Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF TEIE INVENTION
Field of the Invention
This invention relates to butterfly valves and
to methods for making same. More particularly, the invention
relates to butterfly valves having a molded plastic valve
body and to a method of making such butterfly valves where-
in a disc aasembly is first assembled into a sleeve and then
positioned in a mold cavity for molding the valve body around
the disc assembly.
Description of the Prior Art
A butterfly valve of the present type, but having
the usual machined valve body,is illustrated in U.S. Patent
3,902,697 issued September 2, 1975 to Robinson. The
present invention relates to providing such valves with a
molded valve body with consequent substantial cost savings.
SUMMARY OF THE INVENTION
The present invention provides an improved
butterfly valve wherein the valve body is injection molded
around a pre-assembled disc assembly and a method for making
such a butterfly valve. The method includes assemblying a
rotatable disc and supporting stem in a sleeve, positioning
thè disc assembly in a mold, and then injection molding of
the valve body around the disc assembly. The molded valve
body includes accurately defined bores and internal or
external threads and does not require subsequent machining,
thereby eliminating the expense associated with forming
and machining metal valve bodies typically employed in prior ~;~
art butterfly valves. Furthermore, assembly of the butterfly -
valve is simplified because the disc and stem are pre-
assembled outside the valve body and the component parts are
more readily accessible than is the case when these parts
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must be assembled inside the ~ody. ~-
One aspect of the present invention is defined as : .
a butterfly valve comprising a generally cylindrical metal
sleeve having diametrically opposed aligned apertures therein
transverse the bore of the sleeve, a valve stem projecting ~
through and journaled in the apertures, a plastic valve body ..
molded around the sleeve and the stem and extending to both
sides of the sleeve with a bore on each side of the sleeve
substantially the same configuration as the bore of the sleeve
where~y the sleeve is fixed in the ~ody by the molded material
of the ~ody while providing a substantially smooth bore through
the sleeve and on both sides of the sleeve, at least one end-
of the stem projecting through the body, a valve disc mounted on
the stem for rotation with the stem, a resilient seal mounted in
the periphery of the disc, the disc ~eing rotatable to seat the
seal on the ~ore of the sleeve to shut off flow or into general
alignment with the bore axis for maximum flow.
Another aspect of the present invention involves
. a method for fabricating a ~utterfly valve including a: 20 valve ~ody having a generally cylindrical bore defining a
flow passage therethrough, a rotata~le stem extending trans-
versely of the flow passage, at least one aperture in the
- valve ~ody for receiving the stem, a generally circular disc
carrying a sealing member on the outer periphery thereof
and mounted on.the stem for rotata~le movement within the
flow passage bet~een an open position and a closed position
to shut off flow through the flow passage, the steps comprising
mounting the disc on the stem; positîoning the assembled disc
and stem in a mold having a cavity arranged to define the
valve ~ody with the disc clampingly engaged between a pair
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of cores, thç plane of the disc being transverse to the
longitudinal axis of the cores, and at least one end of
the stem positioned in a bore provided in a wall of the
mold cavity; and injecting a molten thermoplastic material
into the mold cavity to form a molded valve body around
the disc member and the stem.
BRIEF DESCRIPTION OF THE DRAWINGS
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Fig. 1 is a partial cross sectional view of a
mold for use in molding a butterfly valve of the invention,
the mold having an assembled disc assembly and sleeve sup-
ported therein.
Fig. 2 is a perspective view of a butterfly valve
of the invention.
Fig. 3 is a fragmentary, cross sectional! end
elevation view, partially broken away, of the butterfly valve,
showing the disc member in the closed position. ;~
Fig. 4 is a cross sectional side elevation view
of the butterfly valve showing the disc in exploded relation.
Fig. 5 is a fragmentary perspective view of the
inner end portion of one of the core pins of the mold in
Fig. l; and
Fig. 6 is a perspective view of the sealing ring.
DESCRIPTION OF T~E PREFERRED EMBODIMENTS
The butterfly valve of the invention includes an
injection molded plastic valve body 12 having a central,
longitudinally extending cylindrical bore 14 which provides
a fluid flow passage through body 12. The opposite ends
of body 12 can be threaded as shown, one end having an
external threaded portion 13 and the other end having an
internal threaded portion 15, or otherwise constructed for ~`
conventional connection with associated plumbing. ~ody 12
is formed from a molclable thermoplastic material adaptable
for injection molding.
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Referring to Figures 3 and 4, body 12 houses a
generally circular disc 16 which is fixed on a shaft or stem
18 for rotatable movement with the shaft 18 around its axis.
