Abstract:
An automobile service lift includes a plurality of generally vertical posts, each of which has a carriage moveably mounted thereon. Each carriage has an outrigger which extends outwardly from the carriage and supports a portion of the weight of a vehicle positioned on the lift. Each outrigger is pivotable relative to the respective carriage about a generally horizontal axis. Each carriage further includes an adjustment mechanism for selectively pivoting the respective outrigger to compensate for any deflection of the outrigger due to the weight supported thereon.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to the field of automobile service lifts, and in particular to a lift having adjustable outriggers which can compensate for deflection of the outriggers due to the weight of a vehicle on the lift. 
   2. Description of the Related Art 
   A wide variety of post-type automobile lifts have been previously known and used in the automobile repair business to provide access to the underside of a vehicle. Post lifts can be either of the in-ground or above-ground variety. In-ground post lifts usually have one or two vertically ascending columns mounted below the floor of a garage or service area which are raised hydraulically to lift the vehicle. Above-ground post lifts generally have two or four vertical columns or “posts,” each of which includes a carriage which rides up and down the post. These carriages are often raised and lowered by means of a chain, cable, or other flexible lifting member which is driven by a winch or hydraulic actuator. 
   Each carriage has one or more arms or “outriggers” which extend outwardly from the carriage. On some lifts, the outriggers directly engage the undercarriage of a vehicle such that the wheels of the vehicle are unsupported after the vehicle is lifted. On other lifts (which are typically four post lifts) the outriggers of the two posts on each side of the lift support a platform or “runway” which supports the wheels of the vehicle. Lifts of this second type are often used for wheel alignment work because this type of maintenance requires that the wheels be supported and not hanging freely. Alignment lifts may include rotatable turntables mounted to the runways under the front wheels of the vehicle. These turntables allow the front wheels to be easily turned during the alignment process. 
   A problem with existing post-type lifts is that the outriggers can sag when a load is applied to them. This can cause the runways to become out of level. This problem is particularly detrimental when doing alignment work because the vehicle must be level for the adjustments to be made accurately. What is needed is a lift which allows the outriggers to be leveled to compensate for deflection due to the weight of the vehicle. 
   SUMMARY OF THE INVENTION 
   The present invention comprises a post type automobile service lift wherein each of the outriggers is pivotally connected to its respective carriage for movement about a generally horizontal axis. A respective adjustment mechanism is provided for selectively pivoting each outrigger to compensate for deflection of the outrigger caused by the weight being supported thereon. 
   In the preferred embodiment, each carriage includes a pair of generally vertical side plates. The respective outrigger is pivotally connected between the side plates by a generally horizontal pivot pin. The adjusting mechanism comprises a stop plate mounted between the side plates above the outrigger and inboard of the pivot pin. The stop plate includes a threaded receiver which receives an adjustment bolt. The adjustment bolt has a lower end which is in rotatable contact with an upper surface of the outrigger. By turning the adjustment bolt, a lift operator can raise or lower the outboard end of the outrigger upon which the weight of the vehicle is supported. This allows the operator to level the vehicle and/or the runways. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a four post alignment lift embodying the present invention. 
       FIG. 2  is an enlarged perspective view of one of the carriages of the lift of FIG.  1 . 
       FIG. 3  is a partially cross-sectional view of the carriage of  FIG. 2  taken generally along line  3 — 3  in FIG.  2 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   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. The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof. 
   Certain terminology will be used in the following description for convenience in reference only and will not be limiting. For example, the words “upwardly,” “downwardly,” “rightwardly,” and “leftwardy” will refer to directions in the drawings to which reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the embodiment being described and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof and words of a similar import. 
   Referring to the drawings in more detail, and in particular to  FIG. 1 , the reference number  1  generally designates an alignment lift having four posts  3 . Each post  3  has a carriage  5  which is vertically moveable along the respective post  3 . Each carriage  5  includes an outrigger  7  which extends from the respective carriage  5  toward the centerline of the lift  1 . The outriggers  7  associated with each longitudinal pair of the posts  3  support opposed ends of a respective runway  9 . The runways  9  each include ramps  11  which allow a vehicle (not shown) to be driven onto the runways  9 . The runways  9  may each also include a turntable  13  which supports a respective front wheel of the vehicle and allows the wheel to be easily turned. 
