Abstract:
An improved trailer coupling with integral brake actuator that employs sturdier telescoping inner and outer casings and adjustable rollers there between to compensate for wear and tear tolerances over time. The outer casing is a hollow tubular outer beam, and the inner case is formed as a section of hollow I-beam adapted for a telescoping fit inside the outer case. A plurality of rollers are secured to each side of the outer case and project inwardly to provide bearing support against the outwardly-projecting lateral ridges of the I-beam, and this results in a substantially frictionless telescoping extension. Each roller is selectably offset on an axle to allow adjustment of the degree of support against the lateral ridges of the I-beam, thereby allowing compensation for increased wear tolerances over time. The device also employs an improved damping system including a pair of damping cylinders between the telescoping inner and outer casings, plus a master brake cylinder mounted on damped spring-brackets. A safety release assembly is also provided, and this includes a chain coupled at one end to the towing vehicle and coupled at the other end to a break-away lever that is pivotally mounted atop the outer case in operative engagement with the master cylinder. This way, inadvertent separation of the towing vehicle from the coupling/brake actuator activates the master cylinder to apply the trailer brakes to prevent accidents.

Description:
CROSS-REFERENCED TO RELATED APPLICATIONS 
     The present application derives priority from U.S. Provisional Patent Application No. 60/171,175 for “HEAVY DUTY BRAKE ACTUATOR”; Filed: Dec. 16, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to brake actuators for coupling vehicles with trailers and other towed transports having pneumatic brakes. More specifically, the invention is a heavy duty design for a brake actuator with structural enhancements to increase ruggedness and reliability over others presently on the market. 
     2. Description of the Background 
     There are a wide variety of commercially-available couplings incorporating brake actuators for utility trailers, boat trailers and the like which trailers are equipped with conventional pneumatic wheel brakes. The brake actuators serve to apply the brakes of the trailer as the trailer approaches the pulling vehicle. During towing, when the pulling vehicle decelerates by applying its brakes, the inertia of the trailer causes a forward force upon the towing vehicle. The trailer begins to override the towing vehicle. When this occurs, the trailer brake actuator applies the trailer brakes to reduce the force of inertia in the trailer. This greatly reduces the amount of work required for the pulling vehicle&#39;s brakes to stop the trailer. When the pulling vehicle accelerates, or remains at constant speed, the inertia and/or drag of the trailer is responsible for creating a tensile force between the trailer and pulling vehicle. This tensile force deactivates the actuator; hydraulic pressure to the brakes is released and braking is eliminated. This allows the actuator to function only when the trailer is forcing the pulling vehicle forward and not when the pulling vehicle is pulling the trailer. 
     The design of most trailer brake actuation systems is to have an outer casing which is connected to the trailer, and an inner casing which is to be telescopically operated within the outer casing connected to the pulling vehicle. A typical design for the outer casing is to have complicated geometry and to be formed as a welded assembly of components. It is the telescopic action of the inner casing relative to the outer casing that actuates the master cylinder, which is responsible for hydraulically activating the trailer brakes. For example, U.S. Pat. No. 3,783,982 to Wells discloses a telescoping tongue and brake actuator assembly for brake-equipped trailers which can be extended without disconnecting the braking structure. A motion dampening spring 76 is included. However, the illustrated coupling employs a simple telescoping square-beam design that is subject to frictional wear and tear. Over time it has been found that the wear and tear impedes the cooperation of the parts and eventually causes catastrophic stress fractures. This design has in the past been successful for light duty environments and/or highway conditions in the application of the brakes, thereby preventing the forward force created by the trailer&#39;s inertia upon the towing vehicle. But under heavy loading, rough environment, or off road conditions, and over extended periods of operation these systems presented problems that were never perfected, only remedied by the frequent replacement of these units. These devices presented strength and durability flaws focused upon, in general, the outer casing and/or inner casing. Buckling or bending of these components is common therefore the initial strength of these components is of concern. The telescopic action between the inner casing and outer casing is also of concern. This telescopic action is accomplished in general by the sliding of the outer casing over the inner casing. It is this sliding action that creates problems due to the extreme friction created between the casings. Over time, this friction wears away the walls of the inner and outer casings, substantially weakening these components as well as increasing the amount of clearance between the components, thereby causing them not to fit tight enough. This “slop” adds substantially to the strength problems already discussed herein above. 
