Compact expanding gate valve

A compact expanding gate valve having a valve body defining a flowway and having spaced internal seat rings. Guide elements project internally from the valve body. A valve stem driven gate and segment assembly is movable within the valve body between open and closed positions relative to the seat rings and has control arms mounted by actuating pins to each side of gate and segment members of the gate and segment assembly. The control arms are movable linearly with the gate and segment assembly and are disposed in guided relation with the guide elements during opening and closing movement. During initial movement of the gate and segment assembly from the closed position, the pinned connection of the control arms to the gate member and the segment member causes the control arms to pivot responsive to relative linear movement of the gate and segment members and apply collapsing force to the gate and segment members to collapse the gate and segment assembly to minimize frictional contact thereof with the seat rings and permit its movement by the valve stem from the closed position to the open position.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention is directed generally to gate valves for pipe lines 
and the like and more specifically to expanding gate valves with 
relatively movable gate and segment assemblies having oppositely inclined 
interacting cam surfaces that cause expansion thereof for tight sealing 
with internal sealing surfaces with the gate valve and permit contraction 
thereof to permit opening and closing movement of the gate and segment 
assemblies by a linearly movable valve stem. Even more specifically, the 
present invention concerns a compact expanding gate valve mechanism having 
a gate and segment assembly incorporating control arms which are connected 
to the gate and segment actuating pins for achieving desired positioning 
of the gate and segment at various positions during opening and closing 
movement of the valve mechanism. 
2. Description of the Prior Art 
Expanding gate valves have been in wide use for many years and achieve 
efficient sealing particularly at both the open and closed positions of 
the valve mechanism. Typically, within a valve body structure a gate 
member is movable by a linearly movable valve stem between an open 
position, where flow of fluid through inlet and outlet passages is 
permitted, and a closed position where the gate member blocks the flow of 
fluid through the inlet and outlet passages. The gate member may define a 
flow port which is in registry with the flow passages in the open position 
of the gate and segment assembly. In compact gate valves, the gate member 
is often non-ported and is moved by the actuating stem of the valve to an 
open position where it is retracted to a position within the bonnet 
structure of the valve body and substantially clear of the flow passages. 
Efficient sealing of the gate and segment assembly with respect to internal 
seat rings or seat surfaces located within the valve body about the flow 
passages is caused by one or more segment members which cooperate with the 
gate member to define a gate and segment assembly and which is 
positionable relative to the gate member to permit contraction of the gate 
and segment assembly to thus permit its movement between the open and 
closed positions of the valve mechanism. This expansion and contraction of 
the gate and segment assembly is caused by interacting wedge or cam 
surfaces of the gate member and the segment member is caused by 
interacting cam or wedge surfaces of the gate and segment members which 
typically occurs as the gate member is driven linearly by the valve stem 
while the segment member is restrained by suitable internal stop structure 
of the valve body. 
A problem that typically occurs when expanding gate valves are employed is 
the tendency of the gate and segment assembly to remain in its condition 
of expansion even when force is being applied by the valve stem to achieve 
its contraction and movement. To minimize the tendency of the gate and 
segment assembly to remain so expanded, springs are often used to provide 
an urging force for collapsing or contracting the gate and segment 
assembly in absence of the presence of cam induced forces that overcome 
the spring force and expand the gate and segment assembly or structure 
that prevents collapse of the gate and segment assembly and maintains it 
positioned at its open or closed positions. 
Another problem that often occurs is the tendency of conventional gate and 
segment assemblies to undergo a condition known as "back-wedging" wherein 
the gate and segment assembly will be expanded particularly during its 
movement toward the closed position responsive to pressure induced force. 
As the gate and segment assembly are moved typically downwardly toward the 
closed position, as the flow path through the valve becomes restricted the 
velocity of the flowing fluid will increase. This increased velocity flow 
will act on the segment member, forcing it tightly against the downstream 
seat and thus increasing its drag or frictional resistance to movement. 
