U.S. patent number RE31,912 [Application Number 06/515,418] was granted by the patent office on 1985-06-11 for inertial spin welding of thermoplastic and thermoplastic coated container parts.
This patent grant is currently assigned to Cosden Technology, Inc.. Invention is credited to Vincent E. Fortuna, Donald N. MacLaughlin.
United States Patent |
RE31,912 |
Fortuna , et al. |
June 11, 1985 |
Inertial spin welding of thermoplastic and thermoplastic coated
container parts
Abstract
A thermoplastic container bottom is inertially spin welded into
the interior of a cylindrical container body of paperboard
internally lined with a layer of thermoplastic material. A body
supporting mandrel has an expansible body engaging portion which is
inserted into the body and subsequently expanded to define a
cylindrical surface of a diameter exactly equal to that of the
specified internal diameter of the body. A seating member at the
end of the body supporting mandrel establishes the depth to which
the container bottom is inserted into the body and is provided with
a low-friction projecting resilient member which contacts the
rotating bottom.
Inventors: |
Fortuna; Vincent E. (Huntington
Beach, CA), MacLaughlin; Donald N. (Midland, MI) |
Assignee: |
Cosden Technology, Inc.
(Dallas, TX)
|
Family
ID: |
27398557 |
Appl.
No.: |
06/515,418 |
Filed: |
July 20, 1983 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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234344 |
Feb 13, 1981 |
|
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Reissue of: |
415126 |
Sep 7, 1982 |
04386999 |
Jun 7, 1983 |
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Current U.S.
Class: |
156/494;
156/73.5; 156/294; 156/580; 264/532; 425/111; 156/165; 156/304.2;
264/68; 425/DIG.14 |
Current CPC
Class: |
B29C
65/0672 (20130101); B29C 66/12441 (20130101); B65D
15/08 (20130101); B29C 66/542 (20130101); B29C
66/8322 (20130101); B29C 66/72328 (20130101); B29C
65/7885 (20130101); B29C 66/12469 (20130101); B29C
66/73921 (20130101); B29C 66/8226 (20130101); B29C
66/63 (20130101); B29C 66/116 (20130101); B29C
66/114 (20130101) |
Current International
Class: |
B29C
65/06 (20060101); B23K 027/00 (); B29C 027/08 ();
B29D 023/03 (); B28C 001/08 () |
Field of
Search: |
;156/73.5,160,165,296,358,360,294,304.2,397,446,475,492,494,496,580,583.3
;425/111,353,457,468,523,DIG.14,DIG.59 ;264/68,532,523 ;198/651
;294/97 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kimlin; Edward
Assistant Examiner: Falasco; Louis
Attorney, Agent or Firm: Caddell; Michael J.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application is a .Iadd.Reissue of Ser. No. 415,126, U.S. Pat.
No. 4,386,999 which is a .Iaddend.continuation-in-part of an
original application field Feb. 13, 1981, Ser. No. 234,344, by
Vincent E. Fortuna and Donald N. MacLaughlin, entitled "INTERNAL
SPIN WELDING OF THERMOPLASTIC AND THERMOPLASTIC COATED CONTAINER
PARTS", now abandoned.
Claims
What is claimed is:
1. Spin welding apparatus comprising upper and lower mandrel means
mounted for vertical movement toward and away from each other along
a common vertical axis, said upper mandrel means being adapted to
releasably support an open ended cylindrical container body and
said lower mandrel means being adapted to releasably support a
container bottom of thermoplastic material having an axially
upwardly projecting peripheral flange insertable into said
container body with a press fit, first drive means for driving at
least one of said mandrel means in rotation about said vertical
axis relative to the other mandrel means, and second drive means
for driving said mandrel means in movement along said vertical axis
to seat said container bottom within said container body while said
mandrel means are rotating relative to each other to insert and
frictionally weld said container bottom in said container body;
with radially expansible and contractable body engaging means
mounted on the lower end of said upper mandrel means in
symmetrically disposed relationship about said vertical axis, said
engaging means being normally disposed in a contracted position
wherein said engaging means may be axially inserted into a
container body, expanding means for radially expanding said
engaging means to an expanded position wherein the radially outer
surfaces of said expanding means lie on a common cylindrical
surface having a diameter equal to the specified internal diameter
of said container body and further comprising a seating member
mounted at the lower end of said upper mandrel means and engagable
with said container bottom to establish the depth to which said
container bottom is inserted within said container body by
operation of said second drive means.
