Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE INVENTION
A method for ultrasonic welding and ultrasonic welding fastener and joining
systems.
BACKGROUND OF THE INVENTION
[0001] Coated abrasive and non-woven abrasives materials are
usually produced in large rolls from which a desired commercial product is cut
by an automated process. Most useful forms are abrasive belts and disks for
example.
[0002] For many years, endless abrasive belts have been made by
splicing the ends of lengths of coated abrasive and non-woven abrasive sheet
materials.
[0003] Four types of splices are common: 1) lap joint made by
profiling each end such that when overlapped and joined with adhesive, which
is preferably urethane, on a heated press, the belt having a uniform cross-
sectional thickness across the joined area; 2) overlap top skived joint,
similar to
the lap joint, except that the layer of grain above the joint is removed by
grinding; 3) butt joint, wherein the two ends are scuffed on the non-abrasive
surface and are butted together, with no overlap, to form an endless belt; a
very
strong thin reinforcing and tear-resistant tape, with adhesive on the surface
thereof, is placed on the back of the butt joint and put in a heated press to
activate and cure the adhesive, which is preferably urethane; 4) interlocking
joint, similar to a regular butt joint, except that the two ends of the belt
have a
wavy cut and interlock in each other.
[0004] Typical materials used for abrasive belts are coated
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abrasives (grain coated on polyester cloth, cotton cloth, rayon cloth, paper,
polyester film) or non-woven scrim reinforced abrasives (grain coated inside
and above the 3-dimensional plastic fiber web).
[0005] Plastic button may be welded on abrasive discs made of a
non-woven material by spin welding or vibration welding. Non-woven abrasive
discs have on the front side a lofty non-woven open web material formed of
synthetic fibers and abrasive particles. The web is needle tacked to an open
weave scrim backing and impregnated with resin and abrasive.
[0006] In the field of plastic welding, ultrasonic methods have not
been developed since it has been established that these methods are only
efficient in the case of two components having a molecular structure
compatibility. Besides, ultrasonic means involve generating very high
frequency
waves and require adjustments according to the type of materials to weld.
[0007] In the cases of disks, when the components to be welded are
not identical, ultrasonic methods have usually been discarded. Generally, in
the
cases of belts, adhesive tapes reinforced with structural filaments, which
curing
is achieved under pressure and heat inside a hot press, are used. This
technique proves to involve time wasting surface preparation and finishing.
[0008] There is still a need in the art for a method for ultrasonic
welding and ultrasonic welding fastener and joining systems.
SUMMARY OF THE INVENTION
[0009] There is provided a method for making a joint between a first
and a second components using ultrasounds, comprising the steps of selecting
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a first material and a second material; selecting an ultrasound-emitting
source;
optimizing parameters of the ultrasound emitting source; and exposing a region
of the joint to ultrasounds emitted by the ultrasound emitting source; thereby
forming a structural interface by melting at the region of the joint between
the
first and the second components.
[0010] There is further provided a joint between a first and a second
components made in one of: i) coated abrasive materials and ii) non-woven
scrim reinforced abrasive materials, the joint comprising a region of the
first
component in contact with a region of the second component, and a bond
generated by exposure to ultrasounds of a film of ultrasound sensitive
material
placed in the region of contact.
[0011] There further provided a joint between a first component
made in one of: i) coated abrasive materials and ii) non-woven scrim
reinforced
abrasive materials, and a second component made in one of: i) metallic
material and ii) plastic material), the joint comprising a region of the first
component in contact with a region of the second component, and an interfacial
bond generated by exposure of the region of the first component in contact
with
the region of the second component to ultrasounds.
[0012] There is further provided a joint between a first component
made in one of: i) coated abrasive materials and ii) non-woven scrim
reinforced
abrasive materials, and a second component made in one of: i) metallic
material and ii) plastic material), the joint comprising a film of ultrasound
sensitive material in contact with both components, and an interfacial bond
generated by exposure of the film of ultrasound sensitive material to
ultrasounds.