     Partial solutions to the above-described situation have been suggested. For instance. U.S. Pat. No. 5,013,059 to Goettker shows a brake actuator/coupler in which a square inner casing 46 fits within a square outer casing 18, and pins 8 through oblong slots 70, 72, 74 and 76 give a sliding degree of freedom. Rollers are used to reduce friction. Specifically, a front roller 40 and rear rollers 42 protrude through inner casing 46 and bear against outer casing 18 to facilitate sliding. A single damping shock absorber 84 is used. While the use of rollers helps, there are still significant torsional stresses and wear and tear issues that renders the design unsuitable for many heavy-duty industrial applications. Even with the rollers, wear and tear over time introduces significant tolerances that can leave the rollers ineffective. Consequently, this and like designs continue to fail after prolonged use on test tracks. 
     Accordingly, there remains a significant need for a more rugged coupling design that combines a sturdier telescoping casing with adjustable rollers to compensate for wear and tear tolerances. The additional use of plural damping shocks and other structural enhancements are capable of giving a level of ruggedness and reliability that far exceeds other coupling/brake actuator units presently on the market. 
     SUMMARY OF THE INVENTION 
     It is, therefore, an object of the present invention to provide a heavy duty trailer coupling with integral brake actuator that employs a sturdier telescoping casing and rollers to compensate for wear and tear tolerances. 
     It is another object to provide adjustable rollers for adjustment of the telescoping inner and outer casings to compensate for increased wear tolerances over time. 
     It is another object to incorporate a damping system inclusive of plural damping cylinders between the telescoping inner and outer casings, plus a damped master brake cylinder. 
     It is another object to provide heavy duty inner and outer casings, the inner casing being welded to control tighter tolerances. 
     In accordance with the above objects, an improved heavy duty trailer coupling with integral brake actuator is provided. The trailer coupling/brake actuator generally comprises a hollow tubular outer beam, and an inner case formed as a section of hollow I-beam and adapted for a telescoping fit inside the outer case. The outer casing may be made from a single piece of reinforced square tubing. Having a solid rolled tube as the basis for the actuator greatly increases the strength of the actuator. The outer casing is reinforced by welded steel straps on the outside, and this increases its strength as well. 
     The inner casing is made from a welded assembly in the shape of a double I-beam. Tight tolerances are kept to ensure that the desired distance is kept between the inner and outer casing. This increases the strength of the inner casing and provides a surface for which the rollers can run on as described. 
     A plurality of rollers are secured to the sides of the outer case and projecting inwardly to provide bearing support against the outwardly-projecting lateral ridges of the I-beam, and this results in a substantially frictionless telescoping extension. Each of the rollers preferably comprises a wheel mounted on a selectably-offset axle to allow adjustment of the degree of support against the lateral ridges of the I-beam. This adjustment feature allows compensation for increased wear tolerances over time. 
     A master pneumatic brake cylinder is mounted inside the outer case for engagement with the inner case. 
     A safety release assembly is provided, and this includes a chain coupled at one end to the towing vehicle and coupled at the other end to a break-away lever that is pivotally mounted atop the outer case and is in operative engagement with the master cylinder. This way, inadvertent separation of the towing vehicle from the coupling/brake actuator activates the master cylinder to apply the trailer brakes to prevent accidents. 
     In addition, an improved damping configuration is provided. Specifically a plurality of master pins are inserted through corresponding grooves through the side walls of the inner case. A pair of damping cylinders are pivotally anchored inside the inner case and each has a piston rod attached to a corresponding one of the master pins. The pneumatic master cylinder for actuating the trailer brakes is separately damped. The pneumatic master cylinder is mounted inside the outer case and has a piston operatively engaged with the inner case for applying the trailer brakes. The pneumatic master cylinder is mounted in the outer case on spring-brackets to provide overload protection. In this regard the spring-brackets engage upon excessive pressure applied to the hydraulic system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects, features, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiment and certain modifications thereof when taken together with the accompanying drawings in which: 
     FIG. 1 is an exploded perspective view of the trailer coupling and brake actuator  1  according to the present invention. 
