Abstract:
A hydraulically powered switch machine having power and manual operating modes, and a dual disconnect mechanism. In power operation mode, the machine may be operated remotely, or using controls located on or near the machine. In the event of power failure, the machine may be operated manually. The dual disconnect mechanism physically disconnects the powered throw mechanism when the machine is operating in manual mode and physically disconnects the manual throw mechanism when the machine is operating in power mode, in both cases preventing unexpected movement of the manual throw mechanism.

Description:
FIELD OF THE INVENTION 
     This invention relates to switch machines. In particular, this invention relates to hydraulically operated switch machines having dual independent control mechanisms. 
     BACKGROUND OF THE INVENTION 
     Switch machines are used to move railroad switch points. Many machines are manually operated, requiring an operator to physically force a manual throwing device to move, working against the weight of the switch points and the effects of friction and inertia. In response to the high physical toll such machines took on the operator, switch machines, such as those described in U.S. Pat. No. 4,938,438 to Farrell, U.S. Pat. No. 5,419,518 to Fiorenzo and U.S. Pat. No. 5,494,243 to Kuhn, were improved to provide a better mechanical advantage and ease the physical load on the operator. 
     Many switch machines also have power operating modes, such as those described in U.S. Pat. No. 5,775,647 to Wyatt, German Patent No. 3825182 to Windgassen et al., each of which disclose hydraulically-assisted switch machines. It is also known to use electrically powered switch machines, such as those disclosed in U.S. Pat. Nos. 6,427,950 and 6,568,641, both to Hoyer et al. 
     While hydraulic machines generally contain fewer parts than electrical machines and therefore are simpler and cheaper to construct and maintain, electrical machines were said to be an improvement over hydraulic machines because the hydraulic machines could be susceptible to failure due to leakages in the machine itself as well as all external pipes, conduits and hoses, and because hydraulic machines require an external source of hydraulic power, which is not always readily available. However, electrically powered machines also require a power source to operate the machine. In some lightly populated or underdeveloped areas, it may be difficult to ensure that a reliable power source is always available, and also difficult to constantly have someone checking the machine. Further, if for some reason a power source is unavailable, a powered switch machine is inoperable. 
     It is therefore preferable to provide a secondary manual operating mode, so that a switch machine may be operated even without power. U.S. Pat. No. 8,297,559 to Voegeli et al. describes a hand throw mechanism designed to be retrofitted on an in-tie electrical switch machine, to operate the machine in case of power loss. U.S. Pat. Nos. 6,164,601 and 7,267,304 to Scheer et al. disclose electrical switch machines with manual hand throw levers to be used when electrical power is not available. Other dual control machines are described in U.S. Pat. No. 5,417,392 to Wyatt, which provides a hand pump by which the hydraulic fluid within the system may be manipulated to operate the points. U.S. Pat. No. 4,213,588 to Bowles discloses a hydraulic actuator on a trailable switch machine having a pair of manual controls to move a hydraulic valve manually, thereby allowing manipulation of the fluid within the machine as needed to move the points. U.S. Pub. No. 2011/0049308 to Beaman et al. discloses a hydraulic switch machine in which the dual control comprises a hand pump for manual operation, and a hydraulic actuator for power operation. A directional selection lever may be used to move a first directional control valve to select manual operation, or to move a second directional control valve, which is electrically controlled by valve control solenoids, to select powered operation. Controls within the hydraulic manifold hydraulically isolate the hand pump during power operation. However, none of Wyatt, Bowles or Beaman addresses the issue of manually actuating the machine if hydraulic pressure is not available. 
     Another potential issue with such machines is the nature of the control over the operating mode. If an operator is in the process of manually throwing a switch and power is suddenly restored to the machine, the interdependence between the power and manual operating modes generally means that the manual throw lever could suddenly begin to move on its own with great force, potentially causing serious injuries to the operator. 
