Chain for a trolley conveyor system

A trolley conveyor system chain for pulling trays of the conveyor through horizontal turns and climbing and descending grades. A link of the chain has a single pair of vertical and a single pair of horizontal wheels mounted thereon. A Y or vertical axis of the vertical wheels and an X or horizontal axis of the horizontal wheels intersect at a point and a link mechanism maintains the horizontal wheels in an ideal position relative to a chain rail assembly on which the wheels rotate and also aligns the chain to prevent collapse of the chain under tensile and compressive forces.

BACKGROUND OF THE INVENTION 
1. Field of Invention 
This invention relates to chains for use in pulling a trolley over a track. 
More particularly, the invention relates to chains of the type that make 
horizontal turns and climb and descend grades. 
2. Brief Description of the Prior Art 
Trolley conveyor systems are known that move trays along a predetermined 
path defined by a pair of parallel tracks to transport boxed or packaged 
materials within a storage or production facility. In a prior art conveyor 
system, a chain consisting of hollow tubular tow bars interconnected by a 
three axle link incrementally spaced along the predetermined path pulls 
the trays. The path includes both horizontal turns and climbs and descents 
in a vertical plane. 
The chain in this prior art conveyor system is partially enclosed within a 
chain rail assembly located intermediate the pair of tracks. The chain 
rail assembly consists of four separate rails partially enclosing the 
link. The chain is subject to tension and compression forces as it is 
separately driven to pull the trays. 
The link of the prior art includes a single pair of horizontal wheels, 
which wheels support the weight of the chain and assist the vertical 
wheels in guiding the chain along the path. The horizontal wheels are 
rotatably mounted on one axle and each horizontal wheel travels between 
upper and lower rails of the chain rail assembly. Two pairs of vertical 
wheels, which serve to guide the chain along the path and through turns, 
are mounted on half-link extensions equidistant fore and aft of the 
horizontal wheels. The extensions are therefore connected to each other by 
cylindrical bearings on the horizontal wheel axle. The vertical wheels are 
mounted on the other two axles of the link and also travel between the 
rails of the chain rail assembly. The axles of the vertical wheels are 
connected to the tow bars by cylindrical bearings. 
The chain therefore follows the path of the chain rail assembly, pulling 
the trays along the tracks. When the chain must climb a grade, the fore 
and aft extensions of the link pivot about another cylindrical bearing on 
the horizontal wheel axle. In making a horizontal turn, the tow bars pivot 
about the two vertical wheel axles. 
It is therefore seen that the prior art conveyor system uses three axles to 
a link between tow bars. Each axle has a cylindrical bearing. As the chain 
is pulled along the path of the chain rail assembly, the link is loaded at 
each of the three axles. Each axle has a cylindrical bearing subject to 
maximum loading as the chain is pulled along a straight line path and 
which bearings must be lubricated to reduce associated wear and maintain 
performance. 
The prior art link uses the two pairs of vertical wheels which contact the 
chain rail assembly to maintain the pair of horizontal wheels at all times 
perpendicular to a tangent through the curve of a horizontal turn made by 
the chain rail assembly. However, because the vertical wheels are 
positioned by and spaced away from the horizontal wheels on extensions, 
the horizontal wheels do not precisely ride on the chain rails, but ride 
slightly off of the rails. This in turn subjects the horizontal wheels to 
some wear as a horizontal turn is made. 
It would be advantageous over the prior art to have a link including a 
single pair of horizontal wheels and a single pair of vertical wheels 
whose rotational axes intersect at a single point. The prior art link 
horizontal and vertical wheels act at essentially three points along the 
length of the link, one for each pair of wheels. Using the three spaced 
apart pairs of wheels of the link of the prior art, the chain rail 
assembly often has to follow compelx "S" curves in order for the link of 
the chain to pull a tray through a simple horizontal turn. If all wheels 
acted essentially at a single point, the chain rail assembly curve would 
be a simple horizontal turn and the horizontal wheels would ride on and 
more precisely follow the path of the chain rail assembly. 
SUMMARY AND OBJECTS OF THE INVENTION 
The principal object of the present invention is to provide a link for a 
trolley conveyor system chain that acts essentially at a single point. 
Another object of the present invention is to lower initial cost as well as 
maintenance costs in a conveyor system, while increasing performance. 
