Abstract:
A trailer hitching system ( 10 ) and method is provided for facilitating an operator&#39;s maneuvering of a towing vehicle hitch component ( 16 ) into alignment with a towed vehicle hitch component ( 18 ) to enable mechanical interconnection of the hitch components. The trailer hitching system ( 10 ) includes an alignment sensor ( 24 ) attached to either the towing vehicle ( 12 ) or the towed vehicle ( 14 ) for emitting a light beam over a field of view. A reflector ( 32 ) attached to the other of the towing vehicle ( 12 ) or the towed vehicle ( 14 ) is mounted at a predetermined location relative to the alignment sensor ( 24 ). The reflector ( 32 ) reflects a portion of the light beam emitted from the alignment sensor ( 24 ). An alarm ( 46 ) in the alignment sensor ( 24 ) emits an audible alarm in response to detecting a portion of the reflected light beam. The activation of the audible alarm indicates that the reflector ( 32 ) is within the field of view of the alignment sensor ( 24 ) and thereby the hitch components ( 16  and  18 ) are moving towards alignment.

Description:
TECHNICAL FIELD 
     This invention relates generally to trailer hitching systems and, more particularly, to an electronic sensor system for aligning a vehicle and a trailer in preparation for hitching. 
     BACKGROUND OF THE INVENTION 
     For many years now vehicles that are temporarily connected to trailers have been used to transport boats, off-road vehicles, lawn maintenance equipment, and other vehicles. Generally, a hitch assembly connected to the towing vehicle and trailer is employed to permit their interconnection. Aligning the hitch assembly of the towing vehicle with the hitch assembly of the trailer is often a time-consuming and frustrating endeavour. This is especially so when the trailer is so heavy that it cannot be moved by an individual to compensate for minor misalignments of the hitching assemblies. In response to the continued nuisance associated with attempting to align hitching components, numerous hitching system alignment aids have been developed. Examples of some of the more common approaches include, mirrors attached to the rear of the towing vehicle for providing a view of the hitch assemblies, cameras mounted to provide a video picture of the hitch assemblies, metal guide plates attached to the towing vehicle hitch assembly to force lighter trailers into alignment, and electronic sensor assemblies. Each of the prior art approaches falls short of providing an accurate, low-cost, portable, all-weather, easy-to-use hitching system. 
     Hitching systems employing mirrors generally are mounted to the rear of the towing vehicle and provide the vehicle operator a view of the hitch assemblies during the alignment operation. To be effective mirrors must typically be of the relatively large convex variety making storage difficult and replacement relatively costly. Additionally, mirrors require favourable viewing conditions; therefore night-time operation and bad-weather operation are problematic. 
     Camera assemblies that are used in hitching systems provide the operator with a video display to assist in the alignment of the hitch assemblies. In addition to usually requiring daytime operation and good weather, camera assemblies are very expensive and require time-consuming assembly and disassembly each time the hitching system is used. 
     Metal guideplates by their very nature are limited to use with the class of trailers wherein aligning the hitching assemblies is the least problematic. The guideplates are situated between a vehicle and the ball-hitch in the shape of a “V”. As the vehicle is backed-up, a slightly misaligned trailer hitch component will impact the guideplate and be guided in towards the ball-hitch. As the trailer hitch component is guided inward, the trailer pivots about its tires. Due to the necessity for shifting the position of the trailer, the guideplate system is limited to use with lighter weight trailers. Using guideplates with heavier trailers may lead to either the guideplate breaking away from the vehicle or the vehicle being shifted, placing undesirable lateral forces upon the vehicle wheels. 
     Conventional hitching systems that rely on electronic circuits employ sensor assemblies such as magnetically activated switches, autofocus assemblies, and light reflective assemblies. Generally, output signals from the various sensors are received by a processor, which calculates the relative distance from the towing vehicle to the towed vehicle and provides an output to the operator. To receive power, the processor and some of the sensor assemblies are typically wired to the towing vehicle power subsystem. Connecting to the vehicle power requires the system to be semi-permanently installed with an associated installation cost in addition to the cost of the electronic assemblies. 
