US2707315A - Hydraulically-powered automatic brick machine - Google Patents

Description

May 3, 1955 E. R. HERsHEY HYDRAULICALLY-POWERED AUTOMATIC BRICK MACHINE Filed OCT'. 30, 1951 3 Sheets-Sheet. l

IN VENTOR A'ITO EY May 3, 1955 E. R. HERSHEY 2,707,315

HYDRAuLIcALLY-POWERED AUTOMATIC BRICK MACHINE Filed oct. zo, 1951 s sheets-sheet 2 ATTORNE May 3, 1955 E. R. HERsHEY 707,315|

HYDRAULICALLYPOWERED AUTOMATIC BRICK MACHINE Filed oct. 3o, 1951. s sheets-sheet s fr. '111111, l

ATTORNEY United States Patenty O HYDRAULICALLY-PWERED AUTMATIC BRICK MACHINE Elwood R. Hershey, Lancaster, Pa., assigner to Posey Iron Works, Lancaster, Pa., a corporation of Penu- Sylvania Application October 30, 1951, Serial No. 253,907

6 Claims. (Cl. 25m2) This invention relates to automatic brick machines of the type in which a reciprocating push-out plate individually shifts the molds that are delivered in front of the push-out from a sanding mechanism to a position beneath the die of a pug mili where they are titled with mud. The molds are usually elongated and partitioned into a number of compartments so that several bricks may be made in each mold at the same time, and the molds are fed sidewise step-by-step through the machine. The action of the push-out in moving a mold to lling position beneath the pug mill also serves to advance a train or" previously filled molds outwardly toward the discharge end of the machine. Here the molds are inverted for dumping the molded shapes onto pallets, and then the molds are fed back into the machine, sanded and eventually returned to a position in front of the push-out.

In accordance with past practice, the push-out has commonly been operated by means oi' a crank or rocker arm so that the train of molds as they are moved from iilling to discharge positions have been subject to a series of impacts or kicks. Because of the inertia of the plastic mud filling the molds, these impacts cause the mud to surge and pile up against the trailing side of the mold, so that, as a consequence, the top and bottom faces of the shapes discharged from the molds are not truly parallel and one end of the bricks is thicker than the other.

lt is the purpose of the present invention to overcome the above disadvantages by providing hydraulic mechanism for reciprocating the pusheout, such mechanism being so constructed and arranged as to cause the push-out to execute a quick preliminary movement approximately into engagement with the mold and then to impart a slower and uniform movement during its further advance while in contact with the mold. in this way the acceleration of the molds is gradual and the tendency of the mud to shift within the molds is reduced to a minimum.

Another object of the invention is to provide in a hydraulically-powered automatic brick machine of the above character, means for quickly retracting the pushout at the end of its working, or mold-advancing, stroke, ready to begin a new forward stroke.

A further object of the invention is to provide in a hydraulically-powered automatic brick machine of the above character, means for coordinating the hydraulic operation with the mechanical operation of the machine.

Still another object of the invention is to provide in a hydraulically-powered automatic brick machine of the above character, hydraulic means for operating the molddumping mechanism for depositing the molded shapes onto pallets, the dumping mechanism being operable in timed relationship with the push-out mechanism, so that for each forward step of the train of molds a mold is emptied and returned to the machine.

Other objects and advantages will be apparent from 2,707,315 iiatentecl May 3, 1955 the following detailed description of a preferred embodiment of the invention, reference being made to the accompanying drawing in which:

Figure 1 is a simplitied side View of an automatic brick machine, parts thereof being indicated in crosssection, showing the hydraulic system for operating the mold push-out and the mold-dumping mechanisms;

Figure 2 is a schematic View of the mechanical driving means for various parts of the machine;

Figure 3 is a schematic view of the hydraulic system;

Figure 4 is a diagrammatic view of the mold push-out control valve showing its position for effecting the initial portion of the working stroke of the push-out;

Figure 5 is a diagrammatic view of the: mold push-out control valve showing its position for effecting the iinal portion of the working stroke of the push-out; and

Figure 6 is a plan View of the hydraulic system for operating the mold push-out.

