Patent Publication Number: US-10309824-B2

Title: Weight sensing vehicle hitch

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a conversion from U.S. Provisional Application No. 62/112,440 filed on Feb. 5, 2015. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     This invention relates to vehicle hitches and in particular to hitches that includes a sensor to provide the user with information on the load applied to the hitch. 
     Towing a trailer behind a vehicle may be dangerous if the weight of the trailer is improperly balanced or exceeds the intended design of the vehicle. Exceeding the rated towing capacity of a vehicle can result in a very dangerous driving condition in addition to potential damage to the vehicle. For instance, dangerous trailer sway can occur by loading a trailer such that the proper proportions of “tongue weight” to gross weight are not achieved. 
     However, current technology does not provide an easy or convenient mechanism for measuring the tongue weight of a trailer. In fact, the almost-universally suggested method for measuring the tongue weight of a loaded trailer involves the use of a conventional bathroom scale, a brick, and a piece of wood. Such an awkward and inconvenient method of measuring the tongue weight of a trailer is, unfortunately, the state of the art. 
     SUMMARY OF THE INVENTION 
     The invention is directed at the receiver unit which is inserted into the vehicle&#39;s receiver hitch assembly. The invention includes a load force sensing assembly to be placed beneath the receiver unit. The integral load sensor in the load force sensing assembly detects a force exerted on the receiver unit from the apparent weight of the tongue of a trailer placed on a trailer ball attached to the receiver unit. 
     In one aspect, the invention enables an apparatus comprising a load force sensing assembly adapted to sense a force exerted by the receiver unit resting in the vehicle&#39;s receiver hitch. The load force sensing assembly; and a signal component coupled to the load force sensing assembly and configured to output a signal substantially corresponding to the force. 
     In another aspect, the invention enables a sensor operative to detect a downward force imparted on a trailer hitch to which the trailer is attached while a trailer is coupled to the trailer ball and to convey the downward force through the receiver to a display mechanism. 
     In yet another aspect, the invention enables an apparatus for displaying the tongue weight of a trailer comprising a display having a coupling that is operative to couple to a trailer, the display being configured to output an indication of a tongue weight of a trailer while the trailer is coupled to the trailer ball based on a signal received from the trailer ball using the coupling. 
     In still another aspect, the invention enables a method for measuring tongue weight. The method includes detecting a downward force exerted by a trailer tongue on a trailer hitch with the trailer tongue coupled to the trailer hitch and outputting a signal that corresponds, at least in part, to the downward force. 
     Advantageously, embodiments of the invention enable a user to inspect the tongue weight of a trailer while the trailer is coupled to the trailer ball and without having to decouple the trailer from the trailer ball. In addition, weight can be redistributed on the trailer without decoupling the trailer from the trailer ball to achieve a desired tongue weight, which greatly simplifies the task of loading a trailer that is safe to tow. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         FIG. 1  shows a side view of a weight sensing vehicle hitch, vehicle bumper, and coupler; 
         FIG. 2  shows a detailed view of a hitch receiver and load force assembly; 
         FIG. 3  shows a side view of a load force assembly; 
         FIG. 4  shows a top view of a hitch receiver and load force assembly; 
         FIG. 5  shows a diagrammatic view of an embodiment of the invention; 
         FIG. 6  shows a diagrammatic view of an embodiment of the invention; 
         FIG. 7  shows a diagrammatic view of an embodiment of the invention; 
         FIG. 8  shows a side view of an alternative embodiment with a gooseneck trailer configuration, 
         FIG. 9  shows a top view of a the gooseneck trailer configuration of  FIG. 8 , 
         FIG. 10  shows the load force assembly of  FIG. 8 , 
         FIG. 11  shows the load force assembly of  FIG. 9  in a top view, 
         FIG. 12  shows a diagram of the calibration scheme for the sensors, 
         FIG. 13  is a graph showing the sensor signal to weight. 
         FIG. 14  is a graph showing the raw signal versus corrected signal with varied weights, and 
         FIG. 15  is a graph showing the sensor signal versus time at constant weights. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a side view of a hitch assembly  10  comprising a hitch receiver  12  attached to vehicle chassis  16 . The hitch assembly  10  further includes a load force assembly  20 . In some embodiments, the load force assembly  20  comprises at least one load sensor  22  (see  FIGS. 3 and 4 ), a first layer of protective material  24 , and a second layer of protective material  26 . The at least one load sensor  22  is sandwiched between the first layer of protective material  24  and the second layer of protective material  26 . The at least one load sensor  22  is attached to a computational assembly  28  that interprets the output from the at least one load sensor  22  and outputs the information so that it can be displayed to the operator. The computational assembly  28  may be powered via the vehicle&#39;s power supply (not shown), such as a 12V system, for example with connector  30 .  FIG. 1  shows the ball mount  34  slid into the hitch receiver tube  32  which is locked together by a pin through matching holes and secured with a hitch pin  42  and hairpin cotter  44 . 
     Power for the computational assembly  28  can be provided with a hardwired connection to the vehicle&#39;s OEM (original equipment manufacturer) wiring harness or via a plug-in connection into the vehicle&#39;s electrical system, for example located at the rear of the vehicle; power can also be provided to the computational assembly  28  using an internal power supply, such as a battery, which may be rechargeable, disposable, or of any other suitable variety. 
