US3647308A

US3647308A - Apparatus for forming a cored concrete slab

Info

Publication number: US3647308A
Application number: US771152A
Authority: US
Inventors: Robert L Yost
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-10-28
Filing date: 1968-10-28
Publication date: 1972-03-07
Anticipated expiration: 1989-03-07

Abstract

An apparatus and method for forming cored concrete slab utilizing an elongated fixed mold for forming the opposite sides and bottom surface of the slab. A concrete depositing and core forming assembly moves longitudinally over the mold, the assembly including a plurality of elongated core forming mandrels and a hopper which deposits a first layer of concrete in the mold generally to the top of the mandrels. A length of metal mesh is provided having its free end attached at one end of the mold, the mesh being coiled on a reel mounted on the assembly which lays the mesh over the mandrels and the first layer, applying tension thereto, as the assembly moves toward the other end of the mold. Another hopper is mounted on the assembly which deposits a second layer of concrete over the first layer and mesh.

Description

Yost

ited States Patent APPARATUS FOR FORMING A CORED CONCRETE SLAB Robert L. Yost, Decatur, Ind.

Joseph J. Dues, Dayton, Ohio Oct. 28, 1968 Inventor:

Assignee:

Filed:

Appl. No.:

References Cited UNITED STATES PATENTS 8/1964 Kalns ..25/41.5 A 4/1965 Roth et a1 ..25/41 J 2,663,063 12/1953 Van Loon ..25/4l.5 A

Primary Examiner-.1. Spencer Overholser Assistant ExaminerDeWalden W. Jones Attorney1-Iood, Gust, Irish & Lundy ABSTRACT An apparatus and method for forming cored concrete slab utilizing an elongated fixed mold for forming the opposite sides and bottom surface of the slab. A concrete depositing and core forming assembly moves longitudinally over the mold, the assembly including a plurality of elongated core forming mandrels and a hopper which deposits a first layer of concrete in the mold generally to the top of the mandrels. A length of metal mesh is provided having its free end attached at one end of the mold, the mesh being coiled on a reel mounted on the assembly which lays the mesh over the mandrels and the first layer, applying tension thereto, as the assembly moves toward the other end of the mold. Another hopper is mounted on the assembly which deposits a second layer of concrete over the first layer and mesh.

15 Claims, 8 Drawing Figures PATENTEUMAR I 1912 v 3, 647, 308

sum 1 BF 6 INVENTOFZ Rosem L. Yosr be. Homo, Gus'r, lmsu Lunov AHornevs PATENTEDMAR 7 1972 SHEET 2 BF 6 INVENTQR QOBERT LYosT bu H000 ATfor-neys APPARATUS FOR FORMING A CORED CONCRETE SLAB BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to apparatus and methods of forming reinforced concrete structural elements, and more particularly to an apparatus and method for forming a cored concrete slab from low slump concrete.

2. Description of the Prior Art Prestressed reinforced concrete beams, slabs, panels and other structural elements are extensively employed in the construction industry. Many of such elements are of the cored type, i.e., having cavities or cores therein for reducing the overall weight.

Such cored concrete structural elements are commonly formed by one of two different processes. The first process, employs a concrete mixture having no slump. This mixture is pressure formed into the desired shape. In one form of apparatus utilizing no slump concrete, an elongated stationary mold is employed which forms the sides and bottom surface of the element. An extruding device moves along the mold carrying a top plate which completes the mold cavity, and the relatively dry concrete mixture is forced into the cavity by rotating augers which also respectively form the cores in the product. In another apparatus utilizing no slump concrete an extruding assembly moves over a bed successively depositing three layers of relatively dry concrete mix, each layer being compacted by reciprocating tamping devices. The middle layer surrounds a plurality of reciprocating mandrels which form the cores, and the sides of the slab are formed by a slip form device which advances with the assembly. Both of the abovedescribed types of apparatus for performing the dry process possess certain disadvantages. One such disadvantage is that it has not been possible to incorporate inserts, such as electrical junction boxes, conduits and the like, into slabs formed in this manner.

In the second method of forming prestressed, cored concrete structural elements, concrete having a low slump is poured in the mold, cured and removed therefrom. There is a preference in the industry for using concrete having a low slump rather than concrete having no slump, particularly where it is desired to include various types of inserts in the product. In one comparatively simple form of apparatus employing low slump concrete, a stationary mold is provided which forms the sides and bottom surface of the product. Elongated inflated mandrels are positioned in the mold and the relatively fluid or wet concrete is then poured into the mold covering the mandrels. After curing, the mandrels are deflated and removed leaving the cores in the product. In another type of apparatus employing low slump concrete, referred to as a slip form machine, an assembly is moved over a bed. The slip form machine forms the sides of the product; the bed forms the bottom surface of the slab. This assembly also carries a plurality of elongated mandrels or core tubes which form the cores in the product, the relatively wet concrete being poured over the mandrels into the mold cavity formed by the slip form machine and the stationary bed. The speed of operation of the slip form machine is necessarily limited by the fact that the moving assembly carries a portion of the mold and thus can travel only as fast as the concrete cures so as to be self-supporting.