When this condition is developed the gate member is physically moved by 
the valve stem while the segment tends to become static at an intermediate 
position. This condition results in relative movement of the gate and 
segment members, thus causing expansion of the gate and segment assembly 
during its travel between the open and closed positions. 
Resistance to opening and closing movement of the gate and segment assembly 
can also result from increased pressure within the valve chamber as 
compared to pressure within the flowway of the valve. This higher body 
pressure can develop as the result of temperature changes, such as when 
fluid trapped within the valve body externally of the seat rings can 
expand as the result of increased heat and cause body pressure of 
increase. This increased body pressure can act on the gate and segment 
assembly and enhance its frictional engagement with the valve seats to the 
point that opening movement of the gate and segment assembly requires 
excessive valve stem force. It is desirable therefore to ensure that the 
gate and segment assembly does not become expanded by back-wedging during 
its movement between the open and closed positions. It is also desirable 
that the gate and segment assembly become collapsed immediately as its 
movement toward the open or closed position is initiated and remain 
collapsed during the entirety of its travel between the open and closed 
positions. 
SUMMARY OF THE INVENTION 
It is a principal feature of the present invention to provide a novel 
expanding gate valve mechanism having a gate and segment assembly 
incorporating a mechanism for ensuring movement of the gate and segment 
assembly thereof to its collapsed condition to enable stem actuated 
movement of the gate and segment assembly thereof from the closed position 
to the open position; 
It is another feature of the present invention to provide a novel expanding 
gate valve mechanism having a gate and segment assembly which is 
physically maintained at the collapsed condition thereof during the 
entirety of its movement between the open and closed positions, to ensure 
that a condition of back-wedging will not occur; 
It is an even further feature of the present invention to provide a novel 
expanding gate valve mechanism having a gate and segment assembly and 
incorporating a pair of control arms interacting with control pins, 
projecting from the gate and segment members, which mechanically actuate 
the gate and segment assembly from the expanded condition thereof to the 
collapsed condition to thereby permit its stem actuated opening movement 
within the valve body;

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
Referring now to the drawings and first to FIGS. 1 and 2, a compact 
expanding gate valve embodying the principles of the present invention is 
shown generally at 10 and is provided with a valve body shown generally at 
12 and defining conduit sections 14 and 16 which form flow passages 18 and 
20 through which fluid is permitted to flow when the valve mechanism is at 
its open position as shown in FIG. 2. The conduit sections 14 and 16 each 
define connection flanges 22 and 24 respectively which permit bolted 
connection of the valve body to a pipeline, not shown, having flanged pipe 
sections. It should be borne in mind that the valve body may be provided 
with any other suitable type of pipe connection system, such as weld 
connections, clamped connections, or the like, without departing from the 
spirit and scope of the present invention. 
The valve body 12 defines a bonnet section 26 having bonnet wall members 28 
and 30 that are disposed in spaced relation and defined in internal bonnet 
chamber 32. Typically the valve body will be of welded construction and 
formed of plate material though it may be constructed in any other 
suitable manner within the spirit and scope of the present invention. For 
example, the bonnet section may be cast or otherwise formed and may be of 
circular or oval cross-sectional configuration, if desired. When composed 
of plate material, the bonnet wall members 28 and 30 will be composed of 
flat plate stock and side-wall members, one being shown at 34 will be 
welded or otherwise connected to the bonnet walls 28 and 30. A bonnet 
closure 36 will be connected to the bonnet walls 28 and 30 and to the 
side-wall members 34 in any suitable manner. Typically, to permit repair 
or replacement of the gate and segment assembly or the seat rings, the 
bonnet closure 36 will be removably connected in sealed assembly with the 
bonnet walls by bolting or by any other suitable means of connection. 
