Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to fittings for use in fluid piping systems,
and especially to fittings which utilize deflectible seals,such as resilient
solid sealing rings, and chevron rings, and to a method for assembling a
fitting.
It is a characteristic of this type of fitting that a body having a
fluid passage therethrough includes a socket member, within which a deformable
sealing ring is held in an internal ring groove. The diameter of the aperture
in the sealing ring is smaller than the outer diameter of a pipe, so as to be
deflected by the pipe and form a fluid seal. The conventional method of manu-
facturing fittings of this type is to cast a massive knob on a body and thenmachine the internal groove in the knob. This is a very expensive technique
and frequently results in out-of-round ring grooves. An out-of-round ring
groove is unacceptable, because it leads to leakage in usage.
A further undesirable feature of conventional fittings is that the
thickness of the knob when cast is quite large, and the cycle time of a plastic
molding machine to make it is relatively high, and the production rate is
relatively low. Accordingly, the cost of the produced item, even before
machining, is greatly increased. Furthermore, larger masses when cast tend to
have void inclusions more frequently than thinner sections. Therefore, an
increased risk exists of making scrap in the molding process.
Yet another disadvantage of cast articles is that a core must be in
place while they ~re being cast, and the core must thereafter be removed. As
a consequence, no part of the casting closer to the opening can have a smaller
diameter than any part farther from the opening, or the core cannot be removed.
This means that the mouth must be quite large, and that a pipe inserted into
the fitting can be bent sidewise as a lever relative to the socket member, and
tends to flatten out-of-round ehough to permit leakage. This can occur, for
example, when a heavy body, such as a vehicle, rolls over the ground above the
joint.
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With this invention, a hub member of reduced diameter can be fixed
in a socket member of larger diameter, after the socket member is molded.
Such an arrangement has the advantage that there can be some play between the
pipe and the inside of the socket member when the pipe moves as a lever, and
the tendency of the pipe to flatten is significantly reduced.
It is an object of this invention to provide a fitting which can be
made from members with modest cross-sections that can be assembled into a
larger solid construction.
The invention provides a fitting comprising a body having a flow
passage therethrough; a socket member on said body having an opening, a central
axis, a peripheral socket abutment wall, and a per~pheral socket sidewall in
said opening; a ring-like hub member in said opening~ said hub member having
a peripheral hub abutment wall, a peripheral ring groove face, and a hub side-
wall; a peripheral ring groove bottom facing on one of said members facing
inwardly toward said central axis and adjacent to the said ring groove face;
said members being made of a thermoplastic material, which material is fusible
to like material by motion fusion, said abutment walls extending non-parallel
to the axis, and being joined together solely by fusion of the surface mate-
rials of the abutment walls, all radial dimensions of the socket member from
~he socket sidewall to and including the opening end of the socket member
being greater than any radial dimension of the hub member, there being no
radial overlap of the hub member by any part of the socket member at said
end of the socket member; and a resilient sealing ring in the ring groove
formed by the ring groove face and ring groove bottom surface.
The invention, can be employed to provide an inexpensive fitting
construction wherein the critical dimensions relative to the ring can inex-
pensively and conveniently be held to very close tolerances, and the members
of the fitting assembled in a low cost operation, whereby a construction is
obtained which has very close dimensional tolerances where it matters, namely
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at the surfaces which support the ring. The groove, once formed, remains
circular, concentric, and in good alignment.
According to a preferred but optional feature of the invention, the
two members are made of materials with good insulating properties, and the
wall thickness of the hub member is greater than that of the socket member,
whereby to provide for greater dimensiDnal stability of the hub member when
these members are heated. A cavity is preferably formed between the hub mem-
ber and the socket member to receive slag for~ed by the heat of friction.
According to still another preferred but optional feature of the
invention, an elastomeric sealing ring is in place between the socket member
and the hub member when they are joined to one another, whereby to smooth out
the slag which may be introduced into the groove so it does not prevent a good
seal from being made.
