CA1044718A - Stack-height responsive sheet stacking system - Google Patents
Stack-height responsive sheet stacking systemInfo
- Publication number
- CA1044718A CA1044718A CA270,337A CA270337A CA1044718A CA 1044718 A CA1044718 A CA 1044718A CA 270337 A CA270337 A CA 270337A CA 1044718 A CA1044718 A CA 1044718A
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- Canada
- Prior art keywords
- lift head
- carriage
- stack
- lift
- head
- Prior art date
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Abstract
ABSTRACT OF THE DISCLOSURE
A material handling machine having a laterally shiftable, elevated carriage on which a vertically shiftable lift head is mounted is provided with controls which operate the machine to automatically perform multiple functions. A
particularly significant control feature permits lifting the material to only the minimum height required to clear a stack of material on which the material is being stacked in response to the height of the stack. The picked up material is then carried laterally to a predetermined point above the receiving stack and lowered onto the stack or other receiving surface in response to the actuation of a control switch by the carriage when it reaches the predetermined point.
A material handling machine having a laterally shiftable, elevated carriage on which a vertically shiftable lift head is mounted is provided with controls which operate the machine to automatically perform multiple functions. A
particularly significant control feature permits lifting the material to only the minimum height required to clear a stack of material on which the material is being stacked in response to the height of the stack. The picked up material is then carried laterally to a predetermined point above the receiving stack and lowered onto the stack or other receiving surface in response to the actuation of a control switch by the carriage when it reaches the predetermined point.
Description
B
This is a divisional application of Canadlan Applicatlon No. 190,812 filed on January 24, 1974.
The material handling machine of this invention has been designed and bullt with a view towards automatically handling material, particularly sheet material, with maximum efficiency ln the course of ~
the multiple steps of picking up pieces of material from a supply station, ~ ~ -moving laterally with the material and depositing :it at a predeterl~ined location at a receiving or stacking station.
These basic objectives have been realized by utili2ing a horizontally shiftable carriage on an elevated guide track, mounting a vertically shiftable lift head with materlal pickup means on the ; `
carriage and provlding controls to automatically operate the carriage and lift head to carry out the aforesaid materlal handl:lng steps.
A partlcularly advantageous control feature of the machine resides in the use of a lift head lowering control which is responsive to the generation of slack in the lift head drive mechanism when the lift head strikes a contact surface, to thereby stop the lift head downward stroke immediately to avoid damage to the machine and to the material being handled. In the preferred form of the machine a chain drive operated by a power cylinder is utilized to raise and lower the lift head, and when the lift head strikes a contact surface, a spring acting o~ one end of the drive chain shifts the slackened chain to carry a trip device attached to the chain in~o contact with the actuator of a control switch which then operates to stop the downward movement of the lift head.
~s a further beneficial feature of my material handling machine, I provide it with a multiple pickup control function in accor-dance with which the lift head of the machine is lowered to pick up material from a receiving bed only after a predetermined length of material has accumulated on the bed. This is preferably accomplished by .. - . ~ : .
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locating a control device, such as a photoelectric cell, adjacent the receiving bed in front of a material stop a predetermined distance sub-stantially e~ual to the total length of material desired to ~e picked up.
The control operates in response to the presence o.E material on the receiving bed at the control location for a predetermined period of time to actuate the lift head on its downward stroke to pick up the material accumulated on the receiving bed between the stop and the control device.
A height control function is incorporated ln the machine and utilizes a sensing device responsive to the height of a stack of ~aterial on which the machine is placing pieces of material to terminate the upward movement of the llft head with a piece of material at a supply station when the lift head reaches a level above the height of the material stack. This eature eliminates unnecessary elevation o the ;~
lit head and initiates the lateral movement o the lit head to the stacking station at a point above the material being stacked when the lit head has risen high enough to clear the stack on which it must deposit the piece o~ material it has picked up at the supply station.
These and other objects and beneflts o~ my invention will become readily apparent as the following description is read in conjunction with the accompan~ing drawings wherein like reference numerals have been used to designate like elements throughout the several views.
Figure 1 is a perspective view of the material handling machine of this invention;
Figure 2 is a hori~ontal section view taken along lines
This is a divisional application of Canadlan Applicatlon No. 190,812 filed on January 24, 1974.
The material handling machine of this invention has been designed and bullt with a view towards automatically handling material, particularly sheet material, with maximum efficiency ln the course of ~
the multiple steps of picking up pieces of material from a supply station, ~ ~ -moving laterally with the material and depositing :it at a predeterl~ined location at a receiving or stacking station.
These basic objectives have been realized by utili2ing a horizontally shiftable carriage on an elevated guide track, mounting a vertically shiftable lift head with materlal pickup means on the ; `
carriage and provlding controls to automatically operate the carriage and lift head to carry out the aforesaid materlal handl:lng steps.
A partlcularly advantageous control feature of the machine resides in the use of a lift head lowering control which is responsive to the generation of slack in the lift head drive mechanism when the lift head strikes a contact surface, to thereby stop the lift head downward stroke immediately to avoid damage to the machine and to the material being handled. In the preferred form of the machine a chain drive operated by a power cylinder is utilized to raise and lower the lift head, and when the lift head strikes a contact surface, a spring acting o~ one end of the drive chain shifts the slackened chain to carry a trip device attached to the chain in~o contact with the actuator of a control switch which then operates to stop the downward movement of the lift head.
~s a further beneficial feature of my material handling machine, I provide it with a multiple pickup control function in accor-dance with which the lift head of the machine is lowered to pick up material from a receiving bed only after a predetermined length of material has accumulated on the bed. This is preferably accomplished by .. - . ~ : .
~l`o~
locating a control device, such as a photoelectric cell, adjacent the receiving bed in front of a material stop a predetermined distance sub-stantially e~ual to the total length of material desired to ~e picked up.
The control operates in response to the presence o.E material on the receiving bed at the control location for a predetermined period of time to actuate the lift head on its downward stroke to pick up the material accumulated on the receiving bed between the stop and the control device.
A height control function is incorporated ln the machine and utilizes a sensing device responsive to the height of a stack of ~aterial on which the machine is placing pieces of material to terminate the upward movement of the llft head with a piece of material at a supply station when the lift head reaches a level above the height of the material stack. This eature eliminates unnecessary elevation o the ;~
lit head and initiates the lateral movement o the lit head to the stacking station at a point above the material being stacked when the lit head has risen high enough to clear the stack on which it must deposit the piece o~ material it has picked up at the supply station.
These and other objects and beneflts o~ my invention will become readily apparent as the following description is read in conjunction with the accompan~ing drawings wherein like reference numerals have been used to designate like elements throughout the several views.
Figure 1 is a perspective view of the material handling machine of this invention;
Figure 2 is a hori~ontal section view taken along lines
2-2 of Figure 3 and showing the laterally shiftable carriage of the machine;
Figure 3 is a side elevation view of the machine o ~igure 1 performing a material stacking function;
Figure 4 is a fragmentary, side elevation view o~ the machine of Figure 1 taken from the opposite side of -the machine from 7~
that shown in Figure 3 and illustrating the mechanism for raising and lowering the lift head;
- Figure 5 is a fragmentary, left end elevation view of the machine shown in Figure l;
Figure 6 is a control diagram illustrating the various : :
con~rol steps of the machine; . ;
~: .
Figure 7 is a top, plan view of a receiving bed with ,, ~.
controls mounted thereon for controlling the total length of accumulated .. ~
~ . .
material which the machine picks up at one time;
Figure 8 is a front, elevation view of the receiving bed and controls shown in Figure 7, and ~ igure 9, located on the same sheet as Figure 1, is a plan v~ew o the base of the machine in Figure 1.
Re~erring now to the drawing, I have shown in Flgure 1 a prePerred embodiment of my material handling machine having an elevated ~ .
support boom 1 in the fonm of an I-beam mounted on an upright pedestal 2.
Guide tracks 4 and 6 extending longitudinally along the top and bottom faces of I-beam 1 serve to shiftably support and guide a carriage 8 ~`
which is laterally shiftable back and forth on boom 1. Carriage 8 may !' be shiftably supported on guide tracks 4 and 6 in various ways for sliding ;~ :
or rolllng support thereon. For il:Lustratlve purposes, as most clearly appears in Figure 5, I have utilized rollers for this purpose. An upper ~ YOller~
A set o~ r~ 9 and 10 attach to a horizontal extension 12 of carriage 8 engage the top and rear, side faces of upper guide track 4; and a : :~
bottom roller 14 engages the front ~ace of lower guide track 6.
It will be appreciated that various types of reversible -:
motor means may be utili~ed to move car~iage 8 back and forth on the ~:
guide tracks 4 and 6 o~ boom 1. I have found that a pneumatic cylinder is particularly suitable for this purpose, such a cylinder and its associated piston being designated by reference numerals 16 and 18 in .:, .. . . . . ... .
