Patent Publication Number: US-6983196-B2

Title: Electronically controlled vehicle lift and vehicle service system

Description:
This application claims priority from U.S. Provisional Application Ser. No. 60/243,827, filed Oct. 27, 2000, the disclosure of which is incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   This invention relates generally to vehicle lifts and their controls, as well as to vehicle service systems having such vehicle lifts and controls. The invention is disclosed in conjunction with a unique electronic control which is simple and intuitive to operate, which may be stand alone or networked to other lift controls of the vehicle service system. 
   Hydraulic and electromechanical (screw) vehicle lifts for raising and lowering vehicles are well known. While the design and configuration of vehicle lifts vary, they all are used primarily for servicing vehicles. They must all have some type of control system to effect the raising and lowering function. 
   Prior art control systems for hydraulic lifts typically include an electric switch wired in series with the pump motor for raising the lift and a manually operated lowering valve for lowering the lift. Raising and lowering a vehicle into position requires a series of steps. Raising a vehicle with such a hydraulic lift requires depressing the electric switch to raise the vehicle, followed by operating the lowering valve to lower the lift to the locking mechanism. To lower a vehicle beyond the locking mechanism, such as to the ground, the first step is disengagement of the latches, which may be manually, electrically or pneumatically disengaged. The technician must first raise the lift off of the latches, and then either manually disengage the latches, or operate an electric switch or a pneumatic valve through a lever. The technician next operates the lowering valve while continuously operating the electric switch or pneumatic valve to hold the latches disengaged. 
   The vehicle lift and the area close by the lift, within which the technician moves and works on the vehicle is generally called the lift bay or service bay. To use the vehicle lift properly and safely, the technician needs accurate information regarding the safe operation and maintenance of the lift, such as for example vehicle lift points, operating conditions of the lift, maintenance and trouble shooting information. While working on a vehicle, a technician needs immediate access to current and accurate information regarding operating the lift and servicing the vehicle. 
   Typically, the information needed by a technician is not available at the lift bay. While the needed information is generally available as manuals or other printed form, such are frequently not kept in the service bay, if kept anywhere at all, and may be outdated. To obtain the information, the technician is thus usually required to leave the bay and locate the information. A technician may be unwilling to leave the bay to locate the information, since this adds another step to the technician&#39;s work schedule. A technician works more efficiently if everything needed to work on the vehicle is within the bay. Time spent by a technician away from the bay to obtain information, parts, process paper work, etc. detracts from the efficient performance of service on the vehicle. 
   Instruction on proper lift use is important for new technicians or new lifts. In such training situations, instruction may not occur at all if much effort is required to learn or teach the use of the lift or to locate the relevant instructional material. Instruction may be given by other technicians who may themselves not be aware of the proper operation of the lift, relying instead on their own understanding of operating the lift. 
   Proper lift maintenance is also important. Routine maintenance needs to be performed to keep a lift operating properly and safely. Although the need for preventative maintenance arises from the usage of the lift, information on preventative maintenance of lifts is not always readily available. Routine maintenance schedules may be kept independent of the lifts, and the technician does not know while he is in the lift bay whether routine maintenance needs to be performed. Maintenance information regarding repair or trouble shooting information is also typically not kept in the lift bay, resulting in limited or inefficient use of such important resource materials. 
   Although vehicle lifts define the service bay and are the focal point for servicing a vehicle, vehicle lifts themselves are considered secondary to other equipment used to service a vehicle. The view of the capabilities of a vehicle lift and its control has been limited to the raising and lowering functions, and has not extended to other functions. Thus, vehicle lifts and their controls have not been considered by those skilled in the art for providing access to information needed by the technician, or for collecting and transmitting information relative to operation of the lift of the servicing of the vehicle. 
   The present inventors have recognized that the overlooked vehicle lift and its control can meet the unrecognized needs for electronic delivery of information to and from the lift bay. The advent by the present invention of providing the ability to access, collect and transmit information by the vehicle lift control in addition to providing the lift functions, creates the new need to be able to revise the new non-lift functions of a lift control completely independent of the lift functions of the lift control. Because vehicle lifts are subject to third party certification, any changes to hardware or software which controls the lift functions, even if the changes only affect the non-lift functions, require recertification. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention, and together with the description serve to explain the principles of the invention. In the drawings: 
       FIG. 1  is a perspective view of a two post vehicle lift with control in accordance with the present invention. 
       FIG. 2  is a perspective view of a four post vehicle lift with control in accordance with the present invention. 
       FIG. 3  is a perspective view of the control assembly of a vehicle lift in accordance with the present invention. 
       FIG. 4  is a front view of the control assembly of  FIG. 3 . 
       FIG. 5  is a side view of the control assembly of  FIG. 3 . 
       FIG. 6  is a partially exploded perspective view of the control assembly of  FIG. 3 . 
       FIG. 7  is a partially exploded perspective view of the rear of the enclosure of the control assembly of  FIG. 3 . 
       FIG. 7A  is an exploded perspective of the display assembly and computer processor board. 
       FIG. 8  is a front view of the back plate of the control assembly of  FIG. 3 . 
       FIG. 9  is a partially exploded perspective view of the control assembly of  FIG. 3  illustrating the back plate attached to a vehicle lift post. 
       FIGS. 10A and 10B  are, respectively, front and side views of the back plate of a slave control illustrating an alternate embodiment including a pneumatic quick disconnect and a communications port 
       FIG. 11  is a partially exploded perspective view of an alternate embodiment of electrical connections to the control assembly at the back plate. 
       FIG. 12  is a schematic diagram of an embodiment of a control in accordance with the present invention. 
       FIG. 13  depicts the display screen and key pad of a control in accordance with the present invention. 
       FIG. 14  is diagrammatic illustration of a vehicle service system which includes a plurality of vehicle lifts in accordance with the present invention. 
