Load Sharing Handrail Drive Apparatus
BACKGROUND
FIELD OF INVENTION
[0001] The present invention relates generally to handrail drive
apparatuses, and more particularly, to linear handrail drive
apparatuses typically used in conjunction with moving walkways,
travelators, escalators, and the like.
DISCUSSION OF RELATED ART
[0002] Linear handrail drives have existed for many years. Such
handrail drives were developed to elevate handrails entirely
above the step band of a moving walkway and/or escalator and
thereby avoid routing the handrail down into the truss to be
driven directly by the same elements arranged to drive the step
band. Notwithstanding the advantages that arise from this
configuration, known linear handrail drives have been fraught
with problems such as difficulty in effecting adjustment, lack
of reliability, capacity limitations, the inability to
incorporate special handrails, and relatively rapid
deterioration.
[0003] FIG. 1A depicts one example of a traditional linear
handrail drive apparatus 10. The handrail drive apparatus 10
includes a plurality of driving wheel members 12 arranged to
drive a handrail 14. Each of the driving wheel members 12
includes an input portion 12a and an output portion 12b. The
input portions 12a of each of the driving wheel members 12 are
connected with one another via a connecting member 16 such as,
for example, a chain or belt or the like. A drive motor 18 is
coupled to the input portion 12a of at least one of the driving-
wheel members 12 via an input connecting member 16a. The
handrail 14 is forced against the output portion 12b of each

driving wheel member 12 by a respective pinch roller 20
positioned on an opposite side of the handrail 14. In
operation, the drive motor 18 drives one of the driving wheel
members 12 which, in turn, drives another driving wheel member
12 via connecting member 16 at substantially the same angular
velocity. As a result, the output portions 12b of each driving
wheel member 12 drive the handrail 14 to move. When the
structural attributes of all of the foregoing members in the
handrail drive apparatus 10 are equal (e.g., the diameter and
hardness of each of the driving wheel members 12 are equal; the
pinch force applied to the handrail 14 by each pinch roller 20
is equal), and the angular velocities of members 12 are equal,
the linear velocity of the output portion 12b of each driving
wheel member 12 will also be equal. Consequently, the linear
velocity imparted to the handrail 14 by each of the driving
wheel members 12 is equal since the rolling radii of the driving
wheel members 12 are equal.
[0004] Generally, however, the respective driving wheel members 12
are not equal in all respects due to various differences and
defects inherent in standard manufacturing processes. For
example, the output portion 12b of one or more driving wheel
members 12 may not be completely round or may have a diameter
that differs slightly from one or more of the other driving
wheel members 12. As another example, one or more driving wheel
members 12 may have different hardnesses and/or the pinch force
applied to the handrail 14 by each respective pinch roller 20
may not be consistent. Any of the foregoing differences can
effectively create differing rolling radii in each of the
driving wheel members 12. As shown in FIG. 1A, for example, the
rolling radii of the respective output portions 12b of the
driving wheel members 12 may not be equal to one another and, as
a result, the output portion 12b having the smaller radius will
attempt to drive the handrail 14 at a slower linear velocity

than the output portion 12b having the larger radius. Where the
driving wheel members 12 attempt to drive the handrail 14 at
different linear velocities, slipping or scrubbing of some or
all of the driving wheel members 12 against the handrail 14 must
occur for the handrail 14 to move. As one of ordinary skill in
the art will recognize, operation involving slipping/scrubbing
introduces inefficiencies related to dynamic friction
coefficients, whereas operation under pure rolling conditions
takes advantage of more efficient static friction coefficients.
The end result is an inefficient drive apparatus with high wear,
increased debris generation, and reduced capacity due to
imperfect operating conditions.
[0005] One attempt to alleviate the inefficiencies in traditional
linear handrail drives is depicted in FIG. lB, which shows a
linear handrail drive apparatus 22 including a handrail 23, a
drive motor 24, an input connecting member 26, a primary driving
wheel member 28, at least one secondary driving wheel member 32,
a connecting member 30, and a plurality of pinch rollers 34.
The drive motor 24 is drivably coupled to an input portion 28a
of the primary driving wheel member 28 via the input connecting
member 2 6 which may be, for example, a chain or belt or the
like. An output portion 28b of the primary driving wheel member
28 is coupled to the at least one secondary driving wheel
members 3 2 via a connecting member 3 0 which may be, for example,
a chain, a poly vee or cogged belt configured to engage the
handrail 23. The plurality of pinch rollers 34 are positioned
opposite the primary and secondary driving wheel members 32 to
force contact between the handrail 23 and connecting member 30
and thereby impart motion to the handrail 23. While this
configuration offers some improvement to the above-described
inefficiencies associated with traditional linear handrail
drives, it also has inherent shortcomings. For example, since
the linear stiffness of the connecting member 30 is typically

