Field of the Invention This invention relates to the field of rail brakes and in particular to an improved coil spring rail brake which provides, among other things, for improved access to the spring assembly and to the brake shoes for ease of maintenance and repair.

Background of the Invention

In the prior art, applicant is aware of various designs of rail brakes. In particular, applicant is aware of the following United States Patents:

Patent No. 581,270 which issued April 27, 1897, to Davis for a Rail Brake discloses the use of coil springs secured to lever bars so as to hold the lever bars, and the brake shoes mounted thereunder, away from the track rails.

Patent No. 1,790,202 which issued to Down on January 27, 1 31, for a Magnetic Brake Device, discloses a magnetic brake shoe which is normally held suspended away from the rail and, upon energization, is attracted to the rail to act as a brake. A coil spring is disposed in a chamber and acts on a piston so as to normally maintain the brake shoe in a suspended position over the rail.

Patent no.3,878,925 which issued to Ignatoweicz in April 22, 1975, for a Mounting Device for Magnetic Rail Brakes, discloses reducing the air pressure in conventional bellows so as to compress the bellows downwardly until stopped by a spring buffer at a low position wherein the brake magnet may be energized so as to be attracted towards the rail thereby causing a further compression of the spring buffer. Correction of the vertical setting of the magnetic brake unit is accomplished by pressurizing the bellows so as to raise the magnetic unit to a high position. The height of the magnetic unit above the rail may then be adjusted.

Summary of the Invention

It is an object of the present invention to provide a rail brake in which at least one or more of the following characteristics are present: a) the rail brake brake shoes may be replaced without removing the whole rail brake assembly from the crane or other rail-mounted machine having the rail brake mounted thereon. b) the rail brake actuators may be removed for service without removing the rail brake assembly from the crane or other rail-mounted machine having the rail brake, both when the brake is applied or when the brake is released and the rail brake springs are caged; c) the springs, when caged, together with the top plate may be removed modularly from the rail brake enclosure without removing the enclosure from the crane or other rail-mounted machine.

The rail brake according to the present invention includes a rigid enclosure having an upper end and opposite base end rigidly mounted oppositely to the upper end. The upper end is adapted for mounting to the rail-mounted machine, for example under a crane, so as to dispose the base end of the enclosure over and adjacent the rail. A top plate is mounted underneath the upper end of the enclosure, spaced apart from and substantially parallel to the upper end of the enclosure so as to define a gap there-between. A spring carriage is mounted for vertical translation within the enclosure, beneath the top plate, between an elevated position and a lowered position. At least one spring is mounted between the spring carriage and the top plate so that the springs are compressed when the spring carriage is in its elevated position and decompressed when the spring carriage is in its lowered position. At least one brake shoe is mounted under the carriage so as to be oppositely disposed on the carriage relative to the springs.

At least one selectively actuable actuator is mounted between, so as to bear opposite ends thereof against, the spring carriage and the base end of the enclosure respectively. The actuators are actuable between extended and retracted positions. In the extended position, the spring carriage is in its elevated position and the brake shoes are correspondingly retracted upwardly. In the retracted position, the spring carriage is in its lowered position and the brake shoes are correspondingly lowered so as to be urged by the springs into frictional engagement against the rail.

The enclosure includes sides extending between the upper end and the base end. At least one of the sides is open for ease of removal of the spring carriage, the top plate, the springs and/or the actuators therethrough. The spring carriage may also include an elongate caging member, where the caging member has opposite first and second ends. The caging member is mounted to the spring carriage at the first end of the member and extends substantially parallel to the springs. The second end of the member is journalled upwardly through an aperture in the top plate, and is free to translate vertically in the gap as the spring carriage translates correspondingly within the enclosure so as to translate simultaneously and correspondingly therewith. The second end of the caging member protrudes into a spring-caging position in the gap when the spring carriage is in its elevated position. A selectively releasable lock locks the second end of the caging member in its spring-caging position whereby translation of the caging member and the spring carriage is immobilized. The lock may include a latch member in which case the caging member includes a latch receiver for releasably holding the latch member when caging member is in its spring-caging position. The brake shoes are removable when the spring carriage is in its elevated position.