     FIG. 2 is a composite drawing that includes a top view cross-section and side view cross-section of the nested inner case P 18  (dotted lines) and outer case P 1  of the coupling/brake actuator  1  as in FIG.  1 . 
     FIG. 3 is a composite drawing that includes a top view and side view of the outer case P 1  of FIG.  1 . 
     FIG. 4 is a composite drawings that includes a top view, end view and side view (clockwise from top) of the inner case assembly  3  of FIG.  1 . 
     FIG. 5 is a side view of the I-beam section  187  of the inner case P 18  of FIG.  1 . 
     FIG. 6 is a top view of the I-beam section  187  of the inner case P 18  of FIG.  5 . 
     FIG. 7 is a detailed end view showing the chamfered cross-section of both side walls of the I-beam section  187  as in FIGS. 5 and 6. 
     FIG. 8 is a side view of one of the side reinforcement plates  195 . 
     FIG. 9 is a composite drawing showing a side view, end view and bottom view (clockwise from top) of one of the damped cylinder bracket assemblies  24 . 
     FIG. 10 is a composite drawing inclusive of a side view and end view of the cylinder frame front  243 . 
     FIG. 11 is a composite drawing inclusive of a side view and end view of the cylinder frame rear  244 . 
     FIG. 12 is a composite drawing inclusive of a side view and end view of the cylinder frame strap  241 . 
     FIG. 13 is a composite drawing showing a side view, end view and top view (clockwise from top) of the arcuate spring strap  245 . 
     FIG. 14 is a composite drawing showing a top view, side cross-section view and bottom view (from the top) of the safety release assembly  4  as in FIG.  1 . 
     FIG. 15 is a side view of the a break-away lever  10  of FIG.  14 . 
     FIG. 16 is a composite drawing showing a top view side view and pattern view (counterclockwise from top) of one of the lever mounting brackets  270  as in FIG.  1 . 
     FIG. 17 is a composite drawing showing a top view, side view and pattern view (counterclockwise from top) of one of the lever locks  12 , 13  as in FIG.  14 . 
     FIG. 18 is a side view of the weather seal  11  of FIG.  14 . 
     FIG. 19 is a composite side view and end view of an exemplary roller axle P 3 . 
     FIG. 20 is a composite drawing inclusive of a close-up side view and end view of the push-rod assembly  20 . 
     FIG. 21 is a close-up side view of the push-rod  335  of FIG.  20 . 
     FIG. 22 is a composite side view and end view of the angled push-rod lever  330 . 
     FIG. 23 is a composite side view and end view of the push-rod pin  28  for insertion through holes in the walls of the I-beam  187 . 
     FIG. 24 is a composite side view and end view of an exemplary master pin  31  for insertion through the push rod collar of the pneumatic cylinder  29 . 
     FIG. 25 is a composite side view and end view of an exemplary damper pin  188  for insertion through the collar of a pneumatic cylinder  29 . 
     FIG. 26 is a composite side view and end view of an exemplary access cover  16 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is an exploded perspective view of the trailer coupling and brake actuator  1  according to the preferred embodiment of the present invention. Coupling/brake actuator  1  includes a reinforced square tubular outer case (or tongue) P 1  that houses both a master cylinder assembly  2  and a safety release assembly  4 . An inner case assembly  3  inclusive of an inner case P 18  is inserted in one end of outer case P 1  for a telescoping fit therein, the inner case assembly  3  being mounted on adjustable rollers  5  for decreased friction between inner case P 18  and outer case P 1 . The outward extension of inner case assembly  3  is limited by two master pins  31  and is preferably damped by at least two pneumatic damping cylinders  29  attached between the inner case assembly  3  and master cylinder assembly  2  by master pins  31 . A towing vehicle can be coupled to a trailer via the coupling/brake actuator  1 , and for this purpose a conventional trailer hitch (not seen in FIG. 1) may be anchored against the forward end of inner casing P 18 . A typical trailer hitch may include a forwardly projecting lunette (to be described) that catches a hook-type hitch mounted on the towing vehicle. The trailer hitch and lunette configuration are well-known and not considered to form a part of the invention being described herein. The forward pull of the towing vehicle pulls the outer case P 1  outward and the tensile force is transmitted through damping cylinders  29  to the inner case assembly  3  and to the trailer. This tensile force extends the inner casing P 18  with respect to the outer casing P 1 , effectively rendering the master cylinder assembly  2 , and subsequently the trailer brakes, inactivated. Upon deceleration of the towing vehicle, such as is caused by the applying of brakes or letting up on the accelerator, the initial tendency is for the trailer to overrun the towing vehicle. The inner case assembly  3  compresses inward into the outer case P 1  against the resistance of damping cylinders  29 . This allows for insignificant variations in relative speed of the trailer and the towing vehicle. Braking of the towing vehicle also activates the master cylinder  19  to apply the trailer brakes. The inner casing P 18  and pin  28  move aft relative to the outer casing P 1 , and this pushes a push-rod assembly  20  into the master cylinder  19  and effectively applies the trailer brakes. 
