Conveyors: power-driven – Conveyor section – Live roll
Reexamination Certificate
2003-05-28
2004-12-28
Valenza, Joseph (Department: 3651)
Conveyors: power-driven
Conveyor section
Live roll
C198S722000, C244S137100
Reexamination Certificate
active
06834758
ABSTRACT:
RELATED APPLICATION
This application claims priority to United Kingdom Patent Application Number 0212354.5, filed May 29, 2002.
TECHNICAL FIELD
The present invention relates to a power drive unit for cargo handling systems, particularly drive units for use in a cargo handling system in the cargo compartment of an aircraft.
BACKGROUND ART
Conventional Power Drive Units (PDUs) include rotationally driven rollers which can be raised through an aperture in a deck panel of the cargo compartment frictionally to engage the under-surface of a cargo unit, conventionally a Unit Load Device (ULD) to move the ULD within the cargo compartment. It would be understood however that such PDUs can be used to handle ULDs and other cargo units in cargo handling systems external to the cargo compartment of an aircraft or other vehicle or vessel.
In the accompanying drawings
FIG. 1
is a cross-sectional representation of a conventional PDU. The conventional PDU includes a rigid metallic frame
11
pivotally mounted at
12
to a chassis (not shown in
FIG. 1
) rigidly secured beneath a deck panel of the floor or deck of a cargo compartment. The axis
13
of pivotal movement of the frame
11
relative to the chassis is parallel to, and spaced below, the plane of the deck panel. Adjacent its end remote from the pivot axis
13
, the frame
11
rotatably supports a roller assembly
14
for rotation about an axis
15
parallel to the axis
13
. The roller assembly is disposed in alignment with an aperture in the deck panel and in a rest position of the frame
11
relative to the deck panel rubber tyred rollers
15
a
of the roller assembly
14
lie just beneath the plane of an array of Ball Transfer Units (BTUs) carried on the upper surface of the deck panel to provide a low friction support for a ULD on the deck panel. There is provided an arrangement for raising the PDU by pivoting the frame
11
about the axis
13
to raise the periphery of the rollers
15
a
through the aperture in the deck panel to engage the under-surface of a ULD seated on the BTUs.
Mounted within the frame
11
is an electric drive motor
16
the rotor shaft
17
of which is equipped, at one end of the shaft
17
, with an electro-magnetically operable brake assembly
18
. The brake assembly
18
when operative brakes the shaft
17
of the motor against rotation.
The opposite end of the shaft
17
from the brake
18
is equipped with a small diameter pinion gear wheel
19
which meshes with the teeth of a large diameter internal gear wheel
21
mounted to the frame
11
for rotation about an axis parallel to the axes of the shaft
17
and roller assembly
14
. A shaft
22
extending from the gear wheel
21
and rotatable therewith is formed with a small diameter pinion gear wheel
23
meshing with a larger diameter gear wheel
24
on a shaft
25
mounted to the frame for rotation about an axis co-extensive with the axis of rotation of the shaft
17
. A train of gears
43
,
44
,
45
all rotatable about parallel axes transmit drive from the gear wheel
24
to a shaft
46
carrying the gear wheel
45
. The shaft
46
carries the axially aligned rollers
15
a
for rotation therewith about the axis
15
, the shaft
46
being journalled at its opposite axial ends respectively in bearings on the frame
11
for rotation relative thereto, and the gear wheel
45
being disposed adjacent the mid-point of the length of the shaft
46
between the rollers
15
a
. It will be recognised therefore that when the brake
18
is de-energised to release the shaft
17
and the motor
16
is energised then the motor
16
drives the rollers
15
a
for rotation in unison about their common rotational axis
15
.
The end of the shaft
25
remote from the motor
16
is coupled to an axially co-extensive drive shaft
26
through the intermediary of a torque limiting device
27
and an electro-magnetically operable clutch
28
. A small diameter pinion gear wheel
29
on the shaft
26
meshes with a larger diameter gear wheel
31
on a shaft
32
parallel to the shaft
26
. A smaller diameter gear wheel
33
on the shaft
32
drives a larger diameter gear wheel
34
driving a co-axial gear wheel
35
meshing with a gear wheel
36
on the end of a cam shaft
37
journalled for rotation in the frame
11
. The cam shaft
37
extends the full width of the frame
11
and adjacent its opposite axial ends respectively carries first and second cams
38
which cooperate with fixed cam followers on the chassis of the PDU whereby angular movement of the shaft
37
about its longitudinal axis lifts and lowers the frame
11
about the axis
13
by virtue of the cam action between the cams
38
and the cam followers on the chassis.
The operation of the conventional PDU illustrated in
FIG. 1
is as follows. Let us assume firstly that the brake
18
is operative, the clutch
28
and the motor
16
are de-energised, and the cam shaft
37
is in a rotated position such that the frame
11
is collapsed into its rest position below the level of the deck panel. In order to raise the rollers
15
a
through the aperture in the deck panel to engage a ULD, power is supplied to the motor
16
and at the same time the brake
18
is de-energised so that the shaft
17
is released for rotation. Simultaneously power is applied to the electromagnetic clutch
28
so that the clutch is engaged and rotational movement of the shaft
17
is transmitted through the torque limiter
27
and the engaged clutch
28
to the shaft
26
.
Simultaneously rotational movement of the motor shaft
17
is transmitted through the gear train
24
,
43
,
44
,
45
to the rollers
15
a
to rotate the rollers
15
a
about their axis
15
.
Rotation of the shaft
26
drives the shaft
37
through the step-down gear train
29
,
31
,
33
,
34
,
35
,
36
interconnecting the shafts
26
and
37
. The shaft
37
is thus moved angularly about its longitudinal axis causing the cams
38
to cooperate with the chassis and thus raise the frame
11
relative to the deck panel about the axis
13
. The periphery of the rollers
15
a
is thus caused to project upwardly through the aperture in the deck panel so as frictionally to engage the under-surface of a ULD supported on the deck panel. As the rollers
15
a
are being rotated by the motor
16
the ULD will be moved relative to the deck panel.
It will be noted that the roller assembly
14
includes a rubber tyred wheel
39
mounted for rotation about the axis
15
and having an outer diameter similar to the outer diameter of the rollers
15
a
. The wheel
39
engages the under-surface of a ULD at the same time that it is engaged by the rollers
15
a
. However, the wheel
39
is not driven with the rollers
15
a
and thus can detect slip between the rollers
15
a
and ULD since in such a situation the rollers
15
a
will continue to rotate but the wheel
39
will be stationary, or moving at a different speed, by virtue of its engagement with the ULD. A slip sensor detects any difference in the rotational speeds of the wheel
39
and the rollers
15
a
and either provides warning of slippage or alternatively de-energises the motor.
When the engagement between the cams
38
and the cam followers reaches its highest point (corresponding to the maximum lift position of the frame
11
) the cams
38
engage stops which prevent further rotation of the shaft
37
. Thus the gear train and the shaft
26
become stalled since the shaft
37
cannot rotate any further, and the torque limiting device
27
slips so that the motor
16
can continue to operate and to drive the rollers
15
a
notwithstanding that the shaft
37
is now held against further rotation. It will be recognised that energy is dissipated within the torque limiting device
27
as the device
27
slips throughout the whole of the time that the rollers
15
are rotated in their fully raised position.
In the event that the rollers
15
a
are subjected to a shock loading in a vertical direction then they can be depressed relative to the deck to accommodate such a shock loading by reverse rotation of the cams
38
and t
Gavino William A
Issakhanian Edmond
Larson Richard
Morse John E
Nguyen Frank H
Goodrich Corporation
Valenza Joseph
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