Extensible Lift Mechanism

Abstract

The invention relates to a lifting mechanism that includes a base frame and a load supporting frame that are operatively interconnected by a scissor linkage. The load supporting frame is raised and lowered on the base frame by screw drives supporting carriers operatively connected to the load supporting frame. The interconnection between the carrier and the load supporting frame includes linkage means that universally accommodate lateral movement of the load supporting frame relative to the axes of the screws to allow the load supporting frame to be tilted relative to the base frame. The device also incorporates air cushioning supports on the base that allow the entire unit to be floatingly supported on a film of pneumatic fluid for final alignment of the support frame relative to a reference point.

Description

BACKGROUND OF THE INVENTION

This invention relates generally to material handling apparatus and more specifically to an improved type of extensible lift mechanism that is capable of raising a load to a predetermined height above the ground.

The use of plural framed hoist mechanisms that are interconnected by a scissor linkage and adapted to be raised and lowered relative to each other have found numerous applications in recent years. Examples of such units are shown in U.S. Patents issued to Carder, U.S. Pat. No. 3,341,042, and Larson, U.S. Pat. No. 3,246,876. Both such devices incorporate extensible rams or jacks that are operatively interposed between the base frame and part of the structure supported by the base frame so that extension and retraction of the rams will cause the load supporting frame to be raised relative to the base frame.

One major difficulty encountered in the ram operated extensible lift mechanisms of the type under consideration is that varying forces must be applied to move a load supporting frame or platform from a fully collapsed position to a fully extended position, the amount of force required being dependent upon the moment arm for the respective rams.

In order to initiate the upward movement of the load supporting frame, the rams must necessarily be at an angle with respect to the base frame and the load supporting frame. This requires that the collapsed condition of the lifting mechanism have the platform a considerable distance above the ground.

A partial solution to the variable force problem of the ram type units is found in McCartney et al. U.S. Pat. No. 3,474,925. While this arrangement allows for the use of a substantially constant lifting force during raising and lowering of the support frame relative to the base frame, one difficulty is that such an arrangement requires that the drive screws be located substantially at the four corners of the rectangular frames to allow the frames to be moved relative to each other.

A further difficulty is encountered in finally aligning the load or cargo on the load supporting frame relative to its final position that it is to assume. A unit such as shown in the McCartney et al. patent must have the load accurately aligned with its final destination in order to allow the transfer of the load or cargo relative to the cargo space.

A partial solution to this problem is suggested in Shaw U.S. Pat. No. 3,370,727.

SUMMARY OF THE INVENTION

The present invention is directed to an extensible lift mechanism that is capable of accurately aligning a load thereon longitudinally, transversely, and vertically relative to any fixed reference, merely by manipulation of controls forming part of the unit; in which the entire load supporting surface thereof is unobstructed to provide an extremely low profile for the unit in the collapsed position; and which has a capability of tilting the load supporting surface relative to the base for accurate alignment of the load with an adjacent surface.

The extensible lift mechanism of the present invention includes a base frame and a load supporting frame or platform connected to each other by a scissor linkage and the two frames are capable of being moved relative to each other by a pair of spaced elevating screws located adjacent one end of the base frame. The lift mechanism includes a reversible drive means cooperating with the screws for rotating the screws in opposite directions.

The screws support first and second carriers for axial movement in response to rotation thereof. The two carriers are respectively connected at spaced points on the load supporting frame by first and second linkage means that universally accommodate lateral movement of the spaced points of the frame relative to the axes of the screws to allow the load supporting frame to be tilted relative to the base frame.

To insure that the load supporting frame can be tilted a substantial amount relative to the base frame, the linkage means accommodate movement of the spaced points along two perpendicular paths that both extend perpendicular to the axis of the associated screws.

More specifically, the linkage means include a first link pivoted on the carrier about a first pivot, a second link pivoted on one of the points about a second pivot on the frame which is parallel to the first pivot and a third link pivoted at opposite ends about spaced parallel pivots, respectively defined on the first and second links. The linkage means allow lateral movement of the frame relative to each of the screws without producing any significant lateral forces or strain on the screws.

To further insure that the load supporting frame can be tilted relative to the base frame without any distorting forces being applied to either frame, the respective arms of the scissor linkage are connected at pivots on the respective frame that include spherical bearings which allow for lateral or pivotal movement of opposite ends of the arms relative to the longitudinal dimension of the arms.

According to another aspect of the invention, the drive means incorporate control means that automatically returns the two frames to a substantially planar parallel position at extreme ends of travel for the carriers on the screws.

According to a further aspect of the invention, the unit incorporates a dual mode of support means to support the unit for transportation and to allow free movement of the unit for final positioning. The first mode of support includes a plurality of caster wheels that are supported on the load supporting frame and extend below the base frame when the two frames are in the fully collapsed position. Thus, the unit may be initially located in close proximity to a final position by movement on its caster wheels, whereupon the two frames can be extended relative to each other to move the base frame into engagement with the floor or supporting surface and raise the caster wheels above the floor. The final positioning is accomplished by utilizing a plurality of air casters or cushions that will produce a supporting film of pneumatic fluid, such as air, so that the entire unit can be freely moved for final positioning.

