Abstract:
A centering device for a platform lift which includes a lifting mechanism for moving objects from a first to a second height. The lift mechanism has a base, at least a first and a second set of legs, and a platform. The first and second sets of legs each have first opposite ends pivotally secured to the base and the platform, respectively, and second opposite ends provide with traveling members to cooperate with the platform and base, respectively. The platform has a lower portion including a rail upon which the traveling members of the first set of legs traverse. Between the ends of each of the first set of legs, having the traveling members, and the rail, a centering device is disposed to provide alignment of the traveling members and the rails.

Description:
FIELD OF THE DISCLOSURE 
   The disclosure relates to lifts in general, and more specifically to industrial scissor lifts. 
   BACKGROUND OF THE DISCLOSURE 
   Lift type devices have been used for many years, and in various applications. Lift type devices are, however, generally used to raise and lower objects or people from a first elevation to a second elevation. Just as there are various types of lifts and lift type devices, there are many possible power modules capable of performing the required actions necessary to properly utilize the lift. The different power modules may include, but are not limited to, manual input, electric systems, pneumatic systems, and hydraulic systems. 
   One of the many lift type devices, as mentioned above, is a scissor type lift. The scissor lift is named for the scissor like action of a set of legs used to raise and lower the lift. Typically, a scissor lift includes a set of complementary legs which are pivotally attached to each other at their respective centers. The first set of legs is usually pivotally attached to a base at one end, and has attached at the other end, rollers that are adapted to traverse on the underside of a platform. The second set of legs is usually pivotally attached to the platform at one end, and has attached at the other end rollers, that are adapted to traverse on the topside of the base. Disposed between the two sets of legs, is a power module that forces a scissor action, thereby creating the lifting and lowering of the platform. More specifically, the power module pulls and pushes the lower portion of the second set of legs, toward and away from the lower portion of the first set of legs, thereby creating a lifting motion. 
   The modern uses for a scissor lift are many, but scissor lifts are generally used to move large objects between two levels, or to place personnel into higher positions. For example, when transferring loads between a vehicle and a receiving platform or vice versa, it is generally more efficient and secure to transfer the load from the vehicle bed onto an essentially horizontal lift platform, and then onto the receiving platform, than having the load be manually lifted and lowered, inevitably titling the load and shifting or perhaps dropping the content. Similarly, when elevating personnel to higher positions, the scissor lift can provide a large horizontal platform on which to work, thereby giving the personnel a great amount of stability and efficiency. 
   Although the scissor lift is a useful device, having many applications and various benefits, today&#39;s scissor lift technology does have certain drawbacks and limitations, preventing it&#39;s full and efficient use. The area of contact between the rollers and platform, for instance, creates heavy wear, and is often the reason for failure of one of the two components. The wear between these two components is usually caused by several factors, including, but not limited to, the type of material used and misalignment of the components themselves. Similarly, the location of the load, on the platform, must be carefully calculated and placed. More specifically, the size and weight of the load must be taken into consideration, in an attempt to place the center of the load onto the center of the platform. Not centering the load, may cause additional wear on lift components, and may even prevent the lift from working properly. 
   Therefore there still remains the need for an improved lift type mechanism, and more specifically an improved scissor type lift. 
   SUMMARY OF THE DISCLOSURE 
   In accordance with one aspect of the disclosure, a centering device for a scissor lift is provided. The lift, being used for moving objects from a first to a second height may include a base, a first and a second set of legs, a platform, traveling members and a power module. The lower portion of the platform may include a rail upon which the traveling members traverse, the traveling members being connected to the first set of legs. The centering device, being disposed between the end of the first set of legs and the rail, may provide proper alignment between the traveling members, the rail and the platform. 
   In accordance with another aspect of the disclosure, a method of operation for a centering device for a scissor lift is provided. The method may include providing a lift that includes a base, a first and a second set of legs, a platform, traveling members and a power module. The method may entail moving an object or person from a first to a second height, all the while aligning the traveling members, the rail and the platform relative to each other, by disposing a centering device between the end of the first set of legs and the rail. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an isometric view of an industrial scissor lift constructed in accordance with the teachings of the disclosure, 
       FIG. 2  is a cross-sectional view of the scissor lift of  FIG. 1 , taken along line  2 — 2  of  FIG. 1 , 
       FIG. 3  is a cross-sectional view of the scissor lift of  FIG. 1 , taken along line  3 — 3  of  FIG. 2 , 
       FIG. 4A  is a cross-sectional view of the scissor lift of  FIG. 1 , taken along line  4 A— 4 A of  FIG. 1 ; 
       FIG. 4B  is a cross-sectional view of the scissor lift of  FIG. 1 , taken along line  4 B— 4 B of  FIG. 1 ; and 
       FIG. 5  is an isometric view of a two-scissor scissor lift constructed in accordance with the teachings of the disclosure. 
