Note: Descriptions are shown in the official language in which they were submitted.
33
BACKGROU~D OF THE INVENTION
In automatic picker systems, horizontal floor space is at a
premium, so that it is desirable to store articles in a vertical
direction, but as the angle of storage is increased, the problems
associated with stacking articles in the storage area correspond-
ingly increase particul~rly due to problems o~ velocity control
and impact control.
There is ~ well known need to transport articles between
different levels, and many types of conveyors, both powered and
gravity operated, are known for this purpose.
In this article transport fieldJ powered transfer conveyors
can control the velocity and impact o~ articles quite well, but
usually in correlation to the expense involved in manufacture,
maintenance and desi~n. Gravity conveyors have the extreme
problem of runaway velocity that will damage articles or adjacent
machinery when a moving article hits a stationary article.
Various types o~ retarders or slow moving conveyors solve the
velocity and impact problems, but in turn they produce the
problems o~ low volume flo~, that is they will have an undesirably
low transfer capacity per unit of time.
SUMMARX OF THE IN~VENTION
It is an object of the present invlention to provide a
transport device of the type discussed, without the disadvantages
of the prior art. Particularly, a transport device is provided
to move and store articles vertically with a low initial cost,
low maintenance cost, and simplicity of operation as compared
with the prior art, while at the same time providing for a high
volume ~low rate, low impact shock for articles, automatic control,
reliable speed control throu~hout movement that varies according
to the number of articles already stored in the device.
- 2 ~
BRIEF DESCRIPTION OF THE DRAWING
Further objects, features and advantages of the present
invention will become more clear from the following detailed
descrip~ion of a preferred embodiment as shown in ~he
accompanying drawing, where m:
~ IGURE 1 is a partially schematic, partially cross sectional,
side elevation view o~ apparatus ~mbodying the present invention;
FIGURE 2 is a cross sectional view taken along line II-II;
FIGURE 3 is a plot of acceleration versus distance ~rom the
point of free fall to the point of i.mpact with the downstream
stationary article; and
FIGURE 4 is a plot of velocity versus the distance
corresponding to Figure 3.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
_
In Figure 1, there is shown a gravi~y transport device for
moving a plurality of substantially identical articles la-le from
a first upper station 2 to a second lower station 3. A suitable
conveyor, such as endless conveyor 4 7 will feed articles, such as
article le, at the first station 2. The conveyor 4 comprises a
drive sprocket 5, a belt 6, an idler sprocket 7, and a motor 9,
for driving the conveyor belt 6 in the direction of the arrow to
move the article le into the inclined feed 8 of a chute 10. The
inclined loading surace of the inclined eed 8 is sloped with
respect ~o the horizon~al at an an~le ~, which is pre~erably
15 degrees, and the upper wall is slightly flared outwardly
toward the article le with respect to the lower wall, so as to
guide the ar~icle leinto the entrance end ll of the chutelO. As
seen in Fi~ure 2, the chute 10 has a cross sectional shape that
is complementary tn the corresponding cross sectional shape of
the article le, so that there is a small uniform clearance between
the article and the chute. The`chute 10 has such a uniform cross
section throughout its entire extent from its en~rance end 11, to
its exit end 12. Thus, the chute defines a central axis of
symmetry, which would be perpendicular to Figure 2 and which in
Figure 1 is vertical. While vertical is preferable, any vertical
extent may be used so long as there is sufficient slope with
respect to the horizontal to provide for gravity feed of articles
travelin~ through the chute.
It is desirable ~o have the chute near true vertical,
'~0 because it will take up less valuable horizontal space ~han if
it were inclined more to the horizontal and provide for faster
feeding of articles into the chute. The side walls of the chute
are continuous and air impervious, so that when combined with the
complementary telescoping shape of the chute and articles 1, the
article ld traveling in the chute will function as a piston pump-
ing air in front of it to increase the pressure of air in front
of the falling article ld to a pressure that is greater than the
air behind the article ld. In this sense, the walls are air
impervious, although it is understood that assembly techniques
and manufacturing tolerances can produce air leakage that is
tolerable and vents may be deliberately provided along the length
of the chute for speed control, while stlll considering such
walls air impervious in the sense that the above-mentioned pump-
ing action will occur and the speed control to be discussed
below will result.
