Note: Descriptions are shown in the official language in which they were submitted.
~59~39
l~ls invention relates to a n~ethod and apparatus for making a
metal annular member of precise tolerances and also to a method for providing
desired surace finish.
Suspension systems, particularly those suspension systems found in
automotive applications, make substantial use of devices commonly known as
bushings. Generally these bushings consist of at least two more or less con-
centric annular members, usually of metal, separated by a rubber element of
specific design which element is under compression. Such devices are some-
times called outer and inner metals or "outers" and "inners" and are more
fully described in, for example, United States Patent Nos. 3,893,775;
3,495,859; and 3,199,186. lhe present procedure for making these annular
members involves several draw die steps wherein an initially flat blank is
drawn in successive draw die procedures into the desired configuration. This
procedure is not entirely satisfactory because it is expensive, requiring
repeated transfer steps, and it produces a product not always as accurate as
desired. The relevant prior art may also include the United States Patents
2,506,657 to Webster; 3,224,243 to VanDerberg; 3,789,650 to Axeloff; 3,263,
477 to Roper; 2,930,~83 to Kaul; 3,314,278 to Bergman; 3,668,918 to Benteler;
and 3,740,993 to Moore.
In certain bushings it is desirable or necessary that the surface ` `
of the outer or inner which contacts the rubber element be so configured
or finished as to grip the rubber element so as to eliminate or reduce slip-
page therebetween. One prior art procedure or preventing relative movement
` between the metal sleeves and the elastomeric insert is disclosed in Sievers -
patent 3,893~775 and involves sandblasting the surfaces of the metal sleeves
and thereafter forming a phosphate coating thereon. It is desirable that `~
improved means be provided for forming a rough gripping surface on the metal
sleeves of the bushing. It is desirable that better control over the precise
orm of the surface texture be provided and that this be accomplished in-
3~ expensi~ely. Other prior art related to this eature are United States
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.
3g
Patents 1,940,302 -to ~lumphre; 1,~59,265 to ~erk; 2,725,692 to Andreae;
2,819,105 to ~elinke; 3,368,852 to ~lerbenar; and 3,50~,513 to Bl~ck.
According to one aspect of the present invention there is provided
a process for making a metal annular member of precise tolerances which com-
prises placing an annular sh0et metal blank between a punch and an external
die, forcing the annular blank into the external die by means of the punch
so that the external die reduces the outside diameter of the blank, maintain-
ing said external die in continuous contact with the portion of said blank
that is reduced in diameter, causing at least a portion of the inside dia-
meter of the blank to contract as dictated by said reduction of the outside ;~
diameter and without interference with the punch, seating one end of the
blank against a ridge surrounding the inside of the external die, and driving
the punch axially inside the annular blank and the external die until the .~
punch seats against the other end of the blank thereby forming the blank ~ .
into the desired annular member configuration as determined by the configura- `
tion of the punch and the external die and the ridge thereon.
According to another aspect of the present invention there is
provided apparatus for forming an annular shset metal blank into an annu-
lar member of precise tolerances which comprises: `
;
~a) an external die having a continuous die surface of the configuration
:, desired for the external surface of the annular member, at least one por~
tion of said continuous die surface being of smaller diameter than said ~ ~ .
annular metal blank so as to be capable of shrinking said blank to said ~ ~ `
smaller diameter when said blank is forced through said die, and said die .
having an annular ridge surrounding the inside of the die for seating one ~ .` `:
end of said annular metal blank, .
(b) a first punch mounted with relation to said external die for reci~
~, ~
procal travel through a path into and out of an endmost position within said
. external die, said first punch being shaped and proportioned to fit inside
. 3~ said annular metal blank and having a holding portion that engages and holds
said blank so as to force said blank through said external die when said
: ~ ~ 3 _
39
punch travels toward said endmost position, said first p~lch being spaced
away from the portion of said annular metal blank that is reduced to a
smaller diameter by the continuous die surface of said external die so as
to allow the free inward movement of the internal surface of said annular
metal blank when said external die reduces the diam~ter of the blank, and
(c~ means for reciprocating said fi.rst punch axially through said path
into and out of said endmost position in said external die.
Objects of the invention include the providing of an improved
process and apparatus for making metal annular members of precise :~
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tolerances and the providing of a proc:ess and apparatus for making
metal annular members of precise tolerances without the expendi~ure of
an excessive amount of energy.
Figure 1 is an axial section of an annular member produced by the
method and apparatus of the present invention.
