Abstract:
A trailer is equipped with a surge braking system having a braking/dampening unit  70  that is integrated with a common reservoir  71  that supplies brake fluid to both the master brake cylinder  72  and the dampener cylinder  75 , so that if the master cylinder is starved of brake fluid, the dampener also is starved of fluid and the jarring between the forward hitch and the rear housing in response to acceleration and deceleration of the towing vehicle will alert the operator of the towing vehicle to replenish the reservoir with brake fluid. Safety cable  111  connects at one end to the towing vehicle and actuates the master cylinder in response to tension being applied thereto, and latch  98  moves in behind the master cylinder and locks the master cylinder in it operative position so as to hold the brakes in their locked position.

Description:
TECHNICAL FIELD 
     The present invention is generally related to self actuated hydraulic trailer braking systems and, more particularly, to an apparatus for alerting an operator of a vehicle which is towing a trailer when the hydraulic brake fluid of the trailer brake system is low. 
     BACKGROUND OF THE INVENTION 
     Self-actuated trailer surge brakes are known in the art. Typically, surge brakes have movable sections, a forward unit which is positioned adjacent the ball hitch of the trailer and a rear unit which is positioned rearwardly of the forward unit. The units move with respect to each other when a trailer surges forwardly or rearwardly with respect to the towing vehicle, typically due to the deceleration or acceleration of the towing vehicle. When the rear unit of the surge brake mechanism moves forwardly relative to the forward unit of the surge brake mechanism, the relative movement between the forward and rear units is used to actuate the hydraulic brakes of the trailer. The relative forward motion of the rear unit causes a member on the forward unit to actuate a master brake cylinder on the rear unit. Upon being actuated, the master brake cylinder pressurizes the wheel cylinders to apply the brakes of the trailer. 
     Although the provision of a surge brake for a trailer prevents the trailer from over running the towing vehicle, the relative movement of the forward and rearward units of the surge brake also creates a potential problem of the jarring of the trailer and towing vehicle when the forward and rearward units clash as they reach the limits of their relative movements. 
     In order to eliminate the jarring between the forward and rearward units of the surge brake, prior art surge brake mechanisms typically include a hydraulic surge dampener for dampening the relative motion of the rear unit with respect to the front unit of the trailer hitch, and therefore between the trailer and the towing vehicle. The surge dampener relieves the jarring between the units both when the towing vehicle accelerates and decelerates with respect to the trailer. When the towing vehicle accelerates the dampener permits a full and smooth extension of the rear unit with respect to the forward unit, thus eliminating a jarring impact when the front unit fully extends with respect to the rear unit. Likewise, the dampener cushions the movement of the rear unit toward the forward unit of the trailer hitch when the brakes of the vehicle are applied. Typically, the prior art dampener is integrated in parallel with the surge brake mechanism. Without the dampener mechanism, the jarring impact caused by the clash between the rear unit and the forward unit would prematurely decrease the life span of the surge brake mechanism. 
     However, a problem with such prior mechanisms is that the master brake cylinder can be depleted of hydraulic fluid without the knowledge of the operator of the vehicle. The brake assembly does not give the vehicle operator an indication that the hydraulic brake fluid is depleted and the brakes are not operable. 
     SUMMARY OF THE INVENTION 
     Briefly described, the present invention is directed to a self actuated hydraulic braking mechanism for a trailer which includes a master cylinder and a hydraulic dampener, and a single brake fluid reservoir for supplying brake fluid to both the master cylinder and to the hydraulic dampener. When the brake fluid becomes dissipated from the reservoir, it eventually becomes dissipated or “starved” from the dampener and the master cylinder. When there is an inadequate amount of brake fluid in the dampener the dampener begins to fail, in that it begins to inadequately suppress the jarring between the surging of the trailer toward the towing vehicle when the brakes of the towing vehicle are applied, or the surging of the towing vehicle away from the trailer when the towing vehicle accelerates. The operator of the vehicle soon senses the increased surging and jarring between the trailer and the towing vehicle and, as a result, realizes that the brake fluid of the trailer brake system is low and needs replenishing. 
     Another feature of the invention is a self actuating brake latch which holds the master cylinder of the brakes in an actuated condition in response to the trailer becoming detached from the towing vehicle. A tether or cable is attached between the towing vehicle and the brake mechanism and operates the brake latch when tension is applied to the cable, as when the trailer hitch becomes inadvertently detached from the towing vehicle. 
