Patent Description:
Certain aerial work platforms, known as scissor lifts, include a frame assembly that supports a platform. The platform is coupled to the frame assembly using a system of linked supports arranged in a crossed pattern, forming a scissor assembly. As the supports rotate relative to one another, the scissor assembly extends or retracts, raising or lowering the platform relative to the frame. Accordingly, the platform moves primarily or entirely vertically relative to the frame assembly. Scissor lifts are commonly used where scaffolding or a ladder might be used, as they provide a relatively large platform from which to work that can be quickly and easily adjusted to a broad range of heights. Scissor lifts are commonly used for painting, construction projects, accessing high shelves, changing lights, and maintaining equipment located above the ground. <CIT> discloses an elevating device according to the preamble of claim <NUM>, in particular having one or more pairs of crossed scissors members, each member having at least two telescoping sections. The scissors members are mounted for pivotal movement with respect to each other, and means are included for interconnecting opposed scissors members for effecting extension of the telescoping sections in response to the pivoting of the scissors members. <CIT> discloses an elevator, for example, a commercial aircraft cargo loading elevator, utilizing a scissors-type lifting linkage, wherein the variation of the lifting force required by the lifting actuator means is minimized during the entire lifting cycle by utilizing scissors-type linkage pivot means offset below the planes formed by the two frames and attaching the lifting means above the plane of one of said frames.

One embodiment relates to a lift device including a base, a platform configured to support an operator and a scissor assembly coupling the base to the platform, the scissor assembly including: a first scissor layer including a first inner arm pivotally coupled to a first outer arm, wherein the first inner arm is configured to rotate relative to the first outer arm about a first middle axis, and wherein the first scissor layer has a first end axis center point; a second scissor layer coupled to the first scissor layer, the second scissor layer including a second inner arm pivotally coupled to a second outer arm, wherein the second inner arm is configured to rotate relative to the second outer arm about a second middle axis, wherein the second scissor layer has a second end axis center point; and an actuator configured to move the platform between a fully raised position and a fully lowered position relative to the base,wherein the first middle axis is offset vertically from the first end axis center point, wherein the second middle axis is offset vertically from the second end axis center point, and wherein the first middle axis is offset vertically from the second middle axis; and wherein the first inner arm has an upper end defining a first end axis and a lower end defining a second end axis, and wherein a distance between the first end axis and the second end axis is fixed.

The invention is capable of other embodiments and of being carried out in various ways. Alternative exemplary embodiments relate to other features and combinations of features as may be recited herein.

According to an exemplary embodiment, a scissor lift includes a base, a platform configured to support at least one operator, and a lift assembly coupled to the base and the platform and configured to raise and lower the platform relative to the base. The lift assembly includes a series of scissor layers arranged on top of one another. Each scissor layer includes a pair of inner scissor arms pivotally coupled to a pair of outer scissor arms. The inner scissor arms of each scissor layer are pivotally coupled to the outer scissor arms of the adjacent scissor layers. The bottom scissor layer is coupled to the base, and the top scissor layer is coupled to the platform. One or more actuators rotate the scissor arms relative to one another such that the overall length of the scissor assembly changes, raising and lowering the platform.

Within each scissor layer, the inner arms are pivotally coupled to the outer arms about a middle axis that extends laterally. If this middle axis is placed in the center of the inner arms and the outer arms, the distance between the bottom ends of the inner and outer arms will be the same as the distance between the top ends of the inner and outer arms. However, placing a pin in this location can have a negative effect on the strength of the inner arms and outer arms. If the lateral axis is offset above or below the center of the inner arms and the outer arms, the distance between the bottom ends of the inner and outer arms will not be the same as the distance between the top ends of the inner and outer arms. This results in longitudinal movement of the platform. This longitudinal movement is undesirable, as it can cause the platform to contact other objects. By way of example, if the scissor lift is placed adjacent a wall, this movement can cause the platform to contact the wall, potentially damaging the wall or the scissor lift. However, offsetting the pin is advantageous, as the reduction in strength caused by placing a pin in the centers of the scissor arms can be avoided.

The scissor lift described herein utilizes multiple scissor layers having vertically offset pins. The pins are placed such that the net vertical offset of the pins is zero. By way of example, if two of the pins were each offset downward two inches, another pin would be offset upward four inches. This arrangement prevents the longitudinal movement of the platform while still permitting the pins to be offset, increasing the strength of the scissor arms.

According to the exemplary embodiment shown in <FIG> and <FIG>, a lift device (e.g., a scissor lift, an aerial work platform, etc.), shown as lift device <NUM>, includes a chassis or base, shown as frame assembly <NUM>. A lift device (e.g., a scissor assembly, etc.), shown as lift assembly <NUM>, couples the frame assembly <NUM> to a work platform, shown as platform <NUM>. The frame assembly <NUM> supports the lift assembly <NUM> and the platform <NUM>, both of which are disposed directly above the frame assembly <NUM>. In use, the lift assembly <NUM> extends and retracts to raise and lower the platform <NUM> relative to the frame assembly <NUM> between a fully lowered position and a fully raised position. The lift device <NUM> includes an access assembly, shown as an access assembly <NUM>, that is coupled to the frame assembly <NUM> and configured to facilitate access to the platform <NUM> from the ground by an operator when the platform <NUM> is in the fully lowered position.

Referring again to <FIG> and <FIG>, the frame assembly <NUM> defines a horizontal plane having a lateral axis <NUM> and a longitudinal axis <NUM>. In some embodiments, the frame assembly <NUM> is rectangular, defining sides extending parallel to the lateral axis <NUM> and sides extending parallel to the longitudinal axis <NUM>. In some embodiments, the frame assembly <NUM> is longer in a longitudinal direction than in a lateral direction. In some embodiments, the lift device <NUM> is configured to be stationary or semi-permanent (e.g., a system that is installed in one location at a work site for the duration of a construction project). In such embodiments, the frame assembly <NUM> may be configured to rest directly on the ground and/or the lift device <NUM> may not provide powered movement across the ground. In other embodiments, the lift device <NUM> is configured to be moved frequently (e.g., to work on different tasks, to continue the same task in multiple locations, to travel across a job site, etc.). Such embodiments may include systems that provide powered movement across the ground.