In its preferred embodiment, the extensible lift mechanism is specifically designed for use in proper positioning of heavy parts for aircraft, such as, for example, landing gears or engines during the assembly or removal thereof relative to the remaining structure of the aircraft. For this purpose, the unit also incorporates a strut assembly to allow the load to be longitudinally tilted on the support frame for accurate alignment of the upper free end of the load with respect to structure to which it is to be attached.

If desired, the unit may also incorporate a winch to move the load onto the load supporting frame or platform.

All of the above is incorporated into a very simple unit that can easily be manufactured with readily replaceable parts that are easily accessible for maintenance and replacement.

Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and of one embodiment thereof, from the claims and from the accompanying drawings in which each and every detail shown is fully and completely disclosed as a part of this specification in which like numerals refer to like parts.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF DRAWINGS

FIG. 1 of the drawings shows a perspective view of the extensible lift mechanism of the present invention;

FIG. 2 is a side elevation view of the mechanism during the loading of a landing gear;

FIG. 3 is a view similar to FIG. 2, showing the landing gear in its supported position on the lift mechanism;

FIG. 4 is a side elevation view similar to FIG. 3, showing the lift mechanism in a partially extended position;

FIG. 5 is an end view of the lift mechanism showing the load in a tilted position on the supporting frame;

FIG. 6 is a fragmentary plan view of the scissor linkage and the frames, with parts thereof broken away;

FIG. 7 is a side elevation of the lift mechanism with parts thereof broken away;

FIG. 8 is a section view taken generally along line 8--8 of FIG. 7;

FIG. 9 is an end view of the lift mechanism with parts thereof broken away;

FIG. 10 is a fragmentary perspective view of the two frames with certain parts being in unassembled condition for clarity;

FIG. 11 is an enlarged fragmentary end view of the one end of the lift mechanism;

FIG. 12 is an exploded view of the various parts forming the interconnection between the screw carrier and the load supporting frame;

FIG. 13 is a view similar to FIG. 12, showing the various parts in assembled condition;

FIG. 14 shows the side elevation view of the assembled elements shown in FIG. 13;

FIG. 15 is a schematic illustration of the pneumatic circuit incorporated into the mechanism; and

FIG. 16 is an electrical schematic of an exemplary circuit utilized in the lift mechanism.

DETAILED DESCRIPTION

While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail one embodiment, with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit to the embodiment illustrated.

It should also be noted that while the unit will be described and has been shown in connection with the positioning of a landing gear, the invention has applicability in other areas, as will be explained below.

GENERAL DESCRIPTION

FIG. 1 of the drawings generally shows the extensible lift mechanism that includes a base or base frame 12 and a load supporting frame or platform 14 that is supported above the base 12. The two frames 12 and 14 are interconnected by a scissor linkage, generally designated by the reference 16 (FIG. 4). The extensible lift mechanism further includes drive means, generally designated as 20 for raising and lowering the platform 14 above the base 12.

The extensible lift mechanism also includes ground engaging elements or caster wheels 22 (FIG. 2) carried by the platform 14 and extending below the base 12 when the two frames are in the totally collapsed condition, for a purpose which will be described later.

THE PLATFORM DRIVE MEANS

As was indicated above, the platform drive means is capable of raising the platform 14 relative to the base 12 and of tilting the platform 14 relative to the base 12 without producing lateral forces on the fixed elements of the drive means. Furthermore, the drive means is of the type wherein all loads are balanced and the forces required for elevating the platform 14 relative to the base 12 remain constant regardless of the position of the scissor linkage.

The drive means is shown in detail in FIGS. 7 and 9 and includes a pair of columns 30 fixedly secured to the base 12 at opposite corners adjacent one end thereof, which will be referred to as the forward end of the mechanism or unit for purposes of orientation only. The columns 30 are substantially U-shaped in cross-section and open towards the rear of the unit for a purpose which will be described later.

The columns 30 each support a screw 32 for rotation about a fixed axis. Each screw is supported on a pedestal 34 carried on the base 12 and a suitable bearing 36 fixed to the column at its upper end that hold the respective screws 32 in a substantial vertical position above the base 12 wherein the axes of the two screws 32 are parallel to each other. The pedestal 34 also incorporates a worm gear drive assembly in housing 38 that allows the screw 32 to be rotated by a motor 40 having its output shaft 42 coupled to the input shaft 44 for the worm gear drive.

The motor 40 is of the reversible type and is preferably pneumatically driven. For example, the motor may be of the vane type wherein the centrifugal force holds the vanes tightly against the housing for a uniform efficient seal.

A carrier or nut 50 cooperates with each screw for axial movement in response to rotation of the screw. Each carrier 50 is connected to one corner of the load supporting platform 14 through a linkage means 52 that will be described later.

According to one aspect of the invention, the drive means consisting of the two drive motors 40 preferably capable of being interconnected to operate as a unit when the platform is to be moved an equal amount on both sides thereof, or operated independently in opposite directions.