Still another object of the present invention is to allow a simpler design 
for the chain rail assembly of a conveyor system. 
A further object of the present invention is to provide a trolley conveyor 
system that does not collapse as the chain is subjected to tensile and 
compressive forces. 
In accordance with the objects of the invention, a trolley conveyor system 
chain includes a link having a frame pivotally mounted on a single 
vertical axle, which has a pair of vertical wheels mounted at either end 
thereof, and a pair of horizontal wheels rotatably mounted on horizontal 
axles integrally extending away from the frame. The horizontal and 
vertical wheels are positioned between four separate rails forming a chain 
rail assembly. A rearward end of a leading tubular tow bar is universally 
connected to the vertical axle to pivot about both an X axis of the link, 
coaxial with the axis of rotation of the horizontal wheels, and a Y axis 
of the link, coaxial with the axis of rotation of the vertical wheels, 
which axes intersect at a single point. A forward end of a trailing tow 
bar in the direction of conveyor travel is rigidly connected to the 
vertical axle. 
A link mechanism or system slideably relative to the frame and rigidly 
mounted on the two tow bars on either side thereof, defines four pivot 
points. The second and third pivot points are fixed relative to the 
leading and trailing tow bars respectively. A first pivot point, and a 
fourth pivot point cooincident with the Y axis directly opposite the first 
pivot point, are always aligned along the X axis by the link mechanism so 
that the angle between the leading and trailing tow bars is always 
bisected by the X axis. The X axis, i.e. the rotational axis of the 
horizontal wheels, is therefore always perpendicular to a tangent through 
the curvilinear path of the chain rail assembly at the point of 
intersection of the X and Y axes. 
When the link is used to universally connect adjacent members, the vertical 
and horizontal wheels, confined within the chain rail assembly aligns the 
tow bars. Therefore, even though universally connected, the tow bars do 
not pivot out of alignment when subjected to tensile and compressive 
forces. 
In an alternative embodiment, spring bias means are utilized to 
interconnect the leading tow bar and the trailing tow bar to the link. In 
this manner the angle between the two tow bars is generally bisected by 
the X axis of the link.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A segment of a trolley conveyor system 20 utilizing the present invention 
is seen in FIGS. 1 and 2. Such a conveyor system is useful in the 
transportation of boxed or packaged material such as mail or the like 
within a manufacturing or storage facility. The conveyor system 20 is 
adapted to move in three dimensions by making left or right horizontal 
turns and climbing and descending grades. 
The conveyor system 20 includes a plurality of trays 22 extending at spaced 
intervals continuously over the length of the conveyor system. The trays 
are open at the top and have walls and a bottom for containing the 
material to be transported. A pair of parallel trolley tracks 24 define 
the path over which the trays move. A pair of flanged horizontal wheels 26 
extend laterally from each of the trays to rotatably contact the track 24. 
The sheels 26 are rotatably mounted from the underside of one end of each 
tray 22 through a pair of stub axles 28. A connecting rod 30 is also 
connected to the underside of the trays 22 at the end where the wheels 26 
are connected. The connecting rod extends away from the wheels, under the 
tray toward the leading end of the tray of the conveyor system and 
downward to pivotally connect through a universal joint 46 and a fork yoke 
47 (FIG. 2) to a continuous chain 32. 
The continuous chain 32 is subjected to tensile and compressive forces as 
it is moved by a drive system 130 to, be discussed more fully hereinafter, 
and includes a plurality of connecting members or links 38 incrementally 
spaced apart by hollow elongated arms or tow bars 40. A leading tow bar 
leads the link in the path of conveyor travel, while a trailing tow bar 
trails the link in the direction of conveyor travel. The chain 32 follows 
a path defined by a chain rail assembly 34 of generally square transverse 
cross section (FIG. 3) to the path of travel of the conveyor system 20. 
The chain rail assembly is located between the trolley tracks 24 and is 
formed of four separate rails 34a, 34b, 34c and 34d, spaced equidistantly 
from each other. The chain rail assembly partially encloses the chain. 
Each of the rails has a pair of bearing surfaces 36 that face, 
respectively, the two adjacent rails. For example, rail 34a has bearing 
surfaces 36 which face rails 34d and 34b. 