From another aspect, the invention providesthemethod ofassembling
a ring-shaped hub member of a fitting in a circular ope~ing in a socket member
comprising pressing an abutting wall of each member against the other with a
resilient ring placed in a ring groove that is contiguous to both abutting
walls, said ring groove having an edge adjacent to both of said abutting walls
which forms a peripheral reservoir, and generating heat by means of motion
fusion, whereby to fuse the members together at said abutting walls and to
discharge slag from the joinder into said reservoir, the wall thickness of
the hub member at the point of fusion being greater than the wall thickness of
the socket member, whereby distortion of the socket member as a consequence of
the heat is minimized.
The above and other features of this invention will be fully under-
stood from the following detailed description and the accompanying drawings in
which:
Figure 1 is a side elevation, partly in cutaway cross-section, show-
ing an embodiment of the invention;
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Figure 2 is a cross-section taken at line 2-2 of Figure l;
Figure 3 is an enlarged fragmentary axial cross-section of Figure l;
Figures 4-8 are fragmentary axial cross-sections showing other
embodiments of the invention;
Figure 9 and 10 are fragmentary elevations, partly in cutaway cross-
section, showing two steps in the preferred method of manufacturing the fitting;Figures 11 and 12 are fragmentary axial cross-sections showing two
steps in an alternate method of manufacturing the fitting;
Figures 13 and 14 are fragmentary axial cross-sections showing other
structural joinders useful with this invention;
Figure 15 is a side elevation partly in cutaway cross-section, show-
ing the presently-preferred embodiment of the invention;
Figure 16 shows the parts of the assembly of Figure 15 just before
joinder;
Figure 17 is a cross-section taken at line 17-17 in Figure 15;
Figure 18 shows the parts of Figure 15 loosely assembled;
Figure 19 is an enlargement of a region within line 19-19 in Figure 15;
Figures 20 and 21 are fragmentary cross-sections of an alternate
embodiment in loose and joined conditions, respectively; and,
Figures 22 and 23 are fragmentary cross~sections of another embodi-
ment in loose and joined conditions, respectively.
Figure 1 shows an embodiment of fitting 20 according to the invention.
The fitting comprises a body 21 having a flow passage 22 extending therethrough
along a central axis 23. The body comprises a socket member 25, a hub member
26, and a sealing ring 27 retained in a ring groove 28 formed between the hub
member and the socket member. Pipes 29 and 3~ are shown connected by fitting
20, which is the function of the fitting. The fluid seal is made by deflection
of the sealing ring by the outer surfaces 31, 32 of pipes 29 and 30, respect-
ively. This type of fitting is sometimes referred to as a "compression"
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fitting because the sealing is caused by compression, or more rigorously by
deflection, of the seal material.
Fittings are known which have internal ring grooves holding internal
resilient rings. As previously stated, there is herein described a very
accurate ring groove made inexpensively.
Socket member 25 includes a socket sidewall 35 and a socket abutment
wall 36. These are formed in each end of the fitting or at any other place in
the fitting, for example at a third location if the fitting were a T, where
the fitting opens for connection to a pipe.
The socket member has an enlarged section 37 which accommodates a
counterbore formed by the socket sidewall. Preferably, but not necessarily?
the socket sidewall has a draft angle (~) of approximately 2-1~2 degrees ( 5
degrees conical) opening toward the open end 38 of the socket member. There-
fore, socket sidewall 35 is frustoconical. It terminates at socket abutment
wall 36 which is planar. Sidewall 35 is concentric with axis 23 and wall 36
is normal to axis 23.
The socket abutment wall can have two functions, and therefore its
radially innermost portion (numbered 39 in Figure 3) is sometimes also refer-
red to as a groove side face 39. It may or may not be coplanar with the re-
mainder of abutment wall 36, as will later be discussed. Instead, it may beaxially spaced from it.
Hub member 26 is a ring-shaped body having a central opening 40 to
pass pipe 29. It hasa hub sidewall 41 and a hub abutment wall 42. Under
certain circumstances, socket abutment wall 36 and hub abutment wall 42 will
abut and be joined to one another by a structural joinder.
The hub member also includes a groove side face 43 and a groove
bottom face 44. Bottom face 44 is cylindrical and extends peripherally around
the central axis 23 in alignment therewith. The accuracy of its diameter, its
concentricity, and its circularity when the hub member is fixed in the socket
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member are important features.
