MXPA97007347A - Work platform system aerial articular - Google Patents

Abstract

The present invention relates to an articulated aerial work platform system comprising a base, a work platform and a lifting assembly on the base to raise and lower the work platform, said lifting assembly being characterized in that it comprises: lower lifter comprising a parallelogram, said lower lifter having a lower end connected to the base for pivotal movement of the lifter with respect to the base, and an upper end: an upper lifter comprising a parallelogram, said upper lifter having a lower end connected operatively to the upper end of the lower lifter for pivotal movement of the upper lifter with respect to the lower lifter, and an upper end: an extendable and retractable power actuator having a lower end connected to the base, and an upper end connected to the upper lifter, said actuator being extendable to pivot the elevators s upper and lower towards elevated and retractable positions for the upper and lower elevators towards lowered positions, the relationship between a distance of extension of the actuator and a height of the work platform being linear, a mechanism of articulation regulated of time that interconnects the elevators upper and lower to maintain the pivotal movement of the upper and lower elevators in time-regulated relation to one another as they move between their respective raised and lowered positions, said time-regulating articulation mechanism comprising a time-controlled articulation at its end superior to an upper beam of the upper elevator and connected at its lower end to a lower beam of the lower elevator

Description

ARTICULATED AERIAL WORK PLATFORM SYSTEM BACKGROUND OF THE INVENTION This invention relates generally to aerial work platforms and more particularly to an articulated aerial work platform system. Aerial platforms of the type to which the present invention relates have a base that includes a rotating platform on which a lifting structure and a working platform arranged to be lifted by means of the lifting structure is mounted. In this way, the platform can be raised and lowered, and turned over a generally vertical central line of the turntable. These movements of the platform are typically controlled by an operator from a control panel on the platform. The movement of the platform must be relatively accurate, particularly in situations where the operating space is small. In the past, the speed of movement of the platform varied significantly along different scales of movement, making movement control more difficult. In many cases, including for example when the aerial platform is used to lift people towards the wings of an airplane, the operator needs to be sure of the location of the lifting structure around the platform. The elevation structure near the platform that projects substantially below the floor of the platform can not be observed by the op > He may inadvertently hit the wing or other structure near the platform. In addition to driving to the platform itself, the operator must be aware of the location and movements of the lift structure of the platform (eg, booms and elevators) that lie beneath it. In this way, it is highly desirable to maintain the movements of the lifting structure within a defined volume in which it is free to move without hitting any adjacent structure. The defined volume is normally the upward projection of the rotating platform or base. The characteristic of the lifting structure to extend laterally out of this volume in an elevated position is known as "tail swing" or "front swing", depending on the direction in which the lifting structure moves away from the volume. Frequently, such aerial platforms are mobile and have up to that point a chassis and wheels that comprise its base. The platform is able to move from one location to another for its use. The lifting structure must not be mounted so that in its lowered or retracted position the lifting structure projects substantially out of the base, making it difficult to maneuver the aerial platform. to a new location. Supporting a platform at substantial distances away from the base requires substantial strength in the lifting structure, not only to resist bending moments but also to resist torsion. Simply adding material to the lifting structure is not a satisfactory solution to the strength requirement due to the weight added to the lifting structure.