   

   Reference will now be made in detail to the present preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings. 
   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to the drawings in detail, wherein like numerals indicate the same elements throughout the views,  FIG. 1  illustrates a perspective view of an asymmetric two post vehicle lift with an overhead cable equalization, generally indicated at  2 . Although an asymmetric two post lift is illustrated, the present invention is not limited to such. Lift  2  includes two spaced apart columns or posts  4  connected at their respective tops by overhead beam  6 . Each post  4  carries a respective carriage  7  which is moveable vertically along the respective post  4 . Extending from each carriage  7  are two respective arms  8 , shown pivoted to positions adjacent each other. In the embodiment depicted, each end  8   a  of arms  8  include flip up adapter  10  which engages the underside of the vehicle to be lifted. In this embodiment, adapters  10  have three positions which permit quick and easy contact with the pickup points on a variety of vehicles. Arms  8  may have any of a wide range of configurations which engage a vehicle in a variety of ways. Lift  2  includes power unit  12  which functions, in response to the control, to raise and lower arms  8 . Power unit  12  can be any convenient power source suitable to raise and lower arms  8 . In the embodiment depicted, power unit  12  is attached at the top end of one of posts  4  and includes electric motor  12   a  which drives hydraulic pump  12   b.  Hydraulic fluid for the hydraulic circuit is contained in reservoir  12   c.    
   Although not shown, a spotting dish may be used with lift  2  to locate the vehicle in the appropriate position relative to columns  4 . 
   On one of posts  4 , lift  2  includes control assembly, generally indicated at  16 . A slave control assembly  16   a  may be located on the other post  4 , the operation of which will be described below. 
     FIG. 2  illustrates a perspective view of a four post vehicle lift, generally indicated at  20 . Lift  20  includes four spaced apart columns or posts  22 , with control assembly  16  mounted to one of posts  22 . Although not shown, slave control assembly  16   a  may also be located on one of the other posts  22 . Lift  20  includes lifting platform  23  comprising a pair of runways  24 , each being carried at both ends by a respective post  22  through a respective yoke  25  which is movable vertically along posts  22 . As is well known, the vehicle to be lifted is driven onto runways  24  so that runways  24  engage the vehicle&#39;s tires. Lift  20  includes a power unit  26 , located at one of the rear posts of lift  20 , which functions in response to the control to raise and lower runways  24 . Power unit  26  can be any convenient power source suitable to raise and lower runways  24 . In the embodiment depicted, power unit  26  includes electric motor  26   a  which drives hydraulic pump  26   b.  Hydraulic fluid for the hydraulic circuit is contained in reservoir  26   c.    
   Although the two lifts depicted in  FIGS. 1 and 2  illustrate specific configurations of structures which engage the vehicle to be lifted, numerous configurations of structures currently exist and may be developed in the future. As used herein, movable lift engagement structure means those vertically movable parts of a vehicle lift which engage a vehicle in any manner so as to move the vehicle vertically in either direction, and includes, for example, arms  8  and runways  24 . Although the two lifts depicted are surface lifts, the use of the control of the present invention is not limited to surface lifts. 
   Before describing control assembly  16  in detail, it is noted that although control assembly  16  is depicted as being attached to a post of a vehicle lift, it may be mounted separate from the lift which it controls, such as on wall or on a separate stand. 
   Turning now to  FIG. 3 , control assembly  16  of the present invention is illustrated. Control assembly  16  includes enclosure  28  which houses the control itself. Enclosure  28  is made of any suitably material. In the depicted embodiment, enclosure  28  is made of an industrial grade, glass filled polypropylene which has high impact resistance and is resistant to chemicals common to a garage where vehicles are serviced. 
   In the embodiment depicted, enclosure  28  includes first recessed area  30  having walls  30   a  extending inwardly toward a generally flat panel  30   b  which comprises display screen  32 . Alternatively, display screen  32  could be omitted, as for slave control assembly  16   a , and flat panel  30   b  could be formed integrally with enclosure  28  of the same material. Enclosure  28  carries user interface  31  comprising display screen  32  and key pad  34 . Display screen  32  is disposed generally vertically at the rear thereof. In the embodiment depicted, display screen  32  is a LCD display, although any suitable display maybe used. By recessing display screen  32 , glare is reduced. 
   Key pad  34  is disposed in first recessed area  30  below display screen  32 . Key pad  34  is depicted as a generally flat panel which is tilted 30° up from horizontal, although any angle convenient to use may be used. Recessing key pad  34  aids in preventing accidental operation. As will be described in more detail below, key pad  34  comprises a keyboard with momentary contact switches underlying a flexible membrane which keeps contamination out of the switches. Any suitable user interface may be used, including for example, a touch screen display which functions as a switch to generate the desired signals upon touching the screen in the appropriate location. As will be described in detail below, in the embodiment depicted, key pad  34  comprises four keys formed as membrane switches. Although four keys are particularly suited for the particular embodiment depicted, it will be appreciated that more or less keys may be used. As used herein, key pad and keyboard include any user input device, including text input, touch screen input, etc. 
   Second recessed area  36  is disposed below first recessed area  30  having a generally vertical rear wall  38 . Rear wall  38  includes opening  40  shaped complementarily to what ever component is to be disposed therein. In the embodiment depicted in  FIG. 3 , opening  40  is a rectangle, shaped complementarily to a standard rectangular ground fault circuit interrupt electrical outlet  42 . Rear wall may also be formed without an opening. 
   Control assembly  16  includes electrical disconnect switch  44  disposed along a side thereof. Switch  44  functions as an on/off switch which can be locked in the off position and as an emergency stop switch. When switch  44  is turned off, there is no power to control assembly  16  beyond switch  44  so that the lift cannot be operated and electrical outlet  42  is not powered. This allows a single lift bay to be shut down, such as for servicing, rather than shutting down any other devices on that same electrical circuit. 