Hub sidewall 41 also has a draft angle, preferably of the same
angularity as the socket sidewall 45. It may be slightly oversized relative
to the socket sidewall, for example, by approximately 0.001 inch on the dia-
meter~ whereby to form an interference fit. Hub sidewall 41 in this embodi-
ment is also a frustoconical surface of revolution.
Ring groove 28 is defined as the spacing between groove side faces
39 and 43, bounded by bottom face 44. There may, in some embodiments, also
be a spacing between the socket abutment wall 36 and hub abutment wall 42 so
that they will not in fact be in abutment, and a clearance may exist between
them. This means that under such circumstances the groove bottom face 44 will
not interconnect both groove side faces, but this is of no importance to the
invention.
Sealing ring 27 is seated in the ring groove in contiguity with
bottom face 44. It projects radially inside both of the side faces in order
that a compressive f~rce may be exerted on the pipe. Preferably, a clearance
46 will be provided between the ring and one or both of the side facesin order
that the resilient, but incompressible, elastomeric material of the sealing
ring may have some place in which to move when it deforms. Should this place
not be provided, then deformation will occur along the pipe itself, which is
also an acceptable arrangement. A suitable set of dimensions (in inches) for
a two-inch fitting of this type (see Figure 3) is as follows:
A 3.400 F 2O722
B 3.088 G 2.388
C 2.800 H 1.460
D 2.405 K 0.498
E 2.360 L 0.995
A desirable feature of the fitting according to this invention is
its suitability for use with both high pressure and low pressure fittings.
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The rectangular sectioned ring shown in Figure 3, or its equivalents such as
solid 0-rings, is suitable for relatively lower pressures where reliance is
had upon the resilience of the material to make the seal. Chevron-type seals
are used for higher pressure ranges.
Figure 4 shows fitting 20 utilizing a chevron-type ring seal 48
which utilizes the pressure of the fluid being sealed to spread its arms 49,
50 apart to make a more reliable seal. These seals are well known in the art
and require no further description here, because they form no part of the
instant invention.
A structural joinder 47 joins all of the walls together.
An important feature of the invention resides in methods for joining
the hub member and the socket member together. These methods will be discussed
after alternative constructions of the fitting are disclosed. Figures 5-8 show
alternative constructions of hub members and socket members.
In Figure 5, a socket member 55 is shown which has a socket sidewall
56 bounding a counterbore in the end of a body 57. A groove side face 58
extends laterally relative to the central axis as in Figure 1. Socket sidewall
56 is a straight cylinder.
Hub member 60 has a hub sidewall 61 of substantially the same diameter
20 as sidewall 56. It may make a light press fit or even a relatively loose fit.
An abutment wall 62 is formed on the end of the socket member, and a flange
63 on the hub member carries an abutment wall 64. The two abutment walls are
flat annuli lying normal to the central axis of the fitting. The hub member
also carri es a groove side face 65 and a groove bot*om face 66. Structural
joinder 67 is made between the two abutment walls in a manner yet to be
described.
Figure 6 shows an alternative form of hub member 70 which can be
utilized with either of the sockets of Figures 1 and 5. It differs from hub
member 26 only in that its hub sidewall 71 has two portions, a first straight
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portion 72 and a second tapered portion 73. For reasons which will become
evident, structural joinder between the hub member 70 and the socket member
will occur at tapered portion 73.
Similarly in Figure 7, a hub 75, identical to hub member 26 except
for its outer hub sidewall 76, is shown. Hub member 75 includes first and
second straight cylindrical portions 77, 78 joined by a curved portion 79,
the diameter of portion 77 being greater than that of portion 78. Structural
joinder in this construction, when hub member 75 is used with the socket member
of Figures l or 5, will occur at straight portion 77 and perhaps at part of
curved portion 79.
Figure 8 shows another embodiment of hub member 80 for use with
either of the socket members of Figures 1 or 5 and identical to hub member 26,
except for its hub sidewall 81, which includes a straight cylindrical portion
82 and a tapered portion 83. This is a reversal of the construction of Figure
6, and in this case, structural joinder may be expected to be formed at the
straight cylindrical portion 82 which has a diameter larger than the major
portion of the tapered portion.
