CA2373692A1 - Simplified multi axis, lightweight, steerable power drive unit, for handling aircraft cargo - Google Patents

Abstract

The system and apparatus of the present invention is generally comprised of an articulated, steerable, load absorbing multi-axis, recessed, cargo handling device, which is installed within and below the cargo deck of an aircraft being suspended from the underside of a structurally reinforced deck plate. The apparatus of the present invention is preferably equipped with at least one motor driven, rotationally activated wheel assembly mounted in the middle of a load absorbing, multi-axis mounting armature, with a passive spring response system at one end of said armature, which permits said rotationally activated wheel assembly to be passively moved below the plane of the cargo deck without operator manipulation, actuators, motors or gears, to permit the efficient passage of pallets over the deck plate of the present invention. The preferred embodiment of the current invention incorporates an electrically actuated pair of DC brushless motors, and a control module, connected to a rotating deck plate apparatus to effect movement of the drive unit, about a vertical and horizontal axis with the effect of selectively changing the direction a given cargo pallet is moved. The present invention further incorporates a mechanical clutch assembly to disengage the powered wheel drive system to effect movement of the pallet assembly in forward or reverse without the need for fully retracting the wheel drive assembly. The present invention also incorporates a circular CAM track and plurality of cam followers with clean-outs and a rack and pinion gear drive assembly mounted on the structurally reinforced inner deck plate, to effect rotation of the deck plate inside an outer deck collar. The innovative details of the preferred embodiment of the present invention will become obvious to those skilled in the art of aircraft cargo handling systems by examining the drawings and text contained herein and reducing them to practice, to achieve a reduction in maintenance, lighter weight, fewer components, and higher reliability than previous rotationally activated-steerable aircraft cargo handling systems associated with prior art.

Description

FIELD OF THE INVENTION
This invention relates to a novel, deck plate mounted, passively retracted, mufti axis load absorbing, steerable powered drive unit (SPDU) assembly used for the powered movement of containers and pallet assemblies typically installed within the cargo floor of freighter aircraft BACKGROUND OF THE INVENTION
Various types of aircraft cargo handling systems have been in use for decades, and although these existing steerable powered drive unit (SPDU) systems continue to be employed, numerous design deficiencies, and operational to problems associated with the complexity and obsolescence of these SPDU
designs are still widely used today. The persistence of these designs frequently result's in poor reliability, and inadvertent damage to the SPDU, and aircraft floor structure.
Prior design precedence in support of the aforementioned assertions can be seen in the former SPDU products of Aero Union, a U.S. Corporation located in i5 California, wherein a cargo powered roller system (CPRS) designated as design No. 11790 (circa 1988) had no passive retraction/extension capability, or mufti-axis load path transfer capability.
Paramount among the problems confronting existing SPDU design are the mufti axis loads imposed on all SPDU's when moving pallet assemblies over the 2o motor drive units. There is currently no existing SPDU design which accommodates mufti-axis loading. Although as disclosed in U.S. Patent 5,547,069 by Robert J.
Pritchard, issued on August 20, 1996, Pritchard describes a singular means to accommodate the transfer of vertical loads imposed on the powered motor drive by using a canister assembly. Further, although Pritchard in said patent discloses a 25 plural "compression spring" assembly with a "cam engaging plate" to accommodate said vertically imposed loads and manual retraction, Pritchard does not address any means to mitigate and otherwise transfer to the aircraft sub floor structure, tangent axis loads imposed on said springs. No such method was disclosed by Pritchard, or exists in any SPDU currently being manufactured.
3o Further, as disclosed in the Pritchard U.S. Patent 5,547,069, and more specifically depicted in sectional drawing "9" of said Pritchard patent, Pritchard discloses the external mounting of several SPDU components on the outside periphery of the external canister instead of on the inner deck plate, which constricts and otherwise causes a reduction in the diameter and surface area of said structurally reinforced inner deck plate, thereby inversely reducing the width and length of the power drive wheel or roller assembly. 3 This results in an overall reduction between the frictional rubber surface area, of the power drive wheel/roller, and the underside of a pallet. In synopsis, a smaller wheel generally equate to less friction, and thereby poorer handling characteristics of the pallet.
Further, in all aircraft design and engineering functions, the methodologies employed by aircraft structural and systems designers take into account the cumulative value of repeated weight savings wherever multiple components, assemblies, and systems are incorporated within a given aircraft. For example, a io Boeing 747 freighter aircraft. Eliminating parts, and complexity in any aircraft component or assembly generally results in increased payload capacity which can be used for fuel, passengers, cargo, or other payload materials. In this regard, many existing SPDU designs equipped with passive response, spring actuated, or compression strut actuated drive wheel or roller retraction and extension sub 1s systems, require an external canister shaped enclosure, mounted below the cargo deck of an aircraft, to support and otherwise absorb loads transferred from said spring or strut assemblies. These canister designs, as disclosed in the Pritchard U.S. Patent 5,547,069, and specifically depicted in figures "3", "8" and "9"
of said patent, denote one such canister referred to as, a "housing". Further Pritchard also 2o denotes a second "canister" external to the interior "housing". Further Pritchard also clearly indicates in U.S. Patent 5,547,069 that the "support means" includes, and directly links, the load transfer path from a "load bearing swing arm", to a "circular bottom". Said "circular bottom" comprises the lower part of a "cylindrical outer housing" through which the loads are transmitted to the aircraft floor structure. This 2s complex load path described by Pritchard in U.S. patent 5,547,069, creates additional weight due to the load bearing "cylindrical outer housing". Further Pritchard does not disclose a direct load path to a structurally reinforced deck plate in the aircraft floor structure. Nor does Pritchard disclose a means to accommodate lateral, longitudinal, or tangential axis dynamic loads imposed on the SPDU
3o assembly. Further, the load transfer methodology as disclosed by Pritchard physically places the friction engagement means, or powered wheel/roller assembly, dynamic load response system, and all ancillary components of the Pritchard SPDU above the load transfer means or "cylindrical outer housing".