Disc 16 has a diametrically extending, enlarged central hub
portion 20 for receiving stem 18 and opposed annular bosses
24 surrounding the opposite ends of hub portion 20. Disc 16
is rigidly secured to stem 18 by a suitable means, such as
by spot welding.
Disc 16 is surrounded by a generally cylindrical
sleeve 26, preferably constructed from a metal such as brass,
having a smooth-surfaced bore 27 which serves as the valve
seat. Sleeve 26 can also be constructed from other metals
such as stainless steel or from ceramics or plastics which are
thermally compatible with molding temperatures and are compat- -
ible with the type of fluids for which the valve is to be
used. Sleeve 26 is rigidly secured in a groove 28 in bore
14 with opposite ends of sleeve 26 held between shoulders 28a
of the groove 28. The inside dimensions of sleeve bore 27
are substantially equal to the inside dimension of the bore 14
Sleeve 26 further includes a pair of diametrically opposed
apertures 29 ~or receiving the opposite ends of stem 18.
One end of stem 18 is received through an aperture 29
in sleeve 26 an~ is rotatably received in a coaxial recess 30
provided in body 12. The other end of stem 18 extends through
the opposite aperture 29 in sleeve 26 and through a coaxial
aperture 34 provided in body 12. The outer end portion of
shaft 18 projecting through aperture 34 and extending outwardly ~ -
from the valve body includes a flat surface 32 on one side and
receives a handle 42. Handle 42 preferably is molded from the
same thermoplastic material as the valve body and includes a
complementary bore 43 for recelvin~ the outer end of stem 18.
Rotational mo~ement of handle 42 rotates stem 18 and disc 16
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` about the axis of stem l~ ~e~ween a closed posîtion where
the plane of disc 16 is generally at right angles to the
longitudinal axis of bore 14 and an open posi~ion where the
plane of disc 16 is substantially ali~ned with the direction
of fluid flow through the valve.
Sleeve bore 27 includes diametrically opposed
flat or planar portions 50 which surround and are adja~ent
the diametrically opposed apertures 29. When sleeve 26 is
formed from a metal, these planar portions can be formed by
broaching a cylindrical sleeve having a circular cross section.
Sleeve bore 27 also includes diametrically opposed generally
semicircular wall portions 51 extending circumferentially
~etween planar wall portions 50. The outer surface 52 of each ;
boss 24 of disc 16 is flat and is spaced inwardly a small -~ :
distance from the corresponding planar wall portion 50 of
sleeve Z6. Peripheral semicircular portions 53 of disc 16 :
similarly have an outer radius which is slightly less than the
radius of the corresponding semicircular wall portions 51 of
sleeve 26.
A sealing ring 54 is carried in a continuous
peripheral recess or groove 58 provided in the periphery of .:
disc 16. Groove 58 includes opposed annular portions definQd
by bosses 24 and encircling stem hub 22 and further includes
opposed generally semicircular portions which extend between :
bosses 24 and connect the annular portions. Sealing ring 54
preferably is formed as a unitary assembly and includes annular
sections 55 which fit into the annular portions of disc groove ::
58 and semicircuIar sections 56 which join the annular sections
and fit into semicircular portions of disc groove 58. Sealing
ring 54 is preferably made from a relatively resilient material,
such as natural rubber, synthetic elastomers, fluorocarbon
materials and the like
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In order to provide an interference fit be~ween
annular sections 55 of sealing ring 54 and planar portions
50 of sleeve bore 27, each annular section 55 of sealing ring
54 extends outwardly from the annular portion of the disc
groove 58 by a dimension which exceeds the clearance between
the outer surface of boss 24 and planar portion 50. This
interference fit, which is maintained for all positions of
disc 16, causes annular sections 55 of sealing ring 54 to be
compressed radially into sealing engagement with stem 18.
Thus, the annular portions of the sealing ring 54 provides
fluid-tight stem seals at all positions of disc 16.
Disc 16 is convenie~tly constructed from two disc
halves 64 in the manner disclosed in U.S. Robinson Patent
3,902,697 which is incorporated herein by reference. Disc
halves 64 preferably are identically arranged with each includ-
ing a generally semicylindrical central portion and a circum-
ferential flange which, upon face-to-face assembly of disc
halves 64, define hub portion 20 and groove portions 58,
respectively. I~hen disc halves 64 are so constructed, they
can be formed from stamped stainless steel sheet or the like
and attached to stem 18 by spot welding. If desired, disc
halves 64 also can be fastened together to provide further
structural integrity.
