US2965948A - Apparatus for producing pre-cast concrete members - Google Patents

Description

1960 A. c. RECKMAN ET AL 2,965,948

APPARATUS FOR PRODUCING PRE-CAST CONCRETE MEMBERS Filed Aug. 30, 1955 6 Sheets-Sheet 1 INVENTORS ALBERT C. REOKMAN RICHARD E. FRANCIS BY HERMAN F. BARKLAGE Dec. 27, 1960 A. c. RECKMAN. ET AL 2,955,948

APPARATUS FOR PRODUCING PRE-CAST CONCRETE MEMBERS Filed Aug. 30, 1955 6 Sheets-Sheet 2 O N O D O I cu INVENTORS ALBERT C. RECKMAN RICHARD E. FRANCIS BY HERMAN F. BARKLAGE 1960 A. c. RECKMAN ET AL 2,965,948

APPARATUS FOR PRODUCING PRE-CAST CONCRETE MEMBERS I Filed Aug. 30, 1955 -6 Sheets-Sheet 4 INVENTORS ALBERT G. REGKMAN RICHARD E. FRANCIS BY HERMAN F. BARKLAGE Dec. 27, 1960 A. c. RECKMAN ET AL 2,965,948

APPARATUS FOR PRODUCING PRE-CAST CONCRETE MEMBERS Filed Aug. 30, 1955 6 Sheets-Sheet 5 INVENTORS ALBERT C. RECKMAN RICHARD E. FRANCIS BY HERMAN F. BARKLAGE Dec. 27, 1960 A. c. RECKMAN ET AL APPARATUS FOR PRODUCING PRE-CAST coNgRE-TE; MEMBERS Filed Aug. 30, 1955 6 Sheets-Sheet e YINVENTORS ALBERT o. RECKMAN RICHARD E. FRANCIS BY HERMAN F. BARKLAGE ATT RNE United State APPARATUS FOR PRODUCING PRE-CAST CONCRETE MEMBERS Albert C. Reckman, 201 Bank t., St. Bernard, Ohio; Richard E. Francis, 1773 Reading, Reading, Ohio; and Herman F. Barklage, Zind Lane, Sharonville, Ohio Filed Aug. 30, 1955, Ser. No. 531,569

2 Claims. or. 25-41 This invention is directed to the art of fabricating structural members from a concrete mixture, utilizng a preforming technique in the production of relatively long, slender units such as structural beams or columns. Precast concrete members of this general character, usually reinforced longitudinally, are widely used in residential and commercial buildings as load-bearing beams and columns; and they are also used to a greater extent in shorter lengths in the form of lintels to span door and window openings, and in the form of floor and roof slabs.

The fabrication of pre-cast concrete members of this nature has heretofore presented several difficult problems because the mass of loose concrete must be compacted uniformly in the mold to impart maximum density and strength to the member at all points along its length; and the cast member must be of fairly precise and regular configuration lengthwise and in cross section; and in most cases, a finished surface texture is required.

The invention involves an apparatus relating to the rapid production of pre-cast units of high quality and strength, utilizing power apparatus which is controlled manually. In practicing the invention, the concrete mixture is initially charged into a unique mold box in a damp, loose state and is reduced to a dense pre-formed casting by the application of pressure and vibratory motion.

The mold box is then stripped, leaving the pro-formed casting resting upon a support surface in axially straight condition free from localized curves or irregularities and ready for curing or hardening. The resulting pre-form is fragile; however, it is self-sustaining while resting lengthwise upon the support surface and has a finished surface texture. The pre-form remains on the support surface and hardens into a monolithic pre-cast member ready for use after a setting or curing period.

Precast machines have been proposed in the past, and in general they have embodied separable molds of various types, and ram structures for compressing loose concrete in a mold. In the earlier machines of this type, the loose concrete mixture is compressed in a mold which is then opened and the pre-cast member is bodily removed from the mold and then transferred to a storage area for the setting or curing period. This technique is not satisfactory for the eflicient casting of long, slender members contemplated by this invention because the lineal extent of the fragile pre-forms requires certain essentially different operating principles.

