US3053402A

US3053402A - Case stacking and unstacking machine

Info

Publication number: US3053402A
Application number: US822602A
Authority: US
Inventors: Robert J Russell; Joseph F Cella; Edward A Towles
Original assignee: Cella Machinery Inc
Current assignee: Cella Machinery Inc
Priority date: 1959-06-24
Filing date: 1959-06-24
Publication date: 1962-09-11
Anticipated expiration: 1979-09-11
Also published as: GB909927A

Description

'7 Sheets-Sheet 1 A rroAwe-rs Sept. Il, 1962 R. J. RUSSELL ETAL cAsr: sTAcKING AND uNsTAcxING MACHINE FileaJune 24. 1959 Sept. 1l, 1962 R. J. RUSSELL ETAL CASE sTAcKING AND uNsTAcxING MACHINE Filed June 24, 1959 '7 Sheets-Sheet 2 a L ev n. A 4 mma m m Jn N P I .A 31.! 3 f d M C MM MM/m 0 M W 6 3 4 .y M M F Am 9 G 0./ c. u a l IJ III /f l O a SePt- 11, 1962 R. J. RUSSELL ETAL 3,053,402

CASE STACKING AND UNSTACKING MACHINE Filed June 24, 1959 '7 Sheets-Sheet 3 5 on ipa/92.

Sept'. 11', T962? R. J. RUSSELL ErAL 3,053,402

CASE STACKING ND UNSTACKING MACHINE Filed June 24', 1959 7 Sheets-Sheet 4 'ama/m a Puls/6 Sept. l1, 1962 R. J. RUSSELL ETAL 3,053,402

CASE STACKING AND UNSTACKING MACHINE Filed June 24, 1959 7 Sheets-Sheet 5 7k;` Jl iii 74 i E E INVENTOR:

@056er a. .easafzL fill@ By on/Alea A. ron/fs Sept. 1l,

Filed June 24, 1959 R. J. RUSSELL ETAL 3,053,402

CASE STACKING AND UNSTACKING MACHINE 7 Sheets-Sheet 6 @wd/0M ATTO/wys Sept 11, 1962` R. J. RUSSELL ETAL 1 3,053,402

CASE STACKING AND UNSTCKING MACHINE IN VEN TOR' Patented Sept. 11, 1962 3,053,402 CASE STACKING AND UNSTACKING MACHINE Robert J. Russell, Northl'ield, Mass., Joseph F. Cella,

Brouxville, N.Y., and Edward A. Towles, Northampton, Mass., assignors to Cella Machinery Inc., New York, N.Y., a corporation of New York Filed .lune 24, 1959, Ser. No. 822,602 4 Claims. (Cl. 214-6) This invention relates to machines for stacking and/ or unstacking articles such as boxes, milk cases, or the like. The invention as disclosed herein is adapted to receive successive articles to be stacked from a line of such articles moving along on a conveyor, Istack the articles, and discharge the stack from the machine. In the alternative, a machine embodying the invention as disclosed herein is adapted to receive successive stacks of articles from a line -of such stacks moving on a conveyor and unstack each stack, discharging the unstacked articles from the machine.

A primary object of the invention is the provision of a stacking and/or unstacking machine which is fully automatic in oper-ation, is o small, compact size in relation to the operation it performs and the articles it handles, which may be fabricated at a low cost, and installed with a minimum of disturbance of the article conveyors with which it is to be associated.

Another object of the invention is the provision of a machine which will stack boxes or cases moving one behind the other on a conveyor which runs through the machine by picking successive cases upwardly off the conveyor to place each case so removed beneath a case previously removed until a stack of `determined height has been accumulated, and thereafter place the stack back on the conveyor from which the cases were originally drawn so that the stack may be discharged from the machine.

Another object of the invention is the provision of an unstacking machine adapted to receive successive stacks Iol boxes or cases from la conveyor running through the machine and which will successively remove the lowermost case of the stack land place it on the same conveyor by which the stack entered the machine so that the case may be discharged from the machine, and automatically repeat the operation until all of the cases of successive stacks have been discharged from the machine.