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[0013] Other objects, advantages and features of the present
invention will become more apparent upon reading of the following non-
restrictive description of embodiments thereof, given by way of example only
with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] In the appended drawings:
[0015] Figure 1 a) illustrates a butt joint between non-woven scrim
reinforced abrasive belt material pieces by a thermoplastic film supported by
a
polyester tape; Figure 1 b) illustrates an overlap joint between a first and a
second non-woven scrim reinforced abrasive belt material pieces by insertion
of a thermoplastic film; Figure 1 c) illustrates an alternative of the butt
joint of
Figure 1;
[0016] Figure 2a) illustrates a butt joint between coated abrasive belt
material pieces by a thermoplastic film supported on a polyester tape; Figure
2b) illustrates a butt joint between coated abrasive belt material pieces
having a
cloth liner and a first thermoplastic film co-laminated on a backface thereof
to
generate a bond to a second thermoplastic film deposited on a polyester tape
overlapping the joint;
[0017] Figure 3a) illustrates a nylon button welded on a non-woven
scrim reinforced abrasive disk mate(al; Figure 3b) illustrates a nylon button
welded on a coated abrasive disk material co-laminated with a cloth liner and
a
thermoplastic film on a backface thereof; Figure 3c) illustrates a nylon
button
welded on a coated abrasive disk material;
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[0018] Figure 4a) illustrates a metal button welded to a non-woven
scrim reinforced abrasive disk material using a thermoplastic film on the
metal
button; Figure 4b) illustrates a metal button welded to a coated abrasive disk
material co-laminated with a thermoplastic film; and
[0019] Figure 5 shows a table of results of lap shear tests on nylon
button welded on disks.
DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0020] There is provided a method for welding materials together,
such as abrasive belt materials together for example, and for welding on
materials such as on abrasive disk materials, for example, using ultrasonic
methods.
[0021] Ultrasonic methods typically comprise applying a vibratory
mechanical pressure at ultrasonic frequencies at the interface between two
components to be bonded together. Electrical energy is converted to ultrasonic
vibrations through the use of a transducer. The vibratory pressure at the
interface in the welding area generates frictional heat and melts the
materials at
the interface.
[0022] The present method generally provides bonding components
together using ultrasounds.
[0023] The method comprises the steps of selecting the first and
second components; selecting an ultrasound emitting source; and exposing a
region of contact between the two components to ultrasounds emitted by the
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ultrasound emitting source; thereby forming a structural interface at the
region
of the joint between the first and a second components.
[0024] The step of selecting the first and second components
comprises selecting at least one component made in a material having at least
a part with a melting temperature that can be reached under exposure to
ultrasounds.
[0025] The step of selecting an ultrasound emitting source
comprises selecting an ultrasound emitting source according to first and
second components, adapting the shape and geometry of the ultrasound
emitting source according to the bond to be made and optimizing the
parameters of the exposure to ultrasounds, including pressure, power, time of
exposure, delay before withdrawal of the tip ultrasound emitting source (hold
time of the tip), according to the frequency of the ultrasound emitting
source.
[0026] The structural interface at the region of the joint is formed by
engagement of a melted part of the material of at least a first one of the
component with the material of the second component. Partial melting may be
reached in both components.
[0027] The two components may be of similar or dissimilar materials.
[0028] For example the method allows welding a nylon button on a
polyester fabric material under emission of ultrasounds under a pressure of 20
lbs at 80% of an ultrasound-emitting source of 20 kHz, during 1.75 seconds.
[0029] Depending on the flexibility allowed in the step of selecting
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the components and/or in the step of selecting ultrasound emitting source for
example, or on a target resistance of the bond, the present method may further
comprise selecting a film of insertion material and inserting the selected
film in
the region of the bond to be achieved between the two components, either in
the plane of the bond or transversally to the plane of the bond in the case of
a
transverse joint for example.
[0030] Although components of similar materials may usually be
welded together using ultrasounds, using an insertion material having a lower
melting temperature than the materials of the components may be suitable to
avoid using temperatures that could damage one of the components, for
example.
[0031] The selected film may be mechanically deposited, by
lamination for example, on a face of at least one of the components to be
bonded together, or at the interface between the two components to be bonded
together.