SUMMARY OF THE INVENTION It is desired to provide an apparatus and method for forming a prestressed, cored concrete slab employing low slump concrete which incorporates all of the advantages of such a process.

In accordance with the broader aspects of the invention, a longitudinally elongated hold is provided for forming the opposite sides and bottom surface of the slab. Means are provided for progressively laying a layer of cementitious material in the mold and including means disposed over the mold for receiving cementitious material in relatively fluid form and depositing the same in the mold, and means are provided for relatively longitudinally moving the depositing means with respect to the mold in the direction of elongation thereof. A plurality of elongated mandrels are provided disposed in the mold in spaced, parallel relationship and extending in the direction of relative movement for forming the longitudinally extending cores in the slab, the mandrels having spaced opposite ends and having portions intermediate their ends disposed under the depositing means. Means are provided for attaching the leading ends of the mandrels which face in the direction of relative movement to the laying means so that the mandrels are relatively moved with the depositing means. In the preferred embodiment, the layer of cementitious material is deposited to a level generally even with the tops of the mandrels and an elongated length of mesh reinforcing material is provided having its free end attached to the mold, the laying means laying the mesh, under tension, over the previously deposited layer, the laying means including means for depositing a second layer of cementitious material in relatively fluid form over the first layer and mesh.

It is accordingly an object of the invention to provide improved apparatus for forming a cored concrete product.

Another object of the invention is to provide an improved apparatus employing concrete having a low slump, in contrast to no slump, for forming a prestressed, cored concrete product.

A further object of the invention is to provide an improved method for forming a cored concrete slab from concrete having a low slump in contrast to no slump.

The above-mentioned and other features and objects of this invention and the manner of attaining them will become more apparent and the invention itself will be best understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein;

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary view in perspective, partly broken away, illustrating the apparatus of the invention;

FIG. 2 is a top view of the apparatus illustrated in FIG. 1;

FIG. 3 is a side view of the apparatus illustrated in FIG. 1, partly broken away;

FIG. 4 is a fragmentary cross-sectional view, partly schematic, taken generally along the line 44 of FIG. 2;

FIG. 5 is a fragmentary cross-sectional view, taken generally along the line 5-5 of FIG. 2;

FIG. 6 is a generally schematic diagram showing the propulsion system of the apparatus;

FIG. 7 is a fragmentary view in perspective, partly in cross section, useful in explaining the method of the invention, and further illustrating certain features of the apparatus; and

FIG. 8 is a fragmentary cross-sectional view taken along the line 8-8 of FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENT The Apparatus Referring now to the drawings, the apparatus of the invention, generally indicated at 10, comprises a mold assembly 12 for forming the parallel opposite sides and bottom surface of slab l4, and an assembly 16 which travels on the mold depositing cementitious material therein, forming the core openings in the slab, and finishing the top surface as its forward movement in the direction shown by the arrow 18 progresses.

Mold 12, only a short section of which is shown, but which may be several hundred feet in length, comprises a bed 20 supported upon a supporting surface 22, such as the ground, by a plurality of longitudinally spaced-apart support elements 24. Bed 20 may have conduits 26 formed therein for circulating a heating medium, such as heated oil, in order to accelerate the curing of the slab in the mold. A pair of

side mold elements

28, 30 are provided on the opposite sides of bed 20 and extend longitudinally the entire length thereof.

Side mold elements

28 and 30 have

rails

32 and 34 formed on their upper extremities for supporting the assembly 16 for longitudinal movement with respect to the mold 12.

Side mold elements

28 and 30 are supported upon the supporting surface 22 by a plurality of spaced-apart, vertically adjustable supports 36, and are adapted to be vertically raised and lowered between upper and lower positions by a plurality of conventional hydraulic jacks 38. In their upper positions, side mold elements 28. and 30 extend upwardly above the upper flat surface 40 of bed 20. The

inner surfaces

42 and 44 of

side mold elements

28 and 30 thus define a mold cavity having an open top. The

elements

28, 30 with upper surface 40 of base form the opposite parallel sides and bottom surface of the slab 14. In the lower positions of

side mold elements

28 and 30, rails 32 and 34 are flush with the upper surface 40 of base 20, or lower, thereby to assist in the removal of the slab 14 from the mold cavity and to permit transverse sawing of the elongated slab 14 in the mold into shorter elements of desired length by a conventional concrete sawing apparatus (not shown).