2. The invention defined in claim 1 wherein said body engaging
means comprises a plurality of like body engaging members, each of
said engaging members having an outer surface conformed to a
circumferential segment of said common cylindrical surface.
3. The invention defined in claim 2 wherein said engaging members
are circumferentially spaced from each other when said engaging
members are in said expanded position.
4. The invention defined in claim 3 further comprising pivot means
at the upper end of each of said engaging members mounting said
members for pivotal movement on said upper mandrel means about
respective axes lying in a common horizontal plane and tangent to a
circle centered on said vertical axis.
5. The invention defined in claim 4 further comprising spring means
adjacent the lower ends of said engaging members resiliently
biasing said engaging members to their contracted position.
6. The invention defined in any of claims 2, 3, 4, or 5 wherein
said expanding means comprises an actuating cam mounted for
vertical reciprocation relative to said engaging members, said cam
having a plurality of vertically inclined cam surfaces respectively
slidably engaged with complementary inclined surfaces on each of
said engaging members to force said engaging members radially
outwardly upon vertical movement of said cam in a first direction
relative to said engaging members.
7. Spin welding apparatus comprising lower mandrel means for
supporting and rotating a thermoplastic container bottom having an
upwardly projecting peripheral surface, upper mandrel means for
supporting a cylindrical container body, drive means for inducing
rotation of said lower mandrel about a vertical axis, and means for
moving said mandrels relative to each other along said vertical
axis to seat the peripheral surface of said bottom within the lower
end of said body while said lower mandrel is rotating to
frictionally weld said bottom to said body; wherein said upper
mandrel comprises a plurality of body engaging members
symmetrically disposed about said vertical axis, each of said body
engaging members having an outer surface corresponding to an
axially extending segment of a cylindrical surface of a diameter
equal to the specified internal diameter of said cylindrical
container body, mounting means mounting said body engaging means on
said upper mandrel means for radial expanding and contracting
movement relative to said vertical axis between an expanded
position wherein the outer surfaces of said body engaging members
cooperatively define the major portion of a cylindrical surface
coaxial with said vertical axis and of a diameter equal to said
specified internal diameter and a radially contracted position
wherein said body engaging members may be axially inserted into the
interior of a container body, and expanding means operable when
body engaging members have been axially inserted into a container
body for expanding said body engaging members to their expanded
position to mount said body on said upper mandrel means and to size
said body to said specified internal diameter and further
comprising a low-friction bottom seating member mounted on the
lower end of said upper mandrel means for establishing the depth at
which said bottom is located within said container body while being
frictionally welded thereto.
8. The invention in claim 7 wherein said mounting means comprises
pivot means at the upper end of each member mounting the member for
pivotal movement relative to said upper mandrel means about a
horizontal axis, the horizontal axes of said pivot means being
tangent to a common circle centered on said vertical axis, and
spring means coupled to said members adjacent to the lower ends
thereof resiliently biasing said members to said contracted
position.
9. The invention defined in claim 8 wherein said expanding means
comprises a cam member mounted in said upper mandrel means for
vertical movement relative thereto, said cam member having a
plurality of cam surfaces inclined relative to said vertical axis,
and actuating surfaces on the interior of the respective members
adjacent the lower ends thereof slidably engaged with the
respective cam surfaces to cause expanding pivotal movement of said
members upon vertical movement of said cam member in a first
direction.
10. The invention defined in claim 7 further comprising means
defining a recess in the bottom of said seating member, and a
resilient low-friction pad member mounted in said recess and
normally axially projecting below said seating member to engage
said container bottom prior to the seating of said container bottom
against said seating member, said resilient pad member being
compressible into said recess upon seating of said container bottom
against said seating member.
11. The invention defined in claim 10 wherein said pad member
further comprises an external surface of
polytetrafluoroethylene.