Figure 2 is an end elevation of the structure illustrated in
Figure 1.
Figures 3 and 4 are views similar to Figure l of other types of
annular members produced by the present invention.
Figure 5 is an enlarged section of a portion of the structure
illustrated in Figures 3 and 4.
Figure 6 is a view similar to Figures 1, 3 and 4 of a metal blank
used in the process of the present invention.
Figure 7 is an axial section through the forming apparatus of the
present invention showing the final step in the process of making an
annular member.
Figure 7A is a fragmentary section taken along the line 7A-7A of
, Figure 7.
Figure 7B is an enlarged fragmentary section similar to Figure 7
but with the workpiece removed showing the structure of Figure 7A.
Figures 8 and 9 are views similar to Figure 7 showing the final
step in the forming process of making the alternative forms of annular
members shown in Figures 3 and 4 respectively.
Figure 10 is an enlarged detailed sectional view of a portion of
the structure illustrated in Figures 7, 8 and 9.
Figure 11 is an enlarged sectional detailed view of a portion of
the structure illustrated in Figure 9.
Figures 12-1~ are somewhat schematic views of the structure
,~ illustrated in Figure 7 showing serial steps in the process of making
an annular member
Figures 19, 20, 21 and 22 are views similar to Figures 7, 8, 9
and 10, respectively, but showing alternative forms of the invention.
`- Figures 23 and 24 are views similar to Figures 19 and 20, respec-
~ 59 ~ 3~
tively, but showing an alternative form of the invention.
Figure 25 is a view similar to Figure 24 but showing still
another alternati~e form of the invention.
Figure 26 is a schematic perspective view of the surface
prepara~ion procedure of the present invention.
Figures 27 and 28 are perspective views of annular members in-
corporating the surface treatment of the present invention.
Figure 29 is a fragmentary perspective view of an annular mem-
ber having an embossed grid configuration on its surface.
Figure 30 is an enlarged fragmentary cross section of the sheet
metal 205 after it has passed through the rollers 201.
Figure 31 is an enlarged fragmentary cross section of the rollers
201 showing the surface configuration thereof.
Figure 32 is a schematic side elevation of a tube mill having
the surface texturing device of the present invention combined
therewith. ~::
For the purposes of promoting an tmderstanding of the principles
of the invention, reference will now be made to the embodiment il-
lustrated in the drawings and specific language will ~e used to
describe the same. It will nevertheless be understood that no
limitation of the scope of the invention is thereby intended, such
alterations and further modifications in the illustrated device, and
: such further applications of the prlnciples of the invention as
; illustrated therein being contemplated as would normally occur
to one skilled in the art to which the invention relates.
Referring more particularly to Figure 1, there is illustrated
- a common type of annular member 20. Other annular members 21
and 22 are shown in Figures 3 and ~. The annular member 20 in-
cludes a reduced diameter portion 25, an enlarged diameter portion
26 and a radially outwardly extending flange 27. Such annular mem-
bers are used as a part of isolation bushings and must be formed to
relatively precise tolerances. As an example, the annular member
.
~L~359~3~
the annular member illustrated in Figure l has a length dimension
tolerance 30 in one specific embodiment which ranges between 2 010
and 1.990 inches. The following tolerances are also required of
that specific embodiment of annular member: 31 .02 min.", 32
.03-.08", 33 .430-.470", 34 1.920-1.915", 35 1.853-1.858", 36
1.732-1.742", 37 .OS" max, 3~ .055-.073", 39 1.792-1.802", and 40
2.310-2.290". The above dimensions are, of course, specific
only to a particular embodiment of an annular member but serve
to indicate that such annular members are required to be manufactured
according to precise tolerances. Similar such precise tolerances
are required for the annular members of Figures 3 and 4. Figure 5
shows in detail the cross sectional end edge configuration of the
outer me~als of Figures 1, 3 and ~.
In order to manufacture the annular member in accordance with
the present invention, a cylindrical blank 45 (Figure 6) is provided
which has an outside diameter 46 and a predetermined length 47 both
somewhat greater than the outside diameter and length, respectively,
desired for the final annular member. The blank 45 also has a pre-
cision wall thickness 50. The blank is formed of welded tubing,
that is, flat sheet material which is welded into a cylinder with the
outer weld surface skived and the inner weld surface hot planished
to nominal wall thickness. The welded tubing in the above described
speicific embodimen~ is SAE 1010 commercial quality cold rolled steel.
