Linkage locking device

Abstract: Apparatus primarily for use in seating and unseating a valve by turning the valve stem (26) between a fully opened and fully closed position. In one form of the invention, a lever arm (25) attached to the valve stem (26) is connected at one corner of a triangular shaped crank arm (30) by a link (40). A second corner (37) of the crank arm (30) is rotatably mounted on a fixed shaft (35) and the third corner is connected to an actuator (15). The shaft (35), the link (40) and a pivot point on the distal end of the lever arm (25) and a corner of the triangular shaped crank arm (30) are all brought into alignment along a common axis when the valve is in a fully closed position. Moving the actuator in the opposite direction breaks the alignment between the link and the crank arm and pulls the lever arm toward a valve opening position.

Description: This invention refers to an apparatus for moving a device, preferably the stem of a valve, between a first and second position, according to the generic part of claim 1. United States Patent No. 5,542,643 to Breth discloses a ball valve that is seated and unseated by means of a hydraulic actuator. The piston rod of the actuator is coupled to the lever arm of the valve by a plate. The plate contains slotted holes that permit the plate to be adjustably positioned between the valve lever arm and the piston rod of the actuator. Sufficient adjustment is provided so that the valve can be accurately positioned by the actuator between a fully closed and a fully opened position. Collins, in United States Patent No. 5,078,180, which represents the closest prior art, further describes a hydraulically actuated gate valve. The actuator is again connected to the crank arm of the valve by means of plate-like linkage. The valve is opened and closed through the linkage as the piston rod of the hydraulic actuator is extended or retracted. Although the prior art device provides additional torque for seating and unseating a valve, they are incapable of holding the valve closed when the valve experiences high internal surge pressures. Most valve actuators can seat and unseat a valve under normal conditions. However, they cannot also function simultaneously to lock the valve in a closed position. Additionally, many of these prior art devices close at a relatively high speed causing undue wear and breakage of the valve components. United States Patent No. 4,959,989 describes a force multiplying press. Similar to the disclosure in US 5,078,180 a linear motion of an end part is generated, in this case a ram with a fabricating tool of a press. It is a primary object of the present invention to improve apparatus for providing extremely high torque to a lever arm, or the like, to move the arm between a first and a second position. A further object of the present invention is to improve apparatus for seating and unseating a valve. A still further object of the present invention is to provide apparatus for providing a high torque for moving a lever arm, or the like, between a first closed position and a second opened position and simultaneously providing an extremely high locking force automatically against the lever arm when it is brought into the closed position. Another object of the present invention is to provide a device that can open and close a valve and automatically lock the valve in the closed position with sufficient force to prevent the valve from inadvertently opening due to high internal surge pressures. Yet another object of the present invention is to provide a valve actuator mechanism that can unseat the valve under adverse conditions using a minimum amount of force. A still further object of the present invention is to provide a nearly zero valve crank arm speed when the valve reaches its closed position. Yet a further object of the present invention is to provide a valve control apparatus having a linkage that is capable of operating in any direction without changing its performance characteristics. These and other objects of the present invention are attained by the features of claim 1. Preferred embodiments of the invention are set out in the dependent claims. For a better understanding of these and other objects of the invention, reference will be made to the detailed description of the invention which is to be read in association with the following drawings, wherein: Fig. 1 is a side elevation of apparatus for operating a valve with the panels removed to better show the interior of the apparatus with the valve in an open position; Fig. 2 is also a side elevation similar to that illustrated in Fig. 1 showing the valve in a closed position; Fig. 3 is an enlarged elevation showing the linkage mechanism employed in the present invention with the valve being in an open position; and Fig. 4 is a side elevation similar to that illustrated in Fig. 3 showing the valve in a closed position; and Fig. 5 is a further enlarged side elevation showing another embodiment of the present invention. Description of the Invention Turning now to the drawings, the present invention will be described with specific reference to apparatus for seating and unseating a valve. However, as should become evident from the disclosure below, the apparatus has greater utility and can be used in various applications involving the movement of a lever arm or the like between first and second positions. The apparatus of the present invention is capable of delivering high torque as well as providing an automatic locking and unlocking feature that will hold a valve, for example, closed against high internal pressure particularly during surge, and break the lock tending to hold the valve closed under equally high pressures. Furthermore, the present apparatus is arranged to deliver a nearly zero closing speed to the crank arm of a valve thus reducing the closing forces on the valve parts. As illustrated in Figs. 1 and 2, the apparatus of the present invention is housed within a fixture generally referenced 10 which has some of its panels removed to better show the interior thereof. The fixture includes a lower compartment 12 and an upper frame 13 mounted over the compartment. A hydraulic actuator 15 is mounted in the upper frame which includes a cylinder 17 containing a piston rod 18 that is arranged to reciprocate along a vertical path of travel indicated by the arrows. A valve generally referenced 20 is mounted via a bolting flange 21 located in the rear wall 22 of the lower compartment. A lever arm 25 is secured to the valve stem 26 and is arranged to move between a fully opened position as viewed in Fig. 1 and a fully closed position as viewed in Fig. 2. The piston rod of the hydraulic actuator is connected to a triangular shaped crank arm generally referenced 30 by means of a link 31. The link contains a clevis 33 at each end that is threaded into the body of link so that the length of the link can be adjusted. The upper clevis is rotatably joined to the distal end of the hydraulic actuator's piston rod. The lower clevis is rotatably connected to the crank arm at one corner 34 thereof (Fig. 3 and 4). The crank arm is rotatably supported upon a stub shaft 35 mounted in the back wall of the fixture. The shaft is located at a second corner 37 of the crank arm. The center of the shaft 38 thus provides a fixed pivot point 38 (Fig. 4) about which the crank turns as the piston rod 18 of the hydraulic actuator is extended and retracted. The distal end of the valve lever arm 25 is rotatably connected to the third corner 39 of the crank arm by means of a second shorter link 40. Here a clevis 41 is threaded into the opposing ends of the link. The upper clevis is rotatably connected to the corner 39 of the crank arm by a suitable pivot and the lower clevis is similarly connected to the distal end of the lever arm. The operation of the present linkage will be explained with further reference to Figs. 3 and 4. The valve in this particular embodiment is arranged to be fully opened when the lever arm is in a twelve o'clock position as illustrated in Fig. 3. Moving the lever arm ninety degrees in a clockwise direction places the valve in a fully closed position. The geometry of the crank arm and the lengths of the links are set with regard to the stroke of the hydraulic actuator so that the lever arm moves through the required distance as the piston rod 31 is extended and retracted. As illustrated in Fig. 4, when the valve is brought to the fully closed position, the shaft 35, the pivot point 50 at corner 39 of the crank and the pivot point 51 at the distal end of the valve lever arm 25 are all brought into alignment along a common center line 53. The link 40 at this time is also axially aligned with the center line. Accordingly, any pressures or surges that are generated within the valve that might tend to open the valve act along the center line and are strongly resisted by the crank and link which at closure, combine to form a continuous rigid member extending between the shaft and the lever arm that is loaded in compression. To unseat the valve, the actuator is simply retracted which pulls the center 51 back from the centerline 53 to rapidly unlock the valve and break whatever forces that might tend to hold the valve closed. An adjustable stop 60 (Figs. 1 and 2) is mounted within the fixture that is arranged to interrupt the rearward motion of the lever arm once it is brought to the fully opened position. Turning now to Fig. 5, there is shown a second embodiment of the invention wherein the triangular shaped crank arm has been replaced by a pair of angular displaced bars 70 and 71. The proximal ends of the two bars are cojoined at a common hub 73 that is rotatably secured to the fixed shaft 35. Accordingly the two arms will move in unison as the hydraulic actuator is extended or retracted. The valve stem 26, as illustrated in Fig. 5, is again shown in a closed position. Here again, the linkage joining the lever arm to the actuator is arranged so that bar 71 and link 40 are brought into axial alignment along centerline 53 to provide maximum holding force against the valve stem capable of resisting internal forces that might otherwise tend to open the valve. The crank arm 30 and the link 40 are arranged so that point 50 is an instant center about which the two bodies rotate relative to each other. As illustrated in Fig. 4, the velocity of the crank arm 25 approaches zero when the link is aligned along centerline 53 that passes through the center of the shaft 35. By making this zero velocity point correspond to the closure position of the valve, the internal impact forces of the valve generated at closure are considerably reduced when compared to other valve actuators. It should be further noted that the present actuator is not restricted as to where it can be mounted with regard to a valve. The valve actuator performance characteristic will remain unchanged regardless of the actuator position provided the centers 35, 50 and 51 all come into alignment along a common centerline at closure. While this invention has been explained with reference to the structure disclosed herein, it is not confined to the details set forth and this invention is intended to cover any modifications and changes as may come within the scope of the following claims:

Claims: Apparatus (10) for moving a device, preferably the stem (26) of a valve (20), between a first position and a second position, the apparatus (10) including a mechanism with an actuator (15), having a member (18) reciprocating along a predetermined path of travel, with a crank arm fixture (30; 70, 71), defining three pivot points (33, 35, 50), located at the corners (34, 37, 39) of a triangle, the member (18) of the actuator (15) and a first corner (34) of the crank arm fixture (30; 70, 71) being rotatably connected, and with a rotatable connection (50, 51) between the crank arm fixture (30; 70, 71) and the device to be moved, characterized in that the apparatus is provided with a rotatable lever arm (25), which is securable with one end to the device, the lever arm (25) having a first position corresponding with the first position of the device, and a second position, corresponding with the second position of the device, that the crank arm fixture (30; 70, 71) has a fixed pivot point (35), located at a second corner (37) of the fixture (30; 70, 71), that the third corner (39) of the fixture (30; 70, 71) and the distal end of the lever arm (25) are rotatably connected by means of a link (40) with pivot points (50, 51), and that , when the lever arm (25) is brought to one of it's two positions, the fixed pivot point (35) of the fixture (30; 70, 71), the pivot point (50) at the third corner (39) of the fixture (30; 70, 71), the link (40) and the pivot point (51) at the distal end of the lever arm (25) all are lying upon a common center line (53). Apparatus according to claim 1, characterized in, that the crank arm fixture is a triangular shaped element (30). Apparatus according to claim 1, characterized in, that the crank arm fixture consists of angular displaced bars (70, 71), their proximal ends being conjoined at a common hub (73), that is rotatably secured to the fixed pivot point (35), and their distal ends forming pivot points (33, 50). Apparatus according to claims 1, 2 or 3, characterized in, that the reciprocating member (18) and the fixture (30; 70, 71) are rotatably connected by means of a second link (31) and pivot points (33). Apparatus according to any of the preceding claims, characterized in, that the actuator (15) and the fixed pivot point (35) are mounted within a frame. Apparatus according to any of the preceding claims, characterized in, that it includes stop means (60) for interrupting the motion of the lever arm (25), when it is moved to one of it's two positions. Apparatus according to any of the preceding claims, characterized in, that at least one of the links (31, 40) contains means for adjusting the axial length of the link (31, 40).

Inventors: WEIJIAN MA, WEIJIAN, MA
Applicants: YOUNG AND FRANKLIN
Application year: 1999
Main classification: F16K31
IPC codes: F16K31, F15B15