The bonnet closure member 36 defines a centrally located typically circular 
valve stem opening 38 through which a valve stem 40 extends. The lower 
portion of the valve stem 40 defines a cylindrical sealing surface 42 
which is engaged by a packing 44 which is contained within a packing gland 
46 that is defined, at least partially, within the bonnet closure member 
36. To permit the packing or packing assembly to be installed within the 
packing gland and for periodic replacement of the packing, typically a 
portion of the packing chamber 46 is defined by a packing retainer element 
48 that is secured to the bonnet closure structure 36 by means of bolts 50 
or by any other suitable means. 
The upper portion of 52 of the valve stem 40 is typically an externally 
threaded section which is engaged by the internally threaded section of a 
valve actuator drive nut, not shown. As the drive nut is rotated by the 
rotary valve actuator for opening and closing movement of the valve 
mechanism, its threaded interaction with the threaded section 52 of the 
valve stem 40 will impart linear movement to the valve stem from the open 
position thereof shown in FIG. 1 to the closed position shown in FIG. 2. 
It should also be borne in mind that the valve stem 40 may be actuated 
between its open and closed positions by means of a linear actuator such 
as a hydraulic or pneumatic cylinder actuator if desired. 
The upper portion of the valve body is defined by a yoke tube shown 
generally at 54 which has a lower connection flange 56 having a plurality 
of holes through which project bolts or stud and nut assemblies 58 which 
mount the yoke tube securely to the upper surface of the bonnet closure 
36. Typically the connection flange, at its interface with the bonnet 
closure 36, will be provided with a suitable sealing system which, for 
purposes of simplicity, is not shown. A yoke tube member 60 extends 
upwardly from the connection flange 56 of the yoke tube structure and 
defines an internal chamber 62 which is substantially closed and defines a 
protective chamber for the valve stem 52. At the upper portion of the yoke 
tube element 60 is provided an actuator mounting flange 64 which may be 
welded or otherwise connected to the yoke tube 60. The mounting flange 64 
provides support for a valve actuator 66 which may be a rotary actuator 
imparting driving rotation to a drive nut having threaded engagement with 
the upper threaded section 52 of the valve stem 40. Alternatively, as 
indicated above, the valve actuator 66 may conveniently take the form of a 
linear actuator such as a hydraulic or pneumatic cylinder motor for 
accomplishing linear movement of the valve stem for opening and closing 
movement of the valve mechanism. Typically, for protection of the upper 
threaded extremity 52 of the valve stem the valve actuator 66 will be 
provided with a stem protector which typically is a tubular element within 
which the upper end of the valve stem is movably received. This stem 
protector simply prevents the upper threaded section of the valve stem 
from being contaminated or fouled by dirt, dust, water and other debris. 
The valve body is defined internally to form a pair of circular seat 
recesses 68 and 70 within which are located circular seat elements or seat 
assemblies 72 and 74. Typically, the circular seat elements 72 and 74 will 
be provided with face sealing elements 76 and 78 which enhance sealing of 
the seat rings with respect to a gate and segment assembly shown generally 
at 80. The gate and segment assembly incorporates a gate member 82 having 
its upper end 84 connected to the lower end 86 of the valve stem 40 so 
that the gate member is moved directly by the valve stem as the valve stem 
is linearly cycled during opening and closing movement of the valve 
mechanism. The gate member 82 defines a planar sealing surface 86 which is 
disposed for sealing engagement with the circular sealing face and the 
face seal 76 of the circular seat ring 72 when the gate member is at its 
closed position as shown in FIG. 1. The gate member 82 also defines an 
inclined cam surface 88 which faces toward a segment member 90 which is 
also disposed for reciprocating movement within the valve body along with 
the gate member 82. The segment member 90 likewise incorporates a planar 
sealing surface 92 which is disposed for sealing engagement with the 
circular seat 74 of the valve mechanism. The segment 90 further defines a 
corresponding inclined cam surface 94 which is disposed in face-to-face 
engagement with the inclined cam surface 88 of the gate member 82. 