Although Pritchard does disclose the utilization of a singular "sheet-like cover" placed over the top of the "cylindrical outer housing" he does not disclose any means of transferring said dynamic, multi-axis loads, to said "sheet-like cover".
Nor does Pritchard disclose any alternate means of an omni-directional, or uni-s directional load transfer methodology, which would eliminate the additional weight, and the inherent need of Pritchard's design for canisters or housings to accommodate dynamic load transfer to the aircraft structure.
Further, regarding issues of impact damage, considerable physical damage can occur to SPDU's when impacts with pallets are experienced lateral to the to direction of motion, of the powered drive unit. Although Pritchard, in Figure "3" of U.S. Patent 5,547,069, discloses an angular or sloped "flexible protective shield" for the purposes of protecting the powered drive unit from "foreign substances", he does not disclose any means for mitigating lateral impact loads on said drive assembly, or a means to transfer the torsion loads resulting from said impacts.
is Further, regarding issues of lubricity, most SPDU systems use ball bearings to effect translation, particularly in the vertical axis as disclosed by Pritchard, in Figure "9" of U.S. Patent 5,547,069. These roller or ball bearings are typically numerous, resulting in a higher number of parts, and a consequent weight increase in the overall SPDU assembly. The use of bearings also results in higher 2o maintenance as they are also difficult to clean when installed within an SPDU.
Further, even the employment of bushings although lighter, can achieve better maintenance, and reliability, bushings can still be susceptible to dust and foreign object damage, particularly over long periods of repetitive motion.
Further, deficiencies associated with the manufacture of existing, and older 2s "canister" based load transfer methodologies for aircraft SPDU's involve close milling tolerances. Frequently due to a lack of precision milling, SPDU
canisters suffer cracks, and subtle increases in weight, due to the creation of SPDU
canisters with uneven thicknesses, or an elliptical shape. This subtle elliptical shape also causes more wear and tear due to a lack of circular symmetry in the vertically 30 oriented rotational actuation system. If off circular geometry is created, this deficiency results in a loose fit with the deck plate, in turn resulting in more dust and debris being admitted below the deck plate.
Further, existing SPDU's suffer from Steerout wherein the drive assembly actuates the SPDU assembly beyond the maximum range of the gear rack, and prevents the optical reader from self indexing its position relative to the gear rack, resulting in derailing, or preemptive shut down of the SPDU if the optical encoder cannot self locate. This event delays cargo operations, causes damage to the SPDU assembly and at times the aircraft also. A need exists to address a passive shutdown mechanism which prevents steerout and preserves operation of the SPDU without maintenance intervention to get the SPDU back on line. Further, in terms of the way SPDU's can be installed, faulty installation of an SPDU
within the aircraft cargo floor can also effect steerout, and result in unnecessary damage.
A further area requiring new design involves the uses of AC motors and the to resultant hard start when power is applied. A soft start or gradual application of power in an SPDU does not currently exist.
BRIEF SUMMARY OF THE INVENTION
The current aircraft cargo handling system solves the aforementioned problems associated with complex, heavy, poorly accessed, inefficient and ~5 ineffective motor drive unit response methodologies associated with aircraft cargo based steerable powered drive units (SPDU). The preferred embodiment of the current invention addresses these deficiencies by achieving directional control of cargo pallet assemblies with fewer components, a more efficient and simpler multi axis load transfer methodology, resulting in decreased weight, preventing 2o unnecessary wear on components, mitigating pallet impact, improving friction between the pallet and SDDU, and the gradual application of power to achieve soft movement of the pallet.
The preceding assertions, are achieved by the following components and assemblies, 25 1 ) A simplified, multi axis motor drive unit mounting frame which accommodates a compressable bushing assembly, at one end of the mounting frame, and a spring response system at the opposite end of the fram~.