The automatic brick machine illustrated in Figure l comprises a machine frame 1 upon which is supported a vertically disposed pug mill 2 and a charging chamber or press box 3 in communication with the pug mill and having a die i adjacent its bottom through which plasticized material, such as mud, is forced by means of a reciprocating platen 5. The mud passes through the die into molds M that are shoved along a bank of resiliently-supported rollers 6 into and out of registry with the die by means of a push-out plate 7 which moves back and forth at an elevation below and in a path located at one side of the die.

The molds are individually presented in front of the push-out plate by an elevating mechanism comprising a sweeper having iingers 8 mounted on a shaft 9 and arranged during their rotation to engage a mold M and move it along a circular track 16 upwardly onto a pair of receiving plates 11. The receiving plates are hinged at one end at a point somewhat in advance of the charging chamber 3 (considered in the direction of travel of the molds into lilling position) and the free ends of these receiving plates ride upon the circumference of a pair of cams l2 secured to shaft 9. The tingers 8, receiving plates l1 and cams 12 are located at opposite sides of the machine so that only one of each is shown in the drawing. The arrangement is such that the cams allow the receiving plates to lower and provide a gap through which the molds pass up onto the receiving plates from the fingers 8 after the push-out has retracted clear of the receiving plates and is about ready to begin another forward working stroke.

The working stroke of the push-out is such as to move `the empty mold into contact with a preceding iilled mold,

moving the latter from under the die 4 and allowing the empty mold to take its place under the die. Thereupon the platen 5 descends to force mud through the die into the mold, completely filling the mold. On the next working stroke of the push-out, the filled mold is slid along a base 13, together with the series of iilled molds that precede it. Thus, during the operation of the machine, the push-out intermittently advances the train of molds step-by-step toward the discharge end of the machine. In their progress the molds encounter a bumping mech anism 14 which taps the ends of the molds to loosen the material preliminary to dumping the shapes from the molds.

At the discharge end of the machine the molds are received by a dumping mechanism, designated generally at 15. The dumping mechanism comprises a pair of swingable members 16 and 17 (each member including arms located at opposite sides of the machine so as to engage the ends of a mold) mounted respectively upon shafts 16a and 17a so as to rock toward and from each other. The construction and arrangement is such that a mold pushed olf the end of base 13 is caught by the swingable member 16 and transferred over onto the swingable member 17, which latter carries a removable pallet P. As the swingable member 17 rocks away from the swingable member 16, the mold is overturned to dump the shapes onto the pallet; and, in the further movement of this swingable member, the mold is intercepted by a series of rollers defining a mold stop 18 fixed to a bracket 18a on the machine frame. The swingable member 17 continues its counter-clockwise movement to deposit the pallet on the olfatake conveyor 19, while the empty mold slides off the mold stop 18 onto a rollway 20 which returns the mold to the machine.

For operating the dumper, the shafts 16a and 17a are provided with intermeshin'gl segmental gears 161) and 17 b, respectively, and these shafts are rocked in unison by means of a reciprocating rack 21 which engages a pinion 22` on shaft 17a, as best indicated in Figure 3.

The empty molds M delivered onto the rollway 2t? pass by gravity to a sanding mechanism 23. The sander comprises a chamber having a circularly-curved bottom, into which sand is fed by a pipe 24 from a sand bin, not shown. Ar pair of laterally-spaced rotary elements 25 is secured to Opposite ends of a rotatable shaft 26 disposed below and approximately in vertical alignment with sweeper shaft 9. During rotation of shaft 26, circumferential abutments on rotary elements 25 moving in an anti-clockwise direction engage the empty molds feeding off the rollway 2() and urge the molds along the curved bottom of the chamber 23 until they are raised into engagement with the fingers 8. The latter thereupon lift the sanded molds onto the receiving plates 11 in a manner that has already been described.