far less than the linear stiffness of the handrail 23, the
majority of driving force imparted to the handrail 23 occurs at
the first pinch location (i.e., at the primary driving wheel
member 28) since the driving force at downstream pinch locations
is limited by the small stretch of the handrail 23 compared to
the required stretch of the connecting member 30 between pinch
locations to assume load. Thus, most of the load is taken on by
the connecting member 3 0 and primary driving wheel member 2 8 at
the first pinch location as long as, or until, the connecting
member 3 0 becomes unable to drive the handrail 23 by itself at
the first pinch location, at which time the handrail 23 slips
relative to the connecting member 30, allowing stretch of the
connecting member 30 and, in turn, allowing load to be
transferred to the next pinch location (i.e., at the adjacent
secondary driving wheel member 32) . This slipping and loading
cascade continues until equilibrium occurs and the handrail 23
is in motion. Thus, as long as the connecting member 3 0 is not
able to drive the handrail 23 by itself at the first pinch
location, small but continuous slipping occurs at sequential
pinch locations depending on the driving force/load requirements
of the handrail 23. The result is much the same as the
aforementioned traditional linear handrail drives in that the
apparatus causes wear of the handrail and connecting member,
debris generation, and has diminished capacity due to slipping
(dynamic friction coefficients) existing at most of the pinch
locations.
SUMMARY
[0006] The invention is directed to a new and improved handrail
drive apparatus that remedies the problems associated with past
linear handrail drives and provides load sharing between drive
wheel assemblies to reduce wear, improve efficiency of the drive
apparatus by eliminating fighting and slipping between the

handrail and drive wheel assemblies, and improve drive capacity
by operating with static rather than dynamic coefficients of
friction.
[0007] In one embodiment of the invention, a handrail drive
apparatus is provided comprising a first drive wheel assembly
configured to drive a handrail and comprising a planetary gear
train arranged to be driven by a first driving member. The
handrail drive apparatus further comprises a second drive wheel
assembly configured to drive the handrail, the second drive
wheel assembly being coupled to the planetary gear train of the
first handrail drive wheel assembly by a second driving member.
The planetary gear train of the first handrail drive wheel
assembly is configured to divide a torque imparted by the first
driving member between at least the first and second drive wheel
assemblies.
[0008] The planetary gear train of the first drive wheel assembly
comprises a sun gear member, a planet carrier, a ring gear
member, and at least one planet gear. The sun gear member is
rotatably arranged about a first axis and includes an output
portion arranged to contact and drive the handrail. The planet
carrier and the ring gear member are also rotatably arranged
about the first axis. The at least one planet gear is coupled
to the planet carrier and meshes with the sun gear and the ring
gear. The at least one planet gear is arranged to rotate about
a second axis extending substantially parallel to the first
axis. The at least one planet gear divides the torque imparted
by the first driving member to the planet carrier between the
sun gear member and the ring gear member.
[0009] In another embodiment of the handrail drive apparatus, the
at least one planet gear is a compound planet gear having a
first portion arranged to mesh with the sun gear and a second
portion arranged to mesh with the ring gear, the first and
second portions of the compound planet gear having different

diameters such as, for example, the diameter of the first
portion of the compound planet gear being smaller than the
diameter of the second portion of the compound planet gear.
[00010] In another embodiment of the invention, a handrail drive
apparatus is provided comprising a first driving wheel member
arranged to drive a handrail and a second wheel drive member
coupled in parallel with the first driving wheel member to drive
the handrail. The handrail drive apparatus further comprises
means for dividing a torque required to drive the handrail
between at least the first and second driving wheel members.
[00011] In still another embodiment of the invention, the handrail
drive apparatus comprises a plurality of pinch rollers, each
pinch roller being arranged opposite one of the first and second
drive wheel assemblies to force the handrail against a drive
surface of the first and second drive wheel assemblies. The
plurality of pinch rollers are coupled to one another such that
each pinch roller applies equal force to the handrail. A
tensioned cable couples each of the plurality of pinch rollers
to one another, the cable having a first end adjustably secured
to a frame of the apparatus and a second end fixedly secured to
the frame of the apparatus. Each of the plurality of pinch
rollers comprises at least one pulley arranged to receive the
cable such that tension in the cable forces the pinch roller
against the handrail in a direction substantially normal to a
direction of movement of the handrail. At the first end of the
cable, an adjustment mechanism is provided which includes a
threaded end attached to a nut and a compression spring provided
between the nut and the frame to provide adjustable tension in
the cable. Alternatively, the cable is adjustably secured to
the frame at a first point along its length and is fixedly
secured to the frame at a second point along its length. The
adjustment mechanism may also include a pulley over which the
cable passes at the first point along its length such that the