In a preferred embodiment the spring carriage also includes bearing members corresponding to the location of the tops of the actuators so that the actuators bear against the bearing members. The bearing members may include a pair of substantially oppositely disposed bearing members extending orthogonally relative to the actuators. The actuators may be corresponding pair of actuators extending substantially parallel to the springs.

The carriage translates a brake set distance between the elevated and lowered positions, and the actuators actuate a corresponding actuation distance between their extended and retracted positions. The actuators also selectively elevate the spring carriage to an unlocking position which is further elevated above the carriage's elevated position so as to unload a spring force load applied to the latch member of the latch receiver. Once the spring force is unloaded the latch member is removable from the latch receiver. The latch member may include a fork, in which case the latch receiver includes a lip on the caging member. The lip may be a substantially annular lip. The lip may be formed by a collar on the caging member. The latch member may be elongate and mounted substantially horizontally for horizontal translation into engagement under the lip. In one embodiment, spacers define a vertical separation distance within the gap between the upper end of the enclosure and the top plate. The vertical separation distance is substantially equal to the translation distance of the spring carriage between it's lowered position and it's elevated position. The separation distance may be substantially equal to a translation distance of the spring carriage between it's lowered position and it's unlocking position when the caging members are further elevated to allow unlocking of the corresponding latches.

The springs may be a pair of helical coil springs and the caging members may be a pair of elongate shafts. The elongate shafts may be journalled through corresponding springs.

The brake shoes may be mounted under the carriage substantially equi-distant, when measured horizontally between the pair of springs so as to substantially evenly distribute a downward spring force of the springs to the brake shoes.

Brief Description of the Drawings

In the drawings forming part of this specification, like reference numerals denote corresponding parts in each view, and wherein:

Figure 1 a is, in partially cut-away side elevation view, one embodiment of the coil spring rail brake according to the present invention.

Figure lb is, in front elevation view, the rail brake of Figure la.

Figure lc is, in plan view, the rail brake of Figure la.

Figure 2a is, in partially cut-away side elevation view, the rail brake of Figure la with the pair of helical coil springs removed and showing the rail brake housing.

Figure 2b is, in front elevation view, the rail brake of Figure 2a.

Figure 2c is, in plan view, the rail brake of Figure 2a. Figure 3a is the rail brake of Figure lb mounted to a rail-mounted machine so as to be suspended over a rail, with the brake released.

Figure 3b is the rail brake of Figure 3a in the brake set position at nominal rail height.

Figure 3c is the rail brake of Figure 3b with the rail brake in a brake set position at a rail deviation of +2mm. Figure 3d is the rail brake of Figure 3c with the rail brake in a brake set position at a rail deviation of -2mm.

Figure 3e is the rail brake of Figure 3 a with the springs caged. Detailed Description of Embodiments of the Invention

The rail brake according to the present invention is mounted under a rail-mounted machine such as a crane 10, There exists a space between the crane and the rails in which a rigid enclosure is mounted. The top plate of the enclosure is bolted to the underside of the crane so as to position the bottom of the enclosure adjacent the rail to which the brake is to be applied. A modular spring and actuator mechanism is housed in the enclosure. The springs and/or actuators may be removed from the enclosure for servicing, as better described below, through an opening in the enclosure. In a preferred embodiment of the actuators are a pair of actuators mounted in the enclosure to act on the spring mechanism. The spring mechanism includes a pair of helical coil springs 12 which in one embodiment exert a nominal 470 kilo-newton downward force driving downwardly one or more brake shoes 14 mounted under the spring mechanism. In particular, brake shoes 14 mounted on shoe rods 16 are driven downwardly into frictional engagement against the upper surface of rails 18. Brake shoes 14 are mounted to shoe rods 16 by bolts 16a engaging through holes in metal clips 16b, thereby allowing worn brake shoes to be replaced without removing the enclosure or any part thereof from the crane once the brake shoes have been elevated above the rail.

