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Description  |
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FIELD OF INVENTION
The present invention relates generally to the field of apparatus and
methods for automated feeding and joining of elongate preformed
thermoplastic elements. In preferred embodiments, the present invention
relates to apparatus and methods whereby preformed tubular thermoplastic
core elements may automatically be fed and coaxially joined end-to-end
during manufacture of melt-blown filter cartridges.
BACKGROUND OF THE INVENTION
Filter cartridges formed of a nonwoven mass of a melt blown polymer are
well known and have achieved widespread use in fluid filtration
applications. Typically, such melt blown filter cartridges are made by
extruding a polymer through orifices associated with a melt blowing die to
form fibers which are directed toward an axially elongate rotating
perforated core element. During melt blowing, a flow of inert gas (e.g.,
air) acts on the molten fibers so as to attenuate the fibers to relatively
fine diameter and to randomly distribute the attenuated fibers onto the
core element. Over time, therefore, an annular mass of nonwoven, randomly
intermingled solidified fibers builds up on the core element. Controlled
axial movement of the built-up mass of melt blown fibers relative to the
melt blowing die will therefore allow a cylindrical filter cartridge of
indefinite length to be formed continuously.
U.S. Pat. Nos. 4,112,159 and 4,116,738 to Pall (hereinafter "the Pall '159
and '738 patents", the entire content of each being expressly incorporated
hereinto by reference) disclose the temporary end-to-end joining of
sequential preformed core elements by means of coaxially interdigitated
spacers so that the joined preformed core elements are capable of being
rotated and axially traversed as a unit relative to a melt-blowing die
during the continuous production of melt-blown filter cartridges. The
melt-blown fiber layer is subsequently cut at about the midpoint of the
spacers leaving a lap which extends beyond the core elements at each end,
thereby making it possible to pull off a filter length by withdrawing the
core portion of the next following spacer. Presumably, the spacers removed
from the filter lengths are then reused in the process disclosed in the
Pall '159 and '738 patents.
As an alternative to using preformed core elements, the Pall '159 and '738
patents also disclose that the core element can be formed in situ by means
of a continuous rotatable tubular extrusion die. The core element is thus
extruded continuously in tubular form with an open central passage, in a
continuous length. Prior to receiving the melt-blown fibers, the extruded
core element is perforated or slit by cutting means to provide a plurality
of apertures for passage of fluid therethrough into the central open
passage of the core.
The techniques disclosed in the Pall '159 and '738 patents are not without
disadvantages. For example, when using spacers as the means to couple
preformed core elements in an end-to-end manner, care must be exercised
that the melt-blown fiber media is cut at about the spacer's midpoint,
thereby limiting the maximum length of the filter cartridge to the length
of the preformed core element. Furthermore, the cut cannot be made
entirely through the melt-blown fiber media and the spacer, since to do
otherwise would result in sacrifice of the spacer thereby adding to the
overall production costs of the filter cartridge. On the other hand, the
continuous extrusion of the core element necessarily involves the
provision of a rotatable extruder and core-perforation equipment which may
not be cost effective in terms of:already preformed core elements.
Thus, what has been needed in this art are apparatus and methods whereby
preformed core elements may be joined integrally end-to-end without
necessarily using any separate joining structure (e.g., such as spacers).
It is toward fulfilling such a need that the present invention is
directed.
BACKGROUND OF THE INVENTION
Broadly, the present invention relates to apparatus and method whereby
elongate preformed thermoplastic elements are friction-welded (as that
term is defined below) coaxially in an end-to-end manner so that the core
elements are joined integrally to one another. Most preferably, the
elongate elements are perforated tubular elements formed of a
thermoplastic material which are employed as core elements in the
production of cylindrical melt-blown filter cartridges. As such, the
integrally joined core elements can be rotated and traversed as a unit
relative to a melt-blowing die during the continuous production of
indefinite length cylindrical melt-blown filter cartridges.
