TWO-PIECE WHEEL FABRICATION WITH ROLLED CONNECTION

BACKGROUND OF THE INVENTION' This invention relates in geneial to vehicle wheels and m particulai to a method for fabπcating two piece wheels having a wheel nm rolled onto to a sepaiately formed wheel disc to form a mechanical connection therebetween io It is known in the art to fabricate a vehicle wheel by attaching a wheel nm to a sεpaιatel formed wheel disc Typically, the wheel nm is i oiled fiom steel strip stock and the disc is stamped from steel sheet stock The run is welded to the disc to form the wheel Such a wheel is shown in U S Patent No 5,257, 455 to Iwatsuki Alternately, the wheel nm can be rolled from steel and the wheel l ^ disc cast oi foiged fiom a light weight metal, such as aluminum, titanium or magnesium, or an alloy of a light weight metal Because the metals forming the nm and disc aie diffeient, a ferrous w eld anchoi is usually attached to wheel dioC T he w heel nm is welded to the w eld anchoi to assure that a good weld is formed between the nm and disc Such a wheel is descnbed in U S Patent No _\ 506.3 1 1 to Nobach and is commonly refeπed to a bimetal wheel A bimetal wheel combmes the economy, flexibility and strength of a steel nm with the pleasing ornamental appeal ance of three dimensional contours formed in a cast ci foiged w heel disc

1 o enhance the appeal ance of a t o piece wheel, it is known to attach a

2- full face wheel disc which includes the outboard tne retaining flange to a partial wheel nm to form a full face bimetal wheel When a tne is mounted upon a full face w heel the joint between the wheel disc and wheel nm is completely hidden and onlv the wheel disc is visible A decorative finish is often applied to the

face of the wheel disc to further enhance the appeal ance of the wheel Examples of typical decoiative finishes include metal plating, such as chromium plating _, clear coatings and paint

Referring now to the drawings, there is shown in Fig 1 a fiagmentary ι sectional view of a typical prior art bimetal full face wheel 10 The wheel 10 is descnbed in the Nobach patent listed above and includes a full face wheel disc 1 1 formed fiom a light weight metal oi light weight metal alloy by a conventional piocess, such as gravity, low pressure or die casting The full face wheel disc 1 1 includes a central wheel hub 12 which is supported by a plurality lo of wheel spokes 13 (one shown) within an annulai sidewall 14 An outboard tire bead retaining flange 15 extends in a radial outward dn ection from the sidewall 14 The wheel disc 1 1 also includes a ring-shaped weld anchor 16 formed from a feπous material, such as steel, which is partially embedded in the wheel disc sidewall 14 A portion of the weld anchor 16 is exposed to form a welding l -i surface 17 The sidewall 14 furthei includes a cylindncalK -shaped collar 18 which extends axially from the inboard side of the flange 15 The collar 18 extends l adialK ovei a portion of the weld anchor 16 to secure the weld anchor 16 to the wheel disc 1 1

A conventional partial wheel nm 20 is attached to the inboard side of the

20 wheel disc 1 1 The wheel nm 20 is formed from steel strip stock with conventional nm roll forming machinery The wheel rim 20 includes an inboard end 2 1 which terminates in a conventional inboard tire bead retaining flange 22 An inboard tire bead seat 23 and inboaid safety bead 23 A are also formed on the inboard end 2 1 of the wheel nm 20 A leg portion 24 extends in an outward

2ι axial direction fiom the inboaid safety bead 23 A A deepwell 25 is formed in the w heel nm 20 adjacent to the leg portion 24 The wheel nm 20 also includes a cyhndi ically-shaped outboaid end 26 which is adjacent to the deepwell 25 The outboai d w heel nm end 26 includes an outboai d tn e bead seat 27 and

outboard safety bead 27A The outboaid rim end 26 extends er the wheel disc collar 18 and into contact with the w elding surface 17 of the w eld anchor 15 The outboard nm end 26 and the wheel disc collai 18 are sized to form a clearance fit theiebetween, allowing the wheel nm 20 to be rotated lelatu e to the ι wheel disc 1 1