     Safety release assembly  4  operates to prevent accidents in case the trailer inadvertently becomes uncoupled. Safety release assembly  4  includes a breakaway chain  8  attached to the towing vehicle to pull the top of a pivoted break-away lever  10 . The bottom of lever  10  bears against and activates the master cylinder  19  to apply the trailer brakes. Lever lock brackets  12  hold the break-away lever  10  in place once it has been activated. Thus, the trailer comes to an immediate stop when it becomes uncoupled. 
     FIG. 2 is a composite drawing that includes a top view cross-section and side view cross-section of the coupling/brake actuator  1  according to the present invention. The inner case assembly P 18  (dotted lines) rides upon eight adjustable rollers  5 , a set of four rollers  5  being mounted internally on each of the two vertical walls of outer casing P 1 . The master cylinder assembly  2  (inclusive of master cylinder  19 ) is secured inside the outer case P 1 , and master cylinder  19  operates through push-rod assembly  20  which is operatively engaged with the inner case assembly  3  (bearing against a push-rod pin  28  at the leading end of the I-beam inner case assembly P 18 ). 
     FIG. 3 is a composite drawing that includes a top view and side view of the outer case P 1 . The outer case P 1  is a generally square tubular section of {fraction (3/16)}″ steel. The outer case P 1  is machined in places for mounting of the various components, and it is a significant feature of the present invention that certain machined areas are reinforced by welded steel plates. This reinforcement contributes greatly to the structural reliability. Specifically, a pair of 2.81″×4″×¼″ steel master pin straps  46  are welded to each side of the outer case P 1  . Each master pin strap  46  corresponds to the position where a pair of master pins  31  and adjacent pair of spaced rollers  5  are mounted, respectively (see, also, FIG.  2 ). In addition, a trio of 4″×1.25″×¼″ steel front straps  44 ,  45  are welded to each front side of the outer case P 1  as shown. The two opposing front straps  44  correspond to the positions where opposing pairs of spaced rollers  5  are mounted (see, also, FIG.  2 ). Top front plate  45  is a solid strip welded across the top of the outer case P 1  at the forward edge. A pair of square holes is formed through the outer case P 1  and each master pin strap  46  to seat the ends of the axles of the forward spaced rollers  5 . Likewise, a pair of round holes is formed through the outer case P 1  and each master pin strap  46  to seat the ends of the master pins  31 . This way, the master pin straps  46  effectively double the length of the apertures for seating the master pins  31  and the roller  5  axles, and the extra reinforcement greatly reduces egging of the holes. Likewise, a pair of square holes is formed through the outer case P 1  and each opposing front strap  44  to seat the ends of the axles of the aft spaced rollers  5 . The steel front straps  44 ,  45  and master pin straps  46  also reinforce the outer casing P 1  and reduce wear between the two casings P 1 , P 18 . Other holes  47 ,  48 ,  49  are drilled in the illustrated positions for mounting the respective master cylinder assembly  2 , the safety release assembly  4 , and an access cover  16  (to be described). In addition, a rectangular window  400  is formed to provide access to the fill cap  21  of the master cylinder  19 . and this covered by an access cover  16  to be described. 