BRIEF DESCRIPTION OF THE INVENTION Among the various objects and features of the present invention may be noted the provision of an articulated aerial platform system that is capable of maintaining a substantially constant vertical platform speed during the full scale of vertical movement of parallelogram elevators of the platform system , - the provision of an aerial platform system that maintains its center of gravity close to the centerline of its base when the platform is lifted; the provision of an aerial platform system in which there is a generally linear relationship between the extension of a lifting cylinder of the system and the vertical position of the platform; the provision of an aerial platform system that has fewer component parts; the provision of an aerial platform system that is rigid in structure; the provision of an aerial platform system that is resistant to torsion; the provision of an aerial platform system having a compact retracted position; the provision of an aerial platform system in which the structure supporting the platform is protected against the coupling of surrounding structures; and the provision of an aerial platform assembly that is economical to manufacture. Generally, an articulated aerial work platform system constructed in accordance with the principles of the present invention comprises a base, a work platform and a lifting assembly on the base for raising and lowering the work platform. The lifting assembly includes a lower elevator comprising a parallelogram. A lower end of the lower riser is connected to the base for the pivotal movement of the riser with respect to the base. An upper lifter comprising a parallelogram has a lower end connected to an upper end of the lower lifter for pivotal movement of the upper lifter with respect to the lower lifter. An extendable and retractable power actuator, having a lower end connected to the base and an upper end connected to the upper elevator, is extendable to pivot the upper and lower elevators to elevated positions, and retractable to pivot to the upper and lower elevators to descending positions. A time regulating mechanism that interconnects the upper and lower elevators maintains the pivotal movement of the upper and lower elevators in regulated relation to one another as they move between their respective raised and lowered positions. In another aspect of the present invention, a boom and boom system is provided comprising a boom having an inner end mounted for pivotal movement of the boom between raised and lowered positions, and a boom comprising a parallelogram including upper parallel ends. and lower having inner ends connected pivotally to an outer end of the boom. A platform connector member at the outer ends of said upper and lower ends is connected in a first pivot connection to an outer end of the upper end of the boom for relative pivotal movement therebetween around a generally horizontal first axis. A second pivot connection between an outer end of the lower end of the boom and the connector member allows relative pivotal movement therebetween about a second generally horizontal axis spaced apart from said first generally horizontal axis. A first retractable and extendable power actuator can pivot the boom between raised and lowered positions relative to the outer end of the boom while the boom's parallelogram holds the connector member in a substantially fixed angular orientation while the boom moves between its raised and retracted positions. descended. A work platform assembly comprising a floor to support a worker is connected to the connector member in a third pivot connection for pivotal movement of the work platform assembly in relation to the connector member around a third generally horizontal axis separated from said first and second axes generally horizontal. A second retractable and extendable power actuator has an upper end connected to the work platform assembly, and a lower end. A fourth pivot connection between the lower end of the second power actuator and the connector member allows pivotal movement of the lower end of the second power actuator relative to the connector member about a fourth generally horizontal axis spaced apart from said first, second and third generally horizontal axes. The disposition it is such that the extension of the second power driver is adapted to pivot the silver working assembly in a direction about said third pivot axis and the retraction of the second power driver is adapted to pivot the work platform assembly in an opposite direction around said third pivot axis. The fourth pivot connection and the second power driver are disposed outward of said third pivot connection to the work platform assembly. The second power actuator functions to keep the floor of the working platform assembly generally horizontal while said boom pivots between its mentioned raised and lowered positions. Other objects and features of the invention will be apparent and in part signaled in the following.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic elevation view of an articulated aerial platform system of the present invention in a partially raised position; Figure 2 is a cross section taken in the plane including line 2-2 of Figure 1; Figure 3 is a schematic cross section taken along line 3-3 of Figure 2; Figure 4 is a top plan view of the aerial platform system in its retracted position with a boom of the removed platform system; Figure 5 is a fragmentary schematic elevation view showing a lifting assembly of the aerial platform system in a fully elevated position; Figure 6 is a fragmentary schematic elevation view of the aerial platform system illustrating the movement of the center of gravity of the lift assembly; Figure 7 is an elongated fragmented elevation view of the aerial platform system of Figure 1 showing a boom and working platform of the system; and Figure 8 is a cross section taken in the plane including line 8-8 of Figure 7, but with the work platform removed. The corresponding reference characters indicate corresponding parts along the different views of the drawings.

