Apparatus For Producing Concrete Blocks With Undercut Portions

Abstract

Apparatus for forming a concrete block having the usual block with two cavities connected to a small facing block or slab by web portions spaced from the top and bottom of the block and slab, comprises the usual mold box with cores for the block cavities and spaces between the block and slab. Core portions are provided on the stripper head for filling the spaces between the top of the webs and the top of the block. Core portions are provided for filling the spaces between the bottoms of the webs and the bottom of the block, the core portions being slideable from withdrawn position in cavity core recesses to extended position underlying the web spaces. Motor means are provided on the outer side of the mold box sides for extending and retracting the slideable core portions.

Description

BACKGROUND OF THE INVENTION

This invention relates to apparatus for producing concrete blocks having a portion at the bottom which is undercut. It particularly relates to an attachment for a conventional modern high speed concrete block making machine which makes it possible to produce, in such a machine, blocks having undercut portions during the normal operating cycle of the machine.

Certain building blocks have long been known which have a conventional block portion for forming an inner wall integrally connected by web portions to another block portion which provides an outer wall or facing, such as shown in U.S. Pat. No. 943,518 to Butz, dated Dec. 14, 1909. Considerations of insulation against cold and dampness make it desirable that the heighth of the web portions connecting the inner wall portion and the outer face portion be less than the overall height of the block. This was easily done with the slower handmade methods used in the past.

In the modern high speed machines a four sided mold box, open at top and bottom, is used, with cores to fill the voids in the block, the cores being suspended from bridging members supported on the box. A flat steel platen is used to close the bottom of the mold box, the platen being hydraulically supported under the box.

After the concrete mix is delivered to the mold box in premeasured amount, provision is made for vibrating the box on the platen and a stripper head above the box is lowered to first compress and compact the mix in the box and then, as the platen is lowered, the head is further lowered to force the molded blocks out from the cored box onto the platen. The platen is then removed and the process starts again with the introduction of another platen.

It will be apparent that if a block with any undercut portion is desired, one of the cores provided to fill the voids in the block would have to have a transverse projection near the bottom of the block to provide the undercut or the platen would have to have a core secured to it to provide the undercut. Providing a core secured to the platen would be very costly because of the number of platens required for a single machine and would be impractical because the core would interfere with the means now used for stripping the blocks from the platen by sliding the blocks therefrom.

The object of the present invention, therefore, is to provide motor means on the mold box for withdrawing an undercutting core after the block is molded and prior to the time the platen is lowered and the block is forced out of the mold box. Similar motor means in the past have been provided at the mold box ends for embossing one or more faces of the block but no movable core portions have heretofore been known.

SUMMARY OF THE INVENTION

The present invention proposes to provide an undercutting core member which is withdrawn from its undercutting position prior to lowering the platen and stored, during removal of the block from the mold box, outside of the mold box or within one of the box-supported cores.

Motor means secured to the side of the mold box are provided for withdrawing the undercutting core while the molded block is being forced out of the box onto the platen. Since hydraulic power is available at each modern machine the preferred motor means is a cylinder and piston. If the undercutting core extends completely across the mold box it obviously must be withdrawn completely from the box but, in many instances such as for the block hereinafter described, the undercutting core may be withdrawn to a position within one of the box-supported cores. Obviously, a double acting piston motor could be used but, in the interest of space conservation, a single acting piston is used to advance the core to its undercutting position and a return spring is used to withdraw the undercutting core during the expulsion of the block onto the platen. The piston rod of the motor is secured to one end of a lever of the first class, whose fulcrum is supported on the box side, and the other end of the lever is secured to a push rod secured to the undercutting core. A compression coil spring around the push rod biases the latter lever end away from the mold box side for withdrawing the undercut core when the motor is deenergized.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view of a mold box, simplified for clarity, showing apparatus of the present invention attached thereto;

FIG. 2 is a plan view of a concrete block molded in the apparatus of FIG. 1;

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

FIG. 4 is a diagrammatical sectional view on the line 4--4 of FIG. 1, a portion of a stripper head being shown in section and a bridging member being indicated in broken lines;

FIGS. 5, 6 and 7 are views similar to FIG. 4 showing mold box and head in successive stages of operation;

FIG. 8 is a sectional view of the operating mechanism of the apparatus on the line 8--8 of FIG. 9;

FIG. 9 is a side elevational view of the operating mechanism as viewed from the right in FIG. 1; and

FIG. 10 is a view of a modified form of block produced by the apparatus of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, a mold box 10 for molding blocks 11, as shown in FIGS. 2 and 3, has sides 12 and 13 and ends 14 and 15, the box 10 being provided with a partition 16 so that two blocks 11 can be molded in each cycle of the machine. It will be understood that FIG. 1 is simplified in that metal wear plates, not shown, bolted to the sides, ends and partition extend therealong on the interior of box 10.

Block 11 has a conventional block portion 11a to which is secured a smaller block or facing slab portion 11b by web portions 17. It will be understood that block 11 can be used for economically constructing a wall having its inner face provided by the portions 11a and its outer face by portions 11b, the wall being constructed in one operation and eliminating any separate facing operation.