The lift device <NUM> is supported by a plurality of tractive assemblies <NUM>, each including a tractive element (e.g., a tire, a track, etc.), that are rotatably coupled to the frame assembly <NUM>. The tractive assemblies <NUM> may be powered or unpowered. As shown in <FIG>, the tractive assemblies <NUM> are configured to provide powered motion in the direction of the longitudinal axis <NUM>. One or more of the tractive assemblies <NUM> may be turnable or steerable to steer the lift device <NUM>. In some embodiments, the lift device <NUM> includes a powertrain system <NUM>. In some embodiments, the powertrain system <NUM> includes a primary driver <NUM> (e.g., an engine, an electric motor, etc.). A transmission may receive mechanical energy from the primary driver and provide an output to one or more of the tractive assemblies <NUM>. In some embodiments, the powertrain system <NUM> includes a pump <NUM> configured to receive mechanical energy from the primary driver <NUM> and output a pressurized flow of hydraulic fluid. The pump <NUM> may supply mechanical energy (e.g., through a pressurized flow of hydraulic fluid) to individual motive drivers (e.g., hydraulic motors) configured to facilitate independently driving each of the tractive assemblies <NUM>. In other embodiments, the powertrain system <NUM> includes an energy storage device (e.g., a battery, capacitors, ultra-capacitors, etc.) and/or is electrically coupled to an outside source of electrical energy (e.g., a power outlet connected to a power grid). In some such embodiments, one or more of the tractive assemblies <NUM> include an individual motive driver (e.g., a motor that is electrically coupled to the energy storage device, a hydraulic motor fluidly coupled to the pump <NUM> etc.) configured to facilitate independently driving one or more of the tractive assemblies <NUM>. The outside source of electrical energy may charge the energy storage device or power the motive drivers directly. The powertrain system <NUM> may additionally or alternatively provide mechanical energy (e.g., using the pump <NUM>, by supplying electrical energy, etc.) to one or more actuators of the lift device <NUM> (e.g., a leveling actuator, the lift actuator <NUM>, etc.). One or more components of the powertrain system <NUM> may be housed in an enclosure, shown as housing <NUM>. The housing <NUM> is coupled to the frame assembly <NUM> and extends from a side of the lift device <NUM> (e.g., a left or right side). The housing <NUM> may include one or more doors to facilitate access to components of the powertrain system <NUM>.

Referring to <FIG>, the platform <NUM> includes a support surface, shown as deck <NUM>, defining a top surface configured to support operators and/or equipment and a bottom surface opposite the top surface. The bottom surface and/or the top surface extend in a substantially horizontal plane. A thickness of the deck <NUM> is defined between the top surface and the bottom surface. The bottom surface is coupled to a top end of the lift assembly <NUM>. In some embodiments, the deck <NUM> is rectangular. In some embodiments, the deck <NUM> has a footprint that is substantially similar to that of the frame assembly <NUM>.

A series of guards or railings, shown as guard rails <NUM>, extend upwards from the deck <NUM>. The guard rails <NUM> extend around an outer perimeter of the deck <NUM>, partially or fully enclosing a supported area on the top surface of the deck <NUM> that is configured to support operators and/or equipment. The guard rails <NUM> provide a stable support for the operators to hold and facilitate containing the operators and equipment within the supported area. The guard rails <NUM> define one or more openings <NUM> through which the operators can access the deck <NUM>. The opening <NUM> may be a space between two guard rails <NUM> along the perimeter of the deck <NUM>, such that the guard rails <NUM> do not extend over the opening <NUM>. Alternatively, the opening <NUM> may be defined in a guard rail <NUM> such that the guard rail <NUM> extends across the top of the opening <NUM>. In some embodiments, the platform <NUM> includes a door that selectively extends across the opening <NUM> to prevent movement through the opening <NUM>. The door may rotate (e.g., about a vertical axis, about a horizontal axis, etc.) or translate between a closed position and an open position. In the closed position, the door prevents movement through the opening <NUM>. In the open position, the door does not prevent movement through the opening <NUM>.

The access assembly <NUM> is coupled to a side of the frame assembly <NUM>. As shown in <FIG>, the access assembly <NUM> is a ladder assembly. The access assembly <NUM> is aligned with the opening <NUM> such that, when the platform <NUM> is in the lowered position, the access assembly <NUM> facilitates access to the upper surface of the deck <NUM> through the opening <NUM>.

The lift assembly <NUM> is configured to extend and retract, raising and lowering the platform <NUM> relative to the frame assembly <NUM>. The lift assembly <NUM> is selectively repositionable between a fully retracted position and a fully extended position. The fully retracted position corresponds to a fully lowered position of the platform <NUM>. The fully lowered position may be used by an operator when entering or exiting the platform <NUM> (e.g., using the access assembly <NUM>) or when transporting the lift device <NUM>. The fully extended position corresponds to a fully raised position of the platform <NUM>. The fully raised position and any positions between the fully raised position and the fully lowered position may be used by the operator when accessing an elevated area (e.g., to perform construction work, to visually inspect an elevated object, etc.).

