Note: Descriptions are shown in the official language in which they were submitted.
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Method and Apparatus for Vibration Welding of
Thermoplastic Components
Field of the Invention
This invention relates generally to assembly
methods for thermoplastic components and more particularly
to methods and apparatus for manufacturing window and door
frames using vibration welding techniques.
Background of the Invention
At present, plastic window and door frames are
typically assembled from polyvinyl chloride (PVC) extruded
profiles using hot plate welding technology. Typically, the
corner welding process involves pressing the mitered cut
ends of two profiles against a Teflon-coated heated metal
plate. After the thermoplastic PVC material has melted, the
heated metal plate is removed and the two ends are then
pressured against each other forming a hermetically sealed
welded bond. Typically, in manufacturing a four sided frame
assembly either one-head, two-head or four-head welding
equipment is used. For four-head welding equipment, the
complete frame is assembled in one operation and, taking
into account the time required for frame set-up, profile
loading, corner welding, cool down and frame unloading, the
total cycle time is about two minutes.
As well as being a comparatively slow process, a
further drawback of hot plate welding is that a large
quantity of plastic flash is created at the weld line and
this plastic flash has to be mechanically removed through a
process that can involve cutting, shaving and routing
operations. Generally, the equipment required for flash
removal is complex and expensive and the process can also
damage any surface coatings applied to the extruded
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profiles. In addition because the plastic flash material is
contaminated during the welding process, the removed waste
material cannot be recycled and the contaminated material
can also effect the final weld strength. Finally, in order
to consistently achieve a square right angled square corner,
the equipment incorporates elaborate and complex mechanical
support systems.
Vibration welding is one commonly used method for
welding together the flat surfaced end walls of two
thermoplastic components. As described in US Patent
4,352,711, the typical vibration welding process involves
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one component being held firmly in place in a stationary bottom fixture while
a
second component is firmly held in place in a moveable top fixture. By
applying
pressure and moving the top fixture very rapidly, heat is generated through
surface friction, in a very short period of time, that melts the two contact
surfaces
of components that are to be welded together and thus in addition to a short
cycle
time, a further key advantage of vibration welding is that minimum flash is
generated so that the need for mechanical flash removal can be substantially
reduced. Generally, the two plastic component parts are injection molded and
this
allows for flash dams and other features to be incorporated into the
components.
1 o As a result, even with the limited flash that is generated, its movement
and
location is controlled so that it is not visually obtrusive or unsightly.
Various efforts have been made in the past to use vibration welding
techniques for plastic frame assembly but without commercial success. In US
patent 5,902,657, issued to Hanson et al, two alternative processes are
described
that are specifically developed for manufacturing window and door frames. One
technique uses an apparatus similar to a conventional hot plate welder where a
vibratory metal plate rapidly moves back forth between the ends of two
profiles.
To create a welded joint, the metal plate is then removed and the two profiles
are
pressed against each other. As described, there are some technical issues with
this process because unlike conventional hot plate welding, only a thin
surface
layer is heated and as a result, when the vibratory metal plate is moved away,
the
small amount of surface plastic material that has been melted is either
removed
and / or rapidly cools down so that when the two profiles are finally pressed
together the welded bond formed between the two profiles is poor.
There are also some technical concerns with the second alternative
process described in US Patent 5,902,657. With this method for a four-sided
frame, two opposite sides are held fixed in position while the other two sides
are
moveable. The moveable sides are held in fixtures that are connected to four
vibratory heads that are located at profile corner ends when directly welding
3 o together two hollow thin wall profiles. Because the vibratory head moves
back
and forth very rapidly, it is very difficult to accurately control the final
position of the
vibratory head and so consequently the thin profile walls are not correctly
aligned
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and this results in reduced corner weld strength as well as
an uneven joint line which is visually noticeable.
With vibration welding, there is typically a
minimum zone of disturbance at the weld line. However, for
glass fiber re-enforced plastics as described in US Patent
5,874,146 by Kagan et al, higher structural strengths can be
achieved with a wide weld zone that allows for some of the
glass fibers to orient away from the flow direction and to
cross the weld interface.
Summary of the Invention
According to one aspect of the present invention,
there is provided a method for forming a vibratory welded
connection between first and second members and a junction
piece where said members and said junction piece are
composed at least in part of thermoplastic material, said
method comprising providing a vibratory head; providing said
junction piece having a first portion for welding to said
first and second members and a second portion extending from
said first portion for mounting to a fixture connected to
said vibratory head and for supporting said first portion
from said fixture; mounting the second portion of said
junction piece to said fixture connected to said vibratory
head; mounting said first and second members in fixtures
that are independent of said vibratory head; creating an
engagement force between said first member and one side of
said first portion of said junction piece and an engagement
force between said second member and an opposite side of
said first portion of said junction piece; maintaining said
engagement forces while vibrating said junction piece by
means of said vibratory head at a frequency of from 50 to
500 Hz to create friction generated heat to melt material on
the ends of said members and on each respective opposite
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side of the first portion of said junction piece, such
melted material upon cooling forming a weld between said
junction piece and said members; and where said engagement
forces between said first and second members and said
junction piece are applied separately from the operation of
the vibratory head.
Preferably the engagement forces provide even
pressure on each side of the junction piece. The engagement
forces desirably are varied in the duration of the welding
step such that after the desired degree of melting of the
materials of the engaging faces has been achieved, each
engagement force is reduced to a level wherein the melted
material remains molten in position between the ends of the
members and the junction piece.
Preferably the junction piece has a planar flange
that extends at an angle with respect to each of the
members, the junction piece incorporating a removable tab
that is an extension of the planar flange. The tab is held
in the fixture connected to the vibratory head, and after
the welding step has been completed it is removed. The tab
preferably has a geometric shape that is held in the fixture
in an insert hole with a similar geometric shape, e.g. T-
shaped, the junction piece being held firmly in position by
means of metal spring attachments or the like.
Alternatively, the junction piece can incorporate insert
holes for engagement by insert pins on the fixture to secure
the junction piece in position.
For a particular application, the vibratory corner
welding process is controlled by adjusting the duration of
the operation of the vibratory head for a specified
amplitude, frequency, and engagement force.
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According to another aspect, the invention
provides an apparatus for forming a vibratory welded
connection between end faces of first and second members and
a junction piece, and where said members and said junction
5 piece are composed at least in part of a thermoplastic
material, said apparatus comprising: a) a vibratory head
including a drive for vibrating said head in a predetermined
plane at a frequency of from 50 to 500 Hz; b) opposed first
and second fixtures each having clamping structure for
securing thereon a respective one of said first and second
members and where said first and second fixtures support
said first and second members for movement independently of
said vibratory head; c) a third fixture connected to said
vibratory head for holding said junction piece, wherein said
junction piece comprises a first portion for welding to the
ends of said first and second members, and a second portion
extending from and for supporting said first portion, and
wherein said third fixture is adapted for holding said
second portion of said junction piece and is positioned to
allow said first portion to engage said end faces when said
second portion is held by said third fixture; d) guide
structure for guiding relative movement between said members
and said junction piece in a direction perpendicular to said
end faces such as to facilitate engagement between opposite
sides of said junction piece and said first and second
members respectively; e) pressure actuators coupled to
first and second fixtures to provide an engagement force
between opposite sides of said junction piece and said first
and second members; and f) a control system to regulate the
operation of the vibration welding apparatus.
Preferably there are adjustment mechanisms
associated with each pressure actuator whereby the
engagement force provided by each pressure actuator is
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independently adjustable. In this way, a variable force of
engagement can be provided through the duration of the
welding step.