For ease of discussion, reference will be made hereinafter only to tubular
perforated core elements formed of a thermoplastic material which are
typically employed in the production of melt-blown filter cartridges, it
being understood that the present invention is likewise applicable to
elongate thermoplastic elements generally.
The term "friction-weld" and like terms as used herein are meant to refer
to the integral joining of abutted ends of the preformed elements by
friction-generated heat which causes coalescence or melding of the
thermoplastic material to occur at the interface between the abutted ends
of the core elements. According to the present invention, such
friction-welds are achieved by relative high speed rotation of one of the
core elements (most preferably the upstream core element) about its
longitudinal axis relative to the other abutted core element. Such
relative high speed rotation will thus generate sufficient frictional heat
to cause the thermoplastic material at the abutted ends of the core
elements to at least partially melt and/or become sufficiently plasticized
to an extent that the thermoplastic material at the abutted preformed core
ends melds and/or coalesces. Upon cessation of the relative high speed
rotation, the melded and/or coalesced thermoplastic material at the
abutted ends of the core elements quickly resolidifies so as to integrally
join the core elements end-to-end.
In such a manner, the joined core elements may be rotated and traversed as
an integral unit relative to a melt-blowing die during the continuous
production of melt-blown cylindrical filter cartridges. The present
invention, therefore, also includes a feeding assembly to ensure that core
elements are sequentially fed into position and joined to the immediately
preceding core element by friction welding as described briefly above.
Therefore, according to the present invention, preformed thermoplastic
core elements may be sequentially fed and joined end-to-end during the
continuous production of melt-blown cylindrical filter cartridges without
necessarily employing spacers or like separate joining structures. As
such, the formed filter cartridges can be cut to virtually any length,
although it is presently preferred that the cut be positioned at or near
the friction weld between the joined core elements.
These and other aspects and advantages of this invention will become more
clear after careful consideration is given to the following detailed
description of the preferred exemplary embodiment thereof.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Reference will hereinafter be made to the accompanying drawings wherein
like reference numerals throughout the various FIGURES denote like
structural elements, and wherein;
FIG. 1 is a front elevational view showing a system especially adapted for
forming melt-blown cylindrical filter cartridges which employs an
automated preformed core feeding and joining apparatus according to the
present invention;
FIG. 2 is a front elevational view of the automated preformed core feeding
and joining apparatus according to the present invention;
FIG. 3 is a side elevational view of the preformed core feeding and joining
apparatus as taken along line 3--3 in FIG. 2;
FIG. 4 is a top plan view of the preformed core feeding and joining
apparatus as taken along line 4--4 in FIG. 3;
FIG. 5A is an enlarged side elevational view of the core feed tray assembly
employed in the apparatus of this invention;
FIG. 5B is a plan view of the core feed tray assembly as taken along line
5B--5B in FIG. 5A;
FIG. 6 is an enlarged side elevational view of the core element magazine
that is employed in the core feeding and joining apparatus of this
invention;
FIGS. 7A and 7B each represent the operational sequence of the transfer
gate employed in the core element magazine;
FIG. 8 is a foreshortened side elevational view of the core element lift
assembly which sequentially transfers core elements from the magazine to
the in-feed side of the feed tray assembly;
FIGS. 9A and 9B are enlarged side elevational views of the upper end of the
core element lift assembly showing the sequence by which core elements are
transferred into the in-feed cute of the feed tray assembly;
FIGS. 10A and 10B are enlarged side elevational views of the upper end of
the core feed tray assembly showing the operational sequence of the core
alignment fingers;
FIGS. 11A and 11B are each enlarged side elevational views showing the
operational sequence of the core feeding gates; and
FIGS. 12A and 12B are schematic perspective views showing the operational
sequence employed to friction-weld a coaxially aligned pair of preformed
tubular core elements.