Another object of the invention is the provision of a case stacking machine which includes a reciprocating case elevator operable to raise successive cases olf of a case conveyor and place them on cooperating case supporting means which supports each case spaced above the conveyor a distance exceeding the height of the foillowing case, with `the means for supporting the cases above the conveyor being automatically retracted to place the cases so supported on the folowing case as the same is raised by the elevator, and with such supporting means being extensible to support the last raised case and those resting thereupon to all-ow the elevator to return to a lowered position preparatory to raising the next following case.

Another object of the invention is the provision of a case unstacking machine which includes an elevator for raising `a stack of cases oi of a case conveyor with a case holding `device operable synchronously with the elevator to support the stack of cases above the lowermost case and hold ysuch stack elevated as lthe elevator moves downwardly to place the lowermost case lon the conveyor, and which stack holding device will release the stack when the elevator returns upwardly from the conveyor after a previously unstacked case has been discharged from the machine to allow the elevator to lower the stack the height of the bottom case and thereafter again support the stack as the elevator lowers the bottom case to the conveyor with the cycle repeating until all of the cases of the stack have been deposited by the elevator on the conveyor and discharged from the machine.

Another object of the invention is the lprovi-sion of an 'article handling machine which is selectively operable to stack cases at one time and unstack cases at another time, with whichever operation desired beingsele'cted by the machine attendant. While hereinafter the :invention is described `and claimed in connection with case stacking and un-stacking, it should be understood that the word case is used broadly to describe boxes, crates, and the like.

Other objects, advantages, and meritorious features will more fully appear from the specification, claims, and accompanying drawings wherein: A g

FIG. 1 is a top view of a mach-ine embodying the invention;

FIG. 2 is va cross sectional view taken on' the line 2-2 of FIG. l;

FIG. 3 is a cross sectional view taken on the line 3 3 of FIG. 2;

FIG. 4 is a cross sectional view taken on the line 4-4 of FIG. 3;

FIG. 5 is a schematic view showing the relative positions between cases during the stacking operation;

FIG. 6 is -a schematic view showing the relative positions of cases during an unstacking operation;

FIGS. 7 and 8 are schematic views of the electrical control `system ofthe machine, FIG. 7 relating primarily to that portion of the system which is operative when case stacking is selected, and FIG. 8 relating to that portion of the system which is operative when unstacking is selected.

The machine described herein is particularly well suited for the stacking or unstacking of milk bottle cases and when used as a stacker in a dairy, is positioned over a case conveyor carrying lled cases away from the machine which deposits the milk bottles in the cases. In the event the machine is to be used as an unstacker, it is positioned over the case conveyor somewhere ahead of the station at which the empty bottles are removed from the cases, or in the event of the cases being used for packing paper cartons of milk and where the cases are returned empty to the dairy, the machine would be positioned ahead of the case washing machine. Where the machine is to be used in a dual capacity, i.e., at one time as a stacker and at :another time as an unstacker, the conveyor system with which it is associated will have a single conveyor common to the machine which is capable of operation in opposite directions and during operation in one direction will deliver stacks of cases to the machine for unstacking, and when operated in the other direction will deliver single cases` to the machine for stacking.

The machine disclosed herein stacks and unstacks cases from the bottom. In other words, rather than placing successive cases one on top of the other as would normally be done by hand in building a stack, this machine places successive cases one beneath the other to Ibuild the stack. In unstacking, the machine withdraws successi-ve cases from the bottom of a stack rather than withdrawing the cases from the top of the Stack. The unstacking operation is essentially merely the reverse of the stacking operation with certain variations,

The machine as disclosed herein has been designed for use with what is termed an in-floor conveyor, which type of conveyor is coming into widespread use in the dairy industry. The machine is simply placed in the door through which the in-floor conveyor travels with provision being made to allow the case lifting fingers of the case elevator to drop below the case supporting surf-ace of the conveyor.