   

   While the disclosure is susceptible to various modifications and alternative constructions, certain illustrative embodiments thereof have been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the disclosure to the specific forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the disclosure as defined by the appended claims. 
   DETAILED DESCRIPTION 
   Referring to  FIG. 1 , a scissor lift  20  may include a base  30  and a platform  40 , having disposed therebetween a first pair of legs  50  and a second pair of legs  60  mounted in a scissor like manner, and a power unit  70 , operatively connected between the first pair of legs  50  and the second pair of legs  60 . 
   As shown in  FIGS. 1 and 4B , the base  30  may be of general rectangular shape, and may be manufactured from steel, but may also be manufactured from any other suitable material. The base  30  may also be mounted to the floor, adding stability and strength to the lift  20 . The lift  20 , however, may also be mobile, enabling the lift  20  to be moved to and from different locations. Therefore, wheels may be mounted to the base  30 , or the base  30  may be mounted on a wholly independent vehicle. The base  30  may further include a substantially flat bottom surface, framed by a substantially vertical wall. A first pivot mount  32  and a second pivot mount  34  may be fixedly connected to the base  30 . For example, the mounts  32 ,  34  may be welded to the base  30 . The first mount  32  may be adapted to receive a first pivot pin  36  and the second mount  34  may be adapted to receive a second pivot pin  38 . 
   Referring to  FIGS. 2 ,  4 A, and  4 B the first set of legs  50 , or “lower-mount” legs, may include two relatively parallel legs  50   a  and  50   b  that may be fixedly attached to each other at their respective centers or at their respective ends as at  51  ( FIG. 2 ). The two legs  50   a  and  50   b  which make up the first set of legs  50  may have an elongated rectangular shape, including respective inside surfaces  52   a  and  52   b  and outside surfaces  54   a  and  54   b , and may be situated such that the inside surfaces  52   a  and  52   b  of the two legs  50   a  and  50   b  are facing each other. Disposed at the lower or proximal ends  56   a  and  56   b  of each of the first set of legs  50 , may be apertures  57   a  and  57   b , such as mounting holes, which may be adapted to receive the first pivot pin  36  and the second pivot pin  38 , respectively, thereby pivotally mounting the lower-mount legs  50  to the base  30 . 
   As shown in  FIG. 2 , located at the upper or distal ends  58   a  and  58   b  of the lower-mount legs  50 , may be apertures, adapted to receive respective shafts  61   a  and  61   b . The shafts  61   a  and  61   b  may be adapted to receive respective traveling members  62   a  and  62   b , such as rollers, which may then be mounted adjacent the outside surfaces  54   a  and  54   b  of the lower mount legs  50 . Positioned above the rollers  62   a  and  62   b , on the outside surfaces  54   a  and  54   b  of the distal ends  58   a  and  58   b  of the lower mount legs  50 , may be respective counterbores  67   a  and  67   b . Housed within the counterbores  67   a  and  67   b , and adapted to abut a set of rails  64   a  and  64   b , may be respective centering devices  66   a  and  66   b , which may be round in shape, and may be manufactured from low friction material such as Nylatron®. 
   The platform  40  may rest upon the rollers  62   a  and  62   b , and more specifically, the rails  64   a  and  64   b , which may be fixedly attached to the bottom of the platform  40 , may rest upon the rollers  62   a  and  62   b . The rollers  62   a  and  62   b  may be industrial wheels which are designed to withstand a specific weight and/or a specific number of uses. The rails  64   a  and  64   b  may be of a general rectangular shape, with respective horizontal lower surfaces  63   a  and  63   b  acting as traveling member tracks or contact points, and with respective vertical sides  65   a  and  65   b  acting as guides by insuring the traveling members  62   a  and  62   b  stay in contact with the rails  64   a  and  64   b . The platform  40  may also be of generally rectangular shape, and approximately equal in size to the base  30 . The upper surface of the platform  40  may be generally level or horizontal, and may be adapted to lift objects and people. A skirt  72  may extend from the perimeter of the platform down in the vertical direction, which may prevent the exposition of the underside of the platform  40 . 