This is accomplished by an electric clutch 54, a clutch adapter 56 and a shaft coupling 58 that interconnect the two shafts 42 of the respective motors. When the electric clutch is energized, the two motors are interconnected so that the output thereof will be simultaneously utilized to drive both screws thereby raising the platform an equal amount on opposite sides thereof.

To prevent undue stress on the clutch that interconnects the two motors during simultaneous movement of both sides of the platform or load supporting frame in the same direction, the motors are preferably synchronized periodically to prevent one motor from being overworked while the other acting as a vacuum pump. This can be accomplished by proper adjustment of the exhust from the motors in each direction of driving, which will be explained later.

THE LINKAGE MEANS

The linkage means 52 is capable of allowing the supporting platform to be tilted in opposite directions from the normal parallel horizontal position above the base without producing any meaningful lateral stresses on the screw 32. Each linkage means 52 between the associated carrier 50 on the screw 32 and the fixed point on the load supporting frame is identical and one will be described in detail with particular reference to FIGS. 12, 13 and 14.

The linkage means 52 includes first and second depending lugs 100 that are respectively fixedly secured to opposed surfaces of the carrier 50 by screws 102 and pins 104. The lower ends of the lugs each have an opening 106 defined therein with the openings 106 being aligned when the lugs 100 are in the assembled condition on the carrier or nut 50. These openings 106 thus define a first pivot axis that extends perpendicular to the axis of the screw 32.

The linkage means 52 further includes a second pair of lugs 110 that are fixedly secured to a connector 112 through bolts 114 and nuts 116 as well as washers 118. Lugs 110 each have an opening 120 therein that define points fixed relative to the support frame which is secured to the connector 112 by a bracket 121 (FIG. 7).

The linkage means 52 further includes a first link 122 that is pivoted on the carrier about a first pivot defined by openings 106. For this purpose, the link 102 has first and second circular projecting pins 124 extending from the diametrically opposed points on the periphery of the link. The linkage means also includes a second link 126 that has outwardly projecting pins 128 received in openings 120 that define a second pivot which extends parallel to the first pivot and both pivots extend perpendicular to the axis of the screw 32. An inspection of FIG. 12 shows that the links 122 and 126 are circular rings, identical in construction.

The linkage means 52 also includes means in the form of a third link 130 interconnecting the first and second links 122 and 126. The third link includes the first and second link segments 130a and 130b that are pivoted at opposite ends about spaced parallel pivots respectively defined on the first and second links. The pivot on the first link is produced by the outwardly extending circular projecting pins 132 on link 122 with identical projecting pins 134 on the second link 126. The respective projections 132 and 134 are received in openings 136 and 138 respectively defined on opposite ends of both link segments 130a and 130b. The link segments are retained on the projections by screws 140 and washers 142.

The third link 130 is therefor pivoted at opposite edns about third and fourth spaced parallel pivots that are respectively defined on the first and second links 122, 126 and these pivots extend perpendicular to the first and second pivots defined by projections 124 and 128 and also extend perpendicular to the fixed axis of the screw 32.

With the parts interconnected in the manner shown in FIG. 13, any lateral movement of the platform 14, which is connected to the member 112, in the direction of arrows 144 will cause the linkage means or universal connection 52 to pivot about the spaced pivots 124 and 128 to prevent any meaningful lateral forces from being developed on the screw 32. Likewise, any lateral movement in the direction of arrows 145 will cause the second link 126 to be moved relative to the first link 122 and such relative movement will cause the link 130 to pivot about the respective pivots on opposite ends thereof. The movement along the arrows 145 would correspond to forward and rearward movement of the platform 14 relative to the base frame while the movement along the arrows 144 would correspond to movement of the platform from side to side.

In order to accommodate the pivotal movement of the links relative to the screws 32, the two links 122 and 126 as well as the connector 112 all have enlarged openings 146 through which the screw extends to allow unobstructed lateral movement of the links and the members relative to the screw 32.

THE SCISSOR LINKAGE

As was indicated above, the scissor linkage 16 (FIG. 4) causes the rear end of the platform or load supporting frame to move in response to movement of the forward end of the platform by rotation of the respective screws 32. In addition, the scissor linkage is connected to the respective frames to accommodate the tilting movement of the load supporting frame with respect to the base frame without any binding forces being applied to the structure.

Since the scissor linkage 16 includes first and second pairs of arms that are interconnected to each other and connected to the respective frames in an identical manner on opposite sides of the unit, only one pair of arms will be described in detail with particular reference to FIGS. 6, 7 and 8.

The scissor linkage 16 includes first and second arms 160 and 162 that are pivotally interconnected by a pin 164. The first arm 160 consists of first and second transversely spaced portions 160a and 160b interconnected at opposite ends by plates 164. The spacing between the portions 160a and 160b is such that the second arm 162 may be located within the first arm, as will be described later.

The first arm 160 is connected at one end on the base frame about a fixed pivot by a lug 168 which extends between a pair of spaced lugs 172 (only one being shown) and a pivot pin 170 extends through openings in the lugs.

The second arm 162 is also pivoted about a fixed pivot on the load supporting frame or platform. The fixed pivot again includes a pin 175 extending between spaced lugs 176. Both pivotal connections between the pins and the respective arms includes a spherical bearing (not shown) to accommodate pivotal movement of the arms transversely of the unit, as will be explained later.

