Method and apparatus for forming fiber reinforced coupling sleeves

An apparatus and method is provided for fabricating plain-end pipe couplings. Ribbons of resin-soaked fiber reinforced plastic strands are wrapped about a rotating operably expandable mandrel which has placed therearound a pliable resilient form collar which defines an inner surface of such a coupling. After curing, the wrapped ribbons form a rigid coupling. The mandrel is thereafter collapsed and the coupling removed therefrom. The pliable collar is then separated from the coupling.

BACKGROUND OF THE INVENTION 
This invention relates to plain-end pipe couplings and a method and 
apparatus for manufacturing same and more specifically, to plain-end pipe 
couplings made of fibrous glass reinforced plastic wrapped or applied on a 
collapsible mandrel utilizing a polyurethane mold collar and, to a method 
and apparatus for manufacturing same. 
Many underground water systems have historically been made of vitrous clay 
pipe coupled together at abutting ends by a bell and a spigot. Of late 
attempts have been made to utilize "plain-end" pipes, or pipes that have a 
uniform diameter throughout their whole length. Plain-end pipes have been 
found to be more efficient to produce but are problematic in respect to 
providing an adequate watertight seal at their junction. 
Water leakage can occur axially along an outer cylindrical surface of the 
pipe as a result of a coupling that doesn't seal the pipe thouroughly. 
This usually occurs because either because of a size or shape difference 
the coupling lacks adequate sealing ability around the coupling mating 
surface of the pipe or because of a non-uniformity in the diameter of the 
pipe at the point of sealing. Leakage can also occur because of a shear 
strain occuring in the coupling at the point of the junction between the 
pipes themselves. 
In many prior art couplings, the coupling is unable to provide a seal along 
the total cylindrical surface of the pipe or, if able to provide an 
adequate seal as such, the couplings are normally pliable or nonrigid in 
nature and do not have the required structural strength or integrity to 
resist forces acting in a shear direction between the two pipe ends, 
thereby allowing the pipe to separate and/or the pipes and the coupling to 
separate and therefore produce a water leak. 
Another drawback in the prior art is associated with the complicated design 
of many of the conventional couplings, some of which couplings have had an 
elastomeric binding with fibers fabricated therearound. Other conventional 
couplings have had an inner section situated between two outer end 
sections with each section being laminated with different materials. 
OBJECTS OF THE INVENTION 
Therefore, the objects of this invention are: to provide a pipe coupling 
for plain-end pipes that is capable of preventing water leakage both in 
axial and in shear directions; to provide such a coupling that is rigid; 
to provide such a rigid coupling which, when used with elastomeric gaskets 
positioned about the ends of the pipes, will prevent water leakage 
therearound; to provide a method of manufacturing such a coupling that 
comprises winding or applying curable fiber reinforced plastic material on 
a removable polyurethane collar which collar has an irregular outer 
surface which surface defines an inwardly projecting cavity on the inner 
surface of the coupling; to provide such a method which allows simple 
repetition thereof on reusable equipment to produce multiple couplings; to 
provide such a collar which is associated with an operably expandable 
mandrel, which mandrel collapses to allow the removal of the collar and 
coupling therefrom; to provide such a mandrel which is operably expandable 
and collapsible; to provide such a collar which is pliable and therefore 
can be manipulated from engaging contact with an inner cylindrical surface 
of a cured coupling; to provide such a mandrel and collar which are easy 
to manufacture and use; to provide such a coupling which is simple in 
design, relatively inexpensive to produce, easy to manufacture and 
particularly well adapted for the proposed usage thereof. 
Other objects and advantages of this invention will become apparent from 
the following description taken in connection with the accompanying 
drawings wherein are set forth, by way of illustration and example, 
certain embodiments of this invention. 
SUMMARY OF THE INVENTION 
A pipe coupling device for plain-end pipes is provided which comprises a 
rigid generally cylindrically shaped sleeve wound from continuous strands 
of fiber soaked in rigid or hard curing resin. A pliable, resilient, 
generally cylindrical collar having an irregular outer surface is received 
on an operably expandable and rotatable mandrel. The strands are wound on 
the collar to form an annular coupling and thereafter the plastic is 
cured. The mandrel is collapsed to allow the removal therefrom of the 
collar and coupling which collar is pliable and is manipulated so as to 
remove same from engagable contact an inner surface of the coupling. The 
inner surface of the coupling conforms to irregularities existing in an 
outer surface of the collar. Preferably, inwardly extending ridges are 
formed on the coupling inner surface defining therebetween a cavity, such 
ridges being adapted for facilitating the coupling of two pipes. 