The third fixture which holds the junction piece
is preferably located so that the planar flange of the
junction piece is balanced and positioned typically in a
central location, with the first and second fixtures being
movable independently of this third fixture.
The invention also contemplates a system for
interconnecting a series of elongate frame members to form a
closed frame. In this system adjacent ends of adjoining
frame members are engaged by use of the aforesaid apparatus.
The frame member can be a rectangular frame, a set of
apparatuses aforesaid being provided at each of the four
corners of the frame.
The framing members need not be assembled at right
angles, but can in fact be connected at any selected angle
in the range 90° to 15°. The angles of adjoining frame
members with respect to the junction piece can also be
different. Nor is it essential that the framing members be
straight, but on the contrary, one or more of the framing
members may be longitudinally curved.
The system for interconnecting the frame members
can be used to assemble those members around an inner panel
prior to the frame members being welded together to form a
complete assembly with the panel. The panel can be of any
desired composition such as a sheet of glass or rigid
plastics material, an insulating glazing unit, a multi-
cavity sheet extrusion, or the like.
According to another aspect of the invention,
there is provided a frame comprising a plurality of elongate
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frame members, adjacent ends of pairs of said members being
interconnected through an interposed junction piece, wherein
said frame members and said junction piece are each composed
at least in part of a thermoplastic material, wherein each
said junction piece is secured to a pair of adjacent frame
members by vibratory welded bonds on opposite sides of said
junction piece, and wherein said junction piece has a planar
flange that extends at an angle with respect to each said
frame member.
Preferably each hollow profile has a peripheral
wall that provides a surface for welding to the planar
flange. The hollow profile of the frame members can be
subdivided into two or more cavities.
Preferably the planar flange has a thickness in
the range of 2 mm to 12 mm and preferably 3 mm to 6 mm.
The flat surfaces of the planar flange may
incorporate a textured surface finish to improve the build-
up of friction generated heat.
The frame members are preferably composed of glass
fiber reinforced thermoplastic material, such as polyvinyl
chloride. The frame members can have decorative coatings or
finishes incorporated on their outer surfaces.
The junction piece may preferably carry integral
legs that extend from opposite sides of the planar flange,
the legs being sized to engage longitudinally within the
hollow interiors of the adjacent frame members. The
integral legs of the junction piece may incorporate each an
integral spring centering device. Furthermore the hollow
frame profile members can be fixed to the legs of the
junction pieces by ultrasonic spot welding at locations
spaced from the planar flange.
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Preferably the ends of the framing profiles are
miter cut to provide the desired corner angle of the frame,
e.g. a miter cut at 45° to provide a 90° corner. The miter
cut ends of the framing profiles may be formed with a so-
y called dado cut (open sided groove) and a pressure plate can
be applied on the miter cut ends of the front face of the
framing profile during the welding process to prevent the
appearance of this front face being marred by any welding
flash.
The junction piece can incorporate devices such as
traps, grooves or welding beads for locating or receiving
plastic flash generated during the vibratory welding
process.
There are three preferred applications for the vibration
corner welding process, namely: (i) where frame members are
assembled around an insulating glass unit and where silicone
sealant is applied in gaps between the assembled frame and
the insulating glass unit; (ii) where glazing sheets are
directly adhered to the sides of a frame assembly using
silicone sealant, and (iii) where an assembled frame is
located between spaced glazing sheets.
According to another aspect of the present
invention, there is provided a method of forming a framed
panel, comprising the steps of: (a) providing a panel to be
framed; (b) providing a plurality of frame members for
framing said panel, each frame member having a channel
formed therein for receiving an edge portion of said panel,
each frame member comprising at least in part thermoplastic
material; (c) inserting said panel into the channel of each
frame member such that said panel is spaced apart from said
frame member; providing a junction piece for joining
adjacent ends of each frame member, each junction piece
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comprising at least in part a thermoplastic material and
having a first portion for welding to adjacent frame members
and a second portion extending from said first portion for
mounting to a fixture connected to a vibratory head and for
supporting said first portion from said fixture; mounting
the second portion of said junction piece to said fixture
connected to said vibratory head; mounting adjacent frame
members in fixtures that are independent of said vibratory
head; creating an engagement force between a member and one
side of said first portion of said junction piece and an
engagement force between an adjacent member and an opposite
side of said first portion of said junction piece;
maintaining said engagement forces while vibrating said
junction piece by means of said vibratory head to create
friction generated heat to melt material on the ends of said
adjacent frame members and on each respective opposite side
of the first portion of said junction piece, such melted
material upon cooling forming a weld between said junction
piece and said frame members; and where said engagement
forces between said adjacent frame members and said junction
piece are applied separately from the operation of said
vibratory head.
Brief Description of the Drawings
The following is a description by way of example
of certain embodiments of the present invention, reference
being made to the accompanying drawings, in which:
Figures lA and 1B are elevation views of a frame
corner assembly fabricated from square profile, glass fiber
filled PVC extrusions and welded at the corner using
conventional hot plate welding technology.
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Figure 2 is a vertical cross section taken on the
line 2A-2A in Figure 1B through a corner assembly.
Figure 3 is an elevation view of the test fixture
for the thermoplastic corner test as specified in the North
American Fenestration Standard (NAFS-1).
Figure 4 is an exploded perspective detail of a
frame corner assembly incorporating a removable tab on the
outer side edge where the thermoplastic extrusions are
vibration welded at the corners to a diagonal corner web
Figure 5 is a horizontal cross section of a frame
corner assembly where the thermoplastic extrusions are
vibration welded to a diagonal planar flange junction piece
incorporating a removable tab on the outer side edge.
Figure 6A is a perspective view of a single corner
vibration welding apparatus.
Figure 6B is a schematic diagram of the control
system for a single corner friction welding apparatus.
Figure 7A is a plan view of a single corner,
vibration welding apparatus with the extrusions installed in
the fixtures prior to the welding process.
Figure 7B is a view similar to Figure 7A showing
the single corner vibration welding apparatus during the
welding process.
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Figure 8A is an exploded perspective view and Figure 8B is a
perspective view of a vibration welded corner frame assembly incorporating a
junction piece with a planar flange and a removable tab on the bottom edge.
Figure 9A is a cross section detail of a planar flange web
incorporating flash traps.
Figure 9B is a cross section detail of a planar flange web
incorporating welding beads.
Figure 10 is a cross section detail of the moveable fixtures that hold
the framing profiles in position during the vibration welding process.
1o Figure 11 is a perspective view of a junction piece with a planar
flange and a removable T-shaped tab on the outer side edge.
Figure 12A is a perspective detail of a junction piece with a planar
flange and incorporating a removable tab with a double set of L-shaped slots
on
the back edge.
Figure 12B is an exploded top elevation view of a junction piece
holding fixture and a planar flange junction piece web as shown in Figure 12A.
Figure 12C is a vertical cross section of the junction piece holding
fixture with a planar flange junction piece as shown in Figure 12B.
Figure 13 is a perspective view of a corner web with a removable tab
2 0 on the bottom edge.
Figure 14A is a top plan view of a junction piece fixture incorporating
a separate pressure strip device.
Figure 14B is a vertical cross section detail of a corner web fixture
incorporating a separate pressure strip device.
Figure 15A is a cross section plan view detail of a frame corner
assembly where the thermoplastic plastic extrusions are vibration welded at
the
corner using a corner key with a diagonal web and integral legs.
Figure 15B is a cross section detail of the frame corner assembly as
shown in Figure15A where the plastic framing profile is ultrasonically spot
welded
3 o to the integral legs of the corner key.
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Figure 15C is a cross section and elevation detail of the plastic
framing profile and corner key as shown in Figure 15A.