This invention is especially useful in the manufacture of thermo-
plastic fittings. A significant feature of such materials, for example,
polyvinyl chloride, polyethylene, polypropylene, and ABS, all characterized
as being thermoplastic, is that they are also good insulators. Accordingly,
their surfaces may be heated without substantially changing the temperature of
the entire body and of distorting it thermally. This permits the use of fric-
tionally developed forces and the heat which they generate for the purpose of
assembly. It may be said thatthe more crystalline materials are more difficult
to spin-weld or vibration-weld, but are readily ultrasonically welded. The
materials which are more amorphous are better for spin-welding or vibration-
welding. ABS is the best material known at present for this class of welding.
However, even though there may be some greater convenience with one than with
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another, the motion fusion processes can be made to work satisfactorily on
most thermoplastic materials. Lower molecular weight materials appear to
work better.
Figures 9 and 10 show the preferred method for assembling the device
of Figure 1. In Figure 9 socket member 25 and hub member 26 are shown being
brought together, andthe spacing 85 shown between them represents the axial
displacement along axis 23 which results as a consequence of the interference
fit. If there were no interference fit between the sidewalls, then the abut-
ment walls would fit initially *ogether in full contiguity. In the preferred
embodiment, the hub member is gripped, such as by placing driver means (not
shown) into recesses 86 (Figure 1), in its end and rotating the hub member,
as schematically illustrated by arrow 87, while at the same time applying an
axial force, as indicated by arrow 88. As a consequence of this relative
rubbing motion, friction will rapidly heat those ones of the walls which abut
one another. In a brief time, perhaps in only one or two seconds, the necess-
ary amount of axial movement between the parts can occur to overcome the inter-
ference. For this reason, in the assembled illustration of Figure 3, the wall
dimensions of the hub member and the socket member are shown as equal to one
another.
Initially, the outer diameter of the hub member will have been greater
by the amount of interference. Because the wall thickness of the hub member
is greater than that of the socket member, it is the socket member which will
yield the most. It is an advantage that all radial wall thicknesses of the
hub member be greater than the surfaces of the socket member which they abut
for the reason that, for a given quantum of heat generated, the temperature of
the hub member will increase the least, thereby resulting in least thermal
effect on the groove side face and the bottom face ofthe hub member, which
should be undistorted. In assembling a two-inch fitting, it has been found
that somewhere between four and eight turns at approximately 100 rpm will
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result in a firm binding joinder of all of the wall surfaces. The device
with the dimensions illustrated made of polyvinyl chloride will feel warm to
the hand just after joinder, and a firm structural bond, fully resistant to
the forces generated by fluid on the fitting will have been developed. The
important feature of the joinder is a complete peripheral fluid-sealing struc-
tural joint, and it may be provided between either the abutment walls or be-
tween the side walls, or between both, as preferred, so long as sufficient
area of joinder is provided.
For example, in Figure 5 there may or may not be a structural join-
der formed between the sidewalls, but there is one between the abutment walls
62 and 64. Should a joinder between the sidewalls also be desired, then the
dimensions will have been arranged accordingly.
In all of the embodiments of Figures 6, 7 and 8, the rotational
technique of assembly just described will cause a structural joinder to occur
between contiguous walls, which are forced to bear against one another when
the hub member is pressed into the socket member, and the hub member and
socket member are rotated relative to one another.
Figures 11 and 12 illustrate that a structural joinder resulting
from friction can be obtained, even without an interference fit, by pressing
them together in bearing relationship during the spinning operation. Figure
11 shows a socket member 90 and a hub member 91, whose sidewalls 92, 93,
respectively, have an initial clearance 94 between them before assembly. At
the time of assembly, a collet is utilized to squeeze the socket sidewall
toward and against the hub sidewall, this force being schematically illustrat-
ed by arrow 95. At this time, the hub is rotated, and structural joinder 96
is formed at the place where they are held against each other during this
operation.