     Therefore, it is an object of the present invention to provide an operator of a towing vehicle with a warning when there is an inadequate amount of hydraulic brake fluid in the hydraulic brake fluid reservoir of the surge brakes of a trailer hitch apparatus. 
     It is another object of the present invention to provide for an integrated dampening/braking apparatus in a hydraulic surge brake of a trailer. 
     It is another aspect of the invention to provide for a device for manually priming the brakes of a trailer, such that air can be bled from the hydraulic brake lines of the trailer. 
     It is another object of the invention to provide for an improved device to actuate the brakes of the trailer when the trailer and the towing vehicle becomes separated, and a device that latches the brakes in actuated position when the towing vehicle and trailer become separated. 
     Still another object of the present invention, is to provide that the latching mechanism can be easily disengaged by the operator. 
     Other objects, features and advantages of the invention will become apparent from reading the following specification, when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
     FIG. 1 is a perspective view of the trailer hitch mechanism. 
     FIG. 2 is a side cross sectional view of the trailer hitch mechanism of FIG. 1, viewed along lines  2 — 2  of FIG.  3 . 
     FIG. 3 is a top cross sectional view of the trailer hitch, taken along lines  3 — 3  of FIG.  2 . 
     FIG. 4 is a side cross sectional view of the trailer hitch, similar to FIG. 2, but showing the hitch in its retracted position. 
     FIG. 5 is a side cross sectional view of the master brake cylinder, brake plunger and reservoir. 
     FIG. 6 is a side cross sectional view of the dampener cylinder, dampener plunger and reservoir. 
     FIG. 7A is a side view of the safety actuating plate and the brake piston rod. 
     FIG. 7B is a front view of the safety actuating plate and the brake piston rod. 
     FIG. 7C is a top view of the safety actuating plate and the brake piston rod. 
     FIG. 8 is a top view of a towing vehicle coupled to a trailer that includes the trailer hitch mechanism. 
    
    
     DETAILED DESCRIPTION 
     The trailer hitch mechanism partly follows conventional details familiar to those skilled in the art so the following description will not deal needlessly with such conventional or irrelevant details. 
     Referring now to in more detail to the drawings, in which like numbers refer to parts throughout several views, the invention relates to a trailer hitch mechanism  10  for a trailer having hydraulic brakes. Referring now to FIG. 8, a towing vehicle  202  tows trailer  204 . The trailer  204  includes hydraulic brakes  206  that are hydraulically connected to hitch mechanism  10  through hydraulic brake line  208 . The hitch mechanism  10  includes a rear housing  40  coupled to tongue  8  of the trailer  204  and a forward coupler  20 , which is adapted to removably couple with a hitch ball  6 , which is shown in FIG. 4, affixed to the towing vehicle  202 . Rear housing  40  is adapted to fit around forward coupler  20  and is slidably mounted to the forward coupler  20 , thereby allowing relative motion along the longitudinal direction of hitch mechanism  10 . FIGS. 1 and 2 illustrate the relative position of forward coupler  20  and rear housing  40  responsive to the towing vehicle  202  pulling the trailer, such that the trailer hitch mechanism  10  is fully extended. 
     Responsive to the deceleration of the towing vehicle  6 , and the corresponding deceleration of forward coupler  20 , rear housing  40  tends to move forward relative to forward coupler  20  as illustrated in FIG. 4, such that trailer hitch mechanism is completely contracted. The relative motion of rear housing  40  with respect to forward coupler  20  causes a brake piston head  74  connected to a brake piston rod  73  to pressurize hydraulic brake fluid in a master brake cylinder  72 , thereby applying hydraulic pressure to the hydraulic brakes of the trailer. Responsive to acceleration of the towing vehicle or frictional forces exerted on the trailer, such as air resistance, the rear housing  40  tends to move to the position illustrated in FIG. 2, thereby fully extending rear housing  40  relative to forward coupler  20  and relieving the hydraulic brake pressure in master brake cylinder  72 . The actuation of the braking mechanism and the relative motion of rear housing  40  with respect to forward coupler  20  will be discussed in greater detail herein below. 
     Referring to FIG. 1, forward coupler  20  formed from a piece of heavy duty sheet metal has a front end  21 , a rear end  22 , a top wall  23 , a first side wall  24  and a second side wall  25  extending generally downwardly from the top wall  23 . The front end  21  has a socket  26 , formed integrally within forward coupler  20 , with a downward opening for receiving hitch ball  6 . Forward coupler  20  is secured to hitch ball  6  by means known in the art and will not be discussed in detail. 