Within the spring mechanism, coil springs 12 are maintained in spaced apart parallel alignment by rigid supports mounted to contain the tops and the bottoms of the springs and in particular by a spring holder 20 supporting the bottom of the springs and by a top plate assembly 22 supporting the tops of the springs. Spring holder 20 includes walls 20a formed to cup the bottoms of the springs 12 and vertically upstanding cylindrical caging members or guides 20b which extend upwardly within the cavity defined by walls 20a so mat, with springs 12 installed in spring holder 20, guides 20b extend upwardly journalled through the center of the helical coils of the springs. The top surfaces of guides 20b are adjacent the underside of top plate assembly 22 when the springs 12 are fully compressed as further described below. A center guide member 20c extends upwardly between the springs and acts as a stop against top plate assembly 22 to prevent over-compressing of the springs as over-compression of the springs may damage the springs. The top of center guide member 20 acts as a spacer in combination with the top plate to prevent this over-compression.

A caging pin 24 is rigidly mounted into the top ends of guides 20b so as to protrude vertically upwards therefrom. The shank 24a of pins 24 pass through corresponding apertures 22a formed in top plate assembly 22 so that as springs 12 are compressed or allowed to expand, caging pins 24 mounted in guides 20b are raised or lowered respectively relative top plate assembly 22.

Springs 12 and the supports for the springs provided by a spring carriage such as spring holder 20 are all mounted within a rigid enclosure 26. Enclosure 26 is mounted to the underside of the rail-mounted machinery, such as the underside of crane 10, in the space between the underside of the machine and the rail. Top plate assembly 22 is bolted to spacers 22b mounted underneath the upper plate 26a of enclosure 26. Enclosure 26 includes upper plate 26a, sidewalls or a supporting framework 26b (collectively referred to herein as walls), and a rigid base 26c supported rigidly underneath the upper plate 26a by the walls. The spring assembly which consists of the pair of springs 12, the spring holder 20, and the top plate assembly 22, is mounted within the enclosure 26 so that the spring assembly may be removed from an opening in the side of the enclosure, that is, through an opening in a wall of the enclosure, once the brake shoe assembly has been removed and the spring top plate assembly 22 unbolted from the spacers 22b under upper plate 26a by removing bolts 30.

A cavity or space 28 is maintained between top plate assembly 22 and the upper plate 26a of enclosure 26 by spacers 22b. Space 28 allows for vertical translation of caging pins 24, that is, of the upper end of the caging members. With the top plate assembly 22 bolted to the upper plate 26a by bolts 30 through spacers 22b, the spring assembly is suspended within enclosure 26 so as to accommodate the compression and extension of springs 12. As springs 12 extend, spring holder 20 is pushed downwardly so as to bias brake shoe 14 downwardly into frictional engagement on rail 12. A pair of actuators 32, which may be hydraulic actuators, are mounted between the base 26c of the enclosure and bearing members such as a cantilevered or otherwise formed pair of rigid flanges 20c extending laterally from spring holder 20. When actuated so as to extend the actuator pistons, actuators 32 drive spring holder 20 upwardly. This compresses springs 12 towards their fully compressed caged position and elevates the brake shoes 14 above rail 18. As spring holder 20 is elevated, caging pin 24 is also elevated so as to raise head 24b on shank 24a into space 28 above the corresponding upper surface of top plate assembly 22.

With the springs fully compressed by the actuators, for example given an actuator piston stroke of approximately 10mm, head 24b will also be elevated by the same stroke into space 28 above the corresponding upper surface of top plate assembly 22. A lock or latch, for example including a latch member such as fork 34 having a thickness substantially equal to the stroke distance is mounted horizontally for lateral sliding translation so as to place the tines 34a of the fork under the annular lip of head 24b of the caging pin. Head 24b may be formed to include an annular lip, rim or collar to engage the fork tines. Fork 34 may be manually actuated by means of for example a handle or pin 34b. Pin 34b is pushed horizontally to insert fork 34 under head 24b when springs 12 are fully compressed. The insertion of the tines 34b of fork 34 under head 24b cages springs 12 so as to park the brake shoes in a position elevated above rail 18. The brake shoes may then be removed for inspection, maintenance, or replacement. To release the brake shoes from their elevated and parked position, the actuators are fully extended so as to further slightly compress springs 12 to an unlock position, for example a further 2mm beyond the 10mm nominal piston stroke, thereby unloading the spring force load from fork 34 by slightly elevating head 24b from fork 34. Fork 34 may then be extracted from underneath head 24b. The actuator pistons may then be retracted to allow springs 12 to extend by the piston stroke distance so as to engage the brake shoe against the rail. In the above example which is not intended to be limiting, and as illustrated in

