Abstract:
A sensor bracket that isolates a sensor from mechanical vibrations of an associated component extends the operational lifetime, for example, of a wheel-mounted sensor on a vehicle. The bracket includes a multi-legged bracket to decrease the dynamic instability induced by using highly compliant isolating elements on a rotating wheel. Multiple isolating elements provide a reduction in the vibration impinging on a sensor while still maintaining rotational stability of the assembly on the wheel. In some aspects, an intrinsic, fail-safe feature is included in the sensor mounting bracket and isolating element design.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. provisional patent application No. 61/029,414, filed on Feb. 18, 2008 entitled “Apparatus for Isolating a Sensor From Vibration,” the entire disclosure of which is incorporated herein by reference. 
     
    
     FIELD 
       [0002]    The present invention is related to mechanically isolating vehicle sensors from vehicle vibrations, and, more specifically, an isolation bracket that isolates a vehicle sensor from vibrations of the vehicle. 
       BACKGROUND 
       [0003]    Vehicle sensors are often mounted to vehicle components such that information directly related to the associated component may be relayed to an interested party. For example, odometers may be placed on a wheel hub to measure the revolutions of the associated wheel. The measured revolutions, along with information related to the wheel diameter, may be used to calculate a distance traveled by the associated wheel, and therefore a distance traveled by the associated vehicle. Such a device is well known, and is commonly referred to as a hubodometer. A hubodometer is one example of a sensor that may be mounted to a vehicle. Other types of sensors or devices may also be attached to a vehicle, such as, for example, tire pressure sensors, weight sensors, temperature sensors, location sensors, and communications devices, to name but a few. 
       SUMMARY 
       [0004]    Embodiments disclosed herein provide a sensor bracket that isolates a sensor from mechanical vibrations of an associated component. Mounting brackets of various embodiments extend the operational lifetime, for example, of a wheel-mounted sensor on a truck, trailer or bus. Mounting brackets of various aspects accomplish this by protecting the mounted sensor from damaging shock and vibration. The sensor could be an electronic mileage counter such as an electronic hubodometer, a mechanical mileage counter such as a mechanical hubodometer, a tire pressure monitor, and/or a lubricant fluid sensor, to name a few. The shock and vibration impinging on a wheel-mounted sensor may result from poor road conditions such as potholes, washboard, gravel, expansion joints, and/or dislocations associated with the roadway. The shock and vibration impinging on a wheel-mounted sensor also may result from poor driving skill, resulting in excessive encounters with shoulder/centerline ‘rumble strip’ cut outs/protrusions, curbs, foreign objects, and the like. The shock and vibration impinging on a wheel-mounted sensor also may result from poor vehicle maintenance, resulting in, for example, excessive ‘wheel hop’ on braking. The shock and vibration impinging on a wheel-mounted sensor further may be the result of high levels of vibration generated by the internal gearing of the axle on which the sensor is mounted. In other vehicles, such as rail vehicles, vibration may result from axle gearing, track conditions, and the like. The present disclosure provides isolating mounting brackets that reduce the vibration transmitted to a vehicle sensor. In some embodiments, provided is a provision of a ‘fail-safe’ attachment method, which prevents the bracket and sensor assembly from being launched from the wheel during operation of the vehicle should a failure of isolating elements occur. 
         [0005]    Provided in various aspects of the present disclosure are: a sensor-mounting system, designed for the purpose of extending the operational life of a wheel-mounted sensor by protecting it from harmful shock and vibration; use of a multi-legged bracket to decrease the dynamic instability induced by using highly compliant isolating elements on a rotating wheel; implementation of wide temperature range, multiple isolating elements to provide a reduction in the vibration impinging on a sensor while still maintaining rotational stability of the assembly on the wheel; and/or implementation of an intrinsic, fail-safe feature in the sensor mounting bracket and isolating element design. 
         [0006]    In one aspect this disclosure provides a bracket for isolating a sensor from vibration, comprising: (a) a sensor mount adapted to receive a sensor; (b) a plurality of legs extending from the sensor mount; and (c) an isolating element that engages with a distal end of each leg and adapted to receive an attachment element that secures the respective leg, through the isolating element, to a wheel hub. The sensor mount, in an embodiment, comprises a plate having a mounting hole therein that is adapted to receive a sensor. The sensor mount may also include tabs extending from the plate that cover a portion of a sensor when mounted to said plate and provide a shield for the sensor. The plurality of legs, in an embodiment, include holes that receive said isolating elements. The isolating elements may be formed of silicone rubber elements that are substantially cylindrical and include a reduced diameter slot that is captured by a matching hole a respective leg. The isolating elements also include, in some embodiments, a spacer that is inserted into the center thereof. The isolating elements are adapted to receive an attachment bolt used for securing the leg to a wheel hub. The isolating elements may also be molded directly onto said legs, and may include a spacer molded into the material of the isolating element. 