     Referring to FIGS. 2 and 4, cross sectional views of trailer hitch mechanism  10  taken along the  2 — 2  of FIG. 3, each of the opposed side walls  24  and  25  of the forward coupler  20  have aligned front axle slots  27  and aligned rear axle slots  28  formed therethrough for receiving axle bolts  60  and  61  respectively. The longitudinal dimension of the pairs of slots  27  and  28  extend generally in the longitudinal direction of hitch mechanism  10 . Front axle slots  27  are offset in front of and below the rear axle slots  28 . 
     Referring to FIGS. 2-4, forward coupler  20  further includes a U-shaped coupling bracket  30  that extends generally upwardly from top wall  23 . U-shaped coupling bracket  30  is formed from a piece of heavy duty sheet metal such that it has side legs  32  and  33  and base leg  31 , and such that base leg  31  is generally narrower than the width of top wall  23 . Side legs  32  and  33  extend rearwardly from base leg  31 , generally parallel to first sidewall  24  and second side wall  25 , respectively. Base leg  31  has a first hole  34  and a second hole  35  formed therethrough, each for receiving a piston rod. U-shaped coupling bracket  30  is permanently affixed to top wall  23  by means such as welding. 
     Referring to again to FIG. 1, rear housing  40  has a front end  41 , a rear end  42 , a top wall  43 , a first side wall  44  and a second side wall  45  extending generally downwardly from top wall  43  and is formed from heavy duty sheet metal in an inverted U-shape, such that front end  41  of rear housing  40  is sized and shaped to fit about rear end  22  of forward coupler  20 , and rear end  42  of rear housing  40  straddles the tongue  8  of the trailer. Opposed sidewalls  44  and  45  have a first pair of aligned axle bolt holes  46  and a second pair of aligned axle bolt holes  47  formed therethrough for receiving axle bolts  60  and  61 , respectively. The first pair of axle bolt holes  46  and second pair of axle bolt holes  47  are arranged such that when rear housing  40  is assembled with forward coupler  20 , the pairs of axle bolt holes  46  and  47  are aligned with the pairs of axle slots  27  and  28 , respectively, of forward coupler  20 , and receive the bolts  60  and  61 . In addition, proximal to rear end  42  of rear housing  40  opposed side walls  44  and  45  have aligned pairs of bolt holes  48  and  49  formed therethrough for bolting rear housing  40  to the tongue  8  of the trailer. In addition, top wall  43  of rear housing  40  has threaded cap hole  50  formed therethrough for receiving cap  7  and has opening  51  formed therethrough proximal to front end  41 . 
     Referring to FIG.  2  and FIG. 3, when rear housing  40  is assembled with forward coupler  20 , threaded axle bolt  60  extends through axle bolt hole  46  of first side wall  44  of rear housing  40 , through the pair of aligned front axle slots  27  of forward coupler  20 , and through axle bolt hole  46  of second side wall  45  of rear housing  40 , and is secured in position by nut  64 . A pair of juxtaposed front bearings  62  is mounted to axle bolt  60  between the opposed sidewalls  24  and  25  of forward coupler  20 . A load bearing plate  66  is rigidly affixed, by means such as welding, to the opposed sidewalls  24  and  25  of forward coupler  20  beneath front axle slots  27  for bearing against bearings  62 . Threaded axle bolt  61  extends through axle bolt hole  47  of first side wall  44  of rear housing  40 , through the pair of aligned rear axle slots  28  of forward coupler  20 , and through axle bolt hole  47  of second side wall  45  of rear housing  40 , and is secured in position by nut  65 . A pair of juxtaposed rear bearings  63  is mounted to axle bolt  61  between the opposed sidewalls  24  and  25  of forward coupler  20 . Rear bearings  61  bear against the inner surface of top wall  23  of forward coupler  20 . The longitudinal length of axle slots  27  and  28  defines the range of the relative motion between forward coupler  20  and rear housing  40 . In FIG. 2 the trailer hitch mechanism  10  is fully extended with the axle bolts  60  and  61  being in contact with the rear of axle slots  27  and  28 , respectively. In FIG. 4 the trailer hitch mechanism  10  is fully contracted with axle bolts  60  and  61  being in contact with the front of axle slots  27  and  28 , respectively. 
