Patent Publication Number: US-7219770-B2

Title: Coordinated lift system with user selectable RF channels

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims priority under 35 U.S.C. 119(e) and 37 C.F.R. 1.78(a)(4) based upon copending U.S. Provisional Application Ser. No. 60/491,953 for COORDINATED LIFT SYSTEM WITH SELECTABLE RF CHANNELS, filed Aug. 1, 2003. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to a coordinated lift system and, more particularly, to a coordinated lift system incorporating at least two lift mechanisms that communicate by wireless signals on user selected RF channels to coordinate lift mechanisms in the raising and lowering of a vehicle. 
   The need to lift a vehicle from the ground for service work is well established. For instance, it is often necessary to lift a vehicle for tire rotation or replacement, steering alignment, oil changes, brake inspections, exhaust work, and other automotive maintenance. Traditionally, lifting a vehicle has been accomplished through the use of equipment that is built-in to the service facility, such as either lift units with the hydraulic actuator(s) installed below the surface of the floor or two and four post type lift systems installed on the floor surface. These built-in units are located at a fixed location at the service facility and adapted to engage the vehicle frame to lift the vehicle from the ground. However, built-in units tend to be relatively expensive and are sometimes not as useful as they might otherwise be due to their immobility. 
   In an effort to increase the versatility and mobility of lift devices and reduce the need to invest in permanently mounted lifting equipment, devices commonly known as a mobile column lifts (MCL&#39;s) have been developed. Apparatus for lifting a vehicle using multiple MCL&#39;s is described in U.S. Pat. No. 6,315,079 to Berends et al. The lifting device in the Berends patent includes using a number connecting lines or wires to provide electrical power and control of the MCL&#39;s. The lines or wires that are connected between the MCL&#39;s allow the vehicle to be raised or lowered in a coordinated fashion. However, the lines and wires used to connect the MCL&#39;s extend across and are looped within the working area. The presence of the wires and lines in the work area poses a hazard to people working near the vehicle, and the connecting lines may be damaged by vehicles driving over them. 
   Another apparatus for lifting a vehicle using multiple MCL&#39;s is described in U.S. Pat. No. 6,634,461. The &#39;461 lifting device includes multiple MCL&#39;s that are coordinated by coded wireless signals, such as RF (radio frequency) signals, and powered by rechargeable batteries in each lift unit. By these means, the lifting devices in the &#39;461 patent eliminate the need for both power cables and control cables. However, the wireless system of &#39;461 does not allow the user to select the frequency of operation of transceivers of the control units of the lift devices. For this reason, two systems may not be usable simultaneously in a given location without the possibility of interference. Further, if signal interference occurs at a specific location, the frequency on which the system is operating cannot be changed in the field to avoid such interference. 
   Accordingly, there remains a need for a control unit for a wireless mobile lift system with intercommunication frequencies which can be user selected in the field to avoid interference from other lift systems or from unknown sources. 
   SUMMARY OF THE INVENTION 
   The present invention provides a lift system that coordinates the raising and lowering of a vehicle or other structure relative to a surface using sets of mobile column lift units, each having self-contained battery power, and wirelessly coordinated through the use of RF signals which are communicated on RF channels conveniently selectable in the field by the user. 
   In general, the lift system includes at least two lift mechanisms, each including a support frame, a post or vertical guide member, a carriage slidably mounted on the post, an actuating device engaged between the support frame and the carriage, and a controller or control device. The carriage is adapted to engage and support a portion of the vehicle, such as a vehicle tire. The actuating device, such as a hydraulic cylinder with a hydraulic pump and suitable valves, is selectively activated to move the carriage relative to the post. The control device is interfaced with the actuating device and includes wireless transceiver circuitry, such as an RF transceiver including circuitry to operate one any of a plurality of RF channels. The control devices on the lifting mechanisms communicate with one another by wireless RF signals to coordinate the movement of each carriage along the posts to raise or lower the vehicle relative to the surface. The purpose of such coordination is to maintain the vehicle, or other structure, in a substantially level plane during lifting and lowering. The control device further includes channel selector switching whereby any one of the available radio frequency channels may be conveniently selected by the user in the field. 