Figures 2 and 3. The mounting and drive arrangement of cylinder 16 with respect to carriage 8 may best be understood by re~erence to Figures 1 through 3 and 5. Pneumatic cylinder 16 is mounted on the vertical web la of I-beam l as shown in Figure 5, and a bracket 20 attached to piston ~ -18 is secured to an elongated cable 22 guided around sheaves 24 and 26 rotatably supported on vertical axes mounted within the slotted ends of beam web ~a in the manner shown in Figure 1. The ends of cable 22 are secured to a rearward extension 8a of carriage 8 by means of brackets 27 and 28 attached to the opposite sides thereof. The flow of pressurized air to the opposite ends of pneumatic cylinder 16 to reciprocate piston 18 in opposite directions is controlled by a pair of control devices in the form of solenoid valves S-l and S-2.
A lit head generally indicated by rePerence numeral 30 is mounted on carriage 8 for lateral shifting movement therewith by vertically reciprocal carrier means. I have found it particularly ad-vantageous to utilize a carrier means as shown comprised of a plurality of extensible and retractable lift beams 32, 34 and 36 which slidably support each other, and which are driven by a chain drive arrangement hereinafter described to provide a mechanical lift advantage. The lit apparatus may best be understood by reference to Figures 1 and 4. Upper lift beam 32 is ixed at its bottom end to horizontal plate 8b of carriage 8 and slidably supports beam 34 by means oP a slide head 38 on the upper end of lift beam 34 which embraces lift beam 32. A similar slide head 40 is mounted on the bottom end of lift beam 34 and slidably supports and guides bottom lift beam 36. At its lower end, lift beam 36 is secured to cross beam 42 of lift head 30. For the purpose of raising and lowering lift beams 34 and 36, I utilize bi-directional drive means in the Porm o~ a pair of drive chains 44 and 46. Chain 44 is fixed at one end to a spring biased rod 60 extendlng through base plate 8b of carriage 8. The opposite end of chain 44 is attached to slide head 38, ~ ~4~718 wlth chain 44 being guided around a pair of sprockets 47 and 48 mounted on a bracket 50. Chain 46 is guided around a sprocket 51 attached to -slide head 38 and is affixed at one end to base plate 8b of carriage 8. ~ ;
At its opposite end, chain 46 is attached to lift head 30. As may be noted with respect to the showing of chain 46 in Figure 1, both chains 44 and 46 may be double chains guided around a pair of sprockets. As a source of power for driving chains 44 and 46, I utili7e a reversible, double-acting pneumatic cylinder 52 having a reciprocating piston 54 attached at its upper end to mounting bracket 50 on which sprockets 47 and 48 are mounted. The flow of pressurized air to opposite ends of cylinder 52 to reciprocate piston 54 upwardly and downwardly is controlled by a pair of solenoid valves S-3 and S-4.
For the purpose of precisely controlling the downward stroke of lift head 30 so that it will stop immediately upon contacting a sur~ace of any kind, X utilize a control switch designated L-7 having a trip arm 56 disposed in proximity to one end of chain 44. The end of chain 44 near switch L-7 carries a trip bar 58 for act~ating arm 56 of switch L-7. That same end of chain 44 is attached to a rod 60 which extends through base plate 8b of carriage 8 and is normally biased in a downward direction by a coil spring 62 on its lower end. It will be apparent that the load of lift beam 34 and lift head 30 normally acting downwardly on one end of chain 44 will keep chain 44 in tension, with the result that spring 62 will be compressed in a normally loaded condition by the upward force of segment 44a oi chain 44 acting through rod 60. This will cause trip bar 58 to be held at a normal, elevated position out of contact with arm 56 of switch L-7. There is enough "free play" or slack between drive chains 44, 46 and the lift beams 34 and 36 to which they are attached that when lift head 30 engages a contact surface on its downward stroke to thereby remove the tension . ' '~' ' . . ' ' :
.::- , .
7~
stress normally exerted on chains 44 and 46 by the weight of the lift head and the lift beams, chain 44 will be freely movable through a limited distance by the unloading action of spring 62. Spring 62 bears against the bottom base of carriage base plate 8b, and as it unloads downwardly, it will take up any slight slack generated in chain 44, and thereby urge chain segment 44a downwardly. As chain 44a is shifted downwardly, trip -bar 58 carried thereon will engage and trip actuating arm 56 of control swltch L-7. When this happens, actuating arm 56 of switch L-7 will be shifted downwardly to the position shown in Figure 4 w~erein it opens the contacts leading to solenoid valve S-4 and thereby shuts off the supply of pressurized air to the upper end of cylinder 52 to stop the downward stroke oE piston 54. Thls will oE course immediately terminate the downward movement of chalns 44 and l~6, and thus immediately stop the downward stroke of llft head 30 upon contact with a surface of any klnd.
When switch L-7 is actuated in the aforesaid manner, it simultaneously closes the contacts completing a circuit to solenoid valve S-3 to ready lift cylinder 52 for the upward stroke of piston 54 and the elevation o~ lift head 30.
It will be appxeciated from the foregoing description of the lift apparatus, that the use of at least one drive chain 44 or 46 in combination with power cylinder 52 provides a mechanical advantage with respect to the vertical movement imparted to lift head 30 by a particular displacement of piston 54 of cylinder 52. With chain 44 guided around sprockets 47, 48 attached to piston 54, the segment 44b of chain 44 attached to slide head 38 will be displaced vertically twice the distance through which piston 54 moves in a downward or upward stroke. Thus, lift ~`
beam 32 will move twice as far as piston 54; and with a second chain 46 utilized in the manner shown and connected to lift head 30, bottom lift beam 36 attached to lift head 30 will shift vertically four times the distance that piston 54 does on any particular upward or downward stroke.
.
1~47~
Thus, this particular llfting apparatus does not need an undue amount of `~
space above support boom 1 to support lift head 30 in its position of maximum elevation, and thus does not require an unduly high ceiling for its use. Those skilled in the art will also recognize that other types of drive means other than the multlple chain drive shown may be utilized in combination with a blasing spring to actuate control switch L-7 in response to the generation of slack in the drive means when lift head 30 strikes a contact surfzce. ~or example, there is enough slack or free play between gear teeth that this same control principle could be utilized with a rack and pinion type of li~t arrangement for lift head 30.
With reference to Figures 1 and 4, it may be seen that material pickup means are provided on lift head 30 ln the form of a plurality of suction cups 66a, 66b, 66c and 66d. These cups are attached to mountlng blocks 68a, 68b, 68c and 68d Eor ad~ustable mounting on a pair of slide bars 70 and 72. Bars 70 and 72 are provided with longi-tudinal slots 74, 74a and 76, 76a to accommodate the sliding movement of suction cup blocks 68a - 68d thereon. To this end, fasteners extend-ing through mounting blocks 68a - 68d and through the slots in bars 70 and 72 are releasably secured thereto by wing nuts 78. Slide bars 70 and 72 are also slidably ~ounted on cross beam 42 of lift head 30 by means /r o~ slide brackets 80 and fasteners 82. By loosening fasteners 82, bars 70 and 72 may be slidably ad~usted transversely of lift head 30 on beam 42 to move suction cups 66a - 66d in and out transversely of lift head 30.
Thus, the combination of slldably adjustable mounting blocks 68a - 68b and slide bars 70 and 72 permits suction cups 66a - 66d to be adjusted longitudinally and transversely of llft head 30 to permit picking up varying numbers of pieces of different sizes. Although four suction cups have been shown in the drawings, any number of suction cups could obviously be mounted on slide bar 70 and 72. Also~ I contemplate that different types of pickup means, such as magnetic pickup devices, could be 6atisfactorily used ~n place of the suctlon cups.
As may be noted with respect to both Figures 1 and 4, suction cups are connected through flexible lines 84a, 84b, 84c and 84d with a four-way valve 86 connected in a main vacuum line 88. Vacuum line 88 is connected to a vacuum source, such as the vacuum pump shown at 90 in Figure 4. Four-way valve 86 is controlled by a pair of oppositely acting solenolds S-5 and S-6 which ope~ate to open and close this valve to supply and cut off the vacuum to suction cups 66a - 66d.