   Referring to  FIG. 4A , a third pivot mount  74  and fourth pivot mount  76  may be fixedly connected to the platform  40 . The third pivot mount  74  may be adapted to receive a third pivot pin  78  and the fourth pivot mount  76  may be adapted to receive a fourth pivot pin  80 . As shown in  FIG. 1 , the second set of legs or “upper mount” legs  60  may be pivotally attached to the lower mount legs  50  via a shaft  88  disposed near the center of the legs. 
   Referring to  FIGS. 1 and 4A , the upper-mount legs  60 , may also include two legs  60   a  and  60   b  that may be fixedly attached and relatively parallel to each other. The two legs  60   a  and  60   b  that make up the upper-mount set of legs  60 , may be similar to the legs  50   a  and  50   b  that comprise the lower-mount legs  50  in that they each may have an elongated rectangular shape, including an inside surface and an outside surface, and may be situated such that the inside surfaces of the two legs  60   a  and  60   b  are facing each other. Disposed at the top or distal ends  84   a  and  84   b  of each of the upper mount legs  60 , may be an aperture, such as a mounting hole, that may be adapted to receive the third pivot pin  78  and the fourth pivot pin  80 , respectively, which may in conjunction with the third pivot mount  74  and the fourth pivot mount  76 , pivotally mount the upper-mount legs  60  to the platform  40 . Located at the lower or proximal ends  86   a  and  86   b  of the upper-mount legs  60 , may be apertures adapted to receive shafts  87   a  and  87   b . The shafts  87   a  and  87   b  may be adapted to receive traveling members  89   a  and  89   b , such as rollers, that may be adapted to traverse along the flat bottom surface of the base  30 . 
   More specifically, the shaft  88  may span completely through the first set of legs  50  and the second set of legs  60 , wherein the center of the lower-mount legs  50  may be adapted to rotatably receive the shaft  88 , and the center of the upper-mount legs  60  may be adapted to fixedly receive the shaft  88 . It is also conceivable that the shaft  88  may be replaced by two separate shafts, thereby eliminating the presence of the shaft spanning between the sets of legs  50  and  60 . As for other possible features, the shaft  88  may also include additional components, such as bearings, retaining rings and grease fittings to better accomplish the pivoting of the sets of legs relative to each other. 
   The movement of the lift  20  may be assisted by many different types of power units  70  (see  FIG. 1 ), including, hydraulic, electric and pneumatic units. The hydraulic unit may include a piston  90 , a cylinder  92  and a high pressure pump (not shown). As one skilled in the art will know, the hydraulic unit may have more than one pump, and more than one piston  90  and cylinder  92 . To create the motion and force necessary to move the lift  20 , hydraulic liquid may be pushed by the pump into the cylinder  92 . The cylinder  92 , now housing an increase of high pressure fluid, may concentrate the high pressure of the fluid toward the piston  90 , enabling the piston  90  to move. 
   In operation, one objective of the lift  20  may be to move an object from a first position to a second position. The object being moved may be of a great variety of shapes, sizes and weight, ranging from small to large and from light to heavy objects, not excluding people. The distance the object may be moved, may also vary from lift to lift depending on the amount of travel that is required for a specific application. 
   To accommodate for the variety of distances necessary to move objects, several techniques may be employed. The sets of legs  50 ,  60  for instance, may be made longer or shorter depending on the application, thereby relatively increasing or decreasing the amount of vertical travel obtained. Similarly, multiple sets of legs (scissors) may be added, thereby increasing the amount of travel by a multiple of the number of scissors in the lift. For example, the scissor action of the first set of legs  50  and second set of legs  60 , being a single scissor, may combine for a vertical travel of X. The addition of a third set of legs  100  and fourth set of legs  110  as shown in  FIG. 5 , now providing a double scissor, may increase the vertical travel to 2X, etc. 