     In electrical switch machines, this issue has been typically addressed by disrupting the power circuit when the switch machine operates in manual mode. U.S. Pat. No. 5,504,405 to Hager discloses a powered system with a manual operating option, in which an electrical cutout switch is provided as a fail-safe mechanism. One drawback with this type of system is the possibility of tampering; with an electric motor, it is possible to bypass the cutout switch and allow the motor to operate even if the system appears to be in manual mode. U.S. Pat. No. 3,691,371 to Hylen describes a powered system with a manual operating option, in which an electrical cutout switch is provided in cooperation with a manual throw lever to prevent the motor from operating when the hand throw lever is not in its resting position. As a secondary fail-safe, Hylen also describes a lock plate that must be moved before the manual throw lever can be operated; movement of the lock plate disrupts the electrical circuit and shorts out the motor. However, as noted, a safety mechanism that relies solely on disrupting the electrical circuit may be bypassed. 
     With respect to hydraulic switch machines, similar steps can be taken, such as disconnecting the power source to the hydraulics when the switch machine is in manual operating mode, as described in U.S. Pat. No. 8,302,915 to Biagiotti. Again, this is not completely fail-safe, as a hydraulic motor could itself be shorted to provide power, even if its battery is disconnected. 
     It is therefore an object of this invention to provide a switch machine that overcomes some or all of the foregoing difficulties. 
     It is a further object of the invention to provide a switch machine that combines an independent hydraulic powered operating mode with an independent manual operating mode and a dual disconnect mechanism to positively mechanically prevent the machine from operating in one mode if the other mode is selected. 
     It is a further object of the invention to provide a switch machine that combines an independent hydraulic powered operating mode with an independent manual operating mode, a dual disconnect mechanism to positively mechanically prevent the machine from operating in one mode if the other mode is selected, and a second disconnect mechanism to positively electrically prevent the machine from operating if the dual disconnect mechanism is not properly engaged in the power operating mode. 
     These and other objects of the invention will be better understood by reference to the detailed description of the preferred embodiment which follows. Note that the objects referred to above are statements of what motivated the invention rather than promises. Not all of the objects are necessarily met by all embodiments of the invention described below or by the invention defined by each of the claims. 
     SUMMARY OF THE INVENTION 
     In one aspect, the invention comprises a switch machine for switch stands controlling points at a switch. In power operation mode, the machine may be operated remotely, or using controls located on the machine. In the event of power or hydraulic failure, the machine may be operated manually. The machine comprises a dual disconnect mechanism to disconnect the hydraulic throw mechanism when the machine is operating in manual mode and prevent unexpected movement of the manual throw mechanism, which could injure a worker attempting to manually throw the switch points. Similarly, the dual disconnect mechanism disconnects the manual throw mechanism when the machine is operating in power mode, such that movement of the switch points will not move the manual throw mechanism, avoiding the possibility of injuring a nearby worker. 
     In one aspect, the invention comprises a switch machine having hydraulic power and manual operating modes, the switch machine comprising a hydraulic actuation system operatively connected to a drive shaft to actuate the drive shaft in the power operating mode; a manual actuation system operatively connected to the drive shaft to actuate the drive shaft in the manual operating mode; and a selector system to selectively operatively disconnect one of the hydraulic actuation system and the manual actuation system from the drive shaft. 
     In a further aspect the selector system may cause the hydraulic actuation system to disengage from the drive shaft in the manual operating mode, and the manual actuation system to disengage from the drive shaft in the power operating mode. The disengagement may be caused by a clutch moving a travelling distance along the drive shaft. In some embodiments, the clutch has a tooth depth, and the travelling distance is preferably greater than the tooth depth, and may be at least twice the tooth depth. 
     In a further aspect, the manual actuation system comprises a manual throw actuator; and one or more gears actuated by the manual throw actuator; at least one of the one or more gears being operatively connected to the drive shaft. Various types of manual throws may be provided and are intended to be included within the terms “manual throw” and “manual throw actuator”. The at least one or more gears may be operatively engageable with the drive shaft, and may be operatively selectively engageable with the drive shaft by movement of the selector system. Various types of selectors and selector systems may be provided and are intended to be included within the terms “selector” and “selector system”. The clutch engages and disengages with the gears by moving a travelling distance along the drive shaft. 
     The clutch has a tooth depth, and the travelling distance is preferably greater than the tooth depth, and may be at least twice the tooth depth. 