DETAILED DESCRIPTION OF THE PREFERRED EXEMPLARY EMBODIMENTS
An exemplary system for manufacturing melt-blown cylindrical filter
cartridges is shown in accompanying FIG. 1 as including a core feeding and
joining apparatus 10 according to the present invention, positioned
upstream of a melt-blowing section 12 and a downstream cutting section 14.
As will be explained in greater detail below, the apparatus 10 according
to this invention is provided so as to automatically feed and join in
end-to-end manner preformed core elements C so that the joined core
elements C may then be rotated and axially advanced through the
melt-blowing section 12. The core elements C are, in and of themselves,
highly conventional in the art of melt-blown filter cartridges in that
they are each perforated so as to have fluid passageway apertures (not
shown) formed therethrough.
As shown in FIG. 1, three core elements designated C, C' and C" are shown
disposed coaxially end-to-end. The melt-blowing section 12 therefore lays
down an annular mass of nonwoven continuous filaments onto the rotating
and axially translating joined core elements C' and C" so as to form a
cylindrical filter cartridge preform FCP of indefinite length. The filter
cartridge preform FCP may then be cut into desired lengths at the cutting
section 14 so as to obtain a generally cylindrical filter cartridge.
Preferably, the melt-blowing section 12 and the cutting section 14 are as
described in copending, commonly owned U.S. Pat. No. -,---,--- which
issued from U.S. patent application Ser. No. 08/433,006 filed on May 2,
1995, the entire content of which is expressly incorporated hereinto by
reference. As will be discussed in greater detail below, the core element
C is fed and integrally joined end-to-end to the core element C'.
As is perhaps shown more clearly in accompanying FIGS. 2-4, the preformed
core feeding and joining apparatus 10 of this invention is generally
comprised of cradle assemblies 18a-18c, a feed-tray assembly 20 which
automatically sequentially feeds preformed cores C to the cradle
assemblies 18a-18c, and a motorized spindle assembly 22. The cradle
assemblies 18a-18c, feed tray assembly 20 and spindle assembly 22 are each
supported by a suitable table frame 23 to establish a generally
horizontally disposed conveyance path of the core elements C established
by the cradle assemblies 18a-18c. Furthermore, a core magazine assembly 24
is provided at the rear of the apparatus 10 and includes a core lift
assembly 26 in order to transfer core elements C from the magazine
assembly 24 to the feed tray assembly 20 and thereby maintain an available
stand-by supply of core elements C therein.
As shown particularly in FIG. 4, each of the cradle assemblies 18a-18c is
most preferably provided with a feed gate 28a-28c operatively coupled to
the shaft 30a-30c of a pneumatic actuation cylinder 32a-32c, respectively.
Each of the cylinders 32a-32c is operated simultaneously so as to move the
feed gate 28a-28c reciprocally between a stop position (in which the next
successive core element C in the feed tray assembly 20 is prevented from
rolling by gravity into the cradle assemblies 18a-18c) and an open
position (in which the next successive core element C in the feed tray
assembly 20 is allowed to roll by gravity from the feed tray assembly 20
and onto the cradle assemblies 18a-18c). Selective simultaneous operation
of the pneumatic actuation cylinders 32a-32c (which may occur by automated
actuation of solenoid valves by a microprocessor-based controller, not
shown), will therefore allow the next sequential core element C in the
feed tray assembly 20 to be positioned coaxially upstream of the previous
core element C' in sequence.