     Therefore, it is desirable to provide a hitching system for facilitating an operator&#39;s maneuvering of a towing vehicle to align the vehicle hitch component with a trailer hitch component carried on a towed vehicle. Also, it is desirable for the hitching system to be operational during bad weather and at night. Additionally, a low-cost, portable system is desirable. It would also be desirable to provide a system that is operational with virtually all types of towing vehicles and trailers. 
     SUMMARY OF THE INVENTION 
     In accordance with the teachings of the present invention a trailer hitching system and method is provided for facilitating an operator&#39;s maneuvering of a towing vehicle hitch component into alignment with a towed vehicle hitch component to enable mechanical interconnection of the hitch components. The trailer hitching system includes an alignment sensor attached to either the towing vehicle or the towed vehicle for emitting a light beam over a field of view. A reflector attached to the other of the towing vehicle or the towed vehicle is mounted at a predetermined location relative to the alignment sensor. The reflector reflects a portion of the light beam emitted from the alignment sensor. An alarm in the alignment sensor emits an audible alarm in response to detecting a portion of the reflected light beam. The activation of the audible alarm indicates that the reflector is within the field of view of the alignment sensor and thereby the hitch components are moving towards alignment. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and advantages of the present invention will become apparent to those skilled in the art upon reading the following detailed description and upon reference to the drawings in which: 
     FIG. 1 is a perspective view partially showing the presently preferred embodiment of the electronic hitching system; 
     FIG. 2 is a perspective view partially showing a reflector and a proximity sensor attached to a towed vehicle; 
     FIG. 3 is a schematic diagram of an alignment sensor constructed in accordance with the teachings of the invention; 
     FIG. 4 is a perspective view of an alignment sensor made in accordance with the teachings of the presently preferred embodiment of the invention; 
     FIG. 5 is a depiction of an alignment cone that projects from an alignment sensor; 
     FIG. 6 is an overview illustrating several factors that have an impact on alignment accuracy; 
     FIG. 7A is a perspective view of a proximity sensor constructed in accordance with the teachings of the presently preferred embodiment of the invention; 
     FIG. 7B is a perspective view of an alternative proximity sensor constructed in accordance with the teachings of the presently preferred embodiment of the invention; 
     FIG. 8 is a schematic diagram of a proximity sensor constructed in accordance with the teachings of the invention; 
     FIG. 9A is an overhead view of the presently preferred embodiment of the invention; 
     FIG. 9B is a first sectional view of the mounting arrangement of the proximity sensor; 
     FIG. 9C is a second sectional view of the mounting arrangement of the proximity sensor; and 
     FIG. 10 is an overhead view of an alternative embodiment of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, an exemplary electronic hitching system  10  is illustrated. The electronic hitching system  10  is designed to facilitate a vehicle operator in aligning the hitch components of a towing vehicle  12  and a towed vehicle  14 . Regardless of weather, lighting, or ground-surface conditions the hitching system  10  enables the vehicle operator to quickly and easily align the hitch components of the towing and towed vehicles  12  and  14 . In addition, the presently preferred embodiment is a wireless system, thereby minimizing the period of time required for assembly and increasing the portability and storability of the hitching system  10 . 
     The towing vehicle  12  includes a ferrous metal bumper assembly  20 , below which a towing vehicle hitch component  16  mounts. In the presently preferred embodiment, the towing vehicle hitch component  16  is a ferrous-metal hitch-ball although other types of hitch components are within the scope of the invention such as non-metallic hitch components and ball-receivers. Attached to the bumper  20  of the towing vehicle is an alignment sensor  24  for detecting the presence of the towed vehicle  14  and providing an audible alarm to the vehicle operator. The alignment sensor  24  detects the presence of the towed vehicle  14  by transmitting a beam of light outward from the rear of the towing vehicle  12  and detecting a portion of the beam of light that reflects from the towed vehicle  14 . The alignment sensor  24  is located approximately above the towing vehicle hitch component  16 , although other mounting locations are within the scope of the invention as will be described later. In the presently preferred embodiment the alignment sensor  24  is attached to the towed vehicle  14  by means of a magnet  25  that is affixed to the alignment sensor  24 , however using other means of attachment are within the scope of the invention including bolts and Velcro tape. Additionally, providing a bracket for extending the alignment sensor  24  out from the bumper  22  such as to a position directly over the towing vehicle hitch component  16  is within the scope of the invention. 