Referring to <FIG>, the lift assembly <NUM> includes a series of subassemblies, shown as scissor layers. Specifically, the lift assembly <NUM> includes a first scissor section, shown as bottom scissor layer <NUM>, a pair of second scissor sections, shown as middle scissor layers <NUM> and <NUM>, and a third scissor section, shown as top scissor layer <NUM>. In other embodiments, the lift assembly <NUM> includes more or fewer middle scissor layers (e.g., zero, three, etc.). The bottom scissor layer <NUM> is directly coupled to the frame assembly <NUM> and to the middle scissor layer <NUM>. The middle scissor layer <NUM> is directly coupled to the bottom scissor layer <NUM> and the middle scissor layer <NUM>. The middle scissor layer <NUM> is directly coupled to the middle scissor layer <NUM> and the top scissor layer <NUM>. The top scissor layer <NUM> is directly coupled to the platform <NUM> and to the middle scissor layer <NUM>.

Each of the scissor layers includes a pair of first scissor arms or scissor members (e.g., tubular members, solid members, etc.), shown as inner arms, and a pair of second scissor arms or scissor members (e.g., tubular members, solid members, etc.), shown as outer arms. Each inner arm is coupled (e.g., fixedly) to the other inner arm within that scissor layer. Each outer arm is coupled (e.g., fixedly) to the other outer arm within that scissor layer. The inner arms of each scissor layer are pivotally coupled (e.g., by one or more pins or rods) to the corresponding outer arms of that scissor layer near the centers of both the inner arms and the outer arms. Accordingly, the inner arms of each layer pivot relative to the outer arms of that scissor layer about a lateral axis. Specifically, the bottom scissor layer <NUM> includes inner arms <NUM> and outer arms <NUM> that pivot relative to one another about a lateral axis, shown as middle axis <NUM>. The middle scissor layer <NUM> includes inner arms <NUM> and outer arms <NUM> that pivot relative to one another about a lateral axis, shown as middle axis <NUM>. The middle scissor layer <NUM> includes inner arms <NUM> and outer arms <NUM> that pivot relative to one another about a lateral axis, shown as middle axis <NUM>. The top scissor layer <NUM> includes inner arms <NUM> and outer arms <NUM> that pivot relative to one another about a lateral axis, shown as middle axis <NUM>.

The scissor layers are stacked atop one another to form the lift assembly <NUM>. Each pair of inner arms and each pair of outer arms has a top end and a bottom end. The ends of the inner arms and the outer arms are pivotally coupled (e.g., by one or more pins or rods) to the adjacent ends of the inner or outer arms of the adjacent scissor layers. Each set of inner arms is directly pivotally coupled to one or more sets of outer arms. This facilitates spacing each pair of inner arms a first distance apart from one another and spacing each pair of outer arms a second distance apart from one another, where the second distance is greater than the first distance. This facilitates ensuring that the fully lowered position is as low as possible, increasing the accessibility of the platform <NUM> and making the lift device <NUM> more compact.

The upper ends of the outer arms <NUM> are pivotally coupled to the lower ends of the inner arms <NUM> such that they rotate relative to one another about a lateral axis, shown as end axis <NUM>. The upper ends of the inner arms <NUM> are pivotally coupled to the lower ends of the outer arms <NUM> such that they rotate relative to one another about another end axis <NUM>. The upper ends of the outer arms <NUM> are pivotally coupled to the lower ends of the inner arms <NUM> such that they rotate relative to one another about a lateral axis, shown as end axis <NUM>. The upper ends of the inner arms <NUM> are pivotally coupled to the lower ends of the outer arms <NUM> such that they rotate relative to one another about another end axis <NUM>. The upper ends of the outer arms <NUM> are pivotally coupled to the lower ends of the inner arms <NUM> such that they rotate relative to one another about a lateral axis, shown as end axis <NUM>. The upper ends of the inner arms <NUM> are pivotally coupled to the lower ends of the outer arms <NUM> such that they rotate relative to one another about another end axis <NUM>.

Referring to <FIG> , the lower ends of the inner arms <NUM> are pivotally coupled to the frame assembly <NUM> such that the inner arms <NUM> rotate relative to the frame assembly <NUM> about a lateral axis, shown as end axis <NUM>. The end axis <NUM> is fixed to the frame assembly <NUM> such that the lower ends of the inner arms <NUM> are translationally fixed relative to the frame assembly <NUM>. A pair of bosses, shown as bearing blocks <NUM>, are coupled (e.g., welded, fastened, etc.) to the frame assembly <NUM>. The bearing blocks <NUM> are each configured to receive a rod or pin, shown as pin <NUM>. The bearing blocks <NUM> and the pins <NUM> may be configured to facilitate rotation of the pins <NUM> about the end axis <NUM>. The pins <NUM> each extend along the end axis <NUM> through one of the bearing blocks <NUM> and the corresponding inner arms <NUM>. The pins <NUM> and the bearing blocks <NUM> pivotally couple the inner arms <NUM> to the frame assembly <NUM>.

Referring to <FIG>, the lower ends of the outer arms <NUM> are pivotally and slidably coupled to the frame assembly <NUM> such that the outer arms <NUM> rotate relative to the frame assembly <NUM> about a lateral axis, shown as end axis <NUM>. The end axis <NUM> is translatable longitudinally relative to the frame assembly <NUM> such that the lower ends of the outer arms <NUM> are slidable longitudinally relative to the frame assembly <NUM>. A tubular member, shown as rod <NUM>, extends laterally between both of the outer arms <NUM>. The rod <NUM> is coupled (e.g., welded, fastened, etc.) to the outer arms <NUM>. The rod <NUM> further extends laterally outside of the outer arms <NUM>. Each end of the rod <NUM> is received within an aperture defined by a block, shown as sliding block <NUM>. The sliding blocks <NUM> are accordingly pivotally coupled to the rod <NUM>. A pair of frame members, shown as channels <NUM> are coupled to (e.g., fastened to, welded to, integrally formed with, etc.) the frame assembly <NUM>. The channels <NUM> extend longitudinally along the frame assembly <NUM>. The channels <NUM> each define a recess <NUM> that receives the sliding block <NUM>. Each of the recesses <NUM> face toward a longitudinal centerline of the lift device <NUM> such that the sliding blocks <NUM> are captured laterally by the channels <NUM>. The sliding blocks <NUM> are free to translate longitudinally along the channels <NUM> to permit pivoting of the outer arms <NUM> relative to the inner arms <NUM>.