Figure 16 is a fragmentary plan view of vibration welding apparatus
showing that the framing profiles can be assembled at varying angles to the
planar
flange junction piece.
Figure 17A is an elevation view of a round top window frame.
Figure 17B is a cross section detail of a butt joint assembly between
a straight and curved framing profile.
Figure 18 is an exploded perspective view of a vibration welded
1 o corner frame assembly incorporating a junction piece with a planar flange
and a
top held removable tab.
Figure 19A and 19B are elevation views of a vertical four head
vibration welding apparatus featuring two stage frame assembly.
Figure 20 is an elevation view of a vertical four head vibration
welding apparatus where all four corners are simultaneously welded.
Figure 21A is an elevation view of a composite channel sash window
panel with the thermoplastic framing profiles assembled using vibration corner
welding.
Figure 21 B is a vertical cross section detail taken on a line 21A - 21A
2o in Figure 21A of a composite channel window panel incorporating a double
glazed
insulating unit.
Figure 22 is an exploded perspective view of a composite channel
frame being assembled around an insulating glass unit using vibration corner
welding.
Figure 23B is a perspective view of a corner assembly of a
composite channel window incorporating different size framing profiles and
assembled using vibration corner welding.
Figure 24A is a perspective view of a vibration welded composite
channel frame assembly where the framing profiles incorporate a single I-
shaped
cavity and thin solid frame profile walls for supporting the insulating glass
unit.
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Figure 24B is an exploded top view of the corner
frame assembly shown in Figure 24A.
Figure 25A is an elevation view of an insulating
glass panel with a rigid thermoplastic spacer frame
5 assembled using vibration corner welding.
Figure 25B is a vertical cross section detail
taken on a line 25A-25A in Figure 25A of the insulating
glass panel incorporating a rigid thermoplastic spacer
frame.
10 Figure 26A is an elevation view of a sealed frame
window panel where the outer glazing sheets are directly
adhered to the frame assembly.
Figure 26B is a vertical cross section detail
taken on a line 26A -26A in Figure 26A of a sealed frame
window panel as shown in Figure 26A.
Figure 27A and 27B are front and side elevation
views of a corner end of a framing profile specifically
fabricated for friction corner welding of sealed frame
panels.
Figure 28 is an exploded perspective detail of a
corner frame assembly for a sealed frame window panel as
shown in Figure 26A.
Figures 29A to 29E are details of the production
steps involved in the sealed frame corner assembly using a
combination of friction welding and ultrasonic spot welding
techniques.
Figure 30 is a perspective view of a junction
piece with a removable tab incorporating insert holes for
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engagement by insert pins that form part of the junction
piece holding fixture.
Detailed Description of the Preferred Embodiments
Referring to the drawings Figures 1A and 1B show
side and front elevations of a frame corner assembly 31
comprising frame members 32, 33 fabricated from square
hollow profile, glass fiber filled PVC extrusions. The
miter cut corner ends 34 of the frame members 32 and 33 are
welded together using conventional hot plate equipment. One
major drawback of hot plate welding is that a large quantity
of plastic flash 35 is created at the weld line 36. This
plastic flash 35 has to be mechanically removed and this
process often involves removing a shallow groove at the weld
line 36. As a result of this mechanical removal process,
the structural performance of the corner weld can be quite
significantly reduced.
Figure 2 shows a vertical cross section on a line
2A - 2A through he frame corner assembly 31 where the miter
cut ends 34 of the frame members 32 and 33 are welded
together at the perimeter wall edge. As previously
described this process creates plastic flash 35 that has to
be mechanically removed from the profile exterior.
In North America, the structural performance of
thermoplastic corner welds are evaluated according to the
North American Fenestration Standard (NAFS-1) test
procedure. As shown in Figure 3, the test procedure
involves attaching a welded frame corner assembly 31 to a
support 39 with clamps 40 and 41. The bottom clamp 41 is
located 100 mm above the top edge 42 of the lower frame
member (profile) 33. A point load L 44 is gradually applied
to the lower frame member (profile) 33 with this load 44
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being located at a distance of 360 mm from the front side
edge 45 of the upper frame member (profile) 32. The pass /
fail test criterion is that when loaded to failure, the
break shall not extend along the entire weld line 36.
Using conventional hot plate welding technology,
corner weld test samples as shown in Figure 2 were
fabricated from 30 per cent glass fiber filled PVC
extrusions. The samples were tested according to NAFS-1
procedure and the samples failed with the break extending
fully along the weld line 36. The main reason that the
fiber filled material failed the NAFS test procedure is that
the weld strength is typically no higher than the base
matrix polymer and as a result, because the 30 per cent
glass fiber filled profiles are stronger and stiffer, the
joint is the weak link in the frame assembly.
As described in detail with reference to Figures
4-30, one of the main purpose of this invention is to
provide a corner frame assembly method where the test
samples fabricated from 30 per cent glass fiber filled PVC
extrusions, consistently pass the NAFS-1 Thermoplastic
Corner Weld test procedure.
Figure 4 shows an exploded perspective view of
corner frame assembly where the miter cut ends 34 of
thermoplastic framing member 32 and 33 are vibration welded
to opposite sides of a junction piece 47 incorporating a
planar flange 48 and a removable tab 49. The junction piece
47 is made from the same
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base polymer as the thermoplastic framing members 32 and 33. The planar
flange 48 incorporates a rough or textured surface and because this surface
treatment accelerates the generation of friction heat, the weld cycle time is
substantially reduced. The wall thickness of the planar flange 48 can vary
between 2 mm to 12 mm with the preferred range being 3 to 5 mm. The
removable tab 49 is thicker than the planar flange 48 and this provides for
increased strength and stiffness. After the welding process is complete, the
removable tab 49 is cut off using a shear press or similar device. Because the
vibration welding does not contaminate the plastic weld material, this
removable
1 o tab can be recycled and the plastic resin reused.
Figure 5 shows a horizontal cross section through the fabricated
corner frame assembly from hollow plastic profiles 32 and 33. Because the
framing members 32 and 33 are vibration welded to either side of the junction
piece 47, the structural loads at each of the two welds is reduced
accordingly. In
addition, the planar flange 48 provides for diagonal corner bracing, further
increasing the structural performance of the frame assembly.
A removable tab 49 that forms an extension of the planar flange 48
is located on the outer side back of the junction piece 47. During the
vibration
welding process, this tab 49 is firmly held in a holding fixture 50 linked to
the
2o vibratory head 52 of the special vibration welding apparatus 51 as
described in
Figures 6A, 6B and 7A, 7B.
A corner test sample was fabricated using the same hollow square
profile PVC extrusions with 30 per cent glass content as the samples that had
been previously made using conventional hot plate welding equipment. The
profile samples were welded to the planar flange using the special vibration
welding techniques but unlike the hot plate welded test samples, these
vibration
welded test samples passed the NAFS-1 Thermoplastic Corner Weld test
procedure.
As shown in Figure 5, the vibration welding process generally results
3 o in the plastic framing profiles 32 and 33 being embedded in the planar
flange 48.
Although it is desirable that the planar flange is made from the same resin-
based
material as the framing profiles, one option is for the junction piece to be
made
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from a stiffer plastic material (e. g. glass fiber filled
material) so that the profiles are not excessively embedded
within the planar flange.
Figure 6A shows a top perspective view of a
prototype single corner vibration welding apparatus 51. The
apparatus consists of five main components:
1. Vibratorv Head
A linear vibratory head 52 that incorporates a
top plate 53 which vibrates back and forth very rapidly in
a predetermined plane.
2. Junction Piece Holding Fixture
A junction piece holding fixture 50 is directly
attached to the top plate 53 and firmly holds the planar
flange junction piece 48 in position.
