US2113926A

US2113926A - Box stacking machine

Info

Publication number: US2113926A
Application number: US735575A
Authority: US
Inventors: Harold C Pierce
Original assignee: FMC Corp
Current assignee: FMC Corp
Priority date: 1934-07-17
Filing date: 1934-07-17
Publication date: 1938-04-12
Anticipated expiration: 1955-04-12

Description

April 12, 1938. c. PIERCE 2,113,926

Box STACKING MACHINE Filed July 1'7-I 1934 3 Sheets-Sheet l April l2, 1938. H. c. PIERCE Box sTAcKING MACHINE Filed July 17, 1934 3 Sheets-Sheet-2 INVENTOF? HAQOLD C P/EQCE B p -Y l Wm ATTORNEY April l2, 1938. H. C. PIERCE y V BOX STACKNG MACHINE Filed July 17, 19554 5 Sheets-Sheet 3 Y R mm m NP. R E@ o Wp. .H .A

I Patented Apr. 12, 1938 PATENT OFFICE Box sTAcxiNG MACHINE Harold C. Pierce, Anaheim, Calif., assignor, by

direct and mesne assignments to Food Machinery Corporation, a corporation of Delaware Application July 17, 1934, Serial No. 735,575

ze claims.

'Ihis invention has to do in a general way with 'machines for stacking articles, such as crates, boxes and the like, andfis more particularly related to improvements in that type of stacking machine which is shown and described in.my co-pending application Serial No. 655,607, led on February '7, 1933, now Patent-No. 2,005,906.

Stacking machines of the general character contemplated by this invention embody conveyor means' supported a't an upper level and adapted to deliver the articles to be stacked into a trap which in turn is automatically operated to deposit the articles received therein onto an elevator platform situated therebelow. As the successive articles are deposited, one on top of the other, on the elevator, the elevator is automatically lowered in a step-by-step manner" until it reaches its bottom level where a second conveyor removes the stack of articles from the elevator platform, after which the elevator is automatically returned to its upper level for the reception of another stackof articles.

It is a primary object of this invention to produce a stacking machineof the class described wherein the energy accumulated through the downward movement of the weight of the article over a predetermined distance is stored and subsequently used to return the elevator to its upper level below the trap.

More specifically, my invention contemplates a self-energizing stacking machine in which all of the power required for operating the machine is obtained from the weight of the articles themselves moving downwardly through a predetermined distance during the stacking operation. In this connection, my invention further contemplates a new and improved form of elevator which is for uniqdirectional operation in that the weight carried by the elevator is always transposed from an upper level to a. lower level and in which such weight is utilized to generate the necessary power to raise the elevator toits upper level when empty.

It is a further object of this invention to provide an` elevator and a stacking machine of the class described in which the elevator and the trap are operated hydraulically, andin .this connection it is a still further object of this invention to provide an elevator of the class described with means for automatically replacing any pressure uid which might leak from the system so as to maintain the proper pressure conditions.

The mechanism for operating the elevator in the device contemplated by this invention consists in a general way of a hydraulic cylinder and pneumatic cylinder, these' two cylinders being interconnected at their bottom portions by means of what I may term a discharge conduit anda pressure conduit. The discharge conduit is provided with a check valve adapted to permit the flow of pressure fluid from-the hydraulic cylinder into the pneumatic cylinder and the pressure conduit is provided with a check valve adapted to permit the discharge of pressure uid from the pneumatic cylinder into the hydraulic cylinder. The pneumatic cylinder contains a compressible fluid such as air which is under a normal pressure lsuiiicient to hold the elevator at'its upperlevel, an'd the discharge conduit is provided with control valve means associated with operating means which in turn are actuated by an` article received in the trap, such operating means being effective to normally hold the valve closed and to open the valve by an article received in the trap. In this way-an article received in the trap is effective to establish communication between -the hydraulic cylinder and th'e vpneumatic cylinder so that the weight of such 4article, when it is-deposited upon the elevator, forces pressure fluid from the hydraulic cylinder into the pneumatic cylinder, thereby permitting the elevator to lower and effecting a partial compression of the pressure uid in the pneumatic cylinder. 'I'his continues in a step by step manner as each successive article is received in the 'trap until the complete stack has accumulated on the elevator when it reaches its lower level. At this point the stack of articles is removed by the lower conveyor and at the same time the elevator, when it reaches its lower position, is effective to close a control valve in the pressure .conduit so that the pressure accumulated in the pneumatic cylinder is applied to the hydraulic cylinder.l As soon as the stack of articles is removed from the elevator such accumulated pressure becomes effective to lift the elevator to its upper level where it is again balanced by the normal pressure in the pneumatic cylinder.

Inasmuch as the accumulating weight on the elevator is effective to produce a corresponding increase in pressure which in turn would normally be followed by an increase in the speed of the downward movement of the .elevator, I consider it desirable to provide means for4 controlling the speed so that it is substantially constant. In this form of my invention such means comprises a pressure` control valve positioned in the discharge conduit and adapted to restrict or obstruct the passage through such conduit as the pressure therein increases.

Although the machine contemplated by this invention may embody a mechanically operated trap or any other type of trap which will automatically deposit the articles onto the elevator platform as they are received therein, I consider it preferable for smoothness in operation and ease in control to employ a trap which is maintained in its closed position by hydraulic pressure from the discharge conduit. The trap contemplated by this invention is so constructed that the Weight of the articles received therein will open the trap.

It is another object of this invention to provide a machine of the class described with an improved safety switch which will be effective to stop the trap delivery conveyor in the event a second box or article is delivered to a point adj acent the trapbefore a rst article has been deposited from the trap onto the elevator or before the trap is closed.