The motorized spindle assembly 22 is mounted on a spindle table 40 by keyed
guideways 40a for reciprocal rectilinear movements between a retracted
position as shown (wherein the spindle 42 is physically separated from the
rearward end of the core element C positioned within the cradle assemblies
18a-18c) and an advanced position (wherein the spindle 42 is inserted into
the rearward end of a core element C positioned within the cradle
assemblies 18a-18c). In this regard, the spindle table 40 is slidable
between its retracted and advanced positions by means of pneumatic
cylinder 44 (see FIG. 2) having an actuator 44a attached to a back plate
46. Thus, operation of the hydraulic cylinder 44 will in turn
extend/retract the ram 44a which acts on the back plate 46 and thereby
causes the spindle table to slide between its retracted and extended
positions. The spindle 42 includes inflatable bladder elements 42a (only
one of which is shown in the accompanying drawing FIGURES) which expand
when supplied with pressurized fluid (e.g., air) through conduit 42b. The
expanded bladder elements 42a thereby frictionally grip the interior of
the core element C when the spindle assembly 40 is moved into its advanced
position so as to temporarily couple the core element C to the spindle 42
and thereby allow the rotation of the spindle 42 to be imparted to the
core element C.
The spindle 42 is operatively attached to a gear unit 48 capable of
imparting high speed rotational motion to the spindle 42 about the
spindle's longitudinal axis (which is substantially coaxial to the
longitudinal axes of the core elements C when positioned in the cradle
assemblies 18a-18c). The gear unit 48 receives driven input from an
electric motor 50 through a belt and pulley assembly 50a.
Accompanying FIGS. 5A-5B perhaps best illustrate the feed tray assembly 20.
Specifically, the feed tray assembly 20 includes a bottom tray wall 20a,
opposed lateral tray walls 20b, and a pair of partial top walls 20c joined
to an upper edge of a respective one of the lateral tray walls 20b. The
walls 20a-20c thereby define a space 20d which accommodates the core
elements C.
Supports 52 support the tray assembly 20 so that it extends upwardly at an
angle relative to a horizontal plane from the cradle assemblies 18a-18c.
In such a manner, therefore, the core elements C will roll downwardly by
gravity from the tray assembly 20 and into the cradle assemblies 18a-18c.
A pair of guide plates 20e, 20f upwardly extend from the upper end of the
space 20d and serve as an inlet chute for guiding the core elements C into
the space 20d. Low and high proximity sensors 54a, 54b, respectively are
provided so as to issue signals to the controller (not shown) in the event
that the presence of a core element is not sensed. In this regard, the
controller will alert the operator and/or shut down the apparatus 10 in
response to receiving a signal from the low proximity sensor 54a which is
indicative of near exhaustion of the supply of core elements in the feed
tray assembly 20. On the other hand, a signal issued by the high position
sensor 54b will initiate a transfer operation (to be described in greater
detail below) so as to transfer another core element C from the magazine
assembly 24 to the feed tray assembly 20 via the core lift assembly 26 and
thereby replenish the supply of core elements in the feed tray assembly
20.
The bottom tray wall 20 is provided with a series of laterally separated
(relative to the longitudinal axis of the core elements) slots 56a which
receive a respective one of the alignment fingers 56. The alignment
fingers are reciprocally moveable towards and away from the core elements
positioned in the interior tray space 20d between an upper position as
shown in the drawings to a lower position where the fingers 56 contact an
uppermost one of the core elements C in the tray space 20d. The alignment
fingers 56 are most preferably actuated by a pneumatic cylinder 56a (see
FIGS. 10A and 10B) which is automatically initiated by the controller in
response to movement of the feed gates 28a-28c into their open positions
so as to allow the next sequential one of the core elements C to roll by
gravity into the cradle assemblies 18a-18c. Upon actuation, therefore, the
fingers 56 will move within their respective slots 56a from the upper
position shown and into the lower position where the uppermost core
element C is contacted. In such a manner, therefore, the alignment fingers
56 encourage the stack of core elements C to roll downwardly along the
feed tray assembly 20 to thereby ensure that the forwardmost one of the
core elements C in the stack is seated properly within the cradle
assemblies 18a-18c.
