Steam control valve

Abstract

Steam control valve, comprising: a housing (1); a valve seat (2) formed within the housing (1); a valve plate (3) which can be placed against the valve seat (2); a valve lift rod (4A, 4B) connected to the valve disc (3), extending in the vertical direction and penetrating the housing (1); a bushing (5A, 5B) provided in the housing (1) and slidably supporting the valve lift rod (4A, 4B); a lever (6A, 6B) connected to an upper end of the valve lift rod (4A, 4B); and an actuating member (7) which causes the lever (6A, 6B) to pivot, characterized in that a box section (22A, 22B) with a downward opening is provided on one end side of the lever (6A, 6B), and the box portion (22A, 22B) of the lever (6A, 6B) is loosely fitted with an overhang portion (23A, 23B) on one side of the valve lift rod (4A, 4B), and the overall size of an interior space of the box portion (22A, 22B), ie the size of the interior space in a vertical direction and a horizontal direction, is larger than the overhang portion (23A, 23B) by an amount corresponding to a predetermined value, taking into account positional displacements of the bushing (5A, 5B) due to thermal expansion of the housing (1).

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The present invention relates to a steam control valve. 2. Description of the state of the art

[0002] Steam turbines include a steam control valve for adjusting the steam supply flow rate depending on the load. A steam control valve according to JP 2016-160973 A includes: a plurality of valve seats formed within a casing; a plurality of valve discs engageable with the plurality of valve seats, respectively; a pair of valve lift rods connected to the plurality of valve discs, extending in a vertical direction, and penetrating the casing; a pair of cylindrical bushings provided in the casing and slidably supporting the pair of valve lift rods, respectively; a pair of levers connected to the upper ends of the pair of valve lift rods, respectively; and an actuator (particularly a hydraulic cylinder or a servomotor) that causes the pair of levers to pivot.

[0003] The upper end of one valve lift rod of the pair of valve lift rods is connected to one end of one lever of the pair of levers by a pin. The upper end of the other valve lift rod is connected to one end of the other lever by a pin. The actuator is connected to the other end of one lever and the other end of the other lever and causes the levers to pivot upward or downward. This causes the plurality of valve discs to pivot upward or downward via the pair of valve lift rods and the like. In this way, the opening degrees of the plurality of valve seats are adjusted and the steam supply flow rate is adjusted.

[0004] Further prior art can be found in document DE 23 26 303 A, which describes a steam turbine control valve.

[0005] Due to the thermal expansion of the body of a steam control valve caused by steam, the positions of the bushings change slightly. According to the above-mentioned conventional technology, the degree of freedom in the arrangement of the valve lift rods is limited because the valve lift rods and the levers are connected by pins. Accordingly, there is a possibility that the valve lift rods may be eccentric or oblique to the bushings, which promotes wear of the valve lift rods. SUMMARY OF THE INVENTION

[0006] An object of the present invention is to provide a steam control valve which can increase the degree of freedom of arrangement of the valve lift rods and reduce the wear of the valve lift rods.

[0007] The present invention is defined by the steam control valve according to claim 1. The dependent claims describe optional features and preferred embodiments.

[0008] In order to achieve the above-described object, a steam control valve according to the present invention comprises: a valve seat; a valve disc abuttable against the valve seat; a valve lift rod connected to the valve disc and extending in a vertical direction; a bushing slidably supporting the valve lift rod; a lever connected to an upper end of the valve lift rod; and an actuator for causing the lever to swing, on which a box portion having a downward opening is provided on one end side of the lever, and the box portion of the lever is loosely fitted with an overhang portion on one side of the valve lift rod.

[0009] According to the present invention, it is possible to increase the degree of freedom of arrangement of the valve lift rod and to reduce the wear of the valve lift rod. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view showing the structure of a steam control valve in a first embodiment of the present invention. Fig. 2 is a cross-sectional view along a section II-II in Fig. 1. Fig. 3 is a partially enlarged cross-sectional view taken at a section III in Fig. 2 was recorded. Fig. 4 is a cross-sectional view along a cross section IV-IV in Fig. 1. Fig. 5 is a cross-sectional view showing a structure for connecting a connecting member to a lever in the first embodiment of the present invention. Fig. 6 is a cross-sectional view showing a structure for coupling a connecting member to a lever in a second embodiment of the present invention. Fig. 7 is a cross-sectional view illustrating a structure for connecting a connecting member to a lever in a third embodiment of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] A first embodiment of the present invention will be explained with reference to the figures.