A typical installation for handling conventional milk bottle cases of a size approximately 14" long by 111/2" wide, would occupy a space roughly 3'4 square centered over the case conveyor and with the height of the machine being substantially equal the height of the stack of cases to be handled. The machine, generally indicated at 20, is adapted to rest on the floor over which the cases are conveyed by the case conveyor 22. The case conveyor serves to deliver cases to and discharge cases from the machine, and is a conventional double chain conveyor. The cases rest on the chains and as the chains move, the cases are frictionally carried therewith. The machine has a frame comprising, as best shown in FIGS. l and 2, four

upright channel members

24, 26, 28, `and 30, which are secured by

angle plates

32, 34, 36, and 38 to a pair of lloor plates 40 and 42 disposed on opposite sides of the case conveyor 22. The lloor plates may in turn be secured to the floor of the building as by bolts or the like 44. Disposed at opposite sides of the conveyor 22 and carried by this frame is the vertically shiftable case elevating and lowering mechanism indicated generally at 46, as well as the case retaining mechanism which includes the supporting mechanism 48 and the case holding or clamping mechanism 50, the latter being operative only during unstacking.

Tie plates 52 are secured to

uprights

24 and 26 as shown in FIGS. 1 and 2, and a similar tie plate, not shown,

rigidilies uprights

28 and 30. Another tie plate 54 extends across conveyor 22 spaced thereabove so as not to interfere with case travel on the conveyor and is secured between and to the upper ends of

uprights

26 and 30 to tie the upper ends of the framework on opposite sides of the conveyor together.

Assuming the machine is to be used for stacking cases, the cases C enter the machine on the case conveyor 22 in the direction of arrow S in FIG. 1, one behind the other. As the leading case passes between

uprights

26 and 30 and its leading edge is about one-half the way through the machine, it strikes the arm 56 of switch LS-l, which in turn activates lluid pressure cylinder 58 to withhold the advance of those cases following the leading case. Cylinder 58 is pivotally connected at 60 to a bracket 62 secured to upright 30 and at the opposite end has a piston rod pivotally connected at 64 to a case stop 66, in turn pivotally supported by a bracket 68 secured to upright 30. As LS-l is tripped, it causes pressurization of cylinder 58 to pivot the stop 66 from the solid to the phantom outline position in which the stop presses against the case next following the leading case and withholds its movement.

The leading case continues to travel until it comes into abutment with the extended

case locators

74 and 76. The case locators are a pair of abutments or stops, one at each side of the path of case travel, which are extensibly and retractibly carried by bearings 78 and 80 secured to uprights 28 and 32, and are actuated for such movement by fluid pressure cylinders 82 and 84, also mounted in any convenient fashion on uprights 28 and 32. As will `hereafter appear, these locators remain in the extended position during the stacking operation and retract to let a stack pass out of the machine on conveyor 22 at the end of the stacking operation.

When the case actuates switch LS-l, such switch initiates a time delay relay 'fR-1, which relay measures a determined interval of time suicient to allow the case to reach the

locators

74 and 76 and then causes the case elevator 46 to start its rising oper-ation to lift the case off the conveyor to a height above that of the following cases. The case elevator includes four case lifting lingers indicated at 118, 118 120, and 120,1, and hereinafter more fully described. As the case rises, case supports 86, 86a, 88, and 88a above it retract, allowing any cases supported thereon to be placed on the ascending case and to allow the ascending case to pass by the supports. When the ascending case reaches a position above the supports, they are again extended, the elevator reverses its travel, and during descent places the case on the supports and continues back down to its starting position to repeat the operation.