     Referring to FIGS. 5 and 6, braking-dampening apparatus  70  includes hydraulic brake fluid reservoir  71 , master brake cylinder  72 , brake piston rod  73 , brake piston head  74 , dampener cylinder  75 , dampener piston rod  76 , and dampener piston head  77 . As illustrated in FIGS. 2 and 4, hydraulic brake fluid reservoir  71  is rigidly affixed to the interior portion of rear housing  40  proximal to the rear end  42 . Hydraulic brake fluid reservoir  71  is in communication with threaded cap hole  50 , thus hydraulic brake fluid can be poured into reservoir  71  through cap hole  50 . 
     Referring again to FIGS. 5 and 6, hydraulic brake fluid reservoir  71  is in communication with master brake cylinder  72  through aperture  79  so that hydraulic brake fluid can be transferred between hydraulic brake fluid reservoir  71  and master brake cylinder  72 . In addition, hydraulic brake fluid reservoir  71  is in communication with dampener cylinder  75  through front restrictive aperture  80  and rear restrictive aperture  81 . Restrictive apertures  80  and  81  are narrow apertures for transferring hydraulic brake fluid between hydraulic brake fluid reservoir  71  and dampener cylinder  75 . Thus, master brake cylinder  72  and dampener cylinder  75  are in separate communication with hydraulic brake fluid reservoir  71 . 
     Master brake cylinder  72  and dampener cylinder  75  are approximately parallel and aligned along the longitudinal direction of hitch mechanism  10  and rigidly affixed to the bottom portion of reservoir  71 . In another implementation master brake cylinder  72 , dampener cylinder  75 , and reservoir  71  are integrally formed. A hydraulic brake fluid line of the trailer is coupled to the rear end of master brake cylinder  72  by coupling nut  86  (FIG.  2 ). Thus, the interior of master brake cylinder  72  is in communication with the trailer&#39;s hydraulic brake fluid line, thereby enabling hydraulic pressure generated in master brake cylinder  72  to be transmitted to the trailer&#39;s hydraulic brakes via the trailer&#39;s hydraulic brake fluid line. 
     Referring to FIG. 4, the braking/dampening apparatus  70  further includes safety actuating plate  90 , tube  120 , coil spring  116  and washer  119 , which are configured to cooperate with piston rod  73  to actuate the brakes of the trailer responsive to rear housing  40  moving forward relative to forward coupler  20 . Piston head  74  is rigidly affixed to hydraulic brake piston rod  73 , which extends therefrom to beyond coupling bracket  30  through piston rod hole  34  of base leg  31  and is slidably coupled thereto. Safety actuating plate  90  is rigidly affixed to tube  120  and abuts base leg  31 . Tube  120  is slidably mounted on piston rod  73  between base leg  31  and master brake cylinder  72  and safety actuating plate is configured so that it does not fit through brake piston rod hole  34 . Washer  119  is mounted on piston rod  73  between master brake cylinder  72  and safety actuating plate  90 . Piston rod  73  is stepped so that the diameter of the forward portion of piston rod  73  is less than the rearward portion of piston rod  73 , as shown in FIG.  5 . Washer  119  is configured to be slidably mounted on only the forward portion of piston rod  73 . Coil spring  116  is mounted around piston rod  73  between safety actuating plate  90  and washer  119  and pushes safety actuating plate  90  against base leg  31  and pushes washer  119  against step  121  of piston rod  73 . Thus, as rear housing  40  moves forward with respect to forward coupler  20 , piston rod  73  moves forward and consequently so does washer  119  while safety actuating plate  90  remains abutted against base leg  31 , thereby compressing coil spring  116  between safety actuating plate  90  and washer  119 . The compression of coil spring  116  causes washer  119  to be pushed rearward with respect to forward coupler  20 , thereby causing piston rod  73  and piston head  74  to move rearward with respect to master brake cylinder  72 , and consequently, pressurizing the hydraulic brake fluid in master brake cylinder  72 . Thus, during normal deceleration the trailer&#39;s brakes are smoothly applied due to the compression of coil spring  116 . However, in the event of rapid deceleration of the towing vehicle rear housing  40  will move rapidly forward with respect to forward coupler  20  necessitating the need for the trailer&#39;s brakes to be quickly applied. Thus, when rear housing  40  moves far enough forward washer  119  is abutted against tube  120 , thereby preventing piston rod  73  from sliding further forward, and consequently, actuating the trailer&#39;s brakes as rear housing  40  moves further forward. 