The details in the construction of a preferred form of my invention, together with other objects attending its production, will be best understood from the following description of the accompanying drawings, which are chosen for illustrative purposes only, and in which Fig. l is an elevational view with parts broken away showing a preferred form of my invention;

Fig. 2 is an end elevation which may be considered as having been taken in the plane reprelsented by the line 2-2 of Fig. l;

Fig. 3 is a plan .view of the device shown in Fig. 4 is a rear elevation taken in the direction of the arrow 4 in Fig. 3;

Fig. 5 is a perspective view showing one set of valve operating levers;

Fig. 6 is another perspective view showing a set of valve actuating levers which co-operate with the lever members shown in Fig. 5;

Fig. 7 is a fragmentary end view which may be considered as having been taken in the direction of the arrow 1 in Fig. 2;

Fig. 8 is an enlarged view with parts broken away showing details in the construction of a preferred form of hydraulic trap control mechanism;

Fig. 9 is an enlarged fragmentary view with parts in section showing a preferred form of automatic pressure liquid supply mechanism; and

Fig. 10 is a sectional elevation on the line IU-IU of Fig. 9.

More particularly describing the invention as herein illustrated, reference numeral I I indicates what I may term an upper or a trap delivery conveyor adapted to deliver articles such as crates or boxes I2 into a trap generally indicated by reference numeral I3. The trap I3 is automatically elective to deposit the articles so received onto an elevator generally indicated by reference numerai I4. Under the Weight of the articles dcposited on the elevator, the elevator lowers ina step-by-step manner, as will be hereinafter more completely described, until it reaches its lower level where the bottom of the stack of articles, generally indicated by reference numeral I5, is deposited on what I may term a lower conveyor generally indicated at I6. This lower conveyfr is in continuous operation and is effective to draw the stack of articles oif the elevator platform after which the elevator is automatically raised to its upper level and the general process just described is repeated.

In this form of my invention, the upper or trap delivery conveyor II consists of a pair if side rails I8 and I8' which are suitably supported at the desired elevations, such rails constituting the supports or a plurality of roller members generally indicated at I 9 and I9'. Roller members I9 are live rollers, being provided with sprocket wheels 20 over which chains 2| extend and are driven from any suitable source of power such as the motor indicated at 22 and the belt and pulley indicated at 23. The last live roller indicated at I9a is provided with a pair of spaced belt members 24 and 24' which extend over a pulley 25 an 'l are adapted to feed the articles into the trap I3.

The motor 22 which drives the conveyor system is controlled by a conveyor arresting switch 23 situated above the run of the inner end of theconveyor. Associated with this switch is a lever member 21 which has a projecting end extending out over the path of the boxes or articles traversing the conveyor. Inthe event the trap is open, or in the event an article is contained therein, or if for any reason an article becomes jammed in the trap, it is important that means be provided to automatically stop the conveyor, and the switch and lever member justreferred to constitute such means, since if a box traversing the inner end of the conveyor is lifted into engagement with the lever 21 such lever will be effective to throw the switch and the switch and lever become operative as a conveyor arresting means by stopping the motor 22.

In order to complete this safety device it is necessary to provide some means in the conveyor for lifting the box to a point at which it will engage the lever 21 when the trap is occupied or before the trap is closed. In yother words means must be provided for giving operative effect to the conveyor arresting means. Such means is in the nature of a movable member positioned in the path of oncoming articles in the conveyor and, in this form of my invention, comprises a tongue 28 which is pivotally mounted at 29 across the conveyor and is positioned in the center portion of the conveyor beneath the path of the articles which pass therethrough. For the purpose of elevating this tongue to raise an article into engagement with the lever 21, I provide a cross shaft 30 situated near the inner end of the trap, .such shaft being equipped with a crank 3| having a link 32 attached to the bottom of the tongue. The outer end of the shaft 38 is provided with an arm 33 which is connected to a link 34 wit.1` another arm 34 which in turn is keyed to whal l I may term themain actuating shaft 35, such shaft being mounted in bearings 36 which are provided on top portions of standards 31 and 31' which in turn constitute a portion of the elevator mechanism and also support one side of the trap. Theetheri side of the trap is supported' by similar standards 38 and 38' which in this form of -my invention also constitute a support for one end of the conveyor rails I8 and I8'.

The portion` of the shaft 35 Within the trap l carries what Iinay term a lever member 48 which is keyed to the shaft andthe shaft is biased inwardly, by means which will be hereinafter more fully described, so that the lever member when engaged by an article 'received in the trap will be swung in the direction of the arrow A of Fig. l, thereby pulling the link 34, and swinging the shaft 35 so as to elevate the tongue so that an article positioned thereover or moving into such position will be brought into engagement with the lever member 21 as indicated in broken lines in Fig. 1. It will be seen that this operation is effective to stop the conveyor and prevent further delivery of articles into the trap. As will be observed from Fig. 3, the tongue 28 is of a substantial length and from the broken line position of the tongue 28 shown in Fig. 1, it will be seen that it is inclined into a position above the plane of the conveyor members 24--24' and I9'. From this it will be apparent that a box positioned above the rear portion of the tongue with its front end at or behind .the broken line D (Fig. l) it will ,be elevated out of contact with the conveyor members and'its progress stopped, without contacting'the lever 21 to stop the conveyor. In the event this occurs the rear end of such a box will be engaged by the front of the next box or series of boxes being advanced by the conveyor, the forward movementof such box or boxes (depending on the length` and angle of the tongue), being effective to advance the rst box into engagement with the lever 21 to stop the' conveyor.

It will be understood .that this operation, just described,` actually occurs only in case of -emergency since the boxes are placed on the delivery conveyor at a rate such that the trap can open and close depositing the articles onto the elevator before a second box reaches a position in front 4of the trap.