The elevator comprises a pair of identical mechanisms on opposite sides of the conveyor 22 and disposed between the uprights of the frame. Each such mechanism includes a pair of

vertical rods

96 and 98 for one mechanism, and and 102 for the other. Hereafter a description of one such mechanism will sullice for both. The rods are mounted on the upright frame members in

blocks

99 and 101 secured to the frame members and to opposite ends of the rods. &lpported for vertically slidable movement on the rods is an elevator carriage which includes a pair of

vertical members

104 and 106 having

rod bearings

108, 110, 112, and 114 secured thereto and received upon the rods, with a horizontal cross member 116 extending between and secured to the upper ends of

members

104 and 106. Secured to the lower end of the carriage and specilically to the lower ends of

members

104 and 106 are the elevator lingers 118 and 120 which, as will be noted with respect to linger 118 in FIG. 3, extend beneath the path of travel of a case on conveyor 22.

The elevator lingers are raised and lowered by a fluid pressure cylinder 122 which acts upon the elevator carriage. Cylinder 122 is secured at the lower end to the lloor plate 42, and at the upper end has a piston rod 124 connected to the cross piece 116 of the carriage. Upon pressurization of the cylinder at the lower end the lingers are raised, While pressurization at the opposite end causes the lingers to be lowered. The

complemental elevator fingers

118a and 120a on the opposite side of the case conveyor cooperate with lingers 118 and 120 to raise cases off the conveyor or replace elevated cases on the conveyor. The lingers come up simultaneously beneath the bottom of the cases to raise them from the conveyor.

The case supports 48, which hold the previously raised cases elevated as succeeding cases are brought up to be stacked beneath those held by the supports, comprise the aforementioned four lingers 86, 86,1, 88, and 88a, which are mounted for extensible and retractible movement with two of the fingers disposed on each side of the conveyor 22 and yat a height thereabove so that they will clear the top of the highest case which may be stacked or unstacked by the machine. A description of one pair of lingers as shown in FIGS. 3 and 4 will suffice for both pairs. The fingers are carried by

sleeve bearings

126 and 128 slidably mounted on

rods

130 and 132, which are carried at opposite ends by

vertical plates

134 and 136 upstanding from and secured to the iloor plate 42. A cross member 138 extends between and is secured to the lingers behind the sleeve bearings to prevent revolution of the lingers on the rods. The fingers are disposed just beyond the edges of vertical plate 134 and reciprocate from a retracted position shown on both sides of conveyor 22 at 86 and 86 in FIG. 6 and an extended case supporting position shown at 86 and 86 in FIG. 5. A lluid pressure cylinder 139 suitably supported at one end on an angle member 141, secured to vertical plate 136, and having a piston rod 140 connected to cross member 138, is opera tive to extend and retract the pair of lingers 86 and 88, while a similar cylinder is operative to accomplish the same with the other pair of lingers 88 and 88a.

Considering FIGS. 3 and 5, the sequence of operations in stacking cases may be readily comprehended. Assuming a case C-2 is supported by the supporting lingers, of

v which two are shown in FIG, S at 86 and 86a, and another case rests on the case conveyor 22 and is in abutment with the

locators

74 and 76, which are in the extended position shown in phantom outline, as mentioned herebefore the case has actuated LS-l and after a short time delay the elevator starts its upward movement raising the elevator lingers, of which two are shown at 120 and 120,... The lingers pick case C-1 off the conveyor and raise it toward the position occupied by case C-2. lust before the upper edge of case C-l strikes the Icase supports 86 yand 86a, switch LS-3, mounted on the upright frame member 30, is actuated by an adjustable trip 142 mounted on the elevator member 104. Actuation of switch LS-3 causes the case supports 86 and 86a to be retracted to the position shown `in FIG. 6. Because case C-1 is moving rapidly upwardly and the supports are withdrawn from beneath case C-2 when only substantially one-half inch or less exists between the two cases, case `C-2 will `drop only slightly, perhaps one-quarter inch, before it seats upon case `C-1. With case C-2 now stacked on case \C-1, both cases are elevated through the remainder of the stroke of cylinder 122. At the top `of the stroke of cylinder` 122, and assuming a full stack has not been accumulated, switch LS-4 is contacted by an adjustable trip 144 mounted on the elevator carriage and this reversely pressurizes the cylinders 139 to extend the case supports 86, 86a, 88 and 88a. When the case supports yare extended, switch LS-7, mounted on the bracket 141 and having a switch arm in contact with the cross member 138 w-hen the supports are retracted, is actuated to cause the elevator to lower cases C-l and C-2 to the supports, upon which they are placed as the elevator returns to its starting position shown at 120 and 120,l in FIG. 5.