The structure thus far described is not new in connection with automatic brick machines, having been previously disclosed in the United States patents of Henry W. B. Graham, No. 1,341,798 granted June 1, 1920, No. 1,350,604 granted August 24, 1920, No. 1,452,152 granted April 17, 1923, and in No. 1,454,165 granted Nay 8, 1923; and in the United States patent of l ames f- P, Martin, No. 1,779,136 granted October 21, 1930. Reference is made to these patents for a more detailed description of the construction and operation of the various parts of the automatic brick machine.

In the operation of the automatic brick machine the several mechanisms for performing the separate functions of mold filling and mold-handling must be suitably synchronized for the machine to operate in a cyclic manner. for operation in synchronism is best indicated in Fig,- ure 2.

A main drive shaft 27 is journaled for rotation upon the machine frame and extends crosswise thereof. This main drive shaft may be connected to a source of power in anyl suitable manner. Upon the main drive shaft' is a sprocket ZS'and a chain 29 extends around this sprocket and around a companion sprocket 30'on a secondary drive shaft 31v mounted for rotation upon top of the pug mill 2. Al small spur gear 32 on secondary. drive shaft 31 engages a larger spur gear 33' on one end of a countershaft 34 so as to impart rotation to the countershaft. The countershaft carries aV bevel gear 35 which engages a bevel' ring gear 36 which latter, in turn, is connected tothe upper end of a vertical pug shaft 37.

The pug` shaft extends downwardly withinthe pu gv mill, as best shown in Figure l, for agitating'the-mud and irnpeiling it through a doorway 33 into-the charging chamber 3 that is contiguous to the lower end of the pugmill. The platen 5 thatlreciprocates within the charging chamber 3 is operatedby a connecting rod 39 pivoted at one end t'o a cranktln-on a crank shaft 40 and at its other end toa slide link 41" carrying at' its lower end the platen upon its upstrolte to fallow inudfto pass from the'pug mill 2 into the charging chamber 3and, upon itsdbwnstroke,

The manner of interconnecting the various partsa. The platen is solformed asftoopen the doorway 3S to close the doorway and force the mud from the charging chamber into a mold positioned below the die 4. For imparting rotation to the crankshaft fit), the crankshaft carries a large spur gear 42 which meshes with the spur gear .32 on secondary drive shaft 31.

For rotating the sander 23 and sweeper shaft 9, a chain 43 extends between a sprocket te on countershaft 34 at the top of the pug mill and a companion sprocket d5 on sweeper shaft 9. The shaft 9 is geared, in turn, to sander shaft 26 through intermeshing pinions 46 andr #i7 mounted respectively upon these two shafts.

1n the past it has been common practice to operate the push-out and mold dumping mechanisms by some mechanically driven part of the brick machine. Usually the push-out has been operated by a crank so arranged as to impart a swift accelerating movement at the beginning of the push-out stroke and a rapid decelerating movement at the end of the stroke, the push-out attaining its maximum velocity approximately at the moment an empty mold' being shoved into filling position engages a previousiy tilted mold situated below the charging chamber. T his, however, is subject to the disadvantage that by imparting a series of sharp impacts to the train of molds, the mud tends to shift its level within the molds as the latter pass to the discharge end of the machine, resulting in the production of bricks of irregular shape.

.ln accordance with the pres-ent invention this push-out mechanism is operated hydraulically in order tov impart a comparatively slow and uniform movement to the filled molds to avoid, or at least to minimize, distortion of the bricks by reducing to a minimum the disturbance of the surface of the mud within the molds.