The assembly 16 comprises a supporting frame 46 supported on the

rails

32 and 34 of the side mold elements 28 and for longitudinal movement thereon by means of a forward pair of

wheels

48 and 50 and a rear pair of

wheels

52 and 54. The forward pair of wheels 48 r and 50 are respectively mounted on an axle 56 and the rear pair of

wheels

52 and 54 are likewise mounted on an axle 58,

axles

56 and 58 being mounted on frame 46, as shown.

The assembly 16 is moved longitudinally over the mold 12 in the direction shown by the arrow 18. The assembly 16 is guided to move on the

rails

32 and 34 by the guides 47. The guides 47 are located at each corner of the frame 46 and engage the facing surfaces 42 and 44 of

elements

28 and 30.

The

wheels

48, 50, 52 and 54 are driven by the propulsion system shown in FIG. 6. A suitable electric motor 60 is mounted on frame 46 and drives a conventional hydraulic pump 62 through a conventional belt drive 64. Pump 62 receives hydraulic fluid from hydraulic tank 66 through supply line 68. Hydraulic pump 62 independently drives the forward pair of

wheels

48 and 50, and the rear pair of

wheels

52 and 54, respectively, through conventional

hydraulic motors

70 and 72. Pump 62 is connected to the forward hydraulic motor 70 by pressure line 74, hydraulic motor 70 having a discharge line 76 which is returned to the tank 66. Pump 62 likewise drives the hydraulic motor 72 through pressure line 78, motor 72 having discharge line 80 which is returned to the tank 66.

The forward hydraulic motor 70 drives a suitable gearbox 82 Y 124 which respectively drive

rear wheels

52, 54 through

drive chains

126 and 128, driving sprockets 130, 132 thereon.

Motor may be energized by suitable flexible cables, or more preferably by a conventional third rail and sliding contact system (not shown). Suitable motor controls 134 are provided for controlling the speed of motor 60 and thus the linear speed at which the assembly 16 moves in the direction 18. Suitable catwalks 136 are supported on frame 46 for the operator and provide access to the motor controls 134.

An elongated hopper 138 is mounted on frame 46 and extends transversely thereacross over the mold 12 for depositing cementitious material in the mold cavity to form a first layer 140 therein as the assembly 16 moves forwardly in the direction 18. Hopper 138 has an open upper end 142 for receiving the cementitious material, and forward and rear sidewalls 144 and146 having converging

lower extremities

148 and 150 which define an elongated, transversely extending discharge opening 152 for depositing the cementitious material in the mold over the top surface 40 of base 20. An elongated force feeding and distributing auger 154 is positioned in hopper 138 adjacent opening 152. Auger 154 is selectively driven in opposite directions by means of a conventional hydraulic motor 156 which drives gearbox 158 which, in turn, drives auger 154 through drive chain 160. Hopper 138 may be continuously filled with cementitious material by means of a conventional ready-mix truck (not shown) which moves along the side of the mold 12 as the assembly 16 moves forwardly in direction 18 or by like means.

A plurality of elongated core-forming mandrels 162 are provided in the mold cavity and extending in spaced, parallel relationship in the direction of movement. Mandrels 162 are in the form of hollow metal tubes closed at their opposite ends 164, 166 and have elongated

rod portions

170 and 171 secured to the mandrels 162 at their opposite ends,

rod portions

170 and 171 respectively project beyond opposite ends 164 and 166. The portions 170 which project forwardly from the forward or leading ends 164 of mandrels 162, which face toward the direction of movement 18, are connected to frame 46 for rotational movement by downwardly extending brackets 172. It will thus be seen that portions of mandrels 162 as adjacent their leading ends 164 extend under the discharge opening 152 of hopper 138, the rear or trailing ends 166 of mandrels 162 extending substantially rearwardly of the rear end 174 of frame 46. In a specific embodiment of the apparatus of the invention, mandrels 162 were each 30 feet long and extended 20 feet beyond rear end 174 of frame 46.