DETAILED DESCRIPTION OF THE PREFERRED MODALITY Referring now to the drawings and in particular to Figures 1 and 4, the mobile lifting machine (i.e., "an articulated aerial work platform system") is generally indicated with the 10. The lifting machine 10 of the present invention it is shown comprising a base, generally indicated by 12, including a chassis 14, wheels 16 and a turntable 18 mounted rotatably on the chassis. A motor (not shown) would also be mounted on the chassis 14 to drive the rotation of the rotating platform 18 and the pumping of hydraulic cylinders described below. A lifting assembly including a lower lifter 20, an upper lifter 22, a boom 24 and a boom 26 (all generally designated by their respective reference numerals), supports a work platform, generally indicated by 28, at an upper end of the lifting assembly and is mounted at its lower end on the turntable 18. It should be understood that a lifting assembly may include or exclude the boom 24 and the boom 26 and still be within the scope of the present invention. The work platform 28 includes a floor 30, a barrier 32 around the perimeter of the floor and a control panel 34 mounted on the barrier from which the operation of the lifting machine 10 can be controlled by a worker (not shown) who is on the work platform. A pair of counterweights 36 are mounted on the side of the turntable 18 as far as possible from the work platform 28 to counterbalance the loads supported by the work platform at a distance from the center line of rotation CL of the turntable. In lift assembly it is activated by hydraulic cylinders to raise and lower the work platform 28. More specifically, a hydraulic lift cylinder 38 is extendable to pivot the lower and upper lifters 20, 22 to elevated positions, and retractable to pivot the lower and upper elevators to lowered positions (retracted). The lifting cylinder 38 is pivotally connected at its lower end to the turntable 18 and at its upper end to the upper elevator 22. A boom lift cylinder 40 functions to raise and lower the boom 24 relative to the lower and upper lifters 20, 22. A boom cylinder 42 for raising and lowering the boom 26 relative to the free end of the boom 24 is pivotally connected at one end to the boom and at its opposite end to a platform connector (generally indicated at 44) which connects the boom with the working platform 28. The lower elevator 20 comprises a parallelogram including an upper tension beam 46 and a lower compression beam 48 connected by pivot connections (designated 47 and 49, respectively) at their lower ends to the rotating platform 18 for the pivotal movement of the lower lifter with respect to the rotating platform. The pivot connection 47 that connects the upper tension beam 46 to the rotating platform 18 extends between a first wall 18A and a second wall 18B projecting upwardly from the turntable. The pivot connection 49 connecting the lower compression beam 48 to the rotating platform 18, extends between the first wall 18A and a third wall 18C projecting upwardly from the rotating platform. The lift cylinder 38 is pivotally connected to the turntable 18 between an elbow 18D projecting upwardly from the turntable and the third wall 18C. The upper tension beam 46 is disposed above the lower compression beam 48 in the same vertical plane as the lower compression beam. The upper riser 22 is a parallelogram comprising an upper compression beam 50 and a lower tension beam 52. The upper compression beam 50 is exposed on the lower tension beam 52 in the same vertical plane as the lower tension beam. The upper ends of the lower lifting beams 46, 48 and the lower ends of the upper lifting beams 50, 52 are all connected in separate locations on a lifting bracket, generally indicated with 54, so that the lifting bracket connects to the upper lift 22 with the lower lifter 20. More specifically, the upper tension beam 45 of the lower lifter is pivotally connected by means of a pivot connection 56 to the lifting bracket 54 and the lower compression beam 48 is pivotally connected by means of a power connection. pivot 58 to the lifting bracket. Similarly, the upper compression beam 50 of the upper lifter 22 is pivotally connected to the lifting bracket 54 by means of a pivot connection 60 and the lower tension beam is pivotally connected to the lifting bracket by means of a pivot connection 62. Referring to Figure 2, a bar 64 of the lift cylinder 38 is pivotally connected to a first clamp (indicated generally at 66) rigidly fixed such as by welding to the upper compression beam 50 of the upper riser 22 and, in the preferred embodiment , is the only power driver that drives the lifting and lowering movement of the lower and upper lifters 20, 22. The first bracket 66 comprises a pair of plates 680, 68B between which the cylinder rod 64 is pivotally fixed. The plates are joined together by means of cross members 70, and the right plate 68B (as seen in Figure 2) is part of a sleeve portion 72 of the first clamp, within which the upper compression beam 50 of the upper elevator 22 extends, and to which the upper compression beam is fixed rigidly. A pipe 74 of the lift cylinder 38 is pivotally connected to the turntable 18 by means of a pivot connection 75. By connecting the lift cylinder 