Electromagnetic switch for diverting objects in high speed conveyors

A pusher switch assembly for diverting pushers from a first path to a second path includes an electromagnet that when energized attracts a ferrous portion of selected pushers and disengages the selected pusher from the first path so as to divert it to the second path.

BACKGROUND OF THE INVENTION 
The present invention relates to conveyor systems capable of diverting 
objects from a high speed conveyor to one or more diverting conveyors and, 
more particularly, to conveyor systems with switch assemblies capable of 
diverting selected objects being carried at high speeds by the main 
conveyor to a diverting conveyor. 
In the quest for high speed sortation of packages and the like to various 
and different destinations, increasing use is being made of central or 
main conveyors coupled with bar code reading devices and with one or more 
diverting conveyors. As selected objects identified by the bar code 
readers approach a diverting conveyor path, object diverting shoes 
associated with the main conveyor are activated, move across the main 
conveyor path, and guide the selected objects to a selected diverting 
conveyor. The shoes move with the conveying surface but are caused by a 
switching mechanism, when activated, to slide across the conveying surface 
along a diagonal guide path toward a diverting conveyor. Various 
mechanically operated switches are typically used to cause the shoes to be 
diverted from a normal forward movement to move laterally across the 
conveyor path. At high conveyor speeds, the time window for the switch 
assembly to be activated and divert selected shoes to the diagonal guide 
path is very small, less than about 16 milliseconds. While there are 
mechanical movement switch assemblies that can accomplish this, such 
assemblies tend to be complex and expensive. Moreover, those assemblies 
add significantly to the noise of the conveyor operation because of the 
mechanical movement. 
It is therefore a paramount object of the present invention to provide for 
a simple switch that can be activated and deactivated well within the time 
window required by today's high speed sorting and/or diverting conveyors. 
It is still another important object of the present invention to provide 
for a switch usable with such conveyors but limiting the level of the 
noise added by the operation of the switch assembly and shoes. These and 
other objects will become apparent following a reading of the accompanying 
description and drawings. 
SUMMARY OF THE INVENTION 
The present invention pertains to a conveyor assembly that has a main 
conveyor and one or more diverting conveyors positioned at an angle with 
and intersecting the main conveyor. The assembly includes a plurality of 
article pushers operatively connected to components of the main conveyor 
and, in a non-diverting state, move with the main conveyor. The pushers 
are also able to move laterally across the main conveyor when placed in a 
diverting state. At least a portion of each pusher is comprised of 
ferromagnetic material. A first guide path, essentially parallel with the 
main conveyor, is in an operative relationship with the pushers and guides 
the pushers when in a non-diverting state. The assembly is also provided 
with at least one second guide path positioned at an angle with and having 
a first distal or receiving end positioned adjacent to the first guide 
path. A second distal or dispensing end of the guide path is positioned 
adjacent to the diverting conveyor. The second guide path has an operative 
relationship with a selected one or more of the pushers for guiding such 
pushers toward the second conveyor when the pushers are in a diverting 
state. A pusher switch is used to place the diverters in the diverting 
state and comprises an electromagnet that when energized attracts the 
ferrous portion of the pushers and disengages the pushers from their 
operative relationship with the first guide path and places the pushers 
into the operative relationship with the second guide path (the diverting 
state) whereby the pushers move parallel to the second guide path and push 
articles across the main conveyor to the diverter conveyor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Reference is initially made to FIGS. 1-4 and 6 for a general overview of a 
conveyor assembly incorporating the present invention. The main conveyor 
10 has a frame structure 12 including side rails 13 (best seen in FIG. 6), 
upright support rails 15, and cross rails 17 appropriately bolted, welded, 
or otherwise fastened together. The side rails 13 rotatably support a 
plurality of sprockets 14 that drive an endless chain 16 being 
appropriately shield on both sides of the frame structure 12 just inside 
the adjacent side rails 13. A plurality of flight tubes or rollers 18 are 
positioned between and rotatably attached to the flights of the endless 
chains 16, forming a conveying surface for articles that are being 
transported by the conveyor assembly. A plurality of article pushers or 
shoes 20 are mounted in a manner, described below, so as to normally move 
with the rollers 18, but when in a diverting state, are slidable relative 
to and laterally across the rollers 18. The conveyor assembly also 
includes at least one diverting conveyor 22 and, in many instances, one or 
more additional diverting conveyors 22a, to receive articles pushed 
laterally across the surface of conveyor 10 by pushers 20. 