At the entrance end 11, a light source 13 powered by a
battery 14, or the like, will pass a beam across the chute to a
photocell 15 for producing a signal that is sent to the control 16.
When the light beam from source 13 is broken by an article, the
signal will be interrupted to the controller 16, and if the
signal is interrupted ~or longer than a fixed period of time that
would indicate the interrupting article is stationary, the
controller 16 will produce a control signal in the line 17 to
stop th~ feed motor 9, to correspondingly stop the feeding of
further articles into the entrance end of the chute, because the
chute would be fully loaded or at capacity.
Spaced at a greater vertical distGance than the corresponding
vertical height of the article la from the exit end 12 of the
chute, there is a support surface 18, on which rests the lower-
most or first article la. Thus, it is seen that the top surface19 of the article la is spaced slightly, for exa~ple 1/8 o~ an
inch, below the bottommost surface of the chute lQ. An article lb
rests upon the top of article la, ~nd extends sufficiently far
into the exit end of the chute 10 that it will effectively
pneumatically séal off the exit end of the chute. A light source
20, powered by a battery or other electrical source 21 produces
a beam of light that will travel across the chute 10 to be
intercepted by the photocell 22, to produce a signal in line 23
that ~ill be received by the control device 24. When an article
intercepts this beam of ligh~ for more than a fixed period of
~, time to indicate that the article is stationary, the controller 24
will produce an output signal in line 25 to operate solenoid 26
for ohanging three-way valve 27 to its illustrated position
wherein fluid, particularly hydraulic fluid fr~m the sump 28 m~y
be moved by p~p 29 through the valve 27 to line 30, through
open valve 31 to the expansible ch~mber device 32 that will
reciprocate ram 33 laterally of the chute axis to slide the
article la from beneath the article lb and onto an endless
conveyor 33, driven by motor 34, so that the conveyor 33 may
move the article to a desired location in a.dir~ction perpendicu-
lar to the plane of Figure l. Thereafter, a suitable controlsignal is provided in line 35, for example under the actuation
of a limit switch associated with the ram 33, so as to operate
solenoid 36 to close the ~alve 31, vent the expansible chamber
device 32 and withdraw the ram 33 to its illustrated position
under the power o~ a return spring (not shown) in ~he expansible
chamber device 32; at this time, the articles lc and lb will move
downwardly so that the article lb will res~ upon the support
- surface 18. Assuming that the article ld is still ~alling, the
photocell 22 will produce a signal in line 23 that will indicate
the absence of an article adjacent it, ~nd the control 24 will
produce a signal in line 25 ~o operate the solenoid 26 so as to
move valve 27 from its illustrated position to an exhaust posi-
tion for the line 30 so that regardless of the operation of
valve 31, the expansible chamber device 32 cannot be actuated to
remove the lowermost ar~icle; in this manner, there is an inter-
lock provided to prevent the removal o~ an article in the
position lb as the topmost stationary article, so that the
pneumatic seal for the exit end 12 of the chute will always be
maintained~ .
The apparatus of Figure 1 may be operated by itself merely
as a transpor~ device with some inherent stora~e, or may be
operated by itsel~ as a picker device that will vertically store
articles to be removed as needed, or operated in conjunction with
a plurality of such chutes lOa, lOb, and lOc to provide multiple
storage facilities as is well known in storage pickers. Theside elevation view of each o~ the chutes lOa, lOb, lOc would
include equipment such as all of that illustrated in Figure 1,
and if desired the internal shape of the chutes lO, lOa, lOb, lOc,
etc., may b~ different to store and transport correspondingly
differently shaped articles, but in any event the shape is
complementary to the article to be carried in the chute with
small clearance so as to produce the p~npin~ effect.
Thæ detectors that are constituted by the light source-
photocell combinations may be omitted if this control is not
needed, although it is desirable to include the lowermost
detector even if manual picking is employed, that is, even if
the ram 33, power cylinder 32, mechanism were removed, and in
such case the si~nal in line 23 would then produce an audible
or visual signal to indicate to the manual picker that the lower-
most article should not be removed, or such si~nal may be used
to place a barrier against the manual removal of the lowermostarticle. Of course, articles may be manually fed into the
entrance end 11, and if desired the inclined feed may be omitted,
since it merely serves the function of insuring proper positioning
of the article in the entrance end 11.