As cases C-1 and @-2 are now carried by the supports, another case may enter the machine for stacking. As the elevator reaches the bottom 4of its movement, it trips switch LS-S mounted on the oor plate 42, which in turn reversely pressurizes case stop cylinder 58 to retract the stop 66 away from the case it is holding, allowing such case to enter the machine and trip switch LS-1 to repeat the abovedescribed cycle.

As the stack of cases increases in height through repetition of the cycles, the machine automatically stops the stacking after a determined number of cases have been stacked, and the stack is thereafter sent out of the machine on conveyor 22. Secured to the machine -frame are a pair of

case stacking guides

150 and 152, each generally L-shaped in cross section and which extend beyond the height to which the cases are to be stacked. Mounted at the upper end of one of the guides is switch LS-6, the actuating arm 154 of which is contacted by the top case of the sta-ck as the elevator is raising the entire stack to place it on the case supports. Upon actuation of LS-6, cylinder 122 is reversely pressurized and instead of continuing to raise the stack, the elevator returns it to conveyor 22 to be carried thereby out of the machine. LS-6 also serves to reversely pressurize cylinders 82 and 84 of the case locators, causing retraction of the locators out of the path of the stack so that the stack may leave the machine. As the stack leaves the machine and clears the

locators

74 and 76, it trips switch LS-S, which causes pressurization of cylinders 82 and 34 to extend the locators and reversely pressurize cylinder 58 to allow the next case to enter the machine so the stacking cycles may continue.

FIGS. 7 and 8 are schematic views of the electrical control system of the machine with FIG. 7 relating primarily to the circuitry of such system operative when case stacking is selected. FIG. 8 shows the circuitry =op erative when unstacking is selected. A selector switch 160, when moved to the position shown in FIG. 7, will energize the circuit of YFIG. 8 for unstacking operation of the machine, and when moved to the right to the phantom outline position shown, will de-energize the circuit of FIG. 8 and energize that portion of the circuit of FIG. 7 below the switch for stacking operation of the machine. As mentioned hereinabove the elevator, case locators, case stop, and case retaining mechanism are operated by uid pressure. Such pressure is derived from a suitable pump driven by an electric motor schematically indicated at 162 lin FIG. 7. Suitable iluid pressure lines extend from the pump driven by electric motor 162 tothe various cylinders herebefore mentioned which actuate the case elevator, etc. Disposed in the pressure lines between the pump and the cylinders are solenoid operated spring return valves. The solenoids for the operation of such valves are shown in FIGS. 7 and 8 as at 164 for the' solenoid that controls the valve which, in turn, controls the extension and retraction ofthe

case locators

74 and 76. Each solenoid operated valve, uponv energization of its' respective solenoid, serves to admit fluid pressure to' the associated cylinder to cause extension of the piston rody of the cylinder, and upon de-energization of the s'olenoidthe valve is spring-returned to a position redirecting luid pressure to thev associated cylinder to cause retraction of the piston rod associated therewith'. The circuits shown in =FIGS. 7 and 8 include the limits switches LS-1, LSV-4, etc., hereinabove mentioned. LS-1, shown' in FIG. 7, is provided with two throw arms, one being indicated at LS-la and the other at LS-lb. LS--lEL is a norm-ally open throw which is closed by a case entering the machine and contacting the arm 56. LS-lb is a normally closed throw which is opened by a case entering the machine and striking the actuating' arm S6. It will be noted that whether the throws or switches are normally open or' normally closed :isv indicated by whether the throw arm' is above or below the circuit line in which the switch is schematically shown as connected.