Figure 13 illustrates an embodiment similar to that of Figure 11
where a clearance 100 is formed between the hub member 101 and socket member
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102, there being an abutment wall 103 on the socket member and an abutment
wall 104 on the hub member which make contact with each other so as to form
a joinder 105.
Figure 14 shows a socket member 110 and a hub member 111 joined
together by a layer of cement 112, which is a chemical or settable type of
bond, or a suitable solvent joinder, rather than by a self-bond, such as is
caused by the heat joinders heretofore described. Any suitable cement or
sealant, for example, the well-known anaerobic sealant "Loctite", or any
other suitable substance may be utilized. A solvent will soften the two
surfaces so they can merge, and the solvent will gradually migrate from the
part, leaving a structural joint.
Occasionally, a leakage path might occur in some of the embodiments
of Figures 1-4 because of slag inclusions, and also because with spin-welding
it is difficult to assure that there will always be a continuous peripheral
seal between two axially-extending walls, for example between two tapered
nearly cylindrical walls. It has been found that a butt-weld is more reliable
in production, provided that a place is provided to which the slag which is
produced by the spin-welding operation can flow. It is undesirable for the
slag to remain in the but-weld itself, and it is preferable for it not to
project into the ring groove in such a way as to wrinkle the fl~xible seal.
The term 'tslag" means plastic material which is displaced during the
spin-welding operation. The butt-weld preferably has a relatively small cross-
section so as to assure a complete fused structural joinder. Of course, the
other surfaces may also be joined, but primary reliance is placed on the butt
joinder, and assurance is first sought that this joint is complete. The other
joinders are of secondary importance, and merely provide additional structural
strength.
In the embodiments of Figures 15-23, the rubber ring is put in place
while the parts are still loosely assembled. When the part is formed, the ring
locjoo7s
smoothens ("irons out") any slag tha~ enters the ring groove. This arrange-
ment provides a slag layer, rather than a "lump". A lump might prevent a
good seal. The smooth conforming layer permits a good seal to be made, be-
cause it does not wrinkle the ring.
Also in the embodiments of Figures 15-23, "reservoirs" may be pro-
vided for the slag to flow into, so that it will not flow to undesired loca-
tions where it might prevent a fluid-sealing joinder from being made.
The presently preferred embodiment of fitting 120 according to this
invention is shown in Figure 15. It is shown joining two pipes 121, 122
together. It includes a socket member 123 with an open mouth facing to the
left (for a socket member which opens in two directions, the construction is
multiplied with like structure at both ends~. A hub member 124 is attached
inside opening 125 of socket member 123, and a flexible chevron sealing ring
126 is placed in a ring groove 127 formed by the socket member and by the hub
member.
The sealing ring (Figure 16) is conventional. It includes a pair of
flanges 128, 129 which are continuous with a bight 130. The bight includes a
pair of curved outer corners 131, 132. In the unflexed condition when no pipe
is in the fitting, the inside flange 129 will project wi~hin the boundaries
defined by the hub member and socket member in order to make a compressible
press fit with the pipe when the pipe is inserted. Insertion of the pipe com-
presses the seal. Spacing 133 (Figure 18) is shown between flanges 128 and
129, and a bead 134 extends into space 133.
The hub member includes a peripheral groove 135 with shoulders 136
to be engaged by a driving tool for turning the hub member when it is to be
spin-welded to the socket member.
A stop 137 is formed inside the fitting which the pipe may strike
to limit its insertion into the fitting.
As best shown in Figure 18, the socket member is provided with a
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socket sidewall 140 and a socket abutment wall 141. Each of these has a draft
angleo~, usually about 2 . The purpose of the draft angle on sidewall 140 is to
facilitate removal of the core after the casting operation, and the purpose of
the draft angle on abutment wall 141 is to provide for a reservoir yet to be
described. The socket member also includes a ring groove bottom face 142 and a
ring groove side face 143 to accommodate the flexible sealing ring 126. A
chamfer 144 is provided for receiving a portion of the sealing ring.
