US3618888A - Casting forms - Google Patents

Abstract

A long, steel open-ended form has upstanding smooth sides from the form bottom to provide full width of a concrete slab casting; the sides then continuing upwardly and inwardly to reduce the width of a casting slab; after which the form side continues upwardly for constant but reduced slab width; the upwardly and inwardly disposed form side being flat but having at least 50 percent of its casting surface ''''dimpled'''' inwardly of the casting region with the ''''dimple'''' depth being a maximum at or near the top of the inwardly extending side portion and reduced to zero at or near the bottom of said portion.

Description

United States Patent Primary Examiner.l. Spencer Overholser Assistant Examiner-Ben D. Tobor Attorney-Robert L. Kahn ABSTRACT: A long, steel open-ended form has upstanding smooth sides from the form bottom to provide full width of a concrete slab casting; the sides then continuing upwardly and inwardly to reduce the width ofa casting slab; after which the form side continues upwardly for constant but reduced slab width; the upwardly and inwardly disposed form side being flat but having at least 50 percent ofits casting surface dimpled" inwardly ofthe casting region with the dimple" depth being a maximum at or near the top of the inwardly extending side portion and reduced to zero at or near the bottom of said portron.

CASTING FORMS This invention relates to a casting form for making long concrete slabs whose sides have grout keys extending longitudinally of the slab as well as transversely (between top and bottom slab faces). In my application Ser. No. 781,422 filed Dec. 5, 1968, and assigned to the assignee of the present application, there is disclosed a slab having grout keys extending longitudinally of the slab as well as transversely (between top and bottom slab faces). The grout keys, when filled with grout, lock adjacent slabs against stresses normally encountered in a building as well as stresses occurring during an earthquake or excessive ground vibration.

A casting form for making such slabs must fulfill a number of conditions incident to the process for producing such slabs. Inasmuch as all grout keys for slab sizes are concave with respect to the slab sides, a finished casting will normally be locked against removal by lateral movement of the casting, in the absence of special provisions therefor. Various casting form structures may incorporatesuch special provisions. A generally similar problem has been present for many years in the manufacture of slabs having only longitudinally extending grout keys along the slab sides. As an example, in U.S. Pat. Nos. 2,299,070; 2,299,071; and 2,299,072, a slab construction is disclosed (this slab may either be prestressed or not) wherein a grout keyway at each slab side is provided for grout to interlock adjacent slabs when installed to make a floor or deck. In U.S. Pat. No. 3,023,476 there is disclosed a casting from to create a modified grout keyway to meet the exigencies of slab removal from a so-called one-piece casting form. In such a casting form, the slab sides and slab pan or bottom are integral and casting removal is effected by spreading the slab sides sufficiently to permit slab removal laterally from the casting form rather than longitudinally thereof. In that patent, the engineering requirements for a slab grout key are set forth in terms of the limitations of spreading the casting form sides to release a casting.

While a casting having the longitudinal and transverse grout I keys as disclosed and claimed in my previous application may be made in a variety of casting forms, it is preferred to utilize a modified one-piece casting form for making such slabs. This modified one-piece casting form may be stripped by the means disclosed and claimed in U.S. Pat. Nos. 3,061,904 and 3,142,106.

Irrespective of the details of the casting form employing the present invention, it is necessary that certain precautions be observed for satisfactory casting. An exemplary casting form embodying the present invention will be disclosed in connection with the drawings, it being understood that the general principles of the construction may be embodied in various casting forms that may differ among themselves, principally with regard to accommodation to stripping procedures.

Referring now to the the drawings:

FIGS. 1, 2, and 3 are respectively perspective, plan and side views of the new casting form.

FIG. 4 is an end view along line 4-4 of FIG. 1.

FIG. 5 is an enlarged view of a part of the casting form side.

FIGS. 6 and 7 are enlarged details along lines 6-6 and 7-7 of FIG. 5.

FIG. 8 is a detail along line 8-8 of FIG. 4.