     FIG. 4 is a composite drawing that includes a top view (A), end view (B) and side view (C) (clockwise from top) of the inner case assembly  3 . The inner case assembly  3  includes the inner case P 18  itself and a number of attachments thereto. One end of the inner case P 18  is formed as a trailer coupling according to the intended application, and a variety of standard trailer coupling configurations are known to exist. For instance, other attachments better suited for ball hitches or the like may be readily substituted. One exemplary trailer coupling is shown in FIG.  4  and this includes a yoked portion  181  with opposing flanges machined to receive a coupling bolt  182 . The coupling bolt  182  may be secured by a conventional lock washer  183  and cotter pin  184 . A circular lunette  185  formed with an integral collar is pivotally attached to the coupling bolt  182  for attachment to the towing vehicle. The yoked portion  181  of the inner case P 18  is integrally formed and the remaining length comprises a section of hollow I-beam  187 . A pair of pneumatic cylinders  29  are pivotally attached at one end inside the hollow of the I-beam  187 . This attachment is accomplished by a pair of spaced damper pins  188  each carried within opposing holes formed in the walls of I-beam section  187 . Damper pins  188  are each inserted through the holes and through the collar of a corresponding pneumatic cylinder  29  as shown, and are secured in place by cotter pins  6 . The push rods of the pneumatic cylinders  29  are each secured to a corresponding master pin  31 . The master pins  31  ride along oblong grooves  193  formed in both walls of the I-beam section  187 . To reduce the frictional wear of the sliding master pins  31 , the grooves  193  in the walls of the I-beam section  187  are reinforced with side reinforcement plates  195  (also formed with aligned oblong grooves). The side reinforcement plates  195  are secured in place to the walls inside the hollow of the I-beam  187  by threaded bolts  196  (preferably, two bolts  196  at the mid section of each side reinforcement plate  195 ). In addition, a push-rod pin  28  is secured in place at the leading end of the I-beam  187  by insertion through holes in the walls of the I-beam  187 . The push-rod pin  28  is pre-drilled with distal through-bores to accept two cotter pins  129  which hold the push-rod pin  28  from the inside of the hollow I-beam to facilitate clearance for the roller wheels  5 . 
     FIG. 5 is a side view of the I-beam section  187  of the inner case P 18 . Oblong grooves  193  are formed as shown through both walls. Holes  192  are formed as shown to accept the bolts  196  for attachment of the side reinforcement plates  195 . Holes  191  are formed proximate the opposing end for attachment of the pair of spaced damper pins  188  (each of which captures a corresponding pneumatic cylinder  29 ). Holes  196  are formed as shown through both walls to accept the push-rod pin  28 . 
     FIG. 6 is a top view of the I-beam section  187  of the inner case P 18  showing a cut-out section  201  machined into the trailing edge of the top plate only of the I-beam section  187 . The lower plate of the I-beam section  187  is identical except that there is no cut-out section  201 . 
     FIG. 7 is a detailed end view showing the cut-out  201  of the top plate of the I-beam section  187 . The cut-out  201  is to allow the inner case P 18  to telescope without hitting the break-away lever  10 . 
     FIG. 8 is a side view of one of the side reinforcement plates  195  illustrating the oblong grooves  193  machined therein. Grooves  193  conform to the grooves in the walls of the I-beam section  187  once side reinforcement plates  195  are secured in place, and this offers significant reinforcement. A pair of holes  205  are machined into the mid section of the side reinforcement plates  195  to accept the bolts  196  for attachment to the walls inside the hollow of the I-beam  187 . 
     Referring back to FIG. 1 the master cylinder assembly  2  is seated inside the hollow of the outer case P 1 . Master cylinder assembly  2  is preferably a commercially available hydraulic master cylinder  19  preferably having a 1¼″ bore, and an upwardly directed filler cap  21 . A rubber gasket  22  and compression fitting  23  allows coupling of a conventional air brake hose thereto. The compression fitting  23  is preferably a {fraction (3/16)}″ inverted seat connector with a 0.040 bleed orifice, a variety of suitable compression fittings  23  being readily available commercial parts. The master cylinder  19  is secured inside the outer case P 1  by a pair of identical damped cylinder bracket assemblies  24  to be described. The cylinder bracket assemblies  24  are bolted through the master cylinder  19  by a pair of ⅜″ hex bolts  25  secured by ⅜″ hex nuts  26  and lock washers  27 , and each bracket assembly  24  is further bolted inside the outer case P 1  by a pair of hex bolts  17  secured by lock washers  14 . The master cylinder  19  is operatively equipped with a push rod assembly  20  for actuating the trailer brakes. 