The core magazine and core lift assemblies 24, 26, respectively, are shown
in greater detail in accompanying FIG. 6. In this regard, the magazine
assembly 24 generally includes a magazine housing 60 provided with a
series of vertically oriented interior partitions 60a which in turn define
a series of vertically oriented channels 60b therebetween for receiving a
lengthwise oriented stack of core elements C. (Only a portion of the core
elements C in the stack contained by channels 60b is depicted in FIG. 6
for clarity of presentation). The housing 60 is mounted upon a platform
frame 62 so as to be moveable therealong between a forwardmost position
(where the housing 60 is positioned close to the tray assembly 20 as shown
in solid lines in FIGS. 3 and 6) and a rearwardmost position (where the
housing 60 is spaced from the tray assembly 20 as shown in chain line in
FIG. 3). The platform frame 62 is itself supported for roiling movement by
casters 62a.
The support platform 62 is provided with an input slot 64 into which core
elements C drop by gravity upon alignment of one of the channels 60b
thereover. Specifically, as shown in FIG. 6, a first stack of core
elements C is positioned vertically in registry over the input slot 64. As
such, the stack of core elements C drop by gravity into the slot 64. A
pivotal transfer gate 66 arrests the vertical drop of core elements C.
However, upon actuation of the pneumatic cylinder 66a, the transfer gate
66 will be pivoted clockwise as viewed in FIG. 6 so as to transfer the
lowestmost core element C in the stack to the inclined transfer tray 68.
After all of the core elements in a particular one of the channels 60b
defined between the partitions 60a have been transferred in this manner,
the pneumatic actuator 70a will be operated so as to disengage the pawl 70
from the ratchet rack 72. The housing 60 will thereafter be moved (e.g.,
via hydraulic cylinder or electric motor drive units, not shown)
incrementally one channel-width leftward as viewed in FIG. 6 so that a
fresh stack of core elements C in the next sequential channel 60b will be
in registry with the input slot 64. The pneumatic actuator 70 will then
return the pawl 70 into engagement with the ratchet 72 to maintain the
housing 60 in such a position.
The transfer tray 68 slopes downwardly from the transfer gate 66 toward the
lift cradle 80 of the core lift assembly 26. In such a manner, therefore,
individual ones of the core elements which are transferred from the
channels in the housing 60 will roll by gravity toward, and be deposited
in, the lift cradle 80.
The lift assembly 26 includes a vertically oriented support column 82 which
supports a cradle housing unit 84 coupled operatively to a linear bearing
member 85. The cradle housing unit 84 is also coupled operatively to a
pneumatic cylinder 88. The lift cradle 80 is fixed to a rotatable support
shaft 90 by means of a blind bolt 80a (see FIGS. 9A-9B). The support shaft
90 is, in turn, cantilevered from the cradle housing unit 84. As such, the
support shaft 90 and the affixed lift cradle 80 can be lifted as a
cantilevered unit in response to pneumatic-assisted (e.g., via cylinder
88) ascension of the drive unit 84 along the linear bearing 85 of support
column 82. The lift cradle 80 is biased by spring 80b (see FIGS. 9A-9B) so
as to normally be in its core lifting position (as shown in FIGS. 6 and
9A), but is pivotal about the axis of shaft 90 against the bias force of
spring 80b so as to assume a core-discharging position (see FIG. 9B). In
this regard, the upper end of the support column 82 is provided with a
generally U-shaped stop element 92 which contacts a bearing element 94
fixed along the upper edge of the lift cradle 80. Upon contact between the
stop and bearing elements 92, 94, continued upward movement of the cradle
housing unit 84 will therefore cause the lift cradle 80 to rotate
clockwise as viewed in FIG. 6 so as to discharge the core element C
carried thereby onto the downwardly inclined bridge plate 96.
The bridge plate 96 is provided with a longitudinally separated (relative
to the longitudinal axis of the core elements) series of pivotal stop
elements 98 which are normally in their raised position as shown in FIG.