The structure of the shoes 20 is best seen in the views of FIGS. 5 and 6. 
Shoes 20 include a wedge shaped pusher 24 that rises above the conveying 
surface defined by rollers 18 and functions to abut and move selected 
articles being conveyed by the conveying surface. A plurality of threaded 
bolts 28 extend from a recess 24a centrally located on each pusher 24 into 
the body of a pedestal support 26. Support 26 has a double concavity 26a 
adapted to compliment the surfaces of adjacent rollers 18 and hold the 
shoes 20 in place as the rollers 18 are being driven forward. The double 
concavity 26a further permits the shoes 20 to move laterally relative to 
the conveyor path when the shoe 20 is not otherwise constrained against 
such movement. A guide pin 30 is bolted to pusher 24 between bolts 28 in 
recess 24a and extends downwardly terminating in a free distal end 30a. A 
wheel bearing member 32 is rotatably mounted on pin 30 at a position 
intermediate the distal end 30a and the bottom of the pedestal 26. Pushers 
24 are typically formed from a material such as urethane while the 
pedestals 26 may comprised of a material such as delrin. The guide pins 30 
are preferably formed from cold-rolled steel, a ferromagnetic material, 
while the wheel bearing member 32 may be made from a delrin-like material 
also. 
As best seen in FIG. 8, a pair of guide rails or channels 34 and 35 are 
appropriately bolted at intervals to frame structure 12 on each side of 
main conveyor 10. Each channel 34 and 35 has a sectional shape with 
respective upright interior and exterior walls 34a, 34b and 35a, 35b 
(shown in FIGS. 8a and 8b, respectively) defining the channel 
configurations into which the distal end 30a extends, thus preventing the 
shoes 20 from moving laterally across the conveyor width when the system 
is in a non-diverting mode. In such non-diverting mode, the shoes 34 
continuously move along that side of the conveyor in a line as shown in 
the bracketed portion depicted by character numeral 38 in FIG. 1. 
To provide for diversion of packages, the conveyor assembly has one or more 
angled guide rails 36 secured to the frame structure beneath rollers 18. 
The rails 36, best illustrated in FIGS. 3 and 7, are positioned at an 
angle 37 at no more than about 20.degree. to the direction of conveyor 
movement. The receiving end 40 of guide rails 36 are positioned close to a 
shoe switching station 42 while the other or dispensing end 43 is 
positioned near the shoe switching station 44. In the sectional view of 
FIG. 8, it may be seen that each angled guide rail 36 takes the form of a 
right angle bracket with an upright arm 36a serving as a bearing surface 
for the wheel bearing member 32 of each shoe 20 that has been diverted 
from its normal conveying path along guide channel 34. 
To best describe the specifics of the shoe switching station 42, reference 
is made to FIGS. 8a, 8c, 9 and 10. The support structure for the switching 
station 42 is a plate 46 (FIG. 9) secured to the assembly frame below 
rollers 18. A bracket 48 is mounted to the plate 46 and can be adjusted to 
move horizontally toward and away from the adjacent guide channel 34. A 
set screw 49 provides for fine adjustment of the bracket 48. An 
electromagnet 50 is bolted to the horizontally movable bracket thereby 
providing for relative movement between channel 34 and electromagnet 50. 