     In a further aspect, the hydraulic actuation system comprises a hydraulic actuator powered by a hydraulic power unit, the hydraulic actuator being operatively connected to the drive shaft. 
     The switch machine may further comprise a power drive gear actuated by the hydraulic actuator, the power drive gear being engageable with the drive shaft. The power drive gear may be operatively engageable with the drive shaft through a clutch, which engages and disengages with the gear by movement of the selector means. The clutch engages and disengages with the power drive gear by moving a travelling distance along the drive shaft. 
     The clutch has a tooth depth, and the travelling distance is preferably greater than the tooth depth, and may be at least twice the tooth depth. 
     In a further aspect, the switch machine may further comprise an electrical cutoff switch to disconnect the hydraulic actuation system. The cutoff switch monitors the disengagement and disconnects power to the hydraulic actuation system when the hydraulic actuation system is disengaged from the drive shaft. 
     In a further aspect, the hydraulic actuation system and manual actuation system are independent of one another. 
     The foregoing was intended as a summary only and of only some of the aspects of the invention. It was not intended to define the limits or requirements of the invention. Other aspects of the invention will be appreciated by reference to the detailed description of the preferred embodiments. Moreover, this summary should be read as though the claims were incorporated herein for completeness. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described by reference to the detailed description of the preferred embodiment and to the drawings thereof in which: 
         FIG. 1  is a top view of a switch stand and the switch machine of the invention; 
         FIG. 2  is cutaway view of the switch stand and switch machine, taken along line A-A; and 
         FIG. 3  is an enlarged view of the disconnect mechanisms in the switch machine of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIGS. 1 and 2 , a switch stand  10  is adapted to be connected to the railroad switch points (not shown) to move the points between first and second positions. A pivoting shaft or spindle  12  is operatively connected to the switch points and carries a target  13  to indicate whether the switch points are in the first or second position. A housing  14  for the switch machine  16  has a cover (not shown) and a first opening  18  through which the switch machine  16  is connected to the switch stand  10  to translate movement within the switch machine  16  to movement of the switch points. 
     The housing  14  contains operating mechanisms for both manual and power operating modes, as well as a dual disconnect mechanism by which either the manual or power operating mechanism is rendered inoperable once the other operating mode is chosen. 
     The power operating mechanism is a hydraulic actuation system that includes a hydraulic power unit  22 , which in turn actuates a hydraulic rotary actuator  24 . A battery  20  or other suitable power source may be provided to power the hydraulic power unit  22 . Movement of the hydraulic rotary actuator  24  rotates a drive shaft  26  via a power drive gear  27  engaged with an engagement means. Various types of engagement means may be provided and are intended to be included within the term “engagement means”; in the embodiment illustrated, the engagement means is an engagement clutch  30 , on drive shaft  26 . Drive shaft  26  in turn actuates switch stand adapter  28 , which is operatively connected to the spindle  12  and the switch points. Rotation of the switch stand adapter  28  therefore moves the switch points from one position to another, and rotates the spindle  12  to indicate the point position. As the switch machine  16  may be used with any suitable switch stand  10 , it will be understood that the actual components connecting the switch machine  16  and the switch stand  10  to actuate the switch points depend on the particular structure of the switch machine  10 , and do not form part of the invention. 
     The housing  14  also contains a second opening  32  through which parts of the manual operating mechanism and operating mode selector pass. The manual operating mechanism is a manual actuation system that includes a manual throw shaft  34  actuated by a manual throw lever  38 . The operating mode selector may comprise a selector lever  40  or any other suitable actuator that allows a user to actuate operating mode selector shaft  36 . Any suitable operating mode selector to secure the levers  38 ,  40  against unauthorized or unintended movement, such as foot latches  42 , and other types of mechanically actuatable mechanisms, may also be provided. The manual operating mechanism may further include a manual driver gear  44  operatively connected to and actuated by the manual throw shaft  34 , and one or more driven gears  46 , at least one of which is operatively connectable to the switch stand adapter  28 , and therefore to the spindle  12  and the switch points. A scotch yoke  48  and a linkage  50  are also provided to operatively connect selector shaft  36  to engagement clutch  30 . 
