US2320728A - Apparatus for molding concrete slabs - Google Patents

Description

3 Sheets-Sheet 1 W. R. HUME Filed Feb. 13, 1940 APPARATUS FOR MOLDING CONCRETE SLABS June l, 1943.

ATTYS.

W. R. HUME APPARATUS FOR MOLDING CONCRETE SLABS June l, 1943.

Filed Feb. 13, 1940 5 Sheets-Sheet 2 June l, 1943. w. R. HUME APPARATUS FOR MOLDING CONCRETE SLABS -3-Sheets-She'et 3 Filed Feb. l5, 1940 ATTYS.

Patented June l, 19,43`

APPARATUS FOR HOLDING CONCRETE SLABS waiter Reginald nume. Melbourne, victoria, Australia Application February 13, 1940, Serial No. 318,764

In Australia February 24, 1939 9 Claims.

This invention relates to the molding of con- 'crete slabs, blocks, tiles and the like, and refers more particularly to the molding of such articles from a relatively dry concrete mixture, usually termed a semi-dry mix. 'I'he invention is not, however,- limited to the use of such a mixture 'but is applicable generally to the manufacture of concrete slabs and the like.

The use of such a semi-dry concrete mixture.

wherein the water content is reduced to a lminimum, has decided advantages in that it obviates, to a great extent, the formation of voids, due to the evaporation of the excess water in the molded article and theleakage or flow'of the excess water, which is liable to cause localised accumulations of the cement binding agent, with the result that the product is not uniformly homogeneous, strong and well nished.

Hitherto, it has been the usual practice to mold such slabs and the like from the semi-dry concrete mix by manually placing the latter within the mold, which is then subjected to a vibratory action which is designed to distribute the low content of moisture through the material and convert the latter into amore p'asty or plasti state within the mold.

Considerable diiiiculty has been experienced in thus effectively molding the semi-dry material by vibration within the mold, particularly when relatively shallo molds, such as those used for concrete slab or'the like, are employed. With this known method, it has been found that the whole of the concrete in the mold is usually not converted into the desired pasty or plastic state necessary to produce a uniformly homogeneous product. Thus, parts of the material, forming the slab or the like;

dry material within the mold is slow and la-- borious owing to the necessity of manuallyi charging each mold with the material and of vibrating it for a relatively long period with the converted into the desired pastry or plastic condition within a suitable feed hopper or chamber prior to its introduction into the mold. By this process and apparatus, the relatively dry material may be effectively vibrated or agitated and converted to the desired plastic and homogeneous state during its passage through the feed hopper or the like so that it is already in the desired plastic condition when it enters the molds into which it may be expeditiously delivered in successive charges of the desired predetermined quantity as the molds are successively brought beneath the bottom or discharge opening of thehopper or the like, as hereinafter described.

In addition to insuring a more homogeneous land generally improvedy product, the invention also greatly facilitates the manufacture of slabs or the like owing to the fact that it is not neces- 'sary to manually ll or charge each mold and then subject the mold to the usualvibratory action. The feed hopper or the like may be of relatively large capacity so that the gravitational effect' of the weight=of the material therein, assisted by the vibratory or agitating action, causes the material to be automatically transferred or fed from the hopper or the like into the molds as they are successively brought .beneath the open lower end or discharge opening of the hop- The invention also embodies an improved method and means whereby sgrotary trowelling action is applied vto the surface of the concrete material after it has been introduced into the mold, this trowelling'action being adapted to effectively smooth or nish oiI the surface of .a rst rotary trowelling disc arranged immediately in advance of the hopper.

Figure 5 is a cross section on a reduced scale on the line V-V of Figure 4. v

Figure 6 is a cross-sectional view on line V11- VI of Figure 4 o n a somewhat reduced scale.

` Figure 'I is a side view showing the lower portion of the hopper andthe driving mechanism for upon the surface of the'material in the molds as they are carried'forwardly by the conveyor.

Figure 11 is a view of a modification embodying stationary trowelling plates for acting upon the surface of the material in the molds on the conveyor.

Figure l2 is a perspective view of portion of one of the trowelling plates seen in Figure 11.

Figure 13 is a longitudinal section of a mold having an inclined bottom plate or palette for the molding of slabs of tapered section.

Figure 14 is a perspective view of a slab showing a roughened ornamental surface surrounded by smooth marginal portions.

Figure 15 is a detail view of a modification wherein a shear blade is adapted to move between the bottom of the hopper and the molds to cut oi the successive charges of cementitious material.

Figures 16 and 17 are respectively, a plan and a cross section on the line XVlI-XVII, of a modified rotary trowelling plate or disc having a segmental gap therein.

