US2315634A - Expansible core mold - Google Patents

Description

April 6, 1943. c McCALL EXPANSIBLE CORE MOLD Filed June 23. 1941 2 Sheets-Sheet l Flehl.

giwvo'n t o'o Harold C. M Call April 6, 1943. MCCALL 2,315,634

EXPANSIBLE CORE MOLD Filed June 23, 1941 2 Sheets-Sheet 2 2 16 .F'I G .4.

I III/III/ Harold C.M Call aftouwn Patented Apr. 6, 1943 UNITED STATES PATENT OFFICE EXPANSIBLE CORE MOLD Harold C. McCall, Columbus, Ohio Application June 23, 1941, Serial No. 399,250

6 Claims.

This invention relates to the casting of cellular cementitious bodies, such as concrete floor slabs and other cementitious building units.

In transverse cross section, for certain uses, a typical floor slab is preferably eight inches in thickness and three feet wide, the slabs bein formed in varying lengths, although many other transverse dimensions are used. To minimize the amount of material utilized in such a slab, and at the same time to retain required structural strength, it is customary to form such slabs with a plurality of parallel longitudinally extending cells or core spaces which extend the full length of the slab. Considerable difficulty has been encountered in providing removable and collapsible core forms for producing the cells or cored spaces of optimum size and shape. Such cores are mounted in the mold in their required positions of relative spacing so that when the mold is poured with the plastic cementitious mixture, the latter will flow around the cores into the internal spaces of the mold in order to produce the cells. After the cementitious mixture at least partially hardens, it has been proposed to collapse the cores to permit the same to be withdrawn by longitudinal endwise movement from the cementitious slabs or blocks.

The present invention provides an improved collapsible core form for carrying out this operation, wherein the core is constructed to include a smooth-surfaced outer sheath of a flexible resilient material, such as rubber, mechanical means being provided within the sheath -for stretching or expanding the same to cause it to assume its operative position and, likewise, for

collapsing the core when it is desired to withdraw th same from a mold poured with cementitious material.

In prior art devices, the cores used for this purpose have beencomposed of sheathings or envelopes of heavy fabric, which inherently are non-elastic and possess relatively coarse or uneven surfaces which adhere to the partially set cement and are difficult to remove, possessing but a short period of utility. Also, it has been proposed to use inflatable tubes to attain similar ends, but these introduce difficult problems as to shape and in use in the shop. It is therefore an object of the present invention to provide a collapsible core composed of an elastic smooth-surfaced sheathing which will not adhere to the cement or concrete when the core is to be collapsed and withdrawn from a cast body of such cementitious material.

It is another object of the invention to provide a collapsible core of the character set forth which will produce in a concrete body a cell or core space substantially square or rectangular in cross-section, as distinguished from a cell substantially circular in cross-section as produced by an inflatable type of core.

A further object of the invention resides in a collapsible core of strong, simple and efiicient design which may b used for extended periods of time without wear or deterioration.

For a further understanding of the invention, reference is to be had to the following description and the accompanying drawings, wherein:

Fig. 1 is a perspective View of a concrete floor slab formed by the mold and core means comprising the present invention;

Fig. 2 is a fragmentary vertical transverse sectional view taken through the mold in which the slab is formed, and disclosing the xpansible core members in their operative positions within the mold to produce parallel cells in a cementitious body, one of the cores being disclosed in its expanded position and another in its collapsed position adapted for withdrawal from the mold.

Fig. 3 is a detail horizontal sectional view taken on the plane indicated by the line III-III of Fig. 2 and showing means for applying initial tension to certain of the reenforcing rods embedded in the floor slabs;

Fig. 4 is a vertical, longitudinal, sectional view taken through the mold shown in Fig. 2, the plane of this section being indicated by the line IV-IV of Fig. 2;

Fig. 5 is a vertical transverse sectional View taken through a portion of a floor slab having a modified form of collapsible core positioned therein, the core being shown in an expanded condition; Fig. 6 is a similar view showing the core in a collapsed condition;

Fig. '7 is a detail longitudinal sectional view taken through the modified form of core when in a collapsed condition;

Fig. 8 is a detail vertical transverse sectional view taken through the joint produced between a pair of floor slabs. e

The mold l disclosed in the drawings is particularly adapted for the formation of a concrete floor slab of the type shown at 2 in Fig. 1, although as the structural features of the invention are more thoroughly understood, it will be obvious that the mold is adapted for the production of other cast cementitious products.

The mold proper comprises a pair of transversely spaced, parallel, longitudinally extending V channel members 3, which are united at spaced intervals by transversely extending cross beams 4. Bolted as at 5 to the upper flanges of the beams 4 is a flooring, the same being composed, in this instance, of wood filler strips '1, and a lagging 8. The upper surfaces of the lagging 8 are covered by a form liner 9.