   It should be realized that the addition of a set of scissors adds to the linkage configuration of the lift, whereby the legs  50   a  and  50   b  of the first set of legs  50  are pivotally attached to the corresponding legs  110   a  and  110   b  of the fourth set of legs  110  as at  112   a  and  112   b , respectively, wherein the legs  50   a  and  50   b  comprise first links and the legs  110   a  and  110   b  comprise second links. Similarly, the legs  60   a  and  60   b  of the second set of legs  60  are pivotally attached to the corresponding legs  100   a  and  100   b  of the third set of legs  100  as at  114   a  and  114   b , respectively, wherein the legs  60   a  and  60   b  comprise third links and the legs  100   a  and  100   b  comprise fourth links. With this arrangement, the first and third links comprised of sets of legs  50  and  60  may be pivotally connected by the shaft  88  disposed near the center of the legs  50   a ,  50   b , and  60   a ,  60   b  and the second and fourth links comprised of sets of legs  100  and  110  may be pivotally connected by a shaft  116  disposed near the center of the legs  100   a ,  100   b  and  110   a ,  110   b.    
   As additional scissors or combinations of legs are added, more links are provided, but the basic scissor principle remains the same. As shown in  FIG. 5 , the only requirement is for one of the linkages (such as the first links  50   a  and  50   b ) to be pivotally mounted to the base  30 , and the other of the linkages (such as the third links  60   a  and  60   b ) to have traveling members cooperating with the base  30  and, similarly, for one of the linkages (such as the second links  110   a  and  110   b ) to be pivotally mounted to the platform  40  and the other of the linkages (such as the fourth links  100   a  and  100   b ) to have traveling members cooperating with the platform  40 . 
   In order to understand the operation of the scissor lift, the single-scissor embodiment of  FIGS. 1–4B  wherein, to initiate the lifting process, the power module  70 , such as the illustrated hydraulic system, is activated. The pumping mechanism and fluid storage (not shown) for the hydraulic system may be located within the area bounded by the first set of legs  50 , and the pistons  90  and the cylinders  92  may be located in the area bounded by the second set of legs  60 . Upon activation, the fluid entering the cylinders  92  may force the pistons  90  outward and, similarly, when the fluid is removed from the cylinders  92 , the pistons  90  may retract into the cylinders  92 . The cylinders  92 , being fixedly attached to the second set of legs  60  near the distal ends  86   a  and  86   b  of the legs  60   a  and  60   b , and the pistons  90 , being operatively attached to a pivot bar  94 , may create in combination, the motion and force necessary for lifting the object. 
   The pivot bar  94  may be a one piece bar or rod, but it may also consist of more than one piece depending on the lift. For example, a lift that utilizes a single pivot bar, may have the pivot bar extend through the center of the lower-mount legs  50  and the center of the upper-mount legs  60 , thereby providing the sets of legs  50 ,  60  a point about which to pivot. The pivot bar  94 , may also comprise or be a part of the shaft  88 . Similarly, a lift that utilizes two discrete pivot bars may have one of the pivot bars associated with corresponding lower-mount and upper-mount legs  50   a  and  60   a , while the other of the pivot bars may be associated with corresponding lower-mount and upper-mount legs  50   b  and  60   b . Fixedly attached to the pivot bar  94 , may be yokes  96 , that are adapted to secure the pistons  90  as with pins  98 . More specifically, the yokes  96  may be fixedly attached to the pivot bar or bars  94 , and have disposed at the opposite end apertures, adapted to receive the pins  98 . Furthermore, the yokes  96  may be positioned on the pivot bar or bars  94  in such a manner, as to properly leverage the power from the power module  70 , to thereby optimize the effectiveness and efficiency of the lift  20 . 
   When in the lowered position, the platform  40  of the lift  20  may rest on or near the ground, so that the load may be easily placed on to the platform  40 . Off-center loading of the platform  40  may have little or no effect when the lift  20  is in the resting position, but may greatly affect the wear and efficiency of the components once the lift  20  is in motion. When placing the load toward one of the sides of the platform  40 , the platform  40  may have a tendency to twist or turn depending on the exact placement and weight of the load. 