[0011] Fig. 1 is a perspective view showing the structure of a steam control valve in the present embodiment, and some portions thereof are omitted from the figure for simplicity. Fig. 2 is a cross-sectional view taken along a cross section II-II in Fig. 1 was recorded, and Fig. 3 is a partially enlarged cross-sectional view taken in a section III in Fig. 2 was recorded. Fig. 4 is a cross-sectional view along a cross section IV-IV in Fig. 1. Fig. 5 is a cross-sectional view illustrating a structure for connecting a connecting member to a lever in the present embodiment.

[0012] The steam control valve according to the present embodiment includes: a plurality of valve seats 2 (four valve seats 2 in the present embodiment) formed within a housing 1; a plurality of valve discs 3 (four valve discs 3 in the present embodiment), each of which is engageable with a corresponding one of the plurality of valve seats 2; a pair of valve lift rods 4A and 4B connected to the plurality of valve discs 3, extending in the vertical direction, and penetrating the housing 1; a pair of cylindrical bushings 5A and 5B provided in the housing 1 and slidably supporting the pair of valve lift rods 4A and 4B, respectively; a pair of levers 6A and 6B, each connected to the upper ends of the pair of valve lift rods 4A and 4B; and an actuator 7 (specifically, a hydraulic cylinder or a servo motor) that causes the pair of levers 6A and 6B to pivot.

[0013] A steam chamber (valve chamber) 8 is formed within the casing 1, and a steam inlet port 9 is formed at a side portion of the casing 1 and communicates with the steam chamber 8. High-temperature and high-pressure steam can be introduced into the steam chamber 8 through the steam inlet port 9. A plurality of steam supply ports 10 are formed at a lower portion of the casing 1 and communicate with the steam chamber 8. Each of the plurality of valve seats 2 is formed at an opening edge portion of a corresponding one of the plurality of steam supply ports 10. The plurality of valve discs 3, which make the opening degrees of the plurality of valve seats 2 variable, make it possible to adjust the supply rate of steam supplied from the steam chamber 8 to a casing (not shown) of the steam turbine.

[0014] A valve lift plate 11 is arranged in the steam chamber 8 of the housing 1. A plurality of through holes 12 are formed through the valve lift plate 11, and each of a plurality of valve rods 13 is inserted into a corresponding one of the plurality of through holes 12. A valve disc 3 is provided on the lower side of each valve rod 13, and double nuts 14 are screwed onto a screw portion on the upper side of each valve rod 13. By adjusting the position of the double nuts 14 relative to each valve rod 13, it is possible to adjust the lower end position of the downward movement of each valve disc 3 relative to the valve lift plate 11 and to adjust the opening and closing timing of each valve seat 2. By setting the opening and closing timing of the plurality of valve seats 2 differently, it is possible to gradually vary the opening degree of the plurality of valve seats 2 as a whole.

[0015] The lower ends of the valve lift rods 4A and 4B are connected to the valve lift plate 11. The upper ends of the valve lift rods 4A and 4B are connected to each other via a coupling member 15. Specifically, outer screw portions at the upper ends of the valve lift rods 4A and 4B are screwed into inner screw portions at both ends of the coupling member 15.

[0016] A guide rod 16 is arranged upright on the top of the housing 1 and is inserted into a through hole in the center of the coupling member 15. A spring retaining member 17 is provided at the upper end of the guide rod 16, and a spring 18 is provided between the spring retaining member 17 and the coupling member 15. The spring 18 can drive the plurality of valve discs 3 downward via the coupling member 15, the valve lift rods 4A and 4B, and the valve lift plate 11.

[0017] The upper end of the valve lift rod 4A is connected to the lower end of a connecting member 19A via the coupling member 15, and the upper end of the valve lift rod 4B is connected to the lower end of a connecting member 19B via the coupling member 15. Specifically, the lower end of the connecting member 19A and the coupling member 15 are connected to each other by a pin, and the lower end of the connecting member 19B and the coupling member 15 are connected to each other by a pin.