38 directly with the top hoist 22, the ratio between the distance of the bar 64 of the cylinder extends from its tube 74 and the height of the work platform 28 is linear. In this way, the speed of movement of the working platform 28 while the lower and upper elevators 22, 20 are high is substantially constant. Referring now to Figures 2 and 3, a generally indicated time-regulating joint 76, interconnects the upper elevator 22 with the lower elevator 20 to maintain the pivotal movement of the lower and upper lifters in a regulated relationship with one another as they move. between their respective high and low positions. More specifically, the control link 76 includes a pair of connecting elements 76A76B pivotally connected at their upper ends to a cylindrical bar 78 fixedly connected between the plates 68A, 68B of the first clamp 66, which is fixed to the compression beam 50 of the upper elevator 22. The lower ends of the elements 76A, 76B of the control link are pivotally connected to another cylindrical rod 80 fixedly fixed to a second clamp, generally indicated 82, which is rigidly secured such as by welding to the compression beam 48 of the lower lifter 20. The second clamp 82 includes first and second plates 82fl, 82B between which the bar 80 extends. A structural member 82C extends between the plates 820, 82B and is fixably secured to each plate to reinforce the second clamp 82. The left plate 82A (as shown in FIG. noted in Figure 2) is part of a cup portion 82D of the second clamp 82, in which the upper end of the beam is received of compression 48 of the lower lifter 20. The compression beam 48 is fixedly connected such as by welding to the second bracket 82. The locations in which the respective ends of the control link 76 are connected with the lower link 20 and the upper linker 22 are selected to achieve a controlled pivoting movement of the lower and upper lifters while being lifted by the action of the lift cylinder 38. In the preferred embodiment, the connection of the control link 76 with the lower and upper lifters 20, 22 is selected so that the angular velocity of the upper and lower elevators while pivoting upwards from their horizontal retracted position is almost the same. However, in the preferred embodiment, the control link 76 is pivotally connected to the compression beam 50 of the upper linker 22 at a location slightly closer to the pivot connection 60 of the upper linker than the connection of the control linkage with the compression member 48 of the lower lifter 20 is with the pivot connection 62. Therefore, the angular velocity at which the upper elevator 22 pivots upwards after the extension of the lift cylinder 38 is somewhat faster than the of the lower elevator 20. As a result of the aforementioned regulated relationship between the pivoting of the upper elevator 20 and the lower elevator 22, the boom 24 and the working platform 28 connected thereto move backwards (as indicated by the curve L in figure 6) outside the base 12 when the lower and upper elevators 20, 22 are raised. The front and rear directions are in are indicated by the arrows R and F in FIGS. 1 and 6. The curve L is parallel to a curve M which is traversed by the connection point of the boom 24 with the upper end of the upper lifter 22. In this way, the lifting machine 10 has a greater lateral reach from the central line of rotation CL when the work platform 28 is raised by the lower and upper elevators 20, 22. To balance the displacement of the rear load created by the backward movement of the working platform 28, the center of gravity of the lift cylinder 38, the lower lift 20 and upper lift 22 move forward as also shown in Figure 6, towards the center line CL while the elevators are raised so that the lifting machine 10 remains balanced . The movement of the center of gravity is illustrated by the curve CG in figure 6 in relation to a vertical line V. It should be understood that the control link 76 may be arranged to produce a different relative pivoting movement between the lower lifter 20 and the upper elevator 22 without departing from the scope of the present invention. A central vertical plane P of the lift assembly of the lifting machine 10 (seen the edge in Figure 4) passes through the center line of rotation CL of the turntable 18. By way of clarity, the boom 24, the boom cylinder 40 and the working platform 28 have been removed from figure 4. As can be seen, the lifting cylinder 38 is in the vertical central plane P, the parallelogram of the lower elevator 20 rests on one side of the plane and the parallelogram of the upper elevator 22 rests on the opposite side of the plane. In this way, when the lower and upper elevators 20, 22 are retracted, they are arranged in a compact and side-by-side relationship. The balanced arrangement of the lower and upper lifters 20, 22 provides a space for the lift cylinder 38 to operate, whereby each lift can be constructed of only two beams. It is not necessary to use pairs of separate beams to allow the lift cylinder to extend through the elevators and connect to the lift assembly. Moreover, the balanced arrangement of the lower and upper lifters 20, 22 provides substantial rigidity to the lifting assembly and is particularly resistant to twisting.