AL continuous circumfeiential air-tight weld 28 is formed between the wheel nm 20 and the weld anchor 16 Typically, a conventional friction or inertial welding pi ocess is used to form the weld 28 Dunng the w elding piocess, the wheel disc 1 1 is held stationary while the wheel nm 20 is rotated o with the outboard nm end 23 pressed against the weld anchor 16 The heat geneiated by faction partially melts the outboard wheel nm end 26 and the adjacent portion of the weld anchoi 16 to form the weld 28

An alternate structure for the weld anchoi is disclosed in U S Patent No 5,421 642 to Archibald wheie the weld anchor includes an annular collai which is recen ed by the outboard end of a partial wheel rim The weld anchor collai positions the wheel nm on the wheel disc

While the wheel disc is typically welded to the wheel nm it is also known to heat shrink the wheel nm onto the wheel disc as shown in U S Patent No 4 363 347 to Baumgartnei and Euiopean Patent Application No 0 096 399 0 to Stahlschmidt &. Malwurm GmbH & Co KG The U S Patent discloses wheel structures having either cylindrical or conical shnnkage surfaces The U S Patent also discloses optional cutting oi rolling of thieads on the cy lindrical shnnkage surfaces to allow the disc to be threadedly attached to the wheel nm The European Patent Application discloses conical shnnkage surfaces The - Eui opean Patent Application furthei discloses optional forming of cleats and coπesponding es, which leceive the cleats, on the shrinkage surfaces

SUMMARY OF THE INVENTION This invention relates to a process for fabricating a two piece vehicle wheel bv rolhnc a wheel rim onto a wheel disc to foπn an interlockin ^g bead and groove which mechanically secure the wheel rim to the wheel disc As described above, two piece vehicle wheels typically include a wheel disc welded to a wheel nm which is formed by a rolling or spinning operation The heat of welding has been know to warp the wheel disc and/or the wheel nm. Also, a layer of oxidized metal can form on the welding surface of the wheel disc and on the adjoining surface of the partial wheel nm This layer of oxidized metal can prevent formation of a satisfactory weld between the wheel disc and wheel nm When a partial wheel rim is welded to a full face wheel disc, oxidation on the welding surface can prevent formation of an air-tight weld between the wheel rim and the wheel disc. As a result, tire inflation air may leak from a tire mounted upon the assembled wheel. Additional metal oxidization can occur if the wheel disc is subjected to a plating process to form a decorative layer on the visible portion of the wheel disc

The heat generated by the welding operation used to attach the wheel nm to the w heel disc can damage the decoi ative finish of the w heel disc If the wheel finish is flawed, the entire wheel must be scrapped. It is known to delay applying the decorative finish to the wheel disc until after the wheel is welded, however, this requires a more complex manufacturing process. Thus, it would be desnable to fabricate two piece wheels without a welding operation This would eliminate the potential of heat damage to the wheel, allow application of the decorative finish to the wheel disc befoie assembly of the wheel and reduce the scrap rate for assembled wheels.

The piesent invention contemplates a piocess for fabneating a vehicle wheel which includes pioviding an annulai wheel rim having an outboard end which defines a cylindrical innei surface A cncular wheel disc having a central

hub connected a plurality of wheel spokes to an armulai -shaped sidewall also is prouded The heel disc sidew all includes a cylindrical outer surface which has at least one bead or formed thereon The wheel nm is positioned on the wheel disc w ith a portion of the wheel nm outboard end extending axially

^ over a portion of the wheel disc sidewall and with the cylindrical inner surface of the wheel nm adjacent to the cylindrical outei surface of the wheel disc sidewall The outboaid wheel nm end is mechanically rolled onto the wheel nm, forcing the ov εilappmg portion of the wheel nm onto the cylindrical outer surface of the wheel disc sidewall The rolling opeiation forms a groove or bead on the

10 cyhndπcal inner surface of the wheel nm The groove receives the coπesponding bead to mechanically secure the wheel nm to the wheel disc The inv ention furthei contemplates that the bead and gioove can be continuous and circumferential Additionally, the invention can be piacticed with a plurality of beads oi grooves formed on the wheel disc Accordingly a

H plurality' of complementary grooves or beads will be formed on the innei nm surface during the rolling operation The invention also contemplates that the plulity of beads define parallel planes

A resilient material can be applied to the wheel nm or the wheel disc before positioning the nm over the disc As the wheel nm is rolled onto the