One of the primary objects of the present invention has been to provide an apparatus in which the present member remains upon the same pallet surface during and after the molding operation, thereby to preserve the member in its original, axially straight condition while in a fragile but non-slumping pressed condition for transfer from the machine to the setting or curing area.

Another object of the invention is to provide an improved mold stripping action which utilizes a pressure ram to compress the loose concrete in a mold box, and to utilize the ram in a second function as a stripper to hold the casting upon the pallet while the mold box is stripped from the pre-formed casting without damage,

According to this principle, the ramming-stripping element descends into the mold box to thoroughly compact and compress the loose charge of concrete to certain specific pre-cast shape, after which it remains in engagement with the pre-formed casting which is in fragile condition while the mold box is stripped upwardly from it. Thus the fragile, slender casting is held rigidly for its full length between the parallel surface of the ram and pallet during stripping to preserve the casting in the axially straight condition which was imparted to it in the mold box.

After stripping, the ram is shifted upwardly to a position above the pre-formed casting, allowing the platen or pallet, with the casting still resting upon it, to be transferred to the curing area. Since the casting is not disturbed during transfer, it retains its original molded shape and texture until it hardens and is ready for shipment as a pre-cast structural member.

A further object of the invention is to provide a power apparatus for imparting vibratory motion to the mold box and pallet while applying downward ramming pres sure upon the mass of concrete in the mold, the combined pressure and vibration forcing the concrete mass into intimate contact with the surfaces of the mold box and pallet to create uniform density and to impart a finished surface texture to the casting.

The power vibrator is adjustable in range and may be operated at high intensity as the loose concrete is charged into the mold to speed up the settling or compacting action. After the ram and stripping head is brought down, and while the pre-cast unit is being compacted to size, the vibrator may be adjusted to a lower intensity, acting in combination with the ram, to obtain the desired degree of compactness and uniformity of surface texture.

To impart the vibratory motion to the pallet and mold box without disturbing the other components of the machine, a resiliently mounted structure sustains the pallet in operating position beneath the mold box resisting downward ram pressure without dampening the vibratory motion of the pallet and mold box. When the mold box is seated upon the pallet, the vibratory motion is transmitted by metal-to-metal contact from the pallet to the mold box.

Briefly, the present apparatus consists of a rigid frame dimensioned to support individual pallets, a vertically reciprocable mold box selectively movable between raised, inoperative and lowered, pallet-engaging, opera.- tive positions, and a vertically reciprocable combination ram head and stripper plate selectively movable between raised and lowered positions relative to the pallet and mold box. Individually operable sets of power cylinders are provided for actuating the mold box and combination ram head and stripper plate for selectively shifting them relative to one another during a molding cycle.

The power cylinders are controlled manually during a molding cycle to first lower and seat the mold box on a pallet, then to lower the ram head down upon the loose concrete housed within the mold. During the concrete charging operation, steel reinforcing rods may be placed longitudinally in the mold box to be imbedded in the mass of concrete. Then, after the loose con.- crete has been thoroughly compacted in the mold by the combined action of the ram head and vibrator mechanism, the power cylinders are actuated to lift the mold box upwardly from the product the lower surface of which is supported on a pallet and the upper surface of which is engaged by the lower surface of the ram head which now functions as a stripper plate by holding the cast member against the pallet during the mold box stripping, that is, elevating operation. In this manner, the

Patented Dec. 27, 1960 stress-free axial alignment of the newly cast member will be insured.

After the mold box has thus been completely stripped from the newly cast member, the power cylindersare actuated to shift the ram head upwardly outof contact with the precast member which is now supportedonly by the pallet which may be bodily moved or transferred from the machine to a curing area. The pallet is sufficiently rigid longitudinally and the concreete sufficiently compacted whereby to prevent any bowing or sagging of the newly cast member during transport and curing.