With reference to Figure 4 and 5, an oscillating cylinder SC of the lifting machine 10 is defined by a vertical projection of a circle having its center on the central line of rotation CL of the turntable 18, and an approximately equal diameter to the width of the lifting machine. As can be seen in Figure 4, the circle defining the oscillating cylinder SC generally corresponds to the shape of the rotating platform 18. In the retracted position, the lifting assembly projects both backward and forward outside the cylinder. oscillation SC. In this way, the full length of the lifting machine 10 with its retracted lifting assembly remains reasonably small. However, in the fully elevated position of the lower and upper lifters 20, 22 shown in Figure 5, the lifters are completely inside the oscillating cylinder SC. The lifting clamp 54 and a floating tower 84 connecting the upper elevator 22 with the boom 24 project only slightly out of the oscillating cylinder SC. In the fully elevated position of the lower and upper lifters 20, 22, there is substantially no tail swing or front oscillation movement of the lower and upper lifters (i.e., substantially no elevator portions, lifting bracket 54 and floating tower 84 extending out of the oscillating cylinder SC). Accordingly, the worker on the work platform 28 does not have to worry while the lifting assembly is rotated about the centerline by the turntable 18 of the lower elevator 20 or the upper elevator 22 striking the structure (not shown) close to the lifting machine 10. As shown in Figure 1, the upper end of the compression beam 50 of the upper lifter 22 is pivotally connected to the floating tower 84 by means of a pivot connection 86, and the end upper of the tension beam 52 is pivotally connected to the floating tower by means of a pivot connection 88 at a location separate from the pivot connection 86. Because the upper elevator 22 and the lower elevator 20 are both parallelograms, the angular orientations of the floating tower 84, the boom 24, the boom 26 and the working platform 28 remain the same when the elevators are raised and lowered and superior. The boom 24 has an inner end mounted by means of a pivot connection 90 on the floating tower 84 for pivotal movement between the raised and lowered positions. The boom cylinder 40 is pivotally mounted at its tube end to the floating tower 84 by a pivot connection 92 and pivotally connected at its bar end by a pivot connection 94 to a boom bracket 96 fixedly attached to the boom 24. The boom is capable of moving telescopically and up to that end comprises an outer member 98 (pivotally fixed to the floating tower 84) and an inner member 100 slidably received within the outer member to extend from and retract into the outer member. The telescopic movement of the inner member 100 of the boom 24 in relation to the outer member 98 is driven by a hydraulic telescopic cylinder 102 (shown in hidden lines) within the outer member. The telescopic cylinder 102 is pivotally connected to the floating tower 84 at its tube end by the same pivot connection 90 attaching the boom 24 to the floating tower. The bar end of the telescopic cylinder 102 is connected to the inner member 100. The boom 26 is a parallelogram including upper and lower parallel ends (generally designated 104 and 106, respectively) which are pivotally connected at their inner ends by means of connections of respective pivots 108, 112 on the free end of the inner member 100 of the boom 24. As can be seen in figure 8, the upper boom end 104 includes a pair of end members 104A, 104B side by side and the lower end of the boom 106 includes a pair of end members 1060, 106B side by side. The limb members are rigidly connected to one another by respective tubes (designated 112 and 114, respectively) at the location of their pivotal connection with the free end of the boom 24. In addition, the limb members 1040, 104B of the upper extremity are connected together by a cross plate 116 at their distal ends. The cross plate 116 has been opened in Figure 8. The lower end of the boom 26 is pivotally connected by the platform connector 44 to the work platform 28. The angular orientation of the platform connector 44 and the work platform 28 remain unchanged while boom 26 is raised and lowered because the boom is a parallelogram. However, boom 24 is not a parallelogram. Accordingly, to maintain the work platform 28 in an angular level and fixed orientation for the pivotal movement of the boom 24, a master cylinder 118, an auxiliary cylinder 120 and the platform connector 44 (Figure 1) are used. The master cylinder 118 is pivotally mounted at its tube end on the floating tower 84, and pivotally connected at its bar end to the outer member 98 of the boom 24. In this way, the boom 24 is raised and lowered by the boom cylinder. 40 creates the corresponding extension and retraction of the master cylinder 118. The movement of the master cylinder 118 is transmitted by conventional hydraulic means to the auxiliary cylinder 120 to produce an opposite movement of the auxiliary cylinder. The platform connector 44 allows the auxiliary cylinder 120 to pivot to the work platform 28 relative to the platform connector and the boom 26 to maintain the level of the work platform while the boom 24 pivots. Referring to Figures 7 and 8, the platform connector 44 comprises a pair of side members 122 that have the same shape and are arranged in a face-to-face and laterally spaced relationship with one another. The side members 122 include inwardly extending ear portions 124, which are used to pivotally connect the bar end of the auxiliary cylinder 120 to the platform connector 44, as will be described hereinafter. The side members 122 and the ear portions 124 are rigidly joined together by means of a lower plate 126, so that the platform connector 44 functions as a rigid part. A first pivot connection 128 connects the outer end of the upper boom end 104 and the platform connector 44 for pivotal movement relative to one another around a generally horizontal first axis. The lower boom tip 106 is pivotally connected by means of a second pivot connection 130 to the platform connector 44 for pivotal movement