   Additionally, the control device include a height sensor, a digital display, and a stop mechanism. The height sensor is engaged between the support frame and the carriage and is used to determining the position of the carriage relative to the post. The stop mechanism operates to prevent movement of the carriage relative to the post of any lift mechanism of a coordinated set. Each lift unit includes a rechargeable battery, such as a marine type lead-acid battery, that provides portable power to the control device and the actuating device to move the loaded carriage relative to the post. The present invention may include a separate remote control device capable of communicating with the control device using wireless signals to raise or lower the vehicle relative to the surface without being stationed to a particular location. 
   The present invention provides method for the coordinated lifting and lowering of a vehicle relative to a surface. The method generally includes providing first and second lift mechanisms, placing the first and second lift mechanisms in contact with a portion of the vehicle, such as a vehicle wheel, selecting a particular RF channel on each control device, sending a wireless control signal from the first lift mechanism, receiving the wireless signal at the second lift mechanism wherein wireless signal instructs the second lift mechanism to move the vehicle relative to the surface, and moving the vehicle using the first lift mechanism in coordination with the second lift mechanism. The method also includes steps such as the entry of the number of lift mechanisms to be used in the lifting operation and the wireless querying of the lift mechanisms to determine the actual number of lift mechanisms present, prior to enabling coordinated operation of the lift mechanisms. 
   Each of the lift mechanisms preferably includes surface engaging wheels and a tongue or handle which enable the lift mechanisms to be moved manually to the required location. Each lift mechanism may also include carriage adapters to expand the range of vehicle wheels which the carriage may usefully engage. Alternatively, other carriage adapters may be provided for lifting structures other than vehicles, such as aircraft, shipping containers, housing construction subassemblies, and the like. 
   Other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention. 
   The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view illustrating a plurality of lift mechanisms according to the present invention, shown supporting a vehicle in a raised position. 
       FIG. 2  is a schematic diagram showing input and output components associated with the control devices of each of the lift mechanisms of the present invention. 
       FIG. 3  is a flow chart illustrating a portion of the operation of the control device of the present invention. 
       FIG. 4  is a continuation of flowchart in  FIG. 3  illustrating a portion of the operation of the control device, the wireless communications being shown in broken lines. 
       FIG. 5  is a schematic diagram illustrating communications between a master control device, slave control devices, and associated output device, the wireless communications being shown in broken lines. 
       FIG. 6  is an enlarged perspective view of a control device of a lift mechanism. 
       FIG. 7  is a block diagram illustrating an embodiment of RF channel selection switches for the lift mechanisms of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. 
   Referring now to the drawings in detail, and initially to  FIG. 1 , numeral  10  generally designates a coordinated lift system with user selectable RF channels which embodies the present invention. Generally, the lift system  10  includes four lift mechanisms, or mobile column lifts (MCL&#39;s),  12  that communicate by wireless signals to coordinate the movement of a vehicle  14  relative to a surface, such as pavement, a garage floor, or the like. It should be understood and appreciated that the number of lift mechanisms  12  used in the present invention may vary depending on the type of vehicle being lifted. Typically, the lift mechanisms  12  are used in pairs. For example, six lift mechanisms may be used to lift a three axle vehicle for service. Furthermore, it should be understood that lift system  10  is not limited for use with vehicles, but also may be used to raise or lower other objects relative to the surface, such as aircraft, industrial machinery, shipping containers, construction subassemblies, and the like. 