The machine preferably is operated with a suflicient number of reserve pallets to providetherequired curing period without interfering with continuous production of the machine. After hardening, the castings may be suitably removed from the palletand stored for further curing or use, whereas the pallet is returned to the machine for reuse.

The pallets preferably are furnished in a standard size suitable for producing castings in sizes up to the capacity of the machine. For the production of narrower units, longitudinal separators may be placed in the mold box, thus creating two or more parallel castings upon each cycle of operation.

To provide for the molding of concrete members having curved or angular top or bottom profiles, ram heads and pallets having the desired contour are installed in the machine. In the event that concrete members are required having a length less than the total length of the mold box, transverse separators may be easily inserted along its length to delineate a series of end-to-end mold sections of the required length.

Further features and advantages of the invention will be more fully apparent to those skilled in the art from the following detailed description in conjunction with the drawings.

In the drawings:

Fig. l is a front perspective view of a concrete molding machine embodying the teachings of the present invention with the parts shown in a position to receive a charge of concrete at the start of a casting cycle.

Fig. 2 is a view similar to Fig. 1, showing the components of the machine in molding position and after the charging operation has been completed.

Fig. 3 illustrates the molding machine of Fig. I viewed in perspective from the right end thereof.

Fig. 4 is a fragmentary sectional view of the molding machine at the start of the molding cycle corresponding to Fig. l, with the mold box charged with the concrete mixture and with the combination ramming head and stripping plate in fully elevated non-operative position.

Fig. 5 is a fragmentary sectional view similar to Fig. 4 with the parts in the same position but showing the loose charge of concrete in the mold box reduced in mass by operation of the vibrating mechanism. This gep of the cycle follows the charging operation of Fig. 6 is similar to Fig. 5 and shows the following step in which the ramming head has descended upon the mass of partially compacted concrete to further the concrete-compacting operation and to bring the pro-formed casting down to its final size and shape.

Fig. 7 is similar to Fig. 6 and shows the upward stripping motion of the mold box relative to the pre-formed casting which is held in position upon the pallet by the combination ramming head and stripping plate.

Fig. 8 illustrates the next step of the stripping operation, showing the stripping plate in its elevated position. above the mold box for removal of the pallet and the newly cast members from the machine.

Fig. 9 shows the final step of the molding cycle, with the mold box and combination ramming head stripper plate maintained in the fully elevated position of Fig.

Fig. 5.

8, and with the pallet and pre-cast members removed from the machine.

Fig. 10 is a diagrammatic front view of the machine in charging position, illustrating a modified construction for molding structural members having a selected length which is less than the total length of the pallet and mold box.

Structure and operation generally With reference now to Figs. 1, 2 and 3, the numerals 2 denote enerally a base comprising a pair of laterally spaced elongate channel members 22 interconnected by transverse members 24. A pair of laterally spaced, vertically disposed end members 26 secured to and carried by members 24 comprise the vertical frame of the machine, it being noted that the upper ends of. the vertical members 26 are rigidly and permanently interconnected by horizontal beam 28.

As best illustrated in Figs. 5 and 9, load bearing arms 30 project from, are rigidly secured to and carried by the vertical members 26, said arms being spanningly engaged by a pair of front and rear outer angle irons 32 and 34 which are fixedly secured'thereto.

A pallet support comprising a plurality of transverse channel members 35 spanningly engages a pair of front and rear inner angle irons 38 and 40. The adjacent vertical legs of the outer angle irons 32 and34 are perma nently and resiliently secured to the vertical legs of the inner angle irons 38 and 49 by means of resilient members "32 which are interposed between and permanently secured to adjacent legs, as illustrated, whereby the pa]- let support is mounted for movement relative to the base of the machine in such a manner that any vibration imparted to the support is completely and effectively insulated from the frame.