It is desirable that the wall thickness 50 of the blank be precise,
for example, to produce the specific embodiment described above, that
it be within a range of .057"-.062" for the reason that the wall
thickness, together with the deformation procedure effected upon the
outer surface of the blank is what determines at least a portion of
the ID of the blank in its final form.
Referring now to Figure 7, the structure of the forming apparatus
is illustrated in detail as including a punch 55 and an external die
--6--
~ 59835~
56. Punch 55 includes two members 57 and 60 with the member 57
secured to the member 60 by means of the threaded member 61. It
should be noted that a stencil member 65 has a lower stencil 66
which cooperates with the trap ledge 67 forming a part of the ex-
ternal die 56 to produce an indentation 68 (Figure 2) which functions
~ as an identifying indicia on the flange 27 of the outer metal.
- In one specific embodiment of the invention, the stencil 66 projects
.020" where the thickness of the flange is .060" whereby the resulting
; indentation is approximately 1/3 of the flange thickness.
The punch 55 is reciprocated by a suitable die press such as,
for example, a 30 stroke-per-minute 100 ton capacity straight side
mechanical press with a 10" stroke. The 100 ton capacity is men-
tioned to make the press capable o~ handling six dies or (six parts)
at a time when a lesser capacity press, i.e. 16.7 ton, would operate
to make one part at a time. The external die 56 thus is held in
position so that there can be reciprocation movement of the punch
55 relative to the external die 56. ~lso mounted for reciprocation
within the external die 56 is an ejector and an end coining punch
70. The ejector punch 70 is formed of hardened tool steel. The
punch member 57 as well as the die insert 71 which has thereon the
- inner continuous die face 72 is formed of hardened ground and polished
special treated high speed steel.
It should be noted that the punch member 57 has an externally
opening recess 75 which receives an O-ring 76. The function of the
O-ring 76 is to prevent the blank from falling off of the punch
when the press is stopped in mid-cycle. In Figure 7, the shaded
area 80 extending around the flange 27, the enlarged diameter portion
26 and at the outside of and bottom of the reduced diameter portion
25 indicates contact of the workpiece or blank with the punch and
the die 55 and 56. Thus, there is no contact of the punch with the
inside surface of the reduced diameter portion 25, and this ID is
determined by t'ne deformation of the OD at the reduced diameter por-
~059~33~
tion. It is ~lso inten~ed that the~e b~ no ex~rudillg action in the manufac-
tura of the amlular member o the present invention. ~ 5
Figures 8 and 9 ar0 generally similar to Figure 7 but show the
; punch members 57A and 57B and the corresponding external dies as having a
slightly dif:ferent configuration. It will be noted, howe~er, that in
Figures 8 and 9 the outwardly facing surfaces 57C and 57D o the punch member
57A and 57B do not contact a greater portion of the internal surface of the
annular member as compared to Figure 7. Thus, this relatively large portion ~ ;
of inner surface is determined by the shrinkage of the outer surface during
the forming procedure, together with the precise wall thickness of the blank
45.
Referring now to the somewhat schematic Figures 12-18, the opera-
tion of the structure of Figure 7 is shown serially. Thus, in the process ~ :
of the present invention, the blank 45 o Figure 6 is positioned between the
punch 55 and the external die 56. As shown i.n Figure 13, the punch 55 moves
downwardly into the blank 45 until the blank is received upon the reduced
diameter portion 90 of the punch member 57. The 0-ring 76 serves to maintain
the blank 45 on the reduced diameter portion 90 of the punch in the event
the punch stops in mid stroke. In Figure 14 the next step is shown of the
punch moving downwardly carrying the blank 45 lnto the die 56 until the lower
end 100 of the blank 45 ~see Figure 10) seats against a ridge 101 formed on
the extexnal die member 71. Note that the ridge 101 includes a radially
extending horizontal surface 103 and a tapered surace 105. The tapered
surface 105 is contiguous with the inwardly facing cylindrical surface 102
of the external die.
It will also be evident from Figure 14 that the ejector die 70
is at its lower end of travel relative to the external die 56. Note also
that the ejector die has a ledge 106 CFigure 10) which ls engaged by the
lower end 100 of the blank 45. The surfaces 105, 103, 101 and 106 serve to
coin the lower end of the workpiece and to produce the lower end coniguration
illustrated in Figure 10. The next step of the process is the continued
downward movement of the punch 55 into the position illustrated in Figure 15
59~13~
wherein the enlarged dlameter portion 110 of the punch has becn driven lnto
the workpiece 45 so as to bogin to orm the enlarged diameter portion 26 of
the outer metal.