relative to each other around a second generally horizontal axis spaced apart from the first axis of the first pivot connection 128. A tube 132 of the boom cylinder 42 is connected coaxially and pivotally with the inner end of the lower boom end 106 to the boom 24, and a bar 134 of the boom cylinder is connected coaxially and pivotally with the outer end of the upper boom end 104 to the platform connector 44 by the first pivot connection 128. The connection of the bar 134 with the first pivot connection 128 has been removed for purposes of clarity in Figure 8. In this manner, the boom cylinder 42 extends. through the diagonal of boom 26, maximizing the pivoting movement scale of the boom around the extremity or of the boom 24. The work platform 28 is connected to the platform connector 44 at the outer end of the boom 26 by means of a cylinder clamp and an oscillation clamp (generally designated by reference numerals 136 and 138)., respectively). In the preferred embodiment, the work platform 28, the cylinder clamp 136 and the oscillation clamp 138, constitute a "work platform assembly". The cylinder clamp 136 and the oscillation clamp 138 are interconnected to allow the work platform 28 to swing back and forth around a vertical axis 01 (Figure 7). The cylinder clamp 136 comprises a pair of mounting plates 140 rigidly joined together by means of a cross piece 142 (partially opened in Figure 8) attached to each mounting plate such as by welding. A flange 144 on each mounting plate 140 reinforces the plate. A hydraulic rotary actuator 146 of the cylinder clamp 136 is fixedly fixed to the flanges 144 of the mounting plates. As shown in Figure 7, the oscillation clamp 138 comprises upper and lower members (designated 148 and 150 respectively) that are 77 fixed fixed to the work platform 28 and pivotally connected to the rotary actuator 46 so that the work platform can be rotated from one side to the other around the axis 01 by operation of the rotary actuator. A third pivot connection 152 connects the cylinder clamp 136 to the platform connector 44 for pivotal movement of the work platform 28 around a third generally horizontal axis spaced apart from the first and second axes associated with the first pivot connection 128 and the second pivot connection 130, respectively. The auxiliary cylinder 128 is fixed in a substantially vertical position between the mounting plates 140 and close to the working platform 28 so that the auxiliary cylinder is substantially protected from contacting objects near the working platform. A bar 154 of the auxiliary cylinder 120 is connected by a fourth pivot connection 156 (FIG. 7) to the ear portions 124 of the platform connector 44 for pivotal movement relative to the platform connector about a horizontal axis spaced apart from the legs. horizontal axes of the first, second and third pivot connections 128, 130 and 152. A tube 158 of the auxiliary cylinder 120 is connected between the mounting plates 140 of the cylinder clamp 136 by a fifth pivot connection 160 for pivotal movement in relation to the platform connector 44 about a horizontal axis separated from the horizontal axes associated with the first, second, third and fourth pivot connections 128, 130, 152 and 156. The extension of the cylinder rod 154 from the tube 158 causes the work platform 28 to rotate in a left-handed direction (as seen in Figure 7) around the third pivot connection 152, and the retraction of the bar inside the tube causes the work platform to rotate in a clockwise direction around the third pivot connection. The movement of the working platform 28 driven by the auxiliary cylinder 120 responds to the pivoting movement of the boom 24 (as detected by the master cylinder 118) to maintain the level of the working platform. The structure of the platform connector 44 and the auxiliary cylinder clamp 136 results in the auxiliary cylinder 120 remaining in a substantially vertical position for the full scale of pivoting movement of the boom 24. In the preferred embodiment, the auxiliary cylinder 120 it oscillates only in an arc of approximately 3 degrees from the vertical plane. The first pivot connection 128 is located on the second pivot connection 130 and also on the third pivot connection 152. The location of the third pivot connection 152 that connects the work platform 28 to the platform connector 44, allows that the second pivot connection 130 and substantially all of the platform connector remain on the plane PF of the floor of the working platform through the full scale of 74 relative movement between the platform connector and the work platform. The fourth pivot connection 156 is located outside of, and below the third pivot connection 152, but generally at a location higher than the second pivot connection 130. The vertical orientation of the auxiliary cylinder 120 is achieved by locating the fourth pivot connection 156. The vertical orientation of the auxiliary cylinder 120 does not require a substantial horizontal distance in which to operate. Therefore, the outer end of the boom 26 can be positioned closer to the platform 28 than if the auxiliary cylinder were oriented horizontally. It is desirable to maintain the distance between the outer end of the boom 26 and the platform 28 as short as possible to reduce the bending moments and stresses in the platform connector. As a result of the reduced tensions, less material is required in the platform connector 44 and its weight can be reduced. The separation of the third pivot connection 152 from the first and second pivot connections 128, 130 also allows the bar 134 of the boom cylinder 42 to be coaxially mounted in an easy manner on the first pivot connection 128 with the upper boom end 104. This allows the boom cylinder 42 to extend across the diagonal to maximize the haul 26 ejection. In view of the above, it will be noted that the different objects of the invention are achieved and that other results are obtained advantageous. Various changes can be made in the above structures without departing from the scope of the invention, and it is intended that all matter contained in the above description or shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense.