2) An Orbital ball joint and spherical washer assembly to accommodate 3o multi-axis loads on springs and to further prevent shearing, and bending resulting in fewer damaged or broken spring rods, 3) A significant simplification of the SPDU load transfer path, into a structurally reinforced deck plate, resulting in the elimination of the canister or housing assembly.

4) A self cleaning capability to remove dust, and debris, which eliminates the requirement for numerous bearing assemblies, and prevents wear or damage to rotational actuation components, achieved by means of CAM
follower openings, self cleaning bushing assemblies. A further benefit of the self cleaning capability, is also the elimination of a secondary protective outer canister or housing assembly to prevent dust from to entering the apparatus from below the SPDU assembly.

5) A magnetic reader and plurality of ferrous pins which prevent steerout beyond index range of the gear rack to prevent damage to the SPDU, and to minimize down time due to SPDU realignment.
The integration of the foregoing assemblies, embodied as interchangeable I S components within the present invention, achieve the foregoing objectives, and provide the novel means to achieve simplified functionality of the preferred invention over existing SPDU's.

BRIEF DESCRIPTION OF THE DRAWINGS
FIG.1 - Is a perspective inverted view of the underside of a multi axis load absorbing, steerable, aircraft cargo power drive unit assembly depicting the MDU
s frame and bushing attachment assembly, and various other components of the present invention.
FIG.2 - Is a perspective inverted view of the underside of a multi axis load absorbing, steerable, aircraft cargo power drive unit assembly depicting the deck plate mounted spring/load transfer assembly, optical encoder, and various other ~o components of the present invention.
FIG.3 - Is a perspective topside view of a multi axis load absorbing, steerable, aircraft cargo power drive unit assembly depicting the deck plate and power driven wheel assembly, retractable lifting handles, and single point suspension spring/load transfer assembly, and various other components of the present invention.
I5 FIG. 4 - Is a perspective part drawing of the load bearing circular bushing and cam assembly of the present invention.
FIG. 5 - Is a perspective part drawing illustrating the single point spring suspension assembly, the load axis lines, and MDU frame and wheel assembly of the present invention.
2o FIG. 6 - Is a perspective part drawing illustrating the multi axis load absorbing polymer bushing assembly, MDU frame and wheel assembly of the present invention.
FIG. 7 - Is a perspective drawing illustrating the load axis lines absorbed by a single point suspension spring ball joint and rod assembly, of the present invention.