3. Moveable Framing Fixtures
Two moveable framing fixtures 55 and 56
incorporate clamping devices 60 that firmly hold the framing
profiles in position. The movement of the framing fixtures
55 and 56 is operated through a variety of means including:
electrical servo motors, pneumatic and hydraulic devices.
4. Control Systems
A control system 46 that regulates the various
operating parameters of the vibration welding apparatus
including: weld time, hold time, joint pressure, amplitude,
frequency and voltage. The control system is located in a
protective housing and is linked to an operator interface
64.
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5. Machine Frame
A machine frame 65 provides the structure that
supports the other components.
The vibratory head 52 can move in either a linear
or orbital manner. With linear vibration welding, the
vibratory head moves back and forth very rapidly in a
predetermined plane. While with orbital vibration, the
vibratory head continuously rotates in a circular operation.
As a continuous process, orbital vibration offers some major
advantages including: reduced time, less energy, less weld
amplitude, reduced clearance and better flash control. At
present, orbital vibration is somewhat less reliable because
the continuous circular motion is driven by an electrical
motor and so only linear vibration welding is illustrated in
the following figures. However, it can be appreciated by
those skilled-in-the-art that orbital vibration welding can
also be substituted for many of these corner welding
applications and specifically, the process offers advantages
where a planar flange junction piece is used.
Figure 7A shows a plan view of a single corner,
vibration welding apparatus 51 in an open position. The
linear vibration welding apparatus 51 features a vibratory
head 52 that linearly moves back and forth in a pre-
determined plane. The vibratory head 52 is similar to the
vibratory heads used on commercially available linear
vibration welders such as the Branson Mini Welder, but
unlike these commercially available products, the vibratory
head is turned upside down as this allows for more flexible
and easy positioning of the framing members 32 and 33 during
the frame assembly process. A flat plate 53 is bolted to
the top surface of the vibratory head 52. As with standard
vibration welders, the vibratory head is bolted to a
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separate heavy cast iron support (not shown) and isolated
from the cast iron support structure (not shown) using
rubber mounts. This cast iron support structure is in turn
bolted to a machine frame 65 that positions the vibratory
5 head 52 at a convenient working height.
Flat plate metal sheets 54 are bolted to the top
surface of the machine frame 65 but this top working surface
is separated apart from the vibratory head 52 so that a
minimum of vibratory movement is transferred to the machine
10 frame 65. Moveable profile fixtures 55 and 56 are supported
on guide rails 57 directly attached to the top table plate
54 and these fixtures hold the framing profiles extrusions
32 and 33 in position. The moveable profile fixtures 55 and
56 move over the vibratory head 52 but there is no direct
15 contact except where the framing profiles 32 and 33 contact
the junction piece 47. The moveable fixtures also allow for
the miter cut ends 34 of the framing profiles 32 and 33 to
be positioned parallel to the planar flange 48 of the
junction piece 47.
Each moveable profile fixture 55 and 56 consists
of a horizontal flat plate 58, a support member 59 that is
attached to the horizontal plate 58 and a clamping fixture
60 that firmly holds the profiles 32 and 33 against the
support member 59. In this embodiment, the clamping fixture
comprises a front clamp 60 positioned adjacent to the side
edge 61 of the flat plate 58 and to ensure that the profile
33 is firmly held in position, the miter cut profiles 32 and
33 only extend 2 or 3 mm beyond the side edge 61. It is
also important that both the profiles extend the same
distance from the two clamping fixtures.
To provide for a right angled joint connection
(i.e. 90°), the vertical support members 59 are positioned
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16
at a 45° angle to side edge 61. However for special framing
shapes, the angular position a of the support member 59 can
be adjusted as required by means of a pivot point 62 and an
attachment device 63. A fixed holding fixture 50 for the
junction piece 47 is located so that the planar flange of
the junction piece is in a balanced central position. The
holding fixture 50 which is directly attached to the top
plate 53 of the vibratory head 52, firmly holds the
removable tab 49 of the junction piece 47 in position.
Figure 7B shows a plan view of the vibration
welding equipment in operation. The miter cut ends 34 of the
profile extrusions 32 and 33 are pressured against the
planar flange 48 of the junction piece 47. As required, the
angular displacement of the profile fixtures 55 and 56 can
be adjusted so that all four joint surfaces are parallel
with each other.
In operation, friction heat is generated at the
two joint interfaces between the parallel surfaces of the
miter cut ends 34 of the framing profiles 32 and 33 and the
planar flange 48 of the junction piece 47. By vibrating the
junction piece 47 back and forth and by simultaneously
pressuring the framing profiles 32 and 33 against the planar
flange 48 of the junction piece 47, friction heat is
generated at the two joint interfaces. When a molten state
is reached at the two joint interfaces 66 and 67, the
vibration is stopped and the perpendicular pressure P is
then maintained briefly while the molten plastic solidifies
to form two welded joints 66 and 67 on either side of the
planar flange 48. In order to provide for even weld
strength, essentially the same perpendicular engagement
force has to be simultaneously applied to each side of the
junction piece 47.
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17
In the vibration welding process, if excessive
pressure is applied after the surface plastic has been
melted, the melted plastic can be pushed away from the joint
line resulting in a poor structural bond. By carefully
controlling the engagement force or pressure of the framing
profiles on the junction piece, this joint bond problem can
be avoided. After the desired degree of melting of the
materials at the joint line has been achieved, the
engagement force is reduced to a level where the melted
material remains molten in position between the ends of the
framing profiles.
In friction welding glass fiber filled profiles,
one of the reasons for reduced weld strength is that the
glass fibers align along the weld line, perpendicular to the
applied engagement force or pressure. This weld zone is
typically very narrow varying from 40 to 100 microns. By
carefully controlling and optimizing the welding parameters
and particularly the applied pressure, a wide weld zone can
be created so that some of the glass fibers are oriented
away from the weld line and cross the weld interface. As a
result, higher weld strengths can be achieved for the glass-
fiber filled profiles.
Using the prototype corner welding apparatus, a
series of experiments have been carried out and these
experiments have shown that satisfactory structural welds
can be achieved by optimizing the different welding
parameters through quite a wide range of different parameter
values. For example, maximum applied pressure can be
reduced if amplitude is increased, or both maximum applied
pressure and amplitude can be reduced if weld-time is
increased. Particularly to reduce the amount of plastic
flash that is produced, our experiments have also shown that
it is preferable to use a higher frequency and a lower
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amplitude. Generally, the different welding parameters can
be varied through the following values although for each
application, there is a need to establish a particular set
of welding parameters.
Maximum applied pressure 6 kN
Weld time 2 - 12 seconds
Weld amplitude 0.4 mm to 3 mm
Weld frequency 50 to 500 Hz
Generally for a particular application, the
vibratory corner welding process is controlled by the weld
time that is determined for a specified weld amplitude,
frequency and maximum applied pressure or engagement force.
It should be noted that weld time is defined as the duration
of the operation of the vibratory head.
Figure 6B is a schematic diagram of the control
system 46 for the single corner vibration welding apparatus
51. The control system 46 consists of a central controller
84 which is protected within metal housing and linked to an
operating interface 45. The controller 84 controls the
operation of five main components: (i) vibratory head 55,
(ii) clamping mechanism 239 and (iii) pressuring mechanism
240 of the first moveable profile fixture 56 and (iv) the
clamping mechanism 241 and (v) pressuring mechanism 242 of
the second moveable profile fixture 56. Through an input /
output information feed, the operations of these five
components can be coordinated and controlled.