cable extends along both sides of each pinch roller assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
[00012] Examples for some embodiments of the invention will be
described with respect to the following drawings, in which like
reference numerals represent like features throughout the
figures, and in which:
[00013] FIG. 1A is a schematic side view of a known linear handrail
drive apparatus;
[00014] FIG. 1B is a schematic side view of another known linear
handrail drive apparatus;
[00015] FIG. 2 is a schematic side view of a handrail drive
apparatus according to an embodiment of the invention;
[00016] FIG. 3A is a schematic side view of a handrail drive
apparatus according to another embodiment of the invention;
[00017] FIG. 3B is a schematic cross-sectional view of an
embodiment of a handrail drive wheel assembly taken through line
"3B-3B in FIG. 3A;
[00018] FIG. 3C is a schematic cross-sectional view of another
embodiment of a handrail drive wheel assembly taken through line
3C-3C in FIG. 3A;
[00019] FIG. 3D is a schematic cross-sectional view of another
embodiment of a handrail drive wheel assembly taken through line
3D-3D in FIG. 3A;
[00020] FIG. 4 is a detailed schematic cross-sectional view of the
planetary gear train in the handrail drive wheel assembly
depicted in FIG. 3B;
[00021] FIGS. 5A and 5B are schematic front and side views of
another embodiment of a planetary gear train having a compound
planet gear according to the handrail drive wheel assembly shown
in FIG. 3C;
[00022] FIG. 6 is a schematic side view of a pinch roller system
having an adjustable pinch force equalizer according to an

embodiment of the invention; and
[00023] FIG. 7 is a schematic view of a handrail drive apparatus
utilizing individual hydraulic motors to drive handrail drive
members according to another embodiment of the invention.
DETAILED DESCRIPTION
[00024] In describing the embodiments illustrated in the drawings,
specific terminology is employed for the sake of clarity.
However, the invention is not intended to be limited to the
specific terminology so selected. It is to be understood that
each specific element includes all technical equivalents that
operate in a similar manner to accomplish a similar purpose.
[00025] In the following description of certain embodiments of the
invention, directional words such as "top," "bottom,"
"upwardly," and "downwardly" are employed by way of description
and not limitation with respect to the orientation of the power
generator unit and its various components as illustrated in the
drawings. Similarly, directional words such as "axial" and
"radial" are also employed by way of description and not
limitation.
[00026] FIG. 2 is a schematic side view of a handrail drive
apparatus 40 according to an embodiment of the invention. The
handrail drive apparatus 40 is configured to drive a handrail 42
and includes a first drive wheel assembly 50 drivably coupled to
a second drive wheel assembly 41 via a first drive member 48,
which may be a belt or a chain or the like. In the embodiment
shown in FIG. 2, the first drive wheel assembly 50 is drivably
coupled to a drive motor 44 via an input drive member 46, which
may be a belt or a chain or the like. The first drive wheel
assembly 50 includes a planetary gear train for dividing a
torque imparted by the input drive member 4 6 between the first
drive wheel assembly 50 and the second drive wheel assembly 41
so that the drive wheel assemblies drive the handrail 42 in a

parallel fashion. The planetary gear train of the first drive
wheel assembly 50 is discussed in further detail below with
reference to FIGS. 3A, 3C, and 5. Briefly, however, the
planetary gear train schematically depicted in FIG. 2 is
arranged rotatably about an axis A and includes a sun gear
member 56, a planet carrier 52, a ring gear member 58, and at
least one planet gear 54, 55. The planetary gear train
functions to divide the torque between the sun gear member 56,
which directly drives the handrail 42 at an output portion 60,
and the ring gear member 58, which passes on the divided portion
of the torque to the second drive wheel assembly 41 via first
drive member 48. One of ordinary skill in the art will
recognize that although two planet gears 54, 55, are included in
the embodiment shown in FIG. 2, any number of planet gears can
be used including one or more planet gears.
[00027] The second drive wheel assembly 41, as shown in the
embodiment depicted in FIG. 2, is a unitary member 45 rotatably
arranged about axis A'. The second drive wheel assembly 41
includes an input portion 43 for receiving torque input imparted
by the first drive member 4 8 and an output portion 47 for
contacting and driving the handrail 42 (see FIG. 3D). In the
embodiment shown in FIG. 2, a plurality of pinch rollers 62 are
also provided opposite the first and second drive wheel
assemblies 50, 41, to force the handrail 42 against the output
portions 60, 47 of the first and second drive wheel assemblies
50, 41 in a direction normal to the direction in which handrail
42 is driven.
[00028] FIG. 3A is a schematic side view of the handrail drive
apparatus 40 according to another embodiment of the invention.
The handrail drive apparatus 40 in the embodiment depicted in
FIG. 3A is substantially the same as that described above and
depicted in FIG. 2, except that an additional drive wheel
assembly 50A is disposed between the drive motor 44 and the