     FIG. 9 is a composite drawing showing a side view (A), end view (B) and bottom view (C) (clockwise from top) of one of the damped cylinder bracket assemblies  24 . Each cylinder bracket assembly  24  includes a cylinder frame strap  241  defined by opposing holes  242  for insertion of hex bolts  25 . The cylinder frame strap  241  is slidably supported within the upwardly directed yoke  249  of a cylinder frame front  243 , and a like yoke  250  of a cylinder frame rear  244 . An arcuate spring strap  245  is coupled as shown between the cylinder frame front  243  and rear  244  and this slidably supports a pair of spring rods  246 . The spring rods  246  are identical rods of hardened steel, preferably approximately 8″ in length and 0.3120″ in diameter with beveled ends. Spring strap  245  also confines a pair of die springs  247  which are inserted onto the respective spring rods  246 . The die springs  247  are standard spring steel dimensioned to fit over the spring rods  246 . This configuration of the cylinder bracket assemblies  24  provides a sliding degree of spring-damped freedom to the master cylinder  19  which is secured to the cylinder frame strap  241 . 
     FIG. 10 is a composite drawing inclusive of a side view (A) and end view (B) of the cylinder frame front  243  which is a generally rectangular member defined by parallel holes  251  in the base section for slidable passage of spring rods  246 , and an upwardly directed yoke  249  for supporting the cylinder frame strap  241 . 
     FIG. 11 is a composite drawing inclusive of a side view (A) and end view (B) of the cylinder frame rear  244  which is a strip defined by parallel holes  252  in the base section for slidable passage of spring rods  246 , and an upwardly directed yoke  250  for supporting the cylinder frame strap  241 . 
     FIG. 12 is a composite drawing inclusive of a side view (A) and end view (B) of the cylinder frame strap  241  that is slidably supported between the cylinder frame front and rear  243 ,  244 . Cylinder frame strap  241  is a metal strip defined by mounting holes  255  for passage of bolts  25  (see FIG. 1) and attachment thereby to the master cylinder  19 . 
     FIG. 13 is a composite drawing showing a side view (A), end view (B) and top view (C) (clockwise from top) of the arcuate spring strap  245  that is coupled between the cylinder frame front  243  and rear  244  for slidably supporting the spring rods  246 . The spring strap  245  has two spaced parallel extensions  260  each defined by a pair of spaced holes  261 . 
     FIG. 14 is a composite drawing showing a top view (A), side cross-section view (B) and bottom view (C) of the safety release assembly  4 . Safety release assembly  4  includes a breakaway chain  8  with an end-mounted clasp  411  for attachment to the towing vehicle. An approximate 3 ft. chain is suitable for breakaway chain  8 . The chain  8  is attached to the upper end of a break-away lever  10  by a standard S-hook  9 . The lower end of the break-away lever  10  is pivotally mounted inside the outer case P 1  by lever mounting brackets  270  that support a clevis pin  272  inserted through the break-away lever  10 . Clevis pin  272  is secured in the break-away lever  10  by a cotter pin  273 . The lever mounting brackets  270  are bolted by bolts  15  and lockwashers  14  to the top wall of outer case P 1 , and a small window is provided through the outer case P 1  to allow the lower end of the break-away lever  10  to protrude down through. The lower end of the break-away lever  10  bears directly against the push-rod assembly  20  and, subsequently, against the master cylinder  19 . This way, if the towing vehicle somehow becomes uncoupled from the towed transport, the chain  8  attached to vehicle will pull taught and this will throw the upper end of break-away lever  10  forward, thereby levering the master cylinder P 1  rearward and applying the trailer brakes. Preferably, the window in the outer case P 1  is sealed by a rubber weather seal  11  with a slit for passage of the lever  10 . Break-away locks  12 ,  13  are secured atop the weather seal  11  each by a pair of hex bolts  15  through lock washers  14 . The break-away locks  12 ,  13  catch the lever  10  and maintain it in a normally disengaged position until a significant force on chain  8  overcomes the friction. 