The opposite ends of both arms 160, 162 are respectively connected to the base 12 and platform 14 by movable pivots, that allow longitudinal movement of the arm ends in response to vertical movement of the frames. As shown in FIG. 8, the base 12 and the platform 14 each have a pair of track elements 180 each having a vertical inner surface with a recess 182 defined therein. A pivot pin 184 extends into the transversely aligned recesses 182 and the arms 160, 162 are pivoted on the pin 184. The upper portion of FIG. 8 shows the construction of the pin 184 in cross-sectional detail. The pin 184 includes a sleeve 186 having a spherical bearing 188 supported thereon and retained between opposite ends by a pair of rollers 190. Each roller 190 has a reduced portion 192 received in the elongated recess 182 and the assembly is held together by a bolt 194 and a nut 196.

The end of the first arm 160 has an opening in which a cooperating bearing member 197 is secured and the bearing member is retained in the opening by a pair of bearing plates 198 secured to opposite sides thereof. Thus, the arm 160 can universally pivot about the pin 184 to accommodate lateral tilting of the respective frames relative to each other as well as pivoting about the axis of pin 184, as will be explained later.

In order to have the two arms completely collapsible and have the second arm located entirely within the first arm, the first arm has a downwardly extending portion on the first end which is connected to the pivot pin 170 while the second or opposite end has an upwardly extending portion connected to the pin 184. Likewise, the second arm has upwardly and downwardly extending portions on opposite ends which are reversed. With this arrangement, the two arms can be completely collapsed to the solid line position shown in FIG. 7 so that the unit will have an extremely low profile in the completely collapsed position.

THE UNIT SUPPORT MEANS

As was indicated above, the extensible lift mechanism or unit incorporates a first mode of support for movement from one site to another and a second mode of support for final positioning of the unit at its ultimate destination.

The first mode of support has been generally discussed above and includes the four caster wheels 22 that are supported on the load supporting platform 14 for movement therewith. As more clearly illustrated in FIGS. 7 and 11, the caster wheels 22 are supported on the upper frame 14 by a carriage 202 that extends through an opening 204 in the base 12 adjacent each corner thereof. The upper end of the carriage 202 is supported on the cross plate 206 that extends between frame elements 208 that define a rectangular support for the carriage (see FIG. 7). The casters 22, as indicated above,are raised and lowered with the platform 14 so that initial relative movement between the platform and the base will cause the base to move downwardly into engagement with the ground. The first mode of support and transportation also includes a tow bar 210 (FIGS. 6 and 7) that is connected to the base at the forward end thereof.

After the device to be transported has been positioned on the platform 14, the platform 14 and base 12 are completely collapsed so that the base raised above the ground a sufficient distance to permit the casters 22 to make contact to allow the unit with the load or cargo thereon to be moved to its ultimate destination. Of course, it will be appreciated, if desired, the entire unit may be of the self-propelled type by providing suitable propulsion for the caster wheels in the manner that is known in the art.

The second mode of support comes into operation at the final destination for the load or cargo to accurately position the load with respect to a fixed reference. A second mode of support is more clearly shown in FIGS. 7, 10 and 11. A second support means consists of four resilient inflatable members or air casters 220 that are supported at the four corners of the base frame. Since all four casters are identical, only one has been shown in detail in FIG. 10 and particular reference will be made thereto.

The inflatable means 220 consists of a rigid plate 222 having a resilient elastomeric member 224 secured to the lower surface thereof. The elastomeric member 224 is a flat disc of high strength elastomers reinforced with high strength fabrics that takes the form of a donut, when inflated, having a recess 226 at the center thereof. A deflector 227 is positioned in the recess 226.

The base frame 12 has a pair of spaced guide means 228 having inwardly directed flanges so that the inflatable means, more particularly the plate 222 may be slidably inserted between the guides and held in fixed relation by suitable sealing means. The base frame also has an inlet opening 229 defined therein that cooperates with an aligned opening (not shown) in the plate 222 when the plate is in the assembled position.

Thus, when the pneumatic fluid, such as air, is supplied through the inlet opening 229, the air initially inflates the flat disc to a donut configuration to lift the entire load a small increment above the ground or floor. After initial inflation, the recess 226 defined by the ring 224 serves as a large piston into which air is supplied through suitable communication means or openings along the inner periphery of the ring 224 that accommodate flow of fluid from the inflatable member. The air is then deflected downwardly by the deflector 227 and escapes through a small opening that will be created between the lower surface of the donut shaped ring and the supporting surface, such as a floor in the building. This flow of air will produce an extremely thin air film that completely frees the base frame from the floor and the resiliency of the donut shaped ring automatically contours to slight irregularities in the floor to provide a constant air gap and uniform air flow between the floor and the lower edge of the ring.

The inflatable means 220 is a unit commercially available from Aero-Go Inc. 5820 Corson St Seattle, Wash. that includes a seal surrounding the air entrance which is in the form of a double adhesive backed sponge rubber tape having a protective cover thereon. In installing the inflatable means or air caster, the protective cover is removed from the tape and the entire unit is slid along the guides 228 until it engages in a stop (not shown). Thereafter, pressure is exerted on the bottom of the air caster to engage a seal with the lower surface of the base frame.

