Scissor lift

A scissor lift comprises a load support, a lift support and at least one scissor assembly defined between the load support and the lift support, the at least one scissor assembly being driven into an open or a closed position by a drive device that enables movement of the load support relative to the lift support with the opening and closing of the at least one scissor assembly, wherein the at least one scissor assembly is further defined by a pair of arms attached at a pivot, and where the pair of arms further comprises a curved outer surface that engages a portion of a drive device for urging the scissor arms apart and for moving the load support relative to the lift support.

FIELD OF THE INVENTION

The present invention relates to scissor lifts in general, and more particularly to, in one embodiment, a low profile scissor lift having curved legs with improved mechanical advantage.

BACKGROUND

Traditional scissor lifts are defined by a scissor assembly driven by a motor or the like that is placed on the ground or the base of the lift. The motor is typically connected to the scissor assembly by a piston and cylinder, whereby the motor activates the piston and cylinder against the scissor assembly to force the scissor assembly from a collapsed position into an extended position. This configuration traditionally requires a large amount of power or force, or an oversized motor, to initiate movement of the scissor assembly because of the poor mechanical advantage of a scissor assembly when started from a completely collapsed condition. Thus, the power required to operate a scissor lift from a fully collapsed condition to a fully extended condition is inconsistent, with more power needed at the beginning and less power needed toward the end of the extension. Moreover, because of the large power requirements at the beginning, the motor tends to be oversized and bulky. In addition, traditional scissor lifts tend to have an extended profile due to the configuration of the scissor arm assemblies, which results in an unnecessary allocation of vertical space.

SUMMARY

The scissor lift of one embodiment of the present invention comprises a load support, a lift support, and a plurality of scissor assemblies attached between the load support and the lift support. The scissor assemblies are driven into an open or a closed position by a drive device that enables movement of the load support relative to the lift support with the opening and closing of the scissor assemblies. Each scissor assembly is further defined by a pair of arms attached at a pivot. Each arm is further defined by an inside section and a curved, outside section, wherein a linear relationship is defined between the curvature of the curved, outside section and a relative movement experienced between the load support and the lift support during the opening or closing of the scissor assemblies. In another embodiment, a single scissor assembly is provided with curved arm surfaces that function in a similar manner. The linear relationship defined by the curved sections of the scissor arms and the movement of the roller assemblies and the movement of the load support results in a consistent power requirement at the drive device with improved mechanical advantage and a compact profile. Such a compact profile benefits from the use of a smaller drive device positioned between the scissor arms or the scissor assemblies, rather than a large and bulky drive device that must be supported on the ground or the base of the lift support.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure describes the best mode or modes of practicing the invention as presently contemplated. This description is not intended to be understood in a limiting sense, but provides an example of the invention presented solely for illustrative purposes by reference to the accompanying drawings to advise one of ordinary skill in the art of the advantages and construction of the invention. In the various views of the drawings, like reference characters designate like or similar parts.

FIG. 1is a perspective view of one embodiment of a scissor lift100, generally comprising a load support200, a lift support300, and a plurality of scissor assemblies400a,400b,400c, and400d(collectively referred to as scissor assemblies400) attached between the load support200and the lift support300. The scissor assemblies400enable movement of the load support200relative to the lift support300between an extended position shown inFIG. 1and a collapsed position shown inFIG. 2, with the opening and closing of the scissor assemblies400. The load support200is typically provided with a solid top210that is intended to transport a load (not shown) such as a vehicle, for example, that might be lifted between a first elevation (FIG. 2) to a second elevation (FIG. 1). For example, the scissor lift100might be used as an elevator to transport a vehicle between various levels in a parking garage (not shown). While a solid, rectangular top210is shown, it will be appreciated that the top may not be solid or rectangular, and may be any shape or construction desired as long as the load support200is able to support a load for which it is intended. Other load support constructions are possible. The lift support300is typically supported on or anchored to a planar surface such as the ground or a foundation, and may further comprise a pair of lift support rails310and320as shown. The lift support300may also be constructed in the form of a platform (not shown) similar to the top210of the load support200. Other lift support constructions are possible.