Circuits

7 and 8 include a plurality of relays, the solenoids for which are enclosed in circles and give CR designations. The respective slave switches' which are controlled by relay solenoids are also given CR designations followed by a number identifying the switch with the particular relay solenoid which controls it. As'there may be a number of enslaved switches controlled' by a single relay solenoid, the various switches controlled b y `anypar'ticular relay solenoid are identified successively Vby alphabetical sub-scripts. The' circuitry of FIG.y 7 also includesa time` delay type of relay indicated at TR-l which, upon energization for a determined time interval, will cause its enslaved switch 'PRK-1.a -to be closed. Upon deenergization of TR-l, switch TR-l will open. Certain of the relay switches, such as CRAGD, `are normally closed, i.e., are closed when the controlling relay solenoid is deenergized, While relay Switches such #as CR-fl,a are normally open and tare closed only when the relay Vsole'noids actuating such switches are energized. Ay further description of the circuit of FIG. 7 is believed unnecessary as the operation of the machine can be traced through the circuit.

The structure of the machine thus far described is sufficient to stack cases entering the indexing station and release successive stacks from the station for discharge therefrom on the case conveyor 22. With certain additions to the structure described, the machine may be made to unstack cases. Reference has heretofore been made to the unstackirig circuit (FIG. 8) which would be operative during unstacking. With the exception of LS-3, the same limit switches are used during unstacking as are used during stacking but the circuitry in which the switches are operated differs as will be evident from a consideration of FIGS. 7 and 8. Certain additional limit switches are provided when the machine is to be used for unstacking. It will be apparent that if the machine is to be a dual purpose machine, i.e., one which will both stack and unstack, the additional switches necessary for the unstacking operation would be permanently a part of the machine and while they would be actuated during certain phases of the stacking operation, would have no effect on the stacking operation.

In FIG. 1 la case stop similar to the case stop 58 heretofore described is secured to the right-hand end of the machine `for the purpose of preventing or allowing entry of stacks of cases moving on conveyor 22 toward the machine. Such case stop is of identical construction to that of the one heretofore described and therefore a further description is believed unnecessary.

One additional structural addition to the stacking machine to adapt it for unstackingis the case clamping mechanism 50 shown in FIGS. 3 and 4. Such mechanism includes a pair of clamping

pads

166 and 168, one disposed at each side of -a stack of cases in the machine and extensible and retractable to grip or release a case disposed between them. Such case gripping clamps are Yoperable synchronously with the operation of the oase supporting finger mechanism 48 during unstacking operation in a manner hereinafter described. Because the clamping pad 166 is carried by mechanism which is a duplicate of that supporting the pad 168, a description of the mechanism for pad 166 will suiice for both.

As shown in FIGS. 3 and 4, pad 166 is carried by a pair of push rods 17 0 and 172, which yare received within rod supporting blocks or the like 174 and 176, which are mounted on a plate 178 which extends across the top of and is secured to the

uprights

134 and 136. A hydraulic cylinder 180 is mounted on plate 178 with the piston rod 182 thereof connected to the push rods by a cross member 184. Upon pressurization of cylinder 180 in one direction, the push rods and consequently the pad 166 will be extended while upon reverse pressurization, the pad and push rods will be retracted. The pad moves between the solid outline position shown in FIGS. 3 and 5 and the phantom outline position bearing against a case as shown in FIG. 5 or the solid outline position shown in FIG. 6. Also included in the machine when adapted 'for unstacking are limit switches LS9 and LS-dt). Switch LS9 is mounted on a cross member 188 which extends between and is secured to the bearing blocks -174 'and 176. The switch has Ian actuating arm 190` which extends above the pad 166 to a point where it may be contacted and shifted by a oase disposed between the

clamps

166 and 168. Whenever a case is disposed between the clamps, switch LS9 will be actuated. LS9 is schematically shown in the circuit of FIG. 8. Switch LS- is disposed at the left-hand end of the machine to sense the discharge of successive cases from the machine during the unstacking operation and in this respect is similar in function to switch LS-8 heretofore mentioned in connecton with the stacking operation. LS-10 includes two throw arms 11S-10a and 11S-10b as shown in FIG. 8, both of which are closed by a case leaving the machine and contacting the switch actuating arm 192.

