Abstract:
An axle lift system for a trailer may include: a moving block coupled to an axle of the trailer; a fixed block coupled to a frame of the trailer; a winch; and a cable, the cable communicating with the moving block, the fixed block, and the winch, the axle lift system configured to move the axle upon operation of the winch. In the event of a flat (or excessively low-pressure) tire, the operator can quickly and easily activate the axle lift system to raise an axle associated with the flat tire off the ground.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims of the benefit of U.S. Provisional Application No. 61/846,040, filed Jul. 14, 2013. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     The invention relates generally to an axle lift system for a wheeled vehicle, and more particularly, but without limitation, to an axle lift system that is configured for emergency use with multi-axle trailers. 
     2. Description of the Related Art 
     Camping trailers, boat trailers, and the like are in widespread use. Multi-axle variants are common on recreational and other types of trailers. One risk in towing such vehicles is the potential for a flat tire caused, for example, by a puncture. Continuing to drive with a flat tire is not preferable due to the potential for damage to the trailer and wheel. Accordingly, the conventional method for responding to a flat tire is to raise the axle (typically with a manually-operated scissor or hydraulic service jack), and then replace the wheel having the flat tire with a spare wheel and tire. This conventional approach has many shortcomings, however. For example, the operator may not be carrying a spare tire. And even if a suitable jack and spare tire are available, attempting such a procedure on the side of a road may be difficult, time consuming, and/or unsafe. 
     A more suitable apparatus and method is needed for responding to a flat tire, esp. for emergency use with a multi-axle trailer. 
     SUMMARY OF THE INVENTION 
     Embodiments of the invention seek to overcome one or more of the aforementioned limitations by providing an electrically-activated axle lift system that is preferably permanently affixed to each end of each axle of a multi-axle trailer. In the event of a flat (or excessively low-pressure) tire, the operator can quickly and easily activate the axle lift system to raise an axle associated with the flat tire off the ground. Such a system enables a more rapid tire change. Alternatively, the operator may be able to tow the trailer to a service center or at least a safer location (at an appropriate speed) with the tire in a raised state. 
     In an embodiment of the invention, an axle lift system for a trailer includes: a moving block coupled to an axle of the trailer; a fixed block coupled to a frame of the trailer; a winch; and a cable, the cable communicating with the moving block, the fixed block, and the winch, the axle lift system configured to move the axle upon operation of the winch. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be more fully understood from the detailed description below and the accompanying drawings, wherein: 
         FIG. 1  is an elevation view of an axle lift system installed on a trailer frame, according to an embodiment of the invention; 
         FIG. 2  is an elevation view of an axle lift system installed on a trailer frame, according to an embodiment of the invention; 
         FIG. 3  is an elevation view of two axle lift systems installed on a trailer frame, according to an embodiment of the invention; 
         FIG. 4  is an elevation view of two axle lift systems installed on a trailer frame, according to an embodiment of the invention; 
         FIG. 5  is a plan view of an axle lift system installed on a trailer frame, according to an embodiment of the invention; 
         FIG. 6  is a functional block diagram of a monitoring and control assembly for an axle lift system, according to an embodiment of the invention; 
         FIG. 7  is a schematic diagram of a light-emitting diode (LED) module of a tire pressure monitoring system, according to an embodiment of the invention; 
         FIG. 8  is a schematic diagram of a lift control user interface, according to an embodiment of the invention; 
         FIG. 9  is a layout of a user interface panel, according to an embodiment of the invention; and 
         FIG. 10  is an illustration of a graphical user interface, according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the invention now will be described more fully with reference to  FIGS. 1 to 10 , in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. 
     Lift Apparatus 
       FIG. 1  is an elevation view of an axle lift system installed on a trailer frame, according to an embodiment of the invention. As shown therein, leaf springs  110  are coupled to a frame  165  of a double axle trailer. In the illustrated embodiment, the leaf springs  110  are secured above the axles  105  by u-bolt assemblies  115 . The leaf springs  110  are coupled to each other via shackle straps  125  and equalizer  120 . A spring bracket  150  is connected to a portion of a leaf spring  110  adjacent to an axle  105 . The spring bracket  150  is coupled to the frame  165  via a block and tackle lift apparatus that includes winch  155 , cable  130 , fixed block  135 , and moving block  140 . The fixed block  135  is connected to the frame  165  via anchor mounting bracket  145 . The lift apparatus will be further described with reference to  FIG. 5  below.  FIG. 1  also illustrates an electrical connection box  160  to facilitate electrical connections to the winch  155 . The spring bracket  150 , winch  155 , cable  130 , fixed block  135 , and moving block  140  are all components of an axle lift system. 