FIG. 1illustrates scissor assemblies400aand400blocated on one end240,340of the load and lift supports200,300respectively, and scissor assemblies400cand400dlocated on the other end260,360of the load and lift supports200,300respectively. While four scissor assemblies400a-400dare illustrated, it will be appreciated that only one or at least one scissor assembly may be used as described below in connection with the embodiment ofFIGS. 6-15, or that only one scissor assembly may be located on one end240,340of the load and lift supports200,300respectively, and one scissor assembly may be located on the other end260,360of the load and lift supports200,300respectively. For purposes of convenience in the embodiment ofFIG. 1throughFIG. 5, and with reference to the front view ofFIG. 3, there will be described one scissor assembly410located on one end240,340of the load and lift supports200,300respectively, and one scissor assembly430located on the other end260,360of the load and lift supports200,300respectively.

As illustrated in the embodiment ofFIG. 3, scissor assembly410is further defined by a pair of arms412,416, attached at a pivot415, each arm further defined by an inside section413,417, and a curved, outside section414,418. Similarly, scissor assembly430is further defined by a pair of arms432,436, attached at a pivot435, each arm further defined by an inside section433,437, and a curved, outside section434,438. The inside sections413,417and433,437of the scissor assemblies410,430face each other, while the outside sections414,418and434,438face away from each other. The inside sections are preferably linear or straight, although they could have other configurations. The outside sections are preferably curved as will be described below. Each arm of each scissor assembly is connected to both the load support200and the lift support300such that the opening and closing of the scissor assemblies (as will be described below) results in a vertical movement of the load support200relative to the lift support300. This is achieved by fixing certain arm sections relative to each of the load and lift supports and allowing certain arm sections to move, slide, or otherwise translate relative to such supports.

More specifically, in the embodiment ofFIG. 3, outside sections414and418of scissor assembly410are fixed to the load support200and lift support300respectively through rotatable connections245and345respectively that allow the outside sections414and418to rotate in place relative to the load and lift supports. Inside sections437and433of scissor assembly430are similarly fixed to the load support200and lift support300respectively through similar connections270and370(see alsoFIG. 4) respectively. On the other hand, inside sections417and413of scissor assembly410are connected to the load support200and lift support300respectively through movable connections250and350respectively, while outside sections434and438of scissor assembly430are connected to the load support200and lift support300respectively, through movable connections265and365respectively. As shown in the embodiment ofFIG. 4, one type of movable connection265and365includes a roller431and439mounted on the end of the outside sections434and438, respectively, that roll along sections267and367in the load and lift supports200and300, respectively as the scissor assemblies move between an open and closed position. Other types of movable connections are possible, including, but not limited to, a pin and slot type connection. WhileFIG. 3illustrates a certain combination of fixed and movable connections, it will be appreciated that other configurations are possible as long as the same result is achieved, namely the movement of the load support200in a vertical plane relative to the lift support300.

The scissor assemblies of the embodiment ofFIG. 1throughFIG. 5are opened or extended through the use of a drive assembly500as shown inFIGS. 1 and 3, for example, which controls the opening and closing of the scissor assemblies that enable movement of the load support200relative to the lift support300. The drive assembly500of the illustrated embodiment includes a drive device510, such as a motor, supported by a drive assembly platform520that is fixed to and supported by the pivots415and435, which are preferably pivot shafts connecting the scissor assemblies. By aligning the drive assembly platform520with the pivots415and435, the drive assembly500is maintained in a constant orientation relative to a defined plane between the load and lift supports200and300. The drive device510drives a first roller assembly610associated with the first scissor assembly410and a second roller assembly630associated with the second scissor assembly430, the drive device510driving the first and second roller assemblies610,630via first and second drive shafts620,640respectively. In the illustrated embodiment, the drive shafts620,640are screw shafts that rotate in opposite directions relative to the drive device510when driven thereby.

As shown in the embodiment ofFIG. 4andFIG. 5, roller assembly630further comprises a bracket632including a threaded nut634and guide636that receives drive shaft640therethrough. The roller assembly630further comprises a pair of rollers645on opposite ends of the bracket632that contact the outside sections of the scissor assemblies. When the drive device510drives the drive shafts620,640in one direction, both roller assemblies610,630are drawn toward the drive510through the engagement of the screw shafts with the threaded nuts on the roller assembly brackets, which forces the rollers645against the outside sections of the scissor assemblies, which causes the arms of the scissor assemblies to separate relative to the pivots, which causes the load support200to move away from or elevate relative to the lift support300. Similarly, when the drive device510drives the drive shafts620,640in the opposite direction, both roller assemblies610,630are forced away from the drive510, which causes the rollers645to travel down the outside sections of the scissor assemblies, which causes the arms of the scissor assemblies to close relative to the pivots, which causes the load support200to move toward or collapse relative to the lift support300. The movement of the scissor arms is facilitated in the illustrated embodiment by the movement of the rollers431,439(seeFIG. 4) along the tracks267,367respectively, and the rotation of the fixed ends of the scissor arms relative to the load and lift supports.