The unstacking cycle of the machine occurs as follows. Stacks of cases enter the machine successively on the case conveyor `22, the latter being operated in the direction of an arrow U shown in FIG. l. The selector switch in the control system is shifted to the solid outline position shown in FIG. 7 de-energizin-g the circuit of FIG. 7 below the switch and energizing the circuit of FIG. 8. As the locators 46 are in the retracted position, the leading stack entering the machine will contact switch arm 56 to actuate LS-l which, in turn, will energize the case stop solenoid to extend the stop 66 to prevent the next following stack from interfering with the leading stack in the machine. As the leading stack moves farther into the machine, one of the cases will strike the actuating arm 190 of LS9 serving to energize relay CR-10 in turn closing relay switch Clt-10a to energize time delay relay TR-L Upon expiration of a determined time interval, TR-l will close enslaved switch TR-la to energize the case elevation solenoid and cause the case elevator fingers 120 and `128 to lift the stack out of the indexing station. When the elevator reaches the top of its stroke, it closes switch LS-4 which, in turn, `causes the elevator to descend. During descent of the elevator and when case VC-2 has reached substantially the position shown in FIG.

5 during descent of lthe stack, switch LS-11 is closed energizing the clamp solenoid causing fluid pressure to be directed to cylinders 180 of both clamping mechanisms to cause extension of the clamps and gripping of case C-2. With case C-2 clamped and with the elevator continuing to descend, case C-1 will continue to descend and will be placed on conveyor 22 for discharge yfrom Vthe machine.

When the elevator bottoms, it closes switch LS-S, which serves to energize the case support solenoid controlling extension or retraction of the supporting lingers 86 and 86a. These fingers now extend beneath case C-2 to support it and when they are vfully extended, serve to close LS-7, which in turn causes the de-energization of the case clamp solenoid causing retraction of the

pads

166 and 168. As the first case to be unstacked leaves the machine and strikes arm 192 of LS-lt), it closes LS-lt), and 1.840 in turn causing the elevator to re-ascend. The elevator lifts case C-2 upwardly oif the supporting

fingers

86 and 36 and when the elevator reaches the top of its stroke, LS-la and LS-fi,J are closed reversing the movement of the elevator and the cycle repeats.

When the last case of the stack is lowered to the conveyor 22 for discharge from the machine, as no case will then be in contact with switch arm `19t), circuit 8 is set up for the reception of the next stack of cases though the case stop 66a does not retract until the last case of the previously unstacked stack of cases clears out of the machine and strikes arm 192 of switch LS-lti. At this point the aforedescribed cycle will repeat.

From the above description it is now apparent that the machine disclosed herein can be used for either stacking or unstacking of cases simply by the selective positioning of switch 160 in the control system and by selecting the direction of movement of the case conveyor 22. It will be noted that when a stack of cases enters the machine, those cases above the lowermost case `will come into contact with the stacking guides l159 and 152 which, in this event, serve as case stack locators and interrupt the travel of the stack of cases through the machine. The time delay cycle of time delay relay 'IR-2 may be so adjusted that substantially at the same instant that a stack of cases entering the machine `cornes into abutment with guides and 152, the elevator will be caused to ascend to lift the stack olf of the conveyor. It will also be noted that because of the particular way in which the machine is cycled during unstacking, the machine will cause unstacking of stacks of cases of varying heights anywhere from -two or more cases in height. In the event that a single case should enter the machine when the machine is operating to unstack cases, such single case will pass directly through the machine without hindrance.

