Abstract:
A coaxial valve includes a valve box having at least one inlet opening, at least one outlet opening, and a common flow channel. A cylindrical valve casing, which is prevented from turning at one segment of the flow channel, but is intended to be axially movable, features an opening for a fluid inlet port as well as an opening for a fluid outlet port, both of which are joined up in the flow channel. A shutoff mechanism is located inside the valve box, is positioned coaxially to the valve casing, and is designed to close off the inlet port or the outlet port of the valve casing. To provide for axial movement, the valve casing, at least in sections at its outermost surface, has at least one external circular groove. The valve casing, at the segment of the external circular groove, is enclosed by a drive casing which is coaxial to the valve casing. At its internal diameter, the drive casing has at least one inner circular groove, which is adapted to the outer circular groove so that the inner and outer grooves are engaged, via inside ball bearings, to create a ball planetary gear and ball rotary spindle drive. The drive casing in the valve box is turnable, but firmly seated axially, and forced to turn by a drive motor inside of the valve box.

Description:
[0001]     This application claims the priority of German application 10 2005 028 584.8, filed Jun. 21, 2005, the disclosure of which is expressly incorporated by reference herein.  
       BACKGROUND AND SUMMARY OF THE INVENTION  
       [0002]     This invention pertains to a coaxial valve including a valve box, having at least one fluid inlet opening, at least one fluid outlet opening, and a common flow channel connecting the fluid inlet and fluid outlet openings together. A tubular shaped valve casing, which is prevented from turning but permitted to be axially pivotable, features a fluid inlet port and an outlet port, which join inside the common flow channel. A shutoff mechanism, located inside of the valve box, is coaxial to the valve casing and designed to shut off the fluid inlet port or the outlet port of the valve casing, and a drive is provided to produce axial movement of the valve casing. The valve may be used with cryogenic fluids.  
         [0003]     Special requirements must be met with valves that serve for the regulating and sealing off of a liquid or gaseous medium under extreme conditions, such as chemical aggressiveness, very high or very low temperatures, or very high pressure. Fields of application for valves that serve to seal off a fluid or gaseous medium are found in power trains in air and space travel. These valves are exposed to extreme temperatures and extreme temperature changes. For valves used for fluid and gaseous rocket fuels, there are additional parameters which increase certain demands on this type of valve, such as demands relating to mass flow, high pressure, and short switching time for opening and closing of the valve or for getting the valve into a special position.  
         [0004]     A valve with these specifications is known from German document DE 199 60 330 C2. The valve shaft of this valve is moved axially in relation to the valve closing mechanism within the flow by a lever which is activated by an electric servo motor from the outside of the valve body.  
         [0005]     Since this servo motor is mounted externally, this valve has relatively large mounting dimensions. In addition, operation using a lever mechanism is complicated and therefore presents increased risks for malfunctioning to an extent which is unacceptable in applications in space aviation.  
         [0006]     It is one object of this invention to design a valve with these specifications which is extremely reliable in its operation because of its compact construction, low friction, low energy requirements, and light weight.  
         [0007]     This object is achieved by way of a valve in which the valve casing is provided, at least in sections, with at least one threaded external nut at an outer circular groove, in which the valve casing is enclosed by a coaxial drive casing at a location of the outer circular groove, in which the drive casing is provided with at least one threaded inner circular groove adapted to the outer circular groove so that ball bearings running along the inner and outer circular grooves create tension against one another, thus forming a ball planetary gear of a ball rotary spindle drive, and in which the drive casing is located inside of the valve box, is pivotable but firmly seated axially, and is made to pivot by a drive motor inside of the valve box.  
         [0008]     The valve shaft is therefore equipped, section by section, on its outer surface with at least one external adjusting nut with threads and surrounded in each section of this external adjusting nut by a drive sleeve which is coaxial to the valve shaft. The drive sleeve is equipped on its interior with at least one threaded internal adjusting nut, which fits against the outer adjusting nut in such a way that the inner and outer threads match and thus perform the ball screw-driven propulsion of a linear integrated ball screw drive. The drive shaft can turn within the valve casing but is axially secured and rotated by a driving motor installed on the inside of the valve shaft. The driving motor and the driving shaft actuate the drive for the valve shaft by taking into consideration the section of the threaded outer nut and the bearings which are integrated into the valve shaft.  