Claims (24)

NOVELTY OF THE INVENTION CLAIMS

1. - An articulated aerial work platform system comprising a base, a work platform and a lifting assembly on the base for raising and lowering the working platform, said lifting assembly comprising: a lower lift comprising a parallelogram, said lower lifter has a lower end connected to the base for the pivotal movement of the lifter with respect to the base, and an upper end, an upper lifter comprising a parallelogram, said upper lifter has a lower end operatively connected to the upper end of the lower lifter for the pivotal movement of the upper lifter with respect to the lower lifter, and an upper end, an extendable and retractable power actuator having a lower end connected to the base and an upper end connected to the upper lifter, said actuator is extendable to pivot the upper and lower elevators to elevated positions, and retractable e to pivot the upper and lower elevators to lowered positions, a time regulating mechanism that interconnects the upper and lower elevators to maintain the pivotal movement of the upper and lower elevators in regulated time relation to one another as they move between their respective high and low positions.

2. A system in accordance with the claim 1, wherein said power driver rests in a central vertical plane of the lifting assembly.

3. A system in accordance with the claim 2, wherein said power driver comprises a hydraulic cylinder.

4. A system according to claim 2, wherein the parallelogram of said lower elevator is arranged completely on one side of said central vertical plane, and the parallelogram of said upper elevator is arranged completely on an opposite side of said plane vertical central.

5. A system according to claim 4, wherein each of said parallelograms comprises a pair of beams arranged one above the other in a vertical plane on a respective side of said central vertical plane.

6. A system in accordance with the claim 1, wherein said time regulating mechanism comprises a control linkage having an upper end pivotally connected to the upper linker and a lower end connected pivotally to the lower linker.

7. A system in accordance with the claim 6, further comprising a lifting clamp, the lower end of the upper lifter and the upper end of the lower lifter being pivotally connected to the lifting bracket at separate locations, the control link interconnecting the upper and lower lifters at selected locations so that after of the extension of the power actuator the upper elevator pivots upwards faster than the lower elevator pivots upwards.

8. A system according to claim 1, wherein said base comprises a rotating platform structure that rotates on a generally vertical axis, said rotating platform structure has an outer periphery that defines a circle that, when projected toward above, defines an oscillation cylinder, said lifting assembly being mounted on said turntable structure for rotation therewith and being configured such that when in a fully lowered or retracted position, it is projected in a forward direction and a further direction beyond said oscillation cylinder, and when in a fully elevated position, rest completely within said oscillation cylinder.

9. A system in accordance with the claim 1, wherein said upper and lower elevators and said power driver have a center of gravity that moves upwardly in a forward direction as the upper and lower elevators move from their respective lowered positions toward their respective raised position., and wherein said working platform moves a backward direction while moving upwardly from a lowered position, said upward and forward movement of said center of gravity serves to balance said forward and upward movement of the platform. work to increase the stability of the system.