The drawings constitute a part of this specification and include exemplary 
embodiments of the present invention and illustrate various objects and 
features thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
As required, detailed embodiments of the present invention are disclosed 
herein; however, it is to be understood that the disclosed embodiments are 
merely exemplary of the invention which may be embodied in various forms. 
Therefore, specific structural and functional details disclosed herein are 
not to be interpreted as limiting, but merely as a basis for the claims 
and as a representative basis for teaching one skilled in the art to 
variously employ the present invention in virtually any appropriately 
detailed structure. 
Referring in more detail to the drawings. 
The numeral 1 generally represents an operably expandable and collapsible 
mandrel. The mandrel comprises two half sections, a first 3 and a second 
5, and is adapted to rotate on a shaft 7 which is connected to a rotating 
means (not shown). A pliable, resilient form collar 9 made of an 
elastomeric material is placed on the mandrel 1 when such a mandrel is in 
a collapsed position by sliding thereon. The collar 9 is snugly fitted to 
the mandrel 1 when the latter is in an expanded position thereof. A 
curable and formable material which, when cured, will harden, such as 
continuous ribbons 14 of fiber impregnated with plastic, for instance, the 
type generally marketed under the trademark Fiberglas, is applied to an 
outer surface 10 of the collar 9. When cured the material will comprise a 
rigid annular member shown here as a pipe coupling 17, which coupling has 
inwardly projecting ridges 19 and 20. 
Referring more particularly to FIGS. 7 and 10, the mandrel 1 comprises a 
circular back plate 21, which has attached thereto the first half section 
3. The first half section 3 has a substantially cylindrical outer surface 
23 and a front web portion 25. Reinforcing plates 27, FIG. 7 are provided 
for strengthening. The first half section 3 is secured to the back plate 
21 by welding on the like. A slot 31 is provided in the back plate 21, the 
function of which will be discussed presently. 
The second half section 5 comprises a substantially cylindrical outer 
surface 38 and is mounted on a substantially circular inner plate 40, see 
FIG. 10, an outer surface 41 thereof slidably engaging the back plate 21. 
The inner plate 40 contains therein pairs of slots 43 and 45 through which 
bolts 50 and 52 project. The bolts 50 and 52 are respectively positioned 
at a one end thereof through apertures 46 and 47 in the back plate 21 and 
at the other end thereof through apertures 48 and 49 in two holding plates 
54 and 56. The holding plates 54 and 56 are secured in slidable contact 
with an inner surface 57 of the inner plate 40 by the bolts 50 and 52 
which are held in place by nuts 55 or the like and function to retain the 
back plate 21 and inner plate 40 in slidable contact. The slots 43 and 45 
in the inner plate 40 are aligned such that when the nuts 58 are loosened 
the inner plate 40 can slide relative to the back plate, thereby allowing 
the mandrel 1 to expand or collapse. During normal operation the nuts 58 
are not loosened. 
Mateable tabs 68 and recesses 70 are positioned along edge portions 72 and 
74 of the members defining the first and second outer surfaces 23 and 38, 
respectively, to enhance support provided to the collar 9 when the mandrel 
1 is expanded. 
A toggle assembly, see FIGS. 7 and 12, generally designated 80, is used to 
bias the two half sections 3 and 5 apart and together, thereby expanding 
and collapsing the mandrel 1. A bracket 82 is securely attached to a 
surface 83 of the back plate 21 by bolts 84 or the like. A lever 85, has a 
recess therein (not shown) by means of which the lever 85 is pivotally 
connected to a tab 86 which projects outwardly from the bracket 82 by a 
pin 87. The lever 85 includes first and second lugs 85a and 85b 
respectively which lugs can have force applied thereto to urge the lever 
85 to pivot or rock about the pin 87. The slot 31 in the back plate 21 is 
aligned with the direction of motion of the mandrel back plate 21 relative 
to the plate 40 and receives therethrough an ear 88 which is attached to 
the inner plate outer surface 41. A pair of links 90 is pivotally 
connected by a pin 91 near a first end thereof to the ear 88 and by 
another pin 92 near a second end thereof to the lever 85. The lever arm 85 
when rotated about the pin 87 functionally biases the tab 86 and ear 88 
toward and away from each other thereby operably collapsing or expanding 
the mandrel 1 respectively. 