Interaction of cam surfaces 88 and 94 as the gate member 82 is moved 
linearly relative to the segment member, causes the segment member to also 
be moved laterally, thus expanding the gate and segment assembly and 
developing tight sealing engagement of the respective sealing surfaces 86 
and 92 of the gate and segment with the circular sealing face surfaces of 
the respective seat rings 72 and 74. To cause relative movement of the 
gate member 82 with respect to the segment member 90, when the gate member 
reaches its closed position, an intermediate stop member 96 of the valve 
body is formed to define a stop surface 98. The stop surface 98 is 
positioned for engagement by the lower end surface 100 of the segment 90 
as the gate and segment assembly are moved downwardly to the closed 
position within the valve body. This feature permits the gate and segment 
assembly to remain collapsed during its movement to the closed position so 
that its movement can be accomplished without requiring valve stem force 
beyond the operating limits of the valve actuator mechanism. The 
intermediate valve body member 96 also defines a recess 102 which permits 
the lower end 104 of the gate member 82 to move further downwardly after 
the segment member 90 has been moved into engagement with the internal 
stop surface 98. As the gate member is moved downwardly relative to the 
segment member, after the segment has engaged the stop surface, the 
inclined flat cam surfaces 88 and 94 are caused to interact to impart 
lateral movement to the segment member, thereby expanding the gate and 
segment assembly and mechanically forcing the planar sealing surfaces 86 
and 92 of the gate and segment into tight sealing relation with the 
respective seat rings 72 and 74. 
When the valve mechanism is in its closed condition as shown in FIG. 1 with 
the planar sealing surfaces of the gate and segment in tight sealing 
engagement with the seat rings, opening movement of the valve mechanism is 
accomplished by moving the valve stem member 40 upwardly by means of the 
valve actuator 66 to thereby impart upward movement to the gate member 82. 
When this occurs the segment member is permitted to move laterally toward 
the gate member by virtue of relative movement of the inclined cam 
surfaces 88 and 94. If however the fluid being controlled by the valve 
mechanism is under considerable pressure, this pressure will act across 
the segment member by virtue of its sealing engagement with the seat ring 
and can cause the planar sealing surface 92 of the segment member to be 
frictionally restrained by the downstream seat ring 74. This frictional 
resistance to gate and segment movement can be greater than the valve stem 
is designed to bear. In this circumstance, the connection of the valve 
stem with the gate member can yield, thereby permitting the valve stem to 
separate from the gate member. Under this circumstance, it will be 
necessary to shut down the pipeline and repair or replace the valve. To 
accomplish repair of the valve while it is located within the pipeline, it 
will typically be necessary that the bonnet closure member 36 be 
removable, i.e. connected by bolts or other suitable means to the valve 
body, so that the gate and segment members can be removed from the valve 
body and replaced. It is therefore desirable to provide means for 
mechanically moving the segment member toward its collapsed position 
relative to the gate member as opening movement of the gate and segment 
assembly is initiated. Ordinarily springs are provided for this purpose, 
but it has been found quite clear that the available spring force is 
usually not sufficiently great to overcome the friction of the gate and 
segment assembly with the seat rings. It is thus desirable to provide a 
mechanism for physically accomplishing collapse of the gate and segment 
assembly to thus permit its opening or closing movement without 
necessitating application of excessive valve stem force. 