12. Spin welding apparatus comprising upper and lower mandrel means
mounted for relative vertical movement along a vertical axis, said
upper mandrel means being adapted to releasably support a container
upper part having a thermoplastic peripheral surface and said lower
mandrel means being adapted to releasably support a container lower
part having a thermoplastic peripheral surface adaptable to axially
mate with said surface on said upper part with an interference fit,
first drive means for driving said mandrel means in relative
movement along said vertical axis to telescope said upper and lower
part surfaces in mating relation, and second drive means for
driving at least one of said mandrel means in rotation about said
vertical axis relative to the other mandrel means to frictionally
weld said surfaces, radially expansible and contractable part
engaging means mounted on an end of one of said mandrel means in
symmetrically disposed relationship about said vertical axis, said
engaging means being disposable in a contracted position wherein
said engaging means may be axially inserted into one of said parts,
and expanding means for radially expanding said engaging means to
an expanded position wherein the radially outer surfaces of said
expanding means lie on a common cylindrical surface having a
diameter equal to the specified internal diameter of said container
part into which it is inserted.
Description
BACKGROUND OF THE INVENTION
U.S. Pat. No. Re. 29,448 discloses methods and apparatus for
inertial spin welding of thermoplastic container parts. As
disclosed in that patent, two axially mating thermoplastic
container parts are respectively mounted upon axially aligned
mandrels. One of the mandrels is temporarily coupled to a rotary
drive means to bring that mandrel and the container part carried by
the mandrel up to a predetermined rotative speed, at which time the
rotary drive is disengaged, the rotary inertia developed
maintaining the mandrel in rotation after the drive is disengaged.
The two mandrels are then moved toward each other and the two
container parts carried by the respective mandrels seat with each
other. The friction developed by the relatively rotating container
part heats the plastic material as it simultaneously brakes the
relative rotation to melt the material to fuse the parts to each
other when the relative rotation ceases and the parts are permitted
to cool.
In U.S. Pat. No. Re. 29,448, the two parts being welded were both
of a thermoplastic material. This fact is worthy of note in that in
order to generate the frictional heat required to melt the plastic
material, the mating parts of the container must fit with each
other with an interference fit. Where both parts are formed from
the same thermoplastic material, the achievement of an interference
fit of this type is not especially difficult in that the part
dimension is quite accurately established in the forming machine
and any subsequent dimensional changes due to thermal expansion or
contraction where the parts are stored for any substantial period
of time prior to assembly normally affects both of the parts to
substantially the same degree.
In recent years, there has been substantial usage of containers in
which the container body or side wall is formed primarily of
paperboard or cardboard, usually sealed at the opposite ends by
metal tops and bottoms. Cans for motor oil and frozen orange juice
are typical examples of containers of this type. Where a paperboard
container body is employed, it is necessary to coat or line the
interior of the paperboard body with some liquid tight material,
thermoplastic materials being frequently used for this purpose.
Where the paperboard container body is lined with thermoplastic
material, it has been proposed to employ a thermoplastic material
for the container bottom which has led to the discovery that such
bottoms could be spin welded to the container body inasmuch as the
container body has a layer of thermoplastic material on its
interior surface. However, difficulties have been encountered in
forming and maintaining the thermoplastic coated paperboard bodies
within dimensional tolerances acceptable for such a spin welding
operation. In order to apply the thermoplastic liner to the
paperboard, the thermoplastic is normally heated in order to bond
it to the paperboard and subsequent cooling tends to shrink the
material so that the container becomes undersized. Non-uniform
shrinkage in storage also tends to occur, and the paperboard
containers may, during preassembly handling and conveying
operations, become slightly out of round.
The present invention is especially directed to methods and
apparatus enabling the spin welding of thermoplastic bottoms to
thermoplastic lined paperboard containers.
SUMMARY OF THE INVENTION
In accordance with the present invention, a mandrel for supporting
a thermoplastic lined cylindrical container body during a spin
welding operation is provided with an expansible container body
engaging assembly which, in a contracted position, can be axially
inserted into the container body. Body engaging members in the form
of circumferential segments of a cylindrical surface are normally
maintained in a contracted position, as by a circumferential garter
spring. Inclined internal cam surfaces on each of the segmental
members are slidably engaged by a complementarily inclined
actuating cam which, upon axial movement relative to the segmental
members radially expands them outwardly to an expanded position. In
this expanded position, the outer cylindrical surfaces of the
segmental members are .[.accuratley.]. .Iadd.accurately
.Iaddend.located to define a cylindrical surface of a diameter
precisely equal to the specified internal diameter of the body for
spin welding purposes.