The collar 9 is of such a size as to slip over the mandrel 1 as shown in 
FIG. 1, when such mandrel is in a collapsed position, and further is of 
such a diameter that, when expanded, the mandrel 1 is slightly larger in 
diameter than the collar 9 thereby requiring the collar 9 to elastically 
expand somewhat and thus snugly retaining the collar 9 on the mandrel 1. 
The collar 9 has an outer arcuate or generally circular surface 95, FIG. 
11, which is uneven or irregular in contour. These irregularities are 
transferred in reverse to an inner surface 98, FIG. 11, of the pipe 
coupling 17, preferably forming thereon the inwardly projecting 
circumferential ridges 19 near each opposing end of the coupling 17 and 
the ridge 20 near a center portion of the coupling 17. 
The collar 9, as shown, is molded of a pliable, resilient material such as 
polyurethane or the like which will allow the collar 9 to be manipulated 
and removed from the inside surface 98 of the rigid and cured coupling 17, 
as seen in FIG. 4. Also, the collar material must be strong enough so as 
not to deform excessively when winding the ribbons 14 thereon. It has been 
found that a material having a durometer reading of 55 to 60 is adequate 
but other materials may perform equally well. 
A device to mold the collar 9 is shown in FIG. 6 and is designated 
generally by the numeral 114. The mold device 114 comprises a side member 
116 and a brace 118, an inner arcuate member 120 which molds or forms a 
generally cylindrical mandrel engaging surface 122 on the collar 9, and an 
outer arcuate member 124 which is generally cylindrical with 
circumferential irregularities 126 on a surface thereof. The inner surface 
of the arcuate member 124 defines a mold for the outer collar surface 95. 
Bolts 128 or the like are provided which function to hold the mold device 
114 together while forming the collar 9. During formation of the collar 9, 
the mold device 114 is placed with the side member 116 down and plastic 
elastomeric or the like material is poured between the members 122 and 
124. An aperture or open top 130 is provided 124 to allow the pouring 
therethrough of the material used to form the collar 9. 
The pipe coupling 17, which can be seen in cross section in FIG. 11, 
comprises a rigid annular member having spaced apart arcuate surfaces 
which, in this example, are two substantially concentric generally 
cylindrical or circular surfaces, the inner surface 98 and an outer 
surface 132. The inner surface 98 has certain circumferential 
irregularities thereon. The coupling is made of a material which when 
cured will harden. As seen in FIG. 11, the ridges 19 and 20 project 
inwardly from the coupling inner surface 98. 
The ridges 19 are each adapted to sealingly engage an elastomeric gasket 
136, as shown in FIG. 8, which gaskets are operably positioned about 
adjacent outer cylindrical surfaces 110 of abutting ends 111 of two 
plain-end pipes 112 which are to be coupled together. 
As shown, the outer surface of each of the mandrel half sections 23 and 38 
are generally semicircular in cross section. Also, the collar 9 is shown 
as being substantially circular. It is envisioned that collars having an 
outer surface of differing shapes, such as ovate, diamond, or rectangular 
could be utilized to mold a pipe coupling to be used with pipes of 
corresponding shapes. When used with various shaped collars, the mandrel 
may be modified to better fit the particular shape of the collar. It is 
also noted that while the coupling 17 of the present embodiment has three 
ridges 19 and 20, it is foreseen that any number or ridges, cavities, or 
even a smooth exterior could be formed on the interior surface of the 
coupling 17. 
In an alternate embodiment as shown in FIG. 9, two semicircular annular 
sleeves 200 and 201 are secured to the outer cylindrical surfaces 23 and 
35 of the half sections 3 and 5. The sleeves 200 and 201 function to 
increase the diameter of the mandrel 1 and are positioned on the half 
sections 3 and 5 such as not to hinder the expanding and collapsing nature 
of the mandrel 1 and attached with screws 202 or the like. With the 
sleeves 200 and 201 attached to the mandrel 1, pipe couplings of diameters 
can be fabricated which differ from the coupling 17 shown in the other 
figures. 
A method for using the mandrel 1 and collar 9 to produce a coupling 17 is 
as follows: 
Material, such as shown here as filaments 140 of fibrous glass to be 
impregnated with plastic are prepared for application on the mandrel 1. 
