Abstract:
A hydraulically-operated actuator for a braking mechanism on a cable drawworks is provided. The actuator can have an enclosed tubular main body capable of being connected to an external hydraulic system. The main body can further contain a spring-opposed hydraulic piston connected to an actuator rod. The actuator rod can extend out of the main body and can connect to a braking system for the drawworks. In operation, the springs can push on the hydraulic piston and hold the actuator rod in a fully extended position to engage the braking system. When pressure from the external hydraulic system is applied to the hydraulic piston, the hydraulic piston can compress the springs and retract the actuator rod into the main body, which can disengage the braking system.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority of U.S. Provisional Patent Application Ser. No. 61/653,280, entitled “Hydraulically-Operated Actuator for Drawworks”, filed May 30, 2012, and hereby incorporates the same provisional application by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure is related to the field of hydraulic actuators, in particular, linear hydraulic actuators for use in braking systems on electric drawworks or winches. 
     BACKGROUND 
     It is known to use pneumatic actuators to operate braking systems on electric drawworks, such as those disclosed in U.S. Pat. Nos. 7,527,245 and 8,079,569. Referring to  FIG. 1 , an example of such drawworks is shown and labelled as A, with the pneumatic actuators labelled as B. Such actuators are pneumatically powered to compress biasing springs contained therein, and to retract an actuating rod that removes force applied to brake bands C disposed around brake drums E on drawworks A, thereby allowing cable drum D on drawworks A to rotate. Upon removal of the pressurized air to actuators B, the biasing springs extend the actuating rod to apply force or tension to brake bands C, thereby stopping rotation of cable drum D. Pneumatically-operated actuators have shortcomings, one of which includes their susceptibility to corrosion and, therefore, failure to operate correctly once corroded. Another shortcoming is that air is compressible, which can make the control of pneumatically-operated actuators in a braking mechanism for a drawworks difficult. 
     It is, therefore, desirable to provide a hydraulically-operated actuator for a braking mechanism for a drawworks that overcomes the shortcomings of pneumatically-operated actuators. 
     SUMMARY 
     A hydraulic actuator for a braking system for a drawworks is provided. In some embodiments, the actuator can comprise a main body with a rod end and a butt end enclosing a fixed piston and a moveable cylinder. The moveable cylinder can comprise a head that can be connected to a rod extending out through the rod end of the main body, with the rod configured to receive a clevis or some other type of functional attachment. One or more springs can be placed between the butt end of the main body and the moveable cylinder, or against a spring pusher configured to operate with the moveable cylinder such that the moveable cylinder is pressed up against the rod end of the main body and the movement of the moveable cylinder towards the butt end of the main body is resisted. Hydraulic fluid can be injected into the rod end of the main body at a sufficient pressure to overcome this resistive force, causing the moveable cylinder to compress the one or more springs and to retract the rod into the main body. The hydraulic fluid can be released from the main body, wherein the one or more springs can expand to cause the movable cylinder to return to its default position against the rod end of the main body, causing the rod to fully extend out of the main body. In some embodiments, the rod can be operatively coupled to a braking mechanism on a drawworks wherein the rod is retracted into the actuator to remove a braking force applied to the drawworks when hydraulic fluid is injected into the actuator under pressure, and wherein the rod is extended from the actuator when the hydraulic fluid is released from the actuator wherein the one or more springs cause the rod to extend from the actuator to apply a braking force to the drawworks. In some embodiments, the actuator is constantly filled with hydraulic fluid, which can keep all of the internal components lubricated and can further prevent or protect the internal components from corrosion, which can compromise their operation. Furthermore, as hydraulic fluid is incompressible, it is possible to provide a greater deal of control over the operation of the actuator through an external hydraulic fluid control system, which can include the use of a spool valve, as well known to those skilled in the art, to inject pressurized hydraulic fluid into the actuator or to release pressurized hydraulic fluid from the actuator. 
     While the hydraulically-operated actuator described and claimed herein can have application in the operation of braking mechanisms for drawworks or winches, it is obvious to those skilled in the art that the hydraulically-operated actuator described and claimed herein can be used in any number of applications requiring a linear actuating rod mechanisms. 