first drive wheel assembly 50. In the embodiment depicted in
FIG. 3A, the drive wheel assemblies 50A, 50, and 41 are driven
in a parallel fashion rather than the series fashion of past
linear handrail drives. Each of the drive wheel assemblies 50A,
50 includes a planetary gear train for torque splitting and
angular velocity compensation. As in FIG. 2, the second drive
wheel assembly 41 is a unitary member 45 having input and output
portions 43 and 47, respectively. The torque is divided by the
planetary gear trains of the drive wheel assemblies 50A, 50
based on the number of drive wheel assemblies in the apparatus
as well as the gear ratios within the planetary gear trains.
FIGS. 3B, 3C, and 3D are schematic cross-sectional views of the
handrail drive wheel assemblies according to the embodiment
shown in FIG. 3A taken through lines 3B-3B, 3C-3C, and 3D-3D,
respectively.
[00029] Referring to FIGS. 3A and 3B, the additional drive wheel
assembly 50A is arranged rotatably about an axis A'' relative to
a support frame F and comprises a sun gear member 56A, a planet
carrier 52A, a ring gear member 58A, and at least one planet
gear 54A, 55A. FIG. 4, discussed further below, shows the
planetary gear train of the additional drive wheel assembly 50A
in further detail. In operation, the planet carrier 52A
receives torque from the drive motor 44 via input drive member
46. Planet gears 54A, 55A are rotatably disposed on shafts 57A
of the planet carrier 52A. A toothed outer surface of the
planet gears 54A, 55A is meshed with a toothed outer surface of
sun gear member 56A at meshing zone 53A and with a toothed inner
surface of ring gear member 58A at meshing zone 51A. By virtue
of the planet gears 54A, 55A, the torque input to the planet
carrier 52A is divided between the sun gear member 56A, which
directly drives the handrail 42 at an output portion 60A, and
the ring gear member 5SA, which passes on the divided portion of
the torque to the first drive wheel assembly 50 via drive member

48A. The planetary gear train of the additional drive wheel
assembly 50A divides the torque input from the drive motor 44
such that a smaller portion of the torque is delivered directly
to the sun gear member 56A by the planet gears 54A, 55A at
meshing zone 53A. The remaining larger portion of the torque is
passed to the ring gear member 58A by the planet gears 54A, 55A
at meshing zone 51A. The larger and smaller torque portions are
based on the moment arms defined by the ring gear member 58A and
the sun gear member 56A, respectively. The larger portion of
the torque output is, in turn, transferred/outputted to the next
sequential drive wheel assembly such as, for example, first
drive wheel assembly 50, via drive member 4 8A which may be a
chain, a belt or the like. Thus, in the embodiment depicted in
FIG. 3A, torque output from the ring gear member 58A becomes the
torque input to the planet carrier 52 in the first drive wheel
assembly 50. This mechanical torque splitting/sharing process
is repeated from one drive wheel assembly to the next until
second drive wheel assembly 41 is reached. The second drive
wheel assembly 41 simply receives the remaining torque from the
first drive wheel assembly 50 without a need to pass on a share.
[00030] FIGS. 3A, 3C, 5A, and 5B schematically depict aspects of
the planetary gear train of the first drive wheel assembly 50
according to an embodiment of the invention. The planetary gear
train of first drive wheel assembly 50 is arranged rotatably
about axis A relative to a support frame F and includes sun gear
member 56, planet carrier 52, ring gear member 58, and at least
one planet gear 54, 55. Planet gears 54, 55 are rotatably
disposed on shafts 57 of the planet carrier 52. In the
embodiment depicted in FIG. 3A, first drive wheel assembly 50 is
operably coupled to the additional drive wheel assembly 50A via
drive member 48A and to the second drive wheel assembly 41 via
drive member 48. Because second drive wheel assembly 41 is the
last drive wheel assembly in the apparatus it does not have a