The link 38 includes a generally rectangular frame 41 with an enlarged 
opening 46 aligned along the direction of conveyor travel (FIGS. 4 and 5). 
Cylindrical bearings 43 in the frame journal a vertical axle 47, coaxial 
with a Y axis 45 extending vertically through the frame of the link. An X 
axis 43 is perpendicular to and intersecting the Y axis and extends 
horizontally from the frame of the link in a direction generally 
transverse to the path of conveyor travel. The frame has relatively short 
integral axles 49 and 51 extending along the X axis and away from the 
frame, axle 51 having a bore or opening 53 extending through the axle's 
entire length. 
A single pair of horizontal wheels 42 coaxial with the X axis 43 are 
rotatably mounted on axles 49 and 51. A single pair of vertical wheels 44 
coaxial with the Y axis 45 are rotatably mounted at either end of the 
vertical axle 47. The vertical wheels and horizontal wheels travel on the 
bearing surfaces 36 of the rails 34a through 34d (FIG. 3) and guide the 
chain 32 along the predetermined three dimensional path. The rail assembly 
and the horizontal and vertical wheels align adjacent tow bars universally 
connected to the link 38 to prevent collapse of the chain as it is 
subjected to tensile and compressive forces. 
Roller bearings 72 conventionally fitted around the axles 49 and 51 allow 
for rotatably mounting of the horizontal wheels 42. Similar roller 
bearings 72 are mounted on either end of the vertical axle 47 at the point 
where it extends beyond the frame 41 to provide for rotatable mounting of 
the vertical wheels 44. 
The Y axis 45 and X axis 43 intersect at a single point 49. This single 
point represents each link 38 as it moves along the chain rail assembly 
34. The single point 49 lies essentially at the center of the chain rail 
assembly (FIG. 3). 
In making a single link 38 a part of the chain 32, a forward end 50 of the 
trailing tubular tow bar 40 is rigidly connected about vertical axle 47, 
through the opening 46 in the frame 41 by a fork yoke 58. A hollow 
circumferential fitting 60 of the fork yoke 58 fits over a shoulder 61 on 
the forward end of the hollow tow bar 40 (FIG. 4). The circumferential 
fitting is rigidly connected to the shoulder by welding. The forward end 
of the trailing tow bar is pivotal in a horizontal plane only about Y axis 
45 because the vertical axle is journalled in the frame 41. 
A self-lubricating spherical bearing 63 universally connects a rearward end 
54 of the leading tow bar 40 to the vertical axle 47 of the link 38 (FIGS. 
4 and 5). The spherical bearing 63 is mounted intermediate upper and lower 
arms of the yoke 58 on the vertical axle. A threaded connection between 
spherical bearing 63 and tow bar 40 results in a rigid connection, as seen 
in FIG. 4. Thus, the rearward end 54 of the leading tow bar 40 is 
pivotally connected about the Y axis 45 of the link 38 to turn in a 
horizontal plane, when the chain makes a horizontal turn. The rearward end 
54 is also pivotal about the X axis 43 to allow turns in a vertical plane, 
as the link climbs or descends a grade. The overall chain 32 moves in both 
horizontal and vertical planes. 
The links 38 of the chain 32 of the present invention maintain the 
horizontal wheels 42 in the ideal position, perpendicular to a line 
tangent to a horizontal curve defined by the chain rail assembly 34 at the 
particular location of single point 49 by a four link mechanism or system 
74 (FIGS. 4 through 8). Four interconnected pivot points 76, 78, 80 and 82 
are associated with the four link mechanism, which mechanism is 
collapsible and expandable along the horizontal axis 43 between pivot 
points 76 and 80. 
The four link mechanism 74 includes a slide rod link 84 slideably received 
along one end within the bore 53 in the integral axle 51 of the frame 41 
(FIGS. 4 and 5). The bore is coaxial with the X axis 43. The other end of 
the slide rod link 84 is bifurcated and has axially aligned openings 
adapted to receive a pivot pin 88 which allows pivotal movement about 
pivot point 80 (FIG. 8). Forward rod link 90 is connected to pin 88 
between the bifurcated arms of slide rod link 84, by a generally spherical 
bearing 91. The other end of forward rod link 90 is connected to pin 92, 
which defines pivot point 78, through a generally spherical bearing 93. 