The construction of the trap itself may be varied to suit the particular type of the article which is to be handled by the machine.v It is an important feature of this invention however that the trap is constructed so that it is automatically opened by the weight of an article received therein. In this form of my invention the trap is shown as comprising a pair of shafts 43 and '43 which are pivoted in

bearings

44 and 44 on Aopposite sides of the trap frame. Fixedly mounted on each of the shafts 43 and 43' are a pair of spaced arms indicatedat 45 and 45', respectively. The

arms

45 and 45 comprise downwardly and inwardly extending sections which are followed by vertical sections, the last mentioned sections carrying a cross member 46 in which inwardly extending fingers are mounted. Such fingers, indicated by reference numerals 49 and 43', extend inwardly below the path of the articles to be received in'the trap so as to support them in the manner indicated in broken lines inA Fig. 2. It will be observed that the peculiar shape of the

arms

45 and 45 is effective to locate the pivotal axis of each set of arms at a substantial distance outside of the line of force applied to the

ngcrs

49 and 49 by the weight of a box received thereon, so that the weight of the box, as pointed' out above, is eiective to automatically open the indicated at I A pivot member which connects the levers at the point 5I is in turn connected to a vertical piston'rod 52, the lower end of which is provided with a piston 53 contained in a cylinder 54, the top of which is provided with a packing gland 55 through which the piston rod extends. As will appear from the description of the elevator operating means, this piston and cylinder mechanism constitutes hydraulic means for closing the trap and holding the same closed until an article is received therein. For the purpose of assisting in the opening movement of the trap during the arrival of the rst article therein I may provide the

shafts

43 and 43 with xed lever arms 51 and 51', the upperends of which are interconnected by means of a tension spring 58.

I will now describe the elevator I4 and its associated mechanism.v This elevator consists of a platform 60 which is mounted on the upper end of what I may term a piston rod6l which constitutes a portion of means which will hereinafter be referred to as piston means. 'I'his piston rod extends through a packing -gland 62, the top of what I may term a hydraulic cylinder 63, and is provided with a piston member 64 within the cylinder. The bottom of the hydraulic cylinder 63 is equipped with an inlet-outlet conduit or a pressure-discharge conduit 66 which is connected through, a T-fitting 61 with a discharge or outlet conduit 68 and an inlet or pressure conduit 69.

Reference numeral indicates what I may term a pneumatic cylinder. The discharge conduit 68 is shown Vas extending through the top of such cylinder into the bottom portion thereof so that it is below the normal liquid level therein and the pressure conduit 69` is shown as being connected into the bottom of the pressure cylinder.

It will thus be seen that the pneumatic cylinder and the hydraulic cylinder, together with their associated conduits, constitute a closed system so that when liquid is provided therein in suflicient quantity to rise above the bottom of the discharge conduit 68 the entire system can be maintained under pressure. In the operation of -this device I provide the pneumatic cylinder with a compressible gas such as air under a pressure (of, say 40 pounds) suflicient to counterbalance and support the piston 64' with its associated elevator mechanism at a position where the elevator is at its uppermost level immediately below the trap when it is empty. This compressiblefluid may be supplied from any suitable source through a valve indicated at 12, a gage 13 being provided for the purpose of indicating the pressure in the pneumatic cylinder.

From the construction so far described it will be seen that, when weight is applied to the platform 60 of the elevator, such weight will be effective to press the elevator downwardly, forcing the hydraulic fluid from .the cylinder 63 through the conduit 68 and a check valve 14 therein which is positioned so as to permit the uni-directional flow of uid from the hydraulic cylinder into the pneumaticrv cylinder 10. This downward movement of the elevator will .thus continue until the weight on the platform is counterbalanced by the pressure developed in the compressible fluid contained in the pneumatic cylinder. In a machine for stacking articles such as is contemplated by this invention, it is important that the downward movement of the elevator take place in a step by step mannerso that the elevator is stopped at a position at which the top of the article received thereon lies in a plane just below the bottom of the trap so that the trap is closed after the top of the article has 'cleared its closing position. For the purpose of intermittently stopping the elevator in this manner I provide the discharge conduit 68 with what I may term a first valve 80, which is normally held in a closed position by means of a tension spring `8| and is adapted to be opened by means of a link 82 connected with one arm 83 on a lever member 84'which is rotatably mounted on the shaft 35. This lever member 84 has another arm 85 which is connected through a link 81 with an elevator return control lever 88. The lever 88 is in a bracket 90 mounted across standards 9|, 9|' and constitutes a part of the elevator frame. Spring and nut means, generally indicated 'at 92, are provided on the pin 89 for .the purpose of holding the lever 88 in position. This lever system just described is used in controlling the upward movement of the elevator and its operation will be taken up in detaillater in the specification. l

For the purpose of actuating the valve 80 by an article received in the trap which, it will be remembered, is eiective to push the lever 40 and lrotate theshaft 35, I provide on the shaft 35 a xed collar member 94 which is provided with a finger 95 extending behind the lever 83, such finger being provided with an adjustable screw 96 adapted to engage, the lever member 83.- It will thus be seen that, when an article is received in the trap and engages the lever 40 to rotate the shaft 35, such rotation will be effective to swin'g the finger 95 so as to engage the lever 83, thereby swinging the valve 80 and opening the same against the action of the tension spring 8|. The lever member 40 is made of a length such that it is engaged by the article until the latter has reached a position where the top thereof is below the closing plane of the trap. In this way the` lever member 40 is permitted to swing back to its normal position under the action of the tension spring 8| when the box reaches a position where the trap will be clear to close.

As was previously pointed'out, cylinder 54 and the piston I3 are provided for the purpose of closing thetrap and holding the same closed until an article is received therein. This is accomplished by connectingl the piston member 54 through a conduit |00 with a T-tting 0| positioned in the conduit 68 between the valve 80 and the hydraulic cylinder 63. It will thus be observed that when the valve 80 is closed the bottom of the piston 53 is subjected to the pressure of the hydraulic cylinder resulting from the weight on the platform 60. In order that there will be `no substantial opposition to the downward movement of the piston under the weight of an article in the trap when the valve is opened, I connect the top of the cylinder 53 with thepneumatic cylinder 10 below the liquid level .therein through the medium of a conduit |04.