[0032] In the case of abrasives materials produced in large rolls for
example, the selected film may be mechanically deposited on the total surface
of one face of the materials or laminated between the backface of the material
and a cloth liner, as will be described hereinbelow.
[0033] People in the art will appreciate that such a feature results in
reduced loss rates at the stage of disks and belts cut-out from complete rolls
for
example. Disks may be cut out, and buttons welded thereon anywhere is
needed using ultrasound directly, since the material already comprises the
selected film.
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[0034] Therefore, the method may comprise continuously laminating
a film of a selected insertion material on an abrasive fabric, with or without
surface preparation by cleaning and sanding for example, and then proceed to
the cut-out of the desired abrasive pieces according to target surface
geometries. These pieces will thus be ready-to be welded.
[0035] Alternatively, the method may comprise continuously co-
laminating a surface coating fabric such as a cloth liner on the backside of
the
abrasive fabric, with or without surface preparation by cleaning and sanding
for
example, with the film of selected insertion material sandwiched therebetween,
welding by ultrasound, and then proceed to the cut-out of the desired abrasive
pieces according to target surface geometries. The cloth liner is found to
prevent shredding of the abrasive fabric. It may also be used for aesthetic
purposes or printing purposes for example.
[0036] The amount of insertion material, i. e, the thickness of the
film, may be adjusted to allow the subsequent joining step, such as welding a
disc button or splice taping using ultrasounds.
[0037] Under action of the ultrasounds, the material of the insertion
film reaches its melting temperature, melts, and the melted material from the
sandwiched film gets into contact with the material to be bounded, which
itself
is non-compatible with ultrasounds, thereby generating a structural bond. In
case of a co-laminated cloth liner, the cloth liner is selected to be of open
weave, i.e. not too closely woven, so as to allow the melted material from the
sandwiched film to go therethrough.
[0038] The examples of Figures 1 illustrate splicing joints in a non-
woven scrim reinforced abrasive belt.
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[0039] In Figure 1a), the non-woven scrim reinforced abrasive
material pieces 12 and 12' are bonded together in a butt joint by an
overlapping
tape 14 supporting an insertion film 16.
[0040] The supporting tape 14 may be a polyester tape, a fiberglass
tape, a polyester fabric, a fiber reinforced polyester splicing tape for
example.
The supporting tape is to withstand stretching forces, which may appear when
the belt is in use.
[0041] The insertion film 16 may be a thermoplastic film or a
thermoset plastic for example.
[0042] In Figure 1 b), a first and a second non-woven scrim
reinforced abrasive material pieces 12 and 12' are bonded together in an
overlap joint by insertion of an insertion film 16; in this case, the
insertion film
16 may be omitted, since typically the layer of grain above the joint is
removed
by grinding.
[0043] Figure 1 c) shows a butt joint of the type of Figure 1 a), which
is reinforced, in a further step, by a second joint formed by submission of a
second thermoplastic film (which may be different from the first thermoplastic
film used in the butt joint according to Figure 1a) on the side of the grains
of the
non-woven scrim reinforced abrasive belt material pieces 12 and 12' to
ultrasounds. Compared to the butt joint of Figure 1a), the joint of Figure 1c)
is
thus reinforced, the joint being prevented from breaking in case the first
butt
joint on the opposite side peels during rolling or other use of the belt.
[0044] It is to be noted that the strength of the bonding depends on
the careful selection of the material of the insertion film according to the
nature
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of the two materials to be welded together and on the matching geometry of the
tip of the ultrasound transducer used.
[0045] For example, a splicing joint in an abrasive belt may be
formed as follows. First, a film of polyurethane of a thickness of 0.008
inches is
colaminated on a polyester abrasive belt material with a cloth liner, under a
pressure of 6 bars, a temperature of 200 C a rate of 1.5 inch/s. Then, a
polyester film reinforced with polyester yarns, colaminated with a
polyurethane
film of a thickness of 0.008 inches, is deposited at the region of the splice,
and
the region is submitted to ultrasounds under a pressure of 20 Ibs, at a
amplitude of 100%, during 5 seconds, using an ultrasound emitting source of
kHz.
