CA2249764A1 - Parking brake system - Google Patents

Abstract

A parking brake system for applying the brakes 64 of a vehicle includes a hydraulic portion and a mechanical lock portion. The hydraulic portion includes a cylinder 70 for receiving fluid under pressure, and a rod 72 which is movable within the cylinder 70 by the pressurized fluid. The rod 72 is in mechanical communication with the brakes 64 of the vehicle, and the rod 72 may be moved in a first direction for applying the brakes 64 and in a second direction for releasing the brakes 64. The hydraulic portion also includes a control valve 106 that may be activated for preventing fluid from exiting the cylinder 70, whereby when the control valve 106 is activated, the rod 72 is prevented from moving to release the brakes 64. The mechanical lock portion may be activated independently of the hydraulic portion, and allows the rod 72 to be moved in the first direction for applying the brakes 64, but prevents the rod 72 from being moved in the second direction to release the brakes 64. The mechanical lock portion and the hydraulic portion act as backups to eachother so that if one of the portions fails, the other portion will still hold the brakes 64 in the applied position.

Description

PARKING BRAKE SYSTEM

This invention is generally directed to a parking brake for use in a vehicle.
Specifically, the system includes both hydraulic and mechanical means for locking the brakes of a railway vehicle in an activated position.
DESCRIPTION OF THE PRIOR ART
In railway cars and other vehicles, it is common to use a pneumatic or hydraulic cylinder to activate the brakes. In particular, a pneumatic cylinder is often used to activate the service brake system of such a vehicle. The service brake system is used while the railway car is in motion for slowing or stopping the car, and generally includes drum or disc brakes mounted on one or more of the car's axles15 for applying stopping friction to the wheels. The brakes are connected to a brake linkage which is acted upon by the pneumatic cylinder for simultaneously applying all the brakes on the railway car. When the railway car is incorporated into a train of railway cars, the pneumatic cylinder is connected to a control system so that the brakes of the car may be remotely actuated.
When a railway car is to be parked for a period of time, either alone, or as part of a train, it is desirable to have a parking brake system for holding the brakes in the activated position. This prevents runaway cars and other similarly dangerous situations.
FIG. 1 illustrates a railway car brake system having a conventional prior art parking brake system. A railway car 20 has a service brake cylinder 22 which maybe pneumatically activated for moving a rail car brake lever 24 in the direction of arrow 26. Brake lever 24 is pivotally mounted on a pivot point 27 at one end, and the movement of brake lever 24 pulls on a brake linkage 28 which is connected to brake lever 24 at the end opposite to pivot point 27. The movement of brake linkage 28activates the brakes (not shown), for slowing or stopping railway car 20.
A handwheel parking brake system is provided on rail car 20 for activating the brakes as a parking brake. The handwheel system includes a handwheel 30 having a retractable cable or chain 32 which is connected to brake lever 24. To apply the parking brake, a worker turns handwheel 30 to take up chain 32. Handwheel 30 includes a ratchet mechanism 34 so that chain 32 and handwheel 30 do not slip backwards following the application of torque. The handwheel 30 is turned until chain 32 is drawn up very tightly, thereby pulling on brake linkage 28 and applying the brakes. When chain 32 has been drawn up tightly, chain 32 will hold the rail car 5 brakes in the activated position until the ratchet mechanism 34 of handwheel 30 is released.
The above-described parking brake system works adequately when properly implemented. However, this system requires that a worker turn a handwheel 30 on each railway car so that the handwheel chain 32 reaches a particular degree of 10 tautness. Turning handwheel 30 is time consuming and requires a certain degree of physical strength. It is also possible that the worker will not turn the handwheel 30 sufficiently for the chain 32 to reach the proper tautness, thereby resulting in a situation in which the parking brake is not properly applied.
It has also been known in the past to use a hydraulic parking brake system 15 in place of the handwheel system. In particular, it is known to have a system which incorporates a hydraulic hand pump for delivering fluid to a hydraulic cylinder. The fluid is used to pressurize the hydraulic cylinder, thereby moving the cylinder rod to apply the brakes. Once the brakes have been applied, a lock nut within the cylinder is moved by hydraulic pressure into a locking position for locking the cylinder and 20 brakes in the applied position. The fluid pressure within the cylinder is then released, and the brakes are held in the applied position solely by the lock nut. Under this system, the lock nut is operated by the same hydraulic system which applies pressure to the cylinder. Thus, if the pressure in the hydraulic system fails due to a leak or the like, the lock nut may not be properly applied, or prematurely released.
25 If the locknut fails, is released, or is not applied, then there is no backup to ensure that the parking brake is not released.
It has also been known in the prior art to attach mechanical locking devices to existing brake systems of vehicles. For example, U.S. Patent No. 3,874,747, to Case, shows an arrangement in which a service brake cylinder rod is formed with a 30 plurality of teeth. The teeth have one inclined face and one perpendicular face relative to the axis of the rod. The teeth on the rod are engaged by a spring-loaded pawl which also has one inclined face and one perpendicular face. The inclined .