         [0009]     The valve shaft is thus identical with the spindle of the screw-driven propulsion. The advantage of the construction described is the compact structure of this coaxial valve which is achieved by the integration of the valve shaft with the screw driven propulsion, and the resulting light weight.  
         [0010]     Further advantages of this invention will also be apparent.  
         [0011]     It is especially of advantage when the drive casing is surrounded by the rotor of the drive shaft and is connected to prevent any rotation. Configuring the motor coaxially with the valve shaft provides for a particularly compact construction of the coaxial valve. It is advantageous that the rotor is surrounded by a stator from the driving motor and that the stator is prevented from turning within the valve casing.  
         [0012]     It is also beneficial when the stator&#39;s position allows for at least a certain amount of axial shifting because this design will compensate for thermal expansion of the various elements of the drive.  
         [0013]     In another advantageous design the rotor can turn inside the stator by means of at least two radial roller bearings. The provision of this roller bearing ensures that the space between the rotor and the stator remains constant during operation, especially under temperature fluctuations.  
         [0014]     An electrically driven driving motor presents an advantage. It is also conceivable that, for example, a hydraulic driving motor could be used.  
         [0015]     In another advantageous embodiment, the drive shaft is positioned above two axial roller bearings. This placement promotes the attachment of the drive shaft within the valve casing and thus ensures a definite axial positioning of the ball screw driven propulsion.  
         [0016]     Optimally, the two axial roller bearings are each provided with a circular, domed convex outer surface within their respective outer bearing rings. These convex outer surfaces are supported in turn by a corresponding concave inner surface on the interior of the valve casing where the respective spherical and concave and convex surfaces share the same central point on the axis of the valve casing. With this design, the entire drive system, including the ball screw propulsion, is at least to some degree pivotable in all directions around the central point, so that tensions caused in the drive, especially by temperature fluctuations, are counter-balanced in the casing and/or in the drive. As a result, a secure valve seal is guaranteed, and an abrasion-free operation of the valve shaft is enabled even in the presence of tension within the valve casing and/or in the drive.  
         [0017]     These features are improved, in an enhanced modification of the invention, by providing the closing mechanism with a first part which has a domed concave surface pointing toward the valve shaft, and by having a domed convex surface of a second part which can be pivoted in such a way that these two parts are connected in an axial direction, but can move relative to each other along the domed surfaces, while the central point of the domed surfaces of the closing mechanism is aligned with the central point of the two domed axial roller bearings. In this way, the second part of the closing mechanism with a tight seal is positioned in a way that allows for pivoting around the same central point, thereby further improving the reliability of the seal even where there is tension within the valve casing and/or in the drive.  
         [0018]     In a preferred embodiment, the closing mechanism is equipped on the second part with a valve seat which, together with the front-sided rim around the valve port of the neighboring end of the valve shaft, effects an even better seal when the valve is closed.  
         [0019]     The invention will now be described by way of an example shown in the drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES  
       [0020]      FIG. 1  shows a cross-section of a coaxial valve according to the invention;  
         [0021]      FIG. 2  is an enlarged view of a detail A of  FIG. 1 ; and  
         [0022]      FIG. 3  is a enlarged view of a detail B of  FIG. 1 .  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]      FIG. 1  shows a cross-section of a coaxial valve. In the valve box  1 , a flow channel  10  with a fluid inlet opening  12  and a fluid outlet opening  14  is provided. The fluid inlet opening  12  and the fluid outlet opening  14  on opposite ends of the valve box  1  are constructed in such a way that the flow channel  10  from the fluid inlet opening  12  is level with the fluid outlet opening  14 . In the cross-sectional view, flow channel  10 , the fluid inlet opening  12  and the fluid outlet opening  14  are arranged in a circular fashion and coaxially to each other, whereby they share a common center line X. In the area of the fluid inlet opening  12 , the flow channel  10  is formed by a first cylindrical bore section  16 . The first cylindrical bore section  16  is provided with a first frontal lid section  11  of valve box  1 . The fluid outlet opening  14  is provided with a second frontal lid section  13  on the side opposing the first frontal lid section of the valve casing. A cylindrical mid section  15  is situated between the first frontal lid section  11  and the second frontal lid section  13  of the valve box  1 . Both lid sections  11 , 13  are screwed together with the cylindrical mid section, as illustrated in  FIG. 1 .  