   The carriages  5  are raised and lowered by a conventional drive mechanism  14 , which may be hydraulic, mechanical, or a combination of hydraulic and mechanical components. For example, the drive mechanism  14  may comprise a hydraulic pump  14   a  connected to a respective hydraulic actuator  14   b  mounted in each of the posts  3 . The drive mechanism  14  may further include flexible lifting members or lifting chains  14   c  which are connected between each carriage  5  and a point on the interior of the respective post  3  proximate its base. The lifting chains loop over a roller or sprocket on the respective hydraulic actuator  14   b  such that as the hydraulic actuators  14   b  are extended, the carriages  5  are raised. 
   An alternative drive mechanism  14  (not shown) could comprise a single hydraulic cylinder mounted in one of the runways  9  and connected to each of the carriages  5  through a respective cable and a system of pulleys. Such a drive mechanism is used on the PF-7000ST four post lift sold by Bend-Pak, Inc. In this system, each cable is connected at one end to the ram end of the cylinder and routed, via pulleys, to a respective outrigger. The cable passes through the respective outrigger and into the interior of the respective post. The second end of each cable is connected to a point proximate the top of the respective post. A pulley on each carriage engages the respective cable such that, as the cylinder is retracted, all of the carriages are lifted. Other possible drive mechanisms  14  might substitute pneumatic actuators or screw jacks (not shown) for the hydraulic actuators described above. Winches and cables (not shown) could also be employed as a drive mechanism  14  to raise the carriages  5 . 
   Because each of the carriages  5  is identical to the others, only one of the carriages  5  will be described in detail herein. Referring to  FIG. 2 , the outrigger  7  is formed of rectangular tubing. The carriage  5  includes a pair of side plates  15  spaced apart from one another to receive the outrigger  7  therebetween. The side plates  15  are shown as being substantially L-shaped, having an upper leg  16  connected to the carriage and a lower leg  17  extending outwardly therefrom. Aligned openings are formed through the lower legs  17  of the side plates  15  and the outrigger  7  to receive a pivot pin  18 . The respective runway  9  is supported on the outrigger  7  outboard of the pivot pin  18  such that the runway  9  can be leveled by selectively pivoting the outrigger  7  about the pivot pin  18 . 
   An adjustment mechanism  19  is provided on the carriage  5  for selectively pivoting the outrigger  7 . The mechanism  19  includes a stop plate  21  which is fixedly connected between the side plates  15  of the carriage  5  above the outrigger  7 . The stop plate  21  includes a threaded receiver  23  which receives an adjusting bolt  25 . The adjusting bolt  25  is installed in the receiver  23  such that a lower end of the bolt  25  bears against the top of the outrigger  7  inboard of the pivot pin  18 . The head of the bolt  25  extends upwardly from the stop plate  21  so as to be easily accessible by a technician operating the lift  1 . 
   In use, an automobile is driven onto the runways  9  of the lift  1 . The carriages  5  are then raised to a desired height. Although the carriages  5  will be raised simultaneously to the same general height, there are typically deviations in the heights of the ends of the runways  9  due to uneven loading exerting different forces on each of the outriggers  7 . The technician will, therefore, check the runways to see if they are level. This may be done using any of a variety of known methods including using a bubble level, a laser level, or by measuring the distances between the runways and a known level surface, such as the floor. If the runways  9  are not level, the technician may bring them into level by turning one or more of the adjustment bolts  25  and thereby raising or lowering the respective runway end. Leveling the runways  9  will, in turn, level the vehicle supported thereon. 
   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. For example, it is to be understood that the adjustment mechanism  19  could be relocated to a point below the outrigger  7  and outboard of the pivot pin  18 . Such a location is not preferred, however, because it would make the adjustment bolt  25  less convenient to access and would increase the clearance required between the outrigger  7  and the floor when the carriage  5  is fully lowered. 
   In addition, it is foreseen that each adjustment mechanism  19  could include a linear actuator other than an adjustment bolt  25  to cause the respective outrigger  7  to selectively pivot about the pin  18 . These other actuators could include mechanical, pneumatic, or hydraulic actuators. For example, it is foreseen that a hydraulic actuator (not shown) could be connected between each outrigger  7  and the respective carriage  5  to permit selected pivoting of the outrigger  7  about the pin  18 .