The second mode of support also includes brake means for temporarily holding the floating unit in a fixed position on the floor while the thin film of air supports the unit. This means is shown in FIG. 11 and includes a ram with a cylinder 230 having a piston rod assembly 232 reciprocable therein. The outer end of the piston rod assembly has a foot 234 secured thereto. The ram is of the single acting type wherein the piston rod assembly is normally held in retracted position by a spring 236 (FIG. 15). By supplying fluid to the head end of the cylinder 230, the foot 234 is moved to engage the floor and acts as a brake to hold the unit in a fixed position.

ADJUSTABLE HOLDING MEANS

As was indicated above, the description and drawing disclose the present invention in a specific environment for use in accurately positioning aircraft components with respect to a fixed reference for installation. For example, in extremely large aircraft, such as the B-747, the components are extremely large, heavy, and bulky and must be accurately positioned for attachment to the body structure of the aircraft. In the specific illustration, the load or cargo on the lift mechanism is illustrated as a wing gear L that must be positioned with respect to a wing for attachment thereto. This many times requires movement of portions of the wing gear for accurate alignment with openings in the wing.

Thus, the extensible lift mechanism further includes a strut assembly 250 pivoted on a support bracket 252 extending above the platform or load supporting frame 14 at a location substantially between the two columns 30. With particular reference to FIG. 7, the strut assembly 250 consists of a base 254 that is pivoted about pins 256 on the support bracket 252. A rod 258 extends through an opening in the base and is reciprocable relative to the base by an air motor 260 and a worm gear drive between the rod and motor. A bellows 262 surounds the screw drive portion of the rod when it is extended. Pneumatic fluid, such as air, under pressure drives the motor in either direction to move the rod 258 relative to the base 254.

CARGO LOADING ATTACHMENT

For extremely heavy cargo, such as a landing gear structure, it is also desirable to provide a loading attachment for initially placing the cargo on the platform 14. The loading attachment is shown in FIGS. 2 and 7 and includes a winch 270 consisting of an air motor 272 that drives a cable reel 274 supported on the platform 14 with a cable 276 extending therefrom. The rear end of the platform has a pair of ramps or runners 280 pivotally secured thereto on pins 282 so that the rear ends of the ramps 280 may be pivoted toward the ground. The air motor driven winch can then be attached to the landing gear and the air motor actuated to pull the landing gear onto the supporting surface. The landing gear can then be maintained on the platform surface by suitable chocks 290 (FIG. 4).

PNEUMATIC CIRCUIT

The pneumatic circuit for supplying fluid under pressure to the respective motors 40, 260 and 270, as well as the brake and the air casters 220, is schematically illustrated in FIG. 15. The pneumatic circuit includes a source of pneumatic fluid under pressure 300 connected to a conduit 302 with an air filter 304 and a lubricator 306 located therein. The pneumatic or air supply is delivered to the respective motors 40, 260 and 270 through four-way double solenoid spring center valves 310, 312, 314 and 316. Thus, the position of the respective valves, which is controlled by the solenoids, determines the direction of rotation of each of the motors.

The air supply conduit 302 is connected by a conduit 320 to a two way, single solenoid, spring return, normally closed valve 322 which supplies fluid to a pair of branch conduits 324. Each branch conduit 324 has an air regulator 326 incorporated therein and leads to two air casters 220. A further adjustment valve 328 is located in each of the branch conduits between the two casters.

With the pneumatic circuit as shown, the pressure regulator 326 can be adjusted to control the supply of fluid to respective pairs of air casters located on opposite sides of the lift mechanism to compensate for an imbalance of the platform that may result from the load being laterally offset on the platform. Furthermore, the control of the pressure of fluid between the fore and aft air casters is controlled by the valves 328. Preferably, the two air casters located adjacent the regulators would be located in the aft end or rear end of the lift mechanism where the majority of the load would normally be centered.

The supply of air to the pneumatic brakes or rams is directed through a conduit 330 having a two-way, single solenoid, spring return, normally closed valve 332 and a needle valve 334 located therein.

ELECTRICAL CIRCUIT

The electrical circuit for supplying energy to the various solenoids on the valves in FIG. 15 as well as the electric clutch 54 is shown in FIG. 16. The electric circuit includes a connection 400 for a power supply to the lift mechanism. A master switch 402 is incorporated in the two lines 404 and 406 leading from the source to the transformer 408 with suitable fuses 410 incorporated therein. The transformer produces a 12 volt output supply with one line of the output connected to each of the 8 solenoids through a line 414. The output of the transformer 414 is also connected through a line 416 and a normally open switch 418 to the input contacts of a tilt DPDT spring centered switch 420 and to the input contacts of a up-down 3 PDT, spring centered toggle switch 422.