The curved configuration of the outside sections of the scissor arm assemblies results in a linear relationship between the movement of the load support200relative to the lift support300and the movement of the roller assemblies610,630along the curved, outside sections of the scissor assemblies. More specifically, movement of the roller assemblies along a unit distance results in the load support moving relative to the lift support through a distance that is a consistent multiple of the unit distance, where such multiple can be a fraction or an integer. In one example, for every inch that the rollers move along the scissor arms, the load support would move one and one-half inches. This result is achieved with a curved outside section having a radius of curvature of approximately twenty-five inches. Other dimensional variations are possible.

The use of curved outside sections also minimizes the power required by the drive device to initiate movement in the load support because the movement of the rollers is consistent along the entirety of the curved outside sections regardless of the height of the load platform relative to the lift platform. Thus, a drive device with a consistent power requirement and improved mechanical advantage is a benefit and feature of the present invention.

In addition, the construction of the scissor assemblies and their connection to the load and lift supports, in combination with the unique drive assembly, results in a compact profile that is more versatile and is capable of being used in a variety of environments. Such a compact profile benefits from the use of a smaller drive device positioned between the scissor assemblies, rather than a large and bulky drive device that must be supported on the ground or the base of the lift support. For example, where excessive room might have been necessary for a rack and pinion type of lift, one is able to use the scissor lift of the embodiments described above with reduced space requirements and a compact storage profile. In one embodiment, a scissor lift constructed in accordance with an embodiment described herein has a fully collapsed or compacted height of ten inches, with a vertical travel of two feet, which results in an overall height from the base of the lift support to the top of the load support of almost three feet. Other dimensional achieves are possible.

FIGS. 6-15illustrate an alternative embodiment of a scissor assembly700that would be attached between a load support800and a lift support900for enabling movement of the load support800relative to the lift support900between an extended position shown inFIGS. 5,6, and12-15and a collapsed position shown inFIGS. 8-11, with the opening and closing of the scissor assembly700driven by a drive assembly1000. The load support800is typically provided with a solid top that is intended to transport a load (not shown) such as a vehicle, for example, although other than a solid top may be used. In certain embodiments, the load support800is shown with a cover member805, while in other embodiments and figures the cover member805is not shown to better illustrate elements of the scissor assembly700. Similarly, in certain embodiments, the drive assembly1000is shown with a cover member1005, while in other embodiments and figures the cover member1005is not shown to better illustrate elements of the drive assembly1000. The lift support900is typically supported on or anchored to a planar surface such as the ground or a foundation and can assume a variety of constructions as described previously in connection with the previous embodiment. While the previous embodiment ofFIGS. 1-5described a plurality of scissor assemblies between a load support and a lift support, the embodiment ofFIGS. 6-15illustrates only a single scissor assembly700. However, it is understood that while at least one scissor assembly is preferred, more than one scissor assembly may be used.

Scissor assembly700is further defined by a pair of arms710,730, attached at a pivot720, each arm further defined by a plurality of curved surfaces712,716on arm710and732,736on arm730, and a plurality of preferably non-curved surfaces714,718on arm710and734,738on arm730as shown inFIGS. 12-13. The non-curved surfaces are preferably linear or straight, although they could have other configurations. Each arm710,730of the scissor assembly700is connected to both the load support800and the lift support900such that the opening and closing of the scissor assembly (as will be described below) results in a vertical movement of the load support800relative to the lift support900. This is achieved by fixing certain arm sections relative to each of the load and lift supports and allowing certain arm sections to move, slide, or otherwise translate relative to such supports.

More specifically as illustrated in the embodiment ofFIGS. 12-13, first ends713,733of scissor arms710,730are attached to the load support800and lift support900respectively through a pair of fixed, rotatable connections845and945respectively that allow the first ends713,733to rotate in place within the rotatable connections845,945relative to the load and lift supports. On the other side of the scissor assembly700, second ends717,737of scissor arms710,730are attached to the load support800and lift support900respectively through a pair of movable, rotatable connections847and947respectively that allow the second ends717,737to both rotate in place within the rotatable connections847,947and move relative to the load and lift supports. As shown in the embodiment ofFIGS. 7 and 12, one type of movable connection847,947includes a bracket850,950having slots852,952for the extension of pins or fasteners854,954extending from the load support800and lift support900respectively. While the pins or fasteners are854,954are fixed to the load support800and lift support900respectively, the slotted brackets850,950are capable of translating relative to the fasteners854,954during the opening and closing of the scissor assembly700. Other types of movable connections are possible, including, but not limited to, roller connections as previously described and other connections. While the embodiments ofFIGS. 6-15illustrate a certain combination of fixed and movable connections, it will be appreciated that the fixed and movable connections can be reversed, and other configurations are possible as long as the same result is achieved, namely the movement of the load support800relative to the lift support900.