A container bottom of thermoplastic material is formed with an
axially upwardly projecting peripheral flange whose major outer
surface is dimensioned for the desired interference fit with the
specified internal diameter of the can body. The outer upper edge
of this flange is tapered upwardly and inwardly so that the flange
can be pressed up into the interior of the container body with the
desired press fit.
A seating member is mounted at the lower end of the body carrying
mandrel to establish the depth to which the container bottom is
inserted into the can body. The seating member is provided with a
low-friction resilient member which normally projects axially
downwardly below the bottom of the seating member. In the assembly
operation, the bottom is first elevated by its mandrel into contact
with this resilient member, and the bottom carrying mandrel is then
engaged with the rotary drive to bring the bottom mandrel up to
rotary speed.
Other objects and features of the invention will become apparent by
reference to the following specification and to the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view, with certain parts omitted or
broken away, of an inertial spin welding machine embodying the
present invention;
FIG. 2 is a detail cross-sectional view of an upper mandrel of the
machine in FIG. 1;
FIG. 3 is a detail cross-sectional view taken on the line 3--3 of
FIG. 1;
FIG. 4 is a detail cross-sectional view taken on the line 4--4 of
FIG. 2;
FIG. 5 is a detail cross-sectional view taken on the line 5--5 of
FIG. 2;
FIG. 6 is a detail cross-sectional view taken on the line 6--6 of
FIG. 2;
FIG. 7 is a cross-sectional view of a container body and container
bottom to be spin welded by the machine of FIG. 1;
FIG. 8 is an enlarged detail cross-sectional view of the container
bottom and body indicating relative dimensions;
FIG. 9 is a detail cross-sectional view showing the container
bottom and body welded to each other; and
FIG. 10-1 through 10-7 are schematic diagrams showing sequential
steps in the spin welding operation performed by the machine.
The machine of the present invention, taken as a whole, utilizes
many of the features disclosed in U.S. Pat. No. Re. 29,448, the
disclosure of which is hereby incorporated by reference. In the
following description, and in the drawings, many parts of the
present machine are illustrated in a simplified form and described
only generally inasmuch as similar parts and structures are shown
and described in detail in U.S. Pat. No. Re. 29,448, to which
reference may be had if further detail is desired.
Referring first to FIG. 1, the stationary frame of the present
machine includes a base designated generally 10 which fixedly
supports a vertically extending central post 12. A cylindrical cam
track 14 is fixedly mounted as by a plate 16 upon the upper end of
post 12 in coaxial relationship with the vertical axis of the post.
A second cylindrical cam track 18 is fixedly mounted on base 10.
All of the structure described thus far constitutes the stationary
frame of the machine, all of the remaining shown in FIG. 1 is
mounted for rotation about the axis of vertical post 12, only a
portion of the rotatable structure being shown.
The rotary structure includes a central sleeve 20 mounted upon post
12 for rotation relative to the post as by a series of bearings 22,
sleeve 20 carrying upper and lower tables 24, 26 fixedly attached
to the sleeve.
In FIG. 1 there is shown only a single set of mandrels which
include an upper mandrel assembly designated generally 28,
supported generally from upper table 24, and a lower mandrel
assembly designated generally 30 carried generally by lower table
26. In the actual machine, there are several sets of upper and
lower mandrels disposed symmetrically about the axis of the
machine, this arrangement being shown in U.S. Pat. No. Re. 29,448
previously referred to.
A drive gear 32 is fixedly secured to the lower end of sleeve 20 to
drive the sleeve and the various parts mounted thereon in rotation
about post 12. As the sleeve and upper and lower tables 34 and 26
are rotated, the upper and lower mandrels 28 and 30 move in a
circular path around central post 12. During this movement, a
roller 34 on lower mandrel assembly 30 moves along a groove 36 in
lower cam track 18 to raise and lower, lower mandrel assembly 30 at
appropriate points in its cyclic movement around post 12. A similar
roller 38 engaged in a similar groove in upper cam track 14
likewise vertically raises and lowers upper mandrel assembly 28,
while a second roller 40 engaged with upper cam track 14 operates
an actuating device to be described below. The vertical
reciprocation of the mandrel assemblies is quite similar to that
described in detail in U.S. Pat. No. Re. 29,448, for which
reference may be had for further details.
