Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE INVENTION
The present invention relates to a friction drive appara-
tus for imparting generally linear motion to a member, and more
~ particularly to a friction drive apparatus having the entire
~ drive train, including the friction drive wheel, mounted on a
~ ; movable support frame which is biased toward the member. The
F present invention finds particular utility in providing a con-
i stant friction drive force for rotating a rotary sorting con- veyor support ring.
Various devices have been employed for distributing and
sorting articles and packages, including items of mail or mer-
chandise. As discussed in U. S. Patent No. 3,750,879 granted
August 7, 1973, such devices may take the form of a rotary car-
rousel-type conveyor having a plurality of panels or carriages
pivotally mounted on a support ring, wherein the articles to
be conveyed are fed to the carriages and upon rotation of the
carrousel to the appropriate location, the carriage is tilted,
causing the article to enter an a~jacent discharge chute. In
this prior art device, the support ring is caused to rotate
about its axis by two vertically aligned friction drive wheels
which are fixedly mounted beneath the ring approximately 180
apart. In this arrangement, the friction drive force, being
dependent strictly on the force of gravity acting on the car-
rousel, is not easily controlled or maintained at a constant
~5 ~ value. Furthermore, drive wheel wear wil} act to alter the
friction drive force over time, thus necessitating replacement
or repositioning of the drive wheels.
The baggage handling turntable assembly disclosed in U. S.
Patent No. 3,180,483, granted April 27, 1965, has a rotary plat-
form comprised of radial frame elements attached to an annular
support rail which is shown as an L-shaped angle section. This
device utilizes a drive roller and a back-up roller mounted on
opposite sides of the vertical leg of the support rail to impart
friction drive to the rail, with the wheels being spring loaded
together. A problem inherent in this type of device is that any
variation in the thickness of the vertical leg of the rail will
result in a variable driving force. Furthermore, any out-of-
roundness of the support rail will result in movement of the~
drive roller, which movement will result in a reaction force,
i tending to horizontally displace the rotary platform from its
normal position. These factors may also result in uneven drive
wheel force, which is a considerable disadvantage.
SUMMARY OF THE INVENTION
The present invention overcomes the problems and disadvan-
tages of the prior art by providing a friction drive apparatus
having a drive force which is easily set and maintained at a
constant value.
- Another object of the invention is to provide a friction
drive apparatus for a rotary sorting conveyor support member
which will produce little, if any, horizontal displacement of
the conveyor as a result of any out-of-roundness of the support
member.
Yet another object of the invention is to provide a fric-
tion drive apparatus which automatically compensates for drive
wheel wear and which is fully reversib~e.
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Additional objects and advantages of the invention will be
set forth in part in the description which follows, and in part
will be obvious from the description, or may be learned by practice
of the invention. The objects and advantages of the invention may
be realized and attained by means of the instrumentalities and
combinations particularly pointed out in the appended claims.
To achieve the objects, and in accordance with the purpose of
the invention, as embodied and broadly described herein, the fric-
tion drive apparatus of this invention is adapted to impart
generally linear motion to a member having first and second
laterally spaced surfaces, and comprises a fixed support, a
rotatable friction wheel in driving contact with the first sur-
~face of the member, a movable support frame mounted on the fixed
~support for linear movement normal to the plane of tangency at
the point of contact between the friction wheel and the first
surface of the member, drive means rigidly secured to the movable
~support frame and connected to the friction wheel for rotating
the wheel, means for biasing the movable support frame toward
the plane of tangency at the point of contact between the fric-
tion wheel and the first surface of the member, thereby biasing
the friction wheel against the first surface of the member, and
~a freely rotatable back-up wheel having its circumferential
periphery in contact with the second surfac~ of the member, with
~ the back-up wheel being rigidly secured to the fixed support
opposite from the friction wheel. The member to which motion is
; ~ to be imparted typically comprises an annular structure, with
the friction wheel being in contact with the inner circumferential
periphery of the structure, and the bac~-up wheel being in contact
;with the outer circumferential periphery of the structure.
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The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate one embodi-
; ment of the invention, and, together with the description,
serve to explain the principles of the invention.
BRIEF DESCRIPTION ~F THE DRAWINGS
Figure 1 is a schematic diagram showing a top view of a
rotary sorting conveyor having a friction drive apparatus con-
structed in accordance with the present invention.
Figure 2 is an enlarged schematic diagram of the friction
drive apparatus shown in Fig. 1.
Figure 3 is a schematic diagram showing a side view of
the friction drive apparatus illustrated in Figs. 1 and 2.