     A readout from the at least one load sensor  22 , for example via the computation assembly  28 , is provided to the operator so that the operator can determine how much load (weight) is placed on the hitch receiver  12  in real time. The readout can be provided to the operator in a variety of ways. For example, as illustrated in  FIGS. 5 and 6 , the operator can have a display in the cab of the vehicle and/or on the rear of the vehicle (e.g., bumper mount). In some embodiments, for example as shown in  FIG. 7 , the load information can be sent to the operator&#39;s cellular phone (e.g., smart phone), or other device, for example via WiFi, Bluetooth, or other wireless or wired interface. In some embodiments, a vehicle&#39;s OEM display is utilized to display the load information. Any other suitable display can be utilized. 
     As show in  FIG. 2 , in some embodiments, the second layer of protective material  26  of the load force assembly  20  rests on an interior surface of the hitch receiver tube  32 . The ball mount  34  ( FIG. 1 ) rests on top of the first layer of protective material  24  so that the tongue load of the trailer can be measured with the load sensor  22 , which is disposed between the first layer of protective material  24  and the second layer of protective material  26 . 
     In some embodiments, the first layer of protective material  24  and the second layer of protective material  26  extent beyond the distal end  36  of the load sensor  22 , as shown in  FIG. 3 , for example. As further shown in  FIG. 3 , the first layer of protective material  24  and the second layer of protective material  26  are curved downwardly at their distal ends so that the ball mount  34  can slide easily into the hitch receiver tube  32  and not catch on the distal end of the layers of protective material  24 ,  26 . The downward curve also serves an important function of ensuring the exact positioning in relationship to the front of the hitch tube of the load sensing portion  40 . In some embodiments, the total thickness of the load sensor  22 , first layer of protective material  24 , and second layer of protective material  26 , is 0.05″. This allows the ball mount  34  to slide easily into the hitch receiver tube  32 . Additionally, in some embodiments, the distance between the top surface of the first layer of protective material  24  and the lower lip  38  of the second layer of protective material  26  is ½. ″ The sensor assembly may also be designed to be used in a temporary placement manner. This version would have the power cord lead from the load sensor  40  coming out the front of the tube instead of the back. It would incorporate the functions of proper sensor positioning (mentioned above w/curve), protective covering of the connection point between the light sensor material and the heavier durable power cord to the computational assembly and facilitate the extraction of the assembly from the hitch tube. 
     With regard to  FIG. 4 , in some embodiments, one or both of the first layer of protective material  24  and the second layer of protective material  26  are 6¼″ in length, though other lengths are permissible. For example, depending upon the characteristics of the receiver tube  32  and load sensor  22 , for example, a length of between 3″ and 10″ may be used. In some embodiments, the load sensing portion  40  of the load sensor  22  is located 1″ from the distal end of the hitch receiver tube  32 . In some embodiments, the center of the load sensing portion  40  is located 1″ from the distal end of the hitch receiver tube  32 . The load sensing portion  40  can further be located in any desirable location along the length of the hitch receiver tube  32  (and relative to the first and second layers of protective material  24 ,  26 ), depending upon the hitch receiver  12  set-up. 
     The invention is also useful in gooseneck trailer configurations which utilize a “turnover ball” hitch mechanism. In such applications a hitch weight sensing device may be added to obtain the benefits discussed above. Gooseneck hitches such as shown in U.S. Pat. Nos. 6,447,000; 7,775,545, the disclosures of which are incorporated herein by reference, are mounted to the bed of a pickup truck and often allow the hitch ball to be lowered below the floor of the truck to permit full use of the bed of the truck. 
     In typical “gooseneck” hitches, the truck bed surface  50  has an opening through which a turnover ball  52  may be inserted. While the turnover ball  52  could simply be threaded into the truck bed, it is more typically inserted into an opening  56  formed in the truck bed frame  60 . In many arrangements, the frame is an added on unit mounted underneath the truck bed. In any event, the turnover ball  52  is inserted into the formed opening  60  and is typically secured with a pin (not shown) through a side opening  62  in the turnover ball and through the truck frame. This secures the turnover ball  52  from being removed unless intended. The opening  56  may include a load force assembly  66  which is inserted into the opening and held in place by upper limiting tabs  68  or the like. An opening  70  is formed for the pin to pass there through when secured to the turnover ball side opening  62 . 
     At the bottom  72  of the load force assembly a load sensor  74  is positioned. It may be protected by layers of protective material on one or both sides as discussed previously. Appropriate wiring  76  carries the signal to a computational assembly  80  for processing which is then transmitted via an OEM wire harness, Bluetooth, Wi-Fi or other means to be displayed in the vehicle with an in-cab display, phone screen or separate display. The load force assembly  66  is placed beneath the removable “turnover” ball on the weight bearing surface of the retention mechanism  82  designed to secure the turnover ball  52 . 
     The retention mechanism  82  is attached to the frame of the vehicle. 
     Trailer loads transmitted through the Gooseneck trailer configuration to the turnover ball mechanism in the vehicle will be measured and communicated to the user 
     Load Force Assembly  66 
         Picks-up the total load force traveling through the turnover ball  52  down to the retention mechanism  82 .   Up to four active force sensing areas that may be spaced equally around the perimeter of the load force assembly  66  are in the configuration as shown in  FIGS. 10 and 11 .   The four load force sensing areas of the load force assembly  66  send information to a computational assembly  80 .       