Using the prototype single corner vibration corner
equipment as described in Figures 6A, 6B, 7A and 7B, corner
frame profile assemblies have been successfully produced
from a wide variety of different plastic materials,
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including: polyvinyl chloride (PVC); composite glass fiber
filled PVC; cellular foam PVC; composite wood fiber filled
PVC and thermoplastic pultrusions. For all assemblies, it
is desirable that the planar flange junction piece is made
from essentially the same base resin as the framing
profiles. A series of alternative designs for the corner
web have also been tested and our experiments have shown
that satisfactory welds can be produced even with a planar
flange thickness of less than 1.5 mm.
Figures 8A and 8B show an exploded perspective
view of a vibration welded corner frame assembly 31
incorporating a junction piece 47 with a planar flange 48
incorporating a removable tab 49 on the bottom edge. In
contrast to the side held junction piece, one advantage of
the tab on the bottom edge is that the junction pieces are
easier to load into the holding fixture.
For simple corner web designs, the junction pieces
can be die cut from plastic sheet material. Alternatively,
the junction pieces can be injected molded and this has the
advantage that various design features can be incorporated
into the junction piece that essentially eliminate the need
for plastic flash removal. Figures 9A and 9B show two
alternative joint designs that essentially eliminate the
need for mechanical flash removal. In Figure 9A, two
hollow-thermoplastic profiles 32 and 33 are longitudinally
joined together using a junction piece 47 incorporating a
planar flange 48. The junction piece 47 incorporates flash
traps or melt recesses 69 on either side of a central bead
70. During the vibration welding process, plastic flows
into the flash traps 69 creating double parting lines 71.
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As shown in Figure 9B, where the aesthetic requirements are more
demanding, the plastic profiles ends 72 can incorporate a dato cut 73. The
flat cut
ends 75 of the profiles 32 and 33 overlap the planar flange 48 that
incorporates
welding beads 74. During the vibration welding process, plastic flows inwards
around the ends of the junction piece 47 and the two flat cut ends 75 almost
touch, creating a single thin parting line. As previously noted, the main
advantages of using flash traps and welding beads is that the plastic flash is
contained during the welding process and does not have to be mechanically
removed from the surface of the plastic extrusions. As a result, it is
feasible for
decorative surface finishes 76 to be incorporated on the plastic extrusions 32
and
33 because there is no mechanical flash removal, these surface finishes 76 are
not damaged during the welding process. A further advantage of weld beads and
flash traps is that by not having to remove melted plastic flash material,
joint weld
strength can also be increased. Although as shown in Figure 9B, a dato cut is
incorporated into the framing profile, it can be appreciated by those skilled-
in-the-
art, that welding beads can be incorporated into the joint design without the
need
for dato cuts.
For the vibration welding equipment shown in Figures 6A, 6B and
7A, 7B, the framing profiles are held firmly in position by means of a front
clamp
2 0 60. For more complex profile shapes, special custom fixtures have to be
used
and where there is a need for different framing profiles to be welded on the
same
production line, it is necessary for these custom clamps to be changed over.
As a
result, there can be production slow downs and delays which means that the
productivity advantages of vibration corner welding may not be realized.
To eliminate this need for special custom fixtures, Figure 10 shows a
cross section detail of an adjustable clamp 60 for holding the plastic framing
profile 77 firmly in position. A vertical support member 59 is attached to the
moveable horizontal plate 58. The framing profile 77 is held firmly in
position by
means of a double set of flat metal strips 78 and 79 with each strip 81
incorporating a special gripping tip 82. The first set of strips 78 slide into
position
and assume the general profile shape of the front face 80 of the framing
profile 77
so that the profile 77 is held against the vertical support member 59. The
second
set of flat strips 79 then slide into position and assume the general profile
shape
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of the side face 83 of the framing profile 77 so that the framing profile 77
is held
also against the horizontal plate 58. Each set of strips incorporate a locking
system (not shown) that locks the strips into position.
Figure 11 shows a perspective detail of the junction piece holding
fixture 50 for the single corner vibration welding equipment 51. The junction
piece
holding fixture 50 is mechanically attached to the top plate 53 of the
vibratory head
52 (not shown). Because the junction piece holding fixture 50 is vibrated back
and
forth very rapidly, the stresses or shock level on the fixture are very high
and it has
been estimated that these stresses are in excess of 100 G-forces. As a result,
1o mechanical pressure devices to hold the corner key in position are not
suitable as
these pressure devices can not withstand the continual vibration.
As shown in Figure 11, one way of eliminating mechanical pressure
devices is for the removable tab 49 of the junction piece 47 to incorporate a
T-
shaped profile 85 and for the holding fixture 50 to also incorporate a
complementary T-shaped insert hole 86. The junction piece 47 is slid into
position
and the T-shaped profile 85 is held firmly in position by means of metal
spring
attachments (not shown).
Figure 12 illustrates an alternative corner key holding system that
also incorporates no moving parts.
2 o Figures 12A shows a perspective detail of junction piece 47
incorporate a planar flange 48 and a removable tab 49. The back edge 87 of the
removable tab 49 incorporates a double set of L-shaped slots 88.
Figures 12B shows a top view of a junction piece holding fixture 50
and a planar flange junction piece 47 prior to installation of the junction
piece
within the holding fixture. The junction piece holding fixture 50 incorporates
a
narrow slot 89 and the width of this slot 89 is marginally larger than the
width of
the removable tab 49. Two circular metal pegs 90 span across the narrow slot
89.
Figure 12C shows a cross section view of the junction piece holding
fixture 50 prior to installation of the junction piece. In the corner frame
assembly
process, the junction piece 47 is first moved horizontally across so that the
two
circular pegs 90 are engaged within the double set of L-shaped slots 88. The
junction piece is then dropped down into its final position where the circular
pegs
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90 are contained within the circular shaped toe 91 of the L-shaped slots 88.
Compared to the T-shaped junction piece shown in Figure 11, the main advantage
of the double L-shaped slots is that the junction pieces use less material and
so
can be manufactured at a lower cost.
5 Figure 13 shows an exploded perspective view of a junction piece 47
with a planar flange 48 and a removable tab 49 on the bottom edge. The
removable tab 49 incorporates double vertical slots 92 that correspond to
double
circular pegs incorporated into junction piece fixture (not shown). Compared
to
the side held holding system shown in Figure 12, the main advantage is that
the
1o junction pieces are easier to load into the bottom held holding system.
Figure 30 shows a second alternative junction piece holding system
that also incorporates no moving parts. The junction piece 47 incorporates a
planar flange 48 and a removable tab 49. Two insert holes 96 and 97 are
incorporated into the removable tab 49 of the junction piece 47. Complementary
15 insert pins 98 and 99 are incorporated into junction piece holding fixture
50 that is
attached to the top plate 53 of the vibratory head. When the two pins 98 and
99
are inserted into the two holes 96 and 97, the junction piece is held firmly
in
position during the vibration welding process.
Rather than incorporating flash traps and welding beads, an
20 alternative method for controlling plastic flash as shown in Figure 14 is
to apply a
pressure strip device to the weld joint during the vibration welding process.
Figure 14A shows a top plan detail of the corner web fixture
incorporating a separate pressure strip device 95 featuring a non-stick
coating
such as Teflon on the contact surface of the pressure strip 95. The profile
extrusions 32 and 33 are held in position by the moveable framing fixtures 55
and
56. A pressure strip device 95 is attached to a separate support structure 96
and
this support structure is isolated from the vibratory head 52.
Figure 14B shows a vertical cross section detail of the single corner
vibration welding equipment 51 incorporating a separate pressure strip device
95
and a bottom-held planar flange junction piece 48. During the vibration
welding
process, downward pressure is directed on the weld line between the framing
profiles 32 and 33 and as a result, the plastic flow generated during the
welding
process is directed inwards and away from the weld line between the two
profiles.