[0046] Figure 2a) illustrates the case of a standard coated abrasive
belt, where two coated abrasive belt material pieces 18, 18' are welded
together in a butt joint by a tape 14 supporting an insertion film 16. The
coated
abrasive material may be made of polyester cloth, cotton cloth, poly-cotton
cloth, polyester film or paper for example, and with or without surface
preparation.
[0047] Figure 2b) illustrates the case of a laminated belt, wherein the
insertion film 16 is co-laminated with a cloth liner 20 on the back face of
the
coated abrasive belt material pieces 18, 18', which is previously prepared. A
bond is then generated between the insertion film and an overlapping tape 14.
The cloth liner 20, of open weave, contributes to reinforce the bond as
mentioned hereinabove. Depending on the target bond strength for the belt to
be produced, an additional insertion film 22 may be required under the
splicing
tape to provide further resistance to the welded joint.
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[0048] For welding buttons to disks using ultrasounds, extra care is
required to yield a target adhesion level, taking into account the uneven
thickness of the buttons, which may result in overheating in thinner regions
thereof and in the region of the disk material where the button is welded. The
heat distribution on the surface of the tip of the transducer needs be first
calibrated, so as to achieve a uniform fusion temperature on the whole surface
of the button.
[0049] Figure 3a) illustrates the case of a nylon button 24 welded on
a non-woven scrim reinforced abrasive disk material 12 without surface
preparation.
[0050] Figures 3b) illustrate the case of a nylon button 24 welded on
a coated abrasive disk material 18, made of polyester cloth, cotton cloth,
poly-
cotton cloth, polyester film or paper for example, and with or without surface
preparation, the coated abrasive disk material 18 being co-laminated with an
insertion film 16 and a cloth liner 20 (for further reinforcement of the
joint, in
particular in case the abrasive disk material is damaged in the region of the
button due to the ultrasound exposure, which may result in a lack of
resistance
of the disk in use. Lamination of a cloth liner 20 provides body and shredding
resistance to the disk in use.
[0051] Figures 3c) illustrate the case of a nylon button 24 welded
directly on a coated abrasive disk material 18, made of polyester cloth,
cotton
cloth, poly-cotton cloth, polyester film or paper for example, and with or
without
surface preparation.
[0052] In Figure 4a), a metal button 26 is welded to a non-woven
scrim reinforced abrasive disk material 12 without surface preparation using
an
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insertion film 16.
[0053] In Figure 4b), a metal button 26 is welded to a coated
abrasive disk material 18, made of polyester cloth, cotton cloth, poly-cotton
cloth, polyester film or paper for example, and with or without surface
preparation, co-laminated with an insertion film 16 and a cloth liner 20.
[0054] In both previous cases, an ultrasound transducer may be
used, or a heating device having a shape reverse from that of the button, or
the
shape of the tape, may be used.
[0055] The quality of the bonding between the metal button on the
non-woven material or the coated material is directly dependent on the nature
of the film 16, the geometry of the tip of the transducer and the laminating
steps
parameters. More precisely, the film 16 must be uniformly activated at a
precise
temperature (melting temperature) and a uniform pressure applied on the
button, in order to yield a strong adhesion.
[0056] A nylon button may thus be welded on a polyester abrasive
disk material as follows. First, a film of polyurethane of a thickness of
0.008
inches is colaminated on a polyester abrasive disk material with a cloth
liner,
under a pressure of 6 bars, a temperature of 200 C at a rate of 1.5 inch/s.
Then, a nylon button is put in place on the polyester abrasive disk material
and
submitted to ultrasounds under a pressure of 20 Ibs, at an amplitude of 100%
and a frequency of 20 kHz, during 3.5 seconds.
[0057] The present method therefore provides assembling together
a variety of components by ultrasonic welding, such as, for example, a) a
threaded male plastic button and an abrasive circular disc made of coated
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abrasives or non-woven abrasives; b) a transverse splicing joint on an endless
abrasive belt, made of coated abrasives or non-woven abrasives; c)
components of different materials, etc...
[0058] The provision of a co-laminated insertion film, with or without
co-lamination of a cloth liner on the backside of the abrasive fabric, allows
rapidly executing joints using ultrasounds only, with an adequate adhesion
quality both on steel and plastic.