~he punch 55 includes an outwardly extending surface 115 curving
smoothly into a downwardly extending surface 116. As the punch 55 continues
its downward movement, it curls the upper end portion 117 of the blank 45
into the position illustrated in Figure 16 and the enlarged diameter portion
26 of the annular member is further formed. Figure 17 shows the punch at
its bottom position fully seated against the outer die 56. It will be noted
that the flange 27 has been fully formed by being trapped within the trap
ledge 67, this trap ledge determining the outer diameter of the flange 27.
The thus formed annular member is then ejectad by raising of the punches
55 and 70 to the positions illustrated in Figu~e 18.
Referring now to Figures 19 and 22, an alternative preferred form
of the invention is shown and is id~ntical to the above described configurat-
ion and process of Figures 5, 6, 7, 11 and 12-18 with one important difer-
ence being the orming of the lower end o the workpiece. The most difficult ~ `
tolerances to meet in connection with the forming o~ the annular member of
Figure 1 relate to the chamfer 110! The reason for this is that the plastic
deformation of the metal in the area of the chamfer is more radical tha~ in
other portions of the workpiece. In certain appllcations of the annular mem-
bers, i,e. automotive suspension bushings, the user is willing to give up a
constant internal diameter in favor of an in-turned lower end of the outer
as shown in Figures 19-22. This modified form in certain situations has
been found preferable because it assists in gripping a rubber or rubber-like
sleeve of a shock absorbing unit.
In Figure 19 the ejector punch or knockout pin 111 is formed with
a radially inwardly extending groove 112 including a surface 114 which ~-~
extends inwardly relative to the vertical at an angle of 15 degrees. That
is~ the angle 115~ is 15 degrees. A1SOJ the horizontal surface 103 of the
ridge is eliminated and replaced with the tapering surface 116 which leads
from the cylindrical inwardly facing surface 117 of the external die 120 to
., , ,
~5~ 39
tho cylindrical inwardly facing surace 121 of the e~ternal die 120. In
the process for making the annular member o Figures 19 and 22, the lower
end 122 of the blank ls movod by the p~mch 125 into the external die reducing
the outside diameter of the blank as described above; however, when the lower
end of the blank ls moved against the ridge or tapered surface 116, it is
guided inwardly into the inwardly extending groove 112 thereby forming a
tapered chamfer on the lower end of the blank. The groove 112 has an ou~-
wardly and downwardly extending surface 125' which cooperates with the sur-
faces 114 and 116 to redirect the metal of lower end of the workpiece and to
thereby form it without radical metal deformation. ~ -
Figures 19, 20 and 21 correspond to Figures 7, 8 and 9, respec-
tively, except that they all incorporate the changed process and apparatus
for redirecting the lower end of the workpiece. While the specific construc-
tion features of Figures 19, 20 and 21 are different in some respects, the
purpose and function is generally the same. Thus, in Figures 9 and 11 the
somewhat pointed or chamfered upper end 130 of the workpiece is produced
entirely by the punch 57B, and this is also true o Figure 21. Also, the
manner of limiting downward movement of the ejector punch 111, 140 and 141
is shown in Figures 19, 20 and 21 as involving abutting surfaces 1~5 and 1~6
and is not shown in Figures 7, 8 and 9. Also, the 0-rings 76 of Figures 7,
8 and 9 are not shown, although they may also be used in the embodiments of
Figures 19, 20 and 21 for the same purpose. Another feature which is present
in the embodiment of Figures 19, 20 and 21 but is not shown is lube vents
150 in the external die. These vents pe~mit the flow out of the external ~.
die of oil used to lubricate the inside of the external die. During the
forming process such oil needs to escape in order to allow the external die
to properly form the workpiece. The vents 150 are connected through a duct
~not shown) in the external die to atmosphere. -
,~
Figures 19, 2~, 21 and 22 show a form o the invention wherein the
lower end 122 of the blank requires a larger or more pronounced chamfer than
can be generated by the apparatus illustrated in Figures 7, 8, 9 and 10. In
the embodiments of Figures 7, 8, 9 and 10 the maximum chamfer that can be
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~OS983'9
genera~ed or cointed by the downward force of the tubular blank is approxi-
mately one-third of the metal thickness. If the apparatus of Figures 7-10
is used in an effort to produc0 a greater chamfer, the excessive force which
is used causes the blank to collapse inwardly in the area above the chamfer.