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As shown in previous figures, the junction piece 47 consists of a
planar flange 48 with a removable tab 49. For certain framing applications,
this
planar flange configuration does not provide for sufficient structural support
and
there is a need for additional corner re-enforcement. As shown in Figure 15,
this
can be achieved by the junction piece or corner key 100 incorporating integral
legs
101.
Figures 15A and15B show a cut out cross section plan view of a
corner frame assembly 31 fabricated from square profile glass fiber filled PVC
profile extrusions 32 and 33 and where the profiles 32 and 33 are welded at
using
a junction piece or L-shaped corner key 100 incorporating integral legs 101.
As shown in Figure 15A, the integral legs 101 of the corner key 100
incorporates an integral spring centering device 102 that simplifies frame
assembly. The planar flange 48 of the corner key 100 is first vibration welded
to
the miter cut ends of the profiles 32 and 33. Because of the need to
accommodate the vibration movement back and forth, the legs 101 only loosely
fit
within the profile.
As shown in Figure 15B in order to provide for additional support, the
plastic framing extrusions are ultrasonically spot welded to the legs of the
corner
key 100. A double tip welding head is typically used creating spot welds 106
and
107. Because the legs only loosely fit within the profile, the ultrasonic
welding
process allows the plastic to flow in the gap between the corner key legs and
the
profile extrusions creating an extra strong welded spot bond and reduced
material
flow on the exterior surface. Because of their complex profile shape, the
corner
2 5 keys 100 are typically injected molded and have to be manufactured from
essentially the same base resin material as the extruded profiles 32 and 33.
One of the main advantages of using ultrasonic spot welding is that it
is an assembly technique that joins two similar thermoplastic components at
localized points with no preformed hole or energy director. In operation, the
spot
welding tips pass through the frame profile wall and the molten plastic
displaced is
shaped by a raised cavity in the tip (not shown) forming a neat, raised ring
on the
surface. Simultaneously, energy is released at the interface producing
frictional
heat. The tip then penetrates the corner key, displacing molten plastic
material
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between the two surtaces and after the plastic has solidified, this forms a
permanent structural bond between the framing profiles and the corner key
legs.
Figure 15C shows a vertical cross-section through the hollow profile
33. The integral legs 101 of the corner key 100 consist of a rigid flat bar
103 with
a central positioning fin 104. The profile extrusion 33 incorporates a half
circular
indentation and this allows the positioning fin 104 to be centrally located.
Figure 16 shows a fragmentary plan of vibratory head 52 of the
single corner friction corner welding apparatus 51 showing framing angle
options.
A junction piece 47 is centrally located and extruded profiles 32 and 33 are
1 o positioned against the vertical support members (not shown) and the
angular
displacement D of these support members can be varied from 90° to
15° and this
allows for special shape frames to be manufactured.
Figure 17A shows an elevation view of a round top window frame
108. The straight framing profiles 109, 110, 111 are miter cut and vibration
welded
at the bottom corners 113 and 114 using planar flange junction pieces 48. At
the
butt joints 115 and 116 between straight framing profiles 109 and 111 and the
round top profile 112, the profiles are straight cut and vibration welded
together
using special junction pieces 117.
Figure 17B shows a cross section detail of the butt joint 115 between
2 0 the straight framing profile 111 and round top or curved framing profile
112. The
junction piece 117 incorporates legs that feature an integral spring centering
device that simplifies the assembly of the window frame.
Figure 18 shows an exploded perspective view of a corner frame
assembly where two framing profiles 32 and 33 are vibration welded to a
junction
piece 47 incorporating a planar flange and with a removable tab located on the
top
edge 119 of the planar flange 48. To provide for simplified handling at the
framing
profiles, the junction piece corner key fixture is typically attached to a
flat plate
located on the top surface of the vibratory head. However, the position of the
vibratory head can be reversed so that the junction piece 47 is held from
above
and particularly for frame-and-panel assemblies, this reversed head position
offers
the advantage that both the panel and the final assembled unit can be more
easily
moved in-and-out of the vibration welding apparatus.
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Although frame assemblies can be manufactured using a single
corner welder, it is more productive if two or more corners are welded
simultaneously. Figure 19A shows a front elevation view of a vertical four
head
vibration welder equipment 120. As with conventional hot plate welding
equipment, the four head welding equipment 120 consists of a rectangular
structural frame 121 with leg supports 122 and 123. The four welding heads
130,131, 132 and 134 are attached to two vertical bridge supports 124 and 125
that span between the top beam 126 and bottom beam 127 of the structural frame
121. The first vertical bridge support 124 is fixed in position while the
second
1 o bridge support 125 is moveable and is driven by a servo motor on a cog
track
located on the bottom beam 127 of the structural frame 121. The top end 129 of
the moveable bridge 125 is supported by a guide rail 128 located on the top
beam 126 of the structural frame121.
A first set of vibration welding heads 130 and 133 are attached to
the first bridge support 124 that is fixed in position and a second set of
vibration.
welding heads 131 and 132 are attached to the second moveable bridge support
125. Each set of vibration welders are operated by a electro servo motor
driven
ball screw that in combination with special control devices allow the vertical
position of each head to be individually controlled so that in operation, all
four
2 0 heads can move up and down either simultaneously or independently towards
a
central horizontal datum line 154. After the four heads 130, 131. 132 and 133
have moved to their initial start location, the four framing profiles 134,
135, 136
and 137 are loaded into position as well as the four junction pieces
138,139,140
and 141.
In contrast to a conventional four point welder where all four corners
are welded simultaneously, the preferred operating strategy for friction
welding is
a two stage process. As shown in Figure 19A, two diagonally opposite corners
150 and 152 are first welded together. For each corner weld, the process is
essentially the same as with a single corner vibration welder. Both sets of
framing
profiles 134, 137 and 135,13'6 are independently pressurized against the two
diagonally opposite corner keys 138 and 140. In addition, only the moveable
frame clamping devices, immediately adjacent to the corner keys 138 and 140
are
in operation. After the welding process is complete, the corner keys 138 and
140
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24
have to be released and by incorporating as part of the vibratory welding head
a
tab removal shear press or a similar device (not shown), this allows for this
release process to be carried out very efficiently.
As shown in Figure 19B, the next step is for the other set of
diagonally opposite corners to be welded together. The bottom head 133 on the
first vertical beam is fixed in position while both the top two heads130 and
131
move downwards while simultaneously the second bridge support 125 moves
sideways. During this second stage process, only the moveable frame clamping
devices immediately adjacent to the corner keys 139 and 141 are in operation.
1o After the second set of diagonally opposite corners 151 and 153 are welded,
the
assembled frame is then unloaded.
Because the friction welding process is so fast( 3 to 6 seconds),
this two stage process does not significantly increase cycle time and compared
with simultaneously welding all four corners, the key advantage is that the
required movement and control of the heads is greatly simplified. For the four
head welder, the controllers for the individual heads form part of a
coordinated
control system (not shown) that controls all four heads as well as the
operation of
the other mechanized components of the automated four point welder.
For a conventional four head, hot plate welder, the overall cycle
time is about 2 minutes and this overall cycle time includes: profile loading,
corner
welding, cool down and frame unloading. In comparison, the estimated overall
cycle time for the two-stage vibration welding process is less than 30 seconds
and
so this represents a significant increase in productivity. To further improve
productivity, one option is to incorporate an automated mechanical feed (not
shown) for installing the junction pieces in the corner holding fixtures.