     In an axle-lifting mode, the winch  155  retracts (winds) the cable  130 , causing the axle  105  that is adjacent to the spring bracket  150  to rise. In an axle-lowering mode, the winch  155  releases (unwinds) the cable  130  and the force of the associated leaf spring  105  causes the axle to return to its normal operating position. 
     Variations to the configuration illustrated in  FIG. 1  are possible. For example, in an alternative embodiment, the spring bracket  150  could be replaced with an axle bracket configured to couple directly to the axle  105  casing. The location of the anchor mounting bracket  145  with respect to the corresponding axle  105  could be varied, according to design choice. Other variations are described below with reference to  FIGS. 2-4 . 
       FIG. 2  is an elevation view of an axle lift system installed on a trailer frame, according to an embodiment of the invention.  FIG. 2  illustrates that, in an alternative embodiment, the leaf springs  110  may be secured below the axles  105  by the u-bolt assemblies  115 . 
       FIG. 3  is an elevation view of two axle lift systems installed on a trailer frame, according to an embodiment of the invention.  FIG. 3  illustrates that, in an alternative embodiment, the leaf springs  110  are secured above the axles  105 , and axle lift systems are installed on each of the two axles  105 .  FIG. 4  is an elevation view of two axle lift systems installed on a trailer frame, according to an embodiment of the invention.  FIG. 4  illustrates that, in an alternative embodiment, the leaf springs  110  are secured below the axles  105 , and axle lift systems are installed on each of the two axles  105 . 
     Although the elevation views in  FIGS. 1-4  only illustrate a portion of one side of a trailer, it should be appreciated that the non-illustrated side of the double axle trailer could include an axle lift system on or adjacent to one or both axles. Preferably, a double axle trailer is configured with four axle lift systems, one associated with each trailer wheel. 
       FIG. 5  is a plan view of an axle lift system installed on a trailer frame, according to an embodiment of the invention. Some components, for example the anchor mounting plate  145  and frame  165 , are omitted for clarity. In the illustrated embodiment, the leaf spring  110  is secured above the axle  105 .  FIG. 5  shows the relative positioning of a wheel hub  505  on the axle  105 . As shown, the fixed block  135  includes three pulleys; the moving block  140  includes two pulleys. An end of cable  130  is looped around bolt  510  and terminated with cable clamp  515 . In alternative embodiments, the fixed block  135  and moving block  140  could each include a fewer or greater number of pulleys. 
     Controls 
       FIG. 6  is a functional block diagram of a monitoring and control assembly for an axle lift system, according to an embodiment of the invention. In the illustrated embodiment, a Tire Pressure Monitoring System (TPMS)  605  includes a TPMS user interface  610 . The TPMS  605  may be a direct type (relying on the use of pressure sensors inside or outside of each tire) or an indirect type (estimating pressure, for example, based on wheel speed, acoustic signature, or other factors). The TPMS user interface  610  may output an audible or visual alert, for instance, when the measured or estimated tired pressure within a pneumatic tire falls below a predetermined threshold. Alternatively, or in combination, the TPMS user interface  610  may display a measured or estimated tire pressure value for each tire being monitored. 
     As also illustrated in  FIG. 6 , a lift control user interface  615  is coupled to each of four winches  155  via a link  625 . The lift control user interface  615  is configured so that an operator can independently control each of the winches  155  (preferably in either direction) by manually inputting a control signal. The link  625  could be or include a cable assembly and/or a wireless communication link. 
     Preferably, elements of the TPMS user interface  610  and lift control user interface  615  are integrated, spatially and/or via software, as will be described below with reference to  FIGS. 9 and 10 . Preferably, the TPMS user interface  610  and/or lift control user interface  615  are remotely located, for example at an operator&#39;s station in a tow vehicle or at one end of a trailer on which one or more axle lift systems are installed. 