planetary gear train. Therefore, in order for first drive wheel
assembly 50 to divide the torque input thereto exactly equally
between itself and the second drive wheel assembly 41, the
diameters of the sun and ring gear members would, in theory, be
equal. In this case, the diameter of the planet gears would
necessarily be zero. This, obviously, is not possible. The
best torque division using a planetary gear train wherein the
planet gears have one toothed surface with a single pitch
diameter configured to mesh with both the sun and ring gear
members (see, for example, FIG. 3B) , would be about a 45-55
percentage split. However, as shown in FIG. 3C, by providing a
compound planet gear 54, 55, a nearly ideal 50-50 division of
the torque is achievable. The compound planet gear 54, 55 is
depicted in the schematic views of the embodiments shown in
FIGS. 3C, 5A, and 5B, and includes two distinct toothed surfaces
having different pitch diameters. In FIG. 3C, a first of the
two toothed surfaces of each of the planet gears 54, 55 is
arranged to mesh with the ring gear 58 at zone 51 and a second
of the two toothed surfaces of each of the planet gears 54, 55
is arranged to mesh with the sun gear member 56 at zone 53 at a
radially outward end of radial extension 59.
[00031] In the handrail drive apparatus 40 depicted in the
embodiment of FIG. 3A, which includes three drive wheel
assemblies 50A, 50, and 41, the gearing in the additional drive
wheel assembly 50A is selected to provide a torque division with
approximately one-third of the torque delivered to the sun gear
member 56A while the remaining two-thirds of the torque is
passed on to the planet carrier 52 of the first drive wheel
assembly 50. In the first drive wheel assembly 50, the
planetary gear train is configured to divide the remaining two-
thirds torque share substantially equally between the sun gear
member 56 and the ring gear member 58, so that all three drive
wheel assemblies 50A, 50, 41 assume approximately one-third of

the total drive torque and load. As will be apparent to one
having ordinary skill in the art, the handrail drive apparatus
40 can include any number of drive wheel assemblies such as, for
example, two (e.g., FIG. 2), three (e.g., FIG. 3A) , or four
drive wheel assemblies (not shown) and so on, wherein the torque
is divided substantially equally among the drive wheel
assemblies.
[00032] If all the drive parameters (e.g., structural dimensions,
hardness, and pinch wheel force) and angular velocities are
perfectly equal in each of the drive v/heel assemblies 50A, 50,
41, the handrail drive apparatus 4 0 would operate to equally
divide the drive torque between the drive wheel assemblies 50,
50A, 41, according to the gear ratios within the planetary gear
train of each respective drive wheel assembly without any
internal movement of the planet gears 54, 55 (54A, 55A) because
the rolling radii of all the drive wheel assemblies would be
equal. However, because the drive parameters of such
apparatuses typically vary from perfection, there are normally
differences in rolling radii between the drive wheel assemblies
50, 50A, 41. As a result, the planet gears 54, 55 (54A, 55A)
move internally as necessary to compensate for the rolling radii
differences and, consequently, alter the angular velocity of
individual drive wheel assemblies while maintaining the drive
torque share provided to the handrail 42.
[00033] FIG. 4 shows a more detailed schematic cross-sectional view
of the planetary gear train of the additional drive wheel
assembly 50A depicted in FIGS. 3A and 3B together with one of a
plurality of pinch roller assemblies 103 (discussed further
below with reference to FIG. 6). The schematic figures depicted
in FIGS. 2, 3A-3D, and 4 are not to scale. Although the sizes
of various elements relative to other elements may differ from
one figure to the next, one of ordinary skill in the art will
recognize that this does not detract from the mechanical

relationships intended to be depicted therein. For example, in
FIG. 4, sun gear output portion 60A of the additional drive
wheel assembly 50A is shown as having a smaller diameter than
other elements such as, for example, ring gear 58A, whereas in
FIGS. 3A and 3B, output portion 60A is shown as having a larger
diameter than ring gear 58A. In both cases, however, output
portion 60A forms part of sun gear member 56A and is arranged to
drive the handrail 42.
[00034] In another embodiment of the invention shown in FIG. 6, a
pinch roller force mechanism 100 is arranged to provide equal
pinch force to the handrail 101 at a handrail contact point of
each of a plurality of drive wheel assemblies 102 in order to
minimize the affect of one of the variable drive parameters.
The drive wheel assemblies 102 shown together with the pinch
roller force mechanism 100 in the embodiment of FIG. 6 may be
any of the drive wheel assemblies described herein or other
known drive wheel assemblies. The pinch roller force mechanism
100 includes a plurality of pinch roller assemblies 103 having
pinch rollers 104, each of which is arranged on an opposite side
of the handrail 101 from an output portion of the drive wheel
assemblies 102. The pinch rollers 104 force the handrail 101
against the output portion of each respective drive wheel
assembly 102 in a direction normal to the direction of travel of
the handrail 101.
[00035] Each pinch roller assembly 103 includes multiple pulleys
105, 106, 107 arranged on the pinch roller 104 such that a cable
108 received by the pulleys 105, 106, 107 forces each of the
pinch rollers against the handrail 101 with equal force based on
the tension in the cable 108. Each pinch roller 104 may have
the pulleys 105, 106, 107 arranged on only one side thereof such
that cable 108 only extends along one side of the pinch rollers
104. Alternatively, each pinch roller 104 may have the pulleys
105, 106, 107 arranged on both sides thereof such that cable 108