As shown in Figure 20, it is technically feasible to simultaneously
weld all four corners 150,151, 152 and 153 in one operation. All four
vibration
welding heads 130, 132,133 and 134 incorporate an additional servo motor 156
that allows each head to move fractionally as the plastic material is melted
during
the vibration welding process. As a result, the position of the heads can be
fractionally adjusted in varying directions so that at four all corners,
perpendicular
pressure is simultaneously applied by the four framing profiles 134,135, 136
and
137 to the four corner keys 150, 151, 152 and 153. However because the head
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movements involved are so small and so complex, the control system for this
simultaneous four headed welding operation is complex and requires very
sophisticated software. Although Figures 18, 19 and 20 show vertical four head
vibration corner welder, it can be appreciated by those skilled-in-the-art
that the
5 bridge supports can span horizontally on a table support.
Although vibration corner can generally be used to join together
extruded plastic profile extrusions, the improved assembly method offers
particular
advantages for fenestration applications. In addition to the production of
conventional windows and doors, the improved assembly method provides for the
1o development of new types of fenestration products. To illustrate the
performance
advantages of vibration corner welding, Figures 21 to 31 show three examples
of
these new types of fenestration products, namely: 1, composite channel window
panels, 2. glass panel units and 3. sealed frame window panels.
Compared to the simple rectangular frame assemblies illustrated in
15 previous figures, these new types of fenestration products incorporate
complex
profile shapes, but it should be noted that the basic component joint design
does
not change and the planar flange junction piece can be configured to
correspond
to the miter joint contour of these more complex profiles shapes.
Figure 21A shows an elevation view of a composite channel window
20 panel 158 consisting of a conventional sealed double glazed unit 159 and a
rectangular sash frame 160 that is assembled around the sealed glazing unit
159
using vibration corner welding.
Figure 21 B shows a cross section detail on a line 21A-21A of the
composite channel window panel 158. The sealed double glazing unit 159
25 consists of two glazing sheets 161 and 162 and incorporates a conventional
perimeter seal 163 with the specific example shown being an inner barrier seal
164 of desiccant filled polyisobutylene (TPS) and an outer structural seal 165
of
polysulphide sealant. The sealed glazing unit 159 is supported on conventional
hard rubber glazing blocks 166 and the glazing channel 167 is conventionally
3 o drained. After the multi-cavity hollow plastic frame has been assembled
and
welded at the corners, two silicone sealant beads 169 and 170 are applied in
the
gaps between the glazing unit 159 and the channel frame profile 168.
Preferably,
the window frame profile is made from glass fiber filled PVC and this has the
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advantage that because of the combined stiffness of glass-and-frame assembly,
the overall frame profile size can be reduced when compared to conventional
PVC
window profiles.
Figure 22 shows an exploded perspective corner detail of a
composite channel window panel 158. The channel-shaped framing profiles 171
and 172 are assembled around the insulating glazing unit 159 and the framing
profiles 171 and 172 are then joined and sealed at the corners using vibration
corner welding. One key feature is that the junction piece 47 incorporates a
removable plastic web 49 that is located on the outer side of the frame and is
held
in the corner web holding fixture attached to the vibratory head of the
friction
welding equipment. This has the advantage that the frame can be assembled
around the insulating glass unit and the corners then welded and sealed. As a
result, by eliminating the need to separately install the insulating glass
unit 169,
there are significant material and labor cost savings.
With conventional hot plate welding, in order for the thin wall profile
walls to be welded together at the corners, the framing profiles have to be
essentially the same size and shape. However with vibration corner welding, by
using a common corner web, different profile sizes and shapes can be
structurally
joined together. For example as shown in Figure 23, the bottom framing profile
173 is larger and incorporates a deep hardware channel 175 while the side
framing profile 174 is smaller and there is no hardware channel. In addition,
with
conventional hot plate welding, only 45° miter cut corners can be used,
while with
a friction welding and a corner key web, it is feasible to join together
framing
profiles with different miter cut angled corners (i.e. 60° and
30°).
2 5 It should be noted that when joining together different size profiles
using friction corner welding, it is necessary for the two moveable framing
fixtures
to apply different engagement forces so that when taking into account the
different
profile sizes, essentially the same pressure is being applied on either side
of the
web.
3 o Although the examples given in Figures 21 to 24 show examples of
a window framing profile being assembled around an insulating glass unit, it
can
be appreciated by those skilled-in-the-art that the same production process
can
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also be used to fabricate a wide range of frame-and-panel products including:
picture frames; mirrors; partitions; shower doors and cupboard doors.
Figures 24A and 24B show a perspective and top plan view of a
welded composite channel frame assembly where the framing profiles 176 and
177 incorporate a single I-shaped cavity 178 and where the thin supporting
profile
walls 179 for the insulating glass unit are solid. The main advantage of this
narrow composite channel profile is that the overall width of the framing
profile is
reduced and as a result, there are material and cost savings. One drawback of
this narrow channel profile is that with a full section corner web, it is
difficult to
achieve a consistent corner weld because the legs of the channel-shaped corner
web are so thin.
One option is for the corner web to only extend to the top profile wall
181 of the I-shaped cavity 178 and to incorporate a notch 182 in the miter cut
corners of the framing profiles 176 and 177. As a result, while the bottom
part of
the profiles 183 is sealed and welded at the corners, the miter cut solid
profile
walls 184 only butt together. However because the vibration welding process
can
be closely controlled, the open gap 185 between the two miter cut profiles 176
and
177 can be kept to a minimum.
Figure 25A shows an elevation view of a sealed double glazed
2 0 panel 159 incorporating a rigid thermoplastic spacer frame 186 that is
welded and
sealed at the corners using vibration corner welding.
Figure 25B shows a cross section detail on a tine 25A-25A of the
perimeter edge of the double glazed panel. The spacer frame 186 is made from
an open channel, rigid thermoplastic framing profiles 187 that are vibration
welded
at the corners to planar flange junction pieces 47 made from essentially the
same
thermoplastic resin as the spacer profile. To minimize differential expansion
between the glazing sheets 161 and 162 and the spacer frame 186, the
thermoplastic spacer profiles are made from glass fiber re-enforced
thermoplastic
extrusions or continuous glass fiber re-enforced pultrusions. After the spacer
3 o frame 186 has been assembled, desiccant-filled polyisobutylene sealant is
applied
to the inner surface 188 of the spacer frame 186 creating a continuous barrier
seal. After the panel has been assembled, double beads 190 and 191 of
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structural thermosetting sealant are applied between the spacer frame 186 and
the two glazing sheets 161 and 162.
For insulating glass panels, the main advantage of using vibration
corner welding is that there is a continuous, single wall barrier seal made
from
rigid thermoplastic material. As a result, the back face 192 of the spacer
frame
can incorporate a variety of profile features including attachment devices. In
addition without damaging the integrity of the barrier seal, other
thermoplastic
parts (e.g. gas fill patches) can also be welded to the back face 192 of the
spacer
frame 186.
1o Figure 26A shows an elevation view of a sealed frame, triple glazed
sash window panel incorporating a perimeter sash frame 194 with vibration
welded corners.
Figure 26B shows a cross section detail on a line 26A and 26A of a
triple glazed, sealed frame window panel 193. The panel consists of two
glazing
outer sheets 161 and 162 that overlap the perimeter sash frame 194 and are
adhered to the frame with thermosetting structural sealant 195. The inner
center
glazing sheet 196 is supported by the perimeter frame 194.
