Plastic coated valve rotor and a method of manufacturing

A method of manufacturing a valve rotor with a wear-resistant, low-friction surface, wherein a disk having angled edges and a shape which correspond with the surface of the rotor is formed from a sheet of polytetrafluoroethylene (PTFE). The disk is placed at the bottom of a mold cavity, and a plastic material is injected in the mold. The plastic fills the mold cavity surrounding and covering the angled edges of the disk. Once hardened, the plastic is locked together with the angled edges of the PTFE disk. In a preferred embodiment, a method of manufacturing a water treatment valve rotor with a PTFE rotating surface is shown.

FIELD OF THE INVENTION 
The present invention relates generally to a valve rotor with a 
wear-resistant, low friction plastic surface, and a method for 
manufacturing the valve rotor. More particularly, the invention relates to 
a water treatment valve and a valve rotor with a wear-resistant, low 
friction rotating seal surface, and a method of manufacturing the valve 
rotor. 
BACKGROUND OF THE INVENTION 
Fluid handling systems and other fluid valve systems include a valve having 
a rotor. The rotor often includes a plastic disk with various ports. As 
the disk rotor rotates, the various ports control the flow of fluid 
through the valve. 
Typically, an electric motor is coupled to the rotor to provide the 
rotational movement of the rotor. A motor control is used to control 
activation of the motor as required by the system. The size of the motor 
is dictated by several factors including the rotational load of the rotor 
and the breakaway torque necessary to start rotation of the rotor from a 
resting position. The necessary breakaway torque is dependent, in part, on 
the friction of the rotating surface of the disk and the eccentric 
actuating forces applied to the rotor during rotation which tend to lift, 
or cant, the rotor, causing extensive tension. It is therefore desirable 
to provide a disk rotor having a low friction surface. 
As fluid handling systems often have a long service life, the opportunity 
is present for contaminants (lime, iron, rust etc.) to build up on the 
disk producing a rough surface which increases the coefficient of 
friction. The combination of the rotor ports and contaminated disk surface 
tend to displace and further wear the stationary rubber gaskets engaged 
with the rotating disk. 
Various prior art systems have addressed the issue of low friction 
surfaces, as well as improving other properties of the component parts. 
In various fluid-handling systems where high pressures and temperatures are 
present, there is a demand for component parts with improved pressure and 
heat-resistant properties. Increases in the variety of chemicals and 
liquids encountered in fluid-handling systems have created a greater need 
for corrosion-resistant component parts. One of the known methods for 
improving the corrosion and wear resistance of components is to cover the 
surface of the system components with a coating of an appropriate 
material. 
A variety of materials have been used in the past as corrosion resistant 
coatings, including polytetrafluoroethylene (PTFE) and other fluorocarbon 
polymers. PTFE, also known under the trademark Teflon, is used in 
protecting and improving properties of various component units, such as 
liquid control valves and the components thereof. In the form of a 
powdered resin, PTFE can be molded in sheets and other shapes, or directly 
into a finished part of a product. Sheets, bars, or other shapes of 
compression molded PTFE are used to create many useful articles that take 
advantage of its chemically impervious nature and low coefficient of 
friction. 
Valves and valve components using such material as a lining or coating have 
been described or suggested, as for example, in U.S. Pat. No. 3,537,700, 
which discloses a corrosion resistant coating formed on the base member by 
an isostatic compression using granular polymeric PTFE powder, then 
removed and heated to a temperature above the gel point of PTFE. The 
process is costly, and the coating is not reliable when used under 
pressure and high temperatures. Present methods of coating molded articles 
with adhesive-free polymers are also unsatisfactory. Often the bond 
between the coating and article surface is inconsistent, resulting in 
separation of the coating from the molded article. 
U.S. Pat. No. 5,295,520 discloses a rotary face valve which has been used 
in carousel-type beverage fillers. Positioned within the body is a Teflon 
disk which provides the dynamic sealing surface for engagement by the 
valve rotor. An adjustable spring provides a bias force which urges the 
rotor against the disk. Passages formed in the valve body and Teflon disk 
communicate with the various lines and nozzle and cooperate with 
connecting passages in the valve rotor. 
U.S. Pat. No. 5,296,183 discloses a method, particularly for comolding a 
property enhancing coating and composite articles, which is provided by 
applying the coating, such as Teflon, to a formed and shaped carrier 
substrate which is placed into the mold. Plastic is injected into the mold 
such that the plastic infiltrates the irregularities in the coating 
surface during molding and therefore locks the coating to the part after 
curing. 