         [0024]     The second frontal lid section  13  shows a cylindrical casing connection  17  protruding forward in the direction of the center line X which has been provided with a fluid outlet opening  14 . On the inside of the cylindrical casing connection  17 , a basically cylindrical second bore section  18  of the flow channel  10  is built, whereby this bore section possesses a diameter which is greater than that of the first cylindrical bore section  16 . Between the first cylindrical bore section  16  and the second basically cylindrical bore section  18  of the flow channel  10 , a cylindrical internal space  19  is located in the area of the mid section  15  of the valve box  1 , the diameter of which is considerably larger than the diameter in the second basically cylindrical bore section  18 .  
         [0025]     In the flow channel  10  there is a tubular valve casing  2  coaxial to flow channel  10  between the first cylindrical bore section  16  and the second basically cylindrical bore section  18 . The valve casing  2  is made circular in cross-section and free to travel along its axis, which is identical with the center line X. The valve casing  2  is constructed as a straight tube and surrounds an inner channel  20 , which is provided with a front-sided inlet port  22  next to inlet opening  12  and a front-sided outlet port  24 , which faces toward fluid outlet opening  14 . Thus the inner channel  20  provides a central section of flow channel  10  between the first cylindrical bore section  16  and the second basically cylindrical bore section  18 .  
         [0026]     On the internal space  19 , a drive  3  is provided. The drive acts on the valve casing  2  to move toward the center line X and will be further described hereafter.  
         [0027]     The drive  3  surrounds a drive motor  30 , which is arranged inside the internal space  19 , is constructed as an electric motor, and surrounds valve casing  2 , and a ball planetary gear  4  which couples the drive of the motor  30  and the valve casing  2 . The motor  30  and the ball planetary gear  4  are also arranged coaxially around the valve casing  2 , so that the rotation axis of the motor  30  and the ball planetary gear  4  align with the center line X under normal circumstances when no deformation of the valve casing  2 , caused by mechanical tension, has taken place.  
         [0028]     The motor  30  is constructed as an internal rotor motor and has an external radial stator  32  as well as an internal radial rotor  34 . The stator  32  is prevented from turning by means of at least one radial outward protruding nib  31  on a radially inward turned rib  15 ′ of the cylindrical mid section  15 , but can be axially displaced. This possibility for axial displacement facilitates a minimal relative movement in axial direction between the valve box  1  and the drive  3 , thus avoiding tensions within drive  3  and in the valve box  1  on account of varying thermal expansion of drive  3  and valve box  1 . For the same reason a nib  31 ′ is allowed in addition between the radial outer edge of the nib  31  and the inner wall of the cylindrical mid section  15  which also facilitates a radial relative movement between the drive  3  and the valve box  1 .  
         [0029]     The stator  32  of the drive motor  30  is equipped with an electrical winding familiar to those skilled in the art. The rotor  34  inside the stator  32  is equipped with permanent magnets familiar to those skilled in the art around the outer surface. The rotor  34  is pivotable without friction by means of two radial ball bearings  33 ,  35  inside stator  32 . This positioning of rotor  34  inside stator  32  by means of ball bearings  33 ,  35  ensures that a constant radial distance is maintained between rotor  34  and stator  32 , even when extreme thermal influences have an effect on drive  3 .  
         [0030]     A cylindrical drive shaft  40  which is part of the ball planetary gear  4  has been provided inside the rotor  34 . The shaft is also prevented from turning and is axially tightly connected with rotor  34 . The drive shaft  40  is also arranged in coaxial order with the valve casing  2 , and the middle axis of the drive shaft  40  is identical with the center line X of the valve casing  2 .  