Figure 1 illustrates a mold for use in the method -~
of the invention for making the butterfly valve. The m~ld
includes a pair of separable mold halves 70 and 72 which
define a generally cylindrical mold cavity 74, the mold
cavity 74 defining the external shape of the valve body 12
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The mold also includes a pair of a~ially movable and axially
aligned core pins 76 and 78 having opposed, adiacent ends
receivable within the mold cavity and generally cylindrically
shaped to define bore 14 of the molded valve body 12 Each
core pin 76 and 78 is slidably supported for axial movement
by respective pairs of core support plates 100 and 102 and 1~4
and 106. Core support plates 100 and 102 clampingly engage the
outer end of core pin 76 and core support plates 104 and 106
clampingly engage the outer end of core pin 78.
13 Core pin 7g slidably supports a preform sleeve 80
having external threads 81 on the inner end for defining
internal threads 15 in one end of valve body 12. Preform
sleeve 80 is provided with an internal cylindrical bore 82
of a diameter substantially equal to the outer diameter `-
of core pin 78. Preform sleeve 82 also includes a
surrounding annular flange 84. The periphery 86 of flange 84
mates with mold halves 70 and 72 and the planar annular
surface 88 of flange 84 defines an end wall of mold cavity 74.
Mold halves 70 and 72 also include respective
insert portions 89 and 90, which surround core pin 76 and have
internal threaded portions 92a and 92b for defining external
threaded portion 13 of valve ~ody 12. Mold half 72 also
includes a bore 94 which extends from mold cavity 74 trans-
versely to the axis of core pins 76 and 78 and intermediate
the adjacent ends of core pins 76 and 78. Bore 94 receives the
outer end of the valve s~em 18 on which handle 42 is mounted.
Mold half 72 also includes a cavity portion 96 adjacent to
bore 94 for defining an integral stop 98 to be molded onto the
outside of the valve body 12. Stop 92 is provided to restrict
rotational movement of handle 42 toward the open position.
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The method of manufacturing the butterfly
valve includes the steps of assembl.ing disc 16, stem 18 ~nd
sleeve 26 and then placing the resultan~ subassembly in mold
cavity 74 wherein disc 16 is clamped between the ends of core
pins 76 and 78 and with the end of the stem 18 received in
the bore 94. More particularly, sealing ring 54 is positioned
inside bore 27 of sleeve 26 with the plane of sealing ring 54 :
extending perpendicularly to the axis of the flow passag~
through sleeve 26 and annular sections 55 aligned with sLeeve
apertures 29. That is, sealing ring 54 is located in a position
corresponding to the closed position of disc 16. Stem 18 is
then inserted through sleeve apertures 29 and through the
aligned annular sections 55 of sealing ring 54. Disc halves 64
are then positioned in face-to-face relationship on opposite
sides of the stem 18 such that the hub portions 20 of disc
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halves 64 surround the stem 18, bosses 24 of disc halves 64
surround annular sections 55 of sealing ring 54, and the
peripheral flanges of disc halves 64 clampingly engage semi-
circular sections 56 of sealing ring 54. Disc halves 64 are
then secured to each other and to the stem 18 by spot welding
or the like.
The assembled disc assembly and sleeve 26 is then
positioned in mold cavity 74 in the manner shown in Figure 1
with the disc assembly clamped between the ends of core pins
76 and 78. The ends of core pins 76 and 78 have an outer
dimensions substantially equal to the inside dimension of
sleeve bore 27 and the inner end of each core pins 76 and 78
has a configuration complementary to an outer face of disc
halves 64 as shown in Fig. 5. ~hus, the core pins clampingly
engage the disc assembly therebetween with the inner ends of core
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pins 76 and 7~ received wichin slee~e 26. As sho~m in
Figure l, preform sleeve 80 is also positioned on the
core 78.
A molten thermoplastic material is then injected
into the mold cavity 74 under pressure to form valve body 12
around sleeve 26. After cooling to solidify the thermo- ;
plastic material, the mold is then opened, i.e., mold halves
70 and 72 are moved in a d rection away from and transverse ~o
the axis of the valve bore 14 and core pins 76 and 78 are
moved axially out of valve bore 14. As the molded valve
body is removed from the mold cavity, core pin 78 slides
axially out of bore 82 in preform sleeve 80 and preform sleeve
~0 is subsequently unthreaded from the valve body 12 to leave
internal threads 15. After molding of the valve body 12 has
been completed, handle 42 can be installed on the outer end
of the stem 18 which was received within bore 94 in mold
half 72 durin~ the moldin~ process.
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