The numeral 44 denotes generally a pallet which may, by way of example, comprise an elongate channel iron having a flat top plate 46 with depending sides 48, see As best illustrated in Figs. 1 and 2, the pallet is adapted to spanningly engage the various transverse channel members 36.

The numeral 50 denotes generally a mold box open at its top and bottom and comprising a rigid, unitary, hori zontal frame including front, rear and opposed end walls 52, 54 and 56, respectively. If desired, an intermediate member 58 may be provided for longitudinally subdividing the space between the front and rear walls, see Figs. 4-9. The mold box is vertically reciprocable between the fully elevated, non-operative positions of Figs. 8 and 9 to the fully lowered, operative position of Figs. 1 through 7, with the lower face thereof in contacting relationship with the upper surface of pallet 44, thereby defining a concrete-receptive chamber open only at its top.

Vertical movement of the mold box may be cffectcd by means of a pair of cylinders 60 having piston rods 62 pivotally connected as at 64 to arms 66 pivoted at 63 to end members 26. The other ends of arms 66 may be pivotally connected at 70 to links 72 pivotally secured at 74 to follower elements 76 which slidably engage and are guided by vertical guides 73 which extend in spaced parallelism with end members 26. The follower elements are secured one each to an opposite end of the mold box assembly which is thereby mounted for vertical movement toward and away from the pallet support assembly.

The numeral 80 denotes generally a vertically reciprocable combination ram head and stripper plate, which in the preferred embodiment of the invention may include a pair of elongate elements 82 the opposite ends of which are rigidly secured to end plates 84 (Fig. 3) which are, in turn, secured to and carried by follower elements 86 which slidably engage vertical guides 78. A plurality of depending elements 90 are secured to and carried by the elongate elements 82, the lower ends of the depending elements carrying rigid pads. 92 having ii 3 smooth lower surfaces. If desired, the pads may be secured to elements 90 by means of bolts 94, whereby to permit interchange of pads, or they may be permanently secured to said elements such as by means of welding, or the like. The pads are dimensioned to make a loose sliding fit with the open upper ends of the mold box as hereinafter more fully explained.

Vertical movement of the combination ram head and stripper plate assembly may be accomplished by means of a pair of cylinders 100 having piston rods 192 pivotally connected at 104 to arms 166 pivotally secured to shaft 108, which is journaled to and spanningly engages vertical members 26. The other end of arms 106 are pivotally connected at 105 by links 189 to follower elements 86, to which they are Pivotally connected at 110.

In the preferred embodiment of the invention a safety latch is provided for precluding the accidental or unintentional lowering of the ram head and stripper plate assembly, said latch comprising a pair of levers 12$? pivotally secured as at 122 from the upper end of the frame. The lower ends of these levers are notched as at 124 to provide a bearing surface engageable under elongate elements 82 when in the fully elevated positions of Figs. 4 and 5. The levers are interconnected by an actuator bar 126 which may be grasped by an operator for effecting disengagement of the latch from the ram head and stripper plate assembly. The lower end of levers 126 are inclined as at 128 to provide a surface which will be antomatically swung out of interfering relationship with the ram-stripper assembly incident to upward movement thereof to fully elevated position. It will, of course, be understood that the latch levers will automatically seek the latching position of Figs. 4 and 5 after the same assembly has been fully raised.

In Fig. 3 the numeral 130 denotes a substantially horizontal apron at the approximate level of the top of the mold box assembly, when in fully lowered position, and upon which the loose concrete is temporarily located incident to charging or filling of the open topped molds as in Fig. 4. Suitable means, not illustrated, may be utilized to deliver freshly mixed, loose concrete to said apron.