To accomplish this feature, as shown in greater detail in FIGS. 3 and 4, 
the valve body is provided with internal guide structure which may 
conveniently take the form of guide pins 106 and 108 which project from 
each side of the valve body and which are substantially oriented in 
aligned relation with an imaginary plane 110 which also intersects the 
center-line of the valve stem 40. If desired the internal guide structure 
may take the form of elongate internal guide elements which may be fixed 
to the wall structure of the valve body or may be formed as an integral 
part of the valve body structure For example, as shown in FIG. 5, a guide 
structure shown generally at 105 defines a connection plate section 107 
which is secured to the valve body by bolts 109 or by any other suitable 
means to maintain the guide structure in fixed relation with the valve 
body. From the connection plate projects a rib-like guide element 111 
which is received within the guide slot of a respective control arm of the 
valve mechanism, which is discussed in detail hereinbelow, and which 
serves to guide the control arms during transition of the gate and segment 
assembly between its open and closed positions. The length of the rib-like 
guide element 111 may be substantially the same as the dimension of the 
oppositely facing outside surfaces of the guide pins 106 and 108. The gate 
member 82 is provided with segment actuator pins 112 that project 
laterally from each of its sides. Likewise, the segment member 90 is 
provided with a pair of segment actuator pins 114 that project laterally 
from each side thereof. At least one and preferably a pair of control 
elements or arms 116 are provided which are located at opposite sides of 
the gate and segment assembly for movement therewith as the gate and 
segment assembly are moved between the open and closed positions thereof 
The control arms 116 may be of any suitable configuration establishing 
guided engagement with the guide elements 106 and 108 or other internal 
guide structure of the valve body. The control arms are connected in 
engagement with the gate member and segment member by respective segment 
actuating pins 112 and 114 of the gate member 82 and the segment member 
90. The control arms each define arm sections 118 and 120 that are 
disposed in spaced relation and defined an elongate guide slot 122. The 
guide slot 122 is provided to receive the aligned guide pins 106 and 108 
as shown in FIGS. 1-4, the rib-like guide structure 111 of FIG. 5 or any 
other suitable internal guide structure of the valve body, to control 
orientation of the control arms as the gate and segment assembly traverses 
its movement from the closed position shown in FIG. 1 to the open position 
shown in FIG. 2. Although the control arms are shown to define a guide 
slot extending substantially the length thereof, it should be borne in 
mind that guiding geometry other than slots may be employed to establish a 
guiding relationship between the control arms and the valve body without 
departing from the spirit and scope of the present invention. The arm 
sections 118 and 120 of the control arms 116 each define pin receiving 
openings 124 and 126 that are of slightly oval configuration so as to 
permit lateral movement of the control arms relative to each of the 
segment actuating pins 112 and 114 to thus permit slight rotational 
movement or canting of the control arms responsive to final closing or 
initial opening of the gate and segment assembly. This arrangement also 
permits the degree of lateral movement of the segment relative to the gate 
member which occurs during expansion and contraction movement of the gate 
and segment assembly. At the upper portion of the segment actuating arms, 
the guide or control slot of each of the control arms is provided with an 
enlargement 128 which permits slight rotation or canting of the control 
arms about the segment pivot 114 to the inclined or canted control arm 
position shown in FIG. 3. The slot enlargement 128 is of a configuration 
to permit control arm pivoting by the segment actuating pins 112 of the 
gate member with pivotal movement occurring about the segment actuating 
pins 114 which occurs as the result of movement of the gate member 
relative to the segment member after the lower end of the segment member 
has moved into contact with the stop surface 98 of the stop member of the 
valve body. 
The opposite control arm activity occurs as the gate member 82 is moved 
openly by the valve stem 40 in the manner described above. As the gate 
member is moved upwardly, the inclined cam surface 88 of the gate member 
will move away from the inclined cam surface 94 of the segment member 90. 
As mentioned above, pressure differential acting across the segment member 
may develop sufficient frictional resistance with the seat ring 74 that it 
will tend to remain firmly seated against the seat ring. This frictional 
resistance may be sufficiently great so as to prevent movement of the 
segment member to its collapsed position relative to the gate member, so 
that the gate and segment assembly will remain expanded and in tight 
engagement with each of the seat rings 72 and 74. In this condition, when 
a conventional expanding gate mechanism is employed, the segment can be 
prevented from being moved along with the gate member so that the result 
is damage to or excessive wear of the valve actuator or cause the 
connection of the valve stem with the gate member to yield. When this 
condition occurs, the valve stem can separate from the gate member and the 
valve mechanism will be rendered inoperative. Even when a conventional 
expanding gate mechanism is movable under these conditions, moving the 
gate and segment assembly with the planar sealing surfaces 86 and 92 of 
the gate and segment in tight frictional engagement with the respective 
sealing faces of the seat rings 72 and 74 can cause significant erosion or 
galling of the sealing surfaces of the gate and or segment members to 
damage the valve and require replacement or repair of the gate and segment 
assembly. 