The first contact 420-1 of the switch 420 is connected by a line 424 through a limit switch 426 and one of a pair of contacts of the limit switch 428 to solenoid 430 on one end of the valve 310 that controls the flow of fluid to the right hand motor 40. The second contact 420 -2 of the switch 420 is connected through a line 432, limit switch 434 and one contact of limit switch 436 to the second solenoid 438 on valve 310.

The third contact 420 -3 of switch 420 is connected through line 440, limit switch 442, one contact of limit switch 444 to solenoid 446 which is on one end of the valve 312 leading to the left hand motor 40. A fourth contact 420-4 of switch 420 is connected through line 450, limit switch 452, one contact of limit switch 454 to solenoid 456 on the opposite end valve 312.

The first contact 422-1 of switch 422 is connected through line 460 to solenoid 430 through the first contact of limit switch 428. The second contact 422-2 is connected through line 462 and the first contact of limit switch 436 to solenoid 438. The third contact 422-3 of switch 422 is connected through line 464, and the first contact of limit switch 454 to solenoid 456. The fourth contact 422-4 of switch 422 is connected through line 466 and the first contact of limit switch 444 to solenoid 446. The remaining two contacts 422-5, 422-6 of the switch 422 will be described in connection with the circuit to the clutch 54.

The two switches 420 and 422 control the direction of the respective screw drive 32. If for example, the platform is to be raised simultaneously on both sides, switch 422 is moved to the uppermost position energizing solenoids 430 and 456 to drive the screws 32 in the direction to move the carriers 50 upwardly while movement of the switch 432 to its lowermost position will energize solenoids 438 and 446 to lower the platform with respect to the base.

A separate electric energy supply for the clutch 54 is delivered from the bridge rectifier 470 to one side of the clutch 54 through a line 472 having a toggle switch 474 therein. The second output contact of rectifier 470 is connected to the third input contact of the switch 422 through a line 480 having a fuse 482.

The fifth contact 422-5 cooperating with the third input contact of switch 422 is connected through a line 482, the other contact of limit switch 454, and the other contact of limit switch 428, to the clutch 54. The sixth contact 422-6 of switch 422 is connected through line 490, the other contact of limit switch 436 and the other contact of limit switch 444 to the clutch through line 486.

The respective limit switches 428, 436, 444 and 454 are located at opposite ends of the path of travel of the respective carriers and are normally closed so that the clutch may be controlled through the switch 474. However, assuming that the right hand side of the platform is higher than the left hand side, and the switch 422 is actuated to energize solenoids 430 and 456, when the right hand carrier reaches the upper extreme position or limit of travel, limit switch 428 would be opened to interrupt the circuit to solenoid 430 thereby closing the valve 310 to the right hand motor while the left hand motor would continue to operate until the left hand carrier reached its upper extreme limit of travel, whereupon limit switch 444 would be actuated to interrupt the circuit to solenoid 446. The same condition would occur with respect to downward travel by appropriate actuation of switches 436 and 444. It will also be appreciated that the respective limit switches 426, 434, 442 and 452 would be appropriately positioned with respect to the platform to define the maximum degree of tilt in either direction for the platform and, when this maximum degree of tilt is reached, the appropriate mercury switch would interrupt the circuits to the various solenoids.

The control to the strut tilt assembly motors 260 include a SPDT, spring centered toggle switch 500 that has its input contact connected to one output lead of the transformer 408 through a line 502. The first output contact 500-1 of switch 500 is connected through line 502 and limit switch 504 to solenoid 506 while the second output contact 500-2 is connected through line 508 and limit switch 510 to solenoid 512. The solenoids 506 and 512 are respectively located on the opposite ends of the valve 314 which controls the flow of fluid to the strut motor 260. Actuation of the toggle switch 500 in the appropriate direction will energize through the solenoid 506 or 512 to extend or retract the strut or rod 258. The respective limit switches 504 and 510 would define the extreme positions of travel for the rod or strut.

The circuit to solenoid 520, forming part of valve 332,includes a switch 522 having both output contacts connected through line 524 to the solenoid 520 so that actuation of the switch in either direction will energize the solenoid and extend the piston rod in the brake.

The solenoid 530 forming part of the valve 322 is connected to transformer output through a line 532 and a switch 534.

The operation of the entire circuit will be described later in connection with a loading and unloading operation.

ADJUSTMENT OF DRIVE MOTOR 40

As was indicated above, it is preferable to adjust the speed of the two drive motors 40 to assure that both motors are synchronized when the clutch is actuated and the screws are both being rotated in the same direction to prevent undue stress on the clutch as well as the motor. This is accomplished by a plurality of adjustable valves 350 cooperating with the exhaust port of the respective valves 310 and 312. This adjustment of the speed of the respective motors should be accomplished each time the air supply through the unit is changed to prevent the above mentioned undesirable results.

The same control may be incorporated into the exhaust ports of the strut control valve 314 to control the speed of the motor 260.

OPERATION

The operation of the unit will be described in connection with the loading, transporting and final positioning of a landing gear. Initially, the rear end of the lift mechanism or the unit is aligned with the landing gear L (FIG. 2) and the ramps 280 are lowered. The winch motor is then actuated by the manual actuation of valve 316 to allow the cable 276 to be unwound and attached to the forward end of the landing gear L. The valve 316 is then manually actuated in the opposite direction to pull the landing gear onto the platform 14 to the position shown in FIG. 3. At this time, the chocks 290 may be positioned adjacent the forward and rearward wheels of the landing gear and the ramps 280 raised for transportation.