It will thus be seen that the mandrels 162 are mounted for rotational movement about their longitudinal axes which extend between their leading and trailing ends 164, 166,

rod portions

170, 171 being coaxial therewith, and leading ends 164 of mandrels 162 being pulled by brackets 172 as the assembly 16 moves forwardly in direction 18, the trailing ends 166 being unsupported by the-frame 46 and floating in the layer of cementitious material so as to form the core openings therein. In order to keep the mandrels 162 submerged in the cementitious material, of the layer 140 and to keep the mandrels 162 generally parallel to the surface 40, mandrels 162 are wholly or partially filled with liquid 176, preferably a mixture of water and alcohol, so that the weight of mandrels 162 is such that the trailing ends 166 will not float upwardly or sink from the aforementioned desired position in the layer 140.In a preferred embodiment, conventional electrically energized immersion heaters 178 are provided within mandrels 162 for heating the same thereby to accelerate curing of the cementitious material. Mandrels 162 have a limited rotary oscillatory troweling motion imparted thereto about their axes by the arrangement now to be described. Referring specifically to FIG. 4, in the illustrated embodiment, one group 180 of the mandrels 162 respectively have ends 182 of lever members 184 secured to projecting portions of rods 168. The upper ends 166 of lever members 184 are respectively pivotally connected together by members 188. A conventional hydraulic cylinder 190 is provided having its rear end pivotally connected to a side of frame 46, as at 192, and having its piston rod 194 connected to members 188, as at 196. It will thus be seen that protractile movement of piston rod 194 of cylinder 190 will result in movement of members 198 and levers 184 to the position shown in dashed lines in FIG. 4, whereas retractile movement of piston rod 194 will move members 188 and levers 184 to the position shown in solid lines. Thus, reciprocatory motion of piston rod 194 results in reciprocatory motion of members 188, as shown by the arrows 198, in turn resulting in rotary, oscillatory troweling motion of mandrels 162, as shown by the arrows 200. Suitable limit switches, schematically shown at 202 and 204, respectively sense the two extremities of the reciprocatory movement of members 188 and are coupled to a suitable solenoid reversing valve 206 for controlling the reciprocatory action of hydraulic cylinder 190. In the illustrated embodiment of the apparatus which incorporates l2 mandrels 162, the mandrels are divided into two groups each having the rotary, oscillatory troweling motion imparted thereto by a cylinder 190, as best seen in FIG. 2.

In the preferred embodiment of the assembly 16, mandrels 162 rotate about one-fourth revolution, and hopper 138 is disposed and auger 154 is driven so as to deposit layer 140 of cementitious material to a level so that its upper surface 208 is substantially even with the tops of the mandrels 162, as best seen in FIG. 8. In this connection, it will be observed that the edge 150 of sidewall 146 of hopper 138 will provide a bulldozing action to assist in depositing the layer 140 to the level 208.

A plurality of vibrating devices 210 are disposed between mandrels 162 and adjacent to side

mold elements

28, 30, closely adjacent rear edge 150 of discharge opening 152 of hopper 138, vibrating devices 210 being further disposed adjacent the tops of mandrels 162, as best seen in FIGS. 3 and 5. Vibrating devices 210 are individually driven by variable speed electric drive motors 212 mounted on frame element 214 forwardly of front wall 144 of hopper 138, each motor 212 being connected to and supporting its respective vibrating device 210 by conduit 216 enclosing a conventional flexible drive shaft. The vibrating devices 210 function to continuously pack the cementitious material between the mandrels 162 and

side elements

28, 30 as it is deposited by the auger 154 from the hopper 138. The speeds of the drive motors 212 and thus of the vibrating devices 210 are individually selectively controlled by speed controls 218 mounted on control panel 220.

ln accordance with the invention, an elongated length of metal mesh material 222 is provided having a width slightly less than the width of the mold 12 between the

side mold elements

28, 30. As will be hereinafter more fully described, free end 224 of mesh 222 is initially secured to a member 226 which is mounted adjacent the rear or starting end 228 of mold 12. Mesh 222 extends forwardly over mandrels 162 and is accommodated on and payed out by a reel 230 rotatably supported by members 232 extending upwardly from frame 46, reel 230 being disposed rearwardly of the hopper 138. Mesh 222 is trained around guide rollers 234 which are respectively disposed in alignment with the spaces between the mandrels 162, rollers 234 pressing the mesh 222 downwardly against the tops of mandrels 162 and into the top surface 208 of cementitious material layer 140 between the mandrels, as best seen in FIG. 8. Mesh 222 is maintained in tension as the assembly 16 moves forwardly in direction 18 by means of a suitable brake device 236 acting upon reel 230. It will thus be seen that as the forward movement of assembly 16 progresses in direction 18, mesh 222 is laid, under tension, over cementitious material layer 140 and mandrels 162, being pressed into the top surface 208 of layer 140 by roller 234.