Fixed rod link 94 is rigidly mounted on the rearward end 54 of the leading 
tow bar 49 and has a forked or bifurcated end pivotally mounted on pin 92, 
as seen in FIGS. 6 and 7. Therefore, pivot point 78 is fixed relative to 
the rearward end of the leading tow bar 40. 
A rearward rod link 96 is bifurcated so as to have two arms which are 
juxtaposed with the arms of the forked end of sliding rod 84 with the 
generally spherical bearing 91 of forward rod link 90 being centered 
therebetween (FIG. 8). The other end of rearward rod link 96 is pivotally 
connected by a cylindrical bearing to pin 98, which pin defines pivot 
point 82. Second fixed rod link 100 is rigidly mounted on the forward end 
50 of the trailing tow bar and has a forked or bifurcated end pivotally 
mounted on pin 98, as seen in FIGS. 6 and 7. There pivot point 82 is fixed 
relative to the forward end of the trailing tow bar. 
Pivot point 76 is located on and fixed relative to the vertical axis 47. 
Pivot points 78 and 82 are at fixed positions relative to the rearward end 
54 of the leading tow bar 40 and the forward end 50 of the trailing tow 
bar 40 respectively. Pivot point 80 moves along X axis 43, but is 
slideably connected by the rod link 84 to the frame 41 through the bore 
53. Therefore the four link mechanism 74 interconnects each part of the 
chain 32, vertical axle, frame and tow bars, so that pivotal movement of 
the tow bars about the Y axis 45 maintains the X axis 43 in a position 
bisecting an angle between the two tow bars. 
The geometry of the pivot points 76, 78, 80 and 82 (FIG. 6) is such that 
the distance between pivot points 78 and 80, and between pivot points 78 
and 76 is equal to the distance between pivot points 82 and 80, and 
between pivot points 82 and 76 respectively (FIG. 7). Any change of angle 
between one of the tow bars 40 and the X axis 43 is equalized by the four 
link mechanism 74 to the angle the other tow bar 40 makes with the X axis. 
The X axis 43 is automatically maintained by the link mechanism 74 along a 
line that bisects the angle between the two tow bars. 
If the X axis 43, which is coaxial with the rotational axis of the 
horizontal wheels 42, is positioned by the four link mechanism 74 so as to 
always bisect the angle between adjacent tow bars 40 interconnected by the 
link 38, then the X axis is always perpendicular to a line tangent to the 
curve of the chain rail assembly 34 through the single point 49, placing 
the horizontal wheels 42 in ideal position. This might be more clearly 
illustrated by imagining three successive links 38, represented by points 
49, which are connected by two equal length lines, representing the tow 
bars 40. A third line is constructed through the middle point 49 tangent 
to the curve of the chain rail. A fourth line perpendicular to the third 
line through point 49 will bisect the angle between the first two lines. 
It can be seen that if the wheels 42 were maintained on the fourth line, 
which wheels always rotate about the X axis 43, which axis would be 
perpendicular to a tangent line to the curve of the chain rail assembly 34 
at the point 49. 
In operation, as the preceding tow bar 40 passes into a horizontal turn, 
the link mechanism 74 moves the frame 41 to set the X axis 43, i.e. the 
rotational axis of the horizontal wheels 42, in ideal position besecting 
the angle between the leading and trailing tow bars. As the chain 32 goes 
through a horizontal turn, if the tow bars 40 on either side of the link 
38 form equivalent angles with the X axis 43 of the frame 41, then the X 
axis of the frame of the link must lie along a line perpendicular to a 
tangent of the horizontal curve at the point 49 the link is located along 
that curve. 
Adjacent tow bars are also aligned along the predetermined path by the four 
link mechanism 74. When universally connected to the link 38, the tow bars 
can pivot about Y axis 45 and get out of alignment with a trailing or 
leading tow bar 40, resulting in collapse of the chain 32. The link 
mechanism prevents this by properly positioning the X axis 43. 
Ideal position is not maintained for the vertical wheels 44. The vertical 
wheels 44 generally make an angle of 10 to 14 degrees with a tangent line 
to a curve of the chain rail assembly 34 when a vertical climb or descent 
is made and are not loaded while climbing or descending. Wear on the 
vertical wheels 44 is therefore not as great a factor as wear on the 
horizontal wheels 42. 