20 wheel disc, the lesilient mateπal is compressed to form an air-tight seal between the wheel nm and the wheel disc An adhesive can be included in the resilient matenal to furthei secure the wheel nm to the wheel disc Alternately, the wheel nm can be brazed welded or soldered to the wheel disc

Optionally the outboard end of the wheel nm can be heated to radially

2τ txpand the inside diameter theieof sufficiently to fit over beads formed on the wheel disc and to make the nm end moie pliable foi the rolling operation Aftei rolling the wheel nm onto the wheel disc, the wheel nm is shrink fitted onto the wheel disc as the wheel assembly cools

Vanous objects and advantages of this invention w ill become appaient to those skilled in the art fiom the following detailed description of the preferred embodiment, when read in light of the accompanying draw ings

BRJEF DESCRIPTION OF THE DRAWINGS

Fig 1 is a fiagmentary sectional view of a prior art t o piece wheel Fig 2 is a fragmentary sectional view of a two piece wheel fabricated in accordance with the invention

Fig 3 is a flow chart for fabπcating the wheel shown in Fig 2 Fig 4 lllustiates the rolling operation included in the flow chart shown in

Fig 5 lllustiates an alternate iolhng opei ation which can be included in the flow chart shown in Fig 3

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Refeπ mg again to the diawings, there is lllustiated in Fig 2 a fragmentary sectional view of a two piece wheel 30 fabπcated in accordance w ith the invention In the prefeπed embodiment, the wheel 30 is a bimetal wheel which includes a full face wheel disc 31 formed fi om a light weight metal, such as aluminum titanium oi magnesium, or an alloy of a light weight metal, by a conventional process, such as casting or foi g g While the prefeπed embodiment includes a wheel disc formed fi om a light weight metal, it will be appreciated that the wheel disc also can be stamped or forged from steel or stainless steel or formed from a plastic Additionally, the wheel disc can be cast from stainless steel with the Hitchner process In the piefeπed embodiment, the wheel disc 3 1 includes a decoi ative surface finish (not shown) Foi example, a layei of plating, such as chrome plating, can be deposited upon a portion of the

wheel disc surface, 01 a layer of paint or a clear coating can be applied to the wheel disc 3 1

While the pi efeπed embodiment is descnbed below for a bimetal wheel, it will be appreciated that the invention also can be practiced on a wheel having a 5 disc and nm formed from the same metal diffeient alloys of the same metal oi plastics For example, a wheel nm formed fiom a first alloy of aluminum can be attached to a wheel disc formed fiom a second alloy of aluminum, where the second alloy of aluminum is diffeient from the first alloy of aluminum Similai K . the inv ention also contemplates attaching a plastic wheel nm to a io plastic w heel disc to form a wheel

In the pieferred embodiment shown in Fig 2, the wheel disc 3 1 includes an annular-shaped sidewall 32 An outboard tne bead retaining flange 33 extends in an outw aid ladial direction from the sidewall 32 The inboard portion of the sidewall 32 has a leduced outer ladius which forms a shoulder 34 and an

] 5 annulai collai 35 The collai 35 has a geneially cvlindncal outer surface which extends axiallv from the shoulder 34 toward the inboaid end of the wheel 30

A pluiahty of paiallel continuous cncumferential beads, tw o of which, 36 and 37, are show n in Fig 2, aie formed on the outei surface of the collar 35 The beads 36 and 37 define parallel planes which are spaced apart axially and are

20 perpendicular to the axis of the wheel 30 While two beads 36 and 37 are show n in Fig 2. the inv ention also can be practiced with moie than t o beads or with a single bead formed on the outer surface of the collar 35

A conventional wheel nm 40, which m the preferred embodiment is a partial wheel nm formed from steel is attached to the wheel disc 3 1 The wheel

2 ^; nm 40 can be formed from steel snip stock with conventional nm loll forming machinery It w ill be appieciated that the invention also can be piacticed with a wheel nm formed with a casting oi forging piocess Additionally, the wheel nm can be formed from a light w eight metal, such as aluminum titanium or

magnesium an alloy of a light weight metal, a plastic or stainless steel The wheel nm 40 can optionally include a decorative finish (not shown) For example, a layei of plating, such as chrome plating, can be deposited upon a portion of the wheel nm surface, or a layer of paint or a clear coating can be applied to the wheel nm 40