6. While in their raised position, the stop elements 98 prevent the core
element on the bridge plate 96 from rolling by gravity into the inlet
chute defined between the guide plates 20e, 20f. However, upon concurrent
actuation of respective pneumatic cylinders (only one of which is shown in
the accompanying drawing FIGURES by reference numeral 98a) associated with
each of the stop elements 98, the stop elements 98 will pivot
simultaneously into their lowered position in which the stop elements 98
no longer impede the progress of the core element C on bridge plate 96.
When in their lowered position, therefore, the stop elements 98 will then
allow the core element C to roll by gravity into the chute defined between
the guide plates 20e, 20f and then on to the space 20d of the feed tray
assembly 20.
The operation of the apparatus 10 according to the present invention will
be described with particular reference to accompanying FIGS. 7A-12B,
inclusive. Specifically, FIG. 7A shows the state of the apparatus 10
whereby a stack of core elements C in one of the channels 60b defined
between partitions 60a within housing 60 is in registry with the input
slot 64 of the platform frame 62. In this state, the transfer gate 66 is
in a stand-by position such that its U-shaped transfer pocket 66b receives
the lowermost one of the core elements C in the registered stack. The
actuator rod 66a' of the hydraulic actuator 66a is eccentrically attached
to the transfer gate 66 via linkage 66c.
As depicted in FIG. 7B, upon actuation of the hydraulic actuator (which
occurs by issuance of a command signal from the controller in response to
receiving a signal from the high position sensor 54b indicating that the
interior space 20d of the feed tray assembly 20 may accommodate a core
element C), the actuator rod 66a' will retract thereby causing the
transfer gate 66 to rotate about shaft 66b due to the mechanical link
provided by linkage 66c until the pocket 66b is oriented with the input
end 68a of the transfer tray 68. In such a state, therefore, a core
element C will be carried by the pocket 66b of the gate 66 and transferred
onto the downwardly inclined transfer tray 68. It will also be observed
that, while the transfer gate 66 is in the position depicted in FIG. 7B,
the arcuately convex bearing surface 66e effectively closes the input slot
64 of the frame 62 so as to prevent entry of the next sequential core
element C in the stack. Upon transfer of the core element C onto the
transfer tray 68, the actuator 66a will again be operated so as to cause
the actuator rod 66a' to extend and thereby return the transfer gate 66 to
the position depicted in FIG. 7A. When in that position, the next
sequential one of the core elements C in the stack will then drop by
gravity into the gate's transfer pocket 66b (i.e., since the bearing
surface 66e of the gate 66 will have then moved into a position to open
the input slot 64).
The core element C transferred onto the transfer tray 68 will then roll by
gravity toward the tray's discharge end 68b and into a cradled position
within the lift cradle 80 as shown in FIG. 8. Sequential logic timers
within the controller (not shown) will thereafter time out causing a
signal to be issued causing the cylinder 88 to be actuated. Upon actuation
of the cylinder 88, therefore, the cradle housing unit 84 will ascend the
support column 82 by virtue of the mechanical connection between the
cradle housing unit 84 and the linear bearing 85 thereby upwardly carrying
the lift cradle 84 and the core element C cradled thereby.