     Power may be provided to the “computational assembly” from the vehicle&#39;s electrical system in four ways: 
     1. Hardwire into the vehicle&#39;s OEM wire harness. 
     2. From either of the vehicles plug-ins located near or in the rear bumper specifically designed for providing electrical power to trailers. 
     3. Plugging into the trailer&#39;s power supply. 
     4. Battery located in the device&#39;s system. 
     The computational assembly  80  that provides the means to determine loads transmitted from the load force sensors  74  and send them to various users&#39; locations. i.e. drivers cab, rear bumper, or to a person operating an independent piece of equipment loading the trailer. It can be transmitted via either OEM wire harness, Bluetooth, Wi-Fi, or other electronic means. These signal can be displayed electronically on the vehicle&#39;s OEM in-cab-display, Smart phone screen, or separate display specifically designed for use with the invention. All means allow the user to view the actual load on the trailer hitch in real-time. 
     Load Force Assembly Method  1 
         Consists of durable material sufficient to secure the load force sensor in proper the position under the “turnover ball” while in use, also when not in use and the turnover ball is in a stored position, or if the “turnover ball” is removed completely from the retention mechanism  82 .   The load sensing electronic components of the hitch weight sensing device are secured to the “base portion” of the load force assembly  66 . The turnover ball  52  rests directly above the load sensors  74 .   The entire load force assembly  66  can be removed in the same manner as the turnover ball  52  by retracting the ball retention pin from the assembly.       

     Load Force Assembly Method  2 
         Consists only of the “base portion” with the load sensing electronic components secured to it. In this form, the load sensors  74  are simply adhered or otherwise affixed to the bottom of the retention mechanism  82 .       