         [0007]    In another aspect, provided is a bracket for isolating a sensor from vibration, comprising: (a) a sensor mount adapted to receive a sensor; (b) a plurality of legs extending from the sensor mount; and (c) a dual stud isolator that engages with a distal end of each leg and adapted secure each leg to a vehicle wheel hub. The dual stud isolator may comprise a first threaded stud having an elastomeric element bonded thereto and a second threaded stud bonded to the elastomeric element opposite the first stud. The studs, in an embodiment, comprise hex bolts with the elastomeric element bonded to the hex head of the hex bolts. The bracket may also include a lanyard assembly coupling the first and second threaded studs of each dual stud isolator. 
         [0008]    A further aspect of the disclosure provides an apparatus for mounting a sensor to a vehicle, comprising: (a) a mounting plate that receives a sensor; (b) a securement assembly that secures the mounting plate to a vehicle; and (c) an isolation element coupled to the securement assembly between the securement assembly and vehicle. The securement assembly, in some embodiments, includes a plurality of legs that extend from said mounting plate. The mounting plate may comprise a plate and a plurality of tabs extending from the plate to at least substantially cover a portion of a sensor when mounted to the plate. The isolation element, in some embodiments, is substantially cylindrical and includes a reduced diameter slot that is captured by a matching hole in the securement assembly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0009]      FIG. 1  is a perspective view of a vehicle of one embodiment; 
           [0010]      FIG. 2  is a perspective view of an exploded mounting bracket assembly of an embodiment; 
           [0011]      FIG. 3  is a perspective view of an assembled mounting bracket assembly of the embodiment of  FIG. 2 ; 
           [0012]      FIG. 4  is a perspective view of an exploded mounting bracket assembly of another embodiment; 
           [0013]      FIG. 5  is a perspective view of an assembled mounting bracket assembly of the embodiment of  FIG. 4 ; and 
           [0014]      FIG. 6  is a perspective view of a mounting bracket of another embodiment. 
       
    
    
     DETAILED DESCRIPTION  
       [0015]    For a more complete understanding of this invention, reference is now made to the following detailed description of several embodiments as illustrated in the drawing figures, in which like numbers represent the same or similar elements. Various embodiments are described herein, with specific examples provided in many instances to serve to illustrate and discuss various concepts included in the present disclosure. The specific embodiments and examples provided are not necessarily to be construed as preferred or advantageous over other embodiments and/or examples. 
         [0016]    With reference to  FIG. 1 , a vehicle  20  is illustrated for one embodiment as a bus that may be used in public transit. While the vehicle  20  of  FIG. 1  is illustrated as a public transit bus, it will be readily understood that this example is for purposes of illustration and discussion, and that methods, systems and apparatuses of the present disclosure may be used for any type of vehicle, including, for example, automobiles, trucks, semi tractor/trailers, and school buses. Furthermore, the systems and apparatuses of the present disclosure may also be used with other types of vehicles, including rail vehicles, aircraft, and/or watercraft. In the embodiment of  FIG. 1 , an odometer  24  is mounted to a wheel hub  28  of a set of rear wheel  32 . Typically wheel  32  includes a set of dual wheels, although the present disclosure is equally applicable to any wheel configuration. Such an odometer  24  is often referred to as a “hubodometer,” and these devices are commonly used in situations where the mileage of the wheel  32  may not necessarily be tracked by an odometer within the vehicle  20  itself, and/or in situations where it is convenient to view a mileage reading without having to access an interior of the vehicle  20 . For example, in the example of buses used in public transit, it may be more efficient for personnel to view the mileage of a bus on such a hubodometer  24  rather than having to open a door to the bus, climb into the bus, read a mileage from an odometer on the interior instrument panel, exit the bus, and close the door. Furthermore, in many cases digital odometers on the instrument panel may not be active unless the vehicle is turned on, thus making such checking of mileage even more inefficient. The odometer  24  of the embodiment of  FIG. 1  includes a display  36  that displays the distance traveled, such as total miles since the odometer&#39;s  24  installation, of the vehicle  20 . Such an odometer  24  may record and output on display  36  the distance traveled since a particular event, such as vehicle  20  maintenance or wheel  32  replacement, instead of or in addition to the total distance recorded since the installation of the odometer. In the embodiment of  FIG. 1 , the odometer  24  is an electronic hubodometer that measures distance traveled according to a number of revolutions detected by an accelerometer within the hubodometer and a size of the wheel  32  that is programmed into the hubodometer. The odometer  24  may also include an RF circuit that operates to transmit an information signal modulated onto an RF signal that includes an identification for the odometer  24  and the current value of the distance that has been measured by the odometer  24 . 