     Referring to FIGS. 3 and 4, schematic and perspective views respectively of the alignment sensor are illustrated. The alignment sensor  24  includes a photo-switch assembly  38  for transmitting a beam of light over a predetermined field of view and receiving a reflected portion of the beam of light. The photo-switch assembly  38  is preferably an infrared, echo mode, retro-reflective photo-switch such as an Allen-Bradley 42SMU7601 having a field of view of 5 degrees and an effective operating distance of approximately 8 feet. However, the scope of the invention includes photo-switches that operate from visible red through infrared with a field of view approaching 90 degrees. The photo-switch assembly  38  includes a light detect switch  44  that is controlled in response to reflected light being detected. Although in the preferred embodiment the light detect switch provides a constant output for detected light exceeding a predetermined intensity, it is within the scope of the invention to employ a photo-switch assembly that provides a light detect switch output that is proportional to the intensity of the detected light. A battery  40  and control switch  42  connect in series with the photo-switch assembly  38  to provide controlled circuit power to the alignment sensor  24 . An alarm  46  connected to the output of the light detect switch  44  provides an audible indication when the photo-switch assembly  38  detects reflected light. 
     Referring to FIGS. 1 and 2, the towed vehicle  14  includes a towed vehicle hitch component  18  attached to a ferrous-metal trailer tongue  22  for permitting the towed vehicle  14  to be hitched to the towing vehicle  12 . In the presently preferred embodiment, the towed vehicle hitch component  18  is a ferrous-metal ball-receiver, although employing the hitching system with other hitch components such as non-metallic hitch components and hitch-balls is within the scope of the invention. An adjustment shaft  26 , crank  28 , and wheel assembly  30  attached to the trailer tongue provide a support point when the trailer is disconnected from the towing vehicle. 
     In the presently preferred embodiment a retro-reflective reflector  32  is attached to the towed vehicle such that incident light emitted from the alignment sensor  24  is reflected back towards the towing vehicle along a path that is parallel to the incident light. Although a 1½″ wide retro-reflective reflector is employed in the presently preferred embodiment, using other reflectors and other widths of reflectors are within the scope of the invention. The reflector  32  employed in the presently preferred embodiment is attached to the forward portion of the adjustment shaft  26 , although other locations on the towing vehicle are within the scope of the invention so long as a suitable mounting relationship is maintained between the reflector  32  and the alignment sensor  24 . 