         [0031]     The drive shaft  40  is provided with at least one threaded inner circular groove  42 . The drive shaft  40  surrounds a central radial, outwardly tapering section  25  of the valve casing  2 . This middle section  25  of the valve casing  2  forms an inner drive element  44 , which is integrated with the valve casing  2  and which exhibits a threaded outer circular groove  46  on its exterior circumference which extends in axial direction across almost the entire length of the middle section  25  which is longer in axial direction than the section of the drive shaft  40 , which is connected with the inner circular groove  42 .  
         [0032]     Between the radial outer circumference of the drive element  44  which has been constructed by the section  25  of the valve casing  2  and the inner circumference of the drive shaft there is only a very small space, so that the inner circular groove  42  and the outer circular groove  46  shown in the covering of the ball bearing channel  47  in  FIG. 1  form a basically circular cross-section, which contains numerous balls  48 . In this way, the inner drive element  44 , the balls  48 , and the drive casing  40  will form the ball planetary gear  4 . The drive  3  and the ball planetary gear  4  will create a ball rotary spindle drive  5  for the valve casing  2 , which is integrated into the ball rotary spindle drive.  
         [0033]     The valve casing  2  is constructed within the area of its flow inlet port  22  which has been inserted in the first frontal lid section  11  and has been sealed off with a slide ring gasket sealing washer  6 . In the same way the valve casing  2  is constructed in the area of its opposite flow outlet port  24  and has been sealed off with a second slide ring gasket sealing washer  7  axially, whereby the second slide ring gasket sealing washer  7  is inserted in the second frontal lid section  13 .  
         [0034]     The first slide ring gasket sealing washer  6  consists of a first ring-shaped insert element  60 , which surrounds the valve casing  2  and is equipped with a circular seal  62  with a sealing lip  64  fitted to the outer surface of the valve casing  2  and seals it. Axially inward from the sealing lip  64 , turned away from the inlet port  22 , that is, in the first insert element  60 , there is a slide ring  66 , which surrounds the outside of the valve casing  2  and turns this with minimal friction.  
         [0035]     In an analogous fashion the second slide ring gasket sealing washer  7  shows a second insert element  70 , which is tied to the second frontal lid section  13 . The second insert element  70  is equipped with a ring-shaped seal  72  which has a radially inward turned sealing lip  74  and surrounds and seals the outer circumference. In the second insert element  70 , axially inward from the sealing lip  74 , turned away from the flow outlet port  24 , there is an slide ring  76 , which surrounds the valve casing  2  and turns it with absolutely minimal friction.  
         [0036]     The ball rotary spindle drive  5 , consisting of the drive motor  3  and the ball planetary gear  4  including the valve casing  2 , is situated inside the valve box  1  and can be turned a little in all directions around the ball central point M, so that this ball central point M is positioned on the center line X, as outlined below. This positioning is achieved by means of two ball bearings  52 ,  56  coaxial to the center line X which have corresponding axial inner bearing ring  53 ,  57  and which have been installed on opposite front sides of the rotor  34 . The corresponding bearing rings  54 , 58  of the axial ball bearings  52 ,  56  are supported by the first frontal lid section  11  and/or the second frontal lid section  13  in a way that will be described later on. In addition, there is a support ring  55  in place coaxially to the center line X and similarly on the second frontal lid section, a support ring  59  is located coaxially to the center line X.  
         [0037]     The positioning of the ball rotary spindle drive  5  inside the valve box  1 , shown in detail A in  FIG. 1 , will now be described by means of  FIG. 2 . The description is given by reference to the upper axial ball bearing  56  in  FIG. 1 , while the support of the lower axial ball bearing  52  is achieved in the first frontal lid section  11  in the same way.  
         [0038]     The support ring  59  is affixed to the second insert element  70 , which is connected with the frontal lid section  13  in a manner familiar to those versed in the art. On its axially and radially inward side, the support ring  59  is equipped with a supporting spherical, concave inner surface  59 ′ which has a corresponding ring-shaped, spherical, convex outer surface  58 ′ which is found on the axial and radial outer area of the axial outer support ring  58  of the axial ball bearing  56 . In the same way, the axially outer bearing ring  54  of the axial ball bearing  52  is equipped with a ring-shaped, spherical, convex outer surface  54 , as is the support ring  55 , which is affixed to the first insert element  60  of the first frontal lid section  11  with a spherical, concave inner surface  55 ′, as shown in  FIG. 3 .  