planes on the teeth and pawl allow the rod to be moved in one direction. As the rod moves, the relative sliding between the inclined planes causes the pawl to be pushed upward against the spring load. This allows one or more teeth on the rod to slip past the pawl in one direction. The spring load forces the pawl back into engagement with 5 the teeth on the rod, thereby preventing movement of the rod in the opposite direction because of the positive stop of the engaging perpendicular faces. The arrangement of the Case patent does not include a redundant hydraulic lock backup, however, and relies on a service brake pneumatic cylinder to apply the brakes, with the mechanical lock serving as the only lock.
Consequently, it is apparent that a need exists for an improved method and apparatus for providing a railway car parking brake. The system should be safe, reliable, easily applied, retlurillable onto existing railway cars, and should be consistently applied regardless of the strength of the individual implementing the system. It is also desirable to have a parking brake which is self-adjusting so as to 15 compensate for wear in the brakes or other moving parts, thereby ensuring that maximum braking efficiency is maintained at all times. The present invention overcomes the shortcomings associated with the above-described priorsystems, andprovides a substantial advancement in the art.
SUMMARY OF THE INVENTION
The present invention is directed to a parking brake system for a railway car, and embodies a combined hydraulic and mechanical arrangement for applying and holding the railway car brakes in the applied position. The system includes a hydraulic cylinder in fluid communication with both a hydraulic hand pump and a hydraulic reservoir which supply fluid to the cylinder. The cylinder has an extensible rod that is connected to a brake lever. The brake lever is also connected to theservice brake cylinder and the brake linkage, as in the prior art described above in FIG. 1. The hydraulic hand pump is used to pressurize the cylinder to apply the brakes. A pop-up indicator or pressure gage is provided for indicating when sufficient cylinder pressure has been reached for the brakes to be applied. A control 30 valve, when open, allows hydraulic fluid to move in and out of the hydraulic cylinder.
When the control valve is closed, the cylinder rod is locked from retracting into the cylinder, and the brake lever is thereby prevented from moving in that direction to __ release the brakes. The cylinder rod may still be extended, however, to apply the brakes.
The system also includes an independently actuated mechanical rod lock for preventing the hydraulic cylinder rod from retracting from the set position. The5 cylinder rod passes through the center of the rod lock housing, and includes aserrated rack area formed along at least a portion of its length. The rack area has a plurality of teeth for engaging with a pair of toothed jaws located in the rod lock housing. The jaws are located on either side of the cylinder rod, and each jaw is in sliding contact with fixed wedges mounted within the lock housing. A spring load10 forces the jaws toward the fixed wedges, the inclined surfaces of the fixed wedges force the jaws inward toward the cylinder rod for engaging the jaw teeth with the teeth on the cylinder rod, thereby providing a gripping and locking action. When the rod lock is activated, the rod lock allows the cylinder rod to be moved in one direction by overcoming the spring load, but prevents movement of the cylinder rod in the 15 other direction. When the rod lock is not activated, the movement of the cylinder rod in either direction is not inhibited by the rod lock.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a conventional prior art parking brake system for a railway car.
FIG. 2 shows an installation view of the parking brake system of the present 20 invention, looking down through the floor of a rail car.
FIG. 3 shows an elevation view of the parking brake system of FIG. 2.
FIG. 4 shows a schematic of the parking brake system of the present invention.
FIG. 5 shows an enlarged view of the rod lock of the present invention taken 25 from the view of FIG. 3.
FIG. 6 shows a top view of the rod lock of FIG 5.
FIG. 7 shows an end view of the rod lock of FIG. 5 FIG. 8 shows a cross-section view of the rod lock of FIG. 5 taken along line 8-8, with the rod lock actuating lever in the unlocked position.
FIG. 9 shows an enlarged cross-section view of the rod lock of FIG. 5 taken along line 9-9.

. ., FIG.10 shows an enlarged cross-section view of the rod lock of FIG. 5 taken along line 10-10.
FIG.11 shows the cross-section view of FIG. 9 demonstrating the ratcheting action of the rod lock of the present invention.
FIG. 12 shows the cross-section view of FIG. 9 with the rod lock actuating lever moved to the unlocked position.
FIG.13 shows a cross-section view of the rod lock of FIG. 6 taken along line 13-13, with rod 72 omitted for clarity.
FIG. 14 shows an enlarged view of a jaw and fixed wedge of the rod lock of 10 FIG. 12.
FIG. 15 shows an enlarged view of a jaw and fixed wedge of the rod lock of FIG. 9.
FIG. 16 shows a perspective view of a jaw 210, with its rod-contacting face 219 positioned downward.

The invention is directed to a parking brake for a vehicle. The invention is intended primarily for use on railway cars, but may also be used on other types of vehicles. The invention includes redundant hydraulic and mechanical locking arrangements for holding the railway car brakes in the activated position. An 20 installation view of the parking brake system is illustrated in FIG.2, as viewed looking down through the floor of a railway car 50. FIG. 3 is an elevation view of the installation of FIG.2, and FIG.4 is a schematic of the parking brake system of FIGS.

2 and 3.
As illustrated in FIGS. 2 and 3 the overall braking system for rail car 50 25 includes a brake lever 52 and a service brake cylinder 54 which function similarly to the service brake cylinder 22 and brake lever 24 as set forth above in the description of the prior art in FIG. 1. However, in FIGS. 2 and 3, brake lever 52 is shown mounted parallel to, and under the floor 55 of rail car 50, in a horizontal disposition, rather than perpendicular to, and above the floor in a vertical disposition, as shown 30 in the prior art illustration of FIG 1. In addition, brake linkage 56 in FIG. 2 is connected to the opposite end of brake lever 52, and the pivot point 58 is located in the center of brake lever 52 rather than on one end. It will be apparent, however, that the parking brake system of the present invention may also be incorporated in the prior art braking configuration of FIG.1, or in other brake system configurations, and that the particular configuration shown is for purposes of describing the preferred embodiment, and not intended to limit the invention to use with a particular existing 5 brake system configuration.
In order to apply the service brakes of rail car 50, service brake cylinder rod 60 is extended by pneumatic pressure introduced within service brake cylinder 62.
This causes brake lever 52 to move in the direction of arrow 62, which pulls on brake linkage 56 in the direction of arrow 63, thereby applying brakes 64, as illustrated in 10 FIG. 4. The service brake system can be used to hold the brakes 64 in an applied position when railway car 50 is parked for a short period of time. However, overlonger periods of time, pressure in the pneumatic system might be lost, which would result in the brakes being released. Consequently, a separate parking brake system is required when rail car 50 is to be parked for longer periods.
As illustrated in FIGS. 2, 3, and 4, the parking brake system of the present invention includes a hydraulic portion that incorporates a hydraulic cylinder 70 which has a movable piston 71 located therein. A cylinder rod 72 is connected to piston 71 and extends out one end of cylinder 70. Rod 72 is axially extendable and retractable by movement of piston 71 within cylinder 70, and rod 72 has a free end connection 20 point 74 which is connected to brake lever 52. A rod lock 76, having a function which will be described below, is mounted on a first end 78 of cylinder 70 and held in place by four long screws 80. A bellows-type sleeve 82 is mounted over the exterior of rod 72 to prevent foreign matter from contaminating rod lock 76 or rod 72. A second end 84 of cylinder 70 is secured to an end cap 85. End cap 85 is pivotally attached to a 25 mounting bracket 86 by a clevis 87 and pin 88. Clevis 87 fits between two plates 89, and is held in place by pin 88 so that end cap 85 is able to pivot about pin 88, but is restrained from lateral movement by plates 89. Mounting bracket 86 is bolted to a cylinder support bracket 90 which is attached to a structural member 92 on the underside of rail car 50. The pivotal mounting of end cap 85 enables cylinder 70 to 30 pivot and thereby remain tangential to the radius of brake lever 52 as brake lever 52 moves back and forth. As a result, rod 72 is always in line with connection point 74, and there is no risk of bending rod 72. From the above-described arrangement it will . .