A second elongated hopper 236 is mounted on extension portion 238 of frame 46 which extends rearwardly from the rear end 174, hopper 236 extending transversely across mold 12 over mandrels 162, cementitious material 140 and mesh 222, and being similar in construction to hopper 138. Hopper 236 has an upper open end 240, a lower discharge opening 242, and a force feeding and distributing auger 244 therein adjacent the discharge opening 242. Hopper 236 receives cementitious material and in conjunction with auger 244 deposits a second layer 246 over mandrels 162, the first layer 140 and mesh 222, as best seen in FIG. 8. Auger 244 is selectively driven in opposite directions by another hydraulic motor 248 which drives gearbox 250, which, in turn, drives auger 244 through a drive chain 252.

Hopper 236 is preferably continuously filled by means of an elevating auger 254 and an open trough 256 which in inclined upwardly from adjacent the forward hopper 138 toward the rear hopper 236, as best seen in FIG. 3. Elevating auger 254 is driven by a conventional electric motor 258 through a belt 260. Thus, by employing two separate chutes from a readymix truck or two separate like devices, one for depositing the cementitious material into the hopper 138, and the other for depositing cementitious material in the trough 256 for elevation by auger 254 and depositing in the rear hopper 236, both

hoppers

138 and 236 can be supplied with cementitious material.

The second layer 246 of cementitious material is compacted and its top surface 262 is finished by a vibratory screed 264 supported on frame extension portion 238. Various inserts, hardware or the like (not shown) may be placed in slab 14 after the mesh has been laid on top of the mandrels before the mandrels have been removed from the slab portion in which the inserts are desirably placed. Adjacent to side

elements

28, 30 and around such inserts, surface 262 must be finished by hand.

Ends 166 of mandrels 162 also may be secured to brackets 172 by means of projecting portions 171 of rods 168, both of the projecting

portions

170 and 171 being adapted to be removably rotatably mounted in brackets 172 and removably connected to ends 182 of levers 184. With this arrangement, when the apparatus 16 has advanced to the far end of mold l2, remote from the starting end 228, and a slab has been completed and the resulting elongated slab has been sawed into shorter sections and the sections removed, projecting ends 170 may be disconnected from brackets 172 and levers 184, the assembly 16 can be turned end-for-end, and the projecting ends 171 can be connected to brackets 172 and ends 182 of levers 184, thereby making ends 166 of mandrels 162 the leading ends. The assembly 16 may then be advanced back to the former starting end of the mold to form another slab, thus eliminating the necessity for conveying the entire assembly back to the starting end of the mold prior to forming another slab.

THE METHOD Prior to commencing motion of the assembly 16 on the

rails

32 and 34 of the

side mold elements

28 and 30, transversely extending, longitudinally spaced-apart reinforcing strands 266 are placed in the mold cavity, and longitudinally extending, transversely spaced-apart prestressing strands 268 are placed thereover and extending the length of the mold. Strands 268 having their ends 270 secured to member 226 and their other ends (not shown) suitably tensioned, as by the use of appropriate hydraulic tensioning jacks. Transverse and longitudinally extending reinforcing

strands

266 and 268 are held in assembled relation and spaced from the top surface 40 of base 20 by conventional spacers 272. Other hardware such asjunction boxes 274, window frames, conduits and the like may also be positioned within the mold cavity if desired. Assembly 16 is positioned on

rails

32 and 34 with trailing ends 166 of mandrels 162 adjacent mold end 228, and end 224 of mesh 222 is secured to member 226. If desired, cementitious material may be placed by hand in the mold rearwardly from the front hopper 138 to the level of the tops of the mandrels 162, and to the desired level 262 rearwardly of the rear hopper 236. Rela-v tively fluid, wet cementitious material, for example concrete having a low slump, is then deposited from a ready-mix truck or like device in the hopper 138 and trough 256 and forward movement of the assembly 16 in the direction shown by the arrow 18 is commenced. As the forward movement progresses, the bottom layer of cementitious material is deposited by trough 138 and auger 154 to a level substantially even with the tops of the mandrels 162, that layer is tamped between the mandrels and

adjacent side elements

28, 30 by vibratory devices 210, the mesh 222 is payed out from the reel 230, under tension, and is pressed onto the tops of the mandrels 162 and into the top surface 208 of layer 140 by rollers 234, the second layer 246 is deposited over the mandrels 162, mesh 222 and the bottom layer 140 by hopper 236 and the auger 244, and that layer is compacted and its top surface 262 finished by the vibratory screed 264.

It will be observed that the floating mandrels 162 have their leading ends 164 pulled forwardly in the direction 18 by the forward motion of the assembly 16 thereby forming the core openings in the resulting slab. The mesh 222 serves not only as reinforcing material in the finished slab, but further, in combination with the cementitious layer 140, supports the top layer 246 of wet cementitious material so that the core openings formed by the advancing mandrels 162 do not collapse. It will be observed that the rotary oscillatory motion imparted to the mandrels 162 provides a troweling action for the interior surfaces of the core openings formed by the mandrels 162 as the mandrels advance in the direction 18.