         [0039]     The convex surfaces  54 ′ and  58 ′ are ring-shaped segments of spheres in a virtual sphere with a central point M on the center line X. Even the concave surfaces  55 ′ and  59 ′ are ring-shaped spherical segments of a virtual sphere with the same central point M. In this manner the entire rotary spindle drive  5  can rotate a little around the center point M with relative movement between inner and outer surfaces  54 ″ and  55 ″, as well as surfaces  58 ″ and  59 ″.  
         [0040]     Furthermore,  FIG. 3  shows that the valve casing  2  in the area of the first frontal cover section  11  is fitted with a pivot  26  projecting radially outwards, and a ball bearing  27  is connected to the pivot. Both the pivot  26  and the ball bearing  27  then catch a longitudinal slot  11 ″ of the first frontal lid section  11  that runs parallel to the center line X, and the ball bearing  27 , including its outer ring  27 ″, will roll off a side wall of the longitudinal slot  11 ″. In an analogous manner, on the valve casing  2  on the opposite side there is a pivot  28  projecting radially outwards. As shown in  FIG. 1 , a ball bearing  29  is connected to the pivot and will be steered in the same manner through a longitudinal slot  11 ″ designated for this side of the first frontal lid section  11 . Both these sideways guiding methods in the valve casing  2  will prevent the valve casing  2  from rotating relative to the valve box  1 , and will assure that the valve casing  2 —with the exception of a minimal swiveling action around the ball central point M—can only move in the direction of the center line X. Using ball bearings  27  and  29  as guide rollers will minimize any friction in the respective axial guide ways.  
         [0041]     The second frontal lid section provides for a shutoff mechanism  8  inside the cylindrical casing connection  17 , i.e. in the second mainly cylindrical bore section  18  of the flow channel  10 . To open and close the valve, this shutoff mechanism will work in conjunction with the outlet port  24  of the valve casing  2 . The shutoff mechanism  8  includes a ring-shaped base section  80  positioned coaxially to the center line X in the area of the fluid outlet opening  14  in the second frontal lid section  13 . Connected to the ring-shaped base section  80  is a cylindrical tubular pedestal section  81  which is also positioned coaxially to the center line X. It forms the first part  82  of the shutoff mechanism  8  and extends into the mainly cylindrical bore connection  18  in the direction of the axial flow.  
         [0042]     The cylindrical pedestal section  81  is provided in its perimeter wall with a majority of openings  89 , which produce a fluid connection between the mainly cylindrical bore section  18  of the flow channel  10  and the fluid outlet opening  14 .  
         [0043]     The axial front wall  83  of the cylindrical pedestal section  81  pointing inwards into the valve box  1  is designed as a concave wall and is provided with a concave front surface  83 ″, which is designed dome-shaped and constitutes a spherical segment of a virtual sphere with the central point M. An adapted convex outer surface  84 ″ of a support element  84  for a valve unit  86  rests in the concave front surface  83 ″. The support element  84  and the valve unit  86  together form a second part  85  of the shutoff mechanism  8 . Also the support element  84  and the valve unit  86  are ordered co-axially to the central line X, whereby the convex outer surface  84 ″ of the support element  84  likewise forms a dome-shaped spherical segment of a virtual ball with the central point M.  
         [0044]     The valve unit  86  is ordered to the side of the support element  84  turned away from the convex outer surface  84 ″ and points to the outlet port  24  of the valve casing  2 . The valve unit  86  is designed conically, whereby in the area of its greatest perimeter it is provided with a circular step  86 ″ forming a valve seat, which in sealing works together with the valve seat formed from the perimeter edge of the outlet port  24  of the valve casing  2  near the closed valve.  