   Enclosure  28  includes opening  46  along one side thereof, which permits the necessary electric and pneumatic connections to the interior of enclosure  28 . As illustrated below, such electrical and pneumatic connections may be made to control assembly  16  in a variety of ways, some through opening  46  and some not through opening  46 . Visible through opening  46  is back plate  48 , described below. 
   Enclosure  28  includes access panel  50  which snaps into place as shown in access opening  52 . Access opening  52  allows access to the fasteners which secure back plate  48  in place. In one embodiment of the present invention, particularly for use with a two post vehicle lift, the locking mechanism is located directly behind access panel  50  to allow access thereto for manual latch disengagement in the event of a power outage. If access through access opening  52  is not necessary, access opening  52  and access panel  50  may be omitted, having in place thereof an integrally formed panel. 
     FIG. 4  is a front view and  FIG. 5  is a side view of control assembly  16 . Electrical and pneumatic lines  56  can be seen in  FIG. 5  extending into the interior of enclosure  28  through opening  46 . 
     FIG. 6  is a partially exploded perspective view of control assembly  16 . Back plate  48  is illustrated spaced slightly behind and aligned with enclosure  28 . Access panel  50  is shown exploded out from opening  52 . Fasteners  60  secure enclosure  28  to back plate  48 . 
     FIG. 7  is a partially exploded perspective view of the rear of enclosure  28 . Mounting holes  62  receive fasteners  60  ( FIG. 6 ) to secure enclosure  28  to back plate  48 . Wall  64  physically separates the area which is accessible through access opening  52  from the electrical components which are disposed below wall  64 . Assembly  66  is secured to enclosure  28  by fasteners  70 . 
   Referring also to  FIG. 7A , which is an exploded perspective view of assembly  66 , assembly  66  includes second computer processor  106 , the components which it comprises being carried by a circuit board which is physically separate from the main circuit board which carries first computer processor  104 . Assembly also includes display screen  32  and display protective cover  68 . Second computer processor  106  is connected to first computer processor  104  (carried by back plate  48 , as described below) by cable  72   a  which is plugged into connector  72 . Second computer processor  106  carries removable memory module  106   a.    
     FIG. 8  is a front view of back plate  48 . Back plate  48  includes mounting holes  74  for securing back plate  48  (and control assembly  16 ) to a lift post or other selected mounting surface. Back plate  48  may be provided with a variety of auxiliary mounting brackets for attaching various components thereto, not all of which are used for each lift model on which control assembly  16  may be used. 
   In the embodiment depicted, back plate  48  carries all major components of the control except for assembly  66  and key pad  34 , including carrying main circuit board  76 , which carries first computer processor  104 , electrical transformer  78 , motor contactor  80  and audible signal sounder  82 . 
   Referring now to  FIG. 9 , there is shown a partially exploded perspective view of control assembly  16 , with back plate  48  mounted to post  4 . Trough  98  is shown covering any electrical and pneumatic lines, such as illustrated at  56  in  FIG. 6 . 
   In the particular embodiment depicted in  FIG. 9 , post  4  carries locking mechanism  86  which is controlled by solenoid  88 . Locking mechanism  86  includes pivoting latch  90  which is normally biased into engagement with a series of vertically aligned windows and steps, resembling a ladder, carried by carriage  7  (not shown in  FIG. 9 ). Engagement of latch  90  with any of the steps prevents the moveable lift engagement structure from lowering beyond that step, thereby providing a positive mechanical lock, preventing downward movement of the vehicle. In order to lower the vehicle intentionally, latch  90  is held in its disengaged position by actuation of solenoid  88 . 
   Solenoid  88  is sufficient for use with two post light duty lifts, with one on each post. Each solenoid must be actuated. However, for other lift applications, such as the two or four post heavy duty lifts, the locking mechanism is actuated pneumatically. Disengagement of the pneumatic locking mechanism is accomplished through actuation of a solenoid operated pneumatic valve (not shown) which is pneumatically connected to each locking mechanism to disengage the latch. The pneumatic solenoid valve may be disposed within enclosure  28 , or elsewhere on the lift, so long as the solenoid is electrically connected to the lift control. If the pneumatic solenoid valve is disposed within enclosure  28 , pneumatic connections to connect to the pneumatic source and to connect the pneumatic solenoid valve to the latching/locking mechanisms must be provided. In such case, the pneumatic connections may be located internal or external to enclosure  28 , such as extending from a side. 
   In case of power failure or other malfunction, in order to lower the vehicle beyond the discrete increments defined by locking mechanism  86 , latch  90  must be manually disengaged. In the embodiment depicted in  FIG. 8 , back plate  48  is oriented such that latch  90  is disposed within access opening  84  (see  FIG. 8 ). This aligns access opening  52  with latch  90 , allowing access thereto by removal of access panel  50 . 
     FIGS. 10A and 10B  are front and side views of the back plate  48   a  of a slave control assembly  16   a , described in detail below. A slave control assembly uses the same enclosure  28  as master control assembly  16 , but lacks most of the electronic components of master control assembly  16  as seen in  FIG. 8 , having only a key pad (not shown in  FIGS. 10A and 10B ) connected by a cable (not shown) to master control assembly  16 . A slave control assembly does not have a display screen, having a flat panel in its place in enclosure  28 .  FIGS. 10A and 10B  illustrate an embodiment of back plate  48   a  having pneumatic threaded NPT connector  92  extending through opening  40  in place of electrical outlet  42 . A pneumatic source (not shown) is connected to the back side of connector  92  in any suitable manner. Back plate  48   a  also includes a communications port  94  carried by bracket  96  in place of electrical disconnect switch  44 . Communications port  94  can simply be connected to a telephone line or a computer communications network, allowing voice or computer connection therethrough. A pneumatic connection and a communication port may be placed in almost any position on either control assembly  16  or slave control assembly  16   a , in any opening as illustrated in the figures, for example openings  40  or  46 , or in openings added to enclosure  28 . 