In Figure 1 I have shown a conveyor 92 onto which pieces of material, such as sheets of plywood or panels of any kind are received from a processing machine, and which serves as a supply station at which lift head 30 picks up pieces of matexlal and conveys them to a stacking station or other location for further processing. ~ photoelectric cell 94 i9 mounted on one end of sllde bar 72 of lift head 30 in the manner shown ln Figures 1 and 3 to accomplish a height control function with respect to the elevation oP lift head 30, as may best be understood by reference to Figure 3. In i~igure 3, I have illustrated the material handling machine in the process of performing a stacking operation where- -in lift head 30 is picking up pieces of plywood from conveyor 92 and depositing them at a stacking station where the wood panels 96 are stacked to a desired height on a pallet 98. The wood panels may ;~
obviously be stacked in any number of piles or stacks 99 and 100 com-prising a stacking station. In such a material stacklng operation, the lift heads of stacking machines have been traditionally controlled and operated to raise to a predetermined height after picking up a piece of material at a supply station before moving transversely to a stacking station, regardless of the height of the stack of material which must be cleared by the lift head. This necessarily involves a great deal of wasted motion of the lift head and lost time when the stack on which a piece of material is to be placed is lower than the predetermined height : . : :
'7~8 to which the lif~ head is always raised. This inefficient type of material handling in a stacking operation is eliminated by the use of photoelectric cell 94 in combination with a light source 102 comprised of a plurality of beam projecting lights 102a. Light source 102 is adjustably mounted on a standard 104 on the opposite side of stacks 99 and 100 from conveyor 92. Beam lights 102a are positioned to send light signals along horizontal paths which intersect the vertical direction of extent of material stacks 99 and 100 accumulating at the stacking station.
Photoelectric cell 94 functions as a signal sensing device and is mounted -on slide beam 72 of lift head 30 so as to be directed towards light source ;
102 to receive light signals emitted by beam lights 102a. Photoelectric cell 94 operates to close the contacts across a switch designated L-8.
Cont~ol sWitch L-8 is connected in the control circuit shown in ~igure 6 in such a way as to stop the upward movement of liit head 30 and to initiate the lateral movement of carriage 8 from a position over conveyor 92 towards the right, as viewed in Figure 3, to a position over one of the stacks 99 or 100 when its contacts are closed. The control circuit shown in Figure 6 includes a logic circuit comprised of a number of steps corresponding to operating functions of the machine and is explained completely hereinafter with respect to a complete operating cycle of the machine. It is suficient to note at this point that the logic circuits shown in Figure 6 are set up so that as each step is activated by a control switch, the preceding step is deactivated and the next succeeding step is energiæed for actuation. It will be seen that control switch L-8 is connected in series with solenoid valve S-2 in the circuit of step 3. Thus, when the contacts of switch L-8 are closed in response to the sensing of a light signal from one of the beam lights 102a by photoelectric cell 94, solenoid S-3 which controls the upward movement of power piston 54 as shown in Figure 4, is de energized and closed to terminate the upward movement of lift head 30 and solenoid valve S-2 is . . .
energized and opened. As may be noted by reference to Figures 2 and 3, solenoid valve S-2 permits the flow of pressurized ~luid to the rigbt end of pneumatic cyllnder 16 so as to move piston 18 to the left, and thereby pull cable 22 in such a direction as to move carriage 8 to the right, for a stacking right operation.
It will be apparent that with one of the stacks 99 or 100 at a relatively high level as indicated by the phantom lines in Figure 3, the stack of material will block the transmission of a light signal to photoelectric cell 94 when it is at the level with lift head 30 shown in phantom lines just starting to move upwardly with a piece of material from conveyor 92. Thus9 photoelectric cell 94 will not receive a light signal from one of the beam lights 102a until it reaches a level above the helght oP stacks 99 and 100. When llEt head 30 and photoelectric cell 94 reach such a helght, control switch L-8 will be actuated in response to the receptlon of a light signal by photoelectric cell 94, and will function to close solenoid valve S-3 and to open ~ -solenoid valve S-2 to stop the raising of lift head 30, and to initiate -the lateral movement of carriage 8 by pneumatic cylinder 16 in a direction towards the right to convey the piece of wood panel 96 picked up from conveyor 92 to a posltlon over one of the stacks 99 or 100.
I~ the stacks 99 and 100 are at a level below lift head 30 when it picks up a plece of material from the top of conveyor 92, then photoelectrlc cell 94 will immediately receive a light signal and actuate switch L~8 so that lift head 30 will rise only a minimum clearance distance above the top of conveyor 92 and then start moving laterally towards stacks 99 and 100 immediately.
6 e ns~
In order to ~ns~e that ll~t head 30 wlll always rise a minimum clearance distance above the top of conveyor 92, or other supply source, I utillze a limit switch L-3 in series with switch L-8 in the circuit of step 3 shown in Figure 6. Limit switch L-3 is mounted , . , , ~, . .
on an upright bar 106 clearly shown in Figure 1, as well as in Figure 3 at a predetermined elevation to permit the lifting of head 30 to a minimum clear-ance height above the top of conveyor 92. Limit 6witch L-3 is actuated by trip bar 108 carried on lift beam 34 when beam 34, and lift head 30 carried thereby reach the predetermined, minimum c1earance height. Thus, it will be seen that both limit switch L-3 and control switch L-8 under the control of photoelectric cell 94 must be actuated before the lift head elevating function stops, and carriage 8 is shifed laterally to the right.
It should be noted that other types of signal sensing devices, such as an ultrasonic control device may be utilized in place of photoelectric cell 94 to sense the height of materlal stacks 99 an~ 100 and carry out the afore-said li~t height control function.
In Figures 1 and 3 there i8 shown an elongated bar 109 suspended under elevated suppQrt boom 1 whlch ls utilized to support a plurality of limit swltches L-l, L-ll, L-10 and L-2 at the positions shown thereon. These limit switches are utilized in pairs; i.e., L-l, L-ll and L-10, L-2 to stop the lateral movement of carriage 8 at precise, predetermined positions to ~ ~-permit the alternate stacking or picking ~p of wood panels at or from multiple stacks or supply sources. For exa~ple, limit switches L-10 and L~2 are utilized to alternately stop the lateral movement of carriage 8 on a stacking right operation above stacks 99 and 100. Each of these limit switches have actuatlng arms positioned to be tripped by movement of carriage 8 into contact therewith, the actuating arms for two of the switches L-l and L-ll being clearlyshown in Figure 1. The actuating arms for limit switches L-10 and L-2 are mounted and positioned fox tripping by carriage 8 in the same manner as are the trip arms shown ln Figure 1 on limit switches L-l and L-ll. As is indicated in the control diagram of Figure 6, limit switches L-2 and L-10 are connected in parallel with each other, both in series with solenoid valves S-4 in step 4 of the logic and control circuit. The logic circuits are arranged so that 30 only one of the switches L-2 or L-10 is in the control circuit to solenoid S-4 at one time. When one of , .. : . .. :: .,., :, . . . . , . , ;.. , , ~
these limit switches is actuated by carxiage 8, it stops the carriage and simul~aneously actuates a circuit switching the other limit switch L-10 into the control circuit for the nex~ stacking operation. Thus, as carriage 8 first moves to the right as viewed in Figure 3 after pick-ing up a piece of wood paneling 96 from conveyor 92, only switch L-2 is in the control circuit and carriage 8 moves all of the way to the right until it actuates switch L-2. Switch L-2 simultaneously opens the circuit.through solenoid valve S-2 and closes the circuit through sole-noid valve S-4. This has the effect of stopping the movement of carriage 8 towards the right, by shutting off the flow of pressurized fluid to the right end o~ power cylinder 16, and o pennitting pressurized fluid ~ - :
to flow into the upper end of llft head cylinder 52 through solenoid valve S-4 to lnitiate the downward movement of lift head 30 over stack 100. The next tlme that carr:Lage 8 moves to the right after picking up another piece of plywood or wood panellng 96 ~rom conveyor 92, it is stopped by limit switch L-10 over stack 99, switch L~l0 now being in the circuit, and switch L-2 being out of the control circuit. Switch L-10 performs the same functlons as described above with respect to switch L~2 and opening solenoid valve S-2 and closing solenoid valve S~4 to stop the movement of carriage 8, and to initiate the downward movement .
of lift head 30 to deposlt the piece of plywood on top of stack 99.
Obviously, any number o~ stacks may be utll~zed in combination wlth the corresponding requlred number of limit switches to alternately stack pieces of material in different stacking locations adjacent to each other.
It will also be appreciated by those skilled in the art, that switches L-l and L-11 can be used in the same manner as described with respect to switches L-10 and L-2 to alternately actuate solenoid valve S-l to stop the movement of carrlage 8 in a directlon towards the left as viewed in ~igure 3 to per.~it picking up or depositing pieces of , , ~ , , L7~
plywood or other sheet material ~rom or on opposite sides of conveyor 92.
Also, stacks or material handling stations 99 and 100 could serve as alternate sources of supply of pleces of material being fed onto a con-veyor, such as conveyor 92 to supply material to a processlng machine.
With such an operation, limit switches L-2 and L-10 would function in the same manner as described above to permit lift head 30 to alternately pick up pieces of material from stacks 99 and 100.