DETAILED DESCRIPTION OF THE INVENTION
1n general, the invention comprises a novel design and approach in the configuration, capability, and operation of aircraft based cargo handling systems.
The invention is now described in terms of the FIGURES 1 through 7 to more fully s delineate in more detail the scope, materials, conditions, and operating methods of the present invention. Many of the parts and components of the present invention are hereinafter described as being "assemblies." As used herein, the word "as-sembly" or "assemblies" refers to the totality of related parts and pieces, related to a given component and its operability, and is not to be considered as limiting to a to particular part, piece, or operation of the invention.
MOTOR DRIVE UNIT (MDU1 ASSEMBLY
As depicted in Figures 1 through 3, 5, and 6, the preferred embodiment of the present invention comprises a motor drive unit (MDU) assembly consisting of a moveable, load bearing Inner Deck Plate 1, which rotates around a vertical axis to ~s change the orientation of said MDU assembly. Further, said Inner Deck Plate 1, of the preferred invention also provides a mounting surface interface for the Multi Axis MDU Frame 41, which in turn connects and provides a mechanical mounting interface to the MDU Mounting Plate 4. Said MDU Mounting Plate 4, further provides the primary mounting interface to a DC Brushless Motor/Harmonic Drive 2o Assembly 3. The DC Brushless Motor/Harmonic Drive Assembly 3, provides the horizontal actuation means to rotate the Flexible Drive Wheel 9, which creates a friction connection and directional force between the Flexible Drive Wheel 9, and a cargo pallet. Said Flexible Drive Wheel 9, can accommodate dynamic loads imposed along a vertical axis by compression of either a composite rubber tire or 25 air filled rubber tire, or other compressible material means common to those skilled in the art of conveyor and cargo handling systems. Further said motor drive unit (MDU) assembly is protected from lateral impact of unintentional or inadvertent contact with pallets and container assemblies by means of a Wheel Mounting Frame Chamfered Edge 5, which deflects the pallet and consequent force of the 3o impact upward, and away from the MDU assembly thereby preventing damage and increasing the interval between repair and maintenance cycles. In the horizontal lateral axis the DC Brushless Motor/Harmonic Drive Assembly 3, provides direct power transfer to effect horizontal movement of the Flexible Drive Wheel 9, while a second vertical DC Brushless MotorIHarmonic Drive Assembly 3, achieves circular movement about a vertical axis by 'means of a Reduction Gear Assembly 8, which in turn is connected to a vertically oriented Pinion/Gear Assembly 7, that transfers the loads to a Gear Rack 6. The cumulative horizontal lateral and vertical load transfer path of the aforementioned gear assembly is common to those skilled in s the art of mechanical drive systems. The use of the aforementioned drive components in conjunction with a DC Brushless MotorIHarmonic Drive Assembly 3, permits for adjustable power settings and soft start engagement of the drive system using a Control Module 62, to effect gradual, or soft movement of the cargo pallets and containers. To move the pallets and cargo containers without the power 1o actuated MDU assembly, a Mechanical Clutch Assembly 10, is connected to the DC Brushless MotorlHarmonic Drive Assembly 3, to disconnect the Reduction Gear Assembly 8. Said Mechanical Clutch Assembly 10, being employed by means of a composite or wire cable which can be connected in series to multiple units of the present invention to disengage the gear and drive means thereby allowing cargo ! s handling personnel to effect freedom of movement about the vertical and horizontal axis of the drive system. Other variations of the present invention can also include an electrically activated brake assembly in lieu of a mechanical clutch to achieve deactivation of the gear mechanism to achieve un-powered pallet movement.
To undertake maintenance, the preferred embodiment utilizes a plurality of 2o interface screws, fasteners, or other mechanical fastening means integrated through the upper surface of the structurally reinforced Inner Deck Plate 1.
Further said Inner Deck Plate 1, also provides a mounting surface for a pair of spring loaded, Retractable Lifting Handles 2, which can also be recessed into the Inner Deck Plate 1, to be flush with the deck plane of the aircraft floor.
2s The preferred embodiment of the present invention incorporates the efficient and space saving mounting of all components inside the outward periphery of the Inner Deck Pfate 1. This redesigned packaging and integration of all the components of the present invention within the outward periphery of the Inner Deck Plate 1, results in an expansion of the surface area available for the Flexible Drive 3o Wheel 9, and permits a wider, and longer Flexible Drive Wheel 9, thereby achieving increased contact area between the pallet.
Further, when used near the peripheral threshold of an aircraft cargo door, the drive system of the present invention may also be augmented with a retraction drive consisting of a screwjack assembly attached at one end to the Inner Deck Plate 1, and simultaneously attached at the other end to the Multi Axis MDU
Frame 41, which when coupled with an electric motor and a mechanical or electrically s activated clutch assembly, can achieve compression of the Spring Assembly 46, and thereby retract the Flexible Drive Wheel 9, below the surface of the aircraft cargo floor to achieve closing of the aircraft cargo doors, over top of the retractable, steerable, power, drive unit. Said screw jack assembly can also be integrated as part of the Spring Rod 48, with a retraction motor attached to the spring rod, to to achieve spring compression.
Other mechanical retraction methodologies familiar to those skilled in the art have been contemplated for integration within the present invention including a vertically oriented sinusoidal shaped circular cam track, which when at a certain point in horizontal rotation effects retraction or extension.
~5 ROTATIONAL BUSHING ASSEMBLY
As depicted in Figures 1, through 3, 5 and 6, the preferred embodiment of the present invention comprises a plurality of Cam Followers 23, and a plurality of Circular Cam Bushing 21, means affixed within a Circular CAM Track 22. Said Circular CAM Track 22, is milled within the inner Deck Plate 1, and Outer Deck 2a Collar 45. Said Circular Cam Bushings 21, preferably being manufactured from compressible polymer material, can accommodate lubricity, substantial lateral loads through 360 degrees of horizontal axis in vertical rotation, and multi axis loads in torsion and compression, to distribute said impact loads more evenly through the full circumference of the SPDU assembly. Further the Circular Cam Bushing 21, is 25 preferably drilled with Lightening Holes 24, to reduce the weight of the overall assembly and aid in compression. Said Circular CAM Track 22, being punctuated by a plurality of Clean-Out Holes 24, which serve to allow exit of the dust and debris to the aircraft floor well below, whenever the SPDU assembly is in circular motion about the vertical axis. Said function of dust and debris removal being 3o achieved by the motion of the Cam Followers 23, pushing in either clockwise or counter-clockwise fashion the plurality of Circular Cam Bushing 21, means.
Said Circular Cam Bushing 21, means being manufactured in a manner as to create Bushing Cleanout Angles 26, which in turn push said dust and debris to, and through the Clean-Out Holes 24. For maintenance purposes, the preferred embodiment of the present invention is also equipped with a plurality of Cam Follower Insertion Holes 27, for the purpose of removing and inserting Cam Followers 23. Said Circular Cam Bushing 21, means being integrated as a sub assembly within, and sandwiched between the Inner Deck Plate 1, and the Outer s Deck Collar 45 to effect lubricity, self cleaning, and to absorb multi-axis loads imposed on the overall SPDU assembly through normal operation of the SPDU.