     Broadly stated, in some embodiments, a hydraulically-operated actuator is provided, the actuator comprising: a tubular main body, the main body comprising a first end and a second end thereby defining a chamber therebetween, the main body further comprising a first end cap disposed at the first end and a second end cap disposed at the second end, thereby enclosing the chamber, the second end cap further comprising a first aperture for injecting pressurized hydraulic fluid into the chamber and a second aperture for releasing the hydraulic fluid from the chamber; a fixed piston comprising first and second ends, the first end operatively coupled to the first end cap within the chamber, thereby defining an annular space about the fixed piston within the chamber; a piston cylinder slidably disposed in the chamber, the piston cylinder configured for slidably receiving the second end of the fixed piston; at least one spring disposed in the annular space between the first end cap and the piston cylinder, the at least one spring configured to resist the motion of the piston cylinder towards the first end cap; and an actuating rod operatively coupled to the piston cylinder, the actuating rod comprising first and second ends, the first end operatively coupled to the head of the piston cylinder, wherein the second end extends from the head of the piston cylinder and through a third aperture disposed through the second end cap. 
     Broadly stated, in some embodiments, the tubular main body comprises a cylindrical main body. 
     Broadly stated, in some embodiments, the fixed piston can further comprise a piston passageway disposed between the first and second ends thereof thereby providing communication therebetween. 
     Broadly stated, in some embodiments, the first end cap can further comprise a breather cap disposed thereon, the breather cap in communication with the piston passageway. 
     Broadly stated, in some embodiments, the actuator can further comprise at least one anti-torsion bar disposed in the chamber between the first and second end caps, the piston cylinder configured to be slidably disposed on the at least one anti-torsion bar. 
     Broadly stated, in some embodiments, the at least one spring can be disposed about the at least anti-torsion bar. 
     Broadly stated, in some embodiments, the piston cylinder can further comprise a spring pusher, wherein the at least one spring is disposed between the first end cap and the spring pusher. 
     Broadly stated, in some embodiments, the at least one spring can comprises eight springs disposed in a spaced-apart configuration in the annular space. 
     Broadly stated, in some embodiments, the at least one anti-torsion bar can comprise eight anti-torsion bars disposed in a spaced-apart configuration in the annular space. 
     Broadly stated, in some embodiments, the actuator can further comprise a clevis coupler operatively disposed on the second end of the actuating rod. 
     Broadly stated, in some embodiments, an improved drawworks is provided, the improved drawworks comprising a cable drum, at least one brake drum, at least one brake band disposed about the at least one brake drum, and a braking mechanism for operating the at least one brake band, the improvement comprising a hydraulically-operated actuator disposed in the braking mechanism, the actuator comprising: a tubular main body, the main body comprising a first end and a second end thereby defining a chamber therebetween, the main body further comprising a first end cap disposed at the first end and a second end cap disposed at the second end, thereby enclosing the chamber, the second end cap further comprising a first aperture for injecting pressurized hydraulic fluid into the chamber and a second aperture for releasing the hydraulic fluid from the chamber; a fixed piston comprising first and second ends, the first end operatively coupled to the first end cap within the chamber, thereby defining an annular space about the fixed piston within the chamber; a piston cylinder slidably disposed in the chamber, the piston cylinder configured for slidably receiving the second end of the fixed piston; at least one spring disposed in the annular space between the first end cap and the piston cylinder, the at least one spring configured to resist the motion of the piston cylinder towards the first end cap; and an actuating rod operatively coupled to the piston cylinder, the actuating rod comprising first and second ends, the first end operatively coupled to the head of the piston cylinder, wherein the second end extends from the head of the piston cylinder and through a third aperture disposed through the second end cap 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view depicting a prior art drawworks mechanism. 
         FIG. 2  is a perspective view depicting one embodiment of a hydraulically-operated actuator. 
         FIG. 3  is a side elevation cross-sectional view depicting the hydraulically-operated actuator of  FIG. 2  with several of the internal components removed. 
         FIG. 4  is a side elevation cross-sectional view depicting the hydraulically-operated actuator of  FIG. 2 . 
         FIG. 5  is an exploded perspective view depicting the hydraulically-operated actuator of  FIG. 2 . 
         FIG. 6A  is a front elevation view depicting the rod end cap of the hydraulically-operated actuator of  FIG. 2 . 
         FIG. 6B  is a side elevation view depicting the rod end cap of  FIG. 6A . 
         FIG. 6C  is a perspective front view depicting the rod end cap of  FIG. 6A . 
         FIG. 6D  is a side elevation cross-sectional view depicting the rod end cap of  FIG. 6A  along section line A. 
         FIG. 7A  is a front elevation view depicting the piston end cap of the hydraulically-operated actuator of  FIG. 2 . 
         FIG. 7B  is a perspective view depicting the interior of the piston end cap of  FIG. 7A . 
         FIG. 7C  is a perspective view depicting the exterior of the piston end cap of  FIG. 7A . 
         FIG. 7D  is a side elevation cross-sectional view depicting the piston end cap of  FIG. 7A  along section line A. 
