Abstract:
A torque booster for operating a valve during initial opening and closing movements of the valve. The torque booster includes a rotatable valve operating stem, a rotatable operator shaft, a gear reduction unit, and a coupling for temporarily operatively interposing the gear reduction unit between the shaft and the stem during initial rotation of the shaft in a valve-opening or a valve-closing direction, so that during the temporary period the stem rotates at a fraction of the speed of the shaft. After the temporary torque-boost period, the speed of rotation of the stem increases with respect to the speed of rotation of the shaft, preferably so that the speeds of rotation of the stem and shaft approach or equal a ratio of one-to-one.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to operation of valves, especially those used in difficult or corrosive locations or environments, such as marine valves. 
     Such valves usually require application of greater torque to initially open or initially close the valve than the further effort required to complete the opening or closing of the valve. Upon opening a fully closed valve, a relatively high torque is required to overcome the pressure differential across the valve, and to overcome the friction of the closed-valve parts. An increased torque is also required to initially move an open valve toward a closed position because a valve which has been open for some period of time often experiences a build-up of residues on the relatively movable parts of the valve which makes initial movement of those parts difficult. 
     In order to obtain a torque boost, it is usually necessary to slow the movement of the movable valve part with respect to the movement of the valve operator, which may be a hand wheel for valves which are manually operated. If there is a large reduction in speed of rotation of the movable valve part, so as to obtain an accompanying large input torque to the valve, the operator, such as the hand wheel, must be turned many times in order for the valve to be completely opened or completely closed. 
     Therefore, it would be advantageous to have an arrangement whereby a high torque can be initially applied to a valve during its initial opening or closing movement, followed by a lower ratio of speeds of the valve operator and valve parts, accompanied by a necessarily lower torque. In this way, high torque is available for overcoming the initial resistance of a valve to opening or closing, but a higher speed of opening or closing movement is available during the remainder of the opening or closing movement of the valve. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a torque booster for operating a valve which temporarily boosts the torque applied to a valve during initial opening and closing of the valve, but thereafter decreases the torque so that the speed ratio between the valve operator and the moving valve part is reduced, whereby the moving valve part more quickly responds to movement of the operator to complete opening or closing of the valve. 
     It is another object of the invention to provide such a torque booster including a gear reduction unit, and coupling means for temporarily operatively interposing the gear reduction unit between the valve operator and the valve during initial movement of the valve operator in a valve-opening or valve-closing direction, the coupling causing the gear reduction unit to be bypassed during further movement of the valve operator. 
     Additional objects and features of the invention are set forth in the following description, in which reference is made to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     In the drawings: 
     FIG. 1 is an environmental view showing the location of a torque booster, according to the present invention, in a typical valve operation installation; 
     FIG. 2 is a side elevational view of a torque booster according to the present invention; 
     FIG. 3 is a schematic, exploded view of a torque booster according to the present invention; 
     FIG. 4 is a transverse cross-sectional view of the torque booster along line  4 — 4  of FIG. 3; 
     FIG. 5 is an axial cross-sectional view of the coupling of the torque booster, with the parts in one relative position; 
     FIG. 6 is a view similar to FIG. 5 showing the parts of the coupling in a different relative position; 
     FIG. 7 is a side elevational view of the piston of the coupling; 
     FIG. 8 is a view similar to FIG. 7 showing the piston rotator about its axis by 90°; and 
     FIGS. 9 a - 9   d  are schematic views showing relative movement of the coupling and the crown gears for temporarily operatively interposing the gear reduction unit between the valve operator and the valve. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 schematically illustrates a torque booster  10  according to the present invention, within an installation for operating a marine valve. However, it is understood that use of the torque booster is not limited to marine environments, but has utility in any type of installation wherein an initial boosting torque is desirable for opening or closing a valve. 
     FIG. 1 is a cross section through a marine vessel having a main deck  11 , a sub-deck  12 , and a bulkhead  13 . Within the interior of the vessel is a valve  14  having a rod  15  which is rotated in one direction to open the valve and in the opposite direction to close the valve. 
     Flush with the surface of main deck  11  is a conventional deck box  16 , such as that shown in U.S. Pat. No. 6,112,694. Within the deck box is a fitting for actuation by an operator, such as a wrench, or alternatively a hand wheel  17  (see FIG. 2) may be used. The wrench or hand wheel is rotated in opposite directions to open and close, respectively, valve  14 . While a hand wheel  17  is used for manual operation of the valve, an automatic mechanism could be employed. 