It is important to note that the control arms are actuatable during initial 
opening or closing movement to a collapsed condition and maintain the gate 
and segment assembly collapsed at all conditions of pressure. During 
movement of the gate and segment assembly between the open and closed 
positions the control arms maintain the gate and segment assembly 
collapsed and thus eliminate development of a condition of back-wedging. 
In order to forcibly actuate the gate and segment assembly to cause 
sufficient collapse thereof to permit linear movement thereof from the 
open position shown in FIGS. 1 and 3 to the closed position shown in FIGS. 
2 and 4 a gate and segment control mechanism is provided for mechanically 
collapsing the gate and segment assembly responsive to opening actuation 
of the valve mechanism. As the gate member 82 is moved upwardly by the 
valve stem 40 from the position shown in FIGS. 1 and 3, the segment 
actuating pin 112 will also move upwardly and will act against a surface 
of the oval pin opening 124 thereby imparting upward force to the control 
arm section 118 causing it to be pivoted about the segment actuating pin 
114 of the segment. The segment actuating control arms will both be 
pivoted in like manner causing clockwise rotation of the control arm from 
the position shown in FIG. 3 about the segment actuating pin 114 to the 
position shown in FIG. 4, at which position the elongate guide slot 122 of 
the respective gate and segment control arm will become aligned with the 
respective guide pins 106 and 108 of the valve body. During rotation of 
the control arms by the actuating pins 112 of the gate member 82, the gate 
member will be caused to move linearly relative to the gate member and the 
control arms will apply collapsing force to the segment member to minimize 
its lateral dimension and permit linear movement of the gate and segment 
assembly to the open position shown in FIG. 4. After this rotational 
movement of the control arms has occurred, the control arms 116 will each 
be in the position shown in FIG. 4, with the elongate guide slot 122 being 
aligned with the fixed guide pins 106 and 108 of the valve body. As the 
gate and segment assembly is retracted into the bonnet chamber 32 the 
control arms 116 will be moved upwardly along with the gate and segment 
assembly, causing the fixed guide pins of the valve body to traverse the 
length of the elongate slots 122 thereof as is evident from FIG. 4. During 
such movement the gate and segment assembly the segment will be prevented 
from movement relative to the gate member and the gate and segment 
assembly will consequently be prevented from expansion until the end of 
its linear travel has been reached. 
Closing movement of the gate and segment assembly is generally the opposite 
of the opening movement discussed above. The valve actuator will move the 
valve stem 40 downwardly and the valve stem will in turn move the gate 
member downwardly. The control arms 116 will be moved downwardly along 
with the gate member 82 by virtue of its connection therewith by the 
segment actuating pin 112. As the gate and the control arms are driven 
downwardly the segment member 90 will also be driven downwardly along with 
the gate member by virtue of its connection with the control arms 116 by 
the segment actuating pin 114. During downward movement of the gate and 
segment assembly and the control arms 116, the fixed guide pins 106 and 
108 of the valve body will traverse the length of the elongate guide slot 
122 and will maintain the control arms at the straight position shown 
particularly in FIG. 4, causing the gate and segment assembly to remain 
collapsed during its transit between the open and closed positions 
thereof. Thus, the control arms prevent the development of back-wedging 
because the segment is prevented from stopping and thus causing relative 
movement with the gate member as the gate is moved by the valve actuator. 
