Note: Descriptions are shown in the official language in which they were submitted.
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ackgroun~ of the Invention
My Canadian Patent No. 940,395, issued January 22, 1974 shows a
linear piston operator having tw~ axially aligned pistons connected ky a bar -
mounting two spaced rollers for selectively engaging opposite sides o a
crank arm having a collar keyed to a valve st~m extending txansversely
through a circul æ notch in the piston housing, and a transverse tubular
housing for the valve stem and collar cut out to conform to and enclose the
notch and welded to the e ges thereof. That construction provided a sealed
enclosure for storing high press~re fluid in the cavity within the piston
housing between the two pistons.
A disadvantage of that construction is that in an intermediate
position of the valve stem ket~een fully open and fully closed valve posi-
tions, control of the valve stem is not positive as some floating or drift-
ing of the valve can occur kecause of the space ketween the crank arm and one
of the rollers of the piston oonnector bar. A scotch-yoke connector having
a constan sliding engagement with a single roller on the piston connector
~ar produoe s positive control of the valve in all positions, but the slot in ~-
the yoke requires substantial mass on koth sides of the slot and conseguent
increased overall width to provide the necessary s~rength to absorb piston P~
thrust. Consequently, a m~ch larger notch in the piston housing is required
to acoommDdate the increased width of the scotch-yoke as it oscillates
between valve cp~n and closed positions, and such notch substantially
weakens the resistance of the cylinder wall to high internal pressures
when high pressure fluid is stored in the cavity ketween the two pisto~s.
Sumc~ry of the Invention
The present invention provides a linear piston operator for a
rotary valve having a single cylinder, a piston in the cylinder, a connectcr
bar oonnected to the piston, and a rotary valve stem member extending trans-
ver æ ly and substantially tangentially of the cylinder. The cyIinder has
a longitudinal slot adjacent the valve stem, an oscillatable element
operatively connecting the connector kar to the valve stem memker and
extending through the slot during oscillation, and a housing partially
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surrounding the stem nE~ber cm d bridging over the slot c~nd having its ends
welded to the cylinder at the ends of the slot. The housing has tWD
longitudinal side bar portions w7elded to the cylin~Pr along the sides of
the slot, the side bar portions extending laterally from their weldments
a substantial distanoe into the cylinder to increase reinforcement thereof.
Preferably, the cylinder has two axially c~ligned spaced-ap~rt
pistons therein, and the connector bar connects the tWD pistons.
The valve stem nEmker may be journaled in the two longitudinal
side bars.
1~ The housing may form a sealed enclosure for a pressure fluid ~ ~
storage cavit~ between the t~ pistons. -
The oscillatable element may be a crank arm secured to the valve
stem me~ber and pivotally connected at its outer end to the aonnector bar.
The housing may form a sealed enclosure at one side of the piston,
and the ends of the cylinder may have ports for introducing and exhausting
pressure fluid.
Preferred embodIments of the invention are shown ky way of
example in the accc~panying drawings and described in the foll~wing speci-
fication. Various mDdifications and changes in details of construction
are co~prehended within the scope of the appended claims.
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Description of the Drawings
Fig. 1 is a longitudinal sectional view, partly in
elevation of one embodiment of the improved piston operator,
showing the scotch-yoke at one end of its stroke.
Fig. 2 is an end elevational view thereof.
Fig. 3 is a cross-sectional view on line 3-3 of Fig.
1, showing the scotch-yoke at the middle of its stroke.
Fig. 4 is a partial side elevation on line 4-4 of
Fig. 2.
Fig. 5 is a longitudinal sectional view, partly in
elevation, of another embodiment of the improved piston operator
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having a single piston within the cylinder, and a connector bar
and crank arm connecting the piston to the valve stem element
enclosed within the improved housing. ~ `
Fig. 6 is a side elevation with parts broken away.
Fig. 7 is a cross-sectional view on line 7-7 of Fig. 6
showing the crank arm at the middle of its stroke.
Description of One Preferred Embodiment
The cylinder indicated generally at 10 may be formed
20 of standard steel tubing and has end caps 11 which are held to- ~-
gether tightly closing the ends of the cylinder by tie bolts 12
extending through diametrically opposite ears I3 on the end ~ ;
caps.