     A suitable mounting relationship is maintained by arranging the alignment sensor  24  and the reflector  32  such that an axis drawn through them runs parallel to an axis drawn through the hitch components  16  and  18  when they are in cooperative alignment. With reference to FIGS. 5 and 6, the effect of mounting relationship upon alignment accuracy is illustrated. The elements that define the accuracy of alignment include the field of view of the alignment sensor  24 , the width of the reflector  32 , the distance to the back that the reflector  32  is mounted from the towed vehicle hitch component  18 , and the distance to the side that the alignment sensor  24  and reflector  32  are offset from the vehicle hitch components  16  and  18 . Referring to FIG. 5, an alignment cone associated with the hitching system  10  is illustrated. The narrower the width of the reflector and the alignment sensor field of view, the narrower the alignment cone, and thereby the greater the alignment accuracy. However, reducing the reflector width and field of view to the minimum values would result in a thin pencil beam of light which would make it difficult for the vehicle operator to keep the reflector  32  within the alignment sensor field of view and thus make it very difficult to discern which direction to maneuver the vehicle  10  to attain alignment (see alignment sensor  24 ′). In the presently preferred embodiment, the alignment sensor field of view is approximately 5 degrees and the reflector width is about 1½ inches. This establishes a sufficiently wide alignment cone to enable the vehicle operator to reliably maneuver the vehicle  10  into alignment (see alignment sensor  24 ″). With reference to FIG. 6, the effect on alignment accuracy of the reflector mounting distance from the hitch component  18  is illustrated. The reflector  32  is depicted in two mounting positions, d1 (reflector  32 ′) and d2 (reflector  32 ″), relative to the towed vehicle hitch component  18 ′ and  18 ″. As the distance of the reflector mounting position from the hitch component  18  increases, the alignment accuracy decreases due to an increased spread of the field of view. To minimize the inaccuracy related to the reflector mounting distance, the width of the reflector is decreased, reducing the offset from the edge of the field of view, which increases the alignment accuracy. Increased sideward offset distance has no effect on alignment accuracy when the towing vehicle and towed vehicle are square relative to each other, but sideward offset distance decreases the alignment accuracy if the vehicles are not square. To eliminate alignment inaccuracy from sideward offset, the vehicle operator need only ensure that both vehicles are somewhat square as the hitch components near alignment. For optimum alignment, the alignment sensor  24  has a narrow field of view, for example approximately 5 degrees, and is attached directly over the towing vehicle hitch component  16 , the reflector  32  is approximately 2 inches wide and attached directly over the towed vehicle hitch component  18 . However, acceptable performance is obtained by maintaining the previously described suitable mounting relationship. 
     Again referring to FIGS. 1 and 2, the towing vehicle includes a proximity sensor  34  attached to the trailer tongue  22 . The proximity sensor  34  is mounted to the side of the towed vehicle hitch component  18  to permit detection of the towing vehicle hitch component  16  as it passes under the towed vehicle hitch component  18 . In the preferred embodiment, the proximity sensor  34  is preferably attached to the trailer tongue  22  by means of a magnet  36  that is affixed to the proximity sensor  34 . However, other means of attaching the proximity sensor  34  to the trailer  14  are within the scope of the invention, such as with bolts, Velcro, and adhesives. Although, the proximity sensor  34  of the present embodiment is rigidly affixed to the trailer tongue  22  with a magnet, it is within the scope of the invention to provide an adjustment means for the field of view to compensate for uneven mounting surfaces. For example, the detector assembly  50  may be adjustable with respect to the proximity sensor  34 , or the magnet  36  may be affixed to the proximity sensor  34  with a mounting apparatus such that the sensor  34  is adjustable relative to the magnet  36 . 
     Referring to FIGS. 7A and 8, a perspective view and schematic respectively of the proximity sensor are illustrated. The proximity sensor  34  includes a detector assembly  50  for detecting the presence of metal within a predetermined distance. The detector assembly  50  is preferably an infrared, echo mode, standard diffuse photo-switch such as an Allen-Bradley 42SMP7601. However, the scope of the invention includes inductive and magnetic metal detectors such as an Allen-Bradley 871F (see FIG.  7 B), as well as ultrasonic sensors such as an Allen-Bradley 873C. The photo-switch version of the detector assembly  50  transmits a beam of light over a 6 degree field of view and detects portions of the light that are reflected off of any object within approximately 12 inches. The detector assembly  50  includes a detect switch  52  that is controlled in response to detecting light reflected from the towing vehicle hitching component  16 . A battery  54  and control switch  56  connect in series with the detector assembly  50  to provide controlled circuit power to the proximity sensor  34 . An alarm  58  connected to the output of the detect switch  52  provides an audible warning when the detector assembly  50  detects the presence of an object within the field of view. 