A casting form embodying the present invention will be made of steel and will have a length up to about 50 or 60 feet, a width (in the casting region) ,from about 16 inches to as much as 48 inches or more, and a depth (in the casting region) from about 4 inches to about 16 inches or more. The length and width of the casting regionmay be reduced by bulkheads and partitions in a casting form having maximum dimensions. The type of steel used for various parts of an entire casting form will depend upon stresses to be encountered and this in turn will depend upon the stripping procedure to be used.

The new casting form has pan 10 consisting of pan bottom 11 and pan sides 12 extending the full length of a casting form. The ends of a casting form are open and may be provided with bulkheads. Pan sides 12 and bottom 11 have curved corners 13 between them. Corners 13 are curved to a 90 angle along as short a radius as possible consistent with sound engineering, architectural and esthetic considerations. For casting forms up to about 24-inch wide slabs, pan bottom 11 may be of 54-inch steel plate, the thickness of which is maintained substantially at corners I3 and sides 12. Corners 13 will usually have a radius of curvature of the order of about three-eighth inch. As is well known, too sharp a corner will overstress the metal and impair the ability of the casting form to function properly during stripping. The general form constructionis the same for each side. For 48-inch wide slabs, pan 11 may be of 39-inch steel plate. For much wider slabs, still thicker steel plate may be used.

Pan side 12 terminates in top edge 15. The elevation of pan edge 15 above pan bottom face Ila may be the same for various sizes of casting forms. As an example, top edge 15 of pan 10 may be about 2% inches above bottom face 110 of pan bottom 11. Standardizing on such a dimension simplifies the problem of jigs and tools for welding, grinding, and working on the structure. Rigidly secured to outer face 12a of pan side 12, as by welding along the form length, is steel channel 19 having web 20 and flanges 21 and 22. Web 20 has its width (between flanges 21 and 22) depending upon the maximum depth of the casting region. Channel 19 extends the full length of the casting form and must be strong enough to reinforce the casting form and be used in conjunction with stripping, as explained in U.S. Pat. No. 3,142,146. Flange 21, at the bottom of the channel has bottom outer face 210 below the level of bottom face 11a of pan 10. This is helpful to maintain clearances during conveying and stacking and avoids damage to the pan during handling of casting forms.

Rigidly secured to outer face 20a of channel web 20 is spacer strip 23 of steel. Strip 23 extends for the entire length of the casting from and is welded (or attached otherwise) to web face 20a so bottom edge 23a is spaced a short uniform distance (as for example onesixteenth inch) and may have a width of about 1 inch as an example. Care must be taken in locating strip 23 on web face 20a accurately throughout the form since it functions as a guide.

Filler piece 24 is of steel and need only be present at the form ends to seal against entry of sand, etc. within the form parts. Filler piece 24 is shaped to close up the region to be sealed. Above spacer strip 23 is auxiliary spacer plate 27 whose thickness is substantially uniform. Spacers 23 and 27 extend the full length of the casting form and are welded in positions shown to face 20a of the channel web. Notches and grooves in these spacers at appropriate places along lines of welding may be provided, such expedients being well known.

Outer face 22a of channel flange 22 has steel spacer strip 30 welded to the channel flange. Above strip 30 is reinforcement plate 31 welded to the channel flange tip. Strips 30 and 31 extend the full length of the form. Spacer strip 30 is provided to maintain desired dimensions closely between the top of plate 31 and face 11b of the pan as well as between faces 11a and 21a. Channels 19 and other parts from suppliers have generous tolerances.

Rigidly supported above top edge 15 of pan side is grout key plate 32, having straight bottom edge 33 and straight top edge 34 extending the length of the casting form. Grout key plate 32 is rigidly secured with bottom edge 33 disposed a short distance above top edge 15 of the pan side. Inasmuch as inner surface of the pan side and inner surface 32:; of the grout key plate define part of the casting region, it is important that the meeting between edges 15 and 33 be completely smooth and free of voids. To that end, it is preferred to space these two edges a short distance, such as of the order of one-sixteenth inch, and till this space along the entire length of the form with weld metal after which the welded joint may be ground to a smooth flush surface. By spacing the edges apart, there will be less likelihood of small voids occurring and a smooth welded surface joining the two edges can be more easily produced. Also this space dimension may be controlled to take up tolerances and supplement the action of spacer 30.