As depicted in Figures 1 tftrough 7, the preferred embodiment of the present invention incorporates a multi axis load absorbing, and load transfer to assembly which accommodates horizontal lateral axis A, longitudinal axis B, vertical axis C, and non-symmetrical tangential axis D forces. Said absorption and load transfer being initiated by various load moments emanating from the pallet assemblies as they pass over, or impact, with the Flexible Drive Wheel 9, and are transferred to the MDU Mounting Plate 4, and in turn are transferred to the Multi s s Axis MDU Frame 41, Said Multi Axis MDU Frame 41, providing a mounting support for the MDU Mounting Plate 4, through two opposing MDU Frame Member 54, means, drilled with a plurality of MDU Frame Mounting Hole 53, means, and secured by a plurality of MDU Frame Drive Mounting Bolts 42, means. Said Multi Axis MDU Frame 41, assembly transfers said loading to a Spring Assembly 46, 2o mounted at one end of the Multi Axis MDU Frame 41, and to an MDU Frame Bushing Assembly 43, mounted at the opposite end of the Multi Axis MDU Frame 4. Said Spring Assembly 46, being comprised of a Spring 47, which receives the forces exerted upon it from the Multi Axis MDU Frame 41, and translates said moments into lineal movement of a Spring Compression Collar 49, over the length 25 of the long axis of the Spring Rod 48, which, in turn effects compression and release of the Spring 47. The various off-axis tangential and torsion loads transferred to the Spring Assembly 46, are absorbed by a Spring Ball Joint 50, recessed within a Spring Spherical Washer Plate 51. Said Spring Assembly 46, preferably being used in plurality and constrained to effect lineal movement by a 3o pair of MDU Frame Spring Mount Hole 52, means which permit the Multi Axis MDU
Frame 41, Spring Compression Collar 49, Spring 47, assemblies to move in a lineal fashion over the length of the long axis of the Spring Rod 48, regardless of the angle of the load path being absorbed.