With reference to FIG. 5, the filaments 140 are drawn from a storage or 
staging area 141 and collated into two strands, with one strand 142 being 
dipped in a tube of a first portion 143 of a curable resin and the other 
strand 144 being dipped in a tube of a second portion 145 of a curable 
resin. Suitable portions 143 and 145 of a curable resin may be a 
conventional catalyst and promotor such as is used in fiber reinforced 
plastics or a suitable equivalent thereof. Soaked strands 148 and 149 exit 
the tubs and are joined. 
Prior to applying the soaked strands 148 and 149 to the mandrel 1, form 
means such as the mold or form collar 9 is preferably placed around the 
mandrel 1 while in the collapsed position thereof, as seen in FIG. 1. The 
mandrel 1 is expanded by rotating the lever 85 in a clockwise direction, 
as seen in FIG. 7, to force the inner plate 40 to slide relative to the 
back plate 21 thereby increasing the diameter of the mandrel 1 and 
snugging or securing the collar 9 thereon. It is foreseen that the form 
means could be an integral portion of the mandrel 1. The lever 85 may be 
actuated by a hydraulic cylinder (not shown) or by means of manual 
manipulation of a handle (not shown) attached thereto. 
A release agent (not shown) may be applied to the collar outer surface, so 
that the cured coupling 17 will not adhere thereto. Also, additional resin 
without a fibrous strand therein may be first applied to the collar outer 
surface 95 to assure that the coupling inner surface 98 will substantially 
have the shape of the collar outer surface 95 without skips or voids 
therein. 
In the present embodiment both prepared or soaked strands 148 and 149 are 
collated into a single ribbon 14 which is then applied to the collar outer 
surface 95. The mandrel 1 is rotated about the shaft 7 which in turn winds 
the ribbon 14 onto the collar 9. While rotating the mandrel 1 the ribbon 
14 may be directed by means (not shown) transversely along the collar 
outer surface 95 to assure a coupling 17 of substantially uniform 
thickness except for the ridges 19 and 20. 
As the ribbon 14 is wound, resistive tension is provided thereto which in 
effect tends to compact the ribbon 14 on the collar 9 and sufficiently mix 
the resin materials in a somewhat homogenous mixture interbetween the 
strands contained in the ribbon 14. After enough thickness is achieved the 
mandrel 1 rotation is stopped and the ribbon 14 severed. A result of the 
compacting of the ribbons 14 while winding is that some of the resin is 
squeezed out of the ribbon 14 to the coupling other surface 132 such that 
this surface cures in a smooth manner. 
The collar 9 is left on the mandrel 1 while the coupling 17 cures. Curing 
generally takes approximately 5 minutes when using infra-red heaters but 
curing may be by self generated reaction or other curing means if time 
permits. After curing, of the coupling 17 the mandrel 1 is collapsed by 
manipulating the toggle 80, and the collar 9 and coupling 17 are removed 
therefrom as a unit, see FIG. 3. The collar 9 is then manipulated, see 
FIG. 4, and removed from engaging contact with the coupling inner surface 
98. 
While the term "annular" is used therein to illustrate a solid object such 
as the collar 9 or coupling 17, having two generally cylindrically shaped 
and spaced surfaces, the term is understood to apply to any solid object 
having two spaced arcuate or nonlinear surfaces. In addition the term 
"curable resin or material" is used herein to describe any of the 
conventional plastics or the like which have a semisolid or manipulative 
state and which harden, cure or the like, whether by time, heat or other 
expedient, to a substantially solid or rigid state. 
It is also foreseen that the reinforcing fiber could be discrete short 
pieces such as chopped fiberglass or alternatively no fiber could be 
utilized if the resin material will provide satisfactory strength to the 
coupling when no fiber or short fibers are utilized. The curable material 
may be applied directly to the mandrel or molding collar. 
It it further foreseen that the present invention could be utilized in 
combination with a plain-end pipe wherein one side of the coupling would 
be applied directly to the pipe and the other end would be formed on a 
mandrel as described herein. In particular the fiber reinforced plastic 
may be wrapped about or applied simultaneously to both an end of the pipe 
and to the mandrel. The mandrel would then be collapsed leaving one end of 
the coupling free to join with a second pipe and the opposite end of the 
coupling fixedly joined to the first pipe. 
It is to be understood that while certain embodiments of the present 
invention have been illustrated and described herein, it is not to be 
limited to the specific forms or arrangement of parts described and shown.