be apparent that cylinder rod 72 is in mechanical communication with brakes 64 through brake lever 52 and brake linkage 56, and that by delivering fluid to cylinder 70, piston 71 and rod 72 may be moved to apply brakes 64.
To accomplish this, a hydraulic hand pump 100 is provided for delivering fluid 5 to cylinder 70 through a hydraulic hose 102 for pressurizing cylinder 70. As illustrated in FIG. 4, a hydraulic fluid reservoir 104 is in fluid communication with pump 100 and also directly with cylinder 70 through a control valve 106. Controlvalve 106 is included for controlling the fluid flow into or out of cylinder 70. Control valve 106 includes a control lever 107 for moving control valve 106 between an open 10 position and a closed position. When valve 106 is in the open position, fluid is free to flow between reservoir 104 and cylinder 70. However, when valve 106 is closed, fluid is unable to flow out of cylinder 70, and, as a result, rod 72 is locked from movement in one direction. Fluid may still be added to cylinder 70 when valve 106 is in the closed position by actuation of hand pump 100, so that rod 72 may still be 15 extended. Alternatively, if service brake cylinder 54 is activated to apply brakes 64 when control valve 106 is closed, fluid is also free to flow to cylinder 70 through check valves which will be described below. In this case, brakes 64 can still beapplied, so that the parking brake system will not prevent application of the service brakes.
Control valve 106 is left open during normal operation of rail car 50. When the service brake system is activated to apply and release the brakes 64 during operation of rail car 50, brake lever 52 moves back and forth. This also moves cylinder rod 72 and piston 71. As the service brakes are applied, rod 72 moves outward and piston 71 creates a suction which draws additional hydraulic fluid into cylinder 70 from reservoir 104 through control valve 106. When the service brakes are released, rod 72 is forced back into cylinder 70, and piston 71 forces hydraulic fluid out of cylinder 70, through control valve 106, and back into reservoir 104.
However, when it is desired to apply the parking brake, control valve 106 is moved to the closed position, as illustrated in FIG. 4. In this position, fluid is no longer free to flow between reservoir 106 and cylinder 70. Instead, cylinder 70 is essentially locked in place against retraction of rod 72. It may be seen, however, that because of the valve arrangement of FIG. 4, rod 72 and piston 71 can still be , extended outward, since additional fluid can feed in through a first check valve 108, pump 100, and a second check valve 110.
Thus, to apply brakes 64 as a parking brake, a handle 114 on hand pump 100 is pumped by a worker to draw fluid from reservoir 104, through first check valve 108, 5 into pump 100, through second check valve 110, and into cylinder 70. As pressure in cylinder 70 increases, piston 71 and rod 72 push brake lever 52 in the direction of arrow 62 to apply brakes 64. Brake lever 52 is prevented from moving back because of the fluid pressure in cylinder 70. A pop-up indicator or pressure gauge 116 is provided to indicate to the worker when sufficient pressure is present in cylinder 70 10 for the brakes to be fully applied. This pressure is approximately 850 psi in the preferred embodiment, but this pressure is dependent on the particular installation configuration. A pressure relief valve 112 is provided to protect the system from damage due to extreme pressures.
In addition, while it is not desirable to operate rail car 50 when control valve106 is in the closed position, the parking brake system of the present invention will not prevent operation of the service brakes even when control valve 106 is in the closed position. Because of the system valve arrangement, which includes check valves 108,110 and control valve 106, rod 72 is still able to be extended. Activation of service brake cylinder 54 will force brake lever 52 forward, thereby creating a suction in cylinder 70 if control valve 106 is closed when activation occurs. This suction will draw fluid from reservoir 104, through check valves 108,110, pump 100, and into cylinder 70, so that rod 72 is able to extend.
In addition, it might be noted that the hydraulic system is essentially a closedsystem, with an air bubble located in reservoir 104 which contracts and expands as fluid moves in and out of reservoir 104. Reservoir 104 also includes reservoir check valves 118 and 120, and an air filter 122, as illustrated in FIG. 4. Check valves 118 and 120 allow air to pass into and out of reservoir 104 should the pressure in the air bubble become too large or too small. Filter 122 filters any air which enters reservoir 104 to ensure that foreign matter does not contaminate the hydraulic fluid.
It will also be apparent that the hydraulic system of the present invention could function in certain modes as a pneumatic system. For example, a pneumatic cylinder may be substituted for hydraulic cylinder 70, and an pneumatic pump may be substituted for hand pump 100. Control valve 106 would still operate in the same way as described above, but a pneumatic system would have certain disadvantages because of the greater compressibility of gas relative to fluid. For example, considerably more time and energy may be required to pump sufficient air pressure 5 to the cylinder for applying the brakes. However, if the disadvantages of using pneumatics are not a concern for a particular application, then pneumatic components may be substituted for the hydraulic ones.
Thus, it may be seen that the hydraulic portion of the parking brake system of the present invention can activate brakes 64 of railway car 50. The hydraulic10 portion further acts as a hydraulic lock for holding brakes 64 in the applied position.
The hydraulic system is self-adjusting to compensate for any wear which occurs in the brake system, since rod 72 is extended under pressure as far as possible each time the system is implemented. Even after the parking brake has been fully applied, if an outside source acts on brake lever 52, such as for example, by activation of the 15 service brake pneumatic cylinder 54, then rod 72 will be able to extend further, but will not retract.
Furthermore, the system does not require as much physical strength to apply as the prior art system. For example, in the preferred embodiment, handpump 100 requires up to approximately 60 pounds of force for cycling handle 114, whereas the 20 prior art handwheel system of FIG. 1 required that up to 125 pounds of force be applied to tighten handwheel 30. Under the present invention a worker must merely cycle pump handle 114 until pop-up indicator or pressure gauge 116 indicates that sufficient pressure is reached, which assures the operator that the parking brake has been properly set. The hydraulic portion of the parking brake system is released by 25 moving control valve 106 from the closed position to the open position, which allows the hydraulic fluid to flow from cylinder 70 back to reservoir 104. Thus, the present invention provides an easily operated and reliable parking brake system.
However, hydraulic systems may sometimes be subject to leakage. Thus, it is possible that a fluid leak could develop in the hydraulic portion of the system so 30 that hydraulic pressure is lost. Under such a scenario, the rail car brakes would be released, and the rail car would be without a parking brake. To protect against such an occurrence, a redundant mechanical lock portion is provided for the parking brake system.
The mechanical lock portion of the parking brake system includes rod lock 76 which is illustrated in greater detail in FIGS. 5-16. FIG. 5 shows a side view of rod 5 lock 76, as enlarged from the view of FIG. 3. Rod lock 76 includes a box-like housing 150 having openings 152 and 154 through which rod 72 passes. Rod 72 has transverse serrations or teeth 156 formed along at least the portion of its length which moves through rod lock 76. Teeth 156 are formed transversely to the major axis 73 of rod 72, and on two opposed sides of rod 72, for engaging with rod lock 76 10 as will be described in detail below. In addition, while rod 72 is shown only in cross section in FIGS. 7-12 and 14-15, and omitted from FIG. 13 for explanation and clarity, it should be understood that the preferred embodiment of rod 72 includes rounded upper and lower flanges 159, as illustrated in FIGS. 7 and 8. Upper and lower flanges 159 allow rod 72 to slide more easily on bearing surfaces, and the like, 15 both within rod lock 76 and externally thereof.
Housing 150 includes mounting supports 157 which have threaded holes for receiving long screws 80 for mounting rod lock 10 on a linear actuator, such as cylinder 70. Housing 150 may be formed by casting, machining, or other techniques, and is preferably formed of two halves held together at the corners by cap screws 158, as illustrated in FIG. 7, for forming a box-like enclosure.
Rod lock 76 includes an actuation lever 160. Lever 160 is movable between an actuated or locked position (shown in FIG.5) and a released or unlocked position, as illustrated at 160' in FIG. 5. Lever 160 is generally U-shaped, as illustrated in FIGS. 7 and 8, and is connected to housing 150 at lever pivot points 162. A pair of links 164 are connected to lever 160 at a link pivot point 166 on either side ofhousing 150, and each link 164 is connected to a drive pin 168 on its free end. Drive pins 168 are movable back and forth within slots 170, so that as lever 160 is moved from the locked position to the unlocked position 160', drive pins 168 move to the right in slots 170 according to the orientation shown in FIG. 5.
As illustrated in FIGS.9-13, drive pins 168 are threaded into a drive plate 180 located within housing 150. Drive plate 180 is a generally rectangular plate having its major plane perpendicular to the axis 73 of rod 72. Drive plate 180 includes a pair , ~ . . .