Por operating the push-out hydraulicaily there is provided a push-out cylinder 48' in which reciprocates a piston 49 having a piston rod Sti projecting outwardly through one end of the cylinder. At the outer end of the piston rod there is pivotally connected the slidable push-out plate 7. Liquid, such as oil, is admitted to the left-hand end of the push-out cylinder through a pipe 51 (Figure 6) and to the right-hand end of the cylinder through a pipe 52, both pipes 51 and 52 extending between the push-out cylinder andv a four-way push-out control valve 53 contained within a valve housing 54. As best shown in Figure 3, the push-out control valve is slidably positioned, in accordance with the movement of a stem 55 connected thereto and projecting outwardly through one end of the valve housing and acting in opposition to the thrust of a compression spring 56 interposed between the valve and an end of the valve housing.

A primary hydraulic pressure line`57 extends between the push-out control valve housing 54s and a pumpy 58 for supplying liquid under pressure. This pump, as in-V dicated in Figure 2, is driven by a chain 59 extending between a sprocket 60 on drive shaft 27 and a companion sprocket 61 mounted upon a countershaft 62- and, in turn, by a chain 63 extending between a sprocket 64 on countershaft 62 and a sprocket 65 on the drive shaft of the pump 58.

Included' in pressure line 57 between the valve housing 54 on the pump 53 is a manually-adjustable resistance valve 66. Liquid is supplied to the pump 53 from a reservoir tank 67 and the pump impels the liquid through the pressure line 57, past resistance valve 66,- to theV admission side of push-out controll valve 53. The liquid return line from valve housing 54 comprises a pipe 68 leadingback to the tank 67.

For hydraulically operating the mold dumping mechanism 15, pressure liquid is admitted to and removed from a mold dumping cylinder 69 (best indicated in Figure 3) via pipes 70 and 71 communicating with the cylinder on opposite sides of a piston 72 reciprocable within the cylinder. The pistonl 72 is provided upon its opposite faces with rod extensions 73 and 74 of equal diameter whichv project outwardly through oppos'ite'ends of the cylinder, whereby the piston presents equal pressure areas to the liquid admitted into the cylinder from pipes 70 and 7i.

5 The rack 21 is connected to the extension '74 so that reciprocation of the piston within the mold dumping cylinder 69 moves the rack backwards and forwards to impart a rocking motion to the pinion 22 and, hence, to the mold dumping mechanism i5, as has been already explained.

For controlling the admission of pressure huid to and from opposite ends of the mold dumping cylinder 69 through the pipes 70 and 71, there is provided a four-way dumper control valve 7S slidable within a housing 75a, and having a valve stern 76 projecting beyond the housing under the urge of a compression spring 77 acting against the other face of the dumper control valve. A secondary pressure line 78 branches ofi." the primary pressure line 57 and extends to the dumper control valve housing 75a, and interposed in this secondary pressure line is a manually adjustable how-control valve 79. This flow-control valve is of the type which maintains the quantity of liquid passing through it constant for any particular setting regardless of the pump pressure in line 78. Therefore a constant flow of liquid is supplied to the lines 70 and 71 communicating with the mold dumping cylinder 69 under all circumstances. A liquid return line S extends directly from the dumper control valve housing 75a to the reservoir tank 67.

For operating the push-out control valve 53 and the dumper control valve 75 a earn shaft 81 is supported on the machine frame (see Figure 2) and rotated by means of a chain S2 extending between a sprocket 83 on shaft 26 and a sprocket 84 on the cam shaft. Upon the cam shaft are fixedly mounted two cams 85 and S6. The cam 85 is of the three-step type and during the rotation of the cam shaft acts against the outwardly projecting end of the valve stem S (Figure 3) through the intermediary of a pivotally mounted roller 87, for regulating the position of the push-out control valve S3; andcam 36 is of the two-step type and acts against the outwardly projecting end of valve stern 76 for regulating the position of the dumper control valve 75.

The operation of the hydraulic system just described is as follows:

The pump 53 draws liquid from the tank 67 and delivers it under pressure to the primary pressure line 57. As soon as pressure builds up sufiiciently to overcome the opposition of the resistance valve 66, liquid passes through line 57 to the push-out control valve housing 54. The purpose of the resistance valve 66 is to insure pressure build up in line 78, so that all the pressure does not follow the line of least resistance and tiow to valve housing 54.