Within the cylinder 10 are two axially aligned pistons
14 connected in spaced relation by a bar 15 by means of bolts
16 extending through the pistons and screwed into the ends 15' ~
of the connector bar 15. The heads of the bolts 16 are prefer- -
ably recessed within the outer faces of the pistons, and are
adapted to abut the inner ends of adjusting screws 17 extend-
ing through the end caps ll for the purpose of varying the stroke
of the pistons. As shown, the adjusting screws 17 preferably
have sealing caps 18 which embody O-rings l9 and 20 encircling
the screws.
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The connector bar 15 may be circular in cross section -~
having a diameter substantially less than the inner diameter ~-
of the cylinder, and is provided with a longitudinal slot 22
extending between the ends 15' and laterally through the bar.
Midway of the ends of the slot 22 a roller mounting pin 24
extends across the slot with its ends secured in opposite sides
of the bax 15, and a tubular roller 25 is journaled on pin 24
within the slot.
A longitudinal slot 26 is cut in the wall of the cyl-
10 inder 10 midway of its ends and laterally opposite to the slot ~ ~ ;
22, and the valve stem 28 of a rotary valve (not shown) extends
through the slot transversely of the cylinder and substantially
tangentially thereto. A scotch-yoke 29 extends through slot 26
and operatively connects the valve stem 28 to the roller 25
traversing the slot 22 in the bar 15.
As shown, the scotch-yoke 29 has an end portion encir-
cling valve stem 28 and secured thereon by a key 30. The other -~
end of the scotch-yoke has an open slot 31 therein in which the
roller 25 is movably engaged. The ends 15' of slot 22 are `
spaced apart sufficiently to provide clearance for the scotch-
yoke at the ends of its stroke.
The housing which encloses the slot and surrounds the
valve stem and scotch-yoke also provides a sealed enclosure for
the cavity in the cylinder between the pistons 14 so that it can ~-
be used to store high pressure fluid. As shown, this housing may
comprise a curved substantially semi-cylindrical section 32
having its axis of curvature transverse to the axis of curvature
of cylinder 10 bridging over and having its ends welded at 33 to
the ends of the slot 26, and said section being sandwiched
30 between two bars 34 extending along the sides of the slot and -
welded at 35 to the cylinder, and at 36 to the edges of sec-
tion 32.
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Since extremely high pressure fluid may be stored in
the cylinder between the pistons, it is necessary that the sides
of the slot 26 be reinforced against spreading, and accordingly
the bars 34 are required to have substantial mass and weight.
For the same reason, it is desirable to provide stitch welds 37
on the interior of the ends of the curved section 32 to prevent ~ ,
them from bowing radially and weakening the exterior weldments 33.
Obviously, the housing surrounding the valve stem ~ ;
could be formed in a different manner, for example, by machining
an arcuate cavity in one face of a block of steel, but the side
and end portions of the block would be required to have suffi-
cient mass to reinforce the sides of the slot against spreading
due to high internal pressures.
As shown in Fig. 3, the valve stem 28 is journaled
in the reinforcing bars 34 of the housing by means of bearing ,~
bushings 38 held in place by plates 39 abutting the outer faces
of the bars 34 and secured thereto by cap screws 40. O-ring
seals are provided around the stem. The substantial mass of the
bars 34 provides strong and stable bearing supports for the
valve stem.
In the operation of the improved piston operator of
Figs. 1 - 4, assuming that the scotch~yoke is in the full line
position of Fig. 1, pressure fluid is introduced through a port
42 in the right hand end cap 11 and exhausted through a duplicate
port 42 in the other end cap. This causes the pistons 14 to
move to the left and the roller 25 and scotch-yoke 29 to rotate
the valve stem 28 counterclockwise as viewed in Fig. 1. If it
is desired to hold the valve stem in a position intermediate the
open and closed position of the valve, shutting off the fluid
pressure to the cylinder positively holds the valve stem in the
desired position because the engagement of the roller 25 in the
slot 31 prevents floating of the valve.