The vertical sides of the mold are produced by the provision of metallic side cleats I U, the latter having their lower portions secured to the outer surfaces of the channel members 3. Resting on the upper flanges of the channel members 3 and bolted as at H to the cleats it) is a plurality of superposed, parallel wood strips l2. Certain of these strips have their inner surfaces formed with ribs and grooves I3 and M respectively, which produce corresponding ribs and grooves [5 in the sides of the slab 2, as shown in Fig. 1.

By reference to Fig. 2, it will be noted that the inner surfaces of the ribs l3 are slightly offset inwardly with respect to the side surface of the lowermost strip, the latter being slightly inclined with respect to the vertical in order to impart a corresponding angularityto the sides of the slab 2. Thus, when a pair of such slabs are placed in horizontal side by side order, their lower longitudinal edges will be in meeting engagement, but a groove will be produced between the upper portions for the reception of a bonding material, ordinarily cement grout. This material will also enter the grooves M to more securely hold the slabs in adjoining relationship.

Placed in the mold adjacent to the ends thereof are bulkheads it which form the ends of the slab 2. These bulkheads may be positioned at any desired location lengthwise of the mold, in order to control the lengths of said slabs. These bulkheads are formed with openings for the reception of cores I? to be hereinafter more fully described, which cores are used in producing the longitudinally extending, parallel cells IS in the floor slab 2 Additional openings are provided in the bulkhead for registration with the ends of steel rods it, which are used to reenforce the slab 2 and become a part of said slabs when the latter are fully molded.

Detachably supported on the ends of the channel members 3 are transversely extending end gates 2! These gates may be retained in place by the provision of removable pins 2i, the shank portions of the latter passing through aligned openings provided in the flanges of the member 3 and the gates 2i). These pins may be readily removed from their operative positions so that the gates may be demounted when a newly formed floor slab has suflicicntly set to permit of its removal from the mold. Spacing blocks 22 are interposed between the end channels 213 and the bulkheads Hi to hold the latter in position when the mold is being poured.

The cores ll each comprise an outer sheath or envelope 23 of a flexible elastic material such as rubber and to expand the same to assume a substantially rectangular form, use is made of a plurality of internally situated, relatively separable core strips 24, the latter extending longitudinally of the sheath. The strips 24 are maintained in their proper relative positions by providing each thereof with a fixed rod section 25, the latter projecting beyond one of the side Walls of the strip carrying the same in order that the outwardly projecting portion of each rod section will be received within a metallic sleeve 26 embedded in a coinplemental strip. Also each of the strips 24 is formed with a beveled or angularly disposed side wall 27, which walls 21 are adapted for engagement with the round edges of a length of squar metallic tubing 23. This tubing is of sufficient length so that an end thereof will project through an opening 29 provided in an end channel 20.

As shown in Fig. 2, when the tubing 28 is partially rotated, the corner edges thereof will engage with the beveled side walls 27 of the nested core strips 24, causing said strips to separate relatively and thereby stretching the sheath 23 so that the same will assume the position disclosed on the left side of Fig. 2. When the cores are in this expanded form, the mold is poured with the cementitious material, thereby producing the cells E8 in the slabs. Vhen the material constituting the slabs has sufilciently set to permit the slabs to be Withdrawn from the mold, the tubing 28 of said cores is rotated so that the side walls of said tubing will flushly engage with the angular beveled walls 2'! of the strips 2 as shown in approximately the center of Fig. 2.

Due to the elasticity of the material from which the sheath 23 is formed, and the rotation of the tubing 28, above set forth, the strips will be caused to move together, permitting the sheath to contract and move out of engagement with the surfaces of the cells l8, enabling the cores to be readily withdrawn from the formed slab. When the cores are expanded, the tubing 23 is held against rotation by the provision of removable locking pins 36 carried by one of the end channels 2s. The pins 39 have their shank portions passed through registering openings formed in the channel 23 and the tubing 2'3. The tubing may be rotated conveniently by the application of a wrench or other tool to the end of the tubing projecting beyond the channel 23. A particular feature of this construction resides in the fact that the rubber sheath possesses a smooth surface which does not adhere to the concrete forming the slab 2. Moreover, the sheath is elastic so that it applies its own forces in moving to a collapsed position.

It will be noted that the heads or strips 29. have extended surface contact with the elastic tube or sheath E3, the shape of the outer surfaces of said strips or heads determining the cross sectional configuration of the core when in its expanded condition. When so expanded, the strips or heads positively hold the core in its desired shape with the exception of the small gaps formed between the adjacent walls of the strips or heads. tube or sheath is transversely unbroken so that it exerts an elastic band action on the means employed for expanding and contracting the same. The cores have low initial and maintenance costs and may be used repeatedly without deterioration. It has been found that when the cementitious mix is poured into the mold with the mix at a temperature of approximately 90 degrees F., and such temperatures maintained during the setting or hardening operation, it is practical to remove the cores from the cast slab or block after a period of about three hours duration.