In ~igures 7 and 8 I have illustrated the manner in which additional controls may be utili~ed in conjunction with my material handling machine to actuate the downward stroke of lift head 30 to pick up a predetermined length of material accumulated on a receiving bed in the form of one article, or a plural:lty of articles. Reference numeral 110 designates a processing machine from whlch articles, such as sheets oE plywood, are deposited on a recelving bed in the form of a conveyor 92a. Such a conveyor would be located with respect to pedestal 2 and the material handllng machine in essentially the same manner as is conveyor 92 shown in Figure 1. Conveyor 92a is illustrated as a belt conveyor comprised of a pair of belts 92b and 92c. Positioned at one end oP conveyor 92a at a predetermined location thereon is a stop means in the form of a stop bar 112 pivotally mounted on an upright support arm 114 by a pivot bracket plate 116. Pivot bracket 116 pivots about point 116a at its point of connection to the upper end of support arm 114. An additional control switch in the form of a limit switch ~-6 is mounted on support arm 114 with its actuating arm 120 positioned to be tripped by the rearward displacement of stop bar 112 about pivot point 116a. A spring 118 acting between support arm 114 and bracket plate 116 normally blases plate 116 and stop bar 112 forwardly so that plate 116 will be out of engagement with actuating arm 120 of limit switch L-6.
In order that stop bar 112 may be adjustably positioned wlth respect to receiving bed 92a for the accumulation o~ a predetermined length of . . ~ .
7~
material, support arm 114 is slidably mounted on a guide rail 122 by ~;
a slide bracket 124, which are shown in Figure 3 as well as in Figure 7 and 8. A control device which may take varlous forms, and whlch is shown for illustrative purposes as a photoelectric cell controller comprised of a light source 126a and a light sens-Ltive, receiving cell 126b is positioned at a predetermined location adjacent to receiving bed 92a. The photoelectric cell controller 126a ~- 126b is located wi~h ... .
respect to bed 92a so that it will be a predetermlned distance forwardly of stop bar 112 in the direction from which material i5 received from ~ ~
processing machine 110 such that the distance between stop bar 112 and ~-the photoelectric controller will be substantially equal to a predetermined total length of material to be accumulated on conveyor 92a to be picked up at one time by lit head 30. The light source 126a for the photo-elec~ric cell i8 positioned under conveyor 92a between conveyor belts 92b and 92c so that lf a sheet of material or other article stops over lt, the transmission o~ the light beam to receiving cell 126b will be blocked.
This will have the effect of closing contacts within receiving cell 126b, which is said to have its contacts closed when the light source to it is interrupted. Photoelectric cell 126b is connected in the control circuit shown in Figure 6 in step 1 of the logic circuit, in series with solenoid control valve S-4 which controls the downward stroke of cylinder piston 5~ and of lift head 30. ~s is illustrated in ~igure 6, a time delay relay 128 is connected in the control circuit in con~unction with the contacts of photoelectric cell 126b so as to be energized when the contacts of photoelectric cell 126b are closed. Time delay relay 128 is set to permit short lengths of material to move past the location of the photoelectric controller, over light source 126a without closing its contacts and completing the circuit through solenoid control valve S-4.
Thus~ a plurality of short pieces of sheet material can pass onto con-veyor 92a without actuating the down stroke of lift head 30. When a .;.
.. . . , , . . .- :, ,:
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single piece of p~edetermined length, or a plu~ality of pieces o~
material equal to the total distance along receivlng bed 92a between stop bar 112 and controller 126a ~ 126b have accumulated on the receiving bed, the transmission of light from source 126a to cell 126b will be permanently blocked. Thus, the time delay period for which time delay relay 128 is set will be exceeded and it will close its contacts to complete a circult through solenoid valve S-4. As may be noted with respect to Figure 4, solenoid controller S~4 directs the flow of pres-surized fluid to the upper end of power cylinder 52 to move piston 54 downwardly and to lower lift ~ead 30. Lift head 30 will be lowered by the drive chain arrangement described above until it contacts the material accumulated on conveyor 92a, and will pick up this material and carry it to a stacking sta~Lon or other processlng station as desired. The longi-tudinal ad~ustment of support arm 114 on guide rail 122 permits stop bar 112 to be longltudinally adJusted on the rece-lving bed towards and away from controller 126a - 126b to permit adjusting the distance there-between for the particular length o~ material desired to be accumulated from processing machine 110, or from any other source.
Limit switch L-6 shown in Figures 1, 7 and 8 is connected in series with the photoelectric cell controller 126a - 126b in the manner shown in the control circuit diagram oF Figure 6. A manual switch designated SW-l i9 connected ln parallel With the photoelectric cell controller as shown in Figure 6, and in series with limit switch L~6.
By closing switch SW-1, the photoelectric cell controller can be by-passed and the machine will operate without the multiple pickup control function. It will be appreciated that with limit switch L-6 connected in the control circuit in such a manner, it must be actuated by the rearward displacement of stop bar 112 when a piece of material contacts bar 112 before the circuit to lift head control solenoid S-4 can be closed. When switch SW-l is closed, the photoelectric cell controller ''` ~ , , 126a - 126b will be bypassed, and th~ tripping of limit switch L-6 when a piece of material is received on conveyor 92a will actuate solenoid valve S-4 and cause lift head 30 to move downwardly to pick up the piece of material. ;
~ complete operating cycle o~ the material handling machine involving the several functions and control operations of the machine set forth above will now be described. For illustrative purposes, a so-called stack right cycle will be described, wherein the machine is picking up material from the con~eyor 92 shown in ~igure 3 and moving to the right and stacking the pieces of material at the stacking station comprised of stacks 99 and 100. As is indicated in Figure 6, there are six basic steps in the cycle, each step containing a logic section and an amplifler section. The loglc section :Ls turned on by a llmit switch and the amplifier sectlon ls turned on by the logic section. The cycle shown starts wlth step 1. When the start switch for the machine (not shown) i9 turned on, step 1 is activated. The cycle starts with carriage 8 positioned at an elevated level over conveyor 92 at the left end o~ boom 1 as ~iewed in Tigure 3. Solenoid 4 will not be actuated to move piston 54 downwardly, and to lower lift head 30 until limit s~itch L-6 is actuated to indicate that a piece of material has been received on conveyor 92 and ls in position to be picked up. If manual switch SW 1 ls open, and the multiple piclcup function controlled by the photoelectric controller 126a - 126b is operational, ~hen this controller must also be actuated, and the contacts o time delay relay 128 closed in response to the accumulation of a predetermined length of material on the conveyor 92 before solenoid val~e S-4 is energlzed. When this happens, piston 54 o~ the power cylinder 52 is mo~ed do~nwardly, and the drive arrangement utilizing drive chains and the liPt beams 34 and 36 lo~ers lift head 30 to pick up a piece o~ material from conveyor 92. When the suction cups 66a - 66b of lift head 30 contact the piece o~ materlal, li~it switch ~-7 is actuated in the manner described above to de-energize solenoid valve S-4 and terminate the downward ~ove~ent of the lit head 30 The closing of switch L-7 also activates ox turns on step 2 and completes a circuit through solenoid valves S-3 and S-5. Solenoid valve S-5 shifts four-way control valve 86, shown most clearly in Figure 9, to its open position to connect the vacuum pump 90 with each of the suction cups 66a - 66d. In this manner, the piece of wood paneling or other sheet material is picked up ~y lift head 30, and the simultaneous actua-tion of solenoid valve S-3 shifts piston 54 upwardly to raise lift head 30. Lift head 30 will move upwardly until trip shoe 108 actuates limit swltc'n L-3 indicating that the lift head has reached the minimum cleaxance height above the conveyor 92; and, lE photoelectric cell 94 senses that the lift head 30 is above the he:Lght of the stacking piles 99 and 100, limit switch L-8 will be closed and the circuit through step 3 and solenoid control valve S-2 will be completed. Step 2 will simultaneously be deacti~ated. The actuation of solenoid valve S-2 ~ill cause carriage 8 to be shifted to the rlght by power cylinder 16, and when one of the li~it switches L-10 or L-2 ls actuated, step 3 will be tuxned off and the circuit thxough step 4 will be completed. Carriage 8 will thus be stopped at a positlon over one of the stacks 99 or 100 and the actuatlon of solenoid valve S-4 in step 4 will cause piston 54 and lift head 30 to move downwardly to deposit the piece of ~aterial on top ol one of the stacks. ~hen the piece of wood paneling 96 contacts the stack, limit switch L-7 will again be actuated to stop the downward movement of lift head 30. This will tuXn off step 4 and complete the cixcuit through step 5 to actuate solenoid valves S-6 and S-3. Solenoid valve S-6 shifts four-way contxol valve 86 to its closed position to shut o~f the vacuum to the suction cups 66a - 66b and solenoid valve S~3 supplies pressurized fluid to the bottom of lift cylinder 52 to ralse , . -.
7~ ~
piston 54 and the lift head 30. ~t the same time, a time deLay relay designated TD-l shown ln Figure 6 ls energized so that if the lift head is already above t~e conveyor 92 and limit s~itch L-3 is actuated lift head 30 will raise another slight distance upwardly before going into step 6 and moving laterally to the left. The closing of limlt switch L-3 and the energizing of time delay relay TD-l completes the -circuit through step 6, and energizes solenoid controller S-1. As may ~e noted with reference to Figure 2, solenoid controller S-l directs the flow of pressurized 1uid into power cylinder 16 at one end thereof so as to shift carrlage 8 to the left as viewed in Figures 2 and 3.