Generally speaking, as the concrete mixture is charged into the lowered mold box assembly of Fig. 4, the commercially available vibrator units denoted generally by the numerals 61 are actuated for imparting a high frequency vibration to the pallet support assembly, and those items supported thereon and thereby, to wit, the platen 44, and the contents of the mold box. The vibratory motion of the mold box is imparted to the mass of loose, damp concrete 111, causing it to settle to the partially compact condition shown in Fig. 5. It is to be noted at this point, that in fabricating the concrete members illustrated, the mold box is partially filled with concrete and steel reinforcing rods 113 are then placed in the mold box upon the top of the concrete mixture within it. There after, an additional mass of concrete is charged into the mold above the rods 113, after which a second set of reinforcing rods 115 is placed upon the top of the second charge of concrete. The final charge is then placed in the mold box covering the second set of reinforcing rods.

The placement of the reinforcing rods with respect to the cross section of the pre-cast concrete member depends upon the particular service for which the casting is designed. For example, the two concrete members shown in cross section in Fig. 8 are intended to be used as lintels above the door or window openings of a masonry building. As such, they act as beams sustaining the weight load of the building wall above the opening. Therefore, the set of rods 113 residing in the lower portion of the lintel will resist in tension the downward load which reacts as a tension force in the zone below the neutral axis of the lintel. The rods 115, in the upper portion, react in compression above the neutral axis.

7 Charging V At the start of a molding cycle, a hydrated, loose concrete mixture is charged into the mold box by way of the charging apron 130 (Fig. 3) which extends from a concrete mixer or other source of supply (not shown) located at the rearward side of the machine. The concrete mass may be composed of a standard admixture of coarse aggregates, sand and pulverized Portland cement. The proportion of the ingredients is designed to create the required physical character of the concrete castings. For the purpose of weight reduction, a suitable grade of cinder particles may be used as the coarse aggregates. On the other hand, if weight is of no consequence, gravel particles may be used as coarse aggregates.

According to the principle of operation, the pre-cast member, while in its compact condition after the mold is stripped from it, must be sufficiently rigid or self-sustaining to retain its molded shape during the hydration or setting period. For this reason, the amount of water which is added to the dry concrete mixture is just suflicient to activate the Portland cement but is insufficient to reduce the mass to the fiowable state usually associated with concrete pouring operations. In other words, the concrete mixture is in a loose, non-adhering state and is readily spread by hand to a uniform depth in the mold box.

The batch of raw concrete may be measured by suitable equipment (not shown) to provide the volume required. On the other hand, an experienced operator is able to fill the mold box to the required level using a suitable spreading tool to distribute the mass evenly throughout the length thereof. Since the charge of concrete is in fairly loose condition at this stage, its actual volume is substantially greater than the mold box and compacted, resultant casting; consequently, the loose concrete is initially heaped above the box as shown in Fig. 4.

While the mold box is being charged, the vibrators 61 may be actuated so that their impulses are transmitted through the pallet and mold box to the loose concrete within the mold box. The vibratory motion acts upon the particles of the loose mixture and, combined with the force of gravity, causes the particles to settle downwardly into the mold box as a fairly dense mass, Fig. 5, which is reduced in volume and which is substantially free of voids or cavities. Moreover, the vibratory treatment forces the particles into intimate contact with the reinforcing rods and with the internal mold surfaces to create a fine surface texture.

Ramming After the vibrator units have been activated for a sufiicient period to compact the initial charge of concrete as indicated, the ramming cycle is initiated by an operator first pulling upon actuator bar 126 for releasing the safety latch levers 120 after which cylinder may be energized for thereby moving the combination ramming head and stripper bar assembly to the lowered position of Fig. 6 with pads 92 engaging the upper surface of thep'artially compacted concrete mass in the mold box. The ram head exerts heavy downward pressure upon the concrete mass within the mold box to compress it further, bringing it to the final shape. The pressure imposed by the ram head may be alternately applied and released by manipulating control lever 200, Fig. 1, whereby to reduce the concrete to'a fairly rigid self-sustaining mass.