of raised lugs 181 on one side to give sufficient thickness for attachment of drive pins 168. Drive plate 180 has a large central opening 182 for receiving a journal bearing 184 in a sliding fashion, so that drive plate 180 may be freely moved back and forth on journal bearing 184 along the axis of rod 72. Journal bearing 184 is pressed 5 within opening 154 in housing 150, and the inner lumen of journal bearing 184 forms a sliding contact with the rounded upper and lower flanges 159 of rod 72.
Drive plate 180 also includes four screw holes 188 for receiving drive-spring-supporting screws 190. The shanks of drive-spring-supporting screws 190 are of smallerdiameterthan holes 188. As a result, drive-spring-supporting screws 190 are 10 free to move axially in holes 188, but are retained by screw heads 192. Drive-spring-supporting screws 190 pass through drive plate 180, and are threaded into a retainer plate 196. A drive spring 200 is mounted on the shank of each drive-spring-supporting screw 190, and is sandwiched between drive plate 180 and retainer plate 196. Each of the four drive springs 200 is a compression spring which exerts a 15 spring force on retainer plate 196 when drive plate 180 is moved toward retainer plate 196 by moving lever 160 from the unlocked to the locked position.
Retainer plate 196 is a generally rectangular plate having a large central opening 197 which allows passage of rod 72 therethrough. Retainer plate 196 has four rectangular pin lugs 202 extending perpendicularly from the side opposite to 20 drive springs 200. Pin lugs 202 have holes therein for receiving two jaw-retaining pins 204 in a lateral disposition. Jaw-retaining pins 204 are mounted with their axes transverse to the axis 73 of rod 72, with one jaw-retaining pin 204 being located directly above, and parallel to, the other jaw-retaining pin 204. Jaw-retaining pins 204 are fixed in place on pin lugs 202 by roll pins 206 or other suitable fastening 25 means.
A pair of locking jaws 210 are slideably suspended on retaining pins 204 by upperandlowerjawlugs212. Jaws210mayslidelaterallyon jaw-retainingpins204 toward or away from rod 72. Each jaw 210 is generally wedge shaped, having an inclined surface 214 which is located adjacent to a fixed wedge 216. Fixed wedges 30 216 are mounted to housing 150, and each fixed wedge has an inclined surface 218 which inclines toward the axis 73 of rod 72. It may be seen that as jaws 210 are moved toward fixed wedges 216, jaws 210 are forced inward toward rod 72 by the action of the inclined surfaces 218.
FIG.16 shows a perspective view of a jaw 210. Jaw 210 includes upper and lower bearing ears 222, which contact inclined surface 218 of fixed wedge 216. As 5 illustrated in FIGS.14 and 15, bearing ears 222 contact inclined surface 218 before inclined surface 214 of jaw 210. Accordingly, as jaw 210 is moved toward fixed wedge 216, bearing ears 222 force jaw 210 inward at the point of contact 223 with inclined surface 218. This creates a force normal to the axis 73 of rod 72 almost directly in line with jaw-retaining pins 204. This reduces torsional forces which would 10 otherwise be in effect if the point of contact were near the tip of jaw 210, and prevents bending of jaw retaining pins 204 or jaw lugs 212. However, it may be seen from FIG. 15 that when rod lock 76 is activated, inclined surface 214 of jaw 210bears against inclined surface 218 of fixed wedges 216.
Each jaw 210 has a rod-contacting face 219 on the side of jaw 210 which faces rod 72 when jaw 210 is installed in housing 150. Rod-contacting face 219 includes a plurality of teeth 220 transversely disposed relative to the axis 73 of rod 72. Teeth 220 on jaws 210 are generally a mirror image of the teeth 156 on rod 72 so that when jaws 210 are pressed against rod 72, jaw teeth 220 closely interfit with rod teeth 156 to provide a frictional engagement and a locking action.
Teeth 156, 220 have a double-inclined surface profile, so that the faces on both sides of each tooth are inclined relative to the axis 73 of rod 72 and meet at a peak. This provides an advantage over most prior art rod-locking devices, such as the Case et al. patent described above, in which the teeth are inclined on only one face, while the other face is at a right angle to the axis of the rod. The double-inclined faces on teeth 156, 220 create what might be characterized as a frictional engagement rather than a positive stop, and thereby reduce the likelihood of accidental engagement between jaws 210 and rod 72, which may not be the case in devices in which the teeth mating surfaces are at right angles and have a positive stop. Furthermore, it may be seen that even if teeth 156,220 were eliminated, then jaws 210 would still provide a gripping action on rod 72, the effectiveness of which would be determined by the coefficient of friction between rod-contacting face 219 and rod 72.