Therefore, the alternate me~hod o Figures 19, 20, 21 and 22 is
provided to allow the chamfered end of the part to form inwardly creating a
greater lead or chamer effect but requiring a substantially reduced forming
force. Figures 19, 20, 21 and 22 also clearly show the chamered end of the
` part formed around the enlarged head 143 or end of the ejector punch 111, 140
or 141. The part is removed from the knockout pin by a orce exerted at the
end o the forming cycle after the part has been ejected to the position of
Figure 18, in other words, has been moved above the external die 120. At
this time a mechanical ejector mechanism 150 shown schematically in Figure
18 moves in the direction of arrows 151 and knocks the part off of the ejector
~ punch 111. The slight stretching actlon required to remove the part from
`, the ejector punch 111 does not exceed the elastic limit of the metal of the
part and for this reason does not deform the part.
Figures 23 and 24 illustrated still urther method and apparatus
for providing a large chamer or lead on the chamfered end o the outer or
inner metal. The method and apparatus of Figure 23 does not require forcing
the part of of the~enlarged head of the ejector punch as in Figures 19-22.
It should be noted that in the procedure of Figure 23 ~as well as Figure 19 `-
I as well as F;gure 7) the shaded area 155 indicates the contact of the work-
i piece or blank with the punch 156 and the external die 157. The shaded area
extends around the flange 27, the enlarged diameter porkion 26 and the out-
side of the bottom of the reduced diameter portion 25. However, in Figure
23, unlike Figures 7 and 19, the shaded area does not include the lower end
160 of the part. As described abo~e in connection with Figure 7, the ~D of
the reduced diameter portion 25 is determined by the deformation of the OD at
- 30 the reducsd diameter portion.
The structure and method of Figure 23 are identical to Figure 19
except that the punch is formed to have a pilot portion 161 which projects
1 1
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through the part. Tho pllot portion 161 provents the lower end of ~he part
from forming inward in an uncontrollod fashion, and lt isf~ly formed by
the frustoconical surface 162 immediately above the pilot portion 161. As `
mentioned, the inside diameter of the part at the reduced portion 25 is
slightly greater than the external diameter of the punch at 165 above the
frustoconical surface 162.
During operatiDn of the apparatus of Figures 23 and 24J the tapered
surface 166 of th~ external die 157 acts to guide the lower end of the par~
against the pilot portion 161 whlch acts as a stop while the forming process
goes through the various serial steps corresponding to Figures 13-16. Final
forming of the lower end of the part occurs when the punch 156 reaches the
position of Figure 23 and the surface 162 engages and forms the inside of `
the lower end of the part, Of course, the surface 162 is stopped in its
illustrated position by the meeting of the external die and ejector punch
surfaces 170 and 171.
It can be seen that the apparatus of Figures 23 and 24 permits
removal of the part from the dies without stretching o the chamfered end
as required in the apparatus of Figures 19-22. Figure 25 shows another
embodiment of the method and apparatus of this invention which permits even
more extensive i~ward orming of the`lower end of the part to the extent o ~`
:
permitting an inwardly directcd flange 180 to be formed. The method and
i`: apparatus o Figure 25 are identical to that of Figures 23 and 24 with the
exGeption that the ejector punch 181 has an annular projection 182 thereon
-~ which has an upper ormlng surace 183. Also the tapered surface 162 o
punch 156 is replaced by the radially extending surface 185.
Referring to Figure 26, there is illustrated a coil 200 of sheet
metal which is drawn through rollers 201 by suitable drive means ~not shown).
The rollers 201 and the drive means may be a part o a conventlonal reduction
mill, the usual function of which is to reduce the thickness of sheet mater-
ial down to a precise thickness. The rollers 201 may be a part of a tube
mill which forms sheet into tube. The rollers 201 have longitudinal grooves
202 and projections 203 in the external surfaGe thereof which are forced into
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tho sh~t motal 205 as tho rollers rotate .~nd tho sheet metal moves through
the rollers producing longitudinal grooves 206 and projections 208 in the
sheet metal 205. These longitudinal grooves remain in the sheet metal as
it ls formed and w~lded into a tubular coniguration 207 by a butted joint
210 and is then formed into the annular members 211 and 212 by the identical
procedures described above with respect to annular members 20 and 22. Prior
to curling the flat sheet 205 into the tubular configuration 207, it may be
necessary to trim the edges of the sheet metal so that the tube has the proper
diameter. On the other hand, even ~n a reduction mill the reduction in thick-
ness of the sheet metal normally results in a lengthening ra~her than a widen-
ing thereof.