When an article is first inserted in the entrance end 11 of
the chute 10, the pressure on the upper surface of the article
~ill substantially balance the pressure on the lower surface of
the article so that the article will freely ~all, when released,
with the normal acceleration of gravity that is 32.2 feet per
second per second. In Figure'3 and ~i~ure 4, the distance is
plotted starting from the'far left-hand position corresponding
to the point where the'article is released in the entrance end 11,
that is point D and is measured vertica]ly along the axis of the
chute and plotted towards the'right in these ~igures to point C
which is the point where the'falling article comes to rest on the
immediately adjacent lower stationary article. Thereore, this
distance D-C will vary according to the'height of stationary
articles stacked within the chute,' ~nd of course in accordance
with the actual height of the chute, but the'profile curves for
the acceleration and velocity will correspondingly vary, that is
they will be similar regardless of thé to~al distance. As seen
in Figures 3 and 49 when the article is first released at the
entrance end 11, point D, the'acceleration will have a positive
value of 32.2 feet per second per second and the velocity will be
zero. From po-int 0 to point A, the article will have a
substantially steady acceleration equal to the acceleration of
gravity, that is 32.2 eet per second per second as its velocity
increases. Thereafter, the pressure'will begin to build up in
front of the falling ar~icle due to the pumpin~ effect of the
,
article acting as a piston within the chute acting as a cylinder
so that pressure in front of th~ article will begin to increase
with respect to th~ pressure behind the falling article and
accordingly the acceleration will continuously decrease from
point A to point B while the velocity continues to increase. At
point B, the acceleration will be zero and the velocity will be
at a maximum. ~oving past point ~, the pressure will continue to
build up in front of the article so that the acceleration will be
negative, that is, there will be deceleration and correspondingly
the velocity will steadily decrease as the falling article moves
from point B to point C. At poin~ C, the falling article will
impact with the nex~ lower stationary article lc, at which time
the acceleration will substantially instantaneously return to
zero and the velocity will su~stantially instantaneously return
to zero. From Figure 4, it is seen that at the moment of impact
at point C, there will be a small terminal velocity E for the
falling article, which will be its velocity at impact. By
controlling the tolerances between the chute and the article,
this terminal velocity can ~e made quite small and in fac~
smaller than the terminal velocity of the article lb moving from
its illustrated stationary position to where it impacts with the
support surface 18 after the ar~icle la is removed and the ram 33
is returned to its illustrated position, which of course would
result in no damage to the article. In ~ny event, it is critical
to control the mating configuration between the chute and
the article, and the exit end of the chute remain sealed by an
article, or other means,so that the pumpin~ ~ction will occur
sufficiently to build up pressure in front of the falling article
so that deceleration will occur for a period of time immediately
before impact sufficient to produce an acceptable terminal
velocity.
~rom the above, it is seen that as the hei~ht of the
stationary articles increases, the points B and C will
correspondingly move upwardly in the chute, so that the speed
control is self regulatin~ to the extent tha~ it will operate
substantially the same regardless of the hei~ht of free fall.
Furthermore, it is seen that the speed control will permit
maximum acceleration of the article and the very rapid reaching
of a high transport speed, and thereafter the controlled
deceleration sufficient to provide the desired impact terminal
velocity. In this manner, the input feed rate from conveyor 4
may be very high and the volume flow handling capability of the
transport device can correspondingly be very high and limited
to no more extent than discharging articles into a totally
vertically aligned free fall without a chute. Even i~ several
articles are falling within the chute at the same time, it is
seen that as a lower one of the falling articles slows down, the
immediately upstream falling artic~e will start to move closer
to the downstream article and thereby build up pressure between
the two to control the approach velocity of two ~alling objects
in a manner similar to that shown in ~igures 3 and 4 with respect
to producing a relative deceleration of approach between the two
articles.
While a preferred embodiment of the present invention has
been described in detail as the best mode and for the advantages
of the specific details, further embodiments, modifications and
variations are contemplated according to the broader aspects of
the present invention, all as determined by the spirit and scope
of the following claims.