     FIG. 15 is a side view of the a break-away lever  10  which is a substantially flat section of metal plate. The lever  10  is formed with a hole  280  at one end for insertion of S-hook  9 . The other end of the break-away lever  10  is adapted to conform to the contour of the master cylinder  19  that it bears against. A pivot hole  281  is provided for insertion of clevis pin  272 . 
     FIG. 16 is a composite drawing showing a top view (A), side view (B) and pattern view (C) (counter-clockwise from top) of one of the lever mounting brackets  270 . Both lever mounting brackets  270  are steel sections (patterned as shown at (C) with pivot hole  290  and spaced mounting holes  291 . The steel sections are bent along the dotted line to provide an offset pivotable mounting for lever  10  on outer case P 1 . 
     FIG. 17 is a composite drawing showing a top view (A), side view (B) and pattern view (C) (counter-clockwise from top) of one of the lever locks  12 , 13 . Both lever locks  12 ,  13  are steel sections patterned as shown at (C) with spaced mounting holes  293  and a tapered tab  294  at the top to allow the lever  10  to be set in a disengaged position and to maintain it there, as well as to lock the brakes on upon engagement of the lever  10 . Both lever locks  12 ,  13  are bent along the dotted line to provide an upward mounting atop the outer case P 1 , and to angle the tab  294  inward slightly in order to facilitate setting of and to catch the lever  10 . 
     FIG. 18 is a side view of the weather seal  11  for sealing the window in the outer case P 1 . Weather seal  11  is preferably an oval rubber section defined by a slit  297  for passage of the lever  10 , and four holes  298  for insertion of bolts  15 . 
     Referring back to FIG. 2, four adjustable rollers  5  (inclusive of two front rollers and rear rollers) are mounted on each side wall of the outer casing P 1  and bear against the projecting edges of the inner casing P 18  to facilitate sliding thereof. The rollers  5  ride against a corresponding overhanging edge of the I-beam  187 . As seen in FIG. 1, each roller  5  further comprises a wheel P 2  that is rotatably mounted on an axle P 3 . Wheel P 2  is secured to axle P 3  by a bolt P 4  and washer P 5  combination, the bolt P 4  being threaded into the end of axle P 3 . Wheels P 2  may be simple annular steel members. 
     FIG. 19 is a composite side view (A) and end view (B) of an exemplary roller axle P 3 . Roller axle P 3  comprises an outer hub  300  for retaining the wheels P 2 , a circular mid-section  310  for seating the wheels P 2  and an offset square end section  320  to facilitate adjustment. The entire roller axle P 3  is defined by a threaded central through-bore for insertion of the bolt P 4  and washer P 5  combination as seen in FIG.  1 . When assembled to the outer case P 1 , the offset square end section  320  of roller axle P 3  is inserted into a conforming square hole in outer case P 1 . The capability for adjustment is important because prolonged operation of the trailer coupling/brake actuator  1  can result in wear tolerances. Specifically, the rollers  5  may wear and lose their effectiveness. Thus, the square end section  320  is selectively off set from the center axis to facilitate four vertical clearance settings of wheels P 2  with respect to I-beam P 18 . Presently, the dimensions are as shown in FIG. 19 to provide a selectable 0.235″, 0.219″, 0.265″ or 0.281″ offset. The degree of off set is selected simply by removing bolt P 4  and axle P 3 , rotating in increments of 90 degrees, and reinstalling. 
     As previously stated, the master cylinder  19  is operatively equipped with a push rod assembly  20  for actuating the trailer brakes and FIG. 20 is a composite drawing inclusive of a close-up side view (A) and end view (B) of the push-rod assembly  20 . Push-rod assembly  20  further comprises an angled push-rod lever  330  that is screwed onto a push-rod  335 . 
     FIG. 21 is a composite drawing inclusive of a close-up side view (A) and end view (B) of the push rod  335 . Push-rod  335  generally comprises a length of carbon steel or the like having a rounded tip for insertion into master cylinder  19 , and a threaded end for attachment of angled push-rod lever  330 . A collar  337  provides a backing for the angled push-rod lever  330 , and a filleted portion surrounds the other side of collar  337  for a rubber boot to fit over. 