   Each lift mechanism  12  includes a support frame formed by a post or guide  18  upstanding from a base  20 . The base  20  includes a pair of flanges legs that are joined to one another by a cross piece  24 . A pair of front wheels  26  are rotatably mounted at an end of the legs  22 . A pair of main or rear wheels  28  are rotatably mounted adjacent to cross piece  24 . The wheels  26 ,  28  enable the lift mechanism  12  to be rolled along the surface and placed in a position to support vehicle  14 . A handle  30  is linked to the wheels  26 ,  28  and may be moved about a pivot point established adjacent to wheels  28 . The handle  30  may be used to place wheels  28  in contact with the surface so that lift mechanism  12  may be rolled into position. Once the lift mechanism  12  is in a desired position, the handle  30  is then used to raise wheels  28  so that they are no longer in contact with the surface. The illustrated wheels  26  are preferably mounted on spring loaded mechanisms (not shown) which are overcome by the weight of the vehicle  14  so that the legs  22  securely contact the floor surface during lifting. The lift mechanism  12  is thereby placed in a stable position for raising and lowering the vehicle  14 . 
   The post  18  is mounted to cross piece  24  and extends upwardly therefrom. The lifting mechanism  12  includes a carriage  32  that is slidably mounted on the post  18 . Specifically, carriage  32  includes a pair of spaced apart, upright slot portions  34  that engage a flanges of the post  18  to guide the carriage  32  in movement along the post  18 . The carriage  32  includes a pair of forks  36  that extend outwardly from slot portions  34  and are adapted to support a portion of vehicle  14 . In particular, the illustrated forks  36  are adapted to support the vehicle  14  at a wheel. However, it should be understood that carriage  32  may also be adapted to engage and support the frame or any other portion of vehicle  14  or other type of structure with the system  10  is intended to lift. 
   The carriage  32  may be moved relative to the post  18  using a linear actuator, such as a hydraulic piston and cylinder assembly  38 . The cylinder  38  is engaged between the support frame, by way of the post  18  or base  20 , and the carriage  32  in such a way that extension and retraction of the cylinder  38  moves the carriage  32  upwardly or downwardly along the post  18 . A power unit or motorized hydraulic pump  39 , in combination with suitable valves (not shown), is used to move a fluid into the cylinder in such a manner to cause the cylinder  38  to extend, as will be described in further detail below. Extension of the cylinder  38  causes carriage  32  move upwardly relative to the surface. As fluid is removed from the cylinder  38 , the cylinder moves downwardly and carriage  32  is lowered by gravity. It should be understood that hydraulic piston and cylinder assembly  38  could alternatively be replaced by a pneumatic actuator, a motorized jackscrew, or an equivalent kind of actuator. Further, it is considered within the scope of the present invention to use a double acting cylinder to move the carriage  32  relative to the post  18 . 
   Each lift mechanism  12  includes a control box  40  or control unit configured to control activation of the local lift cylinder  38  and to communicate with the other control boxes  40  in lift system  10  by wireless signals to coordinate the raising and/or lifting of vehicle  14 . The control unit  40  includes a controller or control processor  35  ( FIG. 7 ), such as a microprocessor which is programmed to perform its desired control and communication functions. A wireless transceiver, such as a radio frequency (RF) transceiver  37 , is also mounted in the control box  40  and includes an externally mounted antenna  44  to radiate RF signals to transceivers  37  in other control boxes  40  and to receive signals therefrom. A rechargeable battery  42  provides electrical power to components within the control box  40  through a power switch  43  and also provides operating power for the hydraulic pump  39  to activate the lift cylinder  38 , so that each lift mechanism  12  can operate without power cables or control cables. The transceiver  37  includes circuitry which provides for operation on one of a plurality of RF channels which can be selected by the user in the field, as will be described in more detail below. 
   The control box  40 , shown in  FIGS. 2 and 6 , is interfaced to a number of components, designated as input components  46 . One input component is a height sensing detector or sensor  48  which determines the height of the carriage  32  relative to the surface and relays such information to control box  40 . The illustrated height sensor  48  is preferably a relative position sensor, such as one which employs an optical detector of spaced openings, markings, or the like. Such an optical detector (not shown) could be used with either a rotary or a linear set of markings. Alternatively, an absolute type of position encoder could be employed, the particulars of which would be familiar to one skilled in the art. Other input components include an emergency stop switch  50 , an interlock function switch  52 , a mode selector switch  54 , an up/down motion switch  56 , and a communication channel selector switch  57 . The emergency stop button  50  enables a user to instruct the control box  40  to stop moving carriage  32  relative to post  18 . For safety, the interlock function switch  52  is required to be engaged before lifting or lowering of the carriage  32  can occur. When the lift system  10  is in a synchronized mode for coordinated lifting, the interlock function  52  also allows a user to specify which one of the control boxes  40  will be a master control box. Once a master control box is selected, the remaining control boxes  40  are designated as slave control boxes and operate under user control actions initiated at the master control box. A more detailed discussion of the coordinated operation of the lift mechanism  12  will be provided below. 