A method for manufacturing a valve disk of a synthetic resin powder 
material is described in U.S. Pat. No. 4,172,112. The method includes 
pressure-molding two valve disk cover segments from a tetrofluoroethylene 
resin, molding the formed segments with a previously made disk-like core 
therebetween under high pressure, and then heating the valve disk segments 
which have been compacted and bonded integrally with the core. This method 
is complicated, requires expensive high pressure molding equipment, and 
may be effective only when a fully covered article of a complicated 
configuration is required. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to reduce the manufacturing cost 
of a fluid handling system having a motor driven fluid valve. 
It is further object of the present invention to reduce the torque output 
requirement of an electric motor in a fluid handling system. 
It is still a further object of the present invention to provide a 
fluid-handling valve having a disk rotor with improved breakaway torque 
characteristics and longer product life. 
Yet a further object of the present invention is to provide a retro-fit 
valve rotor having improved break-away torque characteristics. 
Yet still a further object of the present invention is to provide a method 
for applying wear-resistant, low friction, adhesive-free coatings to a 
molded valve rotor. 
It is still a further object to provide a manufacturing method to 
incorporate a wear-resistant, low friction coating in a valve to reduce 
production steps and minimize costs. 
These and other objects, features, and advantages of the present invention 
will become apparent from the following description when taken in 
conjunction with the accompanying drawings, which illustrate a preferred 
embodiment of the present invention. 
The present invention provides a method of manufacturing a valve rotor with 
a wear-resistant, low friction rotating surface, comprising, providing a 
disk formed from a fluorocarbon polymer, the disk having a shape and an 
edge which correspond with the rotating surface of the valve rotor, 
placing the disk at the bottom of a cavity of a provided injection mold, 
injecting flowable material into the mold such that the material fills a 
portion of the mold cavity, substantially surrounding and covering the 
edge of the disk, solidifying the material to lock with the disk and to 
form a rotor disk, removing the rotor disk from the mold, and securing the 
rotor disk to the base of the valve rotor with the disk facing outwardly 
and providing the rotating surface. 
The present invention also provides a rotor for operation in a rotary valve 
comprising a base with flow ports, the base having a first disk and a 
second disk, the first disk being secured to the base and being formed 
from a non-metallic material and having passages which correspond with the 
flow ports of the base, and the second disk being formed from a polymer 
material having a shape corresponding to the first disk including passages 
which correspond with the flow ports of the base, a shaft extending from 
the base, and means for locking the first disk to the second disk. 
The present invention also provides a rotary valve comprising a valve 
housing, a rotor received by the valve housing, the rotor having a base 
with flow ports, the base having a first disk and a second disk, the first 
disk being secured to the base and being formed from a non-metallic 
material and having passages which correspond with the flow ports of the 
base, and the second disk being formed from a polymer material having a 
shape corresponding to the first disk including passages which correspond 
with the flow ports of the base, a shaft extending from the base, and 
means for locking the first disk to the second disk, and a valve cover 
securable to the valve housing. 
In the illustrated embodiment of a rotor, in according with the present 
invention, the rotor is provided with a rotor disk having a shape and 
passages which are compatible with prior art rotor disks. Therefore, the 
present rotor can be substituted as a replacement rotor for existing prior 
art valves without any substantial modification. The use of a Teflon disk 
reduces the co-efficient of friction and the accumulation of contaminants. 
Significantly, experimental results have shown a 50% reduction in the 
break-away torque in converting from a plastic sliding surface to a Teflon 
sliding surface for a rotor disk. The reduction in break-away torque 
provides the advantage that a motor of reduced size and cost may be used.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Illustrated in FIG. 1 is an assembly 10 of a rotary valve for water 
treatment, which includes a valve body 12 with an inlet 14, an outlet 16, 
a valve chamber 18, a valve cover 20, and a rotor 30. 
As best shown in FIG. 2 and FIG. 3, the rotor 30 includes a base 32 with 
flow ports 34, a shaft 36 extending from the base 32, and a rotor disk 38 
attached to the base 32 in order to form a low-friction rotating surface 
40. The rotor disk 38 comprises a Teflon disk 42 interlocked with a molded 
plastic disk 44 having passages 46 which correspond to the flow ports 34 
in the rotor base 32. The molded plastic disk 44 is provided with an 
angular flange 48 extending along the perimeter, and angled borders 50 
surrounding passages 46. FIG. 4 shows the Teflon disk 42 which was stamped 
from a sheet of Teflon 52 (see FIG. 10). The thickness of the Teflon sheet 
52 ranges from 0.015 inch to 0.060 inch. One surface 54 of the Teflon 
sheet may be pre-treated with an etchant and a primer. The stamping die 
(not shown) cuts the Teflon sheet such as to make a beveled or angled 
perimeter edge 56 and beveled or angled passage edges 58 as best seen in 
FIG. 4 and 5. The cut angle .varies. is shown in FIGS. 5 and 6, where 60 
is the pre-treated surface of the disk 42. The passages 62 of Teflon disk 
42 shown in FIG. 4 correspond to the passages 46 of the molded plastic 
disk 44, but are larger in order to allow the flange 48 and borders 50 of 
the molded plastic disk 44 to lock with the corresponding angled edges 56 
and 58 of the Teflon disk 42 as shown in FIG. 7. The rotor disk 38 
manufactured by the method of the present invention is shown in FIG. 3. 