Block 11 has voids 18 and 19 in portion 11a and voids 20, 21 and 22 between portions 11a and 11b, the latter voids being spaced for the web portions 17. Mold 10 is provided with cores 18' and 19', to occupy voids 18 and 19 during molding, and with cores 20', 21' and 22' to occupy voids 20, 21 and 22, it being understood that one block 11 is cast on one side of partition 16 and another block on the other side of the partition, the blocks being oppositely disposed in box 10.

Referring to FIG. 4, the position of a bridging member 23 is indicated in broken lines. Member 23 is secured to the sides 12 and 13 by means, not shown, and the cores 20', 21' and 22' are secured to the member 23 as by welding. A similar bridging member is provided for supporting cores 18' and 19' in each end of the box 10.

Referring again to FIGS. 2 and 3 it will be seen that it is important that the heighth of the webs 17 be less than the overall heighth of block 11 so that proper ventilation transversely may be provided in a wall built with blocks 11 as well as with ventilation vertically. Each tier or row of blocks must be offset transversely of the wall from the row beneath so that the rows are interlocked. Whether this offset is one half a block length or one third a block length, it will be apparent that for proper transverse ventilation a gap at the bottom of the web portions 17 must be provided as well as a gap at the top of each web portion 17.

Referring to FIG. 4, a stripping head 25 is provided which, when lowered, first compacts and compresses the mix in the mold box 10 prior to expelling the blocks downward. Shoes 26, downwardly projecting core-like members, on the head 25 are provided for compacting and compressing the mix between cores 20', 21' and 22' for forming the gaps above webs 17 in the molding of the block.

Means for forming the gaps or voids below the webs 17 are provided in each half of box 10 and on both sides of the box in the form of undercutting core portions 27 movable into and out of a cavity 28 at the bottom of cores 20' and 22'. Each core 27 is connected by a rod 29 to a slotted connection with one end of a beam or lever of the first class 30, having a fulcrum at 31 on a support 32 projecting, respectively, from the box sides 12 and 13. The other end of each beam 30 has a slotted connection at its other end with the end of a piston rod 33 extending from a cylinder 34 secured to the box side 12 or 13. Rod 29 is provided with a compression coil spring 35 between the side of the box and the end of beam 30 for returning the undercut core 27 to its withdrawn position when cylinder 34 is deenergized.

It will be understood that the mold box 10 is supported in the molding machine independently of the platen 36 (FIG. 4) and head 25, means 37 for connecting the box to its support being shown in FIG. 1. It will also be understood that head 25 may be lowered with respect to box 10, the head being slotted transversely for the bridging members 23 so that the head may be lowered into the box to force the molded block out of the box. Means for vibrating the box and head are also provided.

Referring now to FIGS. 8 and 9, a cylinder 34 and fulcrum support post 32 are shown secured to a plate 40 which is bolted to the side, here side 13, of the mold box at 41--41. The beam or lever 30 comprises a pair of bars extending on either side of piston rod 33, post 32 and rod 29 and secured thereto by the respective pins 42, 43, and 44.

The rod 29 is threadedly secured to the undercutting core 27 and two guide rods 45, secured in the core 20' and extending into suitable holes in core 27, are provided to guide and orient the core 27 as it slides out of and into the recess 28.

Referring again to FIGS. 4-7, inclusive, the cycle of operation of the apparatus starts with the raising of the platen 36, by means not shown, into position under the mold box 10. Cylinder 34 is then energized forcing the undercutting core 27 out of recess 28 with its end against core 21' as indicated in FIG. 4.

The head 25 is elevated out of the path of a charging frame, not shown, which slides in from the side over the box 10. The charging frame, containing a premeasured amount of concrete mix, releases its charge into the mold box 10 and is again withdrawn. The mold box is then vibrated to compact the charge and the head 25 is lowered to further compress and compact the concrete, the shoes forming the voids above the webs 17 and the undercutting cores 27 forming the voids under the webs 17, as shown in FIG. 5.

Cylinder 34 is then deenergized as the vibrating mechanism is stopped, as shown in FIG. 6, spring 35 withdrawing the cores 27 into recesses 28.

Platen 36 is then lowered and head 25 is lowered to force the molded blocks 11 out of the mold box 10, as shown in FIG. 7, the end 46 of the transverse slot for bridging member 23 being shown in this Figure. The platen 36 is then removed and stored to allow the blocks to cure and a new platen 36 is moved into place under box 10 to start another cycle.

It will be apparent that the undercutting cores 27 may vary in size. In FIG. 10, a block 11' is shown having a larger undercut 27' under the shorter web 17' made by a larger undercutting core. It will be noted that the void indicated at 18' in block 11' is tapered inward toward the bottom, the degree of taper being exaggeratedly shown, since the block is expelled downward from the cores.

Claims

I claim:

1. A mold box for forming concrete blocks having undercut portions comprising side members forming a four sided frame open at top and bottom, void-forming core members supported by the side members within the frame, at least one void-forming core member having a recess therein, at least one undercutting core member movable in the box, and motor means secured to the frame side for moving the undercutting core member into undercutting position and for withdrawing the undercutting core member into the core recess.