The wheel nm 40 has a c lindncal outboaid end 41 which includes a portion of an outboard tire bead seat 42 For leasons which w ill be explained below, the nm end 41 has a thinner cross section than the remainder of the wheel nm 40 Generally, the thickness of the nm end 41 is a function of the ductility of the mateπal forming the wheel nm 40 The outboaid nm end 41 extends ovei the wheel disc collar 35 and contacts the wheel disc shoulder 34

As will be explained below, the nm end 41 is rolled onto the w heel disc collar 35 During the i oiling process, the nm end 41 is worked to conform to the shape of the collar 35 During the l olling piocess, the nm end is deformed over the collar beads 36 and 37 to form a pan of grooves 43 and 44 on the inside surface of the nm end 41 Accoidingly, the grooves 43 and 44 are contained in parallel planes which are spaced apart axiallv and coincide w ith the planes of the beads 36 and 37 Also, the gi ooves 43 and 44 have ci oss sectional shapes which aie complementary to the cioss sectional shape of the corresponding beads 36 and 37 Because the nm end 41 is relatively thin, a second pair of beads 45 and 46 are formed on the outer surface of the nm end 41 opposite from the grooves 43 and 44 dunng the lolling operation

As shown in Fig 2, the giooves 43 and 44 receive the wheel disc beads

36 and 37 and coopeiate therewith to pi event axial movement of the wheel nm 40 relative to the wheel disc 3 1 Thus the grooves 43 and 44 and beads 36 and

37 mechanically lock the wheel nm 40 onto the wheel disc 3 1

A ciicumfeiential an -tight seal 50 is disposed between the wheel disc collai 35 and the wheel nm end 41 to prevent leakage of tire inflation air through

the joint formed therebetween The seal 50 is shown extending axially from the sidew all shoulder 34 to the outboaid bead 36 formed on the collar 35 Howevei the seal 50 also may be disposed between the outboaid and inboard beads 36 and 3 ⁷ , between the mboaid bead 37 and the inboaid end of the collar 35 oi over the 5 entire surface of the collai 35 In the prefeπed embodiment the seal 50 is formed fiom a lesilient matenal Also in the piefeπed embodiment, the resilient matenal forming the seal 50 includes an adhesive, such as an epoxy, acrylic or bisphenol Such adhesives have high sheai strength and toughness to resist impact and riser sti esses The adhesive functions to bond, and thereby further o secure the wheel disc 3 1 to the wheel nm 40

The piefeπed embodiment has been illustrated m Fig 2 with the beads 36 and 37 formed on the wheel disc collai 35 and the conespondmg grooves 43 and 44 formed in the wheel nm end 41 by the rolling operation As will be described below the invention also can be practiced w ith a plurality of parallel continuous cucumferential giooves formed in the wheel disc collar with the wheel nm end rolled into the grooves to form complementary beads on the innei surface of the wheel nm end 41 (not shown AdditionalK while the beads 36 and 37 and gioov es 43 and 44 have been shown in Fig 2 having generallv rounded cross- sectional shapes, the invention also can be practiced with beads and grooves 0 having othei conespondmg cioss-sectional shapes, such as, square, rectangular, elliptical, trapezoidal or triangular

It will be appieciated that while the m end 41 has been illustrated as being thmnei than the rest of the wheel nm 40, if the metal forming the nm 40 is ductile enough to be lolled onto the wheel disc collar, a thicker nm end can be _-. used Also, as will be described below, the i oiling of the nm end 41 may invol e either hot oi cold woiking of the metal

The invention contemplates a piocess for fabricating the wheel 30 shown m Fig 2 The piocess is illustrated in the flow chart shown in Fig 3 A wheel

disc which has an annulai collar is provided in functional block 60 In the prefeπed embodiment, a full face wheel disc is used with the collar extending axially from the inboard smiace thereof However, it will be appreciated that the invention also can be practiced with a wheel disc or spider w hich are disposed withm a full wheel nm A plui ahty of beads oi gi ooves ai e foπned on the outer surface of the wheel disc collar

A decorativ e finish is applied to a portion of the w heel disc surface in functional block 61 , howe er, this step is optional The finish can be a layer of paint oi cleai coat Additionally, a decoi ativ e finish of plating can be deposited onto a portion of the wheel disc surface Such layers of plating are typically sealed with a layer of clear coat