Further, the preferred embodiment of the present invention accommodates the vertical forces, and in particular off axis torsion and longitudinal compression forces acting upon the overall assembly of the Multi Axis MDU Frame 41, by means of a flexible polymer MDU Frame Bushing Assembly 43, comprised of an MDU
Frame Bushing Mounting Bolt 44, with a plurality of Bushing Washer 56, means located within the converging axis of a single MDU Frame Pivot Point 55, affixed to one end of the Multi Axis MDU Frame 41, assembly. Said bushing means accommodates said lateral, vertical, longitudinal, and tangent loads through all axis imposed on the Multi Axis MDU Frame 41. Other means of accommodating said to dynamic loads at one pivot point on the Multi Axis MDU Frame 41, have also been contemplated including a polymer ball joint and socket assembly to achieve the same function as the MDU Frame Bushing Assembly 43, disclosed herein. Said, vertical, longitudinal, and tangent loads being mitigated by the Spring Assembly 46, and the MDU Frame Bushing Assembly 43, with excess loads being transferred ~ 5 through the structurally reinforced Inner Deck Plate 1, to the Outer Deck Collar 45, and to the aircraft floor structure, without the use of a load bearing canister or external housing.
CONTROL UNIT ASSEMBLY
2o As depicted in Figures 1 through 3, and 5, the preferred embodiment of the present invention further incorporates a control unit assembly means to effect operator tasking and automated response actions to undertake utilization of the present invention and to prevent damage from faulty installation or dynamic inputs beyond the normal response range of the current invention. Said control unit 25 assembly consisting of an Aircraft Control Power & Data Interface 61, typical to those skilled in the art of aircraft data and power control cable assemblies and preferably integrating either threaded of quick disconnect means to undertake rapid installation and removal of the SPDU cable assembly. Said Aircraft Control Power & Data Interface 61, being connected to the aircraft cargo operator SPDU
control 3o panel and a Control Module 62, mounted to the structurally reinforced webbing of the Inner Deck Plate 1. Said Control Module 62, effecting two way command responses to a Magnetic Reader 63, and an Optical Encoder 67, for the purpose of controlling steerout, and to further effect indexing of the Reduction Gear Assembly 8. Said Optical Encoder 67, being equipped with an Optical Encoder Adjustment Knob 70, to manually recalibrate the encoder. Said control and response commands being passed to the DC Brushless Motor/Harmonic Drive Assembly 3 means, and various other electrically actuated components by means of a Control & Power Cable 64, harness.
Said Magnetic Reader 63, being used to detect a plurality of Ferrous Pin 66, means located at either end of the Reduction Gear Assembly 8, to prevent streerout. Further, the Control Module 62, is protected from adverse impact during installation and operation by a localized Control Module Shield 69. Further a localized Aircraft Interface Shield 68, protects the Aircraft Control Power &
Data 1o Interface 61, from adverse impact during installation and operation.
While preferred embodiments have been shown and described, various substitutions and modifications may be made without departing from the spirit and scope of the invention. Accordingly it is to be understood that the present invention has been described by way of illustration and not limitation.
~5

Claims (22)

1. An integrated assembly of articulating components which together constitute a means to convey aircraft cargo pallets and containers by means of a Steerable, Powered, Drive Unit, which translates in the vertical and horizontal axis, and provides a passive impact and load response system which transfers dynamic multi axis loads to a single structurally reinforced deck plate without using a structural load absorbing canister or housing mounted below the cargo deck of an aircraft, comprising;

a) a motor drive unit; and, b) a motor drive unit mounting frame; and, c) a multi axis load absorbing spring assembly; and, d) a cleanout assembly and, e) a multi axis load absorbing compressible bushing assembly; and, f) a magnetic reader; and, g) an optical encoder; and, h) a calibration knob; and, i) a control module; and, j) a motor drive unit mounting bracket; and, k) a circular bushing assembly; and, l) a reduction gear assembly; and, m) a structurally reinforced deck plate.

2. The apparatus of Claim 1, wherein said aircraft is a fixed or rotary wing aircraft.

3. The apparatus of Claim 1, wherein said motor drive unit incorporates a DC
brushless motor and harmonic drive.

4. The apparatus of Claim 1, wherein said motor drive incorporates a disengaging clutch assembly.

5. The apparatus of Claim 1, wherein said motor drive incorporates a rotationally actuated flexible rubber friction wheel surface to engage cargo pallets.