The scissor assembly700of the embodiment ofFIG. 6throughFIG. 15is opened or extended through the use of a drive assembly1000that includes a drive device1010, such as a motor, supported by a drive assembly platform1020that is attached to a central shaft1030by bearings on either side of the pivot720, which maintains the drive assembly1000in a constant orientation relative to a defined plane between the load and lift supports800and900. The drive assembly1000further comprises a belt drive1015driven by the drive device1010that engages the central shaft1030that is threadedly engaged with a first roller assembly1050associated with the curved surfaces712,732on the scissor arms710,730, and a second roller assembly1060associated with the other curved surfaces716,736. The first and second roller assemblies1050,1060(FIGS. 6-7) respectively further comprise a plurality of rollers1052,1062(FIG. 13) attached to an axle1054,1064(FIG. 14) that is connected to the central shaft1030by a plurality of yokes1056,1066(FIG. 14) that are each axially translated, through the rotation of the central shaft1030, toward or away from the pivot720. In the illustrated embodiment, the central shaft1030is attached to a threaded shaft1032on one side of the pivot720and an oppositely threaded shaft1034on the other side of the pivot720, each threaded shaft1032,1034engaging its respective yoke1056,1066such that the yokes1056,1066are simultaneously drawn toward or moved away from the central pivot720region.

FIGS. 8-11illustrate an embodiment of the scissor assembly700in the closed position with the load support800lowered relative to the lift support900and with the rollers1052,1062fully extended relative to the central pivot720such that the roller axles1054,1064are substantially aligned with the first ends713,733and second ends717,737of the scissor arms710,730respectively (FIG. 9). When it is desired to raise the load support800relative to the lift support900, the drive device1010engages the central shaft1030via the belt drive1015to cause the threaded shafts1032,1034to engage the yokes1056,1066and draw them toward the pivot720, which urges the rollers1052and1062against the curved surfaces712,732and716,736respectively, which causes the arms710,730of the scissor assembly to separate relative to the pivot720, which causes the load support800to move away from or elevate relative to the lift support900. Similarly, when the drive device1010drives the drive shaft1030in the opposite direction, both roller assemblies1050,1060are forced away from the pivot720, which causes the rollers1052,1062to travel down the curved surfaces712,732and716,736of the scissor arms710,730, which causes the arms of the scissor assemblies to close relative to the pivot720, which causes the load support800to move toward or collapse relative to the lift support900. The movement of the scissor arms710,730is further facilitated by the movement of the movable, rotatable connections847and947relative to the load and lift supports, and more specifically, in the currently described embodiment by the lateral movement of the second ends717,737relative to the first ends713,733during the rotation of the scissor arms710,730around the pivot720.

The curved surfaces712,732and716,736of the scissor arm assembly700results in a linear relationship between the movement of the load support800relative to the lift support900and the movement of the roller assemblies1050,1060along the curved surfaces. More specifically, movement of the roller assemblies along a unit distance results in the load support moving relative to the lift support through a distance that is a consistent multiple of the unit distance, where such multiple can be a fraction or an integer. In one example, for every inch that the rollers move along the scissor arms, the load support would move one and one-half inches. This result is achieved with a curved outer surface having a radius of curvature of approximately twenty-five inches. Other dimensional variations are possible.

For all of the previously-described embodiments, the use of curved outside sections or surfaces also minimizes the power required by the drive device to initiate movement in the load support because the movement of the rollers is consistent along the entirety of the curved outside sections or surfaces regardless of the height of the load support relative to the lift support. Thus, a drive device with a consistent power requirement and improved mechanical advantage is a benefit and feature of the present invention.

Similar to the earlier-described embodiment, the construction of the scissor assembly and its connection to the load and lift supports, in combination with a unique drive assembly that is supported by the central shaft and situated between the load and lift supports, also results in a compact profile that is more versatile and is capable of being used in a variety of environments. Such a compact profile benefits from the use of a smaller drive device positioned along the pivot plane, rather than a large and bulky drive device that must be supported on the ground or the base of the lift support.