extends along both sides of the pinch roller 104. In this
instance, cable 108 may be a single continuous cable extending
along both sides of the pinch rollers 104 or, alternatively, two
separate cables, each extending along a respective side of the
pinch rollers 104. In the embodiment depicted in FIG. 6, the
cable 108 can only be seen extending along the visible side of
each pinch roller 104. The cable 108 is adjustably secured to a
frame 110 via an attachment element 115 and an adjustment
mechanism 109. The cable 108 is also fixedly secured to a frame
111. The attachment element 115 may be a member that receives
and grips an end of the cable 108. Alternatively, attachment
element 115 may be a pulley having a rotational axis parallel to
the pinch force direction of each pinch roller 104 so as to
allow a single continuous cable 108 having first and second ends
fixedly secured to frame 111 to extend along both sides of the
pinch rollers 104. In either case, adjustment mechanism 109 is
coupled to the attachment element 115 and includes a threaded
end attached to a nut 113. A compression spring 112 is provided
between the nut 113 and the frame 110 to provide adjustable
tension in the cable 108. The pinch roller force mechanism 100
provides equal tensioning and pinching magnitude at each of the
drive wheel assemblies 102 as shown in FIG. 6. It is further
envisioned that the cable tension could be regulated according
to the driving force required from the drive wheel assemblies,
thus, providing optimized pinch force to the drive and handrail
as necessary and according to the drive force requirements.
[00036] As shown schematically in FIG. 7, it is also envisioned
that the parallel fashion of driving a handrail described above
could be achieved with a hydraulic arrangement 200. For
example, in hydraulic arrangement 200, each drive wheel assembly
202 for driving a handrail 201 includes a hydraulic drive motor
203 located at and connected to the drive wheel assembly 202.
The hydraulic motor 203 of each respective drive wheel assembly

202 is plumbed in parallel with the other hydraulic motors 203
via a hydraulic pressure line 204. As a result, each hydraulic
motor 203 and, consequently, each drive wheel assembly 202,
assumes a portion of the total drive load according to the
displacement of each motor and the common pressure. As with the
mechanical system counterpart described above, any variation in
rolling radii or other drive parameters in any of the drive
wheel assemblies 202 are compensated for by a corresponding
change to the angular velocity of the corresponding motor 203
and drive wheel assembly 202 while maintaining each motor's
share of the load. The hydraulic arrangement 20 0 may also port
the pressure of the drive motors 203 along a line 205 to
hydraulic cylinder(s) 207 coupled to pinch rollers 206 to
provide a pinch force proportional to the drive system load
resulting in optimized, load compensated pinch forces on the
handrail 201 shown in FIG. 7.
[00037] It is also envisioned that the parallel fashion of driving
a handrail could be accomplished electrically using a plurality
of AC drive wheel motors and variable frequency control(s) (not
shown).
[00038] While the invention has been described with respect to
certain examples and embodiments, modifications may be made
within the scope of the invention as defined by the appended
claims.

WHAT IS CLAIMED IS:
1. A handrail drive apparatus comprising:
a first drive wheel assembly configured to drive a
handrail and comprising a planetary gear train arranged to be
driven by a first driving member; and
a second drive wheel assembly configured to drive the
handrail, the second drive wheel assembly being coupled to the
planetary gear train of the first handrail drive wheel assembly
by a second driving member, wherein the planetary gear train of
the first handrail drive wheel assembly is configured to divide
a torque imparted to the first drive wheel assembly by the first
driving member substantially equally between the first and
second drive wheel assemblies.
2. The handrail drive apparatus of claim 1, wherein the
planetary gear train of the first drive wheel assembly
comprises:
a sun gear member rotatably arranged about a first
axis and including an output portion arranged to contact and
drive the handrail;
a planet carrier rotatably arranged about the first
axis ;
a ring gear member rotatably arranged about the first
axis; and
at least one planet gear coupled to the planet
carrier, wherein the at least one planet gear meshes with the
sun gear and the ring gear and is arranged to rotate about a
second axis extending substantially parallel to the first axis.
3. The handrail drive apparatus of any one of the
preceding claims, wherein the first driving member is coupled to
the planet carrier to impart torque to the first drive wheel