A resilient sealing material, which in the pi efeπed embodiment includes an adhesive, is applied to the collar in functional block 62 Alternately, the resilient sealing material and adhesive can be applied to the mnei surface of the vvheel nm outboaid end

In functional block 63 a wheel nm is provided The w heel nm is formed by a conventional pi ocess such as casting forging oi i oiling In the prefeπed embodiment, a partial wheel nm having a cv lindncal outboard end which is r elatively thm and does not include grooves oi beads is used A decorative finish can be applied to a portion of the wheel nm surface in functional block 64, how e er, this step is optional The decorative finish can be a layer of paint or cleai coat Additionally, a decoiative finish of plating can be deposited onto a portion of the wheel nm surface Such layers of plating ai e ty pically sealed with a layer of cleai coat The outboai d end of the wheel nm is heated in functional block 65, however, as will be explained below , this step is optional For a metal wheel nm, the heating l dially expands the nm end increasing the inside diametei thereof sufficiently to fit eι anv beads formed on the wheel disc collai With

respect to a plastic wheel nm, heating makes the nm end pliable The outboard end of the wheel nm is heated by a conventional means, such as electnc induction, electnc resistance 01 inflated heating elements or by placing the wheel nm in a gas-fned 01 electric lesistance furnace In block 66, the wheel nm end is positioned over the wheel disc collar to form a wheel assembly In the prefeπed embodiment the outboard end of the partial vvheel nm is positioned over the collar extending fiom the inboaid surface of the full face wheel disc with the nm concentric with the wheel disc and the inboard tne retaining flange parallel to the outboaid tire letaining flange The wheel nm and disc can optionally be placed in a fixture (not shown) to assuie the pioper alignment therebetween Alternately , the vvheel disc oi spider is positioned with a full wheel nm with the wheel disc oi spider perpendiculai to the wheel nm axis

The outboard end of the wheel nm is rolled onto the wheel disc collar in functional block 67 In the wheel nm has been heated the rolling opeiation is completed before the wheel nm end has cooled Details of the rolling process ai e illustrated in Figs ^d and 5 Fig 4 shows a portion of a full face wheel disc 70 hav ing a plurality of parallel continuous circumfeiential beads 71 formed on an axially extending collai 72 A resilient sealing material 73 is earned on a portion of the outer surface of the wheel disc collar 72 Also shown in Fig 4 is a partial wheel nm 75 which has a cvlindncal outboaid end 76 extending over the wheel disc collar 72 As described above, the nm end 76 is not formed w ith grooves conespondmg to the beads 71, since the giooves will be formed during the rolling opeiation described below If the wheel nm 75 is foimed hav ing an outboaid end diameter sufficiently laige to cleai the wheel disc beads 71 when the wheel nm end 76 is assembled onto the wheel disc collar 72, the wheel nm end 76 does not have to be heated, as shown in functional block 75

A conventional roll forming machine (not shown) is used to roll the wheel nm end 76 onto the w heel disc collai 72 The rolling machine has a plurality of rollers, one of which, 77 is shown in Fig 4 The roller 77 has circumferential grooves 78 formed theie which correspond to the w heel disc beads 71 The - wheel assembh is rotated while the lollei 77 is pressed against the surface of the wheel nm end 76, as shown by the arrow in Fig 4 The rollei 77 forms the wheel nm end 76 over the collar 72 to coπ espond to the surface shape thereof The rollei grooves 78 press a portion of the nm end 76 over the wheel disc beads 71 to form conespondmg grooves 79 therein As described above, the giooves io 79 formed in the vvheel nm end 76 coopeiate with the wheel disc beads 71 to mechamcallv lock the wheel nm 75 on the w heel disc collai 72 The roller 77 also presses the w heel nm end 76 against the surface of the w heel disc collar 72, theiebv compiessmg the resilient material and adhesive 73 to form an an-tight seal between the wheel nm and the vvheel disc

15 An alternate rolling process is shown in Fig 5 vvheie a wheel disc 80 has a pluiahty of parallel continuous circumfeiential gi ooves 81 formed in an axially extending collar S2 A l esilient sealing material and adhesiv e 83 is earned on the collar 82 As described above an outboard end 85 of a partial wheel nm 86 is positioned ovei the wheel disc collai 82 The vvheel nm 86 does not have