Carrlage 8 will move to the left until it contacts one of the limit switches L-1 or L-ll which will operate to turn off step 6 ancl to energiæe or turn off step 1. ~t thls tlme, a complete cycle will have been completed and carriage 8 will be ln posit-lon above conveyor 92 ready to pick up another piece of material, if there are one or more pieces of material on conYeyor 92 serving to actuate limlt swltch L-6 and/or controller 126a - 126b to ln:ltiate another cycle.
Limit switch L-5 shown at the top of lift beam 30 in Figure 1 is vertically positioned on bar 106 to be actuated by trip shoe 108 to shut off the machine when a pile of material such as that shown a~ stacks 99 and 100 has reached a predetermined, maximum height.
~n additional limlt switch could be utili~ed with lts actuating arm under a stack of material being picked up, so that when the last piece of material is removed from the stack, this limit switch will operate to shut off the ~achine after that piece is conveyed to its processing station.
I anticipate that variaus changes can be made in the structure and operating mechanism and controls of the material handling ~-machine described herein without departing ~rom the spirit and scope of ~y invention as defined by the followlng claims.
Figure 3 is a side elevation view of the machine o ~igure 1 performing a material stacking function;
Figure 4 is a fragmentary, side elevation view o~ the machine of Figure 1 taken from the opposite side of -the machine from 7~
that shown in Figure 3 and illustrating the mechanism for raising and lowering the lift head;
- Figure 5 is a fragmentary, left end elevation view of the machine shown in Figure l;
Figure 6 is a control diagram illustrating the various : :
con~rol steps of the machine; . ;
~: .
Figure 7 is a top, plan view of a receiving bed with ,, ~.
controls mounted thereon for controlling the total length of accumulated .. ~
~ . .
material which the machine picks up at one time;
Figure 8 is a front, elevation view of the receiving bed and controls shown in Figure 7, and ~ igure 9, located on the same sheet as Figure 1, is a plan v~ew o the base of the machine in Figure 1.
Re~erring now to the drawing, I have shown in Flgure 1 a prePerred embodiment of my material handling machine having an elevated ~ .
support boom 1 in the fonm of an I-beam mounted on an upright pedestal 2.
Guide tracks 4 and 6 extending longitudinally along the top and bottom faces of I-beam 1 serve to shiftably support and guide a carriage 8 ~`
which is laterally shiftable back and forth on boom 1. Carriage 8 may !' be shiftably supported on guide tracks 4 and 6 in various ways for sliding ;~ :
or rolllng support thereon. For il:Lustratlve purposes, as most clearly appears in Figure 5, I have utilized rollers for this purpose. An upper ~ YOller~
A set o~ r~ 9 and 10 attach to a horizontal extension 12 of carriage 8 engage the top and rear, side faces of upper guide track 4; and a : :~
bottom roller 14 engages the front ~ace of lower guide track 6.
It will be appreciated that various types of reversible -:
motor means may be utili~ed to move car~iage 8 back and forth on the ~:
guide tracks 4 and 6 o~ boom 1. I have found that a pneumatic cylinder is particularly suitable for this purpose, such a cylinder and its associated piston being designated by reference numerals 16 and 18 in .:, .. . . . . ... .
Figures 2 and 3. The mounting and drive arrangement of cylinder 16 with respect to carriage 8 may best be understood by re~erence to Figures 1 through 3 and 5. Pneumatic cylinder 16 is mounted on the vertical web la of I-beam l as shown in Figure 5, and a bracket 20 attached to piston ~ -18 is secured to an elongated cable 22 guided around sheaves 24 and 26 rotatably supported on vertical axes mounted within the slotted ends of beam web ~a in the manner shown in Figure 1. The ends of cable 22 are secured to a rearward extension 8a of carriage 8 by means of brackets 27 and 28 attached to the opposite sides thereof. The flow of pressurized air to the opposite ends of pneumatic cylinder 16 to reciprocate piston 18 in opposite directions is controlled by a pair of control devices in the form of solenoid valves S-l and S-2.
A lit head generally indicated by rePerence numeral 30 is mounted on carriage 8 for lateral shifting movement therewith by vertically reciprocal carrier means. I have found it particularly ad-vantageous to utilize a carrier means as shown comprised of a plurality of extensible and retractable lift beams 32, 34 and 36 which slidably support each other, and which are driven by a chain drive arrangement hereinafter described to provide a mechanical lift advantage. The lit apparatus may best be understood by reference to Figures 1 and 4. Upper lift beam 32 is ixed at its bottom end to horizontal plate 8b of carriage 8 and slidably supports beam 34 by means oP a slide head 38 on the upper end of lift beam 34 which embraces lift beam 32. A similar slide head 40 is mounted on the bottom end of lift beam 34 and slidably supports and guides bottom lift beam 36. At its lower end, lift beam 36 is secured to cross beam 42 of lift head 30. For the purpose of raising and lowering lift beams 34 and 36, I utilize bi-directional drive means in the Porm o~ a pair of drive chains 44 and 46. Chain 44 is fixed at one end to a spring biased rod 60 extendlng through base plate 8b of carriage 8. The opposite end of chain 44 is attached to slide head 38, ~ ~4~718 wlth chain 44 being guided around a pair of sprockets 47 and 48 mounted on a bracket 50. Chain 46 is guided around a sprocket 51 attached to -slide head 38 and is affixed at one end to base plate 8b of carriage 8. ~ ;
At its opposite end, chain 46 is attached to lift head 30. As may be noted with respect to the showing of chain 46 in Figure 1, both chains 44 and 46 may be double chains guided around a pair of sprockets. As a source of power for driving chains 44 and 46, I utili7e a reversible, double-acting pneumatic cylinder 52 having a reciprocating piston 54 attached at its upper end to mounting bracket 50 on which sprockets 47 and 48 are mounted. The flow of pressurized air to opposite ends of cylinder 52 to reciprocate piston 54 upwardly and downwardly is controlled by a pair of solenoid valves S-3 and S-4.
For the purpose of precisely controlling the downward stroke of lift head 30 so that it will stop immediately upon contacting a sur~ace of any kind, X utilize a control switch designated L-7 having a trip arm 56 disposed in proximity to one end of chain 44. The end of chain 44 near switch L-7 carries a trip bar 58 for act~ating arm 56 of switch L-7. That same end of chain 44 is attached to a rod 60 which extends through base plate 8b of carriage 8 and is normally biased in a downward direction by a coil spring 62 on its lower end. It will be apparent that the load of lift beam 34 and lift head 30 normally acting downwardly on one end of chain 44 will keep chain 44 in tension, with the result that spring 62 will be compressed in a normally loaded condition by the upward force of segment 44a oi chain 44 acting through rod 60. This will cause trip bar 58 to be held at a normal, elevated position out of contact with arm 56 of switch L-7. There is enough "free play" or slack between drive chains 44, 46 and the lift beams 34 and 36 to which they are attached that when lift head 30 engages a contact surface on its downward stroke to thereby remove the tension . ' '~' ' . . ' ' :
.::- , .
7~
stress normally exerted on chains 44 and 46 by the weight of the lift head and the lift beams, chain 44 will be freely movable through a limited distance by the unloading action of spring 62. Spring 62 bears against the bottom base of carriage base plate 8b, and as it unloads downwardly, it will take up any slight slack generated in chain 44, and thereby urge chain segment 44a downwardly. As chain 44a is shifted downwardly, trip -bar 58 carried thereon will engage and trip actuating arm 56 of control swltch L-7. When this happens, actuating arm 56 of switch L-7 will be shifted downwardly to the position shown in Figure 4 w~erein it opens the contacts leading to solenoid valve S-4 and thereby shuts off the supply of pressurized air to the upper end of cylinder 52 to stop the downward stroke oE piston 54. Thls will oE course immediately terminate the downward movement of chalns 44 and l~6, and thus immediately stop the downward stroke of llft head 30 upon contact with a surface of any klnd.
When switch L-7 is actuated in the aforesaid manner, it simultaneously closes the contacts completing a circuit to solenoid valve S-3 to ready lift cylinder 52 for the upward stroke of piston 54 and the elevation o~ lift head 30.
It will be appxeciated from the foregoing description of the lift apparatus, that the use of at least one drive chain 44 or 46 in combination with power cylinder 52 provides a mechanical advantage with respect to the vertical movement imparted to lift head 30 by a particular displacement of piston 54 of cylinder 52. With chain 44 guided around sprockets 47, 48 attached to piston 54, the segment 44b of chain 44 attached to slide head 38 will be displaced vertically twice the distance through which piston 54 moves in a downward or upward stroke. Thus, lift ~`
beam 32 will move twice as far as piston 54; and with a second chain 46 utilized in the manner shown and connected to lift head 30, bottom lift beam 36 attached to lift head 30 will shift vertically four times the distance that piston 54 does on any particular upward or downward stroke.