; DESCRIPTION OF THE PREFE~RED EMBODIMENT
Reference will now be made in detail to the presently
preferred embodiment of the invention, an example of which
is illustrated in the accompanying drawings.
The preferred embodiment of the friction drive apparatus
of the present invention is shown in Figs. 1-3, and is rep-
resented generally by the numeral 10. The drive apparatus is
adapted to impart generally linear motion to a member 12. As
embodied herein, member 12 preferably includes a first sur-
face 14 and a second surface 16, which are laterally spaced
apart. Member 12 may comprise a four-sided structure, as shown
in Fig. 3, or, as another example, may be U-shaped.
In the preferred embodiment depicted in Fig. 1, member 12
comprises an annular structure, with the first and second sur-
faces comprising, respectively, the inner and outer circumfer-
~ential peripheries of the structure. As shown, member 12
may be constructed as a structural steel ring supported and
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~" ` centered by vertically aligned support wheels 18 and horizon-
tally aligned guide wheels 20 angularly spaced about the ring,
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` Ilwith the support wheels lying beneath the ring and the guide
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wheels contacting the outer periphery of the ring. A
l,plurality of carriages with tilting tray tops, represented gen-
~erally by the numeral 22, may be mounted on the support ring,
¦iwith the tilting trays being pivotally mounted to the carriage
,~in a conventionally known manner. The carriages are adapted to
receive the articles to be conveyed and sorted at a central in-
~ 10 liduction station 24 and to discharge the articles at the appro-
p~ I priate discharge chute 26.
¦I While the invention finds particular utility in the appli-
~¦cation of a driving force to a rotary sorting conveyor support
ring, as illustrated in Fig. 1, the scope of the invention is
¦obviously not so limited. The friction drive apparatus des-
cribed herein is suitable for imparting generally linear motion
¦to essentially any type of support member.
As can best be seen in Figs. 2 and 3, the friction drive
¦apparatus of the present invention.includes a fixed support 30,
Itypically construc~ed as a structural steel frame and adapted
Ito carry the other elements of the drive apparatus, as will be
¦discussed below. A freely rotatable back-up wheel 32 is secured
~at one end of support 30 via an adjustable bracket 34 and con-
ventional axle and bearing supports (not shown). Frame 30 is
l~situated such that the back-up wheel 32 will contact, or nearly
¦~contact, one surface of the carriage support member 12, with the
¦¦final ad~ustment of the contacting force being made via one or
more adjustment bolts 36 which secure bracket 34 to frame 30.
In the embodiment illustrated in Fig. 1, the back-up wheel is
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33
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situated so as to contact the outer circumferential periphery 16
,
of the carriage support ring.
~- The purpose of the back-up wheel is to offset the force
exerted by the friction wheel 38, to be discussed below. Thus,
ilthe back-up wheel will preferably be aligned directly opposite
the friction wheel. In the preferred embodiment shown in Fig.
1, the axes of rotation of the friction wheel and the back-up
wheel are radially aligned with the axis of rotation P of the
annular carriage support ring 12. It should be noted, however,
¦'that the back-up wheel and the friction wheel need not be pre-
cisely aligned vertically, and in a preferred embodiment, the
back-up wheel may be aligned on the order of 3/4 inch lower
than the friction wheel.
In order to maintain non-slipping contact between the fric-
Ition wheel and the support member, the circumferential periphery
of the friction wheel is preferably comprised of a non-skid
material such as, for example, rubber or another similar mater-
ial. In the embodiment shown in Figs. 1-3, the non-skid material
comprises a soft rubber tire. Similarly, the outer periphery of
~ 20 ¦¦ back-up wheel 32 is preferably comprised of a hard rubber or sim-
{~ Ililar non-skid material.
As embodied herein, friction wheel 38 is rotatably mounted
via axle 40 which is supported by bearings 42 secured to support
bracket 44. The support bracket is secured to a movable support
¦jframe 46 which may typically be constructed as a four-sided
structural steel frame. As embodied herein, movable support ~,
¦iframe 46 is situated within the confines of fixed support 3~,
~ and is mounted on the fixed support by support wheels 48 rotat-
- ~lably mounted on the movable support frame. Fixed support 30 is
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.: preferably constructed with rails 50 laterally spaced from the
sides of movable support frame 46 and adapted to provide support
for wheels 48. Fixed support 30 will also preferably include
guide rails 52 situated above rails 50 and spaced therefrom by
~i 5 ¦la distance approximately equal to the diameter of wheels 48 so
.as to limit the movement of wheels 48, and thereby movable sup-
¦iport frame 46, in the vertical plane. Thus, in addition to sup-
porting movable support frame 46 on fixed support 30, support
¦¦wheels 48 may serve to prevent unwanted vertical movement of
!frame 46.