What we claim is:

1. A case unstacking machine comprising, in combination: an indexing station, a case conveyor running through the station, case stop means at the upstream side of said station relative to the movement of the case conveyor, 'case locating means in the station for interrupting movement of a stack of cases entering the station on the conveyor, a vertically reciprocable case elevator operable between a stack receiving position in the station and a stack elevated position above the conveyor, stack retaining mechanism disposed above the conveyor for receiving and holding a stack of cases raised therefrom by the elevator, said retaining mechanism operable to hold that case superjacent the case supported by the elevator during lowering of the supported case to the conveyor and responsive to the return of the elevator to a position supporting such superjacent case to release such superjaccnt case for lowering to the conveyor and hold the next superjacent case as the stack is lowered on the elevator toward the conveyor, and said case-retaining mechanism comprising case-supporting fingers extensible and retractable adjacent a stack of cases to extend beneath the lowermost case of the stack to support the stack, and further comprising case-gripping pads on opposite sides of a stack of cases and operable synchronously with the supporting fingers to grip a case prior to the extension of the supporting fingers therebeneath and release the case upon extension of the lingers therebeneath.

2. A case unstacking machine comprising, in combination: a case indexing station, a case conveyor running through the station, case stack retaining mechanism disposed above the station and including case supporting means and case clamping means, said case supporting means including extensible and retractable case supporting elements at opposite Sides of a stack of cases spaced above the station and shiftable from a retracted position to an extended position beneath the stack to support the stack thereon when in the extended position, said clamping means disposed above the case supporting means to grip the sides of a case disposed immediately above the case supporting elements, said clamping means responsive to descent of the elevator to clamp that case superjacent the case on the elevator and responsive to an extension of said case supporting elements beneath the clamped case to release the clamping of the case, and said case supporting means responsive to the presence of the elevator in a stack supporting position beneath a stack Supported thereby to shift from the extended to the retracted position.

3. A machine for stacking or unstacking cases or the like comprising, in combination: a case conveyor; a case elevator for raising cases from or lowering cases to the conveyor; case-retaining mechanism for holding a case spaced above the conveyor and including rst case-supporting means shiftable to and from case-supporting positions beneath a case spaced above the conveyor, and `second case-supporting means operable to grip or release the sides of a case spaced above the conveyor; a selective control system for stacking or unstacking operation of the machine and operatively connected to the elevator and retaining mechanism and responsive, when case stacking is selected, to case-elevating movement of said elevator with a case thereon to cause release of a case held by the retaining mechanism as the case on the elevator approaches the held case, to allow stacking of the cases; and said control system responsive, when unstacking is selected, to the presence of the elevator at a stack-lowering position, to cause said rst case-supporting means of the case-retaining mechanism to release the lowest case of the stack and cause the second case-supporting means to grip the sides of the superjacent case as the lower case descends on the elevator toward the conveyor, and responsive to a determined descend of the elevator separating the case thereon from the case gripped by the retaining mechanism to cause said first supporting means to shift beneath the gripped case to support it.

4. The invention as defined in claim 3 characterized in that when case stacking is selected, said control system is operative to cause release of a case held by said retaining mechanism independently of contact of the case on the elevator with such retaining mechanism as the case on the elevator approaches the case held by said retaining mechanism.

References Cited in the le of this patent UNITED STATES PATENTS 2,028,410 Rapisarda Jan. 21, 1936 2,550,587 Neja Apr. 24, 1951 2,687,813 Verrinder et al Aug. 31, 1954 2,857,040 Campbell Oct. 21, 1958 2,885,097 Lyon May 5, 1959 2,931,524 Hallenius Apr. 5, 1960 2,937,482 Layott et al May 24, 1960 2,997,187 Burt Aug. 22, 1961 FOREIGN PATENTS 530,027 Belgium July 15, 1954 1,154,764 France Nov. l2, 1957