.
1~47~
Thus, this particular llfting apparatus does not need an undue amount of `~
space above support boom 1 to support lift head 30 in its position of maximum elevation, and thus does not require an unduly high ceiling for its use. Those skilled in the art will also recognize that other types of drive means other than the multlple chain drive shown may be utilized in combination with a blasing spring to actuate control switch L-7 in response to the generation of slack in the drive means when lift head 30 strikes a contact surfzce. ~or example, there is enough slack or free play between gear teeth that this same control principle could be utilized with a rack and pinion type of li~t arrangement for lift head 30.
With reference to Figures 1 and 4, it may be seen that material pickup means are provided on lift head 30 ln the form of a plurality of suction cups 66a, 66b, 66c and 66d. These cups are attached to mountlng blocks 68a, 68b, 68c and 68d Eor ad~ustable mounting on a pair of slide bars 70 and 72. Bars 70 and 72 are provided with longi-tudinal slots 74, 74a and 76, 76a to accommodate the sliding movement of suction cup blocks 68a - 68d thereon. To this end, fasteners extend-ing through mounting blocks 68a - 68d and through the slots in bars 70 and 72 are releasably secured thereto by wing nuts 78. Slide bars 70 and 72 are also slidably ~ounted on cross beam 42 of lift head 30 by means /r o~ slide brackets 80 and fasteners 82. By loosening fasteners 82, bars 70 and 72 may be slidably ad~usted transversely of lift head 30 on beam 42 to move suction cups 66a - 66d in and out transversely of lift head 30.
Thus, the combination of slldably adjustable mounting blocks 68a - 68b and slide bars 70 and 72 permits suction cups 66a - 66d to be adjusted longitudinally and transversely of llft head 30 to permit picking up varying numbers of pieces of different sizes. Although four suction cups have been shown in the drawings, any number of suction cups could obviously be mounted on slide bar 70 and 72. Also~ I contemplate that different types of pickup means, such as magnetic pickup devices, could be 6atisfactorily used ~n place of the suctlon cups.
As may be noted with respect to both Figures 1 and 4, suction cups are connected through flexible lines 84a, 84b, 84c and 84d with a four-way valve 86 connected in a main vacuum line 88. Vacuum line 88 is connected to a vacuum source, such as the vacuum pump shown at 90 in Figure 4. Four-way valve 86 is controlled by a pair of oppositely acting solenolds S-5 and S-6 which ope~ate to open and close this valve to supply and cut off the vacuum to suction cups 66a - 66d.
In Figure 1 I have shown a conveyor 92 onto which pieces of material, such as sheets of plywood or panels of any kind are received from a processing machine, and which serves as a supply station at which lift head 30 picks up pieces of matexlal and conveys them to a stacking station or other location for further processing. ~ photoelectric cell 94 i9 mounted on one end of sllde bar 72 of lift head 30 in the manner shown ln Figures 1 and 3 to accomplish a height control function with respect to the elevation oP lift head 30, as may best be understood by reference to Figure 3. In i~igure 3, I have illustrated the material handling machine in the process of performing a stacking operation where- -in lift head 30 is picking up pieces of plywood from conveyor 92 and depositing them at a stacking station where the wood panels 96 are stacked to a desired height on a pallet 98. The wood panels may ;~
obviously be stacked in any number of piles or stacks 99 and 100 com-prising a stacking station. In such a material stacklng operation, the lift heads of stacking machines have been traditionally controlled and operated to raise to a predetermined height after picking up a piece of material at a supply station before moving transversely to a stacking station, regardless of the height of the stack of material which must be cleared by the lift head. This necessarily involves a great deal of wasted motion of the lift head and lost time when the stack on which a piece of material is to be placed is lower than the predetermined height : . : :
'7~8 to which the lif~ head is always raised. This inefficient type of material handling in a stacking operation is eliminated by the use of photoelectric cell 94 in combination with a light source 102 comprised of a plurality of beam projecting lights 102a. Light source 102 is adjustably mounted on a standard 104 on the opposite side of stacks 99 and 100 from conveyor 92. Beam lights 102a are positioned to send light signals along horizontal paths which intersect the vertical direction of extent of material stacks 99 and 100 accumulating at the stacking station.
Photoelectric cell 94 functions as a signal sensing device and is mounted -on slide beam 72 of lift head 30 so as to be directed towards light source ;
102 to receive light signals emitted by beam lights 102a. Photoelectric cell 94 operates to close the contacts across a switch designated L-8.
Cont~ol sWitch L-8 is connected in the control circuit shown in ~igure 6 in such a way as to stop the upward movement of liit head 30 and to initiate the lateral movement of carriage 8 from a position over conveyor 92 towards the right, as viewed in Figure 3, to a position over one of the stacks 99 or 100 when its contacts are closed. The control circuit shown in Figure 6 includes a logic circuit comprised of a number of steps corresponding to operating functions of the machine and is explained completely hereinafter with respect to a complete operating cycle of the machine. It is suficient to note at this point that the logic circuits shown in Figure 6 are set up so that as each step is activated by a control switch, the preceding step is deactivated and the next succeeding step is energiæed for actuation. It will be seen that control switch L-8 is connected in series with solenoid valve S-2 in the circuit of step 3. Thus, when the contacts of switch L-8 are closed in response to the sensing of a light signal from one of the beam lights 102a by photoelectric cell 94, solenoid S-3 which controls the upward movement of power piston 54 as shown in Figure 4, is de energized and closed to terminate the upward movement of lift head 30 and solenoid valve S-2 is . . .
energized and opened. As may be noted by reference to Figures 2 and 3, solenoid valve S-2 permits the flow of pressurized ~luid to the rigbt end of pneumatic cyllnder 16 so as to move piston 18 to the left, and thereby pull cable 22 in such a direction as to move carriage 8 to the right, for a stacking right operation.
It will be apparent that with one of the stacks 99 or 100 at a relatively high level as indicated by the phantom lines in Figure 3, the stack of material will block the transmission of a light signal to photoelectric cell 94 when it is at the level with lift head 30 shown in phantom lines just starting to move upwardly with a piece of material from conveyor 92. Thus9 photoelectric cell 94 will not receive a light signal from one of the beam lights 102a until it reaches a level above the helght oP stacks 99 and 100. When llEt head 30 and photoelectric cell 94 reach such a helght, control switch L-8 will be actuated in response to the receptlon of a light signal by photoelectric cell 94, and will function to close solenoid valve S-3 and to open ~ -solenoid valve S-2 to stop the raising of lift head 30, and to initiate -the lateral movement of carriage 8 by pneumatic cylinder 16 in a direction towards the right to convey the piece of wood panel 96 picked up from conveyor 92 to a posltlon over one of the stacks 99 or 100.
I~ the stacks 99 and 100 are at a level below lift head 30 when it picks up a plece of material from the top of conveyor 92, then photoelectrlc cell 94 will immediately receive a light signal and actuate switch L~8 so that lift head 30 will rise only a minimum clearance distance above the top of conveyor 92 and then start moving laterally towards stacks 99 and 100 immediately.
6 e ns~
In order to ~ns~e that ll~t head 30 wlll always rise a minimum clearance distance above the top of conveyor 92, or other supply source, I utillze a limit switch L-3 in series with switch L-8 in the circuit of step 3 shown in Figure 6. Limit switch L-3 is mounted , . , , ~, . .
on an upright bar 106 clearly shown in Figure 1, as well as in Figure 3 at a predetermined elevation to permit the lifting of head 30 to a minimum clear-ance height above the top of conveyor 92. Limit 6witch L-3 is actuated by trip bar 108 carried on lift beam 34 when beam 34, and lift head 30 carried thereby reach the predetermined, minimum c1earance height. Thus, it will be seen that both limit switch L-3 and control switch L-8 under the control of photoelectric cell 94 must be actuated before the lift head elevating function stops, and carriage 8 is shifed laterally to the right.
It should be noted that other types of signal sensing devices, such as an ultrasonic control device may be utilized in place of photoelectric cell 94 to sense the height of materlal stacks 99 an~ 100 and carry out the afore-said li~t height control function.