Further details of upper mandrel assembly 28 are shown in FIGS.
2-5.
Referring first to FIG. 2, upper mandrel assembly 28 includes a
rigid hollow sleeve 42 which is fixedly secured at its upper end to
upper table 24. A housing designated generally 44 is mounted on the
exterior of sleeve 42, as by slide bearings 46 for vertical
reciprocatory movement on sleeve 42. Housing 44 is suspended by a
pair of support rods 48, see FIG. 3, which are fixedly secured at
their lower ends to flange 50 of housing 44 and pass upwardly
through openings 52 in upper table 24. A cross member 54 is fixedly
secured to the upper ends of support rods 48 and serves as a
mounting for cam roller 38 which, as best seen in FIG. 1, rides in
the upper groove of cam track 14. Housing 44 is thus suspended by
support rods 48 from cam roller 38 and the housing moves upwardly
and downwardly in accordance with the path followed by roller
38.
Returning now to FIG. 2, a vertical guide rod 56 is fixedly secured
at its lower end to a second flange 58 on housing 44 and projects
upwardly through an opening 60 in upper table 24 to vertically
guide housing 44 in movement.
Four container body engaging members 62 are pivotally suspended
from the lower side of flange 58. As best seen in FIGS. 4-6, the
four engaging members 62 have the conformation of a circumferential
segment of a hollow cylinder, the circumferential extent of each
body engaging segment 62 being slightly less than one-quarter of
the overall circumference so that spaces such as 64 between the
axially extending edges of adjacent members 62 enable the members
to be moved radially inwardly relative to one another to an outer
diameter less than that of their outer surfaces. The outer diameter
of the members 62 as viewed in FIGS. 4, 5 and 6 is equal (with a
slight negative tolerance) to the specified internal diameter of a
cylindrical container body to be received upon the members 62. This
particular diameter is of substantial importance to the rpesent
invention and will be discussed in further detail below.
Referring now particularly to FIGS. 2 and 3, it is seen that four
radial slots 66 are cut into the underside of housing flange 58,
each slot, as best seen in FIG. 4, overlying one of the body
engaging members 62. A projection 68 at the upper end of each
member 62 passes upwardly through the slot 66 and a horizontally
extending pivot pin 70 pivotally suspends each member 62 from
housing 44 at the underside of flange 58. Pivot pins 70 all line in
a common horizontal plane and, as best seen from FIG. 4, are so
oriented that they are all tangent to a common circle centered on
the central vertical axis of sleeve 42. A garter spring 72 is
mounted within circumferential grooves 74 on the outer sides of
each of the members 62 and resiliently biases the lower ends of the
four members 62 radially inwardly toward each other so that the
outer surfaces of members 62, as viewed in FIG. 2, are normally
inclined downwardly and inwardly toward each other.
Referring now particularly to FIG. 2, a downwardly and inwardly
inclined cam surface 76 is formed on the interior side of each
member 62 near the lower end of the member. A cam member 78 having
cam surfaces 80 of complementary inclination is located between the
member 62 and is fixedly mounted to the lower end of an actuating
rod 82 which passes freely centrally upwardly through sleeve 42 and
is secured at its upper end (FIG. 3) to a bracket 84 which mounts
cam roller 40. As best seen in FIG. 1, bracket 84 also slidably
receives the upper end of guide rod 56.
Referring now particularly to FIG. 5, it is seen that cam member 78
is of a cross-shaped configuration when viewed from above, with cam
surfaces 80 being located at the ends of each of the four arms of
the cross-shaped configuration. The lower portion of housing 44 is
provided with four radial slots 86 through which the arm portions
of cam member 78 freely project.
Referring now particularly to FIGS. 2 and 6, seating member 88 is
fixedly mounted to the lower end .Iadd.on .Iaddend.housing 44 by
means such as welding or as by screws 90 (FIG. 6). A recess 96 is
formed on the lower side of seating member 88 and a resilient
member 98, whose purpose will be described in greater detail below
is fixedly mounted in and projects downwardly from the recess.