As illustrated in FIGS.14 and 15, each tooth 156 has a first tooth surface 224 and a second tooth surface 225, each of which is in an inclined disposition relative to the axis 73 of rod 72. First tooth surface 224 and second tooth surface 225 meet at a peak for forming each tooth 156. First tooth surface 224 is the load-bearing 5 surface for each tooth, such that when rod lock 76 is in the activated condition, with jaws 210 gripping rod 72, and a load is attempting to move rod 72 toward fixed wedges 216 (i.e., toward the left in the drawing figures), then first tooth surface 224 bears the load and transfers the load to teeth 220 on jaws 210. Jaws 210 transfer the load to fixed wedges 216, while the load also forces jaws 210 toward fixed 10 wedges 216, and as a result, inclined surface 218 forces jaws 210 more tightly against rod 72. Second tooth surface 225 presses against jaws 210 when a releaseload is applied to rod 72 for moving rod 72 away from fixed wedges 216. It may be seen that jaw teeth 220 are the reverse of rod teeth 156 and preferably have surfaces with matching angles of inclination to ensure intermeshing.
For releasing jaws 210 from rod 72, upper and lower release springs 226 are mounted on upper and lower jaw-retaining pins 204. Release springs 226 also ensure that jaws 210 do not engage with rod 72 until rod lock 76 is activated. It may be seen that release springs 226 are compression springs located between jaws 210 and that release springs 226 apply a force to move jaws 210 away from each other, 20 and also away from rod 72.
In addition, a safety spring 230 is provided within each fixed wedge 216, and mounted on a stud 232 which is threaded into fixed wedge 216, as illustrated in FIG.
10. Safety springs 230 are compression springs which bear against retainer plate196 for protecting against accidental engagement of jaws 210 in the event of a 25 mechanical failure of, for example pins 168. It may be seen from FIGS. 8 and 10 that fixed wedges 216 have a hollowed-out area 233 to accommodate safety springs230. Jaws 210 have a matching hollowed-out area 234. The spring constants for safety springs 230 and release springs 226 are controlled and balanced so that they combine to create a spring force on retainer plate 196 which is less than the spring 30 load created by drive springs 200 when the rod lock 76 is in the locked condition.
In operation, when it is desired to apply the locking action of rod lock 76 to rod 72, lever 160 is moved from the unlocked to the locked position. Lever 160 pulls links 164, drive pins 168, and drive plate 180 toward fixed wedges 216. Drive plate 180 pushes drive springs 200 against retainer plate 196, which forces retainer plate 196 and jaws 210 toward fixed wedges 216. Jaws 210 move toward fixed wedges 216, and are forced inward toward rod 72 due to the interaction of inclined surface 5 218 and bearing ears 222.
When lever 160 reaches the locked position, drive plate 180 is in its full-forward position as shown in FIGS. 9,10,11, and 13. In this position, retainer plate 196 and jaws 210 are under load from drive springs 200 to move toward fixed wedges 216. The load forces jaws 210 into engagement with rod 72 so that teeth 10 220 on jaws 210 intermesh with teeth 156 on rod 72. This placement locks rod 72 in a fixed position so that attempted motion of rod 72 in the direction of fixed wedges 216 only forces jaws 210 more strongly in the direction of fixed wedges 216. Theinteraction of the inclined surfaces 214 of jaws 210 against the inclined surfaces 218 of fixed wedges 216 increases the inward gripping action of jaws 210. In other 15 words, in the above-described position, rod 72 may not be moved toward fixed wedges 216 (i.e., toward cylinder 70) because a force in that direction will only increase the pressure exerted by jaws 210 on rod 72, thereby increasing the engagement and frictional gripping forces between jaws 210 and rod 72.
However, because retainer plate 196 and jaws 210 are forced forward by a 20 spring force, rather than by a fixed load, rod 72 may be moved in the direction away from fixed wedges 216 (i.e., extended further outward from cylinder 70) as shown by arrow 240 on FIG.11. If a sufficient force is applied to rod 72 in the direction away from fixed wedges 216, either by cylinder 70, or by a force pulling on the end of rod 72, then wedges 210 will be forced outward, and rod 72 will move away from fixed25 wedges 216. Such a force must be sufficient to overcome the net spring load of drive springs 200. This net spring load to be overcome is approximately equal to the total spring load exerted by drive springs 200 on retainer plate 196 minus the spring force exerted by the combination of safety springs 230 and release springs 226, although frictional forces will increase the net spring load slightly.
To reduce the frictional forces the angle A of first tooth surface 224 is preferably less than the angle B of inclined surface 218 on fixed wedges 216, asillustrated in FIG. 15. For example, in the preferred embodiment, the angle of inclination of angle A is 30~ relative to the axis 73 of rod 72, while the angle of inclination of angle B is 31 ~ relative to the axis 73 of rod 72. Having angle B greater than angle A reduces the frictional forces for enabling jaws 210 to be released more easily when moving away from fixed wedges 216.
As illustrated in FIG.11, as rod 72 is forced away from fixed wedges 216, jaws 210 and retainer plate 196 are also forced away from fixed wedges 216, although drive plate 180 does not move. As jaws 210 move away from fixed wedges 216, they will move outward and away from rod 72. This outward movement is due to both the compressive forces of release springs 226 and also due to the ramped 10 profiles of teeth 156, 220. As long as a sufficient force is moving rod 72 in the direction away from fixed wedges 216, jaws 210 will continue to allow rod 72 to extend. However, when the extension forces become insufficient, drive springs 200 will again force teeth 220 on jaws 210 into engagement with teeth 156 on rod 72,thereby returning rod 72 to the fully locked position, so that movement of rod 72 in 15 the direction of fixed wedges 216 will still be prevented. Rod 72, in effect, slides along the tooth profile of jaws 210 as rod 72 moves outward, while the spring force exerted by drive springs 200 continuously forces jaws 210 back into engagement with rod 72. Thus, when activated, rod lock 76 allows rod 72 to essentially "ratchet"
in one direction, while preventing motion in the opposite direction. There may be a 20 slight backlash in the opposite direction if teeth 156, 220 are misaligned. The distance of the backlash depends on the amount of misalignment and the tooth size and geometry. In the preferred embodiment a maximum backlash of 3/16 inch is permitted.
An additional benefit of the spring-loaded feature created by drive springs 200 25 is that they create a consistent operator input force when rod lock 76 is moved to the locked position. Because rod 72 may stop at any of an infinite number of positions along its stroke, it is possible that rod teeth 156 may not initially mesh precisely with jaw teeth 220. When this occurs, jaws 210 will remain disengaged from rod 72, and inward thereof, in the position shown in FIG.11. However, although jaws 210 stop30 short of engagement, they are still under load from drive springs 200 because drive plate 180 will move into the fully-locked position despite the misalignment between rod teeth 156 and jaw teeth 220. The instant that rod 72 starts to move backwards, .