The rod or strut 258 is appropriately extended and attached at a suitable location to the upper portion of the landing gear so that the entire unit is substantially fixed relative to the lift mechanism. A powered vehicle, such as a tractor, can then be attached to the drawbar and the landing gear transported to its ultimate site of installation utilizing the caster wheel support. After the lift mechanism has been properly positioned with respect to the point of installation on the aircraft, the up-down switch 422 is moved to the upward direction to energize solenoids 430 and 456, and clutch 54 simultaneously casuing both sides of the platform to be raised from the position shown in FIG. 3 to be that shown in FIG. 4. During the initial movement of the two platforms relative to each other, the base frame 12 will be lowered into engagement with the adjacent floor F and subsequently the platform or upper support frame 14 will be elevated above the base frame. When the upper end of the landing gear is in general alignment with the attaching point of the aircraft, switch 422 is released to interrupt the circuit to the respective solenoids.

At this time it may become necessary to tilt the landing gear either in the forward and rearward direction or the transverse direction to have the respective connections properly aligned. The forward and rearward tilting of the landing gear structure is accomplished by actuation of the appropriate solenoid 506 or 512 through switch 500 to move the landing gear structure as generally shown in FIG. 4. The tilting of the landing gear transversely is accomplished by actuating the switch 422 in the appropriate direction to energize the respective solenoids cooperating with the motors 40. When the final angular position and longitudinal position has been reached, it may also become necessary to reposition the entire structure relative to the body of the aircraft. This is accomplished by energizing solenoid 530 to supply pneumatic fluid to the respective air casters 222 that will result in floatingly supporting the entire unit and cargo on a thin film of fluid to allow the operator to manually move the unit with a very small amount of force to its final position relative to the point of installation.

It should be noted that during the tilting movement, the platform will generally pivot about an axis extending centrally of the elongated platform since both motors are rotating the screws at the same speed and in opposite directions This tilting movement will result in having the points of connections of the platform move laterally relative to the carriers 50. This lateral movement will cause a pivoting of the appropriate link in the linkage means 52 and prevent any lateral forces from being applied to the screws 32. The lateral movement will also cause a small amount of pivotal movement of the respective ends of the arms about the spherical bearing supports.

After the platform has been tilted the desired amount on the base, it may become necessary to raise or lower the platform while it is in the tilted position. This may be accomplished by actuating the switch in the appropriate direction to drive both screws in the same direction. Because the motors operate at the same speed, the angle of tilt of the platform will remain the same. Also, the angular position of the scissor links between the platform and base, when the platform is tilted, will add stability to the platform.

SUMMARY

It will be seen that the present invention provides extremely rugged structure that can be utilized for transporting various types of loads or cargo a substantial distance and allow a universal movement of the entire unit for final positioning relative to a fixed point. In addition, a platform can readily be tilted to accommodate the angle a receiving unit, such as an aircraft, may be located.

To reiterate, while the lift mechanism has been shown as described in connection with the transportation and final positioning of extremely heavy units that require accurate positioning, numerous other uses are available for a unit of this type. For this example, the expansible mechanism with the tilt capability could be readily utilized as a cargo loader for other material handling equipment.

Claims

I claim:

1. In an extensible lift mechanism having a base frame and a load supporting frame connected for relative movement by a scissor linkage, first and second screws extending above said base frame at spaced locations, said screws being supported for rotation at spaced parallel axes on said base frame; reversible drive means cooperating with said screws for rotating said screws in opposite directions; first and second carriers respectively cooperating with said screws for axial movement in response to rotation of said screws; and first and second linkage means between respective carriers and spaced points on said load supporting frame, said linkage means universally accommodating lateral movement of said spaced points relative to said axes in response to differential rotation of said screws to allow tilting of said load supporting frame relative to said axes.

2. An extensible lift mechanism as defined in claim 1, in which each linkage means includes links accommodating lateral movement in two intersecting paths perpendicular to said axes of said screws.

3. An extensible lift mechanism as defined in claim 1, in which each linkage means includes a first link means pivoted on said carrier about a first pivot; a second link means pivoted on one of said points on a second pivot parallel to said first pivot, said first and second pivots extending perpendicular to said fixed axes; and means interconnecting said first and second link means.

4. An extensible lift mechanism as defined in claim 3, in which said means interconnecting said first and second link means includes a third link means pivoted at opposite ends about spaced parallel third and fourth pivots respectively on said first and second link means, said third and fourth pivots extending perpendicular to said first and second pivots and said fixed axes.

5. An extensible lift mechanism as defined in claim 1, in which said load supporting frame includes floor engaging elements, said floor engaging elements being dimensioned to raise said base frame above a floor upon movement of said carriers to an extreme position adjacent said base frame.

6. An extensible lift mechanism as defined in claim 5, further including inflatable means defining recesses below said base frame; and means for supplying pneumatic fluid to initially inflate said inflatable means and flow into and from recesses between said inflatable means and the floor to produce a film of fluid to floatingly support said base frame on the floor.