6. The apparatus of Claim 1, wherein said motor drive unit incorporates an impact load deflecting chamfered wheel mounting bracket.

7. The apparatus of Claim 1, wherein said motor drive unit mounting frame is pivotally attached at one end to a multi axis load absorbing bushing, and affixed to a multi axis load absorbing spring assembly at the other end.

8. The apparatus of Claim 6, wherein said motor drive unit mounting frame is mechanically fastened to said motor drive unit chamfered brackets in the center and between the two frame members, of said motor drive unit mounting frame.

9. The apparatus of Claim 1, wherein said multi axis load absorbing spring assembly incorporates a spring rod affixed to said load transfer, structurally reinforced deck plate at one end of the rod and spring assembly only, and being connected to nothing at the opposite end.

10. The apparatus of Claim 9, wherein said multi axis load absorbing spring assembly incorporates a ball joint on at least one end of the spring rod.

11. The apparatus of Claim 9, wherein said ball joint incorporates a spring spherical washer plate.

12. The apparatus of Claim 1, wherein said multi axis load absorbing spring assembly passes through said multi axis load transfer frame at one end of the spring only

13. The apparatus of Claim 1, wherein said cleanout assembly is comprised of plurality of circular polymer or other compressible bushings

14. The apparatus of Claim 13, wherein said clean out assembly polymer bushing is cut at an angle as to facilitate collection and forced removal of dust and debris around a cam track.

15. The apparatus of Claim 14, wherein said cleanout assembly incorporates clean out holes which permit dust and debris to fall clear of the SPDU assembly.

16. The apparatus of Claim 1, wherein said cleanout assembly incorporates cam followers and a cam track,

17. The apparatus of Claim 1, wherein said multi axis load absorbing compressible bushing assembly, comprises a cylindrical, compressible main polymer bushing.

18. The apparatus of Claim 1, wherein said control module incorporates a magnetic reader and ferrous metal pins set at predefined degree increments in azimuth around the underside of the structurally reinforced deck plate to activate said magnetic reader.

19. The apparatus of Claim 1, wherein said control module comprises a microprocessor, and power data interface cables.

20. The apparatus of Claim 1, wherein said optical encoder includes an adjustment knob for manual calibration of the SPDU

21. The apparatus of Claim 1, wherein said structurally reinforced deck plate assembly accommodates a plurality of reduction gears.

22. The apparatus of Claim 1, wherein said structurally reinforced deck plate assembly accommodates the mounting and load transfer of all components of the present invention.

DRAWING KEY
MOTOR DRIVE UNIT (MDU) ASSEMBLY
Inner Deck Plate 1, Retractable Lifting Handles 2, DC Brushless Motor/Harmonic Drive Assembly 3.
MDU Mounting Plate 4, Wheel Mounting Frame Chamfered Edge 5, Gear Rack 6, Pinion/Gear Assembly 7, Reduction Gear Assembly 8, Flexible Drive Wheel 9, Mechanical Clutch Assembly 10, ROTATIONAL BUSHING ASSEMBLY
Circular Cam Bushing 21, Circular CAM Track 22, Cam Followers 23, Clean-Out Holes 24, Bushing Lightening Holes 25, Bushing Cleanout Angles 26, Cam Follower Insertion Holes 27, Aircraft Mounting Brackets 28, MDU MOUNTING & LOAD TRANSFER ASSEMBLY
Multi Axis MDU Frame 41, MDU Frame Drive Mounting Bolts 42, MDU Frame Bushing Assembly 43, MDU Frame Bushing Mounting Bolt 44, Outer Deck Collar 45, Spring Assembly 46, Spring 47, Spring Rod 48, Spring Compression Collar 49, Spring Ball Joint 50, Spring Spherical Washer Plate 51, MDU Frame Spring Mount Hole 52, MDU Frame Mounting Hole 53, MDU Frame Member 54, MDU Frame Pivot Point 55, Bushing Washer 56, CONTROL UNIT ASSEMBLY
Aircraft Control Power & Data Interface 61, Control Module 62, Magnetic Reader 63, Control & Power Cable 64, Ferrous Pin 66, Optical Encoder 67, Aircraft Interface Shield 68, Control Module Shield 69, Optical Encoder Adjustment Knob 70,