     Referring to FIG. 6, dampener cylinder  75 , dampener piston rod  76  and dampener piston head  77  are configured to cooperate in such a way so as to resist relative motion between forward coupler  20  and rear housing  40 . The rearward end of dampener cylinder  75  is closed except for restrictive aperture  81 . At the front end of dampener cylinder  75  is stopper  84  which is adapted to fit snugly within the front end of dampener cylinder  75  and, thereby, preventing hydraulic brake fluid from leaking out of dampener cylinder  75 . Stopper  84  has piston rod hole  85  formed therethrough aligned coaxial to dampener cylinder  75 , and adapted to receive dampener piston rod  76  snugly, so as to prevent hydraulic brake fluid from leaking out of dampener cylinder  75 . 
     Referring to FIGS. 3 and 6, dampener piston rod  76  extends from beyond base leg  31  through dampener piston rod coupling hole  35  through piston rod hole  85  of stopper  84  to dampener piston head  77  and is rigidly affixed thereto. Dampener piston rod  76  is threaded and is rigidly affixed to base leg  31  by tightening opposed nuts  78  around base leg  31 . 
     Referring to FIG. 6, dampener piston head  77  essentially divides dampener cylinder  75  into two chambers, fore chamber  82  and aft chamber  83 , each chamber being in communication with reservoir  71  by restrictive apertures  80  and  81 , respectively. When the towing vehicle decelerates, rear housing  40  moves forward with respect to forward coupler  20 , and consequently, so does dampener cylinder  75 . Dampener piston head  77  is rigidly affixed to dampener piston rod  76 , which is rigidly affixed to base leg  31 , and thus, as dampener cylinder  75  moves forward relative to forward coupler  20  hydraulic brake fluid in aft chamber  83  is pressurized and in fore chamber  82  a vacuum is created. In response to the pressure differential between hydraulic brake fluid reservoir  71  and fore chamber  82  and aft chamber  83 , caused by the contraction of trailer hitch mechanism  10 , hydraulic brake fluid is transferred from aft chamber  83  to reservoir  71  and from reservoir  71  to fore chamber  82  via restrictive apertures  80  and  81 . While trailer hitch mechanism  10  is extending, due to acceleration of towing vehicle  6 , hydraulic brake fluid is transferred from fore chamber  82  to reservoir  71  and from reservoir  71  to aft chamber  83 . The transfer of hydraulic brake fluid between the reservoir  71  and the dampener cylinder  75  via restrictive apertures  80  and  81  dampens the relative motion of rear housing  40  with respect to forward coupler  20 . 
     The integrated braking-dampening apparatus  70  provides an important safety feature over a device having separate braking apparatus and dampening apparatus. A person using a vehicle to tow a trailer having a separate braking apparatus and a separate dampening apparatus will not be able to determine whether or not there is hydraulic brake fluid in the reservoir during normal acceleration/deceleration. Even when the hydraulic brakes are not functional, due to a lack of hydraulic brake fluid, the separate dampener continues to operate. Under normal operation, non-emergency stopping, the dampener gently resists the relative motion of forward coupler  20  and the rear housing  40 , and consequently there is little or no jarring impact, because the axle bolts  60  and  61  do not slam into the ends of axle slots  27  and  28 , respectively. Whereas, in the instantaneous invention, the reservoir is in separate communication with both the master brake cylinder  72  and the dampener cylinder  75 . Therefore, if there is no hydraulic brake fluid, then the dampener is no longer operable, and even a gentle deceleration, or acceleration, will result in a jarring impact when the axle bolts  60  and  61  slam into the ends of axle slots  27  and  28 , respectively. Upon hearing and/or feeling the impact the operator of the vehicle is alerted to the fact that the reservoir no longer contains an adequate amount of hydraulic brake fluid, and that the trailer&#39;s brakes are inoperable. Thus, even when the operator fails to regularly check the hydraulic brake fluid in the reservoir, as is frequently the case, the integrated brakingdampening apparatus  70  alerts the operator to the lack of hydraulic brake fluid under normal operating conditions. 