Upon nearing the upper end of the support column 82, the bearing element 94
will come into contact with fixed-position stop element 92 as shown in
FIG. 9A. At this time, however, the cradle housing unit 84 (and hence the
support shaft 90) will continue to move upwardly along the linear bearing
85 of the support column 82. Such continued upward movement of the cradle
housing unit 84 will thereby cause the lift cradle 80 to rotate with the
support shaft 90 about the support shaft's longitudinal axis (i.e., in a
clockwise direction as viewed in FIG. 9A). At the extent of its upward
travel, therefore, the cradle housing unit 84 will be positioned as shown
in FIG. 9B such that the lift cradle 80 has pivoted to such an extent that
the core element C cradled thereby rolls by gravity onto the bridge plate
96 until the rolling movement of the core element C is impeded by the stop
elements 98. Sequential logic timers associated with the controller (not
shown) will thereafter time out causing the controller to issue a signal
to actuate the pneumatic alignment ram 100. Actuation of the pneumatic ram
100 will cause the core element C to move laterally against the stop
element 102 (i.e., outwardly of the plane of FIG. 9B) so as to ensure that
the lengthwise positioning of the core element C is in alignment with the
inlet chute defined between guide plates 20e, 20f. The controller will
also issue a signal to the cylinder 88 which responsively causes the
cradle housing unit 84 to descend the support column 82. It will be noted
in this regard that, as the cradle housing unit 84 descends, the bias
force of the tension spring 80b will pivotally return the lift cradle 80
to its position as shown in FIG. 9A. With the core element C properly
positioned on the bridge plate 96, the controller will then issue a signal
which causes the pneumatic cylinders 98a to operate thereby pivotally
moving their respective stop elements 98 from their raised position and
into their lowered position below the plane of the bridge plate 96 as
shown in FIG. 10A. It will also be observed that the stop element 98
includes a rearwardly projecting spur element 98b which contacts the core
element C upon pivotal movement of the stop element 98 to its lowered
position and thereby provides a gentle forward push to the core element C.
The core element C is thus encouraged by the contact with the spur element
98b to then roll by gravity into the inlet chute between the guide plates
20e, 20f and on to the interior space 20d of the feed tray assembly 20.
The thus transported core element C will then be the last core element C in
sequence positioned within the interior space 20d of the feed tray
assembly 20. The high position sensor 54b will then sense the presence of
the last core element C within the interior space 20d which will allow the
controller to issue a signal to operate an air cylinder or other motive
means (not shown) connected to the finger support collar 56b. Operation of
the air cylinder or other motive means will, in turn, cause the alignment
fingers 56 to move within their respective slots from their upper position
(as shown in FIG. 10A) and into their lower position (as shown in FIG.
10B) by virtue of the collars 56b being rectilinearly slidable along guide
rods 56c. In such a manner, the last core element which had just
previously been transported into the interior space 20d of the feed tray
assembly 20 will be properly aligned in parallel with all of the other
core elements C therein.
The description of the operational sequences above has concentrated on the
transportation of a core element from the magazine assembly 24 to the feed
tray assembly 20. Such a transfer operation is initiated, however, by the
controller in response to the next sequential (lowermost) core element C
in the feed tray assembly being transferred to the cradle assemblies
18a-18d which thereby creates a void below the high position sensor 54b.
As noted previously, when the sensor 54b senses the absence of a core
element C therebelow, the core transfer operation as described previously
will be initiated so that a core element is transferred from the magazine
assembly 24 to the feed tray assembly 20.
The operational sequence for transferring the next sequential one of the
core elements C from the feed tray assembly 20 and into the cradle
assemblies 18a-18c is depicted in accompanying FIGS. 11A-11B. In this
regard, however, it will be understood that only cradle assembly 18a is
depicted in FIGS. 11A-11B for clarity of presentation. The operational
sequences to be described below in relation to cradle assembly 18a,
however, are equally applicable to the cradle assemblies 18b and 18c.
As depicted in FIG. 11A, the feed gate 28a is normally configured in its
stop position where it blocks the entrance to the cradle assembly 18a.
While in the stop position, therefore, the lowermost one of the core
elements C in the feed tray assembly 20 is prevented from rolling by
gravity into position within the cradle assembly 18a. Upon issuance of a
command signal from the controller, the actuation cylinder 32a will be
operated so as to cause the shaft 30a, and hence the feed gate 28a, to
retract to the position shown in FIG. 11B. While in its retracted
position, therefore, the feed gate 28a will allow the lowermost one of the
core elements C in the feed tray assembly 20 to roll by gravity into the
cradle assembly 18a.
