Abstract:
Actuator for operating a valve, including: a drive component; a drive shaft, which is connectable with the valve; and a torque lock, which is connectable with the drive shaft The torque lock includes at least one essentially rotationally symmetric spring element arranged in a ring-shaped housing, and is so constructed that a torque introduced via the drive component causes the drive shaft to rotate, and a torque introduced via the valve blocks rotation of the drive shaft.

Description:
FIELD OF THE INVENTION 
     The invention relates to an actuator for operating a valve, including: A drive component; a drive shaft, which is connectable with the valve; and a torque lock, which is connectable with the drive shaft. 
     BACKGROUND OF THE INVENTION 
     Torque locks are already known in the state of the art. Torque locks permit an unhindered rotational driving of a machine part—for example manually—in both directions of rotation, while reverse torques, i.e. those exerted by the driven part on the drive are blocked, as much as possible, in both senses of rotation, without an additional braking device being needed for such function. A torque lock, or load-torque lock, known from DE 85099971 U works according to the jamming rollers, or jamming wedge, principle. In such case, there is arranged within a closed, ring-shaped housing, a suitable cylindrical inner body, which is connected with the output part, thus the part to be driven, such that it cannot rotate relative thereto. The cylindrical inner body has on its periphery a recess, in which each jamming roller sits, pressed outwards by clamping springs. These prevent a rotation of the cylindrical inner body relative to the ring-shaped, outer housing. Arranged between the two jamming rolls is a strut-shaped driving part, which is e.g. a component of a hand wheel. If this driving part is rotated in one or the other direction, one of the two jamming rolls is released against the force of the pressing spring and the driven part can be adjusted. In such case, the second jamming roll then does not carry a load. Reverse torques from the driven part are, in contrast, blocked in both directions. 
     Rotary drives with torque locks using the jamming rollers principle are used, for example, for position securement on displacing drives for machine parts. Additionally, they serve e.g. for securing and manual adjustment of gate drives, for hatch and window securement, or for rebound protection in the case of control and shutoff butterfly valves. The disadvantage of the known torque locks based on the jamming rollers principle, or also the jamming wedge principle, is that these torque locks can exhibit a relatively critical blocking behavior. Additionally, a relatively high wear is experienced with them, since by the jamming, followed by releasing, of the jamming elements, the contacting parts are subjected to high frictional forces. Due to the wear or due to the slightest deformation of the materials, a continuing worsening of the blocking function can occur. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide an actuator in which reverse torques from the valve are not transmitted to the drive component. 
     The object is solved by providing that the torque lock used in the case of the actuator of the invention has at least one essentially rotationally symmetric spring element arranged in a ring-shaped housing, with the torque lock being so constructed that a torque introduced via the drive component sets the drive shaft in rotation and that a torque introduced via the valve blocks the rotation of the drive shaft. Preferably, the spring element is so embodied, that the torque lock works extremely reliable throughout different torque ranges. 
     In an advantageous further development of the device of the invention, it is provided that the rotationally symmetric spring element is a wrap spring. A special embodiment provides especially that at least one entraining element is provided on the drive component, while at least one blocking piece is arranged on the output drive shaft. Furthermore, the two end regions of the wrap spring are so embodied and arranged that, in the case of an introduction of the torque via the drive component, the at least one entraining element so interacts with the two end regions of the wrap spring that the torque lock is unlocked and the drive shaft turns; in the case of an introduction of torque via the valve, in contrast, the at least one blocking piece so interacts with at least one of the two end regions of the wrap spring that the torque lock blocks. Preferably, the spring wire of the wrap spring has a square cross section. However, the cross section of the spring wire of the wrap spring can also be round. The load, or torque, introduction into the wrap spring occurs preferably via bent spring ends. The bent spring ends are optimized with reference to strength such that the torque lock works with a high degree of process stability. 
     In principle, the drive component can be any kind of drive. By way of example, a direct drive can be mentioned, which, for the actuator of the invention, must be so constructed that it produces a high torque at small rotational speeds. Furthermore, the drive component can be an electric motor, or an electric motor with a reduction transmission coupled therewith. Additionally, the drive component can be a separately operable, adjustment wheel, or a separately operable adjustment wheel with a reduction transmission coupled thereto. Preferably, the separately operable adjustment wheel is a hand wheel. 
     A preferred form of embodiment of the actuator of the invention provides a second reduction transmission, which is arranged between the valve and the torque lock. Especially a worm transmission is installed as the second reduction transmission. Worm transmissions are usually constructed such that they exhibit an intrinsic self-locking. It is true that this does reduce overall efficiency; however, the intrinsic self-locking can effectively prevent an accidental and undesired rotation of the drive shaft. As a result of the self-locking, the drive shaft moves only after a defined torque, which balances the self-locking, is exceeded. This points out a decided advantage of the actuator of the invention: Since the actuator has a torque lock, the intrinsic self-locking of the reduction transmission can be omitted. This embodiment of the actuator of the invention therefore exhibits an increased overall efficiency, compared with the known solution. 