   The mode selector switch  54  allows the control box  40  to be toggled between an off mode and a synchronized mode. The motion switch  56  selects the direction of movement and causes the control box  40  to initiate raising or lowering of the carriage  32  relative to the surface. The emergency stop, interlock or motion input components  46  described above may alternatively be activated by a remote control device  58  by use of a wireless link. The channel selector switch  57  enables the user to select which RF channel the system  10  will use to communicate among the individual lift units  12 . It should be appreciated that it is within the scope of the present invention to provide for other input devices such as, but not limited to, a level sensor (not shown) adapted to determine the orientation of a post  18  relative to vertical. 
   The control box  40  is interfaced to a number of components which may be referred to as output components  59 . The illustrated output components  59  may include the hydraulic pump  39 , a lowering valve solenoid  62 , a holding valve solenoid  64 , and a safety release solenoid  66 . The output components  59  are are used to control the movement of carriage  32  relative to post  18 . In particular, the hydraulic pump  39  moves fluid within the cylinder to raise carriage  32 , as further controlled by valves (not shown) associated with the solenoids  62 ,  64 , and  66 . The lowering valve solenoid  62  is activated to release fluid from the cylinder to thereby lower carriage  32  toward the surface under the influence of gravity. The holding valve solenoid  64  normally maintains the position of carriage  32  relative to post  18 . The safety release solenoid  66  is a backup mechanism that normally functions upon the failure of cylinder assembly  38  to prevent carriage  32  from inadvertently falling downwardly toward the ground. During the normal lowering operation of the lift system  10 , both the holding valve solenoid  64  and the safety release solenoid  66  may be activated to release the carriage  32  and allow it to move relative to post  18 . The control box  40  includes display  68  which displays information such as, but not limited to, the height of one or more of the lift mechanisms  12 , the selected RF channel on which the control boxes  40  are communicating, the state of charge of the battery  42 , status codes, error codes, and any other information essential to operation of the system  10 . 
   In operation, one or more lift mechanisms  12  are first placed in a position to support a portion of the vehicle  14 . In particular, the forks  36  are placed on opposite sides of a vehicle tire in a support position. As previously stated, in order to provide a mobile and convenient lift system  10 , each of the lift mechanisms  12  is powered by rechargeable battery  42 . Energy stored in the battery  42  provides the power required for the operation of the lift mechanism  12  and the control box  40 . The battery  42  may be recharged when the lift mechanism  12  is not in actual operation, that is, not actually lifting or lowering a vehicle. 
   The synchronized mode of operation allows input commands at one control box  40  to influence other control boxes within the system  10  to provide a coordinated lift of vehicle  14 . Coordination of the lifting operation is required to maintain the lifted vehicle  14  in a substantially level orientation, that is, to avoid tipping the vehicle or other load. Initially, referring to  FIG. 3 , each control box  40  is set to a selected RF channel at step  69 , using the channel selector switch  57 . The control box  40  on one of the lift mechanisms  12  is turned on at step  70  and proceeds to perform steps  74  and  76  where the height is checked and displayed. At step  78 , the mode selector switch  54  is set to the synchronized mode position, if it is not already in such a position. Referring to  FIGS. 3 and 4 , at step  88  a determination is made as to which of control boxes  40  will take part in the coordinated lift of vehicle  14 . Preferably, the number of lift mechanisms  12  to be used is entered into the master control box. At this point all participating control boxes  40  should be set to the same channel. Next, any other lift mechanisms  12  that will take part in the lift should be set up. Set-up includes setting the control box  40  to the same channel, step  69 , and turning the unit on, step  70 . If no other control boxes  40  are turned on, then lift mechanism  12  proceeds to step  90  where it scans for the selected radio frequency channel and signals the height. In addition, the control box  40  may displays its height as the operator sets up the other participating lift mechanisms in step  90 . Once a control box  40  is placed in synchronized mode, it searches to communicate with one or more lift mechanisms  12  at the selected frequency. 