In accordance with the invention, a feed hopper or receptacle 2 of the desired size and shape. according to the desired size or capacity of the hopper and the shape of the articles to be molded, is provided. The shape, in plan or cross section, of the hopper or its discharge opening, will 'correspond substantially with that of the mold; for instance, in the molding of rectangular concrete slabs the cross-sectional shape and area of the` hopper or its discharge opening will correspond with the rectangular shape and surface area of the mold. Similarly, in the molding of circular,

`elliptical or other shapes, the cross-sectional shape of the hopper or its discharge opening will conform to the size and shape ofthe surface of the article to be molded.

The concrete mixture which is preferably of a semi-dry or relatively dry consistency-such, for instance, as that referred to in prior United States Letters Patent No. 2,023,381, may be introduced into the feed hopper 2 or the like from a suitable source such as a concrete mixer, the discharge chute of which may be arranged above the open top of the feed hopper which is thus filled to the-desired extent with the semi-dry material. Alternatively, the feed hopper or receptacle may be charged by hand labor, the concrete being shovelled into the hopper through .the side opening 2 in its wall.

thereto. Alternatively, the vibratoryor agitating motion may be imparted directly to the concrete within the feed hopper or the like by arranging a suitable vibrator or agitator within or upon the top of the concrete mixture.

As shown in the drawings'. the vibrary or agitating action may be effectively applied to the material in the hopper 2 by means or rotating cams or lmockers 4 engaging knocker plates 5 and e which are pivoted or hinged as at 1 and form front and -rear inner walls oi' the hopperv chamber.

The cams or knockers 4 which are mounted on cross shafts l supported in bearings 8 and driven by suitable driving gear Il', make contact with the hinged knocker plates E, 8, through openings I2 in outer front and rear walls Il, Il, of the hopper. Suitable means, indicated at I5 may be provided to permit of adjustment of the knocker shaft bearings towards and from each other and consequently adjust the cams or llrnockers in relation to the hinged knocker plates.

The knocker plates 5 and l may be provided with wearing faces I8 to engage the knockers 4 and means. auch as hand levers l1, pivoted on the outer walls I3, I4 of the hopper, and passing through openings I8 therein may be provided to permit of the plates 5 and i being adjusted in relation to the camsor knockers I. The levers may be suitably retained in the desired attitude on their pivots. ABy this means the intensity of the impacts imparted to the knocker plates and the material within the hopper may be varied according to requirements such as the particular consistency or moisture content of the cementitious material employed. Thus, the intensity of Vthe impacts may be adjusted to produce vibrations of relatively slight amplitude in the case of concrete of comparatively wet consistency and to produce more forcible agitation, setting up a jolting or concussional action when the concrete has a lower moisture content.

Whilst it is contained in the feed hopper or chamber, the material is thus subjected to vibration or agitation so that it is converted into the desired pasty or plastic condition as it is shaken down through the hopper. It will thus be evident that when the material reaches the discharge opening 2l at the bottom of the hopper, it hasassumed the desired plastic consistency. so that when it is transferred into the mold 22, it will-at vonce take the shape thereof, and without further agitation, will form a slab or the like 23 which is of substantially uniform homogeneity throughout the area of the mold.

The molds 22 are preferably formed of open topped angle iron frames within which are removable bottom plates or pallet 2l upon which the slabs may be removed from the mold frames after the molding operation. If desired, the bottom plates or pallets 2l may be slightly inclined in relation to the upper edge of the mold, for instance, by providing ledges or distance pieces 2S within the mold frames to support the pallets in an inclined position as seen in Figure 13 so that the molded slabs are of tapered or progressively reduced thickness from end to end.

, Such slabs may be advantageously employed in the construction of roofs and other Vparts of buildings and the like by arranging the thick and thin ends of adjoining slabs in abutting relationship so thatthe thicker ends at the outer faces of the slabs project slightly beyond or overhang the adjoining thinner ends. This facilitates the insertion of jointing or grouting material, such as cement-mortar, between the abutting 0r adjoining edges of the slabs and causesrain water to be shed or pass over the joints from the projecting thick ends onto the thinner end portions of adjoining slabs.

parallel longitudinal bearers or tracks 29 car- Atopposite ends of the bearers ortracks 23 on the machine frame 3| and at opposite sides thereof are short -idle supporting rollers 3l upon which the sidevilanges of the molds may rest whilst they are being fed onto and removed fromA the conveyor 21. s

The aforesaid rotary trowelling action in accordance with the invention may be imparted to the upper surface of the concrete in the mold by means of one or more (preferably two) rotary trowels or discs 36, 31, which are arranged in a substantially horizontal plane immediately above the open topped molds which are fed forwardly beneath thetrowelling disc or discs. The underneath surfaces of these discs are disposed close to and approximately `ush with the upper edges of the-mold frames so as to exert the desired trowelling action upon the cementitious material therein.