     In some embodiments, the first and second layers of protective material  24 ,  26  are made from a metallic material, for example sheet steel or stainless steel. In some embodiments, the protective material thickness is increased specifically over the load sensor  40  to ensure accurate load force transfer. The first and second layers of protective material  24 ,  26  are secured to one another along their edges to prevent movement of the load sensor  22  within the load force assembly  20 . The first and second layers of protective material  24 ,  26  can be secured to one another in any suitable way, for example adhesively, rivets, spot welding, welding, etc. 
     In some embodiments, the first and second layers of protective material  24 ,  26  are made from a durable fabric material, for example epoxy impregnated Kevlar® brand aramid fiber, fiberglass, or carbon fiber. In some embodiments, the protective material thickness is increased specifically over the load sensor  40  to ensure accurate load force transfer. The first and second layers of protective material  24 ,  26  are secured to one another along their edges to prevent movement of the load sensor  22  within the load force assembly  20 . The first and second layers of protective material  24 ,  26  can be secured to one another in any suitable way, for example adhesively, thermal set epoxy, etc. One or both of the protective layers of material can further be made from any suitable material or combination of materials, alloys, composites, etc. 
     In some embodiments, the load force assembly  20  can be used with any class of hitch receiver  12 , for example class I &amp; II, III &amp; IV, V, and VI. 
     In some embodiments, the load force assembly  20  is integrated into the hitch receiver  12 . In some embodiments, the load sensor  22  is integrated into the ball mount  34  on its underside. In this way, an existing hitch receiver  12  would not need to be modified since the load sensors  22  can be on the ball mount  34 . In some embodiments, the load sensor  22  is located on the inside surface of the hitch receiver tube  32  and a layer of protective material is placed over the load sensor  22  such that the ball mount  34  can be located on top of the layer of protective material. 
     In some embodiments, the load force assembly  20  can be used as an aftermarket product or with an OEM hitch receiver  12 . In some embodiments, the load sensor  22  can be used as an aftermarket product or with an OEM hitch receiver  12 . 
     In some embodiments, the at least one load sensor  22  is a “FlexiForce™” sensor from Tekscan, Inc. of South Boston, Mass. Such sensors are described in U.S. Pat. Nos. 6,272,936 and 7,258,026, the disclosures of which are incorporated herein by reference. 
     The load sensors  22  provide an output from a load which needs to be converted to a value in pounds or kilograms. There are two main steps for this conversion. Step one is to compensate for the time-drift of the sensor. To do that we averaged several empirical measurements on different sensors to determine a “typical” drift curve. Those curves were taken under constant load, and the values are raw sensor values vs. time. Then we approximated that measured curve with a piecewise linear compensation function. The compensation function is subtracted from the raw sensor value in the smartphone before converting it to a weight. 
     The compensation function may be a single fixed function of time, representing an average over the sensors and conditions. It may also be a function of both weight and time and instead of being based on a piece-wise linear curve may be a polynomial whose coefficients are dependent on weight. 
     Next, the drift-compensated sensor value is converted to weight. For the sake of clarity, let&#39;s use the terms compensation (to remove time drift), conversion (from compensated signal to weight) and calibration (which generates input to the conversion formula). The need to apply linearization during this conversion step is pretty standard in any sensor measurement. As above, a 3-parameter polynomial may be used to make this conversion, but the coefficients may be measured during production so they are unique for each sensor. The coefficients will reflect the shape of the curve, and they may be scaled or otherwise manipulated to take into account the user calibration. 
     The computational assembly may do the math itself prior to sending the weight to the smartphone. Conversely, it may be done in an app on the phone so a) the calibration factors do not need to be sent from the phone down to the device, and b) the phone more readily deals with a situation where power is interrupted to the sensor during a measurement. 
       FIG. 12  shows a block diagram showing a calibration scheme showing that the information from the sensor is sent to the computational assembly (which may be wholly within the device or may use computational power from another device such as a smartphone using an app. The measurement value is then adjusted with compensation data to compare to factory and user calibrations. 
     Compensation: 
               x   0     =       x   i     +       ∑   k     ⁢         a   k     ⁡     (     t   -     t   0       )       k               
Conversion:
 
x 0 =a k x i   k  
 
       FIG. 12  shows how the raw sensor data may be taken to result in a displayed “hitch weight.” 
     The graph in  FIG. 13  shows the sensor signal to weight 
     The graph in  FIG. 14  shows the raw signal versus corrected signal with varied weights. The sensor detects the physical force transferred from the hitch. It is measured by an analog-to-digital converter (ADC) in the measurement block. The output of the measurement block is the raw uncompensated data, as shown above. 
     In the Compensation block the drift is corrected using the formula shown, where x i  is the input signal, x o  is the output signal, and they a k &#39;s are coefficients determined during the two calibration steps. At the output of this block, the signal is as represented by the red trace in the graph above. 
     In the Conversion block the signal is converted from units of millivolts to units of pounds or kg using the formula shown. Again x i  is the input signal, x o  is the output signal, and they a k &#39;s are coefficients determined now during only the user calibration. The scope of these variable names is local to the block, i.e. the a k &#39;s here are not the same as the ones in the compensation block. The output value x o  here is what is displayed on the smartphone app (or other user interface). 
     The graph in  FIG. 15  shows the sensor signal versus time at constant weights. 
       FIGS. 12-15  show that the sensors have drift and nonlinearity in the data which are being corrected for to provide a displayed “hitch weight.” 
     In each form of the invention, the standard trailer hitch and the gooseneck hitch in pickup beds, the load sensors detect the downward weight on the hitch and can display it so the user can act accordingly. If the weight is within limits nothing needs to be done and the user has the assurance that their weight is acceptable. If not, weight can be removed or adjusted on the trailer to decrease the tongue weight. 
     This completes the description of the preferred and alternate embodiments of the invention. Those skilled in the art may recognize other equivalents to the specific embodiment described herein which equivalents are intended to be encompassed by the claims attached hereto.