[0018] One end of the lever 6A is connected to the upper end of the link 19A, and one end of the lever 6B is connected to the upper end of the link 19B. The other ends of the levers 6A and 6B are rotatably supported by brackets 20A and 20B of the housing 1, respectively. Furthermore, the other ends of the levers 6A and 6B are connected to the actuator 7 via links 21. When the actuator 7 causes the levers 6A and 6B to pivot up or down, the plurality of valve discs 3 move up or down via the links 19A and 19B, the coupling member 15, the valve lift rods 4A and 4B, and the valve lift plate 11. This allows the opening degrees of the plurality of valve seats 2 to vary.

[0019] An essential feature of the present embodiment is that a rectangular parallelepiped box portion 22A having a downward opening is provided on one end side of the lever 6A, a rectangular parallelepiped overhang portion 23A is provided on the upper end side of the link member 19A, and the box portion 22A of the lever 6A is loosely fitted with the overhang portion 23A of the link member 19A. In other words, the link member 19A and the like are suspended from the box portion 22A of the lever 6A. The overall size of the internal space of the box portion 22A of the lever 6A (i.e., the size of the internal space in a vertical direction and a horizontal direction) is larger than the overhang portion 23A of the link member 19A by an amount corresponding to a predetermined value (e.g.,about a few millimeters), taking into account positional displacements of the bushing 5A due to thermal expansion of the housing 1. Furthermore, the opening of the box portion 22A of the lever 6A is larger than the cross-section of the body of the connecting element 19A by an amount corresponding to the aforementioned predetermined value, and additionally smaller than the cross-section of the overhang portion 23A of the connecting element 19A by an amount corresponding to the aforementioned predetermined value. It should be noted that in the present embodiment, the inner surface of the box portion 22A of the lever 6A movably supports the overhang portion 23A of the connecting element 19A.

[0020] Similarly, a rectangular parallelepiped box portion 22B with a downward opening is provided on one end side of the lever 6B, a rectangular parallelepiped overhang portion 23B is provided on the upper end side of the link member 19B, and the box portion 22B of the lever 6B is loosely fitted with the overhang portion 23B of the link member 19B. In other words, the link member 19B and the like are suspended from the box portion 22B of the lever 6B. The overall size of the internal space of the box portion 22B of the lever 6B (i.e., the size of the internal space in a vertical direction and a horizontal direction) is larger than the overhang portion 23B of the link member 19B by an amount corresponding to a predetermined value (e.g., about a few millimeters), taking into account positional displacements of the bushing 5B due to thermal expansion of the housing 1.Furthermore, the opening of the box portion 22B of the lever 6B is larger than the cross-sectional area of the body of the link member 19B by an amount corresponding to the aforementioned predetermined value, and additionally smaller than the cross-sectional area of the overhang portion 23B of the link member 19B by an amount corresponding to the aforementioned predetermined value. Note that in the present embodiment, the inner surface of the box portion 22B of the lever 6B movably supports the overhang portion 23B of the link member 19B.

[0021] In the present embodiment thus configured, the degree of freedom of arrangement of the valve lift rods 4A and 4B can be increased compared to a case where one end of the lever 6A and the upper end of the link 19A are connected to each other by a pin, and in addition, one end of the lever 6B and the upper end of the link 19B are coupled to each other by a pin. Therefore, the positions of the valve lift rods 4A and 4B can be maintained even if the positions of the bushings 5A and 5B change slightly due to thermal expansion of the housing 1. Accordingly, it is possible to prevent the valve lift rods 4A and 4B from being eccentric or oblique to the bushings 5A and 5B, and to reduce wear of the valve lift rods 4A and 4B.

[0022] A second embodiment of the present invention will be explained. Note that parts in the present embodiment that are equivalent to their counterparts in the first embodiment are given identical reference numerals, and explanations thereof are omitted where appropriate.

[0023] Fig. 6 is a cross-sectional view showing a structure for connecting a connecting member to a lever in the present embodiment.

[0024] The steam control valve according to the present embodiment includes a plurality of steel balls 24 housed in the box portion 22A of the lever 6A and movably supporting the overhang portion 23A of the link member 19A, and a plurality of steel balls 24 housed in the box portion 22B of the lever 6B and movably supporting the overhang portion 23B of the link member 19B.