     The presently preferred embodiment of the electronic hitching system  10  has two phases of operation, the alignment phase and the hitch component detection phase. Referring to FIG. 9A, prior to the alignment phase an alignment sensor  24 , proximity sensor  34 , and reflector  32  are mounted to the towing vehicle  12  and towed vehicle  14 . The alignment sensor  24  is magnetically attached to the towing vehicle bumper assembly  20  to provide a beam of light having a field of view that extends outward over the towing vehicle hitch component  16 . The reflector  32  is semi-permanently attached to an adjustment shaft  26  of the towed vehicle  14  to reflect the beam of light back towards the alignment sensor  24 . The proximity sensor  34  is magnetically attached to the side of the towed vehicle trailer tongue  22  in order to sense the towing vehicle hitch component  16  passing under the towed vehicle hitch component  18 . 
     With continued reference to FIG. 9A, during the alignment phase, as the vehicle operator slowly backs the towing vehicle  12  towards the towed vehicle  14  the alignment sensor  24  emits an audible beep so long as the reflector  32  is within the field of view of the alignment sensor  24 . The alignment sensor  24  emits a beam of infrared light over a field of view of about 5 degrees. When the towing vehicle is maneuvered to bring the alignment sensor  24  within about 5 feet of the reflector  32 , light emitted from the alignment sensor  24  reflects from the reflector  32  back along a path parallel to the incident light towards the alignment sensor  24 . The photo-switch assembly  38  within the alignment sensor  24  detects the reflected light and in response controls the light detect switch  44  to supply power to an alarm  46 . The alarm  46  provides a constant audible indication that reflected light is detected. Although the preferred embodiment is limited to distances of 5 feet, the scope of the invention includes greater distances that are obtained by higher power photo-switch assemblies  38 . As the towing vehicle  12  nears the towed vehicle  14  the alignment cone narrows in width, leading the hitch components  16  and  18  towards alignment. By constantly adjusting the direction of the towing vehicle  12  to maintain the audible alarm and thereby remain within the alignment cone, the vehicle operator brings the hitch components  16  and  18  towards alignment. The alignment sensor alarm  46  continues to provide an audible alarm as the towing vehicle hitch component  16  passes under the towed vehicle hitch component  18 . Although, in the presently preferred embodiment the alignment sensor audible alarm does not provide an indication of the relative distance between the hitch components  16  and  18 , it is within the scope of the invention to provide an alarm that changes audible characteristics depending on the intensity of the reflected light. Such an alarm is controlled by a photo-switch assembly  38  that provides a light detect switch output that is proportional to the intensity of reflected light that is received. Examples of audible characteristics include tone, pitch, and frequency of beeps. The changing audible characteristics provide an indication of the relative distance between the hitch components  16  and  18 . 
     Referring to FIGS. 9B and 9C in addition to FIG. 9A, the hitch component detection phase is illustrated. As the towing vehicle hitch component  16  begins to pass under the towed vehicle hitch component  18 , the hitch component detection phase begins. The proximity sensor  34  emits a beam of light over a field of view that extends approximately perpendicular to the towed vehicle hitch component  18 . As the towing vehicle hitch component  16  passes underneath the towed vehicle hitch component  18 , the beam of light is reflected off of the hitch component  18  back towards the proximity sensor  34 . The photo-switch  50  within the proximity sensor  34  detects the reflected light and in response controls the light detect switch  52  to provide power to the audible alarm  58 . In the presently preferred embodiment the proximity sensor audible alarm  58  emits a different sound than the alignment sensor audible alarm  46 , however it is within the scope of the invention for audible alarms  46  and  58  to emit the same sound upon activation. The activation of the second proximity sensor audible alarm alerts the vehicle operator that the hitch components  16  and  18  are aligned. Should the vehicle operator back-up too far, the alarm will halt. Only when the towing vehicle hitch component  16  is in close proximity to the towed vehicle hitch component  18  does the proximity sensor alarm sound. 