The contour of the three-step cam 85 is such that dur-- ing each revolution of the cam, in sequence with each stroke of the push-out plate 7, the push-out control valve 53 is moved, in opposition to the spring 56, to different positions within its housing 54 and held in such positions for the proper interval.

During the retracting stroke of push-out plate 7 the valve 53 is so positioned by the cam 85 that liquid flows from primary pressure line 57 through valve housing 54 into pipe 51 and thence into the left-hand end of cylinder 48. At the same time, the liquid that is on the opposite side of the piston at the right-hand end of the cylinder is evacuated through pipe 52, valve housing 54 and exhaust line 68 back to tank 67. The position of valve 53 during this time is indicated in Figure 3.

Continued rotation of cam 85 moves the valve 53 to the position shown in Figure 4 at which time the push out is ready to begin a working stroke in the opposite direction. The new position of the valve puts both ends of the cylinder 48 into communication with the primary pressure line 57 through valve housing S4 and through the pipes 51 and 52, the exhaust port in this valve being closed. Because there is a larger pressure area on the full (right-hand) face of the piston 49 than on its smaller (left-hand) face that is occupied in part by the rod Sii which projects through the end of cylinder 48, this unbal- 7a anced pressure upon opposite faces will cause a movement of the piston to advance the push-out in a working stroke. This movement of the piston for a distance of approximately one-half of the full working stroke of the push-out is rapid since it is moved both by the volume of liquid delivered from pressure line 57 as well as by the volume of liquid displaced from the left-hand end of cylinder 48, which latter passes via pipe 51 through valve housing 54 and pipe 52 into the right-hand end of the cylinder.

As the cam 35 continues to rotate, it shifts the pushout control valve 53 into its third position, shown in Figure 5. At this time the empty mold that has been previously positioned in front of the push-out by the sweeper 8 is moved by the push-out plate to closely adjacent the mold located under the die 4 of the charging chamber and which has already been filled with mud on the previous downstroke of the platen 5. The valve 53 in its new position establishes communication between the primary pressure line 57 and the right-hand side of cylinder 4S, while liquid from the left-hand end of the cylinder is ported to the exhaust line 68 leading to tank 67. The piston continues its forward travel but now at uniform and reduced speed because of the reduction in volume of liquid acting upon the right-hand face of the piston. The filled mold that was under the die 7 will be shoved forward to become part of the train of filled molds advancing step-by-step toward the discharge end of the machine, while the empty mold engaged by the push-out will be positioned below the die 7.

Further rotation of the cam 65 causes the valve 53 under the urge of the spring 56 to be restored to its initial position, shown in Figure 3, ready to start another retracting stroke of the piston 5i) (and the push-out), thus completing a cycle in the operation of the machine. As will ne apparent from the foregoing description, the pis ton 49 executes a rapid retracting stroke and then a rapid working stroke for a portion of its travel throughout the distance required to slide an unfilled mold up to closely adjacent a previously filled mold located below the die 4 of the charging chamber, and then for the balance of its travel to advance the unfilled mold-and all the lled molds preceding it--relativeiy slowly and. uniformly toward the discharge end of the machine. At the same time the previouslyfilled mold is replaced by the unfilled mold below the die 4l. During the retraction of the pushout, the platen 5 descends to force mud out of the charging chamber 3 into the mold positioned below the die. The operation of the machine is continuous although the mold filling and mold advancing steps are intermittent.

The dumper control valve '74 is operated by the twostep cam 86 fixed on the same shaft 81 with the cam 85, the shaft 81 being so arranged as to make one revolution for each revolution of the crankshaft 40. Pressure from primary pressure line 57 is delivered to secondary pressure line 73 which includes the iiow-control valve 79 through which the supply of liquid delivered to the piston 72--and hence the speed of this piston--is determined.