Referring to <FIG>, the upper ends of the outer arms <NUM> are pivotally coupled to the deck <NUM> of the platform <NUM> such that the outer arms <NUM> rotate relative to the deck <NUM> about a lateral axis, shown as end axis <NUM>. The end axis <NUM> is fixed to the platform <NUM> such that the upper ends of the outer arms <NUM> are translationally fixed relative to the platform <NUM>. In one embodiment, a pair of pins couple the outer arms <NUM> to the platform <NUM>. The pins may each extend along the end axis <NUM> through one of the outer arms <NUM> and a portion of the deck <NUM>.

Referring to <FIG>, the upper ends of the inner arms <NUM> are pivotally and slidably coupled to the deck <NUM> of the platform <NUM> such that the inner arms <NUM> rotate relative to the deck <NUM> about a lateral axis, shown as end axis <NUM>. The end axis <NUM> is translatable longitudinally relative to the platform <NUM> such that the upper ends of the inner arms <NUM> are slidable longitudinally relative to the platform <NUM>. A tubular member, shown as rod <NUM>, extends laterally between both of the inner arms <NUM>. The rod <NUM> is coupled (e.g., welded, fastened, etc.) to the inner arms <NUM>. The rod <NUM> further extends laterally outside of the inner arms <NUM>. Each end of the rod <NUM> is received within an aperture defined by a block, shown as sliding block <NUM>. The sliding blocks <NUM> are accordingly pivotally coupled to the rod <NUM>. A pair of frame members, shown as channels <NUM> are coupled (e.g., fastened, welded, integrally formed with, etc.) to the frame assembly <NUM>. The channels <NUM> extend longitudinally along the platform <NUM>. The channels <NUM> each define a recess <NUM> that receives the sliding block <NUM>. Each of the recesses <NUM> face toward a longitudinal centerline of the lift device <NUM> such that the sliding blocks <NUM> are captured laterally by the channels <NUM>. The sliding blocks <NUM> are free to translate longitudinally along the channels <NUM> to permit pivoting of the inner arms <NUM> relative to the outer arms <NUM>.

An actuator (e.g., a hydraulic cylinder, a pneumatic cylinder, a motor-driven leadscrew, etc.), shown as lift actuator <NUM>, is configured to extend and retract the lift assembly <NUM>. As shown in <FIG>, the lift assembly <NUM> includes one lift actuator <NUM>, and the lift actuator <NUM> is a hydraulic cylinder fluidly coupled to the pump <NUM>. The lift actuator <NUM> is pivotally coupled to the inner arms <NUM> at one end (e.g., a cap end) and pivotally coupled to the inner arms <NUM> at the opposite end (e.g., a rod end). In other embodiments, the lift assembly <NUM> includes more or fewer lift actuators <NUM> and/or the lift actuator <NUM> is otherwise arranged. The lift actuator <NUM> is configured to selectively reposition the lift assembly <NUM> between the fully extended and fully retracted positions. In some embodiments, extension of the lift actuator <NUM> moves the platform <NUM> vertically upward (extending the lift assembly <NUM>), and retraction of the lift actuator <NUM> moves the platform <NUM> vertically downward (retracting the lift assembly <NUM>). In other embodiments, extension of the lift actuator <NUM> retracts the lift assembly <NUM>, and retraction of the lift actuator <NUM> extends the lift assembly <NUM>. The lift device <NUM> may include various components configured to drive the lift actuator <NUM> (e.g., pumps, valves, compressors, motors, batteries, voltage regulators, etc.).

Referring to <FIG>, the scissor arms are coupled to one another by a series of pins. Each of the pins extends through a laterally extending aperture. The laterally extending apertures are centered about and extend parallel to the end and middle axes described herein (e.g., the end axes <NUM>, the middle axis <NUM>, etc.). As shown in <FIG>, a bearing member, shown as middle bushing <NUM>, extends through and is coupled to the outer arm <NUM>. The middle bushing <NUM> defines an aperture, shown as middle pin aperture <NUM>. The inner arm <NUM> utilizes a similar middle bushing <NUM>. The middle pin aperture <NUM> receives a rod or pin, shown as middle pin <NUM>. The middle pin <NUM> also extends through the middle pin aperture <NUM> corresponding to the inner arm <NUM>, pivotally coupling the inner arm <NUM> and the outer arm <NUM>. One or more retraining members (e.g., retaining rings, machined shoulders, clamping collars, fasteners, etc.), shown as snap rings <NUM>, limit the lateral movement of the middle pin <NUM> relative to the inner arm <NUM> and the outer arm <NUM>. The middle bushing <NUM>, the middle pin aperture <NUM>, and the middle pin <NUM> are centered about and extend parallel to (e.g., are aligned with) the middle axis <NUM>. The outer arm <NUM> has a height Hi defined between a top surface <NUM> and a bottom surface <NUM> of the outer arm <NUM>. The middle axis <NUM> is offset a distance D<NUM> below the top surface <NUM> of the outer arm <NUM>. The distance D<NUM> is approximately half of the height Hi such that the middle axis <NUM> is substantially vertically centered on the outer arm <NUM>. The middle axis <NUM> is similarly centered on the inner arm <NUM>. The other outer arm <NUM> and inner arm <NUM> may utilize a similar bushing and pin arrangement. The scissor arms of each middle scissor layer (e.g., the middle scissor layer <NUM>, the middle scissor layer <NUM>) utilize middle bushings <NUM> and middle pins <NUM> positioned in this way to pivotally couple the outer and inner arms.