[0025] In the present embodiment thus configured, it is also possible, similar to the first embodiment, to increase the degree of freedom of arrangement of the valve lift rods 4A and 4B and reduce the wear of the valve lift rods 4A and 4B. Furthermore, in the present embodiment, due to the plurality of steel balls 24, it is possible to reduce the frictional forces generated between the box portions of the levers and the overhang portions of the link members.

[0026] A third embodiment of the present invention will be explained. Note that parts in the present embodiment that are equivalent to their counterparts in the first embodiment are given identical reference numerals, and explanations thereof are omitted where appropriate.

[0027] Fig.7 is a cross-sectional view showing a structure for connecting a connecting member to a lever in the present embodiment.

[0028] The steam control valve according to the present embodiment includes a sliding plate 25 housed in the box portion 22A of the lever 6A and movably supporting the overhang portion 23A of the link member 19A, and a sliding plate 25 housed in the box portion 22B of the lever 6B and movably supporting the projection portion 23B of the link member 19B. The sliding plates 25 are formed such that their friction coefficient is lower than the friction coefficients of the housing portions 22A and 22B of the levers by using a preferred material therefor or subjecting them to a preferred surface treatment.

[0029] In the present embodiment thus configured, it is also possible, similar to the first embodiment, to increase the degree of freedom of arrangement of the valve lift rods 4A and 4B and reduce the wear of the valve lift rods 4A and 4B. Furthermore, in the present embodiment, due to the sliding plates 25, it is possible to reduce the frictional forces generated between the box portions of the levers and the overhang portions of the link members.

[0030] It should be noted that although the box portions 22A and 22B of the levers and the overhang portions 23A and 23B of the connecting members are rectangular parallelepiped in the examples explained in the first to third embodiments, these are not the only examples and they may also be cubic or spherical, for example.

[0031] While the coupling member 15 and the connecting member 19A are arranged between the valve lift rod 4A and the lever 6A, the coupling member 15 and the connecting member 19B are arranged between the valve lift rod 4B and the lever 6B, and the overhang portions 23A and 23B are provided on the connecting members 19A and 19B in the examples explained in the first to third embodiments, these are not the only examples. That is, for example, the coupling member and the connecting members may not be arranged between the valve lift rods and the levers, and the overhang portions may be provided on the valve lift rods. DESCRIPTION OF REFERENCE SYMBOLS 2 valve seat 3 valve plates 4A, 4B valve lift rod 5A, 5B socket 6A, 6B lever 7 Actuator 19A, 19B connecting element 22A, 22B box section 23A, 23B overhang section 24 steel balls 25 sliding plate

Claims

[1] Steam control valve, comprising: a housing (1); a valve seat (2) formed within the housing (1); a valve plate (3) which can be placed against the valve seat (2); a valve lift rod (4A, 4B) connected to the valve plate (3), extending in the vertical direction and penetrating the housing (1); a bushing (5A, 5B) provided in the housing (1) and slidably supporting the valve lift rod (4A, 4B); a lever (6A, 6B) connected to an upper end of the valve lift rod (4A, 4B); and an actuating member (7) which causes the lever (6A, 6B) to pivot, characterized by , that a box section (22A, 22B) with a downwardly directed opening is provided on one end side of the lever (6A, 6B), and the box portion (22A, 22B) of the lever (6A, 6B) is loosely fitted with an overhang portion (23A, 23B) on one side of the valve lift rod (4A, 4B), and the overall size of an interior space of the box portion (22A, 22B), ie the size of the interior space in a vertical direction and a horizontal direction, is larger than the overhang portion (23A, 23B) by an amount corresponding to a predetermined value, taking into account positional displacements of the bushing (5A, 5B) due to thermal expansion of the housing (1). [2] Steam control valve according to claim 1, wherein the lever (6A, 6B) is connected to an upper end of the valve lift rod (4A, 4B) via a connecting member (19A, 19B), and the overhang portion (23A, 23B) is provided on the connecting member (19A, 19B). [3] Steam control valve according to claim 1, comprising a plurality of steel balls (24) housed in the box portion (22A, 22B) of the lever (6A, 6B) and movably supporting the overhang portion (23A, 23B). [4] Steam control valve according to claim 1, comprising a sliding plate (25) which is housed in the box portion (22A, 23B) of the lever (6A, 6B) and movably supports the overhang portion (23A, 23B).

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