assembly.
4. The handrail drive apparatus of any one of the
preceding claims, wherein the second driving member is coupled
between the ring gear member and the second drive wheel
assembly.
5. The handrail drive apparatus of any one of the
preceding claims, wherein the at least one planet gear divides
the torque imparted by the first driving member to the planet
carrier between the sun gear member and the ring gear member.
6. The handrail drive apparatus of any one of the
preceding claims, wherein the at least one planet gear is a
compound planet gear.
7. The handrail drive apparatus of claim 6, wherein the
compound planet gear has a first portion arranged to mesh with
the sun gear and a second portion arranged to mesh with the ring
gear, the first and second portions of the compound planet gear
having different diameters.
8. The handrail drive apparatus of claims 7, wherein the
diameter of the first portion of the compound planet gear is
smaller than the diameter of the second portion of the compound
planet gear.
9. The handrail drive apparatus of any one of the
preceding claims, wherein the first driving member comprises a
belt or a chain.
10. The handrail drive apparatus of any one of the
preceding claims, wherein the second driving member comprises a

belt or a chain.
11. The handrail drive apparatus of any one of the
preceding claims, further comprising a plurality of pinch
rollers, each pinch roller being arranged opposite one of the
first and second drive wheel assemblies to force the handrail
against a drive surface of the first and second drive wheel
assemblies.
12. The handrail drive apparatus of claim 11, wherein the
plurality of pinch rollers are coupled to one another such that
each pinch roller applies equal force to the handrail.
13. The handrail drive apparatus of claims 11 or 12,
further comprising a cable coupling each of the plurality of
pinch rollers to one another, the cable having a first end
adjustably secured to a frame of the apparatus and a second end
fixedly secured to the frame of the apparatus, and wherein each
of the plurality of pinch rollers comprises at least one pulley
arranged to receive the cable such that tension in the cable
forces the pinch roller against the handrail in a direction
substantially normal to a direction of movement of the handrail.
14. The handrail drive apparatus of claim 13, wherein the
first end of the cable is attached to an adjustment mechanism,
the adjustment mechanism including:
a threaded portion engaged by a nut; and
a compression spring disposed between the nut and the
frame of the apparatus to adjustably secure the cable to the
frame.
15. The handrail drive apparatus of claim 11, further
comprising a cable coupling each of the plurality of pinch

rollers to one another, wherein the cable is adjustably secured
to a frame of the handrail drive apparatus at a first point
along its length and is fixedly secured to the frame of the
apparatus at a second point along its length, and wherein each
of the plurality of pinch rollers comprises at least one pulley
arranged to receive the cable such that tension in the cable
forces the pinch roller against the handrail in a direction
substantially normal to a direction of movement of the handrail.
16. The handrail drive apparatus of claim 15, wherein the
cable is adjustably secured to the frame by an adjustment
mechanism, the adjustment mechanism including:
a pulley over which the cable passes;
a threaded portion engaged by a nut; and
a compression spring disposed between the nut and the
frame of the apparatus.
17. A pinch force equalizing device for use in a handrail
drive apparatus, the pinch force equalizing device comprising:
a plurality of pinch rollers, each pinch roller being
arranged opposite one of a plurality of drive wheel assemblies
to force a handrail against a drive surface of each of the
plurality of drive wheel assemblies, wherein the plurality of
pinch rollers are coupled to one another such that each pinch
roller applies equal force to the handrail.
18. The pinch force equalizing device of claim 17, further
comprising a cable coupling each of the plurality of pinch
rollers to one another, the cable having a first end adjustably
secured to a frame of the handrail drive apparatus and a second
end fixedly secured to the frame of the apparatus, and wherein
each of the plurality of pinch rollers comprises at least one
pulley arranged to receive the cable such that tension in the

cable forces the pinch roller against the handrail in a
direction substantially normal to a direction of movement of the
handrail.
19. The pinch force equalizing device of any one of claims
17 and 18, wherein the first end of the cable is attached to an
adjustment mechanism, the adjustment mechanism including:
a threaded portion engaged by a nut; and
a compression spring disposed between the nut and the
frame of the apparatus to adjustably secure the cable to the
frame.
20. The pinch force equalizing device of any one of claims
17-19, wherein the at least one pulley comprises three pulleys.
21. The pinch force equalizing device of any one of claims
17-20, wherein the cable extends along both sides of each pinch
roller.
22. The pinch force equalizing device of claim 17, further
comprising a cable coupling each of the plurality of pinch
rollers to one another, wherein the cable is adjustably secured
to a frame of the handrail drive apparatus at a first point
along its length and is fixedly secured to the frame of the
apparatus at a second point along its length, and wherein each
of the plurality of pinch rollers comprises at least one pulley
arranged to receive the cable such that tension in the cable
forces the pinch roller against the handrail in a direction
substantially normal to a direction of movement of the handrail.
23. The pinch force equalizing device of any one of claims
17 and 22, wherein the cable is adjustably secured to the frame
by an adjustment mechanism, the adjustment mechanism including:

a pulley over which the cable passes;
a threaded portion engaged by a nut; and
a compression spring disposed between the nut and the
frame of the apparatus.
24. The pinch force equalizing device of any one of claims
17, 22, and 23, wherein the at least one pulley comprises three
pulleys.
25. The pinch force equalizing device of any one of claims
17 and 22-24, wherein the cable extends along both sides of each
pinch roller.
26. A handrail drive apparatus comprising:
a first driving wheel member arranged to drive a
handrail;
a second driving wheel member coupled to the first
driving wheel member and arranged to drive the handrail; and
means for dividing a torque imparted to the first
driving wheel substantially equally between the first and second
driving wheel members.
27. The handrail drive apparatus of claim 26, further
comprising a plurality of pinch rollers, each pinch roller being
arranged opposite one of the first and second drive wheel
assemblies to force the handrail against a drive surface of the
first and second drive wheel assemblies.
28. The handrail drive apparatus of claim 27, wherein the
plurality of pinch rollers are coupled to one another such that
each pinch roller applies equal force to the handrail.
29. The handrail drive apparatus of claims 27 or 28,

further comprising a cable coupling each of the plurality of
pinch rollers to one another, the cable having a first end
adjustably secured to a frame of the apparatus and a second end
fixedly secured to the frame of the apparatus, and wherein each
of the plurality of pinch rollers comprises at least one pulley
arranged to receive the cable such that tension in the cable
forces the pinch roller against the handrail in a direction
substantially normal to a direction of movement of the handrail.
30. The handrail drive apparatus of claim 29, wherein the
first end of the cable is attached to an adjustment mechanism,
the adjustment mechanism including:
a threaded portion engaged by a nut; and
a compression spring disposed between the nut and the
frame of the apparatus to adjustably secure the cable to the
frame.
31. The handrail drive apparatus of claims 27 or 28,
further comprising a cable coupling each of the plurality of
pinch rollers to one another, wherein the cable is adjustably
secured to a frame of the handrail drive apparatus at a first
point along its length and is fixedly secured to the frame of
the apparatus at a second point along its length, and wherein
each of the plurality of pinch rollers comprises at least one
pulley arranged to receive the cable such that tension in the
cable forces the pinch roller against the handrail in a
direction substantially normal to a direction of movement of the
handrail.
32. The handrail drive apparatus of claim 31, wherein the
cable is adjustably secured to the frame by an adjustment
mechanism, the adjustment mechanism including:
a pulley over which the cable passes;

a threaded portion engaged by a nut; and
a compression spring disposed between the nut and the
frame of the apparatus.
33. A handrail drive apparatus comprising:
a first driving wheel member arranged to drive a
handrail and comprising a power transmission mechanism; and
a second driving wheel member coupled to the first
driving wheel member and arranged to drive the handrail, wherein
the power transmission mechanism is configured to divide a
torque imparted to the first driving wheel member substantially
equally between the first and second driving wheel members.
34. The handrail drive apparatus of claim 33, further
comprising:
an additional driving wheel member arranged to drive
the handrail and comprising an additional power transmission
mechanism including an input and an output, wherein the input of
the additional power transmission mechanism is arranged to
receive an input torque and the output of the additional power
transmission mechanism is coupled to the power transmission
mechanism of the first driving wheel member to impart torque
thereto, and wherein the additional power transmission mechanism
is configured to divide the input torque between the additional
and first driving wheel members such that the input torque is
divided substantially equally between the additional, first, and
second driving wheel members.


A handrail drive apparatus is provided comprising a first drive wheel assembly (60) configured to drive a handrail
(42) and comprising a planetary gear train arranged to he driven by a first driving member (46). The handrail drive apparatus further
comprises a second drive wheel assembly (41) configured to drive the handrail, the second drive wheel assembly being coupled to
the planetary gear train of the first handrail drive wheel assembly by a second driving member (48). The planetary gear train of
the first handrail drive wheel assembly is configured to divide a torque imparted by the first driving member between the first and
second drive wheel assemblies.