Figures 3a - 3e, given of a nominal piston stroke distance of 10mm, once the springs are compressed by the 10mm stroke distance, a further available compression distance, for example a further 2mm of compression is available so as to release fork 24 from under head 24b of the caging pin. Also, when the springs are extended the stroke distance of for example 10mm, the springs should also be capable of a further extension of for example 2mm so as to accommodate fluctuations in the elevation of rail 12 relative to the elevation of enclosure 26. Thus for example within a range of plus or minus 2mm the brake shoe should be capable of vertical translation while still maintaining a downward force on the rail sufficient to provide the braking function to inhibit movement of the machine along the rail. To give one example of the force exerted by the springs, which example is not intended to be limiting, each spring may provide a nominal force of 270 kilo-newtons with a maximum force of approximately 300 kilo-newtons. The pair of springs thus provides a nominal 540 kilo-newton force. Thus for the two springs the force required to be exerted upwardly by the two actuators in order to compress the springs is a nominal 540 kilo- newtons and a maximum of approximately 600 kilo-newtons. The full compression of the springs corresponds to the brake released position of the spring assembly as seen in Figure 3a where the brake shoe is elevated 10mm above the rail and with the spring compressed by the 10mm piston stroke, that is almost to its maximum, for a spring length of 330mm in the example illustrated. In the embodiment illustrated, in the brake release position the enclosure and spring assembly are sized so as to provide a 17mm gap "a" between the bottom of spring holder 20 and the base 26c of the enclosure, a gap "c" of 4mm between the top of caging pin 24 and the underside of upper plate 26a, a fully extended position extension "d" of 23mm, and 57mm stand- off distances "f and "g" respectively between the bottom of base 26c and the top of rail 12, and between the bottom of upper plate 26a and the top of top plate assembly 22.

In the brake set position of Figure 3b the springs have been extended by the nominal stroke distance of 10mm by the retraction of the actuator pistons, so as to provide a combined downward spring force of 540 kilo-newtons pressing the brake shoe against the rail. Thus gap "a" has been reduced to 7mm, the spring length "b" correspondingly extended to 340mm, gap "c" extended to 14mm, the cylinder piston extension "d" reduced to 13mm, the gap "e" between the rail and the brake shoe reduced to nominally zero while the stand-off distances "f ' and "g" remain the same at 57mm each. The holding force of the rail brake is a function of the coefficient of friction between the brake shoe and the rail. For a hardened, serrated brake shoe the coefficient of friction may be a nominal 0.5 thus providing a holding force along the rail of a nominal 270 kilo-newtons.

Figure 3 c illustrates the brake set position in the instance where, for example, the rail elevation has deviated 2mm upwardly so that instead of the 10mm stroke at the nominal rail height the spring travel is instead 8mm so that gap "a" is 9mm, spring length "b" is 338mm, gap V is 12mm, and cylinder piston extension "d" is 15mm, with the brake shoe elevation being offset upwardly by 2mm to account for the deviation in the height of the rail. In this position, the spring force is approximately 484 kilo-newtons.

Figure 3d illustrates the opposite example from Figure 3c in that it illustrates a brake set position where the rail deviation is 2mm below the nominal rail height so that the spring travel is 12mm instead of the nominal 10mm. Thus gap "a" is 5mm, spring length "b" is 342mm, gap "c" is 16mm, and cylinder piston extension "d" is 11mm. The total spring force between the two springs is approximately 456 kilo-newtons. In this example, the maximum working stroke of the springs is 1 mm and the enclosure is sized so that the spring assembly bottoms out within the enclosure at 17mm of stroke.

In the spring caged position of Figure 3e, fork 34 has been inserted under head 24b of caging pin 24 and the actuators 30 retracted so as to allow springs 12 to re-extend by 2mm for a spring length "b" of 332mm to thereby cage the springs by engaging the head of the caging pin down against the fork. Thus gap "a" is reduced to 15mm and gap ⁿ c" is increased to 6mm as cylinder piston extension "d" is retracted for example to a retracted extension of 6mm.

As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.