20 beads formed on the outboaid end 85 since the beads will be formed during a rolling operation Accordingly, it may not be necessary to heat the wheel nm end, as indicated in functional block 85 in Fig 3, before assembling the vvheel Certain matenals however, will lequire heating before the rolling operation Foi example the outboaid end of a plastic wheel nm would be heated to mciease the

^ ductility' of the plastic A conventional i oiling machine (not shown) rolls the wheel nm end 85 onto the w heel disc collai 82 The i oiling machine includes a pluiahty' ol tollei s, one of which, 87, is shown The roller 87 has a plurality of ciicumfei ential beads 88 formed thei eon which coπespond to the grooves 8 1

11

formed m the wheel disc collar 82 The roller 87 forms the w heel nm end 85 over the collai 82 to coπespond to the surface shape theieof The lollei beads 88 press a portion of the nm end 85 into the wheel disc groov es 81 to form conespondmg beads 89 therein As described above, the beads 89 formed in the vvheel nm end 85 coopeiate with the wheel disc grooves 81 to mechanically lock the wheel nm 86 on the vvheel disc collar 82

If the wheel nm was heated in functional block 65 the assembled wheel is cooled in functional block 90 As shown in Fig 3, cooling is an optional step Ho evei, follow ing the rolling operation the adhesive contained m the resilient matenal 73 is cuied to furthei secuie the wheel nm to the wheel disc

While the prefeπed embodiment of the lolling piocess has been illustiated in Figs 4 and 5 with two beads cooperating with two grooves to mechanically lock the wheel nm onto the vvheel disc, it will be appreciated that the process shown Fig 3 can be applied to wheels having moie than tw o beads and grooves oi to wheels having a single bead and groove Additionally, while the process was descnbed with an adhesi e further securing the wheel nm to the wheel disc, it is also possible to eld, braze or soldei the wheel nm the wheel disc follo ing the I oiling operation When the wheel nm is w elded to the wheel disc, the lesilient sealing matenal is omitted and a continuous circumferential air-tight weld is formed between the wheel nm and the wheel disc If the wheel nm is brazed or soldeied to the vvheel disc, brazing filler metal or solder is applied to the wheel disc or nm instead of the iesihent sealing mateπal Furthermore, while the piefeπed embodiment has been illustrated in Figs 2, 4 and 5 with a full face w heel disc attached to a partial vvheel nm, the process also can be used to attach a wheel disc or spider to a full wheel nm as has been descnbed above In such a case an an -tight seal is not needed between the wheel disc and the wheel nm

As described above, in the prefeπed embodiment, the w heel disc provided in functional block 60 can receive a decorative finish in functional block 61 , such as painting or plating, before being attached to the wheel nm Similarly, the wheel nm provided in functional block 63 can receive a decorative finish in functional block 64 In prioi an wheel fabrication processes w hich include welding vvheel discs having plated oi painted finishes, such decorative finishes could be damaged by the heat generated when the vvheel rim is w elded to the wheel disc. Accordingly, in such prior art processes, the painting or plating is typically applied to the wheel after welding which requires a more complex manufactuπng process. Thus, the present invention simplifies the manufacture of two piece wheels because the decoiative finishes can be applied to the wheel components before they are assembled Because the coating is not damaged during assembly, coπosion protection provided thereby is maintained

Additionally, in the prior art processes, if there is a blemish in the decorative finish, the entne wheel has to be scrapped. With the present invention, any wheel discs or πms which have unsatisfactory finishes can be r ejected befoie assembly of the w heel This eliminates needless scraping of unblemished components and reduces the total sci ap l ate Also oxidation of the wheel disc and rim surfaces does not affect the air-tight seal formed therebetween

Use of an adhesive instead of welding to bond together the wheel components eliminates welding heat and fumes during fabrication of the wheel This simplifies the vvheel manufactuπng facility since heat and fume removal equipment are not required It will be appreciated that, while the prefeπed embodiment has been descnbed as having a i esihent matenal which includes an adhesiv e disposed between the wheel nm and wheel disc, the invention also can be practiced with onlv an adhesive disposed between the wheel rim and wheel disc

In accordance with the pi owsions of the patent statutes the principle and mode of operation of this invention have been explained and illustiated in its prefeπed embodiment Howevei, it must be understood that this inv ention mav be practiced otherwise than as specifically explained and illustrated without departing fi om its spint or scope