The Valve stern 76 riding against the contour of cam 86 under the urge of spring 77 positions the dumper control valve so as to admit pressure liquid from line '7S into the right-hand end of cylinder 69 through pipe 7d and opening the left-hand end of this cylinder through pipe 71 to return line Sd. This imparts travel in a lefthand direction to the piston 72 and, hence, to the extension 74 and rack 21 associated therewith. Thereafter, when the cam 83 has made a half revolution, the dumper control valve is shifted to its second position in which pressure liquid is introduced from line 78 via pipe 71 into the left-hand end of this cylinder to return line 80, causing the piston 72 and the rack to move in the opposite direction. l

Since the rack 21 engages pinion 22 on shaft 17a this imparts back-and-forth motion to the swingable members 16 and 17' of the mold dumping mechanism so that the molds are delivered onto pallets` P and the empty molds returned to the machine.

Because the swingable member l5 must be in a positionto receive the leading mold of the train as it is nudged off; the end of the machine by the action of the push-out in presenting a new mold below the charging chamber 3, it is important that the cams 85 and 6 be properly adjusted so as to synchronize the operations ofthe mold` ward movement of the push-out for about 72 degrees and 144 degrees, respectively, of are on the cam.

Since the piston "f2 delivers a simple back-and-forth motion to rack 2 for operating the mold dumping mechanism 15, the contour of two-step cam do is designed to hold the control Valve 75 against the thrust of the spring 77 during one-half a revolution and to allow the spring 77 to restore the valve 75 to its original position during the other half revolution.

The contour of the stepped cams 85 and 36 may be selected so as to effect a gradual transition from one step to another, thus reducing the noise and vibration caused by thesurging of liquid in one direction and another. Also the time allotted to Athe several portions of the backand-forth strokes of the push-out may be suitably selected to give the best performances; and the operation of the push-out and dumping mechanisms, although separately adjustable in operation, are jointly coordinated with the operation of the machine by coupling the cam shaft Si to amechanically-driven part of the machine.

To prevent damage such as might occur if a mold becomesjammed in the machine, the pump 53 preferably is provided with a relief-valve-controlled` by-pass (not Shown) which upon overloading of the system opens to discharge liquid from the pump directly back to the tank 67.

While a preferred specific embodiment of the hydraulically-poweredautomatic brick machine of the invention has'been set forth, it is to be understood that the invention is not limited to the exact constructions illustrated and: described but modifications of these detailsmay bc made within the scope of the following claims.

l" claim:A

l. In an automatic brick machine of the type comprising a pug mili adapted'to contain a supply of plasticized brick-'forming material and having a charging chamber communicating therewith and a reciprocating platen for forcing materialfrom the chamber into a mold supported upon a trackway below the chamber, the combination with'a push-out member mounted for travel in a plane below the chamber for advancing the mold along the trackway, of a hydraulic system for reciprocating said push-out member,v said' system comprising a cylinder, a piston reciprocable within the cylinder and having'a piston rod' operatively connected to the push-outv member, a source offluid pressure, a control valve for controlling the admission and discharge of pressure fluid to and from said cylinder, and a rotary cam so constructed and arranged as to shift the control vaive to different positions during rotation of the cam, to admit pressure to the cylinder for imparting to the piston a fast retracting stroke and an initially fast and subsequently slower working stroke. y