One of the rotary trowelling discs 36 may be arranged to rotate against the upper ,surface of the concrete in the molds as the latter move away from the discharge opening 2| at the bottom of the hopper, where a stationary and preferably downwardly and forwardly inclined smoothing plate or straight edge 25 is preferably arranged at the front of the discharge opening 2| as seen in Figure 4.

'I'he trowelling disc 36 is preferably plain or continuous as seen in Figure 3 but if desired it may be provided with one or more gaps or openings 33 of segmental form (see Figures 16 and 1'1) so that as the disc rotates, the rear or trailing edge 39 of this opening removes surplus portions of the concrete from the surface of the slab whilst. at the same time, a slight degree of suction may be set up, causing a quantity of air and moisture to be withdrawn from the concrete through the upper surface of the slab. 'I'his action also causes some of the finer particles of the cementitious material to rise to the surface and ensures an effective compacting and smoothing of the upper face of the slab or the like.

'I'he said rear or trailing edge 39 of the opening 33 in the rotary trowelling disc 36 may be slightly upturned or bevelled so as to facilitate and improve the trowelling action. In addition, the

' underneath surface of the rotary trowel or disc may be slightly rounded or bevelled aroundits periphery.

As previously mentioned, said opening or gap in the rotary trowel or disc 36 may be eliminated so that, as seen in Figure 3 the disc consists of a open topped molds and the second disc 31 may be of-smaller diameter approximately equal to the width` of the molding space between the mold walls. as shown. l

The rotary trowels 36 and 31 may be mounted on the lower ends of vertical shafts 40 which are driven by suitable driving gear 40a.

Thus the first rotary trowel may initially operate upon 4the upper surface of the concrete in I the molds as they leave thevibratory or agitating feed hopper, whilst the second trowelling disc may be used .to subsequently smooth and finish off the upper surface of the `slabs after they have left the rst rotary trowel. The second rotary trowel may, if desired, have its underneath surface disposed slightly above the upper edge of the mold walls and at a slightly higher level than the underneath surface of the second or finishing trowel which thus serves `to com- -press the material at the top of the mold, thereaction by one or more of the trowelling discs or plates, the upper surface of the concrete may be subjected to the action of one or more rollers 4| extending across the machine frame immediately above the molds 22 as seen in Figures y1 and l0. 'I'he material may be thus further compacted and smoothed by the rollers 4| as the slabs are carried beneath the latter. The rollers 4| may be surfaced with rubber or the like and mounted in ball bearings 4|a (Figure 10) carried in stationary brackets 4|b at opposite sides of the machine frame.

In lieu of or in conjunction with, the rollers 4 Il stationary trowelling or smoothing plates 42 (Figure 1l) may be arranged upon the machine frame 3| as to extend diagonally across the upper edges of the vmolds and press against the upper surfaces of the slabs asY the latter are carried forwardly by the conveyor 21. The ends of these plates 42 nearest the feed hopper are preferably slightly upturned as indicated at 43. After the molds with the slabs therein have been removed from the idle supporting rollers 30 at the delivery end ofthe machine, the upper surfaces of the slabs may be subjected to the action of a hand operated roller whereby a roughened ornamental surface pattern may be applied to the plastic or tacky upper face of the slab so as to provide an effective non-slip surface which obviates the risk of persons slipping on a pathway or the like composed of the slabs, particularly in wet weather. 'I'his roughenedv ornamental surface is indicated at 45 in Figure 14.

plain or uninterrupted revolving plate, the underneath surface of which rotates against the upper The marginal portions ofthe slab are preferably smoothed off as indicated at 46 around the roughened surface 45 by means of a hand operated straight edge thus providing a neat finished appearance.

Provision is preferably made for delivering, when so desired, a liquid concrete mixture of a smooth sandy nature and having a relatively rich cement content, onto the palette 24 which forms the bottom of the mold prior to the introduction of the main body of concrete intothe mold from the feed hopper. For this purpose, a. chamber or compartment 41 may be associated. with the feed hopper in such a manner that the liquid mixture which is to form the `smooth underneath surface of the slab, is delivered onto the pallet as the mold enters beneath the feed hopper. This compartment I41 may be formed between the l 3 preferably extends overthe Vside iianges of the* feed hopper. The top of the compartment Il may be fitted with a hinged 11d Il. TBUS. the

liquid surfacing mixture spreads over the pallet 24 before the main body of concrete indicated at 50, passes from the hopper into the mold. By this means. a smooth or special surface may be imparted to the underneath side of the slab by the liquid surfacing mixture in cases where such a surface is required. In this respect, it will be evidentv that the liquid surfacing material in the compartment Il may be colored to produce a corresponding colored surface on the slab. l

According to a modification as illustrated in Figure 15, suitable means such as one or more shear blades I or the like may be arranged at or near the bottom of the hopper