     A linkage  18 , below main deck  11 , transmits rotary motion of hand wheel  17  to an operator shaft  19  of torque booster  10 , the latter being supported on a mounting bracket  21 . A valve operating stem  20  of the torque booster, coaxial with operator shaft  19 , connects torque booster  10  to rod  15  of valve  14 . 
     With reference to FIG. 2, the torque booster  10  chosen to illustrate the present invention includes a hollow cylindrical housing  23 , the housing being closed by two end caps  24  and  25 . Operator shaft  19  projects rotatably through end cap  24 , and valve operating stem  20  projects rotatably through end cap  25 . The shaft and stem may be suitably supported, such as by a bushing  26  (FIG. 3) 
     The torque booster mechanism within housing  23  is shown in FIGS. 3 and 4. The mechanism includes a gear reduction unit  28  which may be in the form of a planetary gear arrangement. The gear reduction unit includes a central spur gear  29 , coaxial with shaft  19  and stem  20 , and three planet gears  30 . Planet gears  30  are rotatably carried by a generally triangular support plate  31 . Each planet gear  30  is located between, and meshes with, central gear  29  and an annular gear  32  coaxial with central gear  29  and fixed with respect to housing  23 . It will be appreciated that rotation of central gear  29  causes rotation of planet gears  30  and hence rotation of support plate  31 , the speed of rotation of the support plate being slower than that of central gear  29 . 
     Planet gears  30  are mounted on one face of plate  31 , and projecting from the other face of the plate is a driving crown gear  35 . Crown gear  35  is coaxial with shaft  19  and stem  20 , as well as with central gear  29 . In addition, crown gear  35  is fixed to, and rotates with, support plate  31 . 
     A coupling  36  (FIGS. 3,  5 , and  6 ) is located between plate  31  and valve operating stem  20 . The coupling includes a hollow cylindrical sleeve  37  accommodating a piston  38  which is both slidable and rotatable with respect to sleeve  37 . The sleeve also slideably accommodates one end of valve operating stem  20 . Stem  20  is furnished with a pin  39 , projecting diametrically through stem  20 , the two ends of the pin being slidable within two slots  40  formed in sleeve  37 . As a result of this arrangement, sleeve  37  can slide axially with respect to stem  20 , and rotational movement of sleeve  37  is transmitted through pin  39  and slots  40  to stem  20 . At its end facing support plate  31 , sleeve  37  is formed with a driven crown gear  58  adapted to mesh with the driving crown gear  35  carried by plate  31 . 
     Piston  38  has an extension  43  (FIGS. 5-8) formed with a keyway slot  44 . A similar keyway  45  is formed in operator shaft  19 , at its end within housing  23 . Yet another keyway  46  (FIG. 4) is formed in the interior wall of central gear  29 . When the parts are assembled, a single key  47  (FIG. 3) is accommodated within all three keyways  44 ,  45 , and  46  so that rotation of operator shaft  19  causes rotation of central gear  29  and rotation of piston  38 . 
     Piston  38  is formed with two camming grooves  50  and  51  (FIGS.  5 - 8 ). Camming groove  50  has a central dwell section  50   a  substantially perpendicular to the axis of coupling  36 , and two ramp sections  50   b  and  50   c , each extending at an acute angle to the axis of the coupling. Ramp section  50   b  extends from one end of  50   d  (FIG. 8) of the groove to one end of dwell section  50   a , and ramp section  50   c  extends from the other end  50   e  of groove  50  to the opposite end of dwell section  50   a , the ramp sections converging from the ends of the groove toward the dwell section. Similarly, groove  51  includes a dwell section  51   a  and ramp sections  51   b  and  51   c  (not shown), similar in all respects to groove  50 , except that groove  51  is located 180° from groove  50  around the surface of piston  38 . 
     It will be seen that in the present example, each groove  50  and  51  has a length less than the full circumference of piston  38 . As illustrated, each groove extends for an angular distance of a little more than 180°. 
     Cylindrical sleeve  37  carries two diametrically opposed set screws  52  and  53 , each of which is threaded into an internally threaded hole extending through the thickness of the sleeve wall. At the inner end of screw  52  is a follower pin  54  slidably accommodated within groove  50 , and at the inner end of screw  53  is a follower pin  55  slidably accommodated within groove  51 . 