         [0045]     By means of a screw  87  centrally penetrating the concave front wall  83 , which is braced against the front wall via a support element  88  provided on the back side of the concave front wall  83  of the cylindrical pedestal section  81 , the valve unit  86  and the support element  84 , and the first part  82  are braced against the second part  85  of the shutoff mechanism  8 . The support element  88  is thereby provided with a concave front surface  88 ″ pointing to the front wall  83 , which forms a spherical sector of a virtual sphere with the central point M. The convex back surface  83 ″ of the front wall  83 , which is pointing towards the fluid outlet opening  14 , is also part of a spherical surface with the central point M.  
         [0046]     This shutoff mechanism  8  design, with its spherical surfaces showing the same central point M as the spherical surfaces of the ball rotary spindle drive  5  bearing inside the valve box, also allows the valve unit  86  to pivot a little around the center line M. Therefore, no significant uneven load will occur on the circular step  86 ″ of the valve unit  86  which controls the valve location of the sealing element  8 . That means, even in cases where there is a slight pivoting of the ball rotary spindle drive  5  and the valve unit  86 , a dependable seal regarding the valve in the area of the valve unit  86  and the outlet port  24  is guaranteed. Furthermore, this way any external constraining forces will be kept away from the ball rotary spindle drive  5 .  
         [0047]     Any reference item numbers listed in any claims, descriptions, and drawings are solely provided to better understand the invention. They are in no way intended to limit the scope of protection.  
         [0048]     The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.  
         [0000]     The following is a list of Reference Items  
       REFERENCE ITEM NO  
       [0000]    
       
           1  Valve Box  
           2  Valve Casing  
           3  Drive  
           4  Ball Planetary Gear  
           5  Ball Rotary Spindle Drive  
           6  First Slide Ring Gasket Sealing Washer  
           7  Second Slide Ring Gasket Sealing Washer  
           8  Shutoff Mechanism  
           10  Flow Channel  
           11  First Frontal Lid Section  
           11 ′ Longitudinal Slot  
           11 ″ Longitudinal Slot  
           12  Fluid Inlet Opening  
           13  Second Frontal Lid Section  
           14  Fluid Outlet Opening  
           15  Cylindrical Mid Section  
           15 ′ Rib  
           16  First Cylindrical Bore Section  
           17  Cylindrical Casing Connection  
           18  Second Bore Section, Mainly Cylindrical  
           19  Internal Space  
           20  Inner Channel  
           22  Inlet Port  
           24  Outlet Port  
           25  Middle Section of 2  
           26  Pivot  
           27  Ball Bearing  
           27 ′ Outer Ring  
           28  Pivot  
           29  Ball Bearing  
           30  Drive Motor  
           31  Nib  
           31 ′ Gap  
           32  Stator  
           33  Radial Ball Bearing  
           34  Rotor  
           35  Radial Ball Bearing  
           40  Drive Casing  
           42  Inner Circular Groove  
           44  Inner Drive Element  
           46  Outer Circular Groove  
           47  Ball Bearing Channel  
           48  Balls  
           52  Axial Ball Bearing  
           53  Axial Inner Support Ring  
           54  Axial Outer Support Ring  
           54 ′ Convex Outer Surface  
           55  Support Ring  
           55 ′ Concave Inner Surface  
           56  Axial Ball Bearing  
           57  Axial Inner Support Ring  
           58  Axial Outer Support Ring  
           58 ′ Convex Outer Surface  
           59  Support Ring  
           59 ′ Concave Inner Surface  
           60  First Insert Element  
           62  Circular Seal  
           64  Sealing Lip  
           66  Slide Ring  
           70  Second Insert Element  
           72  Ring-shaped Seal  
           74  Sealing Lip  
           76  Slide Ring  
           80  Ring-shaped Base Section  
           81  Cylindrical Tubular Pedestal Section  
           82  First Part of 8  
           83  Front Wall  
           83 ′ Concave Front Surface  
           83 ″ Convex Back Surface  
           84  Support Element  
           84 ′ Convex Outer Surface  
           85  Second Part of  8   
           86  Valve Unit  
           86 ′ Circular Step  
           87  Screw  
           88  Support Element  
           88 ′ Concave Front Surface  
           89  Openings  
          X Center Line  
          M Ball Central Point