Member 98 can be compressed to lie entirely within recess 96. In
order to reduce friction, member 98 may be made from or coated with
a low-friction material such as polytetrafluoroethylene
(Teflon).
An ejector plate 100 having a circular opening 102 is mounted at
the lower end of a plurality of support rods such as 104, support
rods 104 being fixedly mounted in table 24.
Referring now to FIGS. 7-9, in those figures are shown
cross-sectional views of a container body and bottom which are to
be spin welded by the apparatus described above. Referring first to
FIG. 7, a container body CB of cylindrical shape is shown in
cross-section. The container body CB is formed by a cylindrical
tube of paperboard 106 whose interior surface is lined with a
moisture barrier liner or coat of a suitable thermoplastic material
108 such as polyethylene, polystyrene, or polypropylene. A
container bottom B is formed of the same thermoplastic synthetic
plastic material with a bottom 110 and an integral upwardly
projecting peripheral flange 112. As best seen in the enlarged view
of FIG. 8, flange 112, is formed with a downwardly and outwardly
inclined surface at its upper end, because in order to perform the
desired spin welding operation, there must be an interference fit
between the inner surface of the thermoplastic layer 108 on
container body CB and the outer surface 116 of flange 112. The
inclined surface 114 enables the flange to be pushed axially
inwardly into the container interior with a shoehorn-like
action.
A second upwardly projecting flange 118 preferably is located upon
the container bottom B to protect the lower edge of the paperboard
portion of the container body, as best illustrated in FIG. 9, which
shows the bottom and container body at the conclusion of the spin
welding operation.
The container bottom B preferably is provided with a downwardly
projecting flange 120 and a plurality of radially extending ribs
122 extend from the inner side of flange 120 to the bottom surface
of bottom B to provide a rotary drive coupling between the bottom B
and lugs formed on the upper surface of lower mandrel 30.
THE OPERATION
A general sequence of operation of the apparatus described above is
illustrated schematically in FIGS. 10-1 through 10-7.
The initial step in the operation is shown in FIG. 10-1 in which
upper mandrel 28 is raised to its maximum elevation and cam
actuating rod 82 is likewise raised to its maximum elevation to
position cam member 78 relative to body engaging members 62 in the
position shown in FIG. 2. As previously described, vertical
positioning of upper mandrel 28 and cam actuator 82 is controlled
by rollers 38 and 40 respectively, these rollers riding in grooves
in the stationary upper cam track 14 (FIG. 1) to raise and lower
the respective rollers as the upper and lower mandrels are rotated
about the axis of central post 12 of the machine frame. The broken
lines 38C and 40C in FIGS. 10-1 through 10-7 approximately indicate
the configuration of the cam tracks upon which rollers 38 and 40
ride. Similarly, the broken line 34C indicates the cam track upon
which the lower mandrel positioning roller 34 moves.
With cam rod 82 and cam 78 in their maximum elevated position
relative to body engaging segments 62, garter spring 72 has
radially contracted the lower ends of segments 62 so that the
cylindrical outer surfaces of segments 62 in FIG. 10-1 approximate
a downwardly convergent frustoconical surface having an outside
diameter at its lower end substantially less than the internal
diameter of a container body CB.
In FIG. 10-1, a container body CB is located on a feed table FT-1
in underlying coaxial alignment with upper mandrel 28. A container
bottom B has been fed from a second feed table FT-2 onto the upper
end of lower mandrel 30.
In FIG. 10-2, upper mandrel 28 has been lowered to insert the
container body engaging segments 62, fully into the interior of the
container body CB. During this lowering movement of upper mandrel
28, cam actuating rod 82 is simultaneously lowered so that no
relative vertical movement between actuating rod 82 and upper
mandrel 28 occurs, and the body engaging segments 62, located in
the interior of container body CB in FIG. 10-2 are thus still in
the radially contracted position as in FIG. 10-1.