It will be apparent that, as the weight on the elevator increases with the deposition of each article thereon, the pressure in the hydraulic cylinder 83 will increase and this would normally be followed by an increase inthe speed of the downward movement of the elevator. It is desirable, however, that the elevator travel at a substantially constant speed andgfor .the purpose ofl eecting this, Ilprovide the conduit 68 with' what I may term a pressure controlledvalve|06 which is adapted to be actuated by means of a piston member |01 in a cylinder |08 which in turn is subjected tothe pressure of the fluid in the conduit 68 through' the medium ofv a connection |09. The pressure valve therefore'is effective to obstruct or partially restrict the passage through the.conduit 68 as the pressure of the liquid in such conduit increases.

From the construction so far described it will .beapparent that the compressible fluid in the pneumatic cylinder 101s' compressed by the weight of the articles on the elevator moving downwardly through their distance of travoltol such an extent that there is sufficient pressure in the cylinderl to lift the elevator when it is .matic cylinder into the hydraulic'cylinder.

`pivotally mounted on a pin 89 which is secured empty. In a device which does not embody'A the trap and which is not used for stacking -articles Such as would be used merely for the purpose of vcarryingl one article from one upper level to a.

lower level, it will be seen that a single conduit connecting the hydraulic cylinder and the pneumatic cylinder would be suflicient to apply the pressure of the pneumatic cylinder to the piston in the hydraulic cylinder and raise the elevator.A

ythe hydraulic cylinder entering the pneumatic cylinder through the, discharge conduit during the downward movement of the elevator, I provide the pressure conduit with a check valve indicated at ||0 which is mounted so as to permit uni-directional movement of the liquid from the pneu- In this way the check valves 14 and ||0 control the movement of the pressure liquid so that it travels from the hydraulic cylinder into the lpneumatic,

cylinder through conduit 68 during the down-- In operating a machine of the class described for the purpose of stacking articles it is necessary that the trap be maintained in its closed position during the upward movement' of the elevator even though an article may be received therein. Also, it is important that the trap be permitted to' open `as soon as the elevator reaches its upper,- most position. In other words, it is necessary for the successful operation of this machine that a ,valve be closed between the connection |0| and the pneumatic cylinder during the upward movement of the elevator and, if a box is received in.

the trap, the trap during such period in the operation of the machine, mustbe held closed by the hydraulic pressure on the bottom of the piston 53 until the elevator reaches its uppermost position. As soon as the elevatorreaches its uppermost position, however, and assuming that a box is received in the trap, it is important that the trap be permitted to open. In other words, that open communication be established between the fittingA |0| and the pneumatic cylinder, but, if an article has not yet been received-in the trap, it is important that a valve be retained in its closed position until an article -is received.

For the,..purpose,.,of satisiactorilycarrying out is connected through a link |20 with an upwardly extending arm |2 -on a collar member |22 rotatably mounted on theshaft 35,

TheV collar member 22 is provided with a forwardly extending arm |23 'which is connected through a link |24 with a lever member |25, such lever member being pivotally mounted on the lever' member 88 as indicated at |26 and the lever member 88 is provided with-a nger |29 which extends over the top of the lever |25 and is adapted to pull the same down when the lever member 88 is pulled down. The lever member' 88, however, is free to move upwardly with respect to the lever member |25. Throughfthe action of the linger means of a control bar |30 which extends downwardly along the elevator frame where, its lower end is slidably received in a socket |32.

The bottom portion oi the controlbar is provided with a stop member |33, adapted to be engaged by a projecting arm |34 mounted on the back of the elevator piston rod 6|. It will thus be seen that when the elevator reaches the lower limit oiits travel the bar |34 engages the stop' |33, pulling the control bar |30 downwardly, thereby swinging both levers 08 and |25, such movement in turn being eifective to swing the collars 84 and |2| on the shaft 35 which in turn is effective to close the valve 36 and open the valve 80.

As soon as the stack of articles has bee-nremoved from the elevator platform by conveyor means I5 and |5' the accumulated pressure in the pneumatic cylinder is effective to force the tion, and as soon as the elevatorstarts its upward movement and the stop |33 is free of the arm |34, the lever member 80 is free to swing upwardly'under the action of the tensionv spring 8| by virtue of the -sliding connection |31 between the link 61 and the lever arm 83. In other words, .the

valve 60 is immediately closed as soon `as the elevator starts its upward movement and is not opened again until an article is received in. the trap. vIn this way the trap is held in its closed position for the reception of an article, even though the elevator may have been raised to a point at which the stop arm |34 engages the bottom oi the lever member |25 to swing the same and open the valve 66.l It will also be apparent that an article received in the trap, during the upward movement of the elevator, will not open the trap due to the closed valve 36. I

In order to avoid any possible sluggishness in the downward movement of the elevator when the first box or article is placed thereon, I provide the back of the frame with a pair oi.' tension upward movement of the elevator at the top of its travel for a distance corresponding substantially to .the height of one o! the articles.V In this way the tension of the springs co-operates with the weight of the rst article to speed up the downward movement of the elevator during its initial operation.

It will seen from the construction as described t at the compressible uid in the pneumatic cylinder 10 constitutes what is in eiect a counterbalance for the weight of the elevator and its associated parts, so that the elevator will travel downwardly under the weight of an article placed thereon andwill be moved up to its top normal or top position'by the action of this counterbalance when the elevator is empty.

It has previously been stated that this invention has as one object the automatic replacement of l any pressure liquid, which might leak through the glands and ttings of the system during its operation, so as to maintain a constant #counterbalancing pressure" at all times. This object is accomplished through the mechanism generally indicated at |50 in Fig. 1 and shown in detail in Figs. 9 and 1|).4

In operation, it is seen that a substantial pres'- sure will be applied to the high pressure" end of the cylinder |5| during the downward movement .of the elevator, thereby pushing the piston* toward the low pressure" end, and during the upward movement of the elevator, when the pressure liquid is wing from the pneumatic cylinder into the hydraulic cylinder through pipe 69, suction or a materially lesslpressure will lbe ap'- plied to the high pressure endof cylinder |6| -thereby permitting the spring |55 to push the iioating piston |54 toward the high pressure" end of the cylinders and cause liquid from reservoir |66 to flow into the cylinder |5|.