         FIG. 8A  is a front elevation view depicting the spring pusher of the hydraulically-operated actuator of  FIG. 2 . 
         FIG. 8B  is a perspective view depicting the one side of the spring pusher of  FIG. 8A . 
         FIG. 8C  is a perspective view depicting the opposite side of the spring pusher of  FIG. 8A . 
         FIG. 8D  is a side elevation cross-sectional view depicting the spring pusher of  FIG. 8A  along section line A. 
         FIG. 9A  is a front elevation view depicting the piston cylinder of the hydraulically-operated actuator of  FIG. 2 . 
         FIG. 9B  is a perspective view depicting the piston cylinder of  FIG. 9A . 
         FIG. 9C  is a side cross-sectional view depicting the piston cylinder of  FIG. 9A . 
         FIG. 10  is a perspective view depicting the actuator rod of the hydraulically-operated actuator of  FIG. 2 . 
         FIG. 11A  is a perspective view depicting the piston of the hydraulically-operated actuator of  FIG. 2 . 
         FIG. 11B  is a side cross-sectional view depicting the piston of  FIG. 11A . 
         FIG. 12A  is a front elevation view depicting the piston retainer of the hydraulically-operated actuator of  FIG. 2 . 
         FIG. 12B  is a side cross-sectional view depicting the piston retainer of  FIG. 12A  along section line A. 
         FIG. 12C  is a perspective view depicting the piston retainer of  FIG. 12A . 
         FIG. 13A  is a perspective view depicting a braking mechanism for the drawworks of  FIG. 1  with the hydraulically-operated actuator of  FIG. 2 . 
         FIG. 13B  is a side elevation view depicting the braking mechanism of  FIG. 13A . 
         FIG. 14  is a schematic depicting a hydraulic fluid control circuit for the hydraulically-operated actuator of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     A hydraulically-operated actuator is provided. In some embodiments, the actuator can be used as part of a braking mechanism for a drawworks mechanism like the one disclosed in U.S. Pat. No. 7,527,245 and No. 8,079,569. 
     Referring to  FIGS. 2  through to  12 C, one embodiment of a hydraulically-operated actuator is shown. In some embodiments, hydraulically-operated actuator  50  can comprise tubular main body  18  enclosed on one end by rod end cap  10  and on the other end by piston end cap  26 . In some embodiments, main body  18  can be cylindrical. Rod end cap  10 , main body cylinder  18  and piston end cap  26  can be held together by end cap bolts  19 , which can run parallel to the central axis of main body cylinder  18  and pass through rod end cap bolt passages  80  and piston end cap passages  92 . End cap nuts  17 , which can screw onto both ends of end cap bolts  19 , can fasten rod end cap  10 , main body cylinder  18  and piston end cap  26  together. Main body o-rings  16  can be placed in rod end cap main body o-ring slot  155  and in piston end cap main body o-ring slot  160 , and can provide an airtight barrier created between main body cylinder  18  and rod end cap  10 , and between main body cylinder  18  and piston end cap  26 , respectively. 
     In some embodiments, spring pusher  13  can be slidably disposed within annular spring chamber  75  of main body cylinder  18 . In some embodiments, one or more anti-torsion bars  14  can be disposed in spring chamber  75  in a spaced-apart configured therein, and can be oriented parallel to the central axis of main body cylinder  18 . In some embodiments, anti-torsion bars  14  can be disposed between rod end cap anti-torsion bar ports  85  and piston end cap anti-torsion bar ports  94 . In further embodiments, anti-torsion bars  14  can pass through anti-torsion bar passages  88  disposed through spring pusher  13 . In some embodiments, springs  15  can be disposed coaxially around anti-torsion bars  15  between spring pusher  13  and piston end cap  26 . In some embodiments, springs  15  can be disposed coaxially about anti-torsion bars  14  and further disposed in spring openings  90  disposed in spring pusher  13 , which can be coaxial with anti-torsion bar passages  88 . Springs  15  can be further disposed in piston end cap spring openings  96  disposed in piston end cap  26 , which can be coaxial with piston end cap anti-torsion bar openings  94 . 
     In some embodiments, piston cylinder  12 , can comprise piston cylinder head  100  and piston cylinder sidewall  102 , and can be further disposed coaxially with spring pusher  13 . In some embodiments, the outer diameter of piston cylinder sidewall  102  can correspond to the inner diameter of piston cylinder port  86  disposed through spring pusher  13  such that piston cylinder sidewall  102  can pass though piston cylinder port  86 . The diameter of piston cylinder head  100  is configured such that piston head  100  is unable to pass through piston cylinder port  86 . 