As shown in <FIG>, a bearing member (e.g., a roller bearing, a ball bearing, a bushing, etc.), shown as upper bushing <NUM>, extends through and is coupled to an upper end portion of the outer arm <NUM>. The upper bushing <NUM> defines an aperture, shown as upper pin aperture <NUM>. The upper end portion of the inner arm <NUM> includes a similar upper bushing <NUM>. A bearing member, shown as lower bushing <NUM>, extends through and is coupled to a lower end portion of the outer arm <NUM>. The lower bushing <NUM> defines an aperture, shown as lower pin aperture <NUM>. The lower end portion of the inner arm <NUM> includes a similar lower bushing <NUM>. The upper pin aperture <NUM> and the lower pin aperture <NUM> are each configured to receive a rod or pin, shown as end pin <NUM>. An end pin <NUM> extends through both the upper bushing <NUM> of the outer arm <NUM> and the lower bushing <NUM> of the inner arm <NUM>, pivotally coupling the outer arm <NUM> and the inner arm <NUM>. Another end pin <NUM> extends through both the lower bushing <NUM> of the outer arm <NUM> and the upper bushing <NUM> of the inner arm <NUM>, pivotally coupling the outer arm <NUM> and the inner arm <NUM>. Additional snap rings <NUM> limit the lateral movement of the end pins <NUM> relative to the outer arm <NUM>, the inner arm <NUM>, and the inner arm <NUM>.

The upper bushing <NUM>, the upper pin aperture <NUM>, and the corresponding end pin <NUM> are centered about and extend parallel to (e.g., are aligned with) the end axis <NUM>. The lower bushing <NUM>, the lower pin aperture <NUM>, and the corresponding end pin <NUM> are centered about and extend parallel to (e.g., are aligned with) the end axis <NUM>. The end axis <NUM> is offset a distance D<NUM> below the top surface <NUM> of the outer arm <NUM>. The distance D<NUM> is less than the distance D<NUM> such that the end axis <NUM> is positioned above the center of the outer arm <NUM>. The end axis <NUM> is offset a distance D<NUM> below the top surface <NUM> of the outer arm <NUM>. The distance D<NUM> is greater than the distance D<NUM> such that the end axis <NUM> is positioned below the center of the outer arm <NUM>. In some embodiments, the end axis <NUM> and the end axis <NUM> are approximately equidistant from the middle axis <NUM> (e.g., D<NUM>-D<NUM> = D<NUM>-D<NUM>). In some embodiments, the middle bushing <NUM>, the middle pin aperture <NUM>, the middle <NUM>, the upper bushing <NUM>, the upper pin aperture <NUM>, the lower bushing <NUM>, the lower pin aperture <NUM>, and/or the end pins <NUM> are positioned entirely between the top surface <NUM> and the bottom surface <NUM> of the outer arm <NUM>. The upper and lower ends of each of the inner arms <NUM>, the outer arms <NUM>, the inner arms <NUM>, and the outer arms <NUM> each utilize this pivotal coupling arrangement. The lower ends of the inner arms <NUM> and the outer arms <NUM> utilize this pivotal coupling arrangement. The upper ends of the inner arms <NUM> and the outer arms <NUM> utilize this pivotal coupling arrangement. Offsetting the end pins <NUM> of the upper ends upward and offsetting the end pins <NUM> of the lower ends downward facilitates positioning the scissor arms closer to a horizontal orientation when in the fully retracted position, reducing the height of the lift assembly <NUM> in the fully retracted position.

Referring to <FIG>, a pair of supports, shown as side plates <NUM> are each coupled (e.g., welded, fastened, etc.) to opposite sides of the outer arm <NUM>. The side plates <NUM> extend below the outer arm <NUM>. A bearing member, shown as bottom middle bushing <NUM>, extends through and is coupled to the side plates <NUM>. The bottom middle bushing <NUM> defines an aperture, shown as bottom middle pin aperture <NUM>. The inner arm <NUM> utilizes a similar set of side plates <NUM> and a similar bottom middle bushing <NUM>. The bottom middle pin aperture <NUM> receives a rod or pin, shown as bottom middle pin <NUM>. The bottom middle pin <NUM> also extends through the bottom middle pin aperture <NUM> of the corresponding bottom middle bushing <NUM> of the inner arm <NUM>, pivotally coupling the inner arm <NUM> and the outer arm <NUM>. One or more retraining members (e.g., retaining rings, machined shoulders, clamping collars, fasteners, etc.), may be coupled to the bottom middle pin <NUM> to limit the lateral movement of the bottom middle pin <NUM> relative to the inner arm <NUM> and the outer arm <NUM>. The bottom middle bushing <NUM>, the bottom middle pin aperture <NUM>, and the bottom middle pin <NUM> are centered about and extend parallel to (e.g., are aligned with) the middle axis <NUM>. The outer arm <NUM> has a height H<NUM> defined between a top surface <NUM> and a bottom surface <NUM> of the outer arm <NUM>. The middle axis <NUM> is offset a distance D<NUM> below the top surface <NUM> of the outer arm <NUM>. The distance D<NUM> is greater than the height Hi such that the middle axis <NUM> is vertically below the bottom surface <NUM>. The bottom middle bushing <NUM>, the bottom middle pin aperture <NUM>, and/or the bottom middle pin <NUM> are positioned entirely below the bottom surface <NUM>. Accordingly, the bottom middle bushing <NUM>, the bottom middle pin aperture <NUM>, and/or the bottom middle pin <NUM> do not extend through the outer arm <NUM>. This pivotal coupling arrangement may increase the strength of the outer arm <NUM> (e.g., relative to the outer arm <NUM>), because no holes are required through the outer arm <NUM>. The bottom middle bushing <NUM> is similarly positioned on the inner arm <NUM>. The other outer arm <NUM> and inner arm <NUM> may utilize a similar bushing and pin arrangement.