While the internal structure of the electromagnet is a matter of choice, 
the electromagnet 50 may comprise a pair of upper and lower, spaced plates 
50a and 50b as seen in FIGS. 8a and 8c. The plates are made of 
ferromagnetic material between which are positioned the energizing coils 
(not shown). The space between the plates 50a and 50b may be filled with 
an epoxy material to make the magnet a single unit. The edges of plates 
50a and 50b define a diverting surface 52 facing the pins 30 of the 
passing shoes 20 and form a part of the channel guide 34. Specifically, 
the diverting surface 52 has a flat portion 52a that interrupts a portion 
of the interior upright channel wall 34a of the channel 34 and forms with 
the exterior upright channel wall 34b that portion of the channel 34 
facing the electromagnet magnet 50. Surface 52 additionally has a curved 
portion 52b with a predetermined radius of curvature that curves away from 
the channel 34 toward the cross guide rail 36 and finally a second flat 
portion 52c that is essentially parallel with rail 36. A sensing element 
54 is positioned near, but "upstream" from, electromagnet 50. The distance 
of sensing element 54 from the magnet is adjustable along a slot 55a in 
the plate 55 bolted to support plate 46. When the electromagnet is 
energized, the ferrous material comprising the pin 30 is attracted by the 
ensuing magnetic field and causes the pin to abut and follow the surface 
52 along portions 52a, 52b, and 52c until surface 52 terminates. A wedge 
shaped channel separator or divider 56 secured to the frame 12 functions 
to provide continuity to channel 34 on one side and, collectively with the 
surfaces 52b and 52c, to define an angled channel for the pin 30 attracted 
by the energized electromagnet 50. Movement of the electromagnet 50 
through adjustment of set screw 49 allows for fine adjustment to the 
magnitude of attraction of the electromagnet to the ferromagnetic material 
of the pins 30 as desired. When the pin 30 leaves surface 52, divider 56 
continues to guide the pin 30 to the start of cross rail 36. As perhaps 
best seen in FIG. 9, the divider 56 and rail 52 overlap slightly. At this 
point, the wheel bearing member 32 abuts the cross guide rail 36 and the 
shoe 20 follows rail 36 across the conveyor path. This sequence can best 
be understood by a review of the movement illustrated in the schematic of 
FIG. 11. 
The radius of curvature of the curved surface part 52b plays a significant 
role, particularly at the upper range of speeds of the conveyor. An abrupt 
change of direction of a diverted pusher is not desirable because of the 
resulting noise and wear and/or structural damage that occurs to the pins 
30, bearing members 32, and rails 36 over time. Thus, by providing a 
curvature that guides the movement of the pin 30, the pin 30 moves from 
the direction imposed by guide channel 34 to the direction provided by 
rail 36 in a graduated manner. The radius of curvature required is 
dependent to a large degree on the conveyor speed and strength of the 
electromagnet. As a general rule, small radii of curvature require larger 
electromagnetic forces to counter the higher centrifugal forces of the pin 
moving in the tighter curve path. On the other hand, larger radii of 
curvature increase the total switching time. Applicant has found that a 
radius of curvature of between four to sixteen inches is sufficient for 
most applications. 
During its lateral movement, each shoe 20 experiences an increase in its 
velocity since the vector component in the direction of the movement of 
the conveyor remains the same. For this reason, large angles of diversion 
are not desired for high speed conveyors. Similarly, a significant impact 
can occur at the far side of the conveyor near the diverting conveyor 
where the shoe 20 is returned to the normal path parallel to the flow of 
the conveyor. The impact undesirably increases the operation noise, 
damage, and wear to a considerable extent. It is preferable to use a 
second switching station 44 that operates essentially the same as the 
first switching station 42 to receive shoes 20. Receiving switching 
station 44 may, however, employ a more gradual radius of curvature for 
guide surface 60. The field created by the electromagnet 58 attracts the 
pin 30 against surface 60 leaving the dispensing end 40 of guide rail 36 
where it follows the curvature of surface 60 to the far side guide channel 
35. Because the pin 30 does not impact against channel 35, but follows 
surface 60 into the channel, large impact noises are avoided. Since the 
receiving switching station 44 does not have to be selective, the 
electromagnet 58 may remain energized continuously during the entire 
conveyor operation. Like the electromagnet 50 of the first switching 
station 42, electromagnet 58 is horizontally adjustable relative to the 
side guide, i.e., channel 35, through a slidable plate 61 and a set screw 
63. 