     In some embodiments, actuator rod  6  can comprise piston cylinder tie-in end  110 , threaded bolt opening  111 , clevis tie-in end  112  and rod midsection  114 , which can pass through rod end cap  10  through rod passage  82  disposed therethrough. The outer diameter of rod midsection  114  can correspond to the inner diameter of rod passage  82  such that actuator rod  6  can slide back and forth through rod passage  82  at rod midsection  114 . In some embodiments, rod wiper  7  can disposed coaxially along rod passage  82  in rod wiper slot  150 ; rod seal  8  can be disposed coaxially along rod passage  82  in rod seal slot  151 ; and rod wear band  9  can be disposed coaxially along rod passage  82  in rod wear band slot  152 . In some embodiments, rod wiper  7 , rod seal  8  and rod wear band  9  can maintain a slight gap between rod passage  82  and rod midsection  114 . Rod wiper  7  can clear external dirt and debris from rod midsection  114 . Rod seal  8  can provided an airtight barrier between rod passage  82  and rod midsection  114 . Rod wear band  9  can prevent wear on rod passage  82  from rod midsection  114 . 
     In some embodiments, piston cylinder tie-in end  110  of actuator rod  6  can pass through rod port  84  of piston cylinder  12  wherein bolt  21  can be screwed into threaded bolt opening  111  of actuator rod  6  such that the edge of rod midsection  114  fits tightly against piston cylinder head  100 . This fit can be assisted by washer  20 , which can be placed between bolt  21  and piston cylinder head  100 . Rod o-ring  11  can be placed coaxially with rod port  84  in rod o-ring slot  105 , and can provide an airtight barrier is created between piston cylinder tie-in end  110  and rod port  84 . 
     In some embodiments, the portion of rod midsection  114  extending beyond rod end cap  10  can be covered by rod boot  4 , which can prevent dirt, dust or debris from entering hydraulically-operated actuator  50  through rod passage  82 . Rod boot  4  can be made of a compressible, resilient material in an accordion-like configuration and can be secured in place by a compression fit between jam nut  3 , which can screw onto the threads of clevis tie-in end  112  to fit tightly against the edge of rod midsection  114 , and rod boot centralizer  5 , which can have an inner diameter corresponding to the outer diameter of rod midsection  114  such that rod boot  5  can slide around rod midsection  114  and sit against rod end cap outer face  120 . In some embodiments, actuator clevis  2  can screw tightly onto to clevis tie-in end  112 . 
     In some embodiments, piston  25  can comprise piston sidewall  130  and piston retainer end  131 , which can pass though piston retainer port  98  disposed through piston end cap  26 , and which can be coaxial with main body cylinder  18 , piston cylinder  12 , spring pusher  13  and actuator rod  6 . Piston  25  can further comprise piston passageway  137  extending therethrough. In some embodiments, piston  25  can be configured such that the outer diameter of piston retainer end  131  can correspond to the inner diameter of piston retainer port  98 . In some embodiments, the outer diameter of piston sidewall  130  can be wider than piston retainer port  98  while corresponding to the inner diameter of piston cylinder sidewall  102  such that piston cylinder  12  can slide back and forth along piston  25 , which can remain fixed in place. In some embodiments, piston retainer  28  can comprise piston retainer threads  171  that can screw into piston threads  132  to secure the edge of piston sidewall  130  against piston end cap inner face  126  while piston retainer flange  172  can be secured against piston end cap outer face  125 . In some embodiments, piston retainer o-ring  27 , can be disposed in piston retainer o-ring slot  170  on piston retainer  28 , can provide a seal between piston retainer flange  172  and piston end cap outer face  125 . 
     In some embodiments, piston sidewall  130  can comprise piston seal slot  135  with piston seal  23  disposed therein, and can further comprise piston wear band slot  136  with piston wear band  24  disposed therein. Piston seal  23  can provide an airtight barrier between the outside of piston sidewall  130  and the inside of piston cylinder sidewall  102 . Piston wear band  24  can prevent wear on the inside of piston cylinder sidewall  102  from the outside of piston sidewall  130 . In some embodiments, the lengths of piston cylinder  12  and piston  25  can be configured such that the piston cylinder sidewall  102  can overlap piston sidewall  130  regardless of the position of piston cylinder  12 . In some embodiments, stroke limiter  22 , can be disposed in a coaxial position within piston cylinder  12  adjacent to piston cylinder head  100 , wherein stroke limiter  22  can limit the linear movement of piston cylinder  12  along piston  25 . Together, piston cylinder  12  and piston passageway  137  can form piston cavity  70 , which can vent to the atmosphere though piston retainer vents  173  thereby allowing piston cavity  70  to “breathe” as piston cylinder  12  moves along piston  25 . 