It will be recalled that the core element C' is being continuously rotated
about its longitudinal axis and linearly translated through the
melt-blowing section 12. Thus, at some point in time the rearward end of
the core element C' will be positioned physically within the barrel 102
(see FIG. 1). Thus the feed gates 28a-28c are moved simultaneously from
their stop (extended) positions and into their retracted positions by a
signal issued from the controller. The controller-issued signal is, in
turn, initiated by a proximity sensor (not shown) detecting that the
rearward end of the core element C' is physically within the barrel
assembly 102 which is thereby indicative of the cradle assemblies 18a-18c
then being able to accommodate the next sequential one of the core
elements C in the feed tray assembly 20.
It will be observed in FIGS. 11A and 11B that the terminal edge of the feed
gate 28a is beveled. The beveled edge thereby assists the feed gate 28a in
returning to its stop position by encouraging the stand-by supply of core
elements C not supported by the cradle assemblies 18a-18c to roll upwardly
against the force of gravity. In such a manner, therefore, the stand-by
supply of core elements C within the feed tray 20 is physically separated
from that one of the core elements C supported by the cradle assemblies
18a-18c. Movement of the feed gate 28a from its retracted position and
into its stop (extended) position occurs when a proximity sensor (not
shown) senses the presence of the core element C within the cradle
assembly 18a. Thus, upon moving into its stop position, the beveled edge
of the feed gate 28a will act as a cam surface of sorts to urge the stack
of core elements C remaining on the tray 20a upwardly against the force of
gravity within the feed assembly 20.
Upon return of the feed gate 28a to its stop position as shown in FIG. 11B,
the controller will then issue a signal to the motorized spindle assembly
22 so as to join the axially opposed ends of the core elements C and C'
one to another. Accompanying FIGS. 12A and 12B schematically show the
operational sequence of the spindle assembly 22 to integrally join via
friction weld the core elements C and C'.
Specifically, as noted above and as shown in FIG. 12A, the motorized
spindle assembly 22 is normally positioned in axially spaced alignment
relative to the core element C when the core element C is received in the
cradle assemblies 18a-18c. At this time, the rearward end of the core
element C' is positioned physically within the barrel 102 as described
previously. Upon receipt of the command signal from the controller, the
spindle assembly 22 will be advanced toward the core element C by
actuation of the cylinder 44 such that the spindle 42 is inserted
physically within the rearward end of the core element C. In this regard,
the spindle 42 is sized and configured so that it may be inserted within
the rearward end of the core element C with little or no frictional
engagement therebetween. Advancement of the spindle assembly 22 will
thereby linearly advance the core element C within the cradle assemblies
18a-18c until the forward end of the core element C abuttingly contacts
the rearward end of the core element C'. At this time, the inflatable
bladder elements 42a are expanded by the introduction of pressurized fluid
(e.g., air) through conduit 42b. The inflated bladder elements 42a thus
frictionally grip the interior surface of the core element C so as to
effect mechanical union between the spindle 42 and the core element C as
shown in FIG. 12B.
Once the forward end of the core element C and the rearward end of core
element C' have been abutted and the bladder elements 42a inflated, the
controller will issue a signal to the motor 50 so as to rotate the core
element C at a relatively higher speed as compared to the rotation speed
of the core element C'. This relative high speed rotation thereby
generates sufficient frictional heat at the interface C.sub.i between the
core elements C and C' to at least partially plasticize or melt the
thermoplastic material thereat. This at least partially plasticized or
melted thermoplastic material thereby coalesces or melds at the interface
C.sub.i.
After a sufficient time period has elapsed, the relatively high speed
rotation of the spindle 42 is terminated (i.e., by the controller issuing
a stop signal to the motor 50 and the bladder elements 42a being vented to
the abient environment). Upon termination of such relatively high speed
rotation, the at least partially plasticized or melted thermoplastic
material at the interface C.sub.i solidifies quickly so as to create a
friction weld between the core elements C and C'. In such a manner, the
core elements C and C' are joined integrally as a unit and as such may
then be rotated and linearly translated through the melt-blowing section
12 by the drive means associated therewi | | |