The rotor disk 38 includes a Teflon surface 40, angular flange 48, and 
passages 46 surrounded with molded plastic borders 50. The other surface 
64 of rotor disk 38 is made of plastic and, as shown in FIG. 2, is 
attached to the base 32 of the rotor 30 by a layer of cement 66. 
Description will next be made of the manufacturing method of the rotor 30 
of the present invention with reference to FIGS. 8-10. 
The rotating surface of the rotor according to the present invention is 
formed from the sheet 52 of polytetrafluoroethylene, or Teflon. In order 
to provide optimum toughness and durability, the thickness of the Teflon 
52 sheet should be from 0.015 inch to 0.060 inch. One side 54 the Teflon 
sheet 52 may be pre-treated by an etchant and a primer. An example of a 
polytetrafluoroethylene primer which may be used is Dupont Teflon Primer 
852-201. Using a stamping die (not shown), the Teflon disk 42 of required 
configuration is cut out of the Teflon sheet 52 such that all edges 56, 58 
of the disk 42, including those of the perimeter and the passages 62, are 
inclined inwardly away from the pre-treated surface 60 providing a cut 
angle .varies., as best shown in FIGS. 5 and 6. 
The Teflon disk 42 is then placed on the bottom of the cavity 68 of a first 
portion 70 of a provided injection mold 72 with the pre-treated surface 60 
(if applicable) facing outwardly. For orientation purposes the Teflon disk 
42 is provided with three holes 74 held to a close-tolerance dimension so 
that, when inserted in the mold 72, the Teflon disk 42 has the proper 
position. The first portion 70 is brought into engagement with a second 
portion or cover 76, and a flowable plastic is injected through the inlet 
78 to fill the mold cavity 68. The flowable plastic may be any thermo 
plastic molded material, preferably of high strength, such as Noryl or 
ABS. The cover 76 is constructed with approximately twenty one 
strategically placed pins 80, examples of which are shown in FIGS. 8 and 
9. The function of the pins 80 is to hold the Teflon disk 42 against the 
bottom 82 of the mold cavity 68 so that the injected plastic will not flow 
around over the rotating surface 40 of the Teflon disk 42. The inlet 78 is 
provided above the Teflon disk 42 to further reduce the possibility of 
injected molded plastic flowing between the rotating surface 40 of the 
disk and the first portion 70 of the mold 72. The passages 62 in the 
Teflon disk 42 are larger than those of the molded plastic disk 46. The 
effect of this is to allow the molten plastic to fully cover the edges of 
the Teflon disk passages 62. After solidification, the plastic forms the 
raised angled borders 50 which surround the passages 46. These borders 50 
together with the angular flange 48 formed along the perimeter, 
mechanically lock the Teflon disk 42 by virtue of the cut angle. The 
combined rotor disk 38 is removed from the mold. The side of the rotor 
disk 38 having the molded plastic disk 44 is attached to the rotor base 32 
with a layer of cement, glue, or other compound 66. Alternatively, the 
rotor disk 38 is fusion bonded to the rotor base 32. In this instance, the 
rotor base 32 is preferably made of a glass filled plastic material to 
provide greater bonding strength. The side of the rotor disk 38 having the 
Teflon disk 42 provides the rotating surface 40 for the rotor 30. 
With reference to FIG. 1, the rotary valve of the present invention further 
includes chambers walls 92 forming the valve chambers 18. The chamber 
walls 92 include a groove 94 for receiving a rubber gasket 96. A plastic 
wear strip 98 is also received by the groove 94 on top of the rubber 
gasket 96 to reduce the likelihood of the disk 42 from wedging the rubber 
gasket 96 out of the groove 94 and to reduce build up of contaminants on 
the disk 42. The plastic wear strip 98 may be made of a high density 
polyethylene, or it may be made of a flourocarbon such as Teflon. 
The rotary valve further includes a safety shut-off piston 100 located in 
one of the chambers 18. The piston 100 is biased outwardly of the one 
chamber 18 by means of a spring 102. The piston 100 is designed to block 
one of the (circular) passages 46 in the event the valve breaks down, if 
the piston 100 and one passage 46 should align, in order to avoid an 
overflow. To reduce friction and contaminants, the piston 100 includes a 
recessed portion 104 which receives a Teflon piston disk 106. 
The forgoing description and drawings were given for illustrative purposes 
only. It should be understood that the invention is not limited to the 
embodiments disclosed but is intended to embrace any and all alternatives, 
equivalents, modifications, and rearrangements of elements falling within 
the scope of the invention as defined by the claims.