     In operation, the default position of piston cylinder  12  is shown in  FIG. 4 . Springs  15  push on spring pusher  13 , which can push on piston cylinder head  100  and causes piston cylinder head  100  to rest against rod end cap inner face  121 . In this position, actuator rod  6  can be fully extended. In order for hydraulically-operated actuator  50  to operate, it must be filled or “primed” with hydraulic fluid. To prime hydraulically-operated actuator  50  with hydraulic fluid, hydraulic fluid can be injected through hydraulic fluid port  60  to displace air contained in hydraulically-operated actuator  50 , which can exit or “bleed” through bleed port  61 . Once hydraulically-operated actuator  50  is filled with hydraulic fluid, bleed port  61  can be sealed off with a screw or plug (not shown), as well known to those skilled in the art. To retract actuator rod  6 , hydraulic fluid from an external hydraulic control circuit or system can be injected under pressure into hydraulic chamber  62  through hydraulic fluid port  60 . Although hydraulic chamber  62  is not completely isolated from spring chamber  75 , the hydraulic fluid disposed in hydraulic chamber  62  can exert pressure over a greater surface area on the combination of piston cylinder head  100  and spring pusher  13  than the hydraulic fluid disposed in spring chamber  75 . Thus, when the pressure of the hydraulic fluid is great enough, the hydraulic force acting on piston cylinder head  100  and spring pusher  13  in hydraulic chamber  62  can overcome the force exerted on spring pusher  13  by springs  15  and the hydraulic pressure in spring chamber  75 . When this pressure threshold is exceeded, piston cylinder  12  and spring pusher  13  can move towards piston end cap  26  until piston  25  comes into contact with stroke limiter  22 . When the hydraulic pressure in hydraulic chamber  62  is released by allowing hydraulic fluid to exit hydraulic chamber  62  though hydraulic fluid port  60 , the force exerted on spring pusher  13  by springs  15  can cause piston cylinder  12  to move towards rod end cap  10  until piston cylinder head  100  returns to its resting place against rod end cap inner face  121 . Piston cavity  70  is sealed from hydraulic chamber  62  and spring chamber  75 . Piston cavity  70  can be vented to the atmosphere through piston retainer vents  173  on piston retainer  28 . 
     In one embodiment, hydraulically-operated brake actuator  50  can be used to operate braking bands such as the ones used on the drawworks mechanism disclosed in U.S. Pat. No. 7,527,245 and No. 8,079,569. 
     Referring to  FIGS. 13A and 13B , hydraulically-operated brake actuator  50  can be operatively coupled to braking mechanism  200  disposed on a drawworks, such as the one shown in  FIG. 1 . With clevis  1  coupled to crank  202 , operating hydraulically-operated actuator  50 , as described above, to retract actuator rod  6  can rotate crank  202  to loosen brake band  204  disposed around a brake drum disposed on a cable drum of the drawworks, such as brake band C disposed around brake drum E of drawworks A as shown in  FIG. 1  and as described in U.S. Pat. No. 7,527,245 and No. 8,079,569. When hydraulic fluid is released from hydraulically-operated actuator  50 , actuator rod  6  can extend to reverse the rotation of crank  202  to tighten brake band  204  around a brake drum so as to stop the rotation of the cable drum. 
     Referring to  FIG. 14 , one embodiment of a hydraulic fluid control circuit for use with hydraulically-operated actuator  50  is shown. In some embodiments, hydraulic fluid control circuit  300  can comprise valve  304 , which can control pressurized hydraulic fluid supplied by a hydraulic fluid system (not shown) via supply line  306 . In some embodiments, valve  304  can comprise a spool valve, as well known skilled in the art. In some embodiments, operating valve  304  can direct pressurized hydraulic fluid received from the hydraulic fluid system via supply line  306  to hydraulically-operated actuator  50  via supply line  302 , which can be operatively connected to hydraulic fluid port  60 . In so doing, actuator rod  6  can be retracted into hydraulically-operated actuator  50 . In further embodiments, valve  304  can also be operated to allow pressurized hydraulic fluid to be released from hydraulically-operated actuator  50  through hydraulic fluid port  60 , pass through supply line  302  to valve  304 , and then pass through valve  304  to return line  308 , which can return the released hydraulic fluid to the hydraulic fluid system. In so doing, actuator rod  6  can extend from hydraulically-operated actuator  50  due to the operation of the springs contained therein. 
     Although a few preferred embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention. The terms and expressions used in the preceding specification have been used herein as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims that follow.