     FIG. 11  illustrates another embodiment configuration of electrical connections to control assembly  16 . Bundle  98  includes electrical cables as well as a pneumatic tube, which are illustrated running vertically along and over the top of back plate  48 . Electric power is provided by cable  99 . This configuration can be used when control assembly  16  is mounted to a wall, a wall bracket or a post, such as are typical for use with inground lifts. 
   Turning now to  FIG. 12 , there is shown a schematic of one embodiment of control  100 . Components of control  100  which, in this embodiment, are part of the master control panel, schematically indicated as dashed line  102 , are housed within enclosure  28  of control assembly  16 . Control  100  includes first computer processor  104 , carried by first printed circuit board  76  (see  FIG. 8 ), which comprises first control logic which configures first computer processor  104  to selectively control the raising and the lowering of the movable lift engagement structure of the vehicle lift. Control  100  also includes second computer processor  106 , in this embodiment carried as part of assembly  66 , which comprises second control logic which configures second computer processor  106  to enable display of data and which also comprises maintenance control logic, described in detail below. Control  100  also includes motor contactor  80  and key pad  34 . Optionally, slave control panel, generally indicated at  108 , may be provided, including second key pad  34   a  but not including a second display screen. 
   Control  100  receives, generates and transmits a variety of condition signals which are indicative of various respective lift conditions related to the operation of the vehicle lift. As used herein, a signal includes an electric current or electromagnetic field used to convey data or effect an action, including for example, voltage, current, data imposed on a carrier signal and any more advanced signal forms, as well as the simple closing or opening of a switch of an electric circuit. 
   As illustrated in  FIG. 12 , key pad  34  is electrically connected to first computer processor  104  and transmits user input thereto as signals. In response to such transmitted user input, in the operation mode, first computer processor  104  selectively controls the raising and lowering of the moveable lift engagement structure. 
   Referring now to  FIG. 13 , there is shown display screen  32  and key pad  34  in their relative positions as carried by enclosure  28  (shown partially transparent). As mentioned above, the depicted embodiment of key pad  34  comprises four electric switches or keys  110 ,  112 ,  114  and  116 , in the form of momentary contact switches overlaid by a flexible membrane, which are also known as membrane switches. User input is delivered to key pad  34  by depressing the appropriate key or sequence of keys. 
   In the depicted embodiment, each key  110 ,  112  and  116  performs more than one function. Which function is performed by each key  110 ,  112  and  116  depends on which mode of operation of control  100  has been selected or enabled by actuation of key  114 . Key  114  is functional to cause control  100  to switch between the operating mode and the information mode, as described below in more detail. 
   Key  110 , which includes up arrow indicia, is functional to cause the moveable lift engagement structure to raise, or to scroll up through a menu displayed on display screen  32  depending on the mode of operation of control  100 . While in the operating mode, key  110  is actuated by depressing it, thereby transmitting a signal which enables the control logic of first computer processor  104  to generate a “raise” control signal in response thereto. The “raise” control signal energizes motor contactor coil  118  which closes the contacts of motor contactor  80 , providing power to motor  12   a  thereby driving pump  12   b  and raising the moveable lift engagement structure. Vertical position sensors (not shown) could be provided and the user could be allowed to input through a user interface a selected height. Control  100  could then interrupt upward movement of the moveable lift engagement structure once the selected height is reached, despite continued actuation of key  110 . It is noted vertical position sensors could also be used as a continuous position feedback system for individual control of the carriage or yoke. 
   Once the moveable lift engagement structure has been raised to a desired position, it may be lowered a bit so that latch  90  engages one of a plurality of steps formed between vertically aligned windows (not shown), resembling a ladder, which provides a positive mechanical lock preventing downward movement of the moveable lift engagement structure. Key  116 , which includes “lower to lock” and “select” indicia, is functional to cause the moveable lift engagement structure to lower to the locks, or to select a menu option displayed on display screen  32 , depending on the mode of control  100 . While in the operating mode, actuation of key  116  transmits a signal which enables the control logic of computer processor  104  to generate a lower control signal in response thereto. The lower control signal opens lowering valve  120 , which in the depicted embodiment is a solenoid operated valve, allowing the moveable lift engagement structure to lower. Since latch  90  is normally biased toward engagement, the moveable lift engagement structure can travel downwardly a short distance until latch  90  engages the next step. 
   Key  112 , which includes down arrow indicia, is functional to cause the moveable lift engagement structure to lower, or to scroll down through a menu displayed on display screen  32 , depending on the mode of control  100 . While in the operating mode, key  112  is actuated by depressing it, thereby transmitting a signal which enables the control logic of first computer processor  104  to generate a signal to disengage latches  90  and to generate a “lower” control signal. In the depicted embodiment, latches  90  are held in a disengaged position by actuation of each respective solenoid  88 . Alternatively, as described above, latches  90  may be operated pneumatically and disengaged by actuation of a solenoid valve providing pressure to pneumatic cylinders to hold latches  90  in a disengaged position. With latches  90  in the disengaged position, first computer processor  104  generates a “lower” control signal as described above, opening lowering valve  120 , thereby lowering the moveable lift engagement structure. 
   It is noted that when the moveable lift engagement structure is to be lowered from a position at which latches  90  are in engagement with a step, the moveable lift engagement structure first needs to be raised to separate latches  90  from the step to relieve the force. In such a situation, the user will first actuate key  110  to raise the moveable lift engagement structure a distance sufficient to relieve the forces, and the actuate key  112  to lower the moveable lift engagement structure as far as desired. Alternatively, control  100  may be configured to do this automatically in response to actuation of key  112  when starting from the “lowered to locks” position. 