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The cavity in the cylinder 10 between pistons 14 may
be utilized for storing a supply of pressure fluid because the
housing comprising the arcuate section 32 and the bars 34 pro- -
vides a sealed enclosure over the slot 26. Preferably, angular
ports 44 are provided in one of the bars 34 for communicating
with the pressure fluid in this cavity. Because of the rein-
forcement around the slot 26 by the housing enclosing it, fluid
at extremely high pressure may be stored. One use for such
stored pressure fluid is in case the pressure supply to operate
the pistons fails, in which case the stored pressure may be con-
nected to one o~ the ports 42 to rotate the valve stem 28 and
operate the valve. , -
Description of a Second Preferred Embodiment
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The cylinder indicated generally at 110 may be con- ~ -
structed the same as cylinder 10 of standard steel tubing with
end caps 111 held together by tie bolts 112. Reciprocable within ~;
cylinder 110 is a single piston 114 having a transverse wrist
pin 145 therein pivotally connected to one end of a connector
bar 146. The other end of bar 146 is a clevis 147 pivotally
connected by pin 148 to one end of an oscillatable crank arm 149
having its other end welded to a collar 150 encircling the valve
stem member 128 and non-rotatively secured thereto by keys 130.
Preferably, the end caps 111 have adjusting screws 117
therein for abutting the end of the crank arm ~ at one end of
the cylinder and the face of piston 114 at the other end of the ~ ;
cylinder, so that the stroke of the piston may be varied.
A longitudinal slot 126 is cut in the wall of the cyl-
inder 110 adjacent one end thereof, and the valve stem member
128 extends through the slot transversely of the cylinder and
substantially tangentially thereto. The crank arm 149 extends
through said slot 126.
The housing which encloses the slot 126 and surrounds ~ -
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the valve stem member 128 and crank arm 148 is constructed ~imi~
larly to the housing of Figs. 1 - 4 and provides a sealed en-
closure for the chamber in the cylinder on the inner side of
piston 114. The housing preferably comprises a curved substan-
tially semi-cylindrical section 132 having its axis of curvature
transverse to the axis of curvature of cylinder 110, bridging
over and having its ends welded to the ends of the slot 126, and
said section being sandwiched between two bars 134 extending
along the sides of the slot and welded at 135 to the cylinder and
at 135 to the edges of section 132.
As shown in Fig. 7, the reinforcing bars 134 extend
into the cylinder 110 at their inner ends, as the cylinder 110
is of relatively larger diameter than cylinder 10 and the slot
126 is deeper than slot 26. Thus, the bars 134 have increased
depths so as to give increased reinforcement to the cylinder
against bellying out under pressure. Cap screws 137 may be
provided to tie the bars 134 together within the ends of curved
section 132.
The valve stem member 128 is journaled in the rein-
forcing bars 134 of the housing by bearing bushings 138 held in
place by plates 139 abutting the outer faces of the bars 134 and
secured thereto by cap screws 140. O-ring seals are provided
around the stem member. An indicator plate 152 may be secured
to the end of valve stem member 128 for indicating the position
of the valve (not shown) to which it is connected. ~
In the operation of the piston operator of Figs. 5 - 7, -;
assuming that the piston 114 is in the position of Fig. 5,
pressure fluid is introduced through a port 142 in the right hand
end cap 111 and exhausted through a duplicate port 142 in the ;
other end cap, causing the piston 114 to move to the left and
rotate the crank arm 149 counterclockwise. The crank arm connec-
tion with connector bar 146 provides for positively holding the ;~;
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valve stem member 128 in an intermediate position if desired.
While the construction of Figs. 5 - 7 produces maximum
torque at the center of the stroke rather than at the beginning,
sufficient starting torque is readily obtained by increasing the
diameter of the piston and cylinder, and the increased size of
the cylinder enables extending the reinforcing bars farther
into the cylinder to reinforce it against bellying out under
high internal pressure.
Moreover, the construction of Figs. 5 - 7 is easily
assembled by connecting the piston, connector bar and crank arm
together, and then inserting them, crank arm first, through the
left end of the cylinder. When the crank arm reaches the arcu-
ate chamber formed by section 132 between the bars 134 it drops
down into the chamber in position to receive the valve stem ;
shaft 128 which is then inserted transversely of the chamber.
To disassemble, this procedure is reversed.
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