It is understood that grout key plate 32 may be made up of several successive lengths of material in which case abutting ends will have to be welded and ground down to a smooth flush joint.

Grout key plate 32 consists of lower dimpled portion 35 and flat upper portion 36 between which is boundary line 37. Plate portions 35 and 36 may either be originally separate and welded together along line 37 or may be from one original strip of steel. Three-sixteenth-inch steel may be used to facilitate dimpling procedure to reduce overall costs.

Top edge 34 of grout key plate 32 is flush with the top sur face of reinforcing plate 31. The grout key-forming part of the entire casting form extends from the top of pan surface 12b (opposite edge 15) upwardly to grout key plate top edge 34, or somewhat below, depending upon how much of the casting form depth is utilized. Along surface 12b, the casting form width between pan sides 12 is a maximum.

Undimpled, normally flat plate portion 35, extends up at a slant to flat plate portion 36. Portion 36 will normally lie in a vertical plane while the flat part of portion 35 will be at a small angle to the vertical. In practice, plate portion 35 will be a few degrees from the extension of plate portion 36. The disposition of plate portion 35 is such that along edge 33 the casting form width is a maximum (this being true for everything below edge 33). From edge 33 up to line 37, the casting region width decreases and then remains constant to top edge 34.

If two slabs are disposed in side by side relation, the slab sides adjacent the bottom slab face (created by pan surface 11b) will abut. Between about one-fourth and about one-half of the slab thickness, the slab sides (corresponding to edge 33 in the casting form) will begin to diverge and then the slab sides will continue straight up. As an example, a twenty-four inch wide slab may have its width reduced to about 23%. inches (Mi-inch short at each side). The slab thickness for full width may be about 2 or 2% inches. The slab thickness where the width gradually narrows may be about 5 to 6 inches and the slab thickness where the slab width is constant to the top face of the slab may be from about k inch to about 2% inches, depending on slab thickness. The figures given above are for slabs of from 6 to 8 inches in thickness. The dimensions are exemplary and may vary. The angle between plate portions 35 and 36 will vary somewhat with dimensions but will generally be less than 10.

Referring now to grout key plate 32 and particularly to portion thereof, at longitudinally spaced intervals, there is provided a dimple or embossing 40. The shape of each embossing and the proportion of embossed area to total area of portion 35 may vary. An embossing or dimple may be circular or generally rectangular. The proportion of embossed area to total plate area of portion 35 is preferably between about 50 percent and about 75 to 80 percent. The combination of generally rectangular or wedge shape and spacing between adjacent dimples provides for controlled grout chambers. The dimensions of grout keys at various regions along the length of a slab and at various depths from the top face of a slab will endow adjacent slabs, when grouted together side by side, with desired resistance to stresses. Thus the generally wedgeshaped dimple" will dispose a substantial part of the dimple area near dividing line 37. A circular dimple shape will not be as desirable. The dimple" depth or height (the amount of lateral deflection of metal from the original plane of plate portion 35) is a function of the elevation about pan bottom 11. This is premised upon the use of a so-called one-piece casting form, which is stripped by spreading the form sides as set forth in the U.S. Pat. Nos. 3,023,476 and 3,023,477, issued on Mar. 6, 1962. Assuming the form sides are rigid, it is evident that the higher the dimple" peak is from pan bottom 11, the easier it will be to strip a form without overstressing the entire pan structure. Also the slope of the dimple from peak to lower edge 33 should satisfy the geometrical conditions set forth in the aforementioned patents for a keyway. It is apparent therefore that the generally wedge shape of dimple" with top side of maximum depth close to the top of the dimpled plate portion 35 has particular value in a casting form.