   Control  100  monitors a variety of lift conditions. As used herein, lift conditions include any condition related to the operation, control or maintenance condition of the lift. Control  100  may monitor some operation conditions through receipt of condition signals from sensors disposed to generate an output signal indicative of the operation condition associated with that sensor. In the depicted embodiment, optical overhead sensor  122  (see  FIG. 1 , not seen but generally indicated by arrow, and  FIG. 12 ) is disposed to project a generally horizontal beam across lift  2  just under overhead beam  6 , to monitor when the top of the vehicle is proximate overhead beam  6 . It is noted that the overhead sensor does not have to be optical. Other sensors  124  and  126  are illustrated in  FIG. 12 . For lifts which so require, sensor  124  may be a slack cable sensor, to monitor whether lift cables are slack. Also, as may be required for a particular lift, sensor  126  is a toe guard switch, to monitor when carriage  8   a  is near the floor. 
   The number and configuration of such sensors depend on the operation conditions monitored. For example, for inground lifts, a sensor could be provided to monitor the ground water level. 
   Other condition signals indicative of operation conditions may be monitored by control  100  without the use of sensors. For example, in the depicted embodiment, control  100  monitors the voltage in each driver circuit for the actuators (in the depicted embodiment, motor contactor coil  118 , lowering valve  120 , and latching mechanisms  86 ) as well as regulated and unregulated 24 VDC, and VCC 5 volt input. 
   Of course, control  100  may monitor any operation condition. For example, the following may be monitored: vertical position of moveable lift engagement structure, hydraulic and/or pneumatic pressure, force on arms  8 , position of arms  8 , position of the vehicle, points on the vehicle, out of level conditions, engagement/disengagement of latching mechanism  86 , and wear on key components. 
   Some operation conditions may be monitored by control  100  only during certain operations, such as monitoring the toe guard sensor only when the lift is being lowered or the overhead sensor when the lift is being raised. 
   Computer processor  104  stores, in a non-volatile memory (such as an EEPROM), certain information regarding historical operation conditions, referred to herein as usage data, which can be used to track the performance of the lift. In the depicted embodiment, usage data stored by computer processor  104  includes the number of times motor contactor coil  118  has been energized (motor starts), the total time motor contactor coil  118  has been energized (motor on time), the number of times lowering valve  120  solenoid has been energized (lowering starts), the total time lowering valve  120  solenoid has been energized (lowering on time), the maximum length of time that lowering valve  120  solenoid has been energized (max lowering on time), the number of times that latch  90  (solenoid  88  or pneumatic valve solenoid) has been energized (latch starts), the total time latch  90  (solenoid  88  or pneumatic valve solenoid) has been energized (latch on time), the maximum length of time that latch  90  (solenoid  88  or pneumatic valve solenoid) has been energized (max latch on time), the number of times that overhead sensor  122  has been tripped (overhead cycles), and the number of times that toe guard sensor  126  has been tripped (lower sensor cycles). 
   Monitoring operation conditions involves access to information indicative of the condition being monitored and application of predetermined criteria to that information. Monitoring will result in a defined action if dictated by application of the predetermined criteria. Based on the application of predetermined criteria to the monitored operation conditions, the control logic of computer processor  104  will determine whether an operation fault condition exists, and if so, modify, including inhibit, the operation of the lift from that operation called for by user input, and in certain instances generate an operation fault indication signal which is transmitted to computer processor  106 , which, in the depicted embodiment, enables display of operation fault data, i.e., data indicative of the operation fault condition. Additionally, such predetermined criteria can be applied to usage data. 
   Predetermined criteria applied by the control logic of computer processor  104  to operation conditions monitored through sensors, and the resultant actions by control  100  include, but are not limited to:
         1. If a slack cable sensor is present, any time a slack cable is detected all lift and information display functions of control  100  will be inhibited until the slack cable signal is corrected and audible signal sounder  82  will sound. Computer processor  104  stops transmitting signals to computer processor  106  (such as user input from key pad  34 ). Computer processor  104  may, however, enable the display of operation default data by computer processor  106  indicative of the slack cable condition.   2. If a toe guard switch is present, when the moveable lift engagement structure is being lowered, when the toe guard switch is tripped (indicating the moveable lift engagement structure is proximate the floor, computer processor  104  inhibits further downward movement until key  112  is released and reactuated, after which causes audible signal sounder  82  to beep, as required by certain regulatory bodies. Alternatively, upon tripping of the toe guard switch, computer processor  104  may momentarily pause before continuing the downward movement accompanied by beeps. If the toe guard switch is omitted, beeps may be continuously generated while the lowering valve  120  solenoid is energized (such as by leaving the board connections for sensor  126  open, simulating a tripped toe guard switch).   3. If overhead sensor  122  is tripped and key  110  is actuated, the control logic of computer processor  104  will inhibit further upward movement of the moveable lift engagement structure, and enable the display of operation fault data indicative of the tripped overhead sensor.       

   Predetermined criteria applied to operation conditions related to actuators, include, but are not limited to:
         4. If the motor is supposed to be on, but it is off.   5. If the lowering valve is supposed to be open, but it is closed.   6. If either of the two latching mechanisms is supposed to be disengaged, but is engaged.   7. If the motor is supposed to be off, but it is on.   8. If the lowering valve is supposed to be closed, but it is open.   9. If either of the two latching mechanisms is supposed to be engaged, but is disengaged.       

   For each of the conditions related to the actuators, computer processor  104  will inhibit further movement of the moveable lift engagement structure, will enable the display of operation fault data indicative of the operation fault condition, and will flash LED indicator  128  (see  FIG. 8 ). The display of operation fault data is enabled by a control signal, the operation fault indication signal, from computer processor  104  to computer processor  106 , which recalls the associated operation fault data from the memory module  106   a . Actuation of key  112  during the display of operation fault data will enable the display of trouble shooting instructions related to the relevant operation fault condition. 