In Figures 1 and 3 there i8 shown an elongated bar 109 suspended under elevated suppQrt boom 1 whlch ls utilized to support a plurality of limit swltches L-l, L-ll, L-10 and L-2 at the positions shown thereon. These limit switches are utilized in pairs; i.e., L-l, L-ll and L-10, L-2 to stop the lateral movement of carriage 8 at precise, predetermined positions to ~ ~-permit the alternate stacking or picking ~p of wood panels at or from multiple stacks or supply sources. For exa~ple, limit switches L-10 and L~2 are utilized to alternately stop the lateral movement of carriage 8 on a stacking right operation above stacks 99 and 100. Each of these limit switches have actuatlng arms positioned to be tripped by movement of carriage 8 into contact therewith, the actuating arms for two of the switches L-l and L-ll being clearlyshown in Figure 1. The actuating arms for limit switches L-10 and L-2 are mounted and positioned fox tripping by carriage 8 in the same manner as are the trip arms shown ln Figure 1 on limit switches L-l and L-ll. As is indicated in the control diagram of Figure 6, limit switches L-2 and L-10 are connected in parallel with each other, both in series with solenoid valves S-4 in step 4 of the logic and control circuit. The logic circuits are arranged so that 30 only one of the switches L-2 or L-10 is in the control circuit to solenoid S-4 at one time. When one of , .. : . .. :: .,., :, . . . . , . , ;.. , , ~
these limit switches is actuated by carxiage 8, it stops the carriage and simul~aneously actuates a circuit switching the other limit switch L-10 into the control circuit for the nex~ stacking operation. Thus, as carriage 8 first moves to the right as viewed in Figure 3 after pick-ing up a piece of wood paneling 96 from conveyor 92, only switch L-2 is in the control circuit and carriage 8 moves all of the way to the right until it actuates switch L-2. Switch L-2 simultaneously opens the circuit.through solenoid valve S-2 and closes the circuit through sole-noid valve S-4. This has the effect of stopping the movement of carriage 8 towards the right, by shutting off the flow of pressurized fluid to the right end o~ power cylinder 16, and o pennitting pressurized fluid ~ - :
to flow into the upper end of llft head cylinder 52 through solenoid valve S-4 to lnitiate the downward movement of lift head 30 over stack 100. The next tlme that carr:Lage 8 moves to the right after picking up another piece of plywood or wood panellng 96 ~rom conveyor 92, it is stopped by limit switch L-10 over stack 99, switch L~l0 now being in the circuit, and switch L-2 being out of the control circuit. Switch L-10 performs the same functlons as described above with respect to switch L~2 and opening solenoid valve S-2 and closing solenoid valve S~4 to stop the movement of carriage 8, and to initiate the downward movement .
of lift head 30 to deposlt the piece of plywood on top of stack 99.
Obviously, any number o~ stacks may be utll~zed in combination wlth the corresponding requlred number of limit switches to alternately stack pieces of material in different stacking locations adjacent to each other.
It will also be appreciated by those skilled in the art, that switches L-l and L-11 can be used in the same manner as described with respect to switches L-10 and L-2 to alternately actuate solenoid valve S-l to stop the movement of carrlage 8 in a directlon towards the left as viewed in ~igure 3 to per.~it picking up or depositing pieces of , , ~ , , L7~
plywood or other sheet material ~rom or on opposite sides of conveyor 92.
Also, stacks or material handling stations 99 and 100 could serve as alternate sources of supply of pleces of material being fed onto a con-veyor, such as conveyor 92 to supply material to a processlng machine.
With such an operation, limit switches L-2 and L-10 would function in the same manner as described above to permit lift head 30 to alternately pick up pieces of material from stacks 99 and 100.
In ~igures 7 and 8 I have illustrated the manner in which additional controls may be utili~ed in conjunction with my material handling machine to actuate the downward stroke of lift head 30 to pick up a predetermined length of material accumulated on a receiving bed in the form of one article, or a plural:lty of articles. Reference numeral 110 designates a processing machine from whlch articles, such as sheets oE plywood, are deposited on a recelving bed in the form of a conveyor 92a. Such a conveyor would be located with respect to pedestal 2 and the material handllng machine in essentially the same manner as is conveyor 92 shown in Figure 1. Conveyor 92a is illustrated as a belt conveyor comprised of a pair of belts 92b and 92c. Positioned at one end oP conveyor 92a at a predetermined location thereon is a stop means in the form of a stop bar 112 pivotally mounted on an upright support arm 114 by a pivot bracket plate 116. Pivot bracket 116 pivots about point 116a at its point of connection to the upper end of support arm 114. An additional control switch in the form of a limit switch ~-6 is mounted on support arm 114 with its actuating arm 120 positioned to be tripped by the rearward displacement of stop bar 112 about pivot point 116a. A spring 118 acting between support arm 114 and bracket plate 116 normally blases plate 116 and stop bar 112 forwardly so that plate 116 will be out of engagement with actuating arm 120 of limit switch L-6.
In order that stop bar 112 may be adjustably positioned wlth respect to receiving bed 92a for the accumulation o~ a predetermined length of . . ~ .
7~
material, support arm 114 is slidably mounted on a guide rail 122 by ~;
a slide bracket 124, which are shown in Figure 3 as well as in Figure 7 and 8. A control device which may take varlous forms, and whlch is shown for illustrative purposes as a photoelectric cell controller comprised of a light source 126a and a light sens-Ltive, receiving cell 126b is positioned at a predetermined location adjacent to receiving bed 92a. The photoelectric cell controller 126a ~- 126b is located wi~h ... .
respect to bed 92a so that it will be a predetermlned distance forwardly of stop bar 112 in the direction from which material i5 received from ~ ~
processing machine 110 such that the distance between stop bar 112 and ~-the photoelectric controller will be substantially equal to a predetermined total length of material to be accumulated on conveyor 92a to be picked up at one time by lit head 30. The light source 126a for the photo-elec~ric cell i8 positioned under conveyor 92a between conveyor belts 92b and 92c so that lf a sheet of material or other article stops over lt, the transmission o~ the light beam to receiving cell 126b will be blocked.
This will have the effect of closing contacts within receiving cell 126b, which is said to have its contacts closed when the light source to it is interrupted. Photoelectric cell 126b is connected in the control circuit shown in Figure 6 in step 1 of the logic circuit, in series with solenoid control valve S-4 which controls the downward stroke of cylinder piston 5~ and of lift head 30. ~s is illustrated in ~igure 6, a time delay relay 128 is connected in the control circuit in con~unction with the contacts of photoelectric cell 126b so as to be energized when the contacts of photoelectric cell 126b are closed. Time delay relay 128 is set to permit short lengths of material to move past the location of the photoelectric controller, over light source 126a without closing its contacts and completing the circuit through solenoid control valve S-4.
Thus~ a plurality of short pieces of sheet material can pass onto con-veyor 92a without actuating the down stroke of lift head 30. When a .;.
.. . . , , . . .- :, ,:
~ lr~3'~ B
single piece of p~edetermined length, or a plu~ality of pieces o~
material equal to the total distance along receivlng bed 92a between stop bar 112 and controller 126a ~ 126b have accumulated on the receiving bed, the transmission of light from source 126a to cell 126b will be permanently blocked. Thus, the time delay period for which time delay relay 128 is set will be exceeded and it will close its contacts to complete a circult through solenoid valve S-4. As may be noted with respect to Figure 4, solenoid controller S~4 directs the flow of pres-surized fluid to the upper end of power cylinder 52 to move piston 54 downwardly and to lower lift ~ead 30. Lift head 30 will be lowered by the drive chain arrangement described above until it contacts the material accumulated on conveyor 92a, and will pick up this material and carry it to a stacking sta~Lon or other processlng station as desired. The longi-tudinal ad~ustment of support arm 114 on guide rail 122 permits stop bar 112 to be longltudinally adJusted on the rece-lving bed towards and away from controller 126a - 126b to permit adjusting the distance there-between for the particular length o~ material desired to be accumulated from processing machine 110, or from any other source.
Limit switch L-6 shown in Figures 1, 7 and 8 is connected in series with the photoelectric cell controller 126a - 126b in the manner shown in the control circuit diagram oF Figure 6. A manual switch designated SW-l i9 connected ln parallel With the photoelectric cell controller as shown in Figure 6, and in series with limit switch L~6.