It will be understood that the cores may possess cross sectional configurations other than the substantially square configuration disclosed in Fig. 2. For instance, in Fig. 5, the core shown at 5! possesses a substantially oval form. In this figure, the rubber tube or sheath of the core is indicated at 32. To control the expansion or contraction of the sheath 32, I employ the longitudinally extending head strips 33, the outer surfaces of these strips having extended contact The with the inner surfaces of the sheath or tube 32 so as to maintain the latter in a required form when expanded.

To control such expansion and contraction, the strips 33 are provided with inwardly projecting pins 34, the ends of which project through radial openings provided in a metallic tube 35. Within this tube, there is slidably mounted a rod 36, having fixed thereon conical wedges 31. By sliding the rod 36, the wedges 3'! are brought into contact With the inner ends of the pins 34, causing expansion or contraction of the strips 33 and the rubber sheet 32.

In View of the foregoing, it will be seen that the present invention provides molding apparatus for producing cast cellular cementitious blocks, slabs or the like in a simple, efficient and expeditious manner. It is preferable to place the reenforcing rods I9 under tension at the time they are inserted in the mold and the latter is poured. When so tensioned, the cementitious block or slab is apparently relieved of strains which tend to produce transverse surface checking or cracking of the bottom face of the cementitious body in the region of said rods when the slabs or blocks are placed in use. Such tensioning may be accomplished by providing the ends of the rods with metallic rings or loops 38, which are welded or otherwise attached to the rod ends. Bolts 39 having hook-shaped ends 49 are engaged with the rings 38 and pass through the registering openings provided in the bulkhead l6 and the end gates 26, the outer threaded ends of said bolts being equipped with nuts 4| which tighten against springs 42 of calibrated or known resistance. When the nuts are tightened to compress the springs 42 to a readily ascertained degree, the rods at the under side of the block 16 will be placed under equal or uniform tension. With the collapsible cores then positioned within the mold, the lat er may be poured with the cementitious mix. During this pouring operation, the mold may be vibrated in the usual manner to insure uniform distribution of the mix in the mold spaces.

Having thus described my invention in certain of its specific aspects and embodiments, I am aware that numerous and extensive departures may be made from the structures and arrangements herein illustrated and described. I therefore reserve the right to employ all such modifications that fall within the scope of the following claims.

What is claimed is:

1. An expansible core structure for producing openings in molded cementitious bodies, comprising an elastic flexible casing, means for expanding said casing, said means having a plurality of rigid longitudinally extending relatively movable sections, means engaging adjacent sec tions to control the direction of movement thereof, and an adjustable operating member extending longitudinally of said core, adjustment of said member serving to move adjacent sections relative to one another to uniformly expand said casing on all sides thereof.

2. An expansible core structure for producing openings in molded cementitious bodies, comprising a tubular elastic flexible casing, internally disposed means for expanding said casing, said means having four separable substantially duplicative rigid longitudinally extending sections, guide means extending between adjacent sec tions, and adjustable operating means extending longitudinally of said core, adjustment of said means serving to move adjacent sections radially with respect to the longitudinal axis of said core and in planes disposed at right angles to each other.

3. An expansibl core structure for producing openings in molded cementitious bodies, comprising an elastic flexible casing, means for expanding said casing, said means having a plurality of rigid longitudinally extending relatively movable sections, means engaging certain adjacent sections to control the direction of movement thereof, and adjustable operating means for moving said sections relative to one another to expand said casing on sets of opposed sides arranged in right angular relationship.

4. An expansible core structure for producing openings in molded cementitious bodies, comprising an elastic flexible casing, means for expanding said casing, said means having a plurality of rigid longitudinally extending relatively movable sections, pivot means hingedly connecting certain adjacent sections, and means Within said core for varying the distance between said pivot means and moving the sections about the axes thereof to change the size of said core 5. An expansible core structure for producing openings in molded cementitious bodies, comprising an elastic flexible casing, means for expanding said casing, said means having a plurality of rigid longitudinally extending relatively movable sections, pivot means hingedly connecting certain adjacent sections, wedge members disposed axially of said core for movement longitudinally thereof, and means projecting from said sections into engagement with said wedge members, adjustment of said wedge members serving to swing said sections about the axes of said pivots and varying the distance therebetween.

6. An expansible core structure for producing openings in molded cementitious bodies, comprising four separable rigid longitudinally extending members disposed in relatively contacting order when said core is collapsed, means carried by certain of said sections for controlling the direction of movement thereof, means for moving said sections to cause a separation of adjacent sections, and flexible means disposed on the outer sides of said sections to prevent the entrance of cementitious materials into the spaces between said sections when said core is expanded.

HAROLD C. McCALL.

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