     When the selector lever  40  is in power mode, the engagement clutch  30  is fully engaged with the hydraulic rotary actuator  24 , and is fully disengaged and physically separated from the manual driven gear  46 . The hydraulic power unit  22  actuates the rotary actuator  24 , rotating the engagement clutch  30 , the drive shaft  26  and the switch stand adapter  28 , which in turn throws the switch points and rotates the spindle  12 . In the power operating mode, the operation of the switch machine  16  may be controlled remotely, or may be controlled with controls located on or near the switch machine  16  or switch stand  10 . 
     When the selector lever  40  is moved to manual mode, selector shaft  36  rotates, causing scotch yoke  48  to rotate. This rotation moves linkage  50 , and in turn causes engagement clutch  30  to move a travelling distance away from hydraulic rotary actuator  24 , and towards driven gear  46 . When the selection of manual operating mode is complete, engagement clutch  30  is fully engaged with the manual driven gear  46 , and is fully disengaged and separated from the hydraulic rotary actuator  24 . Manually throwing the throw lever  38  will therefore cause the manual throw shaft to rotate, in turn rotating the gears  44 ,  46 , the engagement clutch  30 , the drive shaft  26  and the switch stand adapter  28 , and actuating the switch points and the spindle  12 . 
     When the selector lever  40  is returned to power mode, the reverse operation happens: scotch yoke  48  rotates and moves linkage  50 , which causes engagement clutch  30  to disengage from driven gear  46  and move a travelling distance towards hydraulic rotary actuator  24 . If the switch points have been manually thrown an odd number of times, the rotary actuator  24  will self-align to properly engage its face with engagement clutch  30 . If the switch points have been thrown manually an even number of times, the rotary actuator  24  does not need to self-align because it is still in proper alignment with the engagement clutch and can simply re-engage. Upon completion of the engagement between clutch  30  and rotary actuator  24 , the hydraulic actuation system is fully connected and ready to move the switch points. 
     The movement of engagement clutch  30  between the rotary actuator  24  and driven gear  46  therefore provides a secure dual disconnect mechanism. The hydraulic actuation system of the switch machine  16  is rendered inoperable if the machine is in manual operating mode, even if power is flowing through the hydraulic system. The manual actuation system of the switch machine  16  is rendered inoperable if the machine  16  is in power operating mode, such that movement of the drive shaft  26  will not cause the manual throw lever  38  to move, while movement of the manual throw lever  38  will not affect the powered operation of the switch machine  16 . Such a dual safety mechanism practically eliminates the chances that a mishap can be caused by unexpected machine activation. 
     Preferably the travelling distance over which the engagement clutch  30  moves is greater than the tooth depth of the engagement clutch  30 , such that when engagement clutch  30  is properly connected to the rotary actuator  24 , there is a separation distance between the engagement clutch and the driven gear  46 , and vice versa. The travelling distance may be approximately twice the tooth depth of the engagement clutch, in order to ensure that the separation distance is sufficient. This provides a means to physically mechanically disconnect the two operating means; if the engagement clutch is not physically connected to either of the rotary actuator  24  or the driven gear  46 , the switch machine  16  will not operate, even if, for example, the hydraulic power unit  22  is shorted to run, or if the manual lever  38  is thrown. 
     As a further safety factor, an electrical cutoff switch, such as electrical interlock proximity switch  52 , best shown in  FIG. 3 , may be provided. This switch monitors the position of the engagement clutch  30 , and if the clutch  30  is not in the power operating position, i.e. the engagement clutch  30  is not fully engaged with rotary actuator  24 , power is prevented from flowing to the hydraulic power unit  22 , and the machine is prevented from operating in the power mode. However, the machine may be operated in the manual operating mode as long as the engagement clutch  30  is properly engaged with the driven gear  46 . 
     The switch machine  16  is adapted to continue operating as intended after being trailed through, whether it is operating in power or manual operating mode. The control system will recognize a trail operation and will rotate the drive shaft  26  in both directions to attempt to complete a throw, but the internal components of the switch machine  16  will not be adversely affected or require resetting after being trailed through. 
     In the foregoing specification, the invention has been described with reference to specific embodiments thereof. However, the scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.