In FIG. 10-3, actuating rod 82 has been moved downwardly relative
to upper mandrel 28. Referring briefly to FIG. 2, the lowering
action of rod 82 illustrated in the transition from FIG. 10-2 to
10-3 causes cam member 78 to move downwardly from the position
shown in FIG. 2, this downwardly movement of cam member 78 causing
its inclined cam .[.surfaced.]. .Iadd.surfaces .Iaddend.80 to slide
downwardly along the inclined surfaces 76 on body engaging members
62 to pivot the members 62 radially outwardly about their
respective pivots 70 into full contact with the interior wall of
container body CB.
As previously described above, the characteristics of container
body CB and the process by which the container body is manufactured
are such that at the time the container body is fed into the spin
welding apparatus, the internal diameter of the body is normally
somewhat smaller than its specified diameter. The container bottom
B, on the other hand, is quite accurately formed to its specified
diameter and maintains this diameter quite accurately after its
formation. In order that the spin welding of the container body to
its bottom may be efficiently performed, it is essential that the
container body be at its specified internal diameter at the time
the container bottom is inserted into the body so that the desired
interference fit between these two parts, one of which is rotating
relative to the other, will generate the desired amount of
frictional heat to fuse the opposed thermoplastic surfaces to each
other.
As described above, the outer surfaces of the body engaging members
62 of upper mandrel 28 are accurately machined to a diameter
corresponding (with a slight negative tolerance) to the specified
internal diameter of container body CB. The radial expansion of
body engaging members 62, by actuation of cam rod 82 after the
members have been inserted into the container body, is likewise
accurately regulated so that at the conclusion of the cam actuated
expansion of body engaging members 62, the outer surfaces of these
members are conformed to a cylindrical surface of a diameter equal
to the specified internal diameter of the container body (with a
slight negative tolerance). Thus, in FIG. 10-3 in conclusion of the
expansion of body .[.engagning.]. .Iadd.engaging .Iaddend.members
62 by lowering of cam actuator 82, the interior of the container
body has been accurately expanded to its specified diameter. The
lower ends of body engaging members 62 are spaced upwardly slightly
from the bottom of the container body to afford sufficient axial
clearance for the insertion of flange 112 of the container bottom
C.
In FIG. 10-4, lower mandrel 30 has been elevated to position the
container bottom B closely beneath, but out of contact with, the
lower end of the container body CB supported upon the upper
mandrel. In this step of the process, the lower mandrel 30 is
engaged with a drive belt DB which drives the lower mandrel in
rotation about its axis. The drive belt DB operates along a portion
of the circular path followed by the lower mandrel, see U.S. Pat.
No. Re. 29,448 for details of this driving arrangement. The
container bottom B is rotatively locked to lower mandrel 28 by the
webs 122 and thus rotates with the lower mandrel.
The next step in the sequence of operation finds upper mandrel 28
being lowered slightly to seat the container bottom B within the
bottom of the container body. Just prior to this lowering step,
lower mandrel 30 passes out of engagement with drive belt DB,
however, the rotary inertia of lower mandrel 30 maintains the lower
mandrel in rotation as the bottom inserting step is performed.
Because the container body CB carried by the upper mandrel 30 is
held against rotation, the relative rotation between the engaged
thermoplastic lined interior of container body CB and the rotating
thermoplastic bottom B carried by the lower mandrel generates
frictional heat melting the two engaged surfaces and at the same
time exerts a braking action upon the rotating lower mandrel and
container bottom. This braking action swiftly brings the freely
rotating lower mandrel to a halt, the energy expended in the
braking operation being converted to the heat which melts and, upon
halting, fuses the container bottom to the container body.
In FIG. 10-6, the lower mandrel has been lowered to its original
position, the now fused container body and bottom are carried above
an outfeed table OF and cam actuating rod 82 has been elevated to
permit the body engaging members 62 to be restored to their
contracted position by garter spring 72.
In FIG. 10-7, upper mandrel 28 has been elevated to its original
position to drop the container body CB onto the outfeed table, this
separation of the container body from the upper mandrel having been
assisted by stripper plate 100 (FIG. 2).
While one embodiment of the invention has been described in detail,
it will be apparent to those skilled in the art that the invention
may be modified. Therefore, the foregoing description is to be
considered exemplary rather than limiting, and the true scope of
the invention is that defined in the following claims.
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