     Referring to FIG. 10, another electronic hitching system  110  configured in accordance with the principles of the invention is illustrated. Hitching system  110  is similar to hitching system  10  in function with corresponding elements numbered in the range  110 - 199 . Hitching system  110  differs from hitching system  10  in that a proximity sensor is not included and the photo-switch assembly  138  of the alignment sensor  124  is an analog retro-reflective photo-switch operating in echo mode. The photo-switch assembly  138  transmits a beam of light over a predetermined field of view and receives a reflected portion of the beam of light. A light detect switch  144  included in the photo-switch assembly has an output that varies in response to the intensity of the reflected light being detected. A battery  140  and control switch  142  connect in series with the photo-switch assembly  138  to provide controlled circuit power to the alignment sensor  124 . An alarm  146  connected to the output of the light detect switch  144  provides an audible indication when the photo-switch assembly  38  detects reflected light. In this embodiment of the invention a variable tone alarm is employed, however the scope of the invention includes other alarms that vary an audible characteristic in response a varying output from the light detect switch  144 , examples of other such alarms include intermittent alarms that vary the duration of each beep and vary the frequency of beeps. 
     In operation, the embodiment of the electronic hitching system  110  has one phase of operation, the alignment phase. Referring to FIG. 5, prior to the alignment phase an alignment sensor  124  and reflector  132  are mounted to the towing vehicle  112  and towed vehicle  114 . The alignment sensor  124  is magnetically attached to the towing vehicle bumper assembly  120  to provide a beam of light having a field of view that extends outward over the towing vehicle hitch component  116 . The reflector  132  is semi-permanently attached to an adjustment shaft  126  of the towed vehicle  114  to reflect the beam of light back towards the alignment sensor  124 . 
     During the alignment phase, as the vehicle operator slowly backs the towing vehicle  112  towards the towed vehicle  114  the alignment sensor  124  emits an audible beep so long as the reflector  132  is within the field of view of the alignment sensor  124 . The alignment sensor  124  emits a beam of infrared light over a field of view of about 5 degrees. When the towing vehicle is manoeuvred to bring the alignment sensor  124  within about 5 feet of the reflector  132 , light emitted from the alignment sensor  124  reflects from the reflector  132  back along a path parallel to the incident light towards the alignment sensor  124 . Although the preferred embodiment is limited to distances of 5 feet, the scope of the invention includes greater distances that are obtained by higher power photo-switch assemblies  138 . The photo-switch assembly  138  within the alignment sensor  124  detects the intensity of the reflected light and in response controls the light detect switch  144  to supply power to an alarm  146 . The alarm  146  provides a variable audible indication that reflected light is detected. The tone of the audible indication is varied in response to the intensity of reflected light that is detected. As the towing vehicle  112  nears the towed vehicle  114  the alignment cone narrows in width, leading the hitch components  116  and  118  towards alignment. At the same time, the audible indication varies indicating to the vehicle operator that the relative distance between the hitch components  116  and  118  is decreasing. By constantly adjusting the direction of the towing vehicle  112  to maintain the audible alarm and thereby remain within the alignment cone, the vehicle operator brings the hitch components  116  and  118  towards alignment. The alignment sensor alarm  146  continues to provide an increasing audible alarm as the towing vehicle hitch component  116  passes under the towed vehicle hitch component  118 . The changing audible characteristic of the alarm  146  provides an indication of the relative position of the hitch components  116  and  118 . The vehicle operator halts the towing vehicle  112  when the audible alarm increases to a level that indicates the hitch components are in alignment. 
     The hitching system provides an adaptable universal system for aligning a towing vehicle hitch component with a towed vehicle hitch component. The system minimizes the myriad problems associated with backing up a motor vehicle to a trailer for hitching and towing. Additionally, weather, lighting, or ground-surface conditions do not affect the performance of the hitching system. The system is wireless, providing a highly portable system that installs instantly and is small enough to fit into a glove compartment for storage. Also, the system when configured with magnetic attachments, is instantly mountable to any ferrous-metal surface. For special cases where ferrous-metallic surfaces are not available, Velcro tape is easily adapted for mounting purposes. If the system is inadvertently left in place after hitching up the trailer, the attachment points are strong enough to secure the assemblies during subsequent travel. 
     It should be understood that while this invention has been described in connection with particular examples thereof, no limitation is intended thereby since obvious modifications will become apparent to those skilled in the art after having the benefit of studying the foregoing specification, drawings and following claims.