Assuming, now, that the valve |10 is setl to` open under a pressure of 40 pounds or more it will be seen that as long as the pressurel from cylinder 10 against check valve |63 is greater than 40 pounds the liquid in the cylinder, following the path of least resistance during the "pressure stroke of the plunger |54 will merelyv circulate through the check valve |10'back into the reservoir |68. If any liquid has leaked from the elevator system, however, sothat the pressure in cylinder 10 is at any time less than 40 pounds, the check valve |10 will be held closed by the action of the spring |1|, and liquid will be forced through check valve |56 into cylinder 10 until the pressure is reestablished therein.

It will thus be seen that thismechanism constitutes means for automatically replacing presuppermost box with its upper level immediately in Fig. 1, with the elevator platform 68 held in its uppermost position by virtue of the air pressure in the pneumatic cylinder 1.0, the valve being held in its closed position by the tension spring 8| and the valve 86 being open so that the trap is held in its closed position by virtue of the piston member 53, it will be observed that as the box I2 is advanced into the trap by the conveyor member 24, it advances into engagement with the lever 48, swinging the same in the direction of the arrow A, to open the valve 80 and raise the tongue 28 in its broken line position. When the valve 80 is open, the cylinder 54 is free to discharge back into thepneumatic cylinder, and as pointed out above the shape of the arms, which carry the fingers 49 and 49' supporting the box, is such that the weight of the box is effective to swing the arms and open the trap against the action of the fluid in the cylinder 54. As the trap is opened, the box is deposited onto the platform and its weight depresses the elevator forcing hydraulic uid from the cylinder 63 through the

conduits

66 and 68, through the open valves 8|) and 8|, and back'into the pneumatic cylinder. The downward travel of the elevator continues as longl as the box is engaged with the lever 40 and holds the same in its valve opening position. When the lower end of the lever is cleared by the top of the box, the lever is swung back into the inclined position shown, thereby closing the v alve 80 and permitting the tongue 28 to drop into its normal position. As has also been pointed out above, the length of the lever 40 is such that the position at which the elevator is stopped supports the below the level of the trap. As successive boxes are delivered into the tra'p the elevator is depressed in a step by step manner until the stack reaches the point indicated in broken lines in Fig. 1, where the lowermost box rests upon the bottom conveyor represented by numerals I6 and I6. The bottom conveyor is immediately eil'ective to withdraw the stack from the elevator platform and, in the meantime, the projecting arm |34 has engaged the stop |33 on the rod |30 to swing the lever 88 and its associated lever |25 downwardly, thereby closing the valve 86 and holding the valve 80 open. As soon as the stack of boxes has been removed from the elevator platform, the pressure in the pneumatic cylinder is eiective to start the ascent of the piston 64 and its associated parts. When the rod |34 has been raised away from the stop member |33, the rod |34 is free to be swung upwardly under the action of the tension spring 8| which closes the valve 80. Since the lever member l|25 and 88 are free to have relative movement with respect to each other, and in view of the frictional resistance in the valve 86, this latter valve is held in its closed position while the valve 88, as pointed out above, is permitted also to close under the action of the spring 8|. In this way, in the event a box is not delivered into the trap before the elevator reaches its uppermost position the conduit 68 will be in a closed position at the time the valve 86 is opened by the engagement of the arm |34 with the upper lever member |25. If, in the meantime, a box is received in the trap, the lever member 40 is swung back to its valve opening position. Since the trap is held closed by virtue of the check valve 14, and the valve 86, during the entire upward movement of the elevator, it is impossibe for the trap to be opened by a box received therein until the valve 86 is opened in the manner described abowAJ vThe valve |06, as pointed out above, controls the speed of the downward travel of the elevator and, in the event any pressure fluid leaks at any point in the system during its operation, such fluid is replenished to maintain the proper pressure in the pneumatic cylinder by virtue of the pressure equalizing unit indicated at |50. In the event the trap is held open by a broken box, or in the event the rate at which the boxes are placed on the conveyor is greater than the rate at which the elevator is traveling downwardly to receive the boxes, the tongue 28 is eiective to operate the safety switch 21, thereby preventing a box being delivered into the elevator when the latter is open. I

It is to be understood that, while I have herein described and illustrated one preferred form of my invention, the invention is not limited to the precise construction described herein but includes within its scope whatever changes fairly come within the spirit of the appended claims.

I claim as my invention:

1. In a stacking machine the combination of a trap adapted to receive articles to be stacked; elevator means for receiving articles from said trap; conveyor means for delivering articles into said trap; means including a switch for operating said conveyor; a lever positioned above said conveyor for throwing said switch; a tongue in said conveyor for lifting an article on said conveyor into engagement with said lever; and means actuated by a rst article received in said trap for raising said tongue whereby a second article in said conveyor above lsaid tongue will engage said lever vand throw said switch.

2. A stacking machine embodying: a trap; an elevator below said trap; hydraulic means for actuating said elevator; a pneumatic cylinder; a discharge conduit leading from said hydraulic means to said pneumatic cylinder; a normally closed valve in said discharge conduit; and means actuated by an article received in said trap for opening said valve thereby establishing communication between saidA hydraulic means and said pneumatic cylinder.

3. A self energizing elevator embodying: a hydraulic cylinder containing a liquid; a piston member in said hydraulic cylinder supported on said liquid; a weight receiving platform on said piston member; a pneumatic cylinder containing a liquid and a gas under sufficient pressure to lift the weight of said piston member and its associated parts to a predetermined level; a conduit for delivering liquid from the bottom of said hydraulic cylinder into said pneumatic cylinder; a valve in said conduit; additional conduit means for conducting liquid from said pneumatic cylinder to said hydraulic cylinder; and a check valve in said last mentioned conduit adapted to automatically open when the pressure in.the pneumatic cylinder is greater than the pressure in said hydraulic cylinder.