         [0017]    Traditionally, a solid metallic flat or formed (commercial steel with rust resistant treatment or stainless steel) bracket is used to attach an odometer to the wheel end of the vehicle or trailer. This bracket is rigidly mounted to the wheel, utilizing the existing hubcap bolts, drive axle cover-plate retainer bolts, or, in some cases, the actual lug nuts that attach the wheel to hub. The present disclosure recognizes that the mounting techniques just described provide little, if any, attenuation of the shock/vibration transmitted from the wheel to an odometer. It is recognized that such shock/vibration may have a detrimental effect on a hubodometer, or any other type of sensor associated with a wheel end, including failure of the component. The present disclosure provides for the shock/vibration transmitted to the sensor to be reduced to a level that is within a sensor&#39;s fragility limit. To achieve reduced shock and vibration impinging on the sensor, a bracket, as will be described in more detail for some exemplary embodiments, is mounted to the wheel end utilizing isolating elements such as elastomeric (elastomeric refers to a relatively highly pliable material or rubber-like substance, such as neoprene or silicone-based rubber) elements. The assembly is designed so that the vibration from the hub to the bracket and sensor must be transmitted through the isolating element to the sensor and bracket. The isolating elements and bracket combination is designed, in various embodiments, to tailor the mechanical resonances so that they do not occur in close proximity (in the frequency domain) to the operational vibration frequencies in the axle. 
         [0018]    As mentioned above, vehicles, as they travel over roadways, rails, etc. may experience a variety of different vibrations. Such vibrations may be caused by roadway surfaces, environmental factors such as wind, and/or by the vehicle itself as different mechanical components of the vehicle operate and generate vibration. For example, some vehicles have planetary gearing that is located at the end of a vehicle axle, which may cause vibrations in the wheel hub. Other drive train components may cause vibration as well, such as the engine and transmission. Various embodiments disclosed herein provide an isolation bracket that operates to isolate vibrations from a sensor. 
         [0019]    In one embodiment, illustrated in  FIGS. 2 and 3 , a hubodometer (not shown) may be mounted to a bracket  100  via a sensor mount  104  that in the embodiment of  FIGS. 2 and 3  is a center, ½ inch diameter hole, using a standard washer and locknut (not shown). The bracket  100  is mounted to a axle hub cover plate  108 , the cover plate  108  being associated with a wheel hub of a vehicle (not shown). The bracket  100  is isolated from vibrations of the wheel hub through isolating elements  112 , which in the embodiment of  FIGS. 2 and 3  are four silicone rubber, single-piece, elastomeric elements  112  that are inserted into associated holes  116  in the bracket  100 . A spacer  120  is inserted into the center of each of the isolating elements  112 . The assembly is secured to the cover plate  108  using an attachment bolt  124  and a washer  128 . In the embodiment of  FIGS. 2 and 3 , four, longer length bolts  124  and larger OD washers  128 , the assembly is mounted in the specified manner on the cover plate  108 . The associated wheel hub may be associated, for example, with a MAN planetary gear reduction axle, which is used in a large percentage of New Flyer, 40 foot transit buses. In an exemplary embodiment, the elastomeric element  112  is a single-piece design, molded from silicone or neoprene rubber. The element  112  has a reduced diameter slot that is captured by a matching hole  116  in the bracket  100 . In other embodiments, isolating elements may be molded directly onto the bracket, thereby becoming an integral part of the bracket. Additionally, other embodiments may have the steel spacer molded into such an isolating element when the isolating element is molded directly onto the bracket, thereby forming a bracket assembly that would require fewer individual parts to assemble when mounted to a vehicle. 