The hub member includes an outer hub sidewall 150 and a hub abutment
wall 151. Sidewall 150 preferably has a draft angle about equal to that of the
socket sidewall 140, but abutment wall 151 will lie substantially normal to
axis 152. As can be seen in Figure 18, ~he dimensions are such that the hub
can loosely be fitted into the socket member and, then as can be seen in Figure
16, just makes contact between the hub abutment wall 151 and edge 153 of the
socket abutment wall, still leaving a very small clearance between the sidewalls
(too small to be shown in Figure 16). Accordingly, when the hub member is spun
into the socket member, the abutment walls will fuse together over a substantial
annular area, as shown in Figure 19, and a small reservoir 155 will be formed
to receive the slag, i.e., material displaced from the abutment walls. This
slag will not interfere with the fusion 156 between the abutment facesO This is
20 the important and peripheral joinder and makes a fluid-tight seal. There is an
additional fusion 157 which will occur in properly-proportioned parts between
the sidewalls, and this occurs as the hub member moves into the socket member
and the sidewalls come into contact during the spinning. This is for additional
structural integrity, but will not be primarily relied on for fluid-sealing
continuity.
In addition, a second reservoir 160 (Figure 19) is formed between
the curved outer corner 131 of the sealing ring and the portion 161 yet to be
described. This is a particularly interesting reservoir because, with the
resilient ring in place during the spinning operation, the hot slag will tend
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to be wiped to form a smooth annular body which will occupy the reservoir
without displacing or wrinkling the seal. Accordingly, not only is there a
continuous fluid seal between the abutment walls of the hub member and the
socket member, but also there is an unimpeded contact between the seal and
the ring groove bottom face and between the seal and portion 161 of the hub
member adjacent to its abutment face. Portion 161 acts as a ring groove side-
wall, and sometimes is referred to as "ring groove sidewall 161". There
results a structurally integral, dependably fluid-sealing construction. Some
slag 163 may also escape at the open end of the fitting, but it is of no
importance as to fluid-sealing.
Figures 20-23 show other locations for reservoirs according to this
invention and means for constructing them. For example, in Figure 20 fitting
170 includes a socket member 171, a hub member 172 and a sealing ring 173.
These are shown loosely assembled in Figure 20, and it will be noted that hub
sidewall 174 and socket sidewall 175 have a draft angle, while the hub abut-
ment wall 176 and socket abutment wall 177 do not. Instead, walls 176 and 177
are normal to the central axis. However, an annular reservoir groove 178 is
formed to receive slag 179 (Figure 21). Similarly, the socket ring groove
bottom face 180 may be undercut by chamfer 181 to form a reservoir 182 addition-
al to and enlarging the reservoir formed adjacent to the corner of the resil-
ient ring in the event that the slag emission at this point is so great as to
require the additional reservoir volume.
~ s in the embodiment of Figure 15, the abutment walls will first be
brought into contiguity, and then while they spin and fuse together, as shown
in Figure 21, Secondary fusion can occur between the sidewalls. The same
advantages are attained as in the embodiment of Figure 15.
Figures22 and 23 show another embodiment, wherein a greater and
more concentrated amount of fusion can be secured by modifying the shape of
the abutment walls. In this fitting 185, there is a socket member 186, a hub
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member 187 and a sealing ring 188. The socket and hub sidewalls 189, 190 may
have a draft angle as in Figure 20. However, the abutment walls are consider-
ably different. In this case, the hub abutment wall 191 has an undercut
segment 192, an intermediate segment 193 and a fusion segment lg4. Similarly,
the socket abutment wall 195 has an undercut segment 196, an intermediate
segment 197 and a fusion segment 198. The fusion segments are annular, normal
to the central axis, and of relatively small area, so that a deep, relatively
small area fusion weld 200 is formed at their joinder. There may be fusion
201 also at the intermediate segments and fusion 202 at the outer sidewalls,
but primary reliance for sealing purposes is placed on weld 200.
Figure 21 also shows an optional means for providing a reservoir,
instead oftheone shown adjacent to the ring. This is a pair of undercuts
205, 206 formed respectively in the hub member and in the socket member.
These are optional, and ordinarily will not be preferred.