   Once the other control boxes have been turned on, the lift system  10  moves to step  92  at which each of the control boxes  40  are communicating at the same selected radio frequency. Each of the height sensors  48  provides a height measurement to its respective control box  40 , and the control boxes  40  provide the height measurement on the display. In step  92 , the control boxes  40  search for other control boxes  40  on the selected channel. If interference occurs or there is an unclear data exchange between the lift mechanisms  12 , an error message or signal loss is shown on the display  68  and the user is prompted to reset the system and select another channel. If this action occurs, the user must turn off the control boxes  40  at step  93  and start the process from the beginning at step  69  by selecting a different RF channel. This process may be repeated until a clear channel is located. 
   However, if no interference occurs, the lift system moves from step  90  to step  102 , or from step  92  to step  102 . In step  102 , each of the control boxes  40  waits for a command from its own box, remote control  58 , or one of the other control boxes by wireless communication. The first control box  40  which is activated is designated as the master control box  94 , and the remaining control boxes  40  are designated as slave control boxes  96 , as shown in  FIG. 5 . If none of the control boxes  40  receive a command, then the process proceeds to step  104  where master control box  94  may be established by selecting the interlock function  52  on any one of the control boxes  40 . If the interlock function is not selected, then the process returns to step  102  where each of the lift mechanisms  12  waits for a command. If the interlock is selected, then the operator chooses to raise or lower the vehicle at the master control box  94  as shown in step  105 . With additional reference to  FIG. 5 , the master control box  94  proceeds to command the slave control boxes  96  to raise or lower by one or more wireless signals  98  at step  118  by operation of the up/down motion switch  56 , and waits for a response from each of the slave control boxes  96  at step  106 . Once the wireless signals are sent via the selected channel by the master control box  94  at step  118 , the slave control boxes  96  wait to receive a command at step  102 . If one or more of the slave boxes  96  do not receive the wireless signal from the master control box  94 , the process remains at step  102 . 
   However, if the slave control boxes  96  receive wireless signal  98  from the master control box  94 , then the slave control boxes  96  must determine whether to raise, lower or hold the vehicle at step  107 . As best seen in  FIGS. 4 and 5 , if the wireless signal  98  provides an instruction to raise vehicle  14 , the master control box  94  and each of the slave control boxes  96  activate their respective pump  39  to cause the cylinder assembly  38  to move the vehicle in an upward direction. If the wireless signal  98  provides an instruction to lower the vehicle  14 , the master control box  94  and each of the slave control boxes  96  activates their lowering valve solenoid  62 , holding valve solenoid  64 , and safety release solenoid  66  to cause the cylinder assembly  38  to move the vehicle downwardly, as shown at step  110 . The pump  39  and the lowering valve solenoid  62  are preferably activated in intervals when the lift mechanisms  12  are raising and lowering the vehicle from the surface respectively. However, it should be understood and appreciated that the intervals may be of such a short duration that the lift mechanisms  12  operate to smoothly raise or lower the vehicle relative to the surface. The operation of the pump and lowering valve solenoid  62  may alternatively be conducted in a substantially continuous manner without any apparent intervals. 