         [0020]    Another embodiment of an isolating bracket is illustrated in  FIGS. 4 and 5 . In this embodiment, as will be described in more detail, an elastomeric element is created by bonding rubber directly to threaded studs. As illustrated in  FIGS. 4 and 5 , a hubodometer (not shown) may mounted to a bracket  200  via a sensor mount  204  that in the embodiment of  FIGS. 4 and 5  is a center, ½″ diameter hole, using the standard washer and locknut (not shown). The bracket  200  is mounted to a axle hub cover plate  208 , the cover plate  208  being associated with a wheel hub of a vehicle (not shown). The bracket  200  is isolated from vibrations of the wheel hub through a dual stud isolator  212 . In this embodiment elastomeric element  216  is created by bonding rubber directly to threaded studs. The studs may be, for example, off-the-shelf hex bolts. The hex head has the advantage of providing an easy method of tightening the fastener into the wheel hub on one end and then providing for nut attachment to the bracket  200  on the other end. This system is made fail-safe by adding a lanyard assembly  220  made from steel end pieces  224  and a lanyard  228  of Nylon or Kevlar, for example, that connects the end pieces  224 . The dual stud isolator  212  is assembled with the lanyard assembly  220  and the bracket  200  is secured with locknut  232  inserted into associated holes in the bracket  200 . The associated wheel hub may be associated, for example, with a MAN planetary gear reduction axle, which is used in a large percentage of New Flyer, 40 foot transit buses. 
         [0021]    Another embodiment of an isolating bracket is illustrated in  FIG. 6 . In this embodiment, a sensor such as a hubodometer (not shown) may mounted to a bracket  300  via a sensor mount  304  that in the embodiment of  FIG. 6  is a center, ½″ diameter hole, using the standard washer and locknut (not shown). The bracket  300 , similarly as described above, may be mounted to a axle hub cover plate associated with a wheel hub of a vehicle (not shown). The bracket  300  may be isolated from vibrations in a manner similar as described above, such as through elastomeric isolating elements that are inserted into associated holes  308  in the bracket  300 . In the embodiment of  FIG. 6 , tabs  312  are provided that provide protection to the sensor from foreign objects and/or road debris when the vehicle is in motion. The height of the tabs  312  is selected such that each tab  312  is higher than the height of the mounted sensor or hubodometer. In such a manner, any flying rocks, sticks, small and medium-sized mammals, etc. may be deflected by the tabs  312  and provide an additional degree of protection to the sensor. In this embodiment, the elastomeric isolating elements provide shock protection to the sensor in a similar manner as described above in that they provide isolation to the sensor from axle-borne shocks due to pot-holes and the other road hazards. 
         [0022]    In a still further embodiment, sensor vibration isolation is obtained by manufacturing the actual bracket from a high-damping material or laminate composite that substantially reduces the vibration transmitted to the sensor due to the energy absorbing damping in the bracket construction. Elastomeric elements need not be used in this embodiment, and the bracket is bolted directly to the hub. For example, the bracket material is made from Constrained Layer Damping (CLD) steel. This is a sandwich-type (laminated) construction where two layers of steel are bonded together with an high damping elastomeric layer in the center (similar to automotive windshield construction). The laminate, in other embodiments, may also be formed with multiple layers of steel and damping layers thereby creating more damping and higher structural rigidity. In yet another embodiments, the bracket is fabricated from aluminum, magnesium, injection molded plastic or carbon fiber-reinforced polymer that may be substituted for the steel components in the laminate construction. Bracket construction using a high damping material that has been described here would be inherently fail-safe, as separate isolating elements such as elastomeric elements are not required. 
         [0023]    While embodiments described herein are described with respect to a four-legged bracket that may be affixed to a vehicle wheel of an over the road vehicle, it will be understood that numerous other configurations and applications are within the scope of this disclosure. For example, as briefly mentioned above, isolation devices may be used in rail vehicle applications. In such applications, it may be desirable to provide vibration isolation in order to extend the lifetime of a sensor. In certain embodiments, a three-legged bracket with isolating elements for each leg may be affixed to a rail vehicle wheel in a similar manner as described above. Numerous other applications and configurations of brackets will be readily recognized by one of skill in the art. 
         [0024]    The previous description of the disclosed embodiments is provided to enable a person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.