During the aforesaid pressing or ramming cycle, the vibrator units 61 may be continuously or intermittently actuated to facilitate compacting of the particles in the mold box. The vibratory impulses greatly reduce the frictional resistance of the concrete particles and thereby facilitate their relative movement in response to the down- Ward pressure imposed bythe ram head. Moreover, the combination of pressure and vibratory action is found to create a finer surface texture, probably causing/the finer particles of the mixture to flow into intimate contact with the smooth internal surfaces of the mold.

The vibrators 61 preferably are arranged to transmit impulses along lines at leastpartially perpendicular to the pallet and ram surfaces, such that the impulses act along the line of ram motion. In this way, the impulses, in half the vibrating cycle, act toward the ram surface and create stepwise compressive impulses while the descending ram reacts against the concrete mass as a follow-up member.

As noted earlier, the vibrating units 61 are adjustable as to intensity, and preferably are operated at high intensity during the initial or charging operation to speed up the settling or compacting of the loose concrete charge as it is placed in the mold box. After the ram head is placed in operation, the vibrator units may be adjusted to a lower intensity, since in many cases this is found to create a more efiicient pressing action and a finer surface texture. The combined pressure and vibratory motion acting upon the concrete mass quickly reduces the mass to its maximum density and positively eliminates any voids or cavities which would otherwise exist within it.

Stripping With the newly cast members firmly held against the pallet by pads 92, the operator may actuate cylinders 60 to lift or strip the mold box 50 upwardly from the casting, as in Fig. 7. It will be noted that the inside dimensions of the mold box are slightly greater than ram head for clearance between the two parts as the mold box is shifted upwardly. During this operation, the pads 92 act as a stripper head, effectively resisting the upward force of the mold box as developed by the frictional resistance between the mold box and preformed casting.

After the mold box has been elevated to the position shown in Fig. 7, the operator may then elevate the ramstripping assembly 80 to the fully elevated position of Fig. 8. Thereafter, the pallet 44 with the pre-cast members A and B resting upon it is bodily removed from the machine and placed in a suitable storage area for the setting period. To accelerate setting, the pre-cast members may be subjected to an elevated temperature, for example, exposure to steam.

After the required curing period, the finished or hardened concrete cast members may be removed from the pallet surface for storage or for use as a load bearing member, such as a beam, column, or lintel. The removal of the finished cast member requires no special technique since the casting is resting loosely upon the pallet surface. After removal of the pre-cast structural member, the pallet may be transferred back to the molding machine for reuse. Each molding machine is supplied with a sufficient number of pallets to provide continuous operation at a production rate, according to the capacity of the plant, to allow an adequate curing period without creating a bottleneck for lack of pallets tied up in the curing area.

It will be observed from the foregoing that the present machine creates castings at a rapid production rate, either full length or otherwise, as indicated later, since the operations of charging, pressing, and stripping of the mold box from the concrete member are executed by power under the convenient control of the operator. The operating cycle is identical in the production of any given concrete casting, whether full length or otherwise. It will also be apparent that various castings, within the length capacity of the machine, may be produced without any basic change instructure or principle of operation simply by installing a mold box and ram head corresponding to the desired pattern. By way of example, if it is necessary to produce castings having a width equal to the full width of the mold box shown in Fig. 4, the ram head may be modified to create a pressure area corresponding to the width of themold box.

In the preferred embodiment of the invention, the lower ends of each of cylinders60 and 100 may include a depending lug 202 pivotally secured as at 204 to amounting plate 206 fixedly secured to the main frame of the machine whereby the cylinders are mounted for angular movement to accommodate the arcs through which the outer ends of arms 66 and 106 are moved incident to actuation of said cylinders.

Since arms 66 are operatively interconnected, being secured to and carried by rock shaft 69, and since arms 106 are also operatively interconnected, being secured to and carried by rock shaft 108, the forces applied to the opposite ends of the mold box assembly 50 and to the ram-stripper assembly will be equalized, thereby insuring smooth, synchronous operation at all times even though the pressure media on which the cylinders operate is air.