     Referring to FIG.  3  and FIG. 4, hitch assembly  10  includes a self-actuated safety device  110  for applying the trailer&#39;s brakes responsive to the forward coupler  20  becoming disconnected from ball  6  during towing. The safety device  110  includes a safety cable  111 , safety actuating plate  90 , washer  119  and coil spring  116 . Cable  111  has a first end  112 , a second end  113 , and is longitudinally flexible and has an S-hook  114  attached to the first end  112  for attaching to the towing vehicle and plug  115  attached to the second end  113  for attaching to safety actuating plate  90 . In this implementation, proximal to the front end  41  of second side wall  45  of rear housing  40  is cable opening  53  formed therethrough for receiving safety cable  111 . When in operable position cable  111  extends from the towing vehicle through cable opening  53 , around the rear end of reservoir  71  to safety actuating plate  90 . Safety actuating plate  90  is configured so as to couple with cable  111 , as will be described herein below. 
     Reservoir  71  is configured so as to have sides  87  extending generally parallel to the side walls  44  and  45  of rear housing  40 , curved rear end  88 , and ledge  89  extending generally perpendicular from the bottom portion of reservoir  71 . Ledge  89  is configured so that cable  111  can be placed thereon. 
     Referring to FIGS. 7A-7C, safety actuating plate  90  is typically formed from a strip heavy-duty sheet metal, generally rectangular in shape, which is then pressed into a shape having a flat vertical portion  91 , and a bent upper portion  92 . Flat vertical portion  91  has a hole  117  formed therethrough for receiving tube  120 . Safety actuating plate  90  is mounted on tube  120  and rigidly affixed thereto by means such as welding. Bent upper portion  92  is first bent backward and downward such that first bend  93  forms an acute angle between the proximal end of upper portion  92  and the flat vertical portion  91 . The distal end of upper portion  92  is then bent at second bend  94  such that the distal end extends from second bend  94  generally upward and thereout. 
     Between first bend  93  and second bend  94  a first hole  95  is formed therethrough, which is in communication with a slot  96 , which is formed therethrough, and which extends from the hole  95  to first bend  93  and extends theredown along a portion of flat vertical face  91 . At second bend  94  a second hole  97  is formed therethrough for receiving a head of screwdriver, or other such tool. 
     Referring to FIGS. 2,  3  and  7 A- 7 C, safety cable  111  is placed in operable position in the following manner. Plug  115  is aligned beneath hole  95  and inserted therethrough and then positioned against flat vertical face  91 . S-hook  114  is then pulled backward, and around curved reservoir end  88 , and through cable opening  53 , such that a portion of cable  111  rests upon ledge  89 . Plug  115  is rigidly affixed to safety cable  111  and is of greater diameter than hole  95  and slot  96 . Thus, when the first end  112  of safety cable  111  is pulled forward, plug  115  is pulled backward and the force is transmitted to safety actuating plate  90 , causing safety actuating plate  90  to move backward and consequently actuating the brakes of the trailer, as will be described hereinbelow. 
     Referring to FIG. 4, top wall  23  of forward coupler  20  has a spring hole  29  formed therethrough for receiving a brake latch which is in the form of an inverted L-shaped spring  98  for latching behind safety actuating plate  90  when safety actuating plate  90  is pulled rearward by safety cable  111 . Inverted L-shaped spring  98  is generally formed from a strip of resilient metal having a shoulder  99 , an arm  100  extending generally horizontal from shoulder  99 , and a leg  101  extending generally vertical from shoulder  99  with a hoop  102  distal from shoulder  99 . Base leg  31  has a slot  36  formed therethrough for receiving arm  100  of inverted L-shaped spring  98 . When inverted L-shaped spring  98  is in operable position, leg  101  extends down into hole  29  with shoulder  99  extending down to top wall  23 , and arm  100  resting on top wall  23  generally parallel to sides  26  and  28 . Arm  100  extends from shoulder  99  through slot  36  with a portion of arm  100  extending beyond base leg  31 . The portion of arm  100  that extends beyond base leg  31  is rigidly affixed to top wall  23  by means such as welding or riveting. Safety actuating plate  90  is configured such that there exist a gap between top wall  23  and the bottom safety actuating plate  90 , the gap being less then the height of the shoulder of the inverted L-shaped spring  98 . When safety actuating plate  90  is pulled backward by safety cable  111 , safety actuating plate  90  engages shoulder  99  of inverted L-shaped spring  98 , pushing leg  101  further into spring hole  29 . After safety actuating plate  90  has been pulled past shoulder  99 , inverted L-shaped spring  98  snaps back into place, thereby preventing safety actuating plate  90  from moving back towards base leg  31 . The relative rearward motion of safety actuating plate  90  causes tube  120  to be pushed against washer  119 , thereby pushing washer  119  rearward which in turn causes piston rod  73  to be pushed rearward. The rearward motion of piston rod  73  actuates the trailer&#39;s brakes. Coil spring  116  remains compressed between safety actuating plate  90  and washer  119  for as long as safety actuating plate  90  is latched by inverted L-shaped spring  98 . Thus, in the event of the forward coupler  20  becoming detached from ball  6  safety cable  111  working in cooperation with inverted L-shaped spring  98  latches safety actuating plate  90 , thereby actuating the brakes of the trailer, and the brakes continue to applied while safety actuating plate  90  is locked by inverted L-shaped spring  98  even if safety cable  111  breaks thereafter. 