The rollers 201 .in one specific embodiment of the invention are
designed as an attachment or addition to operate on the sheet metal before
it moves into an existing tube mill. In designing new tube mills or reduct-
ion mills, the rollers 201 can be incorporated into the design o the mill
so that the rollers have a double function o reduction to a precise thick-
ness as well as surface texturing.
Figure 30 shows the cross sectional coniguration of the sheet metal
: after it has passed between the rollers 201. The depth, width and configur-
ation of the grooves may vary to provide the result desired; ho~ever, in one
speclfic embodiment the grooves 206 are .060 inches in ~idth and between .002
and .005 inches in depth and the projections are of the sam0 width. Figure
31 shows in cross ~ection the~die coniguration used to produce the sheet
metal surface configuration. This die configuration is constant in cross
section. It should be unders~ood that the rolls 201 are fixed in a spaced
relationship which is the thickness desired for the sheet metal 205. Because
the sheet metal from the coil 200 is thicker than the spacing, a substantial
force must be exerted on the sheet metal by the rolls 201 which might be, for
example, in order of 50 Tons and can be calculated given the various paramet- ~;
ers o the mekal. Thus the structure which holds the rolls in a spaced
relationship should be capable of resisting this force.
In some applications it is desirable or necessary that the resis-
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~ID5~33~ ~ `
tance to slippage between the metal sleeves and ela~tomeric insert be in
both the rotary and axial dir0ctions in whlch case the surface configuration
of Figure 29 is desirable. The sheet metal 215 has a pair of grids 216, one
on each side, including a series of s~uare recesses 217 which are produced
by rollers identical to 201 except that their external configuration is not
constant in cross section but instead includes a series of projections of
mating configuration to the surface of the sheet metal 215. Thus Figure 31
; is also an appropriate cross sectional representation or the rollers which -
produce the configuration of Figure 29.
Figure 32 shows in more detail a tube mill having the present -
invention incorporated therein. A standard uncoiler 225, which might be,
for example, a Single Coil Cradle manufactured by McKay ~ivislon of Wean
Industries of Yo~mgstown, Ohio, uncoils the sheet metal and feeds it into
a standard strip splicer 226 and collector unit which migh~ be, for example,
a strip joining shear welder made by the same company and including an
accumulator 227~ The rollers 201 ar0 represented in Figure 32 by rollers
230 and 231. The roller 230 is driven and rotatable, and its axis is fixed.
The roller 231 is vertically adjustable by the hydraulic motor 228, but its
.
- axis can be fixed in a desired spaced relationship to the roller 230 by
the fram~ 229. The surfaces o the rollers 230 and 231 have the appropriate
configuration to produce the texturing desired 206 or 216 or any other
~` desired texturing such as, for example, annular lines, diagonal cross hatch
` or diamond design patterns, longitudinal parallel ~aved lines, and/or a
simulated phosphated surface. The structure 228-231 ~ill not be described
in greater detail because it is a standard cold reduction mill except for the
-~ particular surface of the rollers 230 and 231. An example of such a cold
.: .
reductlon mill is a Fenn Rolling Mill manufactured and sold by Fenn Manufact-
uring Company of Ne-~ington, Connecticut.
The largG loop 2~5 of sheet metal is used to control the relative
speed o the driven roll 230 and the tube mill 236. T~o electric e~es, not
shown, are located one above and one below the loop 235 and function to slow
down or speed up t~e roll 230. The tube mill 236 is, for example, a 400
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1~59839
series.~lcKay Tube Mill ~ith cut of al~o manu~actured by Mc~ay Division of
- Wean Industri~s. ~ho ~unction o~ the tube mill and welder is to gradually
coil the sheet metal until the opposite edges thercof meet whereupon they are
welded together.
It will b~ evident from the above description that the present
invention provides an improved method and apparatus for making metal annular
....
members of precise tolerances and desired surface finish. While the invent-
ion has been illustrated and described in detail in the drawin~ and foregoing
description, the same is to be considered as illustrative and not restrictive
in character, it bsing understood that only the preferred embodiment has been
shown and described and that all changes and modifications that come within
the spirit of the invention and the scope of the claims are desired to be
protected.
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