10. A boom and boom system comprising: a boom having an inner end mounted for pivotal movement of the boom between raised and lowered positions, and an outer end, a boom comprising a parallelogram including upper and lower parallel ends having inner ends pivotally connected to the outer end of the boom, and outer ends, a platform connector at the outer ends of said upper and lower ends, a first pivot connection between the outer end of the upper end of the boom and the connector of platform for relative pivotal movement therebetween about a generally horizontal first axis, a second pivot connection between the outer end of the lower extremity of the boom and the platform connector for pivotal relative movement therebetween about a second axis generally horizontal separated from said first ex and generally horizontal, a first retractable and extendable power actuator for pivoting the boom between raised and lowered positions relative to the outer end. of the boom, said boom parallelogram maintains the platform connector in a substantially fixed angular orientation while the boom moves between its raised and lowered positions, a work platform assembly comprising a floor to support a worker, a third connection of pivot between the working platform assembly and the plat form connector for the pivotal movement of the working platform assembly relative to the platform connector about a third generally horizontal axis separated from said first and second generally horizontal axes, a second extendable and retractable power actuator having an upper end connected to the working platform assembly, and a lower end, a fourth pivotal connection between the lower end of the second power actuator and the platform connector for the pivotal movement of the lower end of the second power actuator in relation with the platform connector about a generally horizontal fourth axis separated from said first, second and third generally horizontal axes, the arrangement being such that the extension of the second power actuator is adapted to pivot the work platform assembly in a direction around of said third pivot axis and the retraction of the second power actuator is adapted to pivot the work platform assembly in an opposite direction around said third pivot axis, said fourth pivot connection and second power actuator being arranged outwardly of said third pivot connection to the work platform assembly, the second power actuator functions to maintain the floor of the working platform assembly generally horizontal while said boom pivots between its mentioned raised and lowered positions.

11. A system in accordance with the claim 10, wherein said second power driver comprises a power cylinder that remains in a generally vertical position while extending and retracting.

12. A system in accordance with the claim 11, wherein the power cylinder comprises a tube and a bar extending from and retractable within the tube, the tube is pivotally mounted on the work platform assembly and the free end of the bar is pivotally mounted on said fourth connection of pivot. 13.- A system in accordance with the claim 12, in which the second pivot connection does not extend below the work platform assembly when the boom is in its raised and lowered positions, and when the boom moves between its raised and lowered positions. 14. A system in accordance with the claim 13, wherein said third pivot connection is located below said first pivot connection. 15. A system according to claim 14, wherein the first power actuator extends between the inner end of one of the upper and lower ends of the boom and the outer end of the other upper and lower ends. 16. A system in accordance with the claim 15, in which the first power actuator is coaxially and pivotally mounted with the inner end of the lower end of the boom and mounted coaxially and pivotally with the upper end of the boom in said first pivot connection. 17. A system according to claim 10, wherein said first pivot connection is located on the second pivot connection. 18.- A system in accordance with the claim 10, wherein said fourth pivot connection is located below said third pivot connection. 19. A system in accordance with the claim 10, wherein said work platform assembly comprises a clamp connected to the platform connector by means of said third pivot connection, and a work platform mounted on the clamp to oscillate about a generally vertical oscillation axis, and in wherein said system further comprises a fifth pivot connection between the clamp and the upper end of the second power driver. 20. A system according to claim 19, wherein said second power driver comprises a power cylinder that remains generally vertical while extending and retracting, and wherein said power cylinder is disposed closely adjacent to said axis. of vertical oscillation of the work platform. 21. A system according to claim 10, wherein the first power actuator extends between the inner end of one of the upper and lower ends of the boom and the outer end of the other upper and lower ends. 22. A system according to claim 21, wherein the first power actuator is mounted coaxially and pivotally with the inner end of the lower end of the boom and mounted coaxially and pivotally with the upper end of the boom in said fourth connection of pivot. 23.- A system in accordance with the claim 10, in which the second pivot connection does not extend below the work platform assembly when the boom is in its raised and lowered positions, and when the boom moves between its raised and lowered positions. 24.- A system in accordance with the claim 23, wherein said third pivot connection is located below said first pivot connection.