   In monitoring the operation of motor  12   c , latches  90  and lowering valve  120 , computer processor  104  checks itself for faulty actuator drivers and faulty actuators (in the depicted embodiment, motor contactor coil  118 , latch solenoid  88  (or pneumatic valve solenoid), and lowering valve  120  solenoid, although other actuators may be included) by checking the voltage at respective points in voltage divider circuits at each actuator driver output. When an actuator is supposed to be energized, computer processor  104  looks for at least a threshold voltage. If at least the threshold voltage is not present, then either the actuator driver is not delivering the required voltage to the actuator, or the actuator circuit is shorted. To determine whether an actuator is connected, computer processor  104  may also be configured to monitor current at the actuator or actuator driver. Actuator current data could be stored as usage data. When an actuator is not supposed to be energized, computer processor looks for no voltage at the actuator driver. 
   At power up, control  100  goes through a series of system checks, based on predetermined criteria, examining the status of all inputs and outputs of control  100  to make sure that they are in the correct state. In the depicted embodiment, this function is performed by computer processor  104 . Key pad  34  is checked to make sure no inputs are being generated. More specifically, computer processor  104  checks to see if any of keys  110 ,  112 ,  114  or  116  are closed. If second key pad  34   a  is present, computer processor  104  sees the corresponding keys  110   a ,  112   a  and  116   a  (not identified, but see  34   a  on  FIG. 12 ) as being in parallel with keys  110 ,  112  and  116 , and are therefore checked at the same time. Key  114   a  (not identified, but see  34   a  on  FIG. 12 ), which corresponds to key  114 , is not connected to computer processor  104 , preventing changing the mode from slave control assembly  16   a . The sensors  122 ,  124  and  126  are checked to make sure that a fault condition is not being indicated. At the same time, computer processor  104  checks for no voltage at the actuator drivers, indicating that no actuators are engaged. 
   During start up, computer processor  104  checks a specific location in its volatile memory to see if a specific key is stored there. If the specific key is stored there, it indicates that the volatile memory has not properly reset, such as might happen with a power glitch. Computer processor  104  terminates start up, inhibits operation of the lift, and enables the display of data indicative of the improper reset by computer processor  106 . If the specific key is not stored in the specific volatile memory location, indicating proper reset, computer processor  104  will write the specific key to the volatile memory location. 
   After verifying the system status is OK, control  100 , which powers up in the operating mode, may be used to control the raising and lowering of the moveable lift engagement structure. 
   Additionally, at start up computer processor  106  verifies the presence of an operable memory module  106   a . If it is not found, display  32  will so indicate. Control  100  remains in the operating mode, with keys  110 ,  112  and  116  remaining functional. However, mode key  114  cannot switch modes to the information mode. 
   While in the operating mode, upon the transmission of any user input to control  100 , such as through key pad  34 , which would enable actuation of an actuator, computer processor  104  checks all of the inputs from user interface  31  and all other inputs as at start up to verify that they are in the correct state. Computer processor  104  also energizes all actuator drivers one at a time for a short time, about one millisecond, long enough for computer  104  to check to make sure that at least the threshold voltage is present in the voltage divider circuits at the actuator driver outputs before proceeding, but not long enough to actuate any of the actuators. When the moveable lift engagement structure is being raised or lowered, if there is any inconsistent user input, such as pressing the up and down keys simultaneously, movement of the moveable lift engagement structure will stop until all user input ceases. 
   Control  100 , through computer processor  104 , periodically monitors the actuator drivers for the correct state. If an actuator is supposed to be energized, computer processor  104  looks for the threshold voltage at that actuator driver. If an actuator is not supposed to be energized, even when another actuator is actuated, computer processor  104  looks for no voltage at that actuator driver. 
   The occurrence of operation fault conditions are also communicated to the user independent of whether display screen  32  is operative. To communicate such information, a code of beeps and LED flashes may be used. In the depicted embodiment:
         1. Fast, short beeps/LED: Improper reset and/or slack cable failure.   2. Slow 50% duty cycle beeps/constant on LED: Toe-guard/overhead limit sensor tripped.   3. One short beep/LED flash, then pause: Motor is supposed to be off, but it is on.   4. Two short beeps/LED flashes, then pause: Lowering valve is supposed to be closed, but it is open.   5. Three short beeps/LED flashes, then pause: One of the two latching mechanisms is supposed to be disengaged, but is engaged.   6. Four short beeps/LED flashes, then pause: The other of the two latching mechanisms is supposed to be disengaged, but is engaged.   7. Five short beeps/LED flashes, then pause: Motor is supposed to be on, but it is off.   8. Six short beeps/LED flashes, then pause: Lowering valve is supposed to be open, but it is closed.   9. Seven short beeps/LED flashes, then pause: One of the two latching mechanisms is supposed to be engaged, but is disengaged.   10. Eight short beeps/LED flashes, then pause: The other of the two latching mechanism is supposed to be engaged, but is disengaged.
 
Of course, operation fault conditions may be communicated independent of display screen  32  in other ways, such as a recorded or synthesized voice.
       

   In the depicted embodiment, all of the functions which control the operation of the lift (which does not include display of data by display screen  32 ) while control  100  is in the operating mode, are performed by first processor  104  independent of second processor  106 . For example, the control logic is resident on first processor  104 ; sensors which monitor operation conditions are connected to computer processor  104 ; operation conditions not monitored through sensors are monitored through computer processor  104 ; the predetermined criteria on which the generation of an operation fault indication signal is based is resident on first processor  104 ; operation fault indication signals are generated by computer processor  104 ; communication of operation fault conditions independent of display screen  32  is done by computer processor  104 ; computer processor  104  generates the signals which enable second computer processor  106  to enable display of messages corresponding to operation fault conditions on display screen  32 ; and actuation of audible signal sounder  82  is done by computer processor  104 . 