7. An extensible lift mechanism as defined in claim 6, including brake means on said base frame for selectively holding said base frame in an adjusted position while said base frame is floatingly supported on the floor.

8. An extensible lift mechanism as defined in claim 1, in which said frames are polygonal and said screws are located at adjacent corners of one end of the said base frame.

9. An extensible lift mechanism as defined in claim 8, in which said scissor linkage includes first and second pairs of arms pivotally interconnected intermediately opposite ends, one end of each first arm pivoted, on one end of said base frame adjacent said screws and one end of each second arm pivoted about a fixed pivot on said load supporting frame adjacent said screws; guide track means on said base frame and said load supporting frame, movable pivots for opposite ends of said arms guided in said track means, and in which all of said pivots for said arms accommodate lateral movement of said frames relative to each other.

10. An extensible lift mechanism as defined in claim 1, further including control means cooperating with said reversible drive means for selectively rotating said screws in opposite directions to tilt said load supporting frame relative to said base frame.

11. An extensible lift mechanism as defined in claim 10, in which said control means includes means for raising and lowering said load supporting frame relative to said base frame while maintaining a preset angle of tilt of said load supporting frame relative to said base frame.

12. An extensible lift mechanism as defined in claim 11, in which said control means includes means for automatically leveling said load supporting frame at opposite extreme limits of travel of said carriers on said screws.

13. An extensible lift frame as defined in claim 1, further including control means for cooperating with said drive means for rotating said screws synchronously or independently.

14. An extensible lift frame as defined in claim 1, in which said control means includes means for simultaneously rotating said screws in the same direction or in opposite directions.

15. An extensible lift mechanism as defined in claim 1, in which said scissor linkage includes first and second pairs of arms pivotally interconnected intermediate opposite ends, each arm having one end connected by a fixed pivot to one of said frames and an opposite end connected by a movable pivot to the other of said frames and in which said connections of said arms include spherical bearings accommodating tilting of said load supporting frame relative to said base frame.

16. An extensible lift mechanism as defined in claim 1, in which said drive means includes a pneumatic motor for each of said screws.

17. An extensible lift mechanism as defined in claim 16, further including releasable coupling means for interconnecting said motors to synchronously drive both screws with both motors.

18. In an extensible lift mechanism having a horizontal base frame and a load supporting frame with scissor arms interposed between said frames; first and second screws extending above said base frame at spaced locations and supported for rotation about substantially vertical axes; drive means for rotating said screws in opposite directions on said base frame; carrier means cooperating with each screw; and linkage means connecting said carrier means to said load supporting frame at spaced locations, said linkage means universally accommodating lateral movement of said load supporting frame relative to said vertical axes upon selective rotation of said screws for tilting said load supporting frame relative to said vertical axes while minimizing lateral forces on said screws.

19. An extensible lift mechanism as defined in claim 18, in which said linkage means includes a plurality of links pivotally interconnected and pivoted to said carrier means and supporting frame to accommodate lateral movement of said supporting frame in two intersecting paths perpendicular to said axes.

20. In an extensible lift mechanism including a base frame and a load supporting frame supported above said frame by scissor arms; a carrier; drive means for moving said carrier in opposite directions along a fixed axis extending above said base frame; and connection means between said carrier and supporting frame, said connection means including linkage means having opposite ends respectively pivoted about spaced parallel axes respectively defined on said carrier and said supporting frame, said spaced parallel axes extending perpendicular to said fixed axis and said linkage means universally accommodating lateral movement of said supporting frame relative to said fixed axis.

21. An extensible lift mechanism as defined in claim 20, in which said linkage means includes a plurality of link means pivotally interconnected and pivoted about said spaced parallel axes to accommodate lateral movement of said supporting frame in plural directions perpendicular to said fixed axis.

22. An extensible lift mechanism as defined in claim 21, in which said linkage means includes a first link means pivoted on said carrier, a second link means pivoted on said supporting frame and third link means pivoted at opposite ends on said first and second link means respectively.

23. In an extensible lift mechanism including a base and a platform; a scissor linkage interposed between said base and said platform; means for extending and retracting said platform above said base between collapsed and extended positions; a plurality of spaced wheels secured to said platform, said wheels extending below said base to engage a support surface and support said lift mechanism when said base and platform are in a collapsed position; a plurality of inflatable members extending from a lower surface of said base; means for selectively supplying pneumatic fluid under pressure to said inflatable members; and means accommodating flow of fluid from said members to produce a supporting film of fluid between the inflatable members and said support surface to support said lift mechanism on said supporting film of fluid when said base and frame are extended to a position where the wheels are spaced from the floor and pneumatic fluid is being supplied to said inflatable members.

24. An extensible lift mechanism as defined in claim 23, in which said inflatable members each include a flat rigid plate and an elastomeric ring attached to one surface of said plate and in which said lower surface has guide means for receiving said plate to releasably support said inflatable member on said surface.

25. An extensible lift mechanism as defined in claim 23, further including brake means for temporarily holding the floating unit in a fixed position on the support surface.