     FIG. 22 is a composite side view (A) and end view (B) of the angled push-rod lever  330  which is a section of steel plate bent at an approximate 90 degree angle and formed with a hole  339  therein. The angled push-rod lever  330  is operatively engaged with the inner case assembly  3  (bearing against push-rod pin  28  at the leading end of the I-beam inner case assembly P 18 ) and urged forward into the master cylinder  19  for actuating the trailer brakes. 
     FIG. 23 is a composite side view (A) and end view (B) of the push-rod pin  28  for insertion through holes in the walls of the I-beam  187 . The push-rod pin  28  is pre-drilled with distal through-bores  340  to accept the two cotter pins  129  (not shown in FIG.  23 ), and its ends are beveled to facilitate easier insertion. 
     Referring back to FIG. 1, the telescoping extension of inner case assembly  3  is damped by two pneumatic cylinders  29  both of which are attached between the inner case assembly  3  and master cylinder assembly  2 . There are a variety of commercially available pneumatic cylinders that will suffice for this purpose, and the presently preferred embodiment employs cylinders that fit the following dimensional and performance constraints: 
     Collapsed length (collar to collar): 6″±0.125 
     Extended length (″): 8.07“±0.125 
     Stroke: 2.07″ 
     Tensile Strength: 3000 lbf 
     Diameter: 1.63″ 
     The pistons of the pneumatic cylinders  29  are each secured at one end to the corresponding master pins  31  which ride along the oblong grooves  193  formed in both walls of the I-beam section  187 . The other ends of the pneumatic cylinders  29  are pivotally attached to the inner side walls of the hollow I-beam  187  by a pair of spaced damper pins  188 . 
     FIG. 24 is a composite side view (A) and end view (B) of an exemplary master pin  31  for insertion through the push rod collar of the pneumatic cylinder  29 . The master pin  31  is pre-drilled with a distal through-bore  381  to accept a cotter pin  32  (not shown in FIG.  24 ), and the ends are beveled to facilitate easier insertion. A flange  382  at the other end limits insertion. 
     FIG. 25 is a composite side view (A) and end view (B) of an exemplary damper pin  188  for insertion through the collar of a pneumatic cylinder  29 . The damper pin  188  is pre-drilled with a distal through-bore  391  to accept a cotter pin  6  (not shown in FIG.  25 ), and the ends are beveled to facilitate easier insertion. A flange  392  at the other end limits insertion. 
     Referring back to FIG. 1, a rectangular window  400  is formed in the outer case P 1  to provide access to the fill cap  21  of the master cylinder  19 , and this covered by an access cover  16 . 
     FIG. 26 is a composite side view (A) and end view (B) of an exemplary access cover  16 . Access cover  16  may be formed from a flat section of steel plate that is cut and bent to form a shallow enclosure bounded on the top and sides, and with laterally protruding brackets  402 . Both brackets  402  are defined by holes  404  by which the access cover  16  can be bolted to the outer case P 1 . 
     In operation of the foregoing, the lunette  185  is attached to the vehicle as is the chain  8  of safety release assembly  4 . Should the trailer begin to override the towing vehicle, the outer case P 1  and I-beam inner case assembly P 18  compress together (aided by rollers  5 ), and the push-rod pin  28  bears against the angled push-rod lever  330  urging push-rod  335  into the master cylinder  19  of the trailer brake actuator, which in turn (via a connected air brake hose) applies the trailer brakes to reduce the force of inertia in the trailer. This greatly reduces the amount of work required for the pulling vehicle&#39;s brakes to stop the trailer. When the pulling vehicle accelerates, or remains at constant speed, the inertia and/or drag of the trailer is responsible for creating a tensile force between the trailer and pulling vehicle. This tensile force deactivates the brakes. This allows the actuator to function only when the trailer is forcing the pulling vehicle forward and not when the pulling vehicle is pulling the trailer. Safety release assembly  4  operates to prevent accidents in case the trailer inadvertently becomes uncoupled. 
     Having now fully set forth the preferred embodiments and certain modifications of the concept underlying the present invention, various other embodiments as well as certain variations and modifications of the embodiments herein shown and described will obviously occur to those skilled in the art upon becoming familiar with said underlying concept. It is to be understood, therefore, that the invention may be practiced otherwise than as specifically set forth in the appended claims.