   Thus, control  100  is configured so that computer processor  104  controls all lift operations regardless whether computer processor  106  is present or functional. By configuring the lift operation control to be resident in a single computer processor and fully operational to control the lift independent of other processors which provide non-lift operation functions, changes may be made to the non-lift operation functions and any associated processors, programming and hardware without affecting or requiring changes to the lift operation control. Since lifts and controls for lift operation are subject to third party certification, this separation of the functions between lift operation control and non-lift operation functions allows changes to be made to the non-lift operation functions without requiring rectification of the lift operation control. 
   As previously mentioned, control  100 , and more specifically computer processor  106  in the embodiment, depicted is also configured to enable display of data, in the depicted embodiment, through display screen  32 . In this embodiment, control  100  has two modes, the operating mode, as described above, and the information mode. As previously indicated, control  100  powers up in the operating mode. To switch to the information mode, key  114  is actuated thereby transmitting a “mode” signal which enables computer processor  104  to transmit a signal to computer processor  106 . In response to the signal from computer processor  104 , computer processor  106  will transmit an appropriate responsive signal to computer processor  104 . Upon receipt of the acknowledging responsive signal, computer processor  104  will enter the information mode. The same “handshake” protocol is followed in switching from the information mode to the operating mode. 
   While in the information mode, key pad  34  is not functional to control the lift operation, although computer processor  104  continues to monitor the operation conditions as described above. In the information mode, computer processor  104  transmits user input from key pad  34  to computer processor  106  to enable display of data in response thereto. 
   As mentioned above, keys  110 ,  112  and  116  are each configured to perform at least two functions: One set of functions may be performed while in the operating mode and a second set of functions may be performed while in the information mode. While in the information mode, the selection of data to be displayed is menu driven. In the information mode, display screen  32  displays menu options and keys  110  and  112  are used to scroll up or down through the menu. In this mode, key  116  is functional to select the menu option to which the user has scrolled. 
   Computer processor  106  is configured to enable display of lift data in response to user input received from key pad  34  via computer processor  104 . Lift data as used herein includes any data relevant to the operation or control of the lift. The display of such lift data can include various display techniques to draw attention to or to emphasize desired aspects of the lift data being displayed, such as flashing graphics. 
   Lift data includes usage data and operation fault data, as described above. Lift data also includes data which instructs the user in regard to the lift (instructional data). Instructional data includes information on how to use the lift (use instruction data), on safety practices and warnings relevant to operation of the lift such as displaying safety decal information (safety data), and on how to troubleshoot operation of the lift (troubleshooting data). 
   In the depicted embodiment, lift data also includes maintenance data. Maintenance data includes maintenance notice data indicating that a maintenance condition exists and maintenance instruction data which includes information on maintaining the lift. 
   As mentioned above, computer processor  106  includes maintenance control logic which is operative to generate a maintenance condition indication signal, based on predetermined criteria, which enables display of maintenance data indicative of the maintenance condition. Maintenance conditions include conditions that call for preventative maintenance and conditions that call for repair maintenance. 
   In the depicted embodiment, the predetermined criteria used to base the generation of a maintenance condition indication signal is based on the passage of time: A specific maintenance condition indication signal is generated when the predetermined time period for that specific maintenance condition has passed. The following table provides examples of predetermined time period criteria for the indicated maintenance condition: 
                                           Maintenance Condition   Time period (days)                                                    Check Cables/Sheaves for Wear   7           Inspect Adapters for Damage   7           Inspect Pads for Damage   7           Inspect Front Wheel Stops   7           Inspect Ramp Chocks   7           Check Locking Latch Operation   7           Clean Slip Plate/Radius Gauge   7           Check Level of Runway   30           Lube Turning Radius Guide   30           Check Equalizer Tension   30           Lubricate Guide Barrel(s)   30           Check All Bolts for Tightness   60           Check Anchor Bolt Tightness   90           Check Power Unit Fluid Level   180                        
These time periods are purely illustrative. In this example, reminders for daily maintenance conditions (i.e., maintenance conditions that should be addressed daily) are set at 7 days, rather than daily. The weekly reminder may include an indication that the maintenance needs to be performed daily. Not all of the maintenance conditions listed in this table applies to all lift types. Additionally, different time periods may also apply for different lift types. The user selects the lift type in the information mode, which identifies the predetermined criteria applicable to the particular lift type. Lift type is also relevant to whether the latches  90  are mechanically operated by solenoid  88  or whether a solenoid operated pneumatic valve is used, so the proper actuation voltage is applied by the associated actuator driver.
 
   As used herein, predetermined criteria, as related to maintenance conditions, includes criteria based on solely on the passage of a period of time, as well as criteria based on varying parameters related to the operation or environment of the lift, such as usage data. Such predetermined criteria includes, for example, algorithms which correlate usage data to the maintenance requirements of the lift as may be empirically developed. Additionally, such predetermined criteria may be based on operation fault data. 
   Upon generation of a maintenance condition indication signal, accompanied by display of the maintenance notice data, the user may either actuate the “select” key  116 , which will then enable display of maintenance instruction data regarding that maintenance condition, or actuate the mode key  114 , which will place control  100  in the operating mode. The maintenance condition may be reset at the appropriate display by input from the user through key pad  34 , preferably only after the indicated maintenance has been performed. The maintenance notice data will be displayed once a day, for example in the morning when the lift has been powered up for the day. Each subsequent day after the initial display of the maintenance notice data, if the maintenance condition has not been reset, the display will indict the number of days the maintenance condition has been passed due. Alternatively, display of the maintenance notice data may be scheduled for a particular time of the day, which is particularly beneficial in case control  100  is left on overnight. 