[0059] Figure 5 shows a table of results of lap shear tests on nylon
buttons welded on abrasive disk materials. As may be seen from the comments
in the last column, the joint itself is strong, the button or filaments of the
material breaking before loosening of the joint.
[0060] The method allows bonding by ultrasounds a metallic button
on an abrasive fabric which has been co-laminated with an insertion film, such
as a plastic film, and optionally a cloth liner, without recurring to any
adhesive,
due to the provision of the co-laminated insertion film, the cloth liner being
so
selected so as to be sufficiently open weave to allow the melted material of
the
insertion film to go through at the melting point of the material of the
insertion
film, under exposure to ultrasounds.
[0061] As people in the art will appreciate, the present bonding
method is much quicker than when using adhesives, which typically requires
lengthy curing times: the duration of the binding process may thus be reduced
from hours, when using adhesives, to seconds when using the present method.
[0062] The method comprises selecting the materials of the
components to be joined according to target applications, in terms of
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compatibility and reactivity to ultrasounds; selecting an insertion material,
i.e. a
material sensitive to ultrasounds so as to generate an interfacial bond
between
the materials of the two components to be welded together in spite of a
molecular mismatch; optionally preparing the surfaces of the components to be
welded, by cleaning and sanding for example, and defining the texture thereof
in order to improve adhesion properties, either chemical and mechanical;
adapting the shape and geometry of the ultrasound emitting source; and
optimizing the parameters of the exposure to ultrasounds, including pressure,
power, and time of exposure, according to the frequency of the ultrasound
emitting source, to meet a target adhesion strength or lap shear between the
two components to be welded together.
[0063] In the case of nylon buttons on abrasive disks for example, it
may be possible to achieve a lap shear between the buttons and the abrasive
disks of about 50 pounds/square inches by a 1 second ultrasonic exposition
(see Figure 5).
[0064] The materials of the components to be welded together may
be of thermoplastic and/or of thermoset type, and typically comprise
polyolefin,
polyamide, polyester or polyurethane. The materials of the components to be
welded together may also be metallic, organic, inorganic or other plastics.
[0065] When the components to be joined comprise different
materials, an insertion material sensitive to ultrasounds is used.
[0066] In the case of a transverse joint, this insertion material further
provides a filling material at the line of transverse joint, in particular in
the case
of abrasive belts for example, which contributes to an improved uniform
sealing
in the transverse axis. As people in the art will appreciate, such improved
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sealing of the line of transverse joint further secures the joint by
preventing an
upper layer of the three-dimensional non-woven abrasive material from lifting
and coming apart as the belt is in use for example. A target lap shear of the
bond is about 30 pounds/square inches under a 1 to 2 seconds ultrasonic
exposition, and the step of preparing the surfaces of the components to be
welded is minimised.
[0067] In the case of two components each having one surface of
thermoplastic material, the thermoplastic materials of these surfaces are
exposed to ultrasonic welding so that the thermoplastic materials melt in
surface and bond together, without insertion material, although an insertion
material may be used for stronger results.
[0068] In the case of a first component of thermoplastic material and
a second component of non-thermoplastic material, a layer of insertion
material
may be provided on the surface of the non-thermoplastic component to allow
bonding with the thermoplastic component. When exposed to ultrasounds, the
material of the thermoplastic component and the insertion material of the
layer
on the second component melt in parallel, with the result that the different
components are bonded together.
[0069] In the case of non-thermoplastic components, an insertion
material sensible to the ultrasonic welding may be provided at the interface
to
generate proper bonding.
[0070] The present method of fastening and joining components by
ultrasonic welding allows shorter assembly cycles of the order of one second
for an enhanced quality of bonding, with a resulting lap shear of up to
50/Ibs/po2, and a reduced reject rate due to improved joint uniformity.
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Moreover, the resulting products, such as abrasive belts, are usable right
after
assembly, since there is no delay required for post curing, as is the case
when
using adhesives.
[0071] Although the present invention has been described
hereinabove by way of embodiments thereof, it may be modified, without
departing from the nature and teachings of the subject invention as defined in
the appended claims.