The present invention is neither directed to nor concerned with the particular means by which pressure media is supplied to the aforesaid cylinders, however, for clarity of detail and understanding the numeral 300 may denote a feed or supply line for pressure media which may be selectively directed to opposite ends of either of the cylinders by means of valves 302 and 304, each of which includes manually operable levers. For purpose of illustration only, it may be assumed that valve 302 controls cylinders 60 and valve 304 cylinders 100.

With particular reference now to Fig. 1, the numeral 311 denotes a suitable electric switch having a control lever 310 by which the operating cycle, magnitude and frequency of vibration of vibrators 61 is determined.

With reference to Figs. 1 and 2, it will be noted that the length of cast member is substantially equal to the overall length of the machine, however in the event that shorter members are desired, the mold box may be divided, intermediate its length, see Fig. 10, by means of adjustable end plates 157 securely though releasably anchored in place by means of clamping members 159. The overall length of the combination ramming head and stripper plate 80 may be reduced to the spacing between the end plates 157, it being understood that the various depending members to which pads 92 are secured are removably associated with the elongate members 82 by means of bolts 83 and nuts 35.

From the foregoing it will be noted that we have thus provided simple yet highly effective means for fabricating elongate members of cast cementitious material on a mass production basis.

What is claimed is:

1. A machine for forming precast concrete structural members, comprising a supporting framework, a relatively long, slender mold box having an open bottom and an open top and a frame slidably mounted on said machine framework for vertical movement relative thereto, a vibratable pallet support resiliently mounted on said machine framework below said mold box, means for moving said mold box between a lowered position with its open bottom in contacting relationship with a pallet on said pallet support and a raised position above and remote from said pallet support, a combination ramming head and stripper plate assembly slidably mounted on said machine framework above said mold box for vertical movement relative thereto and to the machine framework and dimensioned to be received within the mold box, means for moving said assembly between a lowered position Within the mold box and a raised position above the raised position of the mold box, means for independently con trolling the movements of the mold box and the combination ramming head and stripper plate assembly between their respective raised and lowered positions, said assembly including an elongated supporting member extending substantially the full length of the machine frame work and a plurality of pad carrying members depending from said supporting member, safety latching means for maintaining said assembly in raised position against accidental movement to its lowered position comprising a pair of levers pivotally connected adjacent their upper ends to the ends of the machine framework and freely dependent from said pivots, said levers having notched lower ends providing bearing surafces engageable beneath said elongated supporting member adjacent the ends thereof when said assembly is in its raised position, and manually actuatable means for releasing said latching means, the lower ends of said levers having camming surfaces for engagement by said elongated supporting member upon upward movement of the combined ramming head and stripper plate assembly so as to move said levers outwardly away from the positions normally assumed under the influence of gravity and thereby permit upward movement of said assembly to its raised position, said levers returning automatically to latching position under the influence of gravity when said supporting member has been raised above said camming surfaces.

2. A machine as described in claim 1, wherein said latch releasing means comprises an actuator bar interconnecting said levers and adapted to be moved manually by the operator of the machine to disengage said levers 777,086 Emery Dec. 13, 1904 805,914 Horr Nov. 28, 1905 1,086,994 Cathriner Feb. 10, 1914 1,984,363 Dietrichs Dec. 18, 1934 2,036,367 Shinn et al Apr. 7, 1936 2,492,297 Lagarde Dec. 27, 1949 2,555,688 Flam June 5, 1951 2,583,597 Ryner Jan. 29, 1952 2,584,534 Barnhardtson Feb. 5, 1952 2,586,210 Corwin Feb. 19, 1952 2,589,115 Nelson et al Mar. 11, 1952 2,614,308 Burkard et al Oct. 21, 1952 2,685,116 Schutt Aug. 3, 1954 2,697,263 Van Ornum et a1 Dec. 21, 1954

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