Referring to <FIG>, a pair of supports, shown as side plates <NUM> are each coupled (e.g., welded, fastened, etc.) to opposite sides of the outer arm <NUM>. The side plates <NUM> extend above the outer arm <NUM>. A bearing member, shown as top middle bushing <NUM>, extends through and is coupled to the side plates <NUM>. The top middle bushing <NUM> defines an aperture, shown as top middle pin aperture <NUM>. The inner arm <NUM> includes similar set of side plates <NUM> and a similar top middle bushing <NUM>. The top middle pin aperture <NUM> receives a rod or pin, shown as top middle pin <NUM>. The top middle pin <NUM> also extends through the top middle pin aperture <NUM> of the corresponding top middle bushing <NUM> of the inner arm <NUM>, pivotally coupling the inner arm <NUM> and the outer arm <NUM>. One or more retraining members (e.g., retaining rings, machined shoulders, clamping collars, fasteners, etc.), may be coupled to the top middle pin <NUM> to limit the lateral movement of the top middle pin <NUM> relative to the inner arm <NUM> and the outer arm <NUM>. The top middle bushing <NUM>, the top middle pin aperture <NUM>, and the top middle pin <NUM> are centered about and extend parallel to (e.g., are aligned with) the middle axis <NUM>. The outer arm <NUM> has a height H<NUM> defined between a top surface <NUM> and a bottom surface <NUM> of the outer arm <NUM>. The middle axis <NUM> is offset a distance D<NUM> above the top surface <NUM> of the outer arm <NUM>. The top middle bushing <NUM>, the top middle pin aperture <NUM>, and/or the top middle pin <NUM> are positioned entirely above the top surface <NUM>. Accordingly, the top middle bushing <NUM>, the top middle pin aperture <NUM>, and/or the top middle pin <NUM> do not extend through the outer arm <NUM>. This pivotal coupling arrangement may increase the strength of the outer arm <NUM> (e.g., relative to the outer arm <NUM>), because no holes are required through the outer arm <NUM>. The top middle bushing <NUM> is similarly positioned on the inner arm <NUM>. The other outer arm <NUM> and inner arm <NUM> may utilize a similar bushing and pin arrangement.

A point, referred to herein as an end axis center point, is defined for each of the scissor layers. The end axis center point is a point centered between each of the end axes corresponding to that scissor layer. The end axis center point of a scissor layer is defined by (a) within a plane perpendicular to the lateral axis <NUM>, defining (e.g., drawing) a first straight line between the end axes of the inner arms of that scissor layer and (b) within the plane, defining a second straight line between the end axes of the outer arms of that scissor layer. The point at which these two lines intersect is the end axis center point. By way of example, the end axis center point for the middle scissor layer <NUM> is shown in <FIG>. To locate the end axis center point, a first straight line is drawn between the end axis <NUM> and the end axis <NUM> of the inner arms <NUM>. A second straight line is drawn between the end axis <NUM> and the end axis <NUM> of the outer arms <NUM>. The end axis center point for the middle scissor layer <NUM>, shown as point C<NUM>, is the point where these two lines intersect. Using a similar process, the end axis center points of the bottom scissor layer <NUM>, the middle scissor layer <NUM>, and the top scissor layer <NUM> can be located. The end axis center points of the bottom scissor layer <NUM>, the middle scissor layer <NUM>, and the top scissor layer <NUM> are shown in <FIG> as point C<NUM>, point C<NUM>, and point C<NUM>, respectively.

<FIG> illustrates the middle scissor layer <NUM> in a partially extended position, and <FIG> illustrates the middle scissor layer <NUM> in the fully retracted position. The end axis center point C<NUM> is positioned along the middle axis <NUM> such that there is no offset between the end axis center point C<NUM> and the middle axis <NUM> (i.e., OffsetMP<NUM> = <NUM>). A longitudinal distance Li is shown between the end axes <NUM>, and a longitudinal distance L<NUM> is shown between the end axes <NUM>. Due to the relative positioning of the end axis center point C<NUM> and the middle axis <NUM>, as the lift assembly <NUM> moves from the fully retracted position to the fully extended position, the distance L<NUM> and the distance L<NUM> decrease at an equal rate. Accordingly, the distance L<NUM> and the distance L<NUM> are equal in all positions of the middle scissor layer <NUM>. Similarly, within the middle scissor layer <NUM>, the end axis center point C<NUM> is positioned along the middle axis <NUM> (i.e., OffsetMP<NUM> = <NUM>).

<FIG> illustrates the bottom scissor layer <NUM> in a partially extended position, and <FIG> illustrates the bottom scissor layer <NUM> in the fully retracted position. The end axis center point C<NUM> is offset a distance OffsetMP<NUM> vertically above the middle axis <NUM> (i.e., OffsetMP<NUM> > <NUM>). A longitudinal distance Li is shown between the end axis <NUM> and the end axis <NUM>, and a longitudinal distance L<NUM> is shown between the end axes <NUM>. As the lift assembly <NUM> moves from the fully retracted position toward the fully extended position, the distance Li and the distance L<NUM> decrease. Due to the relative positioning of the end axis center point C<NUM> and the middle axis <NUM>, the distance L<NUM> decreases more rapidly than the distance Li. Accordingly, while the distance Li and the distance L<NUM> may be equal in the fully retracted position, the distance Li is greater than the distance L<NUM> in the partially extended position.