~' ~ As embodied herein, unwanted lateral movement of movable
~support frame 46 i8 preferably prevented through the use of
¦horizontally aligned guide wheels 54 mounted at the respective
corners of frame 46 by conventional bearing brackets 56. Fixed
Isupport 30 may be constructed with additional guide rails (not
¦shown) laterally spaced from the sides of movable support frame
46 and adapted to contact horizontal guide wheels 54, or, as
¦Ishown in Figs. 2 and 3, guide rails 52 may be constructed such
¦ that their interior sides contact wheels 54, thereby serving
¦ to restrict their lateral movement, thus restricting lateral
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movement of movable support frame 46.
As can be seen, vertical support wheels 48 and horizontal
¦¦guide wheels 54, in contact with their respective support and/
or guide rails, serve to precisely control the direction of ¦
~¦movement of support frame 46 and to limit any unwanted dis-
¦ placements of the frame.
n accordance with the invention, a drive means 58 is
rigidly secured to movable support frame 46, and is prefer-
ably connected to friction wheel 3B via a motion-translating
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speed reducer 60, which is also secured to movable support
frame 46. As embodied herein, the drive means 58 comprises a
variable speed electric motor. As further embodied herein,
the output shaft 62 of drive means 58 and the input shaft 64
of speed reducer 60 are connected via pulleys and drive belt
66 substantially as shown. Likewise, the output shaft 68 of
speed reducer 60 has a sprocket wheel 70 secured to it, while
the axle 40 of friction wheel 38 has a similar sprocket 72,
and these two sprockets are connected via a conventional roller
~ chain 74.
In accordance with the invention, fixed support 30, includ-
ing support rails 50 and guide rails 52, and movable support
frame 46, including the drive means 58, the speed reducer 60,
the friction wheel support bracket 44 and bearings 42, the fric-
tion wheel 38 and its associated axle 40 mounted thereon are
situated such that rotating friction wheel 38 may be brought in-
to driving contact with carriage support member 12 by rolling
movement of support frame 46 along the support rails 50 of fixed
support 30. As embodied herein, the above-recited elements are
further situated such that movement of support frame 46 along
fixed support 30 is limited to strictly linear movement normal
to the plane of tangency at the point of contact between friction
wheel 38 and carriage support member 12. In a preferred embodi-
~ment of the invention, support member 12, friction wheel 38, and
back-up wheel 32 are situated substantially horizontally.
The preferred embodiment shown in Fig. 1, wherein support
member t2 comprises an annular ring having inner and outer cir-
cumferential surfaces 14 and 16, respectively, is constructed
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such that friction wheel 38 contacts the inner circumferential
surface 14.
In accordance with the invention, friction wheel 38 is
maintained in driving contact with carriage support member 12
at a constant friction drive force by means for biasing the
movable support frame 46 toward the plane of tangency at the
point of contact between member 12 and friction wheel 38,
thereby biasing the friction wheel against the member. As em-
~ bodied herein, the means for biasing the movable support frame
comprises at least one compression spring 76 mounted in a con-
ventional manner as shown, for example, in Fig. 3. In this
embodiment, spring 76 is mounted at one end of rod 78 which ex-
tends through an opening in movable support frame 46 and is
secured at its other end to fixed support 30. One end of spring
15 ~ 76 abuts the inner periphery of support frame 46 and the other
, ~ .
end abuts a nut 80 which is adjustably secured near the end of
the rod. The spring compression may thus be set at the desired
value by adjusting the position of nut 80 on the rod.
By increasing the spring compression, the contact force
between the friction wheel and the carriage support member may
be increased, thereby increasing the tangential driving force
applied by the friction wheel. Similarly, the tangential driv-
ing force may be decreased by decreasing the spring compression.
As further embodied herein, the means for biasing the movable
support frame may alternatively comprise one or more air cylin-
ders arranged between the movable frame and the fixed support
in a conventional manner.
It will be apparent to those s~illed in the art that var-
ious modifications and variations can be made in the friction
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drive apparatus of the present invention without departing from
the spirit or scope of the invention. As an example, the tan-
gential driving force applied to the carriage support member
12 by friction wheel 38 may be increased by providing additional
~ compression springs arranged similarly to spring 76. Thus, it
~is intended that the present invention cover modifications and
;variations of this invention, provided they come within the
scope of ehe appended claim~ and their equivalents.
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