At the upper ends of each of the control arms 116 the elongate guide slot 
122 defines enlargements 128 which permit limited pivotal movement or 
canting of the control arms only when the gate and segment assembly has 
reached its closed position. At all other positions of the gate and 
segment assembly within the valve body, the control arms maintain the gate 
and segment assembly in its collapsed condition so that a condition of 
back-wedging will not occur. The guide slot enlargements 128 are formed by 
cutting away a side section of the elongate slot at the upper end of the 
slot. The guide slot enlargements 128 are of sufficient length to receive 
both of the guide pins 106 and 108 to thus permit limited pivoting or 
rotation of the control arms by the actuating pins 112 and 114 when linear 
movement of the segment is stopped and the gate member is permitted to 
move linearly relative to the segment and cause expansion of the gate and 
segment assembly. As this limited pivotal movement or canting of the 
control arms occurs, the guide pins will be disposed in registry with the 
upper guide slot enlargements 128 of each of the control arms and in 
registry with the elongate guide slots 122 of each of the control arms. As 
downward or closing movement of the gate and segment assembly continues, 
the lower end surface 100 of the segment will contact the stop surface 98, 
thus preventing further downward movement thereof. The gate member however 
will continue to move downwardly since the lower end 104 of the gate will 
enter the recess that is provided to receive it. This relative linear 
movement of the gate member 82 relative to the segment member 90 causes 
interaction of the cam surfaces 88 of the gate member and 94 of the 
segment member, resulting in expansion of the gate and segment assembly. 
This expansion movement causes the planar sealing surfaces 86 and 92 of 
the gate and segment members respectively to be forced laterally into 
tight sealing engagement with the sealing faces of the seat rings 72 and 
74. As the gate member moves linearly relative to the segment member, the 
segment actuating pins 112 are moved downwardly while the segment and the 
segment control pins 114 are maintained static by the stop surface 98. 
This relative movement of the segment actuating pins 113 and 114 causes 
the control arms 116 to be pivoted counter clockwise about the segment 
actuating pins 114 as shown in FIG. 3, so that the elongate guide slot of 
each of the control arms is disposed in angulated relation with the guide 
pins 106 and 108 of the valve body. This pivotal movement of the control 
arms, which is permitted to occur only during expansion of the gate and 
segment assembly at the closed position thereof, causes the fixed guide 
pins of the valve body to be disposed within the offset enlargements of 
the guide slots as shown in FIG. 3. 
It is important to note that, movement of the gate and segment assembly 
from the closed and expanded condition shown in FIG. 3 can only occur if 
the gate and segment assembly becomes collapsed. As upward movement of the 
gate is initiated the actuating pin 112 will be moved upwardly while the 
segment actuating pin 114 will tend to remain static due to frictional 
retention of the segment member against the valve seat 74. Upward movement 
of the actuating pin 112 by the gate member causes pivoting movement of 
the control arm about the actuating pin 114 and thus causes the elongate 
guide slot to be moved into alignment with the guide pins 106 and 108. 
Such movement of the control arm also causes the segment to be moved 
toward the gate member, causing the gate and segment assembly to become 
collapsed and readied for movement to the open position. 
The control arms 116 may be formed from flat sheet metal stock if desired 
or may be composed of a polymer material that is suitable for the intended 
valve service. Although guide pins 106 and 108 are shown to be employed 
for guiding the control arms 116 during linear movement thereof, it should 
be borne in mind that any suitable guide structure, such as that shown in 
FIG. 5, for example, may be provided within the valve body for guiding the 
control arms. For example, elongate guide projections in the form of 
internal bosses may project inwardly from opposite sides of the valve body 
and may be received within the elongate guide slot 122 of each of the 
control arms. Alternatively, the valve body may be machined to define 
internal guide slots of appropriate configuration and the control arms may 
be provided with guide projections that traverse the elongate guide slots 
and permit pivotal control arm movement such as is described above. 
In view of the foregoing it is evident that the present invention is one 
well adapted to attain all of the objects and features hereinabove set 
forth, together with other objects and features which are inherent in the 
apparatus disclosed herein. 
As will be readily apparent to those skilled in the art, the present 
invention may easily be produced in other specific forms without departing 
from its spirit or essential characteristics. The present embodiment is, 
therefore, to be considered as merely illustrative and not restrictive, 
the scope of the invention being indicated by the claims rather than the 
foregoing description, and all changes which come within the meaning and 
range of equivalence of the claims are therefore intended to be embraced 
therein.