4. A self energizing elevator embodying; a hydraulic cylinder containing a. liquid; a piston member in said hydraulic cylinder supported by the liquid therein; a weight receiving platform supported by said piston member; a pneumatic cylinder containing a liquid and a gas under sufficient pressure to lift the weight of the hydraulic piston and its associate parts to a predetermined level; a conduit for delivering liquid from thebottom of said hydraulic cylinder into said pneumatic cylinder at a point below the level ofthe liquid therein; a valve in said con` from said pneumatic cylinder to said hydraulic cylinder; and a check valve in said last mentioned conduit adaptedto .automatically open when the pressure in said pneumatic cylinder exceeds the pressure in said hydraulic cylinder.

5. A self energizing elevator embodying: a hydraulic cylinder containing a liquid; a piston member in said hydraulic cylinder supported by the liquid therein; a weight receiving platform. supported by said piston member; a pneumatic cylinder containing a liquid and a gas under vsufilcient pressure to lift the weight of the hydraulic piston and its associated parts to a predetermined level; a conduit for delivering liquid from the bottom of said hydraulic cylinderA into said pneumatic cylinder at a point below the level of the liquid therein; a valve in said conduit; yieldable means for holding said valve closed; and means including a lever actuated by an article received on said elevator ior opening said valve whereby the weight of said article is effective to depress said elevator and compress said compressible fluid in said pneumatic cylinder; additional conduit means for conducting liquid from said pneumatic cylinder to said hydraulic. -cyl inder; and a check `valve in said last mentioned conduit adapted to automatically open when the pressureV in said pneumatic cylinder exceeds the pressure in said hydraulic cylinder.

6. A machine for stacking articles embodying: a hydraulic cylinder containing aiiquid; a piston member in said hydraulic cylinder supported by the liquid therein; an elevator platform supported by said piston member; a pneumatic cylinder containing a liquid and a gas under suficient pressure termined level; a discharge conduit for delivering.'

holding said valve closed thereby preventing the opening of said trap `and the release of pressure iluid from said hydraulic cylinder to said pneumatic cylinder; and means actuated by an article received in said trap for opening said valve, thereby permitting the opening of said trap and to counterbalance the weight of said piston and its associated parts at a prede-j the downward movement of said piston and elevator. A

*'7. A machine for stacking articles embodying: a hydraulic cylinder containing a liquid; a piston member in said hydraulic cylinder supported by the liquid therein; an elevator platform supported by said piston member; a pneumatic cylinder containing a liquid and a gas under sufrlcient pressure to counterbalance `the weight of said piston and its associated parts at a predetermined level; a discharge conduit for delivering liquid from the bottom of said hydraulic cylinder into Vsaid pneumatic cylinder at a point below the level of the liquid therein; a trap situated above the upper level of said platform for receiving articles to be stacked and releasing same onto said elevator; hydraulic means communicating with said discharge conduit for holding said trap closed, a valve in said discharge conduit; means normally holding said valve closed thereby prey venting the opening of said trap and the release of pressure uid from said hydraulic cylinder -to said pneumatic cylinder and means including a lever member adapted to be `engaged by an article received in said trap for opening said valve thereby permitting the opening of said trap and the downward movement of said piston and elevator; said lever being of a length such that it `will clear said article when the top thereof has descended to the level of the bottom of said trap. 8. A machine for stacking'articles embodying: a hydraulic cylinder containing a liquid; a pistonv member in said hydraulic cylinder supported by the liquid therein; an elevator platform 'supported by said piston member; a pneumatic cylinder containing a liquid and a gas under sufcient pressure to counterbalance the weight of said piston and its associated parts at a predetermined level; a discharge conduit for delivering liquid from the bottom of said hydraulic cylinder into said pneumatic cylinder at a point below the level of the liquid therein; a trap situated above the upper level of said platform for receiving articles to be stacked and releasing same onto said elevator; a valve in said discharge conduit; means normally holding said valve Iclosed thereby preventing the release of pressure iluid from said hydraulic cylinder to said pneumatic cylinder; means actuated by an article received in said trap for opening said valve; a return conduit connecting the bottom of said pneumatic cylinder with the bottom of said hydraulic cylinder; and a check valve in said return conduit arranged to permit flow of liquid from said pneumatic cylinder to said hydraulic cylinder, whereby the pressure in said pneumatic cylinder is effective to raise said piston when theweight of said articles has been removed from said platorm.

9. A stacking machine embodying: a hydraulic cylinder; a piston member in said cylinder; an elevator platform supported by said piston member; a trap situated above the upper level of said platform and adapted to receive articles to be stacked; means supporting said trap; a pneumatic cylinder containing a compressible fluid under sumcient pressure to support said elevator at its upper level when empty; a discharge conduit for deliveringv liquid from the bottom of said hydraulic cylinder into said pneumatic cylinder; a valve in said conduit; hydraulic means communicating with said conduit at a point between'said valve and said hydraulic cylinder for'maintaining said trap closed; and means actuated by an article received in said trap for opening said `valve whereby the weight of said article is eiectlve to open said trap.

10. A stacking machine embodying: a hydraulic cylinder; a piston member in said cylinder; an elevatorplatform supported by said piston member; a trap situated above the upper, level of said platform and adapted to receive articles to be stacked; means supporting said trap: a pneumatic cylinder containing a compressible fluid under suilicient pressure to support said 'elevatorat its upper level when empty; a discharge conduit for delivering liquid from the bottom of said hydraulic cylinder-into said pneumatic cylinder; a valve in said conduit; hydraulic means communicating with said conduit at a point be- -tween said valve and said hydraulic cylinder for maintaining said trap closed; means actuated by an article received in said trap for opening said tive to open said trap and permit the deposition of said article onto said platform; and means for closing said valve after a predetermined downward movement of said elevator whereby ,the pressure in said conduit from said hydraulic cylinder is effective to close said trap.