There are a number of factors which must be correlated in order to form a satisfactory slab. These include the linear rate of speed of the assembly 16 in direction 18, the formulation of the cementitious material used, including in one specific embodiment the cement-aggregate-sand ratio, the moisture content and curing time of the concrete mixture, the consistency or slump of the mixture, which is applied in wet or fluid form, the aggregate size and weight, and the size of the mesh 222 which must support the upper cementitious layer 246 in a wet condition. More particularly, the linear rate of speed, curing time, consistency and mesh size must be correlated so that the core openings formed by the mandrels 162, as they advance forwardly in direction 18, do not collapse, and the-linear rate of speed, moisture content and curing time must further be correlated so that the requisite smooth finish is formed on the top surface 262 by the vibratory screed 264.

In a specific embodiment of the apparatus and method for forming slabs 8 inches thick and 8 feet wide, 12 mandrels respectively 30 feet long and having a 6-inch outside diameter were employed. A concrete mix having a slump from about 1 inch to about 2 inches is employed, preferably using a formula comprising from about 1,000 lbs. to about 1,300 lbs. of No. 9 stone; from about 1,700 lbs. to about 2,000 lbs. of No. 14 sand; from about 650 lbs. to about 760 lbs. of high early cement; from about 18 to about 25 ounces of a water dispersing agent (100N, as sold by Master Builders); and from about 30 to about 40 gallons of water (correcting for moisture in gravel and sand, humidity, etc.). Using a formula within this range, the assembly 16 can be moved at a linear forward speed within the range from about 1 foot per minute to about 6 feet per minute.

Particularly satisfactory results have been provided with a linear forward speed of about 2 feet per minute and a formula comprising about 1,052 lbs. of No. 9 stone, 1,933 lbs. of No. 14 sand; 752 lbs. of high early cement, 23 ounces of the above-identified water dispersing agent, and 40 gallons of water.

After formation of the slab 14 in the mold, curing may be further accelerated by the use of cover members 276 removably positioned on the

top rails

32 and 34 of the

side mold elements

28 and 30, and extending over the slab l4 and enclosing the mold cavity, cover members 276 having suitable electrical heating elements 278 therein.

What is claimed is:

1. Apparatus for forming a cored cementitious slab comprising a mold, said mold having spaced-apart side elements for forming the sides of a slab and a bottom element having an upwardly facing surface for forming the bottom surface of a slab, means for moving said side elements relative to said bottom element between a first position in which said side elements extend upwardly from said surface of said bottom element and define a mold cavity therewith, and a second position in which said side elements are substantially removed from cooperative relationship with said bottom surface thereby to eliminate said mold cavity, means for progressively laying a layer of cementitious material in said mold, said laying means including means for receiving said material in relatively fluid form and depositing the same in said mold, means for moving said laying means relative to said mold in one direction, a plurality of spaced-apart and parallel mandrels disposed in said mold and under said depositing means, said mandrels being elongated in said direction, said mandrels having ends disposed on opposite sides of said depositing means, means for attaching one end of said mandrels to said laying means whereby said mandrels move with said depositing means, and means for paying out reinforcing material over said mandrels as-said movement between said laying means and mold progresses.

2. Apparatus for forming a cored cementitious slab comprising an elongated mold having opposite ends, means for progressively laying a layer of cementitious material in said mold, said laying means including means for receiving said material in relatively fluid form and depositing the same in said mold, means for moving said laying means relative to said mold in the direction of elongation thereof toward one mold end and away from the other mold end, a plurality of spacedapart and parallel mandrels disposed in said mold and under said depositing means, said mandrels being elongated in the direction of said movement, said mandrels having ends disposed on opposite sides of said depositing means, means for attaching one end of said mandrels to said laying means whereby said mandrels move with said depositing means, an elongated length of mesh material having a free end, said free end being attached to said mold adjacent to said other end thereof, said laying means including a reel of said mesh material rotatably mounted on said laying means between said depositing means and said other mold end, means for restraining the rotation of said reel, and means engaging said mesh material for urging said mesh material against said mandrels as said movement between said laying means and mold progresses.

3. The apparatus of claim 2 wherein said mold is stationary and includes spaced parallel side elements for forming said sides of said slab, and a bottom element for forming said bottom surface, said moving means including means for supporting said laying means adjacent said side elements of said mold.

4. The apparatus of claim 1 further comprising means for imparting motion to said mandrels.

5. The apparatus of claim 1 wherein said mandrels are respectively hollow and have liquid therein to maintain said mandrels in said layer.