drive springs 200 force jaws 210 to snap into the fully-locked-and-engaged position as shown in FIGS. 9 and 10. Thus, if the jaw teeth 220 are not initially aligned with the rod teeth 156, the lock may still be set by a worker, and drive springs 200 will automatically force jaws 210 into place in the locked position upon slight movement 5 of rod 72 in either direction.
Rod lock 76 is returned to the unlocked position by moving lever 160 back the unlocked position, which moves drive plate 180 back to the unlocked position, asshown in FIG.12. (FIG. 8 also shows rod lock 76 in the unlocked position) Duringthis action, drive plate 180 moves back along journal bearing 184, and the heads 192 10 of drive screws 190 bottom out on drive plate 180 and pull retainer plate 196 back along with them. This also pulls jaws 210 away from rod 72, and release springs 226 ensure that jaws 210 fully disengage from rod 72.
Safety springs 230 also ensure that jaws 210 remain disengaged from rod 72 in the event of mechanical failure while rod lock 76 is in the unlocked position. For 15 example, if a foreign object strikes lever 160, breaking lever 160 free, then drive plate 180 and retainer plate 196 may be free to move about within housing 150. Under such a scenario, safety springs 230 will hold jaws 210 away from fixed wedges 216, thereby preventing accidental engagement of jaws 210 with rod 72, which could lead to brake lockup. The double-incline tooth profile of teeth 156,220 also helps ensure 20 against accidental lockup in such a situation since there are no right-angled surfaces to engage between the teeth 156, 220.
Since rod lock 76 is located on the underside of rail car 50, it is preferable to be able to control rod lock 76 remotely without having a worker crawl under car 50.
Referring back to FIGS. 2 and 3, it may be seen that rod lock 76 may be controlled 25 remotely via a push-pull cable controller 250. Cable controller 250 includes a knob 252 which is connected to a cable 254 located within a cable casing 256. Cable casing 256 is anchored at one end to cable controller 250, and cable casing 256 may be anchored at its other end to an anchor plate 270 which depends from rod lock housing 150. Anchor plate 270 may be formed unitary with rod lock housing 150, or 30 may be attached by other means. Cable 254 extends beyond anchor plate 270 andis connected to lever 160. Upon moving knob 252, cable 254 acts to move rod locklever 160. Thus, when knob 252 is pushed in, cable 254 moves rod lock lever 160 to the unlocked position. Likewise, when knob 252 is pulled outward, cable 254 moves rod lock lever 160 to the locked position. Knob 252 is held in position byfriction, positive lock, or other means to prevent accidental locking or unlocking of rod lock 76. Alternatively, hydraulic, pneumatic, or electric actuators may also be used 5 to move lever 160 between the locked and unlocked position. For example, a small hydraulic cylinder, a solenoid, or an electric motor could be used to actuate lever 160. Or, alternatively, a mechanical linkage may be connected to lever 160, or directly to drive pins 168 for actuating rod lock 76. Or, still alternatively, a single actuator, such as any of the above-listed, might be used to simultaneously activate 10 both the rod lock 76 and control valve 106 of the hydraulic portion of the system, thereby activating both portions of the system.
In addition, while the rod lock 76 of the present invention is particularly suited for use as the mechanical lock portion of the parking brake system of the present invention, rod lock 76 may also be used for a variety of other applications in which 15 it is desirable to prevent movement of a movable rod. Thus, the rod lock may be applied to a number of additional locking applications which incorporate hydraulic or pneumatic cylinders and other types of linear actuators, such as holding outriggers on equipment in a set position, holding an automatic door in set position, or any other application in which it is advantageous to permit linear movement of a rod in one 20 direction while preventing linear movement in the opposite direction. Accordingly, it will be apparent that a number of additional applications are available for rod lock 76 of the subject invention, several of which are set forth in the co-pending patent application entitled "Lock for Preventing Movement of a Rod"; U.S. Application No.
08/948,262; filed on October 9, 1997; by inventors David E. Pettengill, Jr. and 25 Anthony G. Gurley; assigned to the same assignee as herein; attorney docket no.
GURL-US1; and the disclosure of which is incorporated herein by reference.
From the foregoing, it may be seen that the parking brake system of the present invention has a number of advantages over the prior art. The present invention provides a means to easily and quickly apply the parking brake for a 30 vehicle such as a railway car. In a typical-use scenario, a train may comprise a locomotive and a plurality of rail cars 50 having the parking brake system of the present invention installed. The train is brought into a yard or other location in which the rail cars are to be parked for a period of time. Prior to departure of the locomotive, the train goes through a full service reduction in which all of the pneumatic service brake cylinders 54 on all the rail cars 50 are activated to apply the brakes 64. Service brake cylinders 54 are left pressurized in the activated position 5 following departure of the locomotive. Since the service brake cylinders 54 will lose pressure over a period of time, the operators apply the parking brake of the present invention on a certain percentage of the rail cars 50 (usually 10% or more) to prevent the train from being without brakes.
To apply the parking brake, control valve 106 is moved from the open position 10 to the closed position. Rod lock 76 may be activated before this, or after cylinder 70 has been fully pressurized, or at any time in between. Since control valve 106 was in the open position upon activation of service brake cylinder 54, a full column of fluid was drawn into cylinder 70, and closure of control valve 106 locks the fluid within cylinder 70. Following closure of control valve 106 and the optional activation of rod lock 76, additional fluid is pumped into cylinder 70 using hand pump 100 until apredetermined pressure is reached (approximately 850 psi in the preferred embodiment). When this pressure is reached the operator will know that the brakes are properly applied, and the operator will activate rod lock 76 if it has not already been activated.
Because a full fluid column was drawn into cylinder 70 by operation of service brake cylinder 54, only a small number of pumps on hand pump 100 are required (usually 2-4 pumps) to reach the specified pressure, even though the hand pump has a very small displacement. In addition, because of the valve arrangement of the hydraulic system, even if control valve 106 was unintentionally in the closed position 25 prior to activation of the service brake cylinder 54, an almost full column of fluid will still be drawn into cylinder 70 through check valves 108,110.
In a second typical-use scenario known as spotting, a single rail car 50 might be left in a particular location for loading or the like. In this case it may not have been practical to apply the service brake cylinder 54 to aid in setting the parking 30 brake. To set the parking brake, control valve 106 is moved to the closed position, and rod lock 76 is activated (or, alternatively, activated later). Next, pump 100 is pumped until the specified pressure is reached. Because service brake cylinder 54 was not used to pre-set the brakes, brake lever 52 must be moved the entire distance required to set the brakes solely by cylinder 70. This requires considerably more cycling of pump handle 114 on pump 100 (typically 12 pumps), to fully applybrakes 64 at the specified pressure. However, as the parking brake is only being5 applied to a single car, this is not thought to be particularly burdensome to the operator.
To release the parking brake in either of the above-scenarios, the operator must merely go to a car 50, deactivate rod lock 76, and move control valve 106 from the closed position to the open position. This will allow fluid to flow from cylinder 70 10 back to reservoir 104 as brakes 64 return to the released position under spring force of service cylinder 54 or the brake system.
Thus, it will be apparent that the present invention includes both a hydraulic portion which can apply and hold the brakes in the applied position, and an independent mechanical portion which also holds the brakes in the applied position.
15 If hydraulic pressure in cylinder 70 is lost, rod lock 76 will still hold brakes 64 in the applied position. Similarly, if rod lock 76 fails or is accidentally released, then brakes 64 also will not be released because cylinder 70 will hold brakes 64 in the applied position. The mechanical portion and the hydraulic portion act independently of each other to prevent rod 72 from being moved to release brakes 64. Thus, the present20 invention provides redundant safety features for ensuring that the parking brake does not fail, by providing both a hydraulic lock and a mechanical lock.
In addition, while preferred embodiments have been described herein, it will be recognized that a variety of changes and modifications may be made without departing from the spirit of the subject invention, the scope of which is set forth in the 25 following claims.