     Operation of the torque booster will now be explained with reference to FIGS. 5,  6 , and  9   a - 9   d . Assume the parts are in the condition shown in FIGS. 5 and 9 a , the valve  14  is open, and it is desired to close the valve. Rotation of hand wheel  17  in a valve-closing direction rotates operator shaft  19  which, through key  47  and extension  43 , rotates piston  38 . At the same time, key  47  also rotates central gear  29  as well as the rest of the gear reduction unit  28  so as to cause rotation of support plate  31  and crown gear  35 . However, at the outset, rotation of the gear reduction unit  28  and crown gear  35  have no effect on closing of the valve. Instead, the initial rotation of piston  38  moves follower pin  54  along ramp  50   b  of camming groove  50  from the relative position shown in FIG. 9 a  to the position shown in FIG. 9 b . A similar relative movement takes place with respect to follower pin  55  and groove  51 . This movement causes sleeve  37  to slide axially from the position shown in FIG. 5 to that shown in FIG. 6, thereby bringing crown gears  58  and  35  into meshing relationship, as indicated in FIG. 9 b.    
     At this point, further rotation of hand wheel  17  in the valve-closing direction causes relative movement of follower pin  54  through the dwell section  50   a  of groove  50  to the position shown in FIG. 9 c . During this movement of pin  54  within dwell section  50   a , crown gears  58  and  35  remain in meshing relationship, and hence rotary motion of operator shaft  19  is transmitted via gear reduction unit  28 , plate  31 , and the meshing crown gears to sleeve  37 . Rotation of sleeve  37  is transmitted by pin  39  and slots  40  to valve operating stem  20 . 
     Because this motion is transmitted by means of the gear reduction unit  28 , sleeve  37 , and hence stem  20 , rotate at a speed slower than the speed of operator shaft  19 . The ratio of the speed of stem  20  with respect to shaft  19  will depend upon the gear reduction ratio of unit  28 . A ratio of four to one has been found useful, but any appropriate gear reduction ratio may be used. The speed reduction of stem  20  is accompanied by an increase of torque applied by stem  20  to valve rod  15 , the increase in torque being proportional to the reduction of speed of stem  20 . In this way, a torque boost has been introduced during the initial closing movement of valve  14 . 
     Further rotation of hand wheel  17  in the valve-closing direction causes relative movement of follower pin  54  from the end of dwell section  50   a  along ramp section  50   c  to the end  50   e  of groove  50 , as shown in FIG. 9 d . During this movement, the cooperation of follower pin  54  and groove ramp section  50   c  slides sleeve  37  from its position shown in FIGS. 6 and 9 c  back to its original position shown in FIGS. 5 and 9 d . In this condition, crown gears  35  and  58  have been disengaged, as a result of which gear reduction unit  28  is now bypassed. Continued rotation of hand wheel  17  and hence operator shaft  19  directly rotates extension  43 , through key  47 , and piston  38 . Rotation of the piston causes rotation of sleeve  37  as a result of follower pins  54  and  55  being seated against the ends of their respective grooves  50  and  51 . Rotation of sleeve  37  produces rotation of valve operating stem  20  due to the engagement of pin  39  within grooves  40 . Since operator shaft  19  is now directly driving valve operating stem  20 , without the intercession of gear reduction unit  28 , there is no longer a torque boost applied to stem  20 , and the latter rotates at the same speed as shaft  19 . 
     When it is desired to open the valve, the operation just described is reversed. Hand wheel  17  is rotated in the valve-opening direction causing relative movement of pin  54  from the position shown in FIG. 9 d  to that shown in FIG. 9 c , thereby meshing crown gears  35  and  58 . In this way, gear reduction unit  28  is brought into play introducing a torque boost between shaft  19  and stem  20 . The torque boost lasts during further rotation of shaft  19  as pin  54  moves from its FIG. 9 c  position to that shown in FIG. 9 b . Continued rotation of shaft  20  than moves pin  54  to the position shown in FIG. 9 a , causing crown gears  35  and  58  to disengage, thereby bypassing the gear reduction unit  28 . 
     Throughout the rotation of shaft  19 , gear reduction unit  28  and plate  31  rotate constantly, but the gear reduction unit is interposed between the shaft  19  and stem  20  only when crown gears  35  and  58  are engaged. 
     In the illustrative embodiment of this invention just described, two camming grooves  50  and  51  are shown cooperating with two follower pins  54  and  55 . The device can operate with only a single groove  50  and single follower pin  54 . However, it has been found that use of two grooves and two followers arranged 180° apart stabilizes operation of the unit. Also, while the camming grooves have been shown in piston  38  and the follower pins carried by sleeve  37 , that arrangement could be reversed, with the grooves in the interior surface of the sleeve and the pins projecting from the piston. 
     The invention has been shown and described in preferred form only, and by way of example, and many variations may be made in the invention which will still be comprised within its spirit. It is understood, therefore, that the invention is not limited to any specific form or embodiment except insofar as such limitations are included in the appended claims.