The embodiments of Figures 15-23 thereby show structures and methods
for assuring a full, peripheral, fluid-sealing weld between the hub member,
and the socket member and means for disposing of slag in such a way as not to
distort the flexible ring and to be certain that the weld is further shielded
from the Muid in the pipe by undistorted surfaces of the fluid-sealing ring.
The terms "fusion" and "fusion weld" are synonymous with "structural
joinder".
The term "motion fusion" as used herein means ultrasonic welding,
spin-welding, and vibration-welding. Ultrasonic welding can be used to weld
these structures together the same as spin-welding, and with substantially the
same results. Ultrasonic welding is "motion fusion", because it results from
heat produced by the rapid relative vibration of the contiguous surfaces. Only
endwise pressure, without rotation, will be needed when ultrasonic welding is
used.
"Spin-welding" is the process of creating heat for fusion by rotating
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one part relative to another. ~'Vibration welding" is the process of creating
that heat by rapid back and forth rubbing motion, either angular or trans-
lational, or a combination. With motion fusion, it has been found desirable
to hold the part motionless for a moment after the motion ceases to let the
joinder "set" before removing the compressive force. For example, a joint
to be spin-welded might be spun for one to three seconds, with axial pressure
exerted. Then the spinning would be stopped, and the axial force maintained
for about 1/2 to 1 second before releasing the par~.
Vibration-welding appears to be best suited for joining crystalline
thermoplastic resins, such as acetal, nylon, polyethylene, and polypropylene,
which are not as easily joined by ultrasonics, solvents, or spin-welding as
more amorphous plastics, such as polystyrene, ABS, acrylic, and polycarbonates.
It is also successful with fluorocarbon and fluoropolymer plastics, and with
polyester elastomer.
The term "abutment surface" means a surface which is so oriented
that axial forces against it are primarily transmitted as axial forces, rather
than as radial components. Therefore, an "abutment" will make an included
angle with the axis greater than about 45 . A sidewall will make a lesser
angle, because its orientation primarily transmits radial forces.
In making the structural joinder by friction as heretofore des-
cribed, it is necessary to generate a temperature at the surfaces which are
to join one another of at least approximately 300 F., which is not difficult
to do. The device which rotates the hub member relative to the socket member
may have an overriding clutch to release the drive once the parts have become
assembled. In fact, it will be found that after they have initially softened
sufficiently, they will grab each other and prevent further rotation relative
to one another. Similar considerations govern the usage of ultrasonic and
vibration-welding.
It will be noted that the hub member and the ring groove are concen-
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tric and round because they are molded that way. Further, the hub member is
massive enough that it will stay that way throughout the mechanical and
thermal processing which it undergoes. The axial alignment of the hub member
relative to the socket member is not especially important, so long as suffi-
cient clearance exists inside the body to receive a pipe, even if it is some-
what out of line.
In addition to heat being generated by the exertion of mechanical
forces, it is possible to use other techniques for fusing the wall surfaces
when brought together. For example, the wall surfaces may be quickly heated
to temperatures suitable for fusion, such as in a hot oven, or by air blast,
or by other means, whereupon the hub member and socket member may quickly be
pressed together, but without rotation.
It will be noted from the foregoing that it is unnecessary to provide
walls which are not used to make structural joinders. For example, if structur-
al joinder is to be made only at the sidewalls, then the abutment walls need
not be provided, and vice versa.
The term "structural joinder" means a region of attachment of the
strip members. When they are joined by fusion, it is the fused region. When
they are joined by compositions, such as adhesives or sealants, the structural
joinder is the interconnecting composition.
Wherever spin-welding is used for heating, the contiguous surfaces
will be surfaces of revolution generated around the central axis so they will
be in contiguity when the hub member spins in the socket member. Vibration-
welding is most conveniently accomplished with such surfaces.
It is also evident that both groove side surfaces can be formed in
the hub member and none on the socket member. Also, only one groove side
face need be provided (on the hub) for retention of the ring under pressure.
Accordingly, a second groove side face, or one on the socket member, may be
unnecessary.
lOS()~75
This invention is not to be limited by the embodiments shown in the
drawings and described in the description, which are given by way of example
and not of limitation, but only in accordance with the scope of the appended
claims.
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