   Notwithstanding whether the vehicle  14  is being raised or lowered as described in steps  108  and  110 , the height sensors  48  on each lift mechanism  12  determine the new height of the carriage relative to the surface, convey that information to their respective control boxes  94 ,  96 , provide the height on displays  68  and wait for another command as illustrated in  FIGS. 4 and 5 . The slave control boxes  96  then send the height information by wireless signals  112  to the master control box  94 . At step  114 , the master control box  94  compares its own height measurement with the height measurements sent by the slave control boxes  96  during the lifting or lowering of the vehicle  14  and determines if an adjustment is needed at step  116 . If the heights of each of the slave control boxes  96  are within a predetermined tolerance range, the master control box  94  sends a signal to all of the lift mechanisms continue to lift or lower the vehicle at step  118 . Once the vehicle  14  has reaches a desired height, the lift system  10  may then proceed from step  118  and return to step  102  where the slave control boxes  96  wait for a further command. Alternatively, if the master control box  94  receives a signal  112  that indicates that one or more of the other lift mechanisms  12  are not at the proper height and an adjustment is need, the master control box  94  will determine the rate of speed at which the lift mechanisms  12  must operate in order to maintain synchronism or coordination in the lift of the vehicle  14 , instructs the slow mechanisms to catch up in step  120  by one or more wireless signals  122 , and returns to step  102 . 
   It should be appreciated from the above descriptions that two separate lift systems  10  may be used in close proximity. Initially, in step  69 , the two separate lift systems  10  must be set to different RF channels. However, once the separate systems  10  are placed on different channels, the remaining steps are the same as described above. 
   The above described process for coordinating the lift of a structure using a plurality of actuators, such as hydraulic cylinders, provides an exemplary method of coordinating or synchronizing the cylinders, using wireless links between the lift mechanisms  12 . Other methods for coordinating multiple lifting actuators using controllers interconnected by cables are known within the art, and information concerning one such method can be obtained by reference to U.S. Pat. No. 4,777,798, which is incorporated herein by reference. 
   The channel selection switching  57  may be a multiposition rotary switch as shown in  FIG. 6 .  FIG. 7  shows an alternative to a rotary switch. In  FIG. 7 , four two-state switches  100 , such as on/off switches, are interfaced to a port  102  of the controller  35 . The two states of four such switches provides for sixteen switch state combinations. Each switch combination represents a binary number which is associated with a particular RF channel. The controller  35  reads the state of the switches  100  and sets the channel of the transceiver  37  according to the binary number read. The switches  100  may, for example, be toggle switches which are mounted on an externally accessible panel of the control box  40 . 
   In order to provide for a safe working environment for a user, the lift system  10  includes safety features to prevent inadvertent movement of the vehicle  14 . Specifically, the lift system  10  may provide for security features to prevent extraneous signals from interfering with the communications between the control boxes  40 . For example, each control box  40  may have a unique identifier associated therewith, wherein each communication sent by that control box  40  includes its unique identifier. The unique identifier may be in the form of a serial number. The receiving control boxes  40  may react to a communication from another control box  40  only if it the included serial number is recognized. This type of security feature prevents outside interference causing undesired activation of the lift mechanism  12 . In addition, the lift system  10  may also utilize other types of safety features, such as special encoding or encryption of the signals, or the like. Specifically, as shown in  FIGS. 2 and 5 , the safety release solenoid  66  may activate an independent mechanical latch (not shown) during the lowering function to prevent a carriage  32  on a lift mechanism  12  from falling to the surface upon a failure the cylinder assembly  38 . Furthermore, the emergency stop button  50  may also be activated at any point from any lift mechanism during the raising or lowering of vehicle  14  to stop further movement of carriage  32  relative to post  18 . 
   The present invention provides a lift system  10  that includes a plurality of lifting mechanisms  12  that communicate with each other using wireless signals to raise or lower a vehicle in a coordinated fashion. The channel selection capability allows the user to easily reset the system  10  to a different channel if local interference occurs or the channel initially selected. Further, the use of selectable RF channels allows multiple systems to be conveniently used simultaneously in close proximity. Additionally, the channel selection capability provides for increased mobility and allows the lifting mechanisms  12  to be moved to different locations without the concern for interfering signals. 
   It is to be understood that while certain forms of the present invention have been illustrated and described herein, it is not to be limited to the specific forms or arrangement of parts described and shown.