Claims (27)

1. A parking brake apparatus for holding the brakes of a vehicle in an activated position, said apparatus comprising:
a hydraulic fluid cylinder, said cylinder including a rod, said rod being extendable from said cylinder for holding the vehicle brakes in the activated position;
a reservoir containing hydraulic fluid in fluid communication with said cylinder whereby extension of said rod corresponds to the delivery of fluid from said reservoir to said cylinder;
a control valve for controlling the flow of said fluid from said reservoir to said cylinder, whereby when said control valve is closed, said rod is capable of further extension, but is locked against retraction by said fluid in said cylinder; and a mechanical lock associated with said rod, such that when said lock is activated, said rod is capable of further extension, while being prevented from retraction.

2. The system of claim 1 further including a hydraulic hand pump, said hand pump being in fluid communication between said reservoir and said cylinder,whereby said pump may be used to increase the fluid pressure in said cylinder toprevent retraction of said rod or to cause further extension thereof.

3. The system of claim 1 in which said mechanical lock includes a pair of opposed, generally wedge-shaped jaws, said jaws being movable by a spring load, and a pair of fixed wedges, said jaws being in sliding contact with said fixed wedges, whereby said spring load forces said jaws against said fixed wedges so that saidjaws slide into a gripping engagement with said rod whereby retraction of said rod is prevented while extension of said rod is possible by overcoming said spring load.

4. The device of claim 3 in which said rod includes a plurality of teeth formed along at least a portion of its length, and said jaws include a plurality of teeth formed along their sides which come into contact with said rod, whereby said teeth on said jaws intermesh with said teeth on said rod for forming a gripping engagement.

5. The device of claim 4 further including a pair of release springs located between said jaws, said release springs being in compression for forcing said jaws away from said rod.

6. The device of claim 5 in which said spring load is created by at least one drive spring in compression, said drive spring being movable between a locked position and an unlocked position whereby when said drive spring is in said locked position, said spring force from said drive spring is greater than said spring force from said release springs so that said jaws are forced toward said fixed wedges and into a gripping engagement with said rod.

7. The device of claim 6 further including a lever for moving said at least one drive spring between said unlocked and said locked position, and further including a push-pull cable for remotely activating said lever for moving said drive spring between said unlocked and locked positions.