<FIG> illustrates the top scissor layer <NUM> in a partially extended position, and <FIG> illustrates the top scissor layer <NUM> in the fully retracted position. The end axis center point C<NUM> is offset a distance OffsetMP<NUM> vertically below the middle axis <NUM> (i.e., OffsetMP<NUM> < <NUM>). A longitudinal distance Li is shown between the end axes <NUM>, and a longitudinal distance L<NUM> is shown between the end axis <NUM> and the end axis <NUM>. As the lift assembly <NUM> moves from the fully retracted position toward the fully extended position, the distance L<NUM> and the distance L<NUM> decrease. Due to the relative positioning of the end axis center point C<NUM> and the middle axis <NUM>, the distance L<NUM> decreases more rapidly than the distance L<NUM>. Accordingly, while the distance L<NUM> and the distance L<NUM> may be equal in the fully retracted position, the distance L<NUM> is less than the distance L<NUM> in the partially extended position.

Referring to <FIG>, the distances between the end axes of each inner arm and each outer arm are substantially equal. By way of example, (a) the distance between the end axis <NUM> and the end axis <NUM> of the outer arm <NUM>, (b) the distance between the end axis <NUM> and the end axis <NUM> of the outer arm <NUM>, and (c) the distance between the end axis <NUM> and the end axis <NUM> of the inner arm <NUM> are all substantially equal. Because these distances are all equal, the magnitude of each middle pin offset distance (i.e., |OffsetMP|) determines the angle between the corresponding inner arms and outer arms of that scissor layer. As shown in <FIG>, <FIG>, <FIG>, and <FIG>, an angle θ is defined between the straight lines used to define the end axis center point. Specifically, the bottom scissor layer <NUM> has an angle θ<NUM>, the middle scissor layer <NUM> has an angle θ<NUM>, the middle scissor layer <NUM> has an angle θ<NUM>, and the top scissor layer <NUM> has an angle θ<NUM>. In the embodiment shown in <FIG>, the middle pin offset distances of the middle scissor layer <NUM> and the middle scissor layer <NUM> are both zero (i.e., OffsetMP<NUM> = OffsetMP<NUM> = <NUM>). Accordingly, the angles of the middle scissor layer <NUM> and the middle scissor layer <NUM> are equal (i.e., θ<NUM> = θ<NUM>). The middle pin offset distances of the bottom scissor layer <NUM> and the top scissor layer <NUM> have equal magnitudes (i.e., |OffsetMP<NUM>| = |OffsetMP<NUM>|). Accordingly, the angles of the bottom scissor layer <NUM> and the top scissor layer <NUM> are equal (i.e., θ<NUM> = θ<NUM>).

The lift assembly <NUM> is shown in the fully retracted position in <FIG>. In this embodiment, the end axes are vertically aligned with one another in the fully retracted position. Specifically, a first vertical line can be drawn through the middle axis <NUM>, the middle axis <NUM>, the middle axis <NUM>, the middle axis <NUM>, and the each of the end axis center points. In this embodiment, the end axes are vertically aligned with one another in the fully retracted position. Specifically, a second vertical line can be drawn through the end axis <NUM>, the end axis <NUM>, the end axis <NUM>, the end axis <NUM>, and the end axis <NUM> on one side of the lift assembly <NUM>, and a third vertical line can be drawn through the end axis <NUM>, the end axis <NUM>, the end axis <NUM>, the end axis <NUM>, and the end axis <NUM> on the other side of the lift assembly <NUM>.

Referring to <FIG>, the lift assembly <NUM> is shown in the fully extended position. In this embodiment, the middle axes are all vertically aligned with one another. However, the end axes are not all vertically aligned with one another. The end axis <NUM> and the end axis <NUM> are aligned with one another. The end axis <NUM>, the end axis <NUM>, and the end axis <NUM> are also vertically aligned with one another. However, the end axis <NUM>, the end axis <NUM>, and the end axis <NUM> are offset longitudinally inward from the end axis <NUM> and the end axis <NUM>. This variation in vertical alignment is due to the variation in middle pin offset distances (i.e., OffsetMP) between each scissor layer. In the bottom scissor layer <NUM>, the end axis center point C<NUM> is offset above the middle axis <NUM> (i.e., OffsetMP<NUM> > <NUM>), so the end axis <NUM> is offset longitudinally inward from the end axis <NUM>. In the middle scissor layer <NUM> and the middle scissor layer <NUM>, the end axis center point C<NUM> and the end axis center point C<NUM> are vertically aligned with the middle axis <NUM> and the middle axis <NUM>, respectively (i.e., OffsetMP<NUM> = OffsetMP<NUM> = <NUM>). Accordingly, the end axis <NUM>, the end axis <NUM>, and the end axis <NUM> are all in the same longitudinal position. In the top scissor layer <NUM>, the end axis center point C<NUM> is offset below the middle axis <NUM> (i.e., OffsetMP<NUM> < <NUM>), so the end axis <NUM> is offset longitudinally inward from the end axis <NUM>. As shown in <FIG>, the middle pin offset distances of the top scissor layer <NUM> and the bottom scissor layer <NUM> have equal magnitudes (i.e., |OffsetMP<NUM>| = |OffsetMP<NUM>|). Specifically, the middle pin offset distances of the top scissor layer <NUM> and the bottom scissor layer <NUM> have equal magnitudes but are offset in opposite directions (i.e., OffsetMP<NUM> + OffsetMP<NUM> = <NUM>). Accordingly, the longitudinal offsets caused by the top scissor layer <NUM> and the bottom scissor layer <NUM> cancel one another out, keeping the end axis <NUM> and the end axis <NUM> vertically aligned.

When using a scissor lift, a purely vertical movement of the platform is desired by the user. This type of movement is typically what a user expects when using a scissor lift, and the user will typically set the scissor lift up in a location according to this assumption. Accordingly, any longitudinal movement of the platform may be considered undesirable by the user. By way of example, the user may place the scissor lift up against a wall of a structure. If the platform were to move longitudinally toward the wall, the platform could contact the wall, causing damage to the wall and/or the lift device.