     Variations to the configuration illustrated in  FIG. 6  are possible. For example, the number of winches  155  can vary according to application needs (but 4 winches  155  are preferred for a double-axle trailer, and 6 winches  155  are preferred for a triple-axle trailer). In an alternative embodiment of the invention, the TPMS  605  automatically outputs a lift control signal to a selected one of the winches  155  based on a measured or estimated low-pressure condition, preferably in addition to an audible and/or visual warning to the operator. 
       FIG. 7  is a schematic diagram of a light-emitting diode (LED) module of a tire pressure monitoring system, according to an embodiment of the invention. The illustrated schematic describes one embodiment of the TPMS user interface  610 . As shown therein, a logical high signal received at any TPMS display input  705  will illuminate a corresponding LED  710 . Each of the LEDs  710  is connected to ground  720  via a corresponding series-coupled current-limiting resistor  715 . 
       FIG. 8  is a schematic diagram of a lift control user interface, according to an embodiment of the invention. The illustrated schematic describes one embodiment of the lift control user interface  615 . As shown therein, a +12 VDC source supplies a VCC buss  805  via a series-coupled fuse  810 . Each of the switches  815  (preferably rocker switches) is configured to output an up (UP) or down (DN) lift control output signal  820  to a corresponding winch  155  based on operator input. 
       FIG. 9  is a layout of a user interface panel, according to an embodiment of the invention. The configuration in  FIG. 9  is an example of a spatially-integrated TPMS user interface  610  and lift control user interface  615 . As shown therein, each of 4 LED&#39;s  710  are mounted on a panel  905  adjacent to a corresponding switch  815 . 
     In operation, the TPMS  605  illuminates a selected one of the LED&#39;s  710  based on a measured or estimated low pressure tire condition. An operator would then preferably stop the vehicle and depress a corresponding switch  815  in the up (UP) direction to activate a corresponding winch  155  and raise the axle  105  associated with the flat tire. After the flat tire is repaired or replaced, the operator would depress the corresponding switch in the down (DN) direction to cause the corresponding winch  155  to release its cable and lower the axle  105  associated with the repaired or replaced tire to its normal operating position. 
       FIG. 10  is an illustration of a graphical user interface, according to an embodiment of the invention. The configuration in  FIG. 10  is an example of a software-integrated TPMS user interface  610  and lift control user interface  615 . As shown therein, an input/output device  1000  (an electronic display) is configured to display trailer icon  1005 , low pressure warning icons  1010 , and winch control buttons  1015 . As used herein, an electronic display may be configured to receive user inputs, for example via touch screen techniques. 
     In operation, the TPMS  605  would cause a selected one of the low pressure warning icons  1010  to illuminate, change colors, flash, or otherwise alert the operator based on a measured or estimated low-pressure tire condition. An operator would then preferably stop the vehicle and depress a corresponding winch control button  1015  on the electronic display  1000  to activate a corresponding winch  155  and raise the axle  105  associated with the flat tire. After the flat tire is repaired or replaced, the operator would depress the corresponding winch control button  1015  to cause the corresponding winch  155  to release its cable and lower the axle  105  associated with the repaired or replaced tire to its normal operating position. 
     Although the embodiments described above with reference to  FIGS. 6-10  are for a 4-winch configuration, any monitoring or control functions could be easily scaled to any number of axle lift systems, according to application requirements. 
     CONCLUSION 
     Embodiments of the invention thus enable an operator to easily identify and/or lift an axle associated with a trailer tire that is flat or excessively low on pressure. On a multi-axle trailer, such a system facilitates an emergency tire change and may enable an operator to tow the trailer to a service station or other safe location. 
     It will be apparent to those skilled in the art that modifications and variations can be made without deviating from the spirit or scope of the invention. For example, the monitoring and control features described with reference to  FIGS. 6-10  are not necessarily required. The TPMS  605  could be omitted entirely. Each winch  155  could be operated via a corresponding switch that is co-located on the trailer (for example in the electrical connection box  160 ).