8. A parking brake system for applying and locking the brakes of a railway car, said system comprising:
a hydraulic portion, said hydraulic portion including a cylinder for receiving fluid from a reservoir, said cylinder having a rod which is movable by said fluid, said rod being in mechanical communication with the brakes of the railway car, said rod being movable in a first direction for applying the brakes and in a second direction for releasing the brakes;
said hydraulic portion further including a control valve that may be activated for preventing fluid from exiting said cylinder, whereby when said control valve is activated, said rod is prevented from moving in said second direction; and a mechanical lock portion, said mechanical lock portion allowing said rod to be moved in said first direction for applying the brakes, but preventing said rod from being moved in said second direction, whereby said mechanical lock portion and said hydraulic portion act as backups to each other so that if one of said portions fails, the other portion will still hold the brakes in the applied position.

9. The system of claim 8 in which said hydraulic portion includes at least one check valve for allowing fluid to flow from said reservoir to said cylinder when said control valve is activated.

10. The system of claim 9 in which said mechanical lock portion includes:
a pair of opposed, generally wedge-shaped jaws, said jaws being movable by a spring load; and a pair of fixed wedges, said jaws being in sliding contact with said fixed wedges, whereby said spring load forces said jaws against said fixed wedges so that said jaws slide into a gripping engagement with said rod whereby axial movement of said rod in a first direction is prevented while axial movement of said rod in the opposite direction is possible by overcoming said spring load.

11. The system of claim 10 in which said rod includes a plurality of teeth formed along at least a portion of its length, and said jaws include a plurality of teeth formed along their sides which come into contact with said rod, whereby said teeth on said jaws intermesh with said teeth on said rod for forming a gripping engagement.

12. The system of claim 11 further including a pair of release springs located between said jaws, said release springs being in compression for forcing said jaws away from said rod.

13. The system of claim 12 in which said spring load is created by at least one drive spring in compression, said drive spring being movable between a locked position and an unlocked position whereby when said drive spring is in said locked position, said spring force from said drive spring is greater than said spring force from said release springs so that said jaws are forced toward said fixed wedges and into a gripping engagement with said rod.

14. The system of claim 8 further including a pump for delivering fluid under pressure from said reservoir to said cylinder.

15. A method of applying and holding the brakes of a vehicle as a parking brake, said method comprising:
providing a hydraulic portion, said hydraulic portion including a hydraulic cylinder having an extensible rod, said rod being in mechanical communication with the brakes of the vehicle for applying the brakes when said rod is extended, said cylinder being in fluid communication with a reservoir which delivers fluid to said cylinder during extension of said rod;
positioning a valve arrangement between said cylinder and said reservoir, said valve arrangement including a control valve;
providing a mechanical lock, said mechanical lock capable of allowing said rod to be extended while preventing said rod from being retracted; and delivering fluid to said cylinder during extension of said rod, whereby when said control valve is in a closed position, and said mechanical lock is in an activated position, fluid will be prevented from exiting said cylinder, such that said cylinder and said mechanical lock are capable of holding said rod in an extendedposition.

16. The method of claim 15 wherein said hydraulic portion includes a pump in fluid communication with said cylinder and said reservoir, said method further including the step of delivering fluid to said cylinder by said pump for extension of said rod.

17. The method of claim 16 further including the step of releasing said brakes by deactivating said mechanical lock, and opening said control valve to allow fluid to flow from said cylinder to said reservoir.

18. The method of claim 15 in which said mechanical lock includes:
a pair of opposed, generally wedge-shaped jaws, said jaws being movable by a spring load; and a pair of fixed wedges, said jaws being in sliding contact with said fixed wedges, whereby said spring load forces said jaws against said fixed wedges so that said jaws slide into a gripping engagement with said rod whereby axial movement of said rod in a first direction is prevented while axial movement of said rod in the opposite direction is possible by overcoming said spring load.

19. The method of claim 18 in which said rod includes a plurality of teeth formed along at least a portion of its length, and said jaws include a plurality of teeth formed along their sides which come into contact with said rod, whereby said teeth on said jaws intermesh with said teeth on said rod for forming a gripping engagement.

20. The method of claim 15 in which said valve arrangement includes at least one check valve positioned between said reservoir and said cylinder.

21. A parking brake system for applying the brakes of a vehicle as a parking brake, said system comprising:
a pump for delivering fluid to said system;
a cylinder having a moveable piston located therein and an extensible rod attached to said piston, said cylinder being in fluid communication with said pump whereby delivery of fluid by said pump to said cylinder causes movement of said piston for extension of said rod, said rod being in mechanical communication with the brakes of the vehicle so that extension of said rod applies the brakes; and a mechanical lock associated with said rod, said mechanical lock, when activated, being capable of gripping said rod, so that said rod may extend outward to apply the brakes, but may not retract because of the gripping action of said mechanical lock.

22. The system of claim 21 in which said mechanical lock portion includes:
a pair of opposed, generally wedge-shaped jaws, said jaws being movable by a spring load; and a pair of fixed wedges, said jaws being in sliding contact with said fixed wedges, whereby said spring load forces said jaws against said fixed wedges so that said jaws slide into a gripping engagement with said rod whereby axial movement of said rod in a first direction is prevented while axial movement of said rod in the opposite direction is possible by overcoming said spring load.

23. The system of claim 22 in which said rod includes a plurality of teeth formed along at least a portion of its length, and said jaws include a plurality of teeth formed along their sides which come into contact with said rod, whereby said teeth on said jaws intermesh with said teeth on said rod for forming a gripping engagement.

24. The system of claim 23 further including a pair of release springs located between said jaws, said release springs being in compression for forcing said jaws away from said rod.

25. The system of claim 24 in which said spring load is created by at least one drive spring in compression, said drive spring being movable between a locked position and an unlocked position whereby when said drive spring is in said locked position, said spring force from said drive spring is greater than said spring force from said release springs so that said jaws are forced toward said fixed wedges and into a gripping engagement with said rod.

26. The device of claim 23 in which each of said teeth on said rod and said jaws are formed so that each tooth has a first face and a second face which meet at a peak, each said first face and second face being in an inclined disposition relative to the axis of said rod.

27. The device of claim 23 in which said first face of said teeth is positioned to bear against said jaws when said rod is moved in the direction of said fixed wedges, each of said fixed wedges having an inclined surface, wherein said first face has an angle of inclination relative to the axis of said rod which is less than the angle of inclination of said inclined surface of said fixed wedges relative to the axis of said rod.