6. The apparatus of claim 1 further comprising means for heating said mandrels.

7. The apparatus of claim 2 wherein said laying means includes second means disposed over said mold and said mandrels and between said reel and said other mold end for receiving cementitious material in relatively fluid form and depositing a second layer thereof in said mold over said first-named layer and said mesh material.

8. Apparatus for forming a cored cementitious slab comprising an elongated mold for forming the parallel opposite sides and the bottom surface of said slab; and means for progressively laying a layer of cementitious material in said mold including means disposed above said mold for receiving said material in relatively fluid form and depositing the same in said mold, means for relatively longitudinally moving said laying means with respect to said mold in the direction of elongation thereof, a plurality of elongated mandrels disposed in said mold in a spaced, parallel relationship and extending in the direction of said relative movement for forming longitudinally extending core openings in said slab, said mandrels having spaced opposite ends and having portions intermediate said ends disposed under said depositing means, means for attaching the leading ends of said mandrels to said laying means thereby relatively moving said mandrels with said depositing means, said laying means including second means disposed over said mold and said mandrels for receiving cementitious material in relatively fluid form and depositing a second layer thereof in said mold over said first-named layer, said laying means including means cooperating with said first layer for supporting said second layer, said second layer of cementitious material being deposited over said supporting means, said mold having spaced opposite ends, said direction of relative movement being toward one mold end and away from the other, said supporting means being an elongated length of mesh material having a free end, said free end being attached to said mold adjacent said other end thereof, means for paying out said mesh material in response to movement of said laying means, said paying out means including a reel rotatably mounted on said laying means between said first-named and second depositing means for accommodating a supply of said mesh material, and means for tensioning said mesh material as said relative movement progresses.

9. Apparatus for forming a cored cementitious slab comprising an elongated mold for forming the parallel opposite sides and the bottom surface of said slab, and means for progressively laying a layer of cementitious material in said mold including means disposed above said mold for receiving said material in relatively fluid form and depositing the same in said mold, means for relatively longitudinally moving said laying means with respect to said mold in the direction of elongation thereof, a plurality of elongated mandrels disposed in said mold in a spaced, parallel relationship and extending in the direction of said relative movement for forming longitudinally extending core openings in said slab, said mandrels having spaced opposite ends and having portions intermediate said ends disposed under said depositing means, means for attaching the leading ends of said mandrels to said laying means thereby relatively moving said mandrels with said depositing means, said mold being stationary and having spaced opposite ends, said direction of relative movement being toward one mold end and away from the other, said laying means including a frame, said moving means including wheels for movably supporting said frame adjacent to said mold, each of said mandrels having a longitudinally extending axis, said attaching means including means mounted on said frame for supporting said leading ends of said mandrels for rotational movement about their respective axes, and means for imparting limited oscillatory movement to said mandrels about their respective axes, the trailing ends of said mandrels which face toward said other mold end being unsupported by said frame and projecting substantially beyond the same, said depositing means including a first hopper supported on said frame, said first hopper having an auger therein and extending transversely across said mold, said first hopper being disposed to deposit said layer to a level generally even with the tops of said mandrels, means for vibrating said layer, an elongated length of mesh material having a free end, said free end being attached to said mold adjacent said other end thereof, a reel rotatably mounted on said frame for accommodating said mesh material and paying out the same over said mandrels and layer as said relative movement progresses, means for tensioning said mesh material as it is payed out, means for pressing said mesh 5.1.0 material against said mandrels and layer, second depositing means including a second hopper mounted on said frame, said second hopper having an auger therein and extending transversely across said mold for receiving cementitious material and depositing a second layer thereof in said mold over said first-named layer and mesh material.

10. The apparatus of claim 1 further comprising a cover member for removably covering said mold with said slab therein, and means for heating said cover member for accelerating the curing of said slab.

11. The apparatus of claim 1 wherein said mold includes a base member for forming said bottom surface, and further comprising means for heating said base member for accelerating the curing of said slab.

12. The apparatus of claim 1 wherein said laying means includ'es a frame, said depositing means being supported on said frame, said mandrels being attached to said frame, and said frame being supported on opposite sides of and adjacent to said mold.

13. The apparatus of claim 1 wherein each of said mandrels has a longitudinal axis extending between said ends thereof, and further comprising means for imparting limited rotary oscillatory movement to said mandrels about their respective axes.

14. The apparatus of claim l further comprising means respectively disposed between said mandrels for vibrating the material deposited in said mold.