11. A stacking machine embodying: a hydraulic cylinder; piston means Vin said cylinder; a platform supported by said piston means; a pneumatic cylinder; a discharge conduit connecting said cylinders; a check valve in said discharge conduit permitting the flow of uid from said hydraulic cylinder to said pneumatic cylinder; a pressure conduit connecting said cylinders; a check valve in said pressure conduit permitting the return of pressure uid from said pneumatic cylinder to said hydraulic cylinder; trap means for receiving articles to be stacked ,and depositing same on said elevator platform; a valve in said discharge conduit; means actuated by an article received in said trap for opening said valve thereby permitting downward movement of said piston under the weight of said article; and means for closing said valve when the top of the uppermost article on said platform has reached a predetermined point.

12. A stacking machine embodying: a hydraulic cylinder; piston means in said cylinder; a platform supported by said piston means; a pneumatic cylinder; a discharge conduit connecting said cylinders; a check valve in said discharge conduit permitting the ow of fluid from said hydraulic cylinder to said pneumatic cylinder; a pressure conduit connecting said cylinders; a check valve in said pressure conduit permitting the return of pressure iluid from said pneumatic cylinder to said hydraulic cylinder; a trap means for` receiving articles to be stacked and depositing same on said elevator platform; a valve in said discharge conduit; means actuated by an article received in said trap for opening said valve thereby permitting downward movement of said piston under the weight of said article; means for closing said valve when the top of the uppermost article on said platform has reached a predetermined point; and a pressure actuated valve in said discharge conduit for obstructing f the passage therethrough as the fluid pressure increases.

13. A stacking machine embodying: a hydraulic cylinder; piston means in said cylinder; a platform supported by said piston means; a pneumatic cylinder; a discharge conduit connecting said cylinders; a check valve in said discharge conduit permitting the flow of fluid from said hydraulic cylinder to said pneumatic cylinder; a pressure conduit connecting said cylinders; a check valve in said pressure conduit permitting the return of pressure fluid from said pneumatic cylinder to said hydraulic cylinder; trap means for receiving articles to be stacked and depositing same on said elevator platform; a first valve in said discharge conduit; means actuated by successive articles received in said trap for opening said first valve; means for successively closing said rst valve as the top of the uppermost article on said platform reaches a predetermined point below said trap; a second valve in said discharge conduit; opening and closing means for said second valve; and means associated with said elevator and said opening and closing means for closing said second valve when said elevator reaches the bottom of its travel and opening said second valve when said elevator reaches the top of its travel.

14. A self energizing elevator embodying: a

hydraulic cylinder containing a liquid; a piston member in said hydraulic cylinder supported by said liquid; a weight receiving platform supported by said piston member; a pneumatic cylinder containing a liquid and a gas under a normal pressure sufficient to support said platform and piston at a predetermined level; a conduit for delivering liquid from the bottom of said hydraulic cylinder into said pneumatic cylinder at a point below the level `of the liquid in said pneumatic cylinder; and auxiliary hydraulic means connected with said conduit and operable, under the application of weight to said platform, to automatically maintain a predetermined minimum liquid pressure in said pneumatic cylinder.

15. In a stacking machine, the combination of: a trap adapted to receive articles to be stacked; elevator means for receiving articles from said trap; conveyor means for delivering articles into lsaid trap; means for arresting the operation of said conveyor; a movable member positioned above said conveyor for actuating said conveyor arresting means; means in said conveyor for lifting 'an article on said conveyor into engagement with said movable member; and means actuated by a` first article received in said trap for raising said article lifting means whereby a second article in said conveyor above said lifting means will be raised into engagement with said movable member to actuate the same and arrest the operation of said conveyor.

16. In a device of the class described: an elevator adapted to be lowered bythe weight of an article received thereon; hydraulic means for actuating said elevator; a pneumatic cylinder; a discharge conduit leading from said hydraulic means to said pneumatic cylinder; a valve in said discharge conduit; means for opening said valve to establishcommunication between said hydraulic means and said pneumaticv cylinder, thereby permitting the ow of hydraulic fluid into said pneumatic cylinder and the consequent depression of said elevator -under the weight of an article supported thereon; additional conduit means for conducting liquid from said pneumatic cylinder to said hydraulic cylinder; and a check valve in said last mentioned conduit adapted to automatically open when the pressure in said pneumatic cylinder exceeds the pressure in said hydraulic cylinder.

17. In a device of the class described; an elevator adapted to bel lowered by the weight of an article receivedthereon; hydraulic means for actuating said elevator; a pneumatic cylinder; a discharge conduit leading from said hydraulic means to said pneumatic cylinder; a valve in said discharge conduit; means for opening said 'valve to establish communication between said hydraulic means and said pneumatic cylinder, thereby permitting the flow of hydraulic fluid into'said pneumatic cylinder and the consequent `depression of said elevator under the weight of an article supported thereon; means for closing Said valve to arrest the downward movementv of said elevator; additional conduit means for conkducting liquid from said pneumatic cylinder to l v member actuated by an article received in said trap for opening said valve, thereby establishing a communication between said hydraulic means and said pneumaticvcylinder, said lever member being of a length such that it will swing clear of said article to close said valve when the top of said article has descended to a point just below the level of the bottom of said trap; and yieldable means for swinging said lever to close said valve.

19. For use in a stacking machine ofthe class described, a trap embodying: a frame; a pair yof lower ends of said arms adapted to normally extend horizontally below said guide passage; re-

leasable means for supporting said arms inthe said normal position; and means actuated by an article received in said trap for releasing said arm supporting means, the pivotal axes of said arms being spaced outwardly a substantial distance from the article supporting ends of said ngers, whereby the weight of an article received in said trap is automatically effective to open the same upon the'release of said arm supportingmeans;

20. A stacking machine embodying: a trap; an elevator below said trap; hydraulic means foractuating said elevator; a pneumatic cylinder; a, discharge conduit leading from said hydraulic means to said pneumatic cylinder; a normally closed valve in said discharge conduit; 4means actuated by an article received in said trap for opening said valve, thereby establishingcommunication between said hydraulic means and said pneumatic cylinder; and a pressure actuated valve in said discharge conduit for obstructing the passage therethrough as the fluid pressure increases.