2. In an automatic brick machine of the type comprisbrick-formingv materialand having a charging chamber Lis communicating therewith and a reciprocating platen for forcing material from the chamber into a mold supported upon' a trackway below the chamber, the combination with a push-out member mounted for travel in a plane below the chamber for advancing' the mold along the trackway, of a hydraulic system for reciprocating the push-out member, said system comprising a cylinder, la piston reciprocable within the cylinder and having a piston rod extending outwardly through an end of the cylinder from the forward face of the piston and operatively connected to the push-out member, a source of Iluid pressure, a housing enclosing a push-out control valve communicating with the cylinder upon opposite sides of the piston, a fluid pressure line extending between the pressure source and the control valve housing and a return line extending from the control valve housing to exhaust, a rotatably mounted cam for operating said control valve, and a drive shaft adapted to be connected to a source of power and operatively connected to the platen and to the cam for actuating the control valve and cam in synchronism, said cam being constructed to shift the control valve to different positions during a single rotation, first, to admit pressure to the cylinder for acting against the forward face of the piston and opening the other end of the cylinder to the return line for retracting the piston, second, to placev opposite ends of the cylinder in communication and for admitting pressure thereto for initiating the beginning of the working stroke, and, third, to admit pressure to the cylinder for acting against the rearward face of the piston and opening the other end of the cylinder to the return line for completing the working stroke of the piston.

3. An automatic brick machine asset forth in claim 2 including a resistance valve in the pressure line inter-V mediate the control valve and the source of uid pressure.

4. .in an automatic brick machine of the type comprising a pug mill adapted to contain a suppiy of plasticized brick-forming material and having a charging chamber communicating therewith,'a reciprocating platen for forcing material from the chamber into a mold supported on a trackway below the chamber and a drive shaft adapted to impart reciprocating motion to the platen, the combination with a push-out member slidablyy mounted for travel in a plane, below the chamber for advancing the mold along the trackway into filling position beneath the chamber, a mold dumping mechanism located adjacent an end of the trackway for emptying bricks from the mold, an extension for actuating the mold-dumping mechanism and a hydraulic system for reciprocating said push-out member and said extension, said system comprising a push-out cylinder and a piston reciprocable therein having a piston rod extending outwardly through one end only of the push-out cylinder from the forward face of the piston and operatively connected to the pushout member, a source of fluid pressure, a housing enclosing a three-position push-out control valve communicating with the push-out cylinder upon opposite sides of the piston, a primary pressure line extending between the pressure source and the push-out valve housing and a return line extending from the push-out valve housing to exhaust, a mold-dumping cylinder and a piston recip-V rocably mounted' therein operatively connected to said extension and having opposite faces of equal effective pressure area, a housing enclosing a mold-dumping control valve communicating with the mold-dumping cylinder upon opposite sides of its piston, a secondary pressurey line extending between the primary pressure line and the mold-dumping control valve housing and a secondary return line extending from the mold-dumping control valve housing to exhaust, a rotary cam shaft operatively connected with the drive shaft and' cams upon the cam shaft for actuating the control valvesin synchronism for imparting to the piston of the push-out cylinderY a fast retracting stroke and an initially fast and subsequently slower working stroke' and for imparting to the piston of the mold-dumping cylinder a back and forth motion, the cam for operating the push-out control valve being con structed to shift the control valve to diierent positions during a single rotation, rst, to admit pressure to the cylinder for acting against the forward face of the piston and opening the other end of the cylinder to exhaust for retracting the piston, second, to place opposite ends of the cylinder in communication and for admitting pressure fluid thereto for initiating the beginning of the working stroke, and, third, to admit pressure fluid to the cylinder for acting against the rearward face of the piston and opening the other end of the cylinder to exhaust for completing the working stroke of the piston.

5. An automatic brick machine as set forth in claim 4 including a constant-110W valve in the secondary pressure line between the primary pressure line and the second control valve.

6. An automatic brick machine as set forth in claim 4 in which the source of fluid pressure comprises a pump operated from the drive shaft.

References Cited in the file of this patent UNITED STATES PATENTS 1,341,798 Graham June l, 1920 1,350,604r Graham Aug. 24, 1920 1,452,152 Graham Apr. 17, 1923 1,454,165 Graham May 8, 1923 1,779,136 Martin Oct. 21, 1930 1,799,113 Miedbrodt Mar. 31, 1931 1,824,493 Oeffner et al Sept. 22, 1931 2,228,700 Hamner et al. Jan. 14, 1941 2,542,584 Sherman et al Feb. 20, 1951 2,586,210 Corwin Feb. 19, 1952

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