The chain 32 and connected tray 22 are driven by several drive systems 130, 
seen schematically in FIG. 1, located along straight runs of the trolley 
track 24. Generally, the drive system includes a continuous loop 132 of 
standard chain having projections 134 extending between rails 34a and 34d 
and 34b and 34c respectively to engage radially extending lug 48 which 
project between the rails 34a and 34d and 34b and 34c (FIGS. 1, 2, 4 and 
5). A motor 136 turns a sprocket 139 connected by the continuous loop to a 
second sprocket 138 to power the overall drive system. 
The lugs 48 are attached near the forward end 50 of the tow bar 40. To stop 
the chain 32, the drive system is halted, and a second set of projections 
135 of the drive system engages a lug 52, of reverse geometry to lugs 48, 
mounted at the trailing end 54 of the tow bars 40. 
In an alternative embodiment for maintaining the horizontal wheels 42 in 
ideal position, like parts being given prime suffixes, to the four link 
mechanism 74 (FIGS. 9 and 10) a trailing tow bar spring 108 is 
interconnected between a hinge 110 fixedly mounted to the tow bar 40' at 
forward end 50' and a hinge 112 rigidly connected to the frame 41'. In a 
similar manner, a forward tow bar spring 114 is interconnected between a 
hinge 116 rigidly connected to the rearward end 54' of the tow bar 40' and 
a hinge 118 rigidly connected to the frame 41'. The spring forces and 
lengths of springs 108 and 114 are equal, so that a set tension or 
compression force in spring 108 will be transferred across frame 41' to 
spring 114. The position where the springs are connected to the frame and 
two tow bars are equidistant from the X axis 43' and Y axis 45'. In a 
similar manner to the operation previously described the angle between the 
X axis 43' and the longitudinal axis of the leading tow bar 40' is 
transferred to the angle between the X axis 43' and the longitudinal axis 
of succeeding tow bar 40' to maintain ideal positioning of the frame 41'. 
FIGS. 11 and 14 show a construction for damping the automatic alignment 
system of the second embodiment utilizing springs 108 and 114. It is 
desired to damp the relative motion of the frame 41' about Y axis 45' 
relative to the forward end 50' of the tow bar 40' at the connection 
between the fork yoke 58' and the vertical axle 47'. 
A generally disc shaped cylinder 120 having a depending skirt is integral 
to the lowermost arm of fork yoke 58'. The cylinder has a center on Y axis 
45' and is rigidly connected to the vertical axis 47'. The cylinder 
extends radially away from the axle 47' and includes a circumferential 
volume 129 formed therein. 
The cylinder 120 is seated into a bearing plate 122 which extends radially 
outward from the frame 41' in the opening 46' beyond the diameter of the 
cylinder. A circumferential seal 123 between the cylinder and the bearing 
plate is formed by integral flange lips 124 and 125 of the bearing plate 
which extend upwardly either side of the depending skirt of the cylinder. 
The bearing plate 122 has a number of generally planar pistons 126 aligned 
along radii extending from Y axis 45' projecting into the volume 129 of 
the cylinder. The pistons are located at equally spaced intervals about 
the circumference of the bearing plate. The number of pistons depends on 
the spring force utilized, mass of the frame 41 and viscosity of fluid 128 
contained in the volume 129. The piston has a lower surface, an upper 
surface and four side surfaces. These surfaces of the piston are resisted 
by the viscous fluid 128 as the fork and connected cylinder move about Y 
axis 45' relative to the frame and connected bearing plate. The viscous 
fluid 128 fills the space between the volumes of the cylinder 120 and the 
pistons, a damping effect is created by the fluid contacting the various 
surfaces of the piston. 
Therefore, any outside force applied to horizontal wheels 42' will cause an 
oscillation of the frame 41' about the vertical axle 47'. The cylinder 120 
and piston 126 acting against the viscous fluid 128 will quickly damp 
these oscillations. The four link mechanism 74 does not allow any 
oscillatory movement of the frame 41 about the vertical axle 47, and 
therefore no such damping is required for the preferred embodiment. 
Though the abovedescribed invention has been described with a certain 
degree of particularity, nothing contained herein shall serve to limit the 
scope of the invention, particularly as described in the appended claims.