   As the power module  70  is activated, the traveling members  62   a  and  62   b  mounted on the distal ends  58   a  and  58   b  of the lower mount legs  50  (lower mount rollers) may begin to traverse along the rails  64   a  and  64   b  on the underside of the platform  40 , while simultaneously, the traveling members  62   b  mounted on the distal ends  86   a  and  86   b  of the upper mount legs  60  (upper-mount rollers) may begin to traverse along the upper side of the base  30 . More specifically, the lower-mount rollers  62   a  and  62   b  may begin to traverse along the rails  64   a  and  64   b  toward the third and fourth pivot mounts  74 , 76 , and the upper-mount rollers  89   a  and  89   b  may begin to traverse toward the first and second pivot mounts  32 ,  34 , creating the vertical displacement of the platform  40 . 
   As the vertical displacement occurs, several forces, including that of the load may distribute unevenly among the components. These uneven distributions, in turn, may create tensions and areas of concentrated forces between the components, leading to misalignment between the traveling members  62   a  and  62   b  and the rails  64   a  and  64   b , and similarly, to misalignment between the first and the second sets of legs  50 ,  60 , the platform  40  and the base  30 . Aiding in the reduction of tension and reducing areas of concentrated forces, the centering devices or guides  66   a  and  66   b , being located within the respective bores  67   a  and  67   b , and disposed between the outside surfaces  54   a  and  54   b  of the of legs  50   a  and  50   b  and the corresponding rails  64   a  and  64   b , may strategically ensure the proper alignment of the different lift components. 
   For example, if a load is placed on the outside edge of the platform  40 , the platform  40  may have a tendency to tilt to the load bearing side, thereby misaligning the lower mount rollers  62   a  and  62   b  and the corresponding rails  64   a  and  64   b , or possibly fully concentrating the weight of the platform  40  on a single roller, while raising or distancing the other roller from its rail. If the lower mount rollers  62   a  and  62   b  and the corresponding rails  64   a  and  64   b  are misaligned, or whether one the rollers bears the entire weight of the platform  40  and its load, several components, such as the rollers  62   a  and  62   b , the rails  64   a  and  64   b  and the first and second sets of legs  50  and  60 , may experience extensive wear. More specifically, as the platform  40  tilts or moves toward one side, the roller  62   a  may undergo significant sliding friction against the corresponding rail  64   a , the leg  50   a  may grind and rub against the corresponding rail  64   a , and the roller  62   a  may grind against the corresponding leg  50   a . The centering guides  66   a  and  66   b , however, prevent the misaligning of the lower mount rollers  62   a  and  62   b  with their corresponding rails  64   a  and  64   b , and prevent the rollers from raising or distancing themselves from the rails or experiencing significantly uneven forces or wear, by limiting or eliminating the unwanted play between the components, and by ensuring that the components, such as the first and second sets of legs  50  and  60 , the rails  64   a  and  64   b  and the corresponding rollers  62   a  and  62   b , are aligned. As a consequence of alignment of the different components, due to the centering guides  66   a  and  66   b , the platform  40  and the base  30  may be able to achieve continued and substantial parallelism. More specifically, the centering devices  66   a  and  66   b  may be fixedly attached to the outside surfaces  54   a  and  54   b  of the distal ends  58   a  and  58   b  of the lower mount legs  50 , and disposed between the legs  50   a  and  50   b  thereof and the corresponding rails  64   a  and  64   b . As the rollers  62   a  and  62   b  traverse along the corresponding rails  64   a  and  64   b , they may contact the corresponding inside surfaces  65   a  and  65   b  of the rails  64   a  and  64   b , thereby preventing legs  50   a  and  50   b  from contacting the corresponding rails  64   a  and  64   b  and ensuring that the rollers  62   a  and  62   b  remain substantially perpendicular to and in alignment with the corresponding rails  62   a  and  62   b  at all times. 
   Similarly, when the load is placed on the center of the platform  40 , the centering devices  66   a  and  66   b  are still an integral part of the lift  20 , ensuring alignment of the various components such as the rollers  62   a  and  62   b , the rails  64   a  and  64   b , and the first and second sets of legs  50  and  60 . For example, even though the load is placed on the center of the platform  40 , the centering devices  66   a  and  66   b  prevent the rollers  62   a  and  62   b  from rubbing and grinding against the respective legs  50   a  and  50   b , by demanding a slight distance or separation between the legs  50   a  and  50   b  and their corresponding rollers  62   a  and  62   b.    
   The foregoing detailed description has been given for clearness of understanding only and no unnecessary limitations should be understood therefrom, as modifications will be obvious to those skilled in the art.