The lift assembly <NUM> is configured to eliminate any longitudinal movement of the platform <NUM>. The frame assembly <NUM> is longitudinally fixed to the end axis <NUM>, and the platform <NUM> is longitudinally fixed to the end axis <NUM>. Accordingly, if the end axis <NUM> were to move longitudinally relative to the end axis <NUM>, the platform <NUM> would also move longitudinally the same distance. However, because the middle pin offset distances of the top scissor layer <NUM> and the bottom scissor layer <NUM> are equal, the platform <NUM> moves purely vertically. This arrangement permits the increased strength from offsetting the middle pins without introducing longitudinal movement to the platform <NUM>.

In other embodiments, the middle pin offset distances of the top scissor layer <NUM> and the bottom scissor layer <NUM> are not equal and opposite. Additionally or alternatively, one or more of the middle scissor layers may include offset middle pins. The lift assembly <NUM> may additionally or alternatively include more or fewer middle sections. In such embodiments, the middle pins of each scissor layer are arranged such that the sum of all of the middle pin offset distances is equal to zero. This may be relationship may be represented by the following expression: <MAT> where n is equal to the total number of scissor layers within the lift assembly <NUM> (e.g., n = (the number of middle scissor layers) + <NUM>). In this arrangement, if the distances between the end axes of all of the inner arms and the outer arms are substantially equal, any offset in longitudinal position of the platform <NUM> caused by offsetting the middle pin of one of the scissor layers is nullified by the offsets introduced by one or more other layers.

In some embodiments, the middle pin offset distances of the top scissor layer <NUM> and the bottom scissor layer <NUM> are equal to zero, and middle pin offset distances of the middle scissor layer <NUM> and the middle scissor layer <NUM> have equal magnitudes but are offset in opposite directions (i.e., OffsetMP<NUM> = -OffsetMP<NUM>; OffsetMP<NUM> = OffsetMP<NUM> = <NUM>). In other embodiments, the middle pin offset distances of each of the scissor layers are not equal to zero (e.g., OffsetMP<NUM> = -<NUM> in; OffsetMP<NUM> = <NUM> in; OffsetMP<NUM> = <NUM> in; OffsetMP<NUM> = -<NUM> in). In yet other embodiments, the middle pin offset distances are otherwise configured such that the sum of the middle pin offset distances is equal to zero (e.g., OffsetMP<NUM> = -<NUM> in; OffsetMP<NUM> = <NUM> in; OffsetMP<NUM> = <NUM> in; OffsetMP<NUM> = -<NUM> in; OffsetMPs = <NUM> in; OffsetMP<NUM> = <NUM> in).

In other embodiments, different parts of the lift assembly <NUM> are translationally fixed relative to the frame assembly <NUM> and/or the platform <NUM>. By way of example, the end axis <NUM> may be free to translate relative to the frame assembly <NUM>, and the end axis <NUM> may be fixed relative to the frame assembly <NUM>. By way of another example, the end axis <NUM> may be free to translate relative to the platform <NUM>, and the end axis <NUM> may be fixed relative to the platform <NUM>. In such embodiments, the platform <NUM> will not move longitudinally if the lift assembly <NUM> satisfies Equation <NUM>.

As utilized herein, the terms "approximately," "about," "substantially," and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the precise numerical ranges provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and claimed are considered to be within the scope of the invention as recited in the appended claims.

It should be noted that the terms "exemplary" and "example" as used herein to describe various embodiments is intended to indicate that such embodiments are possible examples, representations, and/or illustrations of possible embodiments (and such term is not intended to connote that such embodiments are necessarily extraordinary or superlative examples).

The terms "coupled," "connected," and the like, as used herein, mean the joining of two members directly or indirectly to one another. Such joining may be stationary (e.g., permanent, etc.) or moveable (e.g., removable, releasable, etc.). Such joining may be achieved with the two members or the two members and any additional intermediate members being integrally formed as a single unitary body with one another or with the two members or the two members and any additional intermediate members being attached to one another.

References herein to the positions of elements (e.g., "top," "bottom," "above," "below," "between," etc.) are merely used to describe the orientation of various elements in the figures.

Conjunctive language such as the phrase "at least one of X, Y, and Z," unless specifically stated otherwise, is otherwise understood with the context as used in general to convey that an item, term, etc. may be either X, Y, Z, X and Y, X and Z, Y and Z, or X, Y, and Z (i.e., any combination of X, Y, and Z). Thus, such conjunctive language is not generally intended to imply that certain embodiments require at least one of X, at least one of Y, and at least one of Z to each be present, unless otherwise indicated.

Claim 1:
A lift device (<NUM>), comprising:
a base;
a platform (<NUM>) configured to support an operator; and
a scissor assembly coupling the base to the platform (<NUM>), the scissor assembly including:
a first scissor layer (<NUM>) including a first inner arm (<NUM>) pivotally coupled to a first outer arm (<NUM>), wherein the first inner arm (<NUM>) is configured to rotate relative to the first outer arm (<NUM>) about a first middle axis (<NUM>), and wherein the first scissor layer (<NUM>) has a first end axis center point;
a second scissor layer (<NUM>) coupled to the first scissor layer (<NUM>), the second scissor layer (<NUM>) including a second inner arm (<NUM>) pivotally coupled to a second outer arm (<NUM>), wherein the second inner arm (<NUM>) is configured to rotate relative to the second outer arm (<NUM>) about a second middle axis (<NUM>), wherein the second scissor layer (<NUM>) has a second end axis center point; and
an actuator configured to move the platform (<NUM>) between a fully raised position and a fully lowered position relative to the base,
wherein the first middle axis (<NUM>) is offset vertically from the first end axis center point, wherein the second middle axis (<NUM>) is offset vertically from the second end axis center point, and wherein the first middle axis (<NUM>) is offset vertically from the second middle axis (<NUM>); and
characterized in that the first inner arm (<NUM>) has an upper end defining a first end axis and a lower end defining a second end axis, and wherein a distance between the first end axis and the second end axis is fixed.