21. The combination of an. elevator adaptedv to be lowered by the weight of articles supported thereon; hydraulic means for actuating said elevator; a pneumatic cylinder; a discharge conduit leading from said hydraulic means to said pneumatic cylinder; a-valve'in said discharge conduit; means for opening .said valve to establish communication between said hydraulic means and said pneumatic cylinder, thereby permitting the flow of vhydraulic fluid into said pneumatic cylinder and the consequent depression of said ele l vator under the weight of articles supported thereon; and a pressure actuated valve in said discharge conduit for obstructing the passage therethrough as the fluid pressure increases.

22. A self energizing elevator embodying: a hydraulic cylinder containing a liquid; a piston member in said hydraulic cylinder supported by said liquid; a weight receiving platform supported by said piston member; a pneumatic cylinder containing a liquid anda gas under anormal pressure sufficient to support said platform and piston at a predetermined level; a conduit for delivering liquid from the bottom of said hydraulic cylinder into said pneumatic cylinder at a point below the level of the liquid in said pneumatic cylinder; and auxiliary hydraulic means connected with said conduit and operai`e, under theapplication of weight to said platform, to automatically maintain a predetermined minimum liquid pressure in said pneumatic cylinder, said last mentioned means comprising an equalizing.

cylinder, means connecting opposite lends of said 4equalizing cylinder 'withsaid pneumatic cylinder and said pneumatic cylinder adapted to open toward said pneumatic cylinder, a piston in said equalizing cylinder, yieldable means in said equalizing cylinder biasing said piston toward said conduit, liquid supply means having an inlet passage communicating with said equalizing cylinder, a check valve in said passage adapted to open toward said equalizing cylinder, said liquid supply means also having a liquid return passage, and an adjustable check valve in said last mentioned passage adapted to open away from said lequalizing cylinder.

23. In an elevator system of the class-described, the combination of: a hydraulic cylinder; a piston Ain said cylinder; a pneumatic cylinder; a discharge conduit connecting said cylinders; a check valve in said discharge conduit permitting -'flow. oi?v iiuid' from said pneumatic cylinder to said hydraulic cylinder; a pressure conduit connecting said cylinders for delivering pressure uid from said hydraulic cylinder to said pneumatic cylinder; a valve in said discharge conduit; means for opening said valve, thereby permitting downward movement of said piston under the weight of an article supported thereby means for closing said valve when said platformhas reached a predetermined point; and auxiliary hydraulic means interposed between said pressure conduit and said pneumaticcylinder and operable under the application of weight to said piston to automatically maintain a predetermined minimum liquid pressure in said pneumatic cylinder.

, 24. In an elevator system of the class described, the combination of: a hydraulic cylinder; a piston in-said cylinder; a pneumatic cylinder; a discharge conduit connecting said cylinders; a check valve in said discharge conduit adapted to open toward said hydraulic` cylinder; a pressure conduit connecting said cylinders for delivering pressure uiii from said hydrauliccylinder to said pneumatic cylinder; valve means insaid pressure conduit for controlling the iiow of iluid therethrough; and auxiliary hydraulic means interposed between said pressure conduit-and said pneumatic cylinder, and operable under the' ap` plication of weight to said piston toautomatically maintain a predetermined minimum liquid pressure in said pneumatic cylinder.

25. In a stacking machine, the combination of: a trap adapted to receive articles to be stacked; elevator means for receiving articles from said trap; conveyor means for delivering articles into said trap; means .for arresting the operation of said conveyo a movable member positioned in4 the path of the oncoming boxes on the conveyor for actuating said arresting means; means in said conveyor for lifting an article on said conveyor to givel operative effect to said arresting means; and means actuated by a iirst article received in. said trap for raising said article lifting means whereby a second article in said conveyor in passing over said lifting means will be raised to eiiect and arrestthe operation of said conveyor.

26. In a stacking machine the combination of a trap adapted to receive articles to be stacked, an elevator for receiving articles from said trap, a conveyor for delivering articles into said trap, and means for arresting the operation of said conveyorcomprising: a normally inoperative conveyor arresting mechanism; a movable member positioned. in the path-of oncoming articles in said conveyor .and associated with said conveyor arthereto; and means actuated by an article in said trap for moving said movable member whereby another article in said conveyor will engage said conveyor arresting mechanism to arrest said conveyor. e

27. In a stacking machine, the combination of a trap adapted to receive articles to be stacked; an elevator for receiving articles from said trap; a conveyor for delivering articles into said trap, said conveyor including travelling members adapted to support and move articles thereon toward said trap; an elongated tongue pivotally mounted in said conveyor and extending forwardly from its axis in the direction of travel of articles on said conveyor, said tongue being normally positioned below the plane of support on said travelling members; means actuated by an article in said trap for swinging said tongue into an upwardly inclined position whereby an article on said conveyor above said tongue is raised out of contact with said travelling members, means for arresting the operation of said conveyor; and means associated with the forward end of said tongue and adapted to be engaged by an article on said forward end for actuating said conveyo arresting means.

28. In combination, a conveyor for delivering articles, said conveyor including driven members adapted to support and move articles thereon, means at the delivery end of said conveyor actuated by an article delivered from said conveyor for raising an article on said conveyor out of contact with said driven members, and conveyor arresting means actuated by an article in raised p0- sitionabove said conveyor. l

29. In combination, a conveyor for delivering articles, said conveyor including driven members adapted to support and move articles thereon, an

v HAROLD C. PIERCE.