By closing switch SW-1, the photoelectric cell controller can be by-passed and the machine will operate without the multiple pickup control function. It will be appreciated that with limit switch L-6 connected in the control circuit in such a manner, it must be actuated by the rearward displacement of stop bar 112 when a piece of material contacts bar 112 before the circuit to lift head control solenoid S-4 can be closed. When switch SW-l is closed, the photoelectric cell controller ''` ~ , , 126a - 126b will be bypassed, and th~ tripping of limit switch L-6 when a piece of material is received on conveyor 92a will actuate solenoid valve S-4 and cause lift head 30 to move downwardly to pick up the piece of material. ;
~ complete operating cycle o~ the material handling machine involving the several functions and control operations of the machine set forth above will now be described. For illustrative purposes, a so-called stack right cycle will be described, wherein the machine is picking up material from the con~eyor 92 shown in ~igure 3 and moving to the right and stacking the pieces of material at the stacking station comprised of stacks 99 and 100. As is indicated in Figure 6, there are six basic steps in the cycle, each step containing a logic section and an amplifler section. The loglc section :Ls turned on by a llmit switch and the amplifier sectlon ls turned on by the logic section. The cycle shown starts wlth step 1. When the start switch for the machine (not shown) i9 turned on, step 1 is activated. The cycle starts with carriage 8 positioned at an elevated level over conveyor 92 at the left end o~ boom 1 as ~iewed in Tigure 3. Solenoid 4 will not be actuated to move piston 54 downwardly, and to lower lift head 30 until limit s~itch L-6 is actuated to indicate that a piece of material has been received on conveyor 92 and ls in position to be picked up. If manual switch SW 1 ls open, and the multiple piclcup function controlled by the photoelectric controller 126a - 126b is operational, ~hen this controller must also be actuated, and the contacts o time delay relay 128 closed in response to the accumulation of a predetermined length of material on the conveyor 92 before solenoid val~e S-4 is energlzed. When this happens, piston 54 o~ the power cylinder 52 is mo~ed do~nwardly, and the drive arrangement utilizing drive chains and the liPt beams 34 and 36 lo~ers lift head 30 to pick up a piece o~ material from conveyor 92. When the suction cups 66a - 66b of lift head 30 contact the piece o~ materlal, li~it switch ~-7 is actuated in the manner described above to de-energize solenoid valve S-4 and terminate the downward ~ove~ent of the lit head 30 The closing of switch L-7 also activates ox turns on step 2 and completes a circuit through solenoid valves S-3 and S-5. Solenoid valve S-5 shifts four-way control valve 86, shown most clearly in Figure 9, to its open position to connect the vacuum pump 90 with each of the suction cups 66a - 66d. In this manner, the piece of wood paneling or other sheet material is picked up ~y lift head 30, and the simultaneous actua-tion of solenoid valve S-3 shifts piston 54 upwardly to raise lift head 30. Lift head 30 will move upwardly until trip shoe 108 actuates limit swltc'n L-3 indicating that the lift head has reached the minimum cleaxance height above the conveyor 92; and, lE photoelectric cell 94 senses that the lift head 30 is above the he:Lght of the stacking piles 99 and 100, limit switch L-8 will be closed and the circuit through step 3 and solenoid control valve S-2 will be completed. Step 2 will simultaneously be deacti~ated. The actuation of solenoid valve S-2 ~ill cause carriage 8 to be shifted to the rlght by power cylinder 16, and when one of the li~it switches L-10 or L-2 ls actuated, step 3 will be tuxned off and the circuit thxough step 4 will be completed. Carriage 8 will thus be stopped at a positlon over one of the stacks 99 or 100 and the actuatlon of solenoid valve S-4 in step 4 will cause piston 54 and lift head 30 to move downwardly to deposit the piece of ~aterial on top ol one of the stacks. ~hen the piece of wood paneling 96 contacts the stack, limit switch L-7 will again be actuated to stop the downward movement of lift head 30. This will tuXn off step 4 and complete the cixcuit through step 5 to actuate solenoid valves S-6 and S-3. Solenoid valve S-6 shifts four-way contxol valve 86 to its closed position to shut o~f the vacuum to the suction cups 66a - 66b and solenoid valve S~3 supplies pressurized fluid to the bottom of lift cylinder 52 to ralse , . -.
7~ ~
piston 54 and the lift head 30. ~t the same time, a time deLay relay designated TD-l shown ln Figure 6 ls energized so that if the lift head is already above t~e conveyor 92 and limit s~itch L-3 is actuated lift head 30 will raise another slight distance upwardly before going into step 6 and moving laterally to the left. The closing of limlt switch L-3 and the energizing of time delay relay TD-l completes the -circuit through step 6, and energizes solenoid controller S-1. As may ~e noted with reference to Figure 2, solenoid controller S-l directs the flow of pressurized 1uid into power cylinder 16 at one end thereof so as to shift carrlage 8 to the left as viewed in Figures 2 and 3.
Carrlage 8 will move to the left until it contacts one of the limit switches L-1 or L-ll which will operate to turn off step 6 ancl to energiæe or turn off step 1. ~t thls tlme, a complete cycle will have been completed and carriage 8 will be ln posit-lon above conveyor 92 ready to pick up another piece of material, if there are one or more pieces of material on conYeyor 92 serving to actuate limlt swltch L-6 and/or controller 126a - 126b to ln:ltiate another cycle.
Limit switch L-5 shown at the top of lift beam 30 in Figure 1 is vertically positioned on bar 106 to be actuated by trip shoe 108 to shut off the machine when a pile of material such as that shown a~ stacks 99 and 100 has reached a predetermined, maximum height.
~n additional limlt switch could be utili~ed with lts actuating arm under a stack of material being picked up, so that when the last piece of material is removed from the stack, this limit switch will operate to shut off the ~achine after that piece is conveyed to its processing station.
I anticipate that variaus changes can be made in the structure and operating mechanism and controls of the material handling ~-machine described herein without departing ~rom the spirit and scope of ~y invention as defined by the followlng claims.
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Material handling apparatus comprising: a hori-zontally shiftable carriage on an elevated, horizontal guide track; reversible motor means drivingly associated with said carriage and operable to move said carriage back and forth on said track; a lift head mounted on said carriage for vertical movement upwardly and downwardly, said lift head being horizon-tally shiftable with said carriage; material pickup means on said lift head; means for raising said lift head; a motor means control device operative to initiate movement of said motor means in one direction to shift said carriage in a pre-determined, horizontal direction on said track; a supply station at which pieces of material to be picked up by said material handling machine are deposited; a stacking station at which material picked up from said supply station by said machine is stacked; a signal emitter positioned to send signals at differ-ent vertical levels along horizontal paths which intersect the vertical direction of extent of a stack of material accummulat-ing at said stacking station and on which said material handling machine is placing pieces of material picked up from said supply station; a signal sensing device mounted on said lift head and operative in response to a signal received from said signal emitter to deactivate said lift head raising means and to actuate said motor means control device to initiate movement of said carriage in said predetermined direction, whereby, with said lift head moving upwardly with a piece of material picked up from said supply station, the stack of material accummulating at said stacking station will interfere with the transmission and reception of said signals by said emitter and sensing device at levels below the top of said stack of material and said sensing device will not deactivate said lift head raising means and actuate said motor means control device until said lift head and said sensing device thereon have been elevated to a level above the top of the stack of material accummulating at said stacking station.
2. Material handling apparatus as defined in claim 1, wherein:
said motor means control device is electrically operable;
said signal emitter is a light source; and said sensing device is a photoelectric cell opera-tive to open and close a circuit to said control device.
said motor means control device is electrically operable;
said signal emitter is a light source; and said sensing device is a photoelectric cell opera-tive to open and close a circuit to said control device.
3. Material handling apparatus as defined in claim 2 wherein:
a height control limit switch is interposed in said circuit with said photoelectric cell and said motor means control device and is operative in response to the elevation of said lift head to a predetermined minimum clearance height to close a set of contacts in said circuit to said motor means control device.
a height control limit switch is interposed in said circuit with said photoelectric cell and said motor means control device and is operative in response to the elevation of said lift head to a predetermined minimum clearance height to close a set of contacts in said circuit to said motor means control device.
4. Material handling apparatus as defined in claim 1, wherein:
said apparatus includes means for lowering said head;
said stacking station is comprised of first and second material receiving stations; and first and second limit switches spaced apart along the length of said track in substantially vertical align-ment with said first and second material receiving stations respectively, each of said limit switches being operative in a control circuit in response to contact by said carriage to actuate said lift head lowering means, said limit switches being connected in a logic circuit of said control circuit in such a manner that only one of said switches is in said control circuit at a time, whereby said limit switches alternately actuate said lift head lowering means in response to contact by said carriage to cause the alternate lowering of said lift head at first one and then the other of said material receiving stations to stack pieces of material at said stations.
said apparatus includes means for lowering said head;
said stacking station is comprised of first and second material receiving stations; and first and second limit switches spaced apart along the length of said track in substantially vertical align-ment with said first and second material receiving stations respectively, each of said limit switches being operative in a control circuit in response to contact by said carriage to actuate said lift head lowering means, said limit switches being connected in a logic circuit of said control circuit in such a manner that only one of said switches is in said control circuit at a time, whereby said limit switches alternately actuate said lift head lowering means in response to contact by said carriage to cause the alternate lowering of said lift head at first one and then the other of said material receiving stations to stack pieces of material at said stations.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US359684A US3901392A (en) | 1973-05-11 | 1973-05-11 | Material handling machine |
| CA197,793A CA1009265A (en) | 1973-05-11 | 1974-04-18 | Material handling machine |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1044718A true CA1044718A (en) | 1978-12-19 |
Family
ID=25667546
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA270,337A Expired CA1044718A (en) | 1973-05-11 | 1977-01-24 | Stack-height responsive sheet stacking system |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1044718A (en) |
-
1977
- 1977-01-24 CA CA270,337A patent/CA1044718A/en not_active Expired
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