     Referring to FIG. 1, first sidewall  24  of forward coupler  20  and first side wall  44  of rear housing  40  have aligned release holes  37  and  54  formed therethrough, respectively. In order to release the trailers brakes when safety actuating plate  90  is locked into actuated position by inverted L-shaped spring  98  a screwdriver, or other such implement, is inserted into release holes  37  and  54 , such that the screwdriver head is inserted into hoop  102  of the inverted L-shaped spring  98 , and then the inverted L-shaped spring  98  is pulled downward so that the shoulder  99  no longer restrains safety actuating plate  90 . In response to inverted L-shaped spring  98  being pulled down, safety actuating plate  90  is pushed back against base leg  31  by compressed coil spring  116 . 
     Occasionally, it is necessary to bleed air out of the hydraulic brake line. This is typically done by pressurizing the hydraulic brake fluid in master brake cylinder  72 , and then relieving the hydraulic pressure from a valve near the trailer&#39;s brakes. The instantaneous invention provides an easy means for pressurizing and pumping the hydraulic brake fluid in master brake cylinder  72 . 
     Referring to FIG.  2  and FIGS. 7A-7C, top wall  43  of rear housing  40  has a brake priming opening  51  formed therethrough for receiving the head of a screwdriver, or other similar implement. Brake priming opening  51  is proximal to the front end  41  of rear housing  40 , such that when rear housing  40  and forward coupler  20  are fully extended, as shown in FIG. 1, brake priming hole  51  is generally above upper portion  92  of safety actuating plate  90 . The head of a screwdriver is inserted into brake priming hole  51  and aligned with hole  97  which is formed in the valley of upper portion  95  of safety actuating plate  90 . Thus, the sides of the valley can be used to guide the head of the screwdriver into hole  97 . With the blade of the screwdriver, or other such implement, properly inserted into hole  97  the master brake cylinder  72  is primed by moving the screwdriver head back and forth, thereby moving safety actuating plate  90  and brake piston rod  73  back and forth. The back and forth motion of piston head  77  primes master brake cylinder  72 , and thus pressurizes the hydraulic brake fluid in master brake cylinder  72 . 
     The term “housing” has been used to designate the support structure for enclosing and supporting the master brake cylinder and dampener; however, the housing can be other shapes suitable for mounting the master brake cylinder and dampener to the tongue of the trailer. Also, the master cylinder and dampener can be mounted either in the trailer tongue or the structure of the forward hitch, as long as they can respond to the relative movement of these elements. The master cylinder and dampener have been disclosed as being mounted in parallel inner connection between the forward hitch and rear housing; however, these elements can be mounted in tandem, if desired. 
     The opening  79  for entry and exit of the brake fluid of the master cylinder and the openings  80  and  81  of the dampener can be of different size or vertically offset with respect to each other or of other configuration so that as the brake fluid is progressively depleted in the reservoir the dampener is starved of brake fluid before the master cylinder is starved. This results in the dampening function being lost before the braking function is lost. The loss of the dampening function before the loss of the braking faction results in the operator of the towing vehicle detecting the jarring between the forward hitch and the rear housing, and therefore detecting the need for replenishing the brake fluid before the master cylinder loses its function. 
     Although a preferred embodiment of the invention has been disclosed in detail herein, it will be obvious to those skilled in the art that variations and modifications of the disclosed embodiment can be made without departing from the spirit and scope of the invention as set forth in the following claims.