When the rollers 18 and shoes 20 are moved around the end sprockets 14 
underneath the conveyor 10, those shoes 20 that were directed to the guide 
channel 35 must be laterally moved again to guide channel 34 before the 
rollers 18 reappear again to form the conveying surface for articles. As 
shown in FIG. 4, a single angled guide rail 62 having a structure similar 
to or identical to the structure of rail cross guide rails 36, may be used 
along with electromagnetic switching stations above to lessen impact 
noise. However, it should be understood that since no rapid diversion of 
articles is required, switching does not have to accomplished with the 
same rapidity and no selectivity is required. 
As stated above conveyor speeds of up to 600 feet per second may be used. 
Thus, the window for diverting the path of an article is typically quite 
small, e.g., on the order of five to sixteen milliseconds. Accordingly, 
the decision to divert must be made at some time interval prior to the 
energization of the electromagnetic switch at the chosen switching 
station. The flow diagram and schematic of FIG. 12 illustrates one example 
of a control system that may be used with the electromagnetic switching 
stations. In this example, a determination is made that all packages 
entering the main conveyor 10 with a code ABC are to be diverted to the 
conveyor 22 and all packages with a code XYZ are to be diverted to the 
conveyor 22a. This information is encoded at user input station 64 into a 
controller such as a computer 66. The computer 66 also receives inputs as 
to conveyor speed, package size, and other such parameters. The entry of a 
package into the conveyor is sensed by a sensor 68, such as a photocell, 
and relayed to the computer 66 so that the package position is known. A 
reader 70, such as a bar code reader, determines whether or not the 
package bears the codes ABC or XYZ. The adjustable sensor 54 positioned 
just upstream of the electromagnet of switching station 42 senses and 
counts the passage of the pushers and provides a running count to the 
computer 66. When the appropriate and predetermined count is reached, the 
electromagnet of switch station 42 is energized prior to the moment when 
the package bearing the code ABC reaches station 42. The electromagnet of 
switching station 42 is continues in an energized state for a 
predetermined time interval necessary for the appropriate number of shoes 
20 to be diverted and engage the article or articles. The diverted shoes 
20 move along the cross guide 36, thereby pushing the package in that 
direction toward switching station 44 and conveyor 22. At switching 
station 44, the diverted shoes are guided into guide channel 35, parallel 
to the main conveyor path. Packages bearing the code XYZ are similarly 
diverted at switch 42a toward conveyor 22a. All other packages continue 
along the main path of the conveyor 10. 
It should be understood from a reading of the above that a portion of the 
shoe must be comprised of a ferrous material that is attracted by the 
electromagnet. Preferably the guide pin of the shoe includes ferrous 
material. An alternate structure for a pin is shown in FIG. 13 in which 
the pin 30 comprises a steel core 72 clad by a layer of bearing material 
73 followed by roller 75 made of a ferromagnetic material. The additional 
ferromagnetic material increases the attraction between the electromagnet 
and the pin 30. Still another alternative structure for the pin 30 is 
shown in the views of FIGS. 14a and 14b in which the pin 30 is provided 
with a flange or "flag" 74 that is made of ferromagnetic material. The 
flag 74 flag the pin 30 and projects behind the pin 30 within the channel 
guide 34 and increases the effective attraction of the pin 30 to an 
electromagnet of a switching station. 
The present invention as described above, accompanied by the various 
figures addresses the objects and provides for solutions to problems posed 
by the high conveyor speeds and accompanying noise levels. Those with 
ordinary skill in the art will be able to devise changes and modifications 
without departing from the scope of the appended claims.