   Control  100  includes time management functions. Control  100 , through computer processor  106 , includes a timer function which displays lapsed time on display screen  32  in all operation modes. The timer may be started and stopped by actuating the appropriate key while in the information mode. Alternatively, the time may be started automatically upon placing a vehicle on the lift and/or raising the lift. Control  100  also includes and displays date and time information, and an alarm which can be set to beep at a preset time on a one time or daily basis. 
   In addition to lift data, computer processor  106  is configured to enable display of vehicle lift point data, which is data indicating the location of the proper lift points for a vehicle. In depicted embodiment, vehicle lift point data is available for most vehicles less than twenty years old. In this embodiment, vehicle lift points are displayed in conjunction with a graphical representation of the vehicle. 
   While in the depicted embodiment, selection of vehicle lift point data displayed is done by user input to key pad  34 , the display of vehicle lift point may be enabled in other ways. For example, data on the type of vehicle may be scanned, or transmitted by an RF or IR transmitter on the vehicle. 
   Control  100  may also be configured to display and receive various other data. Computer processor  106  may be configured to display service data regarding the vehicle. Service data includes any data relevant to performing service on the vehicle, such as instructions on servicing, service bulletins, specifications, time required for defined service, parts list, etc. Service data may include data about the service history of the specific vehicle. Control  100  may be configured to order parts based on input from the user from the facility&#39;s parts department, or even order directly from a parts supplier, with an appropriate communications connection, described below. Control  100  may be configured to keep track of the service performed and interface with an iqinvoicing system. 
   Control  100  may be configured to receive information identifying the user, such as through key pad  34 , through a card reader or any means, and to keep track of the user&#39;s time spent on the particular job. Control  100  may further be configured to require input of an authorized user identification before the lift may be operated. 
   Lift data is stored in a non-volatile electronic memory. Such electronic memory may be a physical storage device such as a hard drive, tape drive, etc. Such electronic memory may also be a memory module, such as an EEPROM, or the like. In the depicted embodiment, usage data, as well as the predetermined criteria for operation conditions and lift type information are stored in a non-volatile memory of computer processor  104 . 
   Instructional data and maintenance data are stored in memory module  106   a  carried by computer processor  106 . The predetermined criteria related to maintenance conditions is also stored in a memory associated with computer processor  106 . This allows changes to these data and criteria to be made without affecting any aspect of computer processor  104 . 
   Any other data displayable by control  100  is also stored in a memory. 
   Referring now to  FIG. 14 , there is diagrammatically shown vehicle service system  200  which includes a plurality of vehicle lifts  202 , with each vehicle lift  202  having a moveable lift engagement structure (not shown in  FIG. 14 ) and an associated electronic control  204 . Each electronic control  204  includes control logic configured to selectively control the raising and the lowering of the movable lift engagement structure of that vehicle lift, as described above. Each control  204  is connected to computer communication network  206 . Also connected to computer communication network  206  is central memory  208  and central computer processor  210 . Alternatively, central memory  208  may be connected to network  206  by being connected directly to central computer processor  210 . 
   The functions performed by computer processor  106  described above are performed for the plurality of lifts by central computer processor  210  and memory  208 . User input from the respective user interfaces (not shown in  FIG. 14 ) are transmitted by the respective lift controls  204  over network  206  to central computer processor  210 , which responds by transmitting the appropriate data or response to the respective lift control  204 . Operation fault indication signals, as described above, are generated as appropriate by the respective lift controls  204  and transmitted over network  206  to central computer processor  210 , enabling display of operation fault data. Central computer processor  210  responds by transmitting the appropriate operation fault data to the respective lift control  204  for display local at the associated vehicle lift  202 . 
   Operation fault data, instructional data and maintenance data are stored in memory  208 , as may be vehicle lift point data. Central computer processor  210  includes the maintenance control logic which, as described above, is operative to generate a maintenance condition indication signal, based on predetermined criteria, which enables display of maintenance data indicative of the maintenance condition. The predetermined criteria related to maintenance conditions is applied by central computer processor  201 . For predetermined criteria based on usage data, central computer processor  210  “looks” at the respective usage data collected by the respective control  204 . As with computer processor  106  as described above, storing the predetermined criteria in memory  208  provides greater flexibility to revising the criteria. By centralizing the data in memory  208 , implementing revisions for all lifts is simpler. For example, revisions could be downloaded from the internet or other external communication. 
   Alternatively, central computer processor  210  may be omitted, with memory  208  providing common memory storage of data and maintenance control logic for the second computer processors (corresponding to computer processor  106  as described above) of all lift controls  204 . This provides the advantages of a central memory. 
   Although as described above, the lift controls  204  networked to vehicle service system  200  all maintain the operation control logic locally (e.g., each has a respective first computer processor corresponding to computer processor  104  as described above), which is preferable, alternatively the operation control logic could be centrally located, with inputs and outputs being communicated over the network and with the user remaining local at the associated lift. Sensor outputs could be delivered over the network, while actuators could remain driven locally upon appropriate signal from the central computer processor  210 . 
   Other equipment may be connected to network  206 . For example, in addition to lift controls  204 , equipment and tools which are suitable for use in servicing a vehicle or with a vehicle service system may be fitted with an electronic control appropriate for that tool and connected to the network. 
   Other computer systems could be connected to network  206 , or network  206  could be part of or connected to a larger computer communication network to which other computer systems are connected. Such other computer systems could include for example parts ordering system, accounting/billing system, scheduling systems, etc. The network could be connected to other networks, such as the internet, for various reasons, such as to place parts orders or to download service data. 
   In summary, numerous benefits have been described which result from employing the concepts of the invention. The foregoing description of a preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiment was chosen and described in order to best illustrate the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.