically to

284 either the inner reinforcing tape 308 or the outer reinforcing tape 310, or to refer to the inner

285 reinforcing tape 308 and the outer reinforcing tape 310 as a group. As such, a reinforcing

286 tape can be composed of any suitable material, such as metal or organic polymer. In many

287 instances, a reinforcing tape will be composed substantially of a composite material which

288 will be referred to hereinafter as "reinforcement composite material". Reinforcement

289 composite material can include reinforcing fiber and an organic polymer. In some

290 instances, the tape composite material will include a unidirectional reinforcing fiber

291 structure in an organic polymeric matrix.

292 The organic polymer will typically be a thermoplastic or thermosetting polymer and can be

293 of any suitable type, including but not limited to, polyetheretherketone (PEEK), polyether

294 sulfone (PES), polyethylenimine (PEI), polyamide-imide (PAI), and polyphenylenesulfide

295 (PPS). In some variations, the organic polymer comprised by the reinforcement composite

296 material will be selected so that it has a lower melting point than that of the organic polymer

297 comprising the moldable composite material. In some particular variations, the organic

298 polymer comprised by the reinforcement composite material will be PPS.

299 In some instances, the reinforcement composite material will be more than 10% reinforcing

300 fiber by weight and the remainder will include organic polymer. In some instances, the

301 reinforcement composite material will be 20-50% reinforcing fiber by weight and the

302 remainder will include organic polymer. In some instances, the reinforcement composite 303 material will be 30-40% reinforcing fiber by weight and the remainder will include organic

304 polymer. In some instances, the reinforcement composite material will be 30-40%

305 reinforcing fiber by weight and the remainder will be organic polymer.

306 While the shaft engagement element 302 and the piston engagement element 304 are each

307 shown as a ring, or circular structure in FIG. 8, a ring structure is not specifically required.

308 For example, the shaft engagement element 302 could be an open-ended harness. An

309 alternative example a connecting rod is shown in FIG. 9 as a two-piece connecting rod 400.

310 In the two-piece connecting rod 400 of FIG. 9, a shaft engagement element 402 includes an

311 open harness 402A for easy engagement with a crankshaft. The shaft engagement element

312 402 also includes an optional capping member 402B that can be secured to the open harness

313 402 A after engagement with the crankshaft, for example, using fasteners 404. The two-

314 piece connecting rod 400 of FIG. 9 may include an outer reinforcement tape 410 that is not

315 cyclic and that is contained only within the larger piece of the two-piece structure. The

316 example of FIG. 9 also illustrates a non-cyclic inner reinforcing tape 412. It may, in some

317 instances, be preferable to exclude the non-cyclic inner reinforcing tape 412 from a two-

318 piece design of this variety.

319 It should be noted that the method 100 for fabricating a connecting rod is applicable to the

320 two-piece connecting rod 400, for example, of the type illustrated in FIG. 9. In such a

321 situation, the optional step 104 of encircling the first and second displacement disks with a

322 reinforcing tape can be modified to correspond with the configuration of the inner

323 reinforcing tape 412 in FIG. 9. As such, in the method 100, as applied to fabrication of a

324 two-piece connecting rod, the first displacement disk 210 is semicircular, corresponding to

325 open harness 402A, while the second displacement disk 212 is circular. Step 104 of method

326 100 would then involve wrapping a reinforcing tape in a pseudo-parabolic shape from one

327 side of the first displacement disk 210, which is semicircular, around the second

328 displacement disk 212, and to the opposite side of the first displacement disk 210.

329 While the methods and connecting rods disclosed herein have been described as being

330 particularly applicable to automotive vehicles and aeronautical vehicles, it should be

331 appreciated that they are applicable to any engine, motor, or device in which a connecting

332 rod is employed to transfer the reciprocating motion of a piston to the rotary motion of a

333 connecting rod.

334 Various aspects of the present disclosure are further illustrated with respect to the following

335 Examples. It is to be understood that these Examples are provided to illustrate specific 336 configurations of the present disclosure and should not be construed as limiting the scope of

337 the present disclosure in or to any particular aspect.

338

339 Example 1. Fabrication of carbon fiber/PEEK connecting rod.

340 A connecting rod mold of the type shown in FIG. 2 is closed and hot injected with a

341 composite material. The composite material consists of -30% carbon fiber ~0.1-12 mm

342 length, 70% PEEK. After curing, the composite connecting rod is removed from the mold.

343 The resulting connecting rod is referred to below as a "no-tape" connecting rod.

344 Separately, the two pins or displacement disks in a connecting rod mold of the type shown

345 in FIG. 2 are tightly encircled with a unidirectional cyclic tape of carbon fiber/PPS. The

346 periphery of the connecting rod mold cavity space is layered with a unidirectional cyclic

347 tape of carbon fiber/PPS. In both cases, carbon fiber content of the cyclic tape is about

348 40%, the remainder PPS, and the tape is cyclized by adhesively affixing the ends of a linear

349 tape.

350 The mold is closed and hot injected with a composite material. The composite material

351 consists of -30% carbon fiber -0.1-12 mm length, 70% PEEK. After curing, the composite

352 connecting rod is removed from the mold. The resulting connecting rod is referred to below

353 as a "2-tape" connecting rod.

354

355 Example 2. Tensile strength testing of carbon fiber/PEEK connecting rod.

356 The no-tape and the 2-tape connecting rods, whose fabrication is described above in

357 Example 1, were each subjected to a tensile strength test. In the test, the piston engagement

358 element and the shaft engagement element of the connecting rod being tested were engaged

359 to a force application/displacement measurement instrument. The instrument exerted a

360 continuously increasing tensile force, i.e. the piston engagement element and shaft

361 engagement element were loaded in opposite directions, and displacement, i.e. stretch or

362 other deformation, of the connecting rod was measured. The results of the test are shown in

363 FIG. 10. The results for the 2-tape connecting rod are depicted as a solid line, while the

364 results for the no-tape connecting rod are depicted as a dotted line. In each case, the

365 connecting rod progressively displaced with increasing force application until part failure.

366 Part failure, i.e. physical fracture, is indicated by the precipitous decline in force after a

367 continuous, gradual force increase, for each data trace. As shown, the no-tape connecting

368 rod failed at an applied force of -21.5 kN, while the 2-tape connecting rod failed at an

369 applied force of -26.1 kN. These results demonstrate the improvement in tensile strength 370 conferred by the reinforcing tapes. The maximum force reached prior to failure is referred

371 to as the tensile failure point.

372 The foregoing description relates to what are presently considered to be the most practical

373 embodiments. It is to be understood, however, that the disclosure is not to be limited to

374 these embodiments but, on the contrary, is intended to cover various modifications and

375 equivalent arrangements included within the spirit and scope of the appended claims, which

376 scope is to be accorded the broadest interpretation so as to encompass all such modifications

377 and equivalent structures as is permitted under the law.

378