     Advantageously, the torque lock used in the case of the actuator of the invention is embodied as an integral part of the drive component. However, an alternative form of embodiment provides that the torque lock is an independent function module, which is so embodied and constructed that it can be coupled to the drive shaft. This embodiment permits the retrofitting of any actuator with the torque lock of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE INVENTION 
       The invention will now be explained in greater detail on the basis of the drawings, the figures of which show as follows: 
         FIG. 1   a : a schematic drawing of a first embodiment of the actuator of the invention; 
         FIG. 1   b : a schematic drawing of a second embodiment of the actuator of the invention; 
         FIG. 2 : a model-like, exploded drawing of a preferred form of embodiment of the torque lock of the invention; 
         FIG. 3 : a longitudinal section through a preferred embodiment of the torque lock of the invention; and 
         FIG. 3   a : a cross section taken according to the cutting plane A-A of  FIG. 3 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIGS. 1   a  and  1   b  are schematic representations of alternate forms of embodiment of the invention. In the case of the form of embodiment shown in  FIG. 1   a , the drive component  3  operates the valve  2  directly via the drive shaft  4 . Valve  2  is preferably an adjusting element  2 , e.g. a globe or gate valve, each with spindle and threaded bushing, a throttle valve or butterfly valve. Depending on the adjusting element  2 , the operating, or displacement process, which is introduced via the drive component  3 , is a rotary, or swinging or pivoting, movement. The drive component  3  is preferably a direct drive  11 . However, it is also possible to insert a first reduction transmission  20  after the electric motor. Of course, alternatively or additionally to the electric drive component  3 , also a separately operable adjustment wheel, e.g. a hand wheel, can be used for manual operation of the valve. The torque lock  5  is associated with the drive shaft  4 . 
       FIG. 1   b  shows a schematic representation of a second embodiment of the actuator  1  of the invention. The form of embodiment shown in  FIG. 1   b  differs from that shown in  FIG. 1   a  by a second reduction transmission  12 , which is arranged between the torque lock  5  and the valve  2  at the torque lock output drive shaft  4   b . The reduction transmission  12  is preferably a worm transmission. Worm transmissions usually exhibit an intrinsic self-locking, which should suppress unintended rotations of the drive shaft  4 . This embodiment of an actuator  1  is especially advantageous, since, due to the interposed torque lock  5 , this intrinsic self-locking of the worm transmission  12  can be omitted, whereby the overall efficiency of the actuator  1  can be improved. 
       FIG. 2  presents a model-like, exploded representation of a preferred form of embodiment of the torque lock  5  of the invention. Essential components of the torque lock of the invention are the wrap spring  7  and a drive shaft divided in two parts, with an entraining mechanism  8  on the drive input side and a blocking mechanism  9  on the drive output side. An entraining element  8  is attached to the torque lock input drive shaft  4   a ; the blocking piece  9  is attached to the torque lock output drive shaft  4   b . The entraining element  8  has the form of a portion of a hollow cylinder. The two end regions  21 ,  22  of the entraining element  8  lie against the insides of the spring ends  10   a ,  10   b  of the wrap spring  7 . 
     Wrap spring  7  is arranged in the blocking ring  6 . Preferably, the spring wire of the wrap spring  7  has a square cross section. However, the cross section of the spring wire of the wrap spring  7  can also be round. 
     Blocking piece  9  is, as already indicated, provided on the torque lock output drive shaft  4   b . Blocking piece  9  is composed of portions of cylindrical surfaces. The radial boundary surfaces form the end regions  23 ,  24  of the blocking piece  9 . The first end region  23 , or the second end region  24 , acts, in the case of a torque introduction coming from the direction of the valve  2 , respectively, on the bent spring end  10   a , or on the bent spring end  10   b . The bent spring ends  10   a ,  10   b  are, moreover, optimized with respect to strength in a manner such that the torque lock  5  functions process stably in high degree. 
     As soon as the torque lock input drive shaft  4   a  turns as a result of a torque introduction coming from the direction of the drive component  3 , the entraining element  8  drives, with the pertinent one of the end regions  21 ,  22 , the wrap spring  7  via the inner side of the pertinent spring end  10   a ,  10   b . This releases the wrap spring  7  from the blocking ring  6 , whereby a turning of the output drive shaft  4  is permitted. 
     If, in contrast, a reverse torque is introduced from the direction of the valve  2  via the torque lock output drive shaft  4   b , then, depending on the turning direction, either end region  23  or end region  24  of the blocking piece  9  presses on the outside of the pertinent spring end  10   a  or  10   b . This causes the wrap spring to be pressed with amplified force against the blocking ring  6 . As a result of this pressing, a rotation of the drive shaft  4  is effectively prevented. As soon, in turn, an introduction of a torque occurs from the direction of the drive component  3 , the wrap spring  7  is again released from the blocking ring  6 , and the blocking action of the torque lock  5  is canceled. 
       FIG. 3  shows a detailed drawing of a longitudinal section through a preferred embodiment of the torque lock  5  of the invention.  FIG. 3   a  provides a cross section according to the cutting plane A-A of  FIG. 3 . The torque lock  5  of the invention is arranged in a housing  13  with adapted flange  18 . The torque lock  5  is arranged on the drive shaft  4 . 
     Essential components of the torque lock  5  are the wrap spring  7 , which is positioned in the blocking ring  6 , the torque lock input drive shaft  4   a  with the entraining element  8 , and the torque lock output drive shaft  4   b  with the blocking piece  9 . Of course, the torque lock  5  could be designed such that the blocking ring  6  is part of the housing  13 . Spacers  19   a ,  19   b  serve to determine the axial position of the wrap spring  7 . 
     The torque lock  5  is mounted on the drive shaft  4  via bearings  15   a ,  15   b ,  15   c . In the illustrated case, the bearings  15   a ,  15   b  are ball bearings, while bearing  15   c  is embodied as a needle bearing. Moreover, the torque lock  5  is sealed relative to the drive shaft  4  via the seals  14   a ,  14   b ,  14   c , which are preferably O-rings. The part of the housing  13  facing the drive component  3  (not separately shown in  FIG. 3 ) is embodied as a flange in the illustrated case.