Referring specifically to dimple 40, top side 40a is parallel to and just short distance below boundary line 37 between plate portions 35 and 36. Thus about one-fourth inch of flat metal between line 37 and line 40a may be provided. Sides 40a to 40d inclusive show where the plate metal merges into the original flat plate stock. The overall length of top side 400 up to a curved corners may be about 2% inches. The length of bottom side 4011 where the dimple" merges into the flat metal is less, about 2 inches as an example. Sides 40b and 400 are inclined toward each other. With corners having a radius of about one-half inch between top 40a and sides 40b and 40c, the overhang of the rounded corners along line 33 will be about one-half inch on each dimple side. Sides 40a to 40d inclusive and rounded corners define the edges of a female die. The dotted lines 41a to 41:: represent the dimple" boundaries of the generally flat interior area of a dimple." The dotted outline of sides 41a to 41c define the outline of a male die. A clearance of about five-sixteenth inch between sides 40a and 41a for working on 3/ 16-inch steel plate is provided, such clearance tapering down to about three-sixteenth inch along bottom side 40d. The maximum depth of a dimple can be about one-fourth inch, this being along side 41a.

The direction a dimple extends is toward the casting region interior so that a casting will have a concave region at the side. Care must be taken to insure that dimples 40 have their top and bottom sides aligned along the length of portion 35. Adjacent dimples may have the separation between them at a desired value, depending upon engineering considerations. In the example discussed above, the curved corners of adjacent dimples may be spaced about 1 inch. Although this separation may be increased or decreased, for conventional slabs of about 6- or 8-inch thickness and widths of the general order of from 16 to 24 or 30 inches, the general dimensions given by way of example will generally be satisfactory. For much shallower slabs, having a thickness of about 4 inches, the key dimensions and dimple will have to be reduced somewhat.

Inasmuch as the convex face of grout key plate portion 35 is a slab casting surface, it is important that the dimpling or embossing area in plate portion 35 be limited to the areas defined. Thus the plate portions above aligned top sides 400 should be flat so that dividing edge 37 will be straight and true. This will make it possible to bend plate 36 with reference to plate portion 35 (if they are of one piece) or weld the two and grind the casting surface side to a smooth surface.

The same considerations apply to lower edge 33 of plate portion 35. While bottom sides 40d of dimples" 40 are aligned a short distance (about one-fourth inch) above edge 33 it is important that bottom edge 33 be true and straight and not be uneven laterally of the plate, especially where dimpling" has occurred.

The ends of a casting form should be free of cracks, burrs, and cavities between parts making up a form. Bulkhead locating pins 50 may be welded to the exterior of a casting form at the ends thereof. All casting surfaces should be smooth and true to provide satisfactory castings. The fact that plate portions 35 and 36 are originally flat makes for easier fabrication of the form. The dimpling is limited to one portion (plate portion 35) and the separation of separate dimples" makes it easier to make a long form to close specifications. In addition, the relative dimple dimensions longitudinally of the form and dimple spacing insures substantial dimple registration of two abutting slabs in spite of some longitudinal misalignment.

Iclaim:

l. A steel form for casting concrete slabs having a casting region length up to about 60 feet and a casting region width from about 16 inches to over 4 feet and a casting region depth from about 4 inches to about 16 inches, said form having open ends and opposed upstanding sides extending the full length of said form, said form having a substantially flat bottom and curved corners between said bottom and sides, each form side having the lowest portion extending vertically up from the curved corner for at least about one-third of the desired slab thickness to be cast, a steel channel having the outer face of the web secured to the outer face of the upwardly extending lowest portion, the channel length extending along the form length, the channel width being generally equal to the form depth with the channel flanges extending outwardly away from the form sides, each form side having second side portion continuing upwardly and inwardly at a slight angle for about one-half of the slab thickness, said second side portion being of steel and having less thickness than the lowest side portion steel so that the metal faces functioning as casting form surfaces are flush, the rear face of the second side portion being spaced from the channel web face, a thin steel guide strip rigidly secured along the form length to the outer web face of the channel between the web face and the rear face of the second side portion, the bottom edges of the guide strip and the second side portion being aligned a predetermined distance above the top edge of the lowest side portion, each fonn side having a third portion extending vertically from the top of said second side portion, said lowest and third side portions lying in vertical but laterally offset planes, metal spacing means between the web outer face and opposed face of the third side portion and secured thereto, metal weld material filling space between the opposed edges of the lowest side portion and second side portion, said weld metal having the outer surface finished to provide a casting surface to cooperate with the remaining casting surfaces, the second side portion having less than about 50 percent of its surface area flat and the remainder thereof being laterally deformed to provide separate convex areas extending toward the opposite form side, all said casting surfaces being smooth, a transverse form section having lines corresponding to the second and third side portions so dimensioned and the lateral deformations being so located and dimensioned as to permit lateral stripping by maintaining the form sides rigid and spreading such sides with respect to the form comers and bottom without damage to the form.

2. The construction according to claim 1 wherein each deformed convex area has its maximum deflection from the plane of said second side portion located near the top of said second side portion.

3. The construction according to claim 2 wherein each deformed convex area has a wedge shape with the longest side being at the top, the maximum deflection being near the top and zero deflection being near the bottom of said second portion.

4. The construction according to claim 3 wherein adjacent wedge-shaped convex areas are spaced from each other a distance less than the widths longitudinally along the form lengths of such convex areas.

Claims (4)

1. A steel form for casting concrete slabs having a casting region length up to about 60 feet and a casting region width from about 16 inches to over 4 feet and a casting region depth from about 4 inches to about 16 inches, said form having open ends and opposed upstanding sides extending the full length of said form, said form having a substantially flat bottom and curved corners between said bottom and sides, each form side having the lowest portion extending vertically up from the curved corner for at least about one-third of the desired slab thickness to be cast, a steel channel having the outer face of the web secured to the outer face of the upwardly extending lowest portion, the channel length extending along the form length, the channel width being generally equal to the form depth with the channel flanges extending outwardly away from the form sides, each form side having second side portion continuing upwardly and inwardly at a slight angle for about one-half of the slab thickness, said second side portion being of steel and having less thickness than the lowest side portion steel so that the metal faces functioning as casting form surfaces are flush, the rear face of the second side portion being spaced from the channel web face, a thin steel guide strip rigidly secured along the form lengTh to the outer web face of the channel between the web face and the rear face of the second side portion, the bottom edges of the guide strip and the second side portion being aligned a predetermined distance above the top edge of the lowest side portion, each form side having a third portion extending vertically from the top of said second side portion, said lowest and third side portions lying in vertical but laterally offset planes, metal spacing means between the web outer face and opposed face of the third side portion and secured thereto, metal weld material filling space between the opposed edges of the lowest side portion and second side portion, said weld metal having the outer surface finished to provide a casting surface to cooperate with the remaining casting surfaces, the second side portion having less than about 50 percent of its surface area flat and the remainder thereof being laterally deformed to provide separate convex areas extending toward the opposite form side, all said casting surfaces being smooth, a transverse form section having lines corresponding to the second and third side portions so dimensioned and the lateral deformations being so located and dimensioned as to permit lateral stripping by maintaining the form sides rigid and spreading such sides with respect to the form corners and bottom without damage to the form.

2. The construction according to claim 1 wherein each deformed convex area has its maximum deflection from the plane of said second side portion located near the top of said second side portion.

3. The construction according to claim 2 wherein each deformed convex area has a wedge shape with the longest side being at the top, the maximum deflection being near the top and zero deflection being near the bottom of said second portion.

4. The construction according to claim 3 wherein adjacent wedge-shaped convex areas are spaced from each other a distance less than the widths longitudinally along the form lengths of such convex areas.

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