15. Apparatus for forming a cored cementitious slab for use with a mold having spaced apart side elements for forming the sides of the slab and a bottom element with an upwardly facing surface for forming the bottom surface of the slab comprising means for progressively laying a layer of cementitious material in a mold, said laying means including means for receiving said material in relatively fluid form and depositing the same in the mold, means for moving said laying means relative to the mold, a plurality of spaced-apart mandrels which are to be placed in the mold between the side elements thereof, said mandrels being beneath said depositing means, said mandrels being attached to said laying means whereby said mandrels move with said depositing means, and means for paying out a cementitious material supporting material over said mandrels, and means for urging said supporting material against said mandrels.

Claims

1. Apparatus for forming a cored cementitious slab comprising a mold, said mold having spaced-apart side elements for forming the sides of a slab and a bottom element having an upwardly facing surface for forming the bottom surface of a slab, means for moving said side elements relative to said bottom element between a first position in which said side elements extend upwardly from said surface of said bottom element and define a mold cavity therewith, and a second position in which said side elements are substantially removed from cooperative relationship with said bottom surface thereby to eliminate said mold cavity, means for progressively laying a layer of cementitious material in said mold, said laying means including means for receiving said material in relatively fluid form and depositing the same in said mold, means for moving said laying means relative to said mold in one direction, a plurality of spaced-apart and parallel mandrels disposed in said mold and under said depositing means, said mandrels being elongated in said direction, said mandrels having ends disposed on opposite sides of said depositing means, means for attaching one end of said mandrels to said laying means whereby said mandrels move with said depositing means, and means for paying out reinforcing material over said mandrels as said movement between said laying means and mold progresses.

2. Apparatus for forming a cored cementitious slab comprising an elongated mold having opposite ends, means for progressively laying a layer of cementitious material in said mold, said laying means including means for receiving said material in relatively fluid form and depositing the same in said mold, means for moving said laying means relative to said mold in the direction of elongation thereof toward one mold end and away from the other mold end, a plurality of spaced-apart and parallel mandrels disposed in said mold and under said depositing means, said mandrels being elongated in the direction of said movement, said mandrels having ends disposed on opposite sides of said depositing means, means for attaching one end of said mandrels to said laying means whereby said mandrels move with said depositing means, an elongated length of mesh material having a free end, said free end being attached to said mold adjacent to said other end thereof, said laying means including a reel of said mesh material rotatably mounted on said laying means between said depositing means and said other mold end, means for restraining the rotation of said reel, and means engaging said mesh material for urging said mesh material against said mandrels as said movement between said laying means and mold progresses.

6. The apparatus of claim 1 further comprising means for heating said mandrels.

9. Apparatus for forming a cored cementitious slab comprising an elongated mold for forming the parallel opposite sides and the bottom surface of said slab, and means for progressively laying a layer of cementitious material in said mold including means disposed above said mold for receiving said material in relatively fluid form and depositing the same in said mold, means for relatively longitudinally moving said laying means with respect to said mold in the direction of elongation thereof, a plurality of elongated mandrels disposed in said mold in a spaced, parallel relationship and extending in the direction of said relative movement for forming longitudinally extending core openings in said slab, said mandrels having spaced opposite ends and having portions intermediate said ends disposed under said depositing means, means for attaching the leading ends of said mandrels to said laying means thereby relatively moving said mandrels with said depositing means, said mold being stationary and having spaced opposite ends, said direction of relative movement being toward one mold end and away from the other, said laying means including a frame, said moving means including wheels for movably supporting said frame adjacent to said mold, each of said mandrels having a longitudinally extending axis, said attaching means including means mounted on said frame for supporting said leading ends of said mandrels for rotational movement about their respective axes, and means for imparting limited oscillatory movement to said mandrels about their respective axes, the trailing ends of said mandrels which face toward said other mold end being unsupported by said frame and projecting substantially beyond the same, said depositing means including a first hopper supported on said frame, said first hopper having an auger therein and extending transversely across said mold, said first hopper being disposed to deposit said layer to a level generally even with the tops of said mandrels, means for vibrating said layer, an elongated length of mesh material having a free end, said free end being attached to said mold adjacent said other end thereof, a reel rotatably mounted on said frame for accommodating said mesh material and paying out the same over said mandrels and layer as said relative movement progresses, means for tensioning said mesh material as it is payed out, means for pressing said mesh material against said mandrels and layer, second depositing means including a second hopper mounted on said frame, said second hopper having an auger therein and extending transversely across said mold for receiving cementitious material and depositing a second layer thereof in said mold over said first-named layer and mesh material.

12. The apparatus of claim 1 wherein said laying means includes a frame, said depositing means being supported on said frame, said mandrels being attached to said frame, and said frame being supported on opposite sides of and adjacent to said mold.

14. The apparatus of claim 1 further comprising means respectively disposed between said mandrels for vibrating the material deposited in said mold.