The perimeter frame 194 is assembled from glass-fiber filled, hollow
thermoplastic profiles 197 which are joined and sealed at the corners using
vibration corner welding. The thermoplastic profiles incorporate glass fiber
fill and
as previously noted this provides for increased strength and rigidity as well
as
reduced thermal expansion. Compared to conventional window assembly, the
main advantage of sealed frame glazing unit is that through composite
structural
action, the required size of the sash profiles 197 can be significantly
reduced
resulting in improved energy efficiency and material cost reductions.
With composite structural action, the sealed frame panel performs in
a similar manner to a stressed skin sandwich panel where the perimeter edges
of
the two glazing sheets 161 and 162 are respectively in compression and tension
and so instead of the panel performing as two independent glazing sheets, the
two
sheets 161,162 act together as a structural unit.
The glazing sheets 161 and 162 are structurally adhered to the
plastic frame profiles 197 with structural thermosetting sealant 195 and for
long
CA 02439552 2004-04-23
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29
term durability, silicone sealant is the preferred material.
For enhanced composite structural performance, a high
modulus silicone sealant is required with the thickness of
sealant being preferably less than 3 mm. To provide for
increased panel stiffness, both the bottom edges 198 and
perimeter side edges 199 of the glazing sheets 161 and 162
are adhered to L-shaped seats 200 on either side of the
perimeter frame profiles 197. To allow glazing sheets 161
and 162 to bow in and out with changes in temperature and
pressure, the side edge contact length is kept to a minimum
with 10 mm being the typical length required.
A third center glazing sheet 196 is located
between the two outer glazing sheets 161 and 162 and this
glazing sheet is similar in shape but smaller in size than
the outer two glazing sheets. For improved thermal
performance, the width of the cavity spaces 201 and 202
between the glazing sheets 161, 196 and 162 is typically
between 9 and 18 mm. For improved energy efficiency, a low-
a coating 203 can also be applied to one or more of the
glass cavity surfaces of the window panel 193. In addition,
the cavity spaces 161 and 162 can incorporate a low
conductive gas such as argon or krypton.
To provide for long term gas retention as well as
maintaining the integrity of the perimeter edge seal, there
is a need for a continuous perimeter edge seal between the
outer glazing sheets. Various edge seal configuration sand
sealant materials can be used to provide this continuous
barrier seal. One option as shown in Figure 26B is to apply
low permeable sealant material 204 to the front face 205 and
front side edges 206 of the perimeter frame 194. To
accommodate glass bowing and movement, the sealant material
must be flexible and because of its low temperature
performance, polyisobutylene is the preferred material. To
CA 02439552 2004-04-23
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29a
remove moisture vapor from the glazing cavity spaces 201 and
202, the low permeable sealant incorporates desiccant fill
material with the preferred material combination being 85
per cent 3A molecular sieve and 15 per cent silica gel.
The rigid frame profiles 197 can be made from many
alternative plastic materials produced using various
processes. One preferred material is glass fiber-filled
polyvinyl chloride (PVC) that is extruded to the required
profile shape. One suitable product is Fiberloc* 80530 that
features a 30 per cent glass fiber fill and is produced by
PolyOne Inc. of Cleveland Ohio. The co-efficient of
*Trade-Mark
CA 02439552 2003-08-28
WO 02/098635 PCT/CA02/00842
thermal expansion of the 30 per cent, glass fiber filled material is 18 x 10
'6 cm/cm/
°C and this compares to the thermal coefficient of glass which is 9 x
10 '6 cm/cm/
°C. For very large panel sizes, the thermal expansion of the plastic
profiles can be
further reduced by reinforcing the frame profile walls 207 and 208 adjacent to
the
5 outer glass sheets 161 and 162 with continuous uni-directional glass fiber
strips
(not shown).
Instead of fiber glass reinforced PVC, the frame profiles 197 can be
made from various other alternative plastic materials, including:
thermoplastic fiber
glass pultrusions, glass fiber reinforced engineering structural plastic foam
10 extrusions and high draw oriented thermoplastic extrusions. Because the
plastic -
profiles are firmly bonded to the glazing sheets and expand outwards from the
mid
points of the perimeter frame, maximum stress due to the differential
expansion
between the plastic profiles and the glass sheets occurs at the corners.
Particularly with glass fiber filled profiles, because the corner welds are
typically
15 only as strong as the un-reinforced plastic, the corner welds can be a
potential
weak point in the frame assembly. To provide for increased strength and
rigidity
and to also reduce stress on the corner welds, the preferred assembly method
is
to join the plastic profiles together at the corners using a combination of
friction
corner welding and ultrasonic spot bonding and this production method has
2 0 previously been described in Figures 15A and 15B.
Figures 27A and 27B show a front elevation (Figure 27A) and a side
elevation (Figure 27B) view of the diagonal cut end 209 of the framing profile
for a
triple glazed sealed sash window panel. By removing the frame profile
material, a
3 to 4 mm deep channel 210 is formed in the diagonal cut end of the profile
209
25 creating plastic side ribs 211 and 212. The dotted line 212 on the side
elevation of
the diagonal cut end indicates the depth of the channel 210.
Figure 28 shows an exploded perspective detail of the corner frame
assembly for a triple glazed, sealed frame window panel 193. The two framing
profiles 213 and 214 are joined together by means of special corner keys
30 incorporating a planar flange web 215 and integral legs 216. To provide for
simplified frame assembly, the integral legs incorporate a self centering
spring
device.
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31
As previously shown in Figures 27A and 27B, by removing the
frame profile material, a channel can be formed in the miter cut ends 217 and
218
of the framing profiles 213 and 214 so that the top side rib surfaces 220 and
221
overlap the diagonal center flange 215 of the corner key 217. During the
friction
welding process, the profile ends except for the top side ribs 220 and 221 are
pressured against the center flange 215. Because plastic flash is only
generated
at the interface between the profiles ends 222 and 223 and the corner key
flange
215, a clean parting line is created between the two top side ribs 220 and 221
of
the framing profiles 213 and 214.
Figures 29A to 29E show the production steps involved in
manufacturing a single, vibration-welded, sealed-frame corner assembly.
As shown in Figure 29A, the sealed frame corner assembly consists
of two framing profiles 213 and 214 and a special L-shaped corner key 219 with
a
diagonal center flange 215 and a removable tab 224. A channel is formed in the
miter cut ends of the framing profiles 213 and 214 so that the top side ribs
220
and 221 of the framing profiles overlap the diagonal center flange 215 of the
corner key 219.
As shown in Figures 29B and 29C, the two legs 225 and 226 of the
L-shaped corner key 219 are loosely fitted into the two framing profiles and
the
2 0 corner assembly is placed in the vibration corner welding apparatus. The
removable tab 224 incorporates a special arrow-head profile 227 that fits into
a
complementary shaped insert hole 228 within the corner key fixture 229. The
framing profiles 213 and 214 are held firmly in position by means of front
clamping
devices 230 and 231 that are attached to the moveable framing fixtures 232 and
233 of the vibration welding apparatus (not shown).
As shown in Figures 29C and 29D, the two profiles are pressured
using perpendicular force against the contact surfaces of 234 and 235 of the
corner key 219 and friction is created by rapidly moving the corner key 219
back
and forth. During the friction welding process, as the two profiles 213 and
214 are
3 o pressured against the corner key flange 215, plastic flash flows to either
side of
the contact surface. Because relatively limited flash is produced, the flash
does
not extend into joint line between the two diagonal cut ends 236 of the
framing
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32
profiles and so as a result, a clean parting Line 237 is created between the
framing
profrles.
After the friction welding process is complete and as shown in Figure
29E, the tab 224 is mechanically removed from the L-shaped corner key 219. The
final step in the production process is to bond the interior profile walls to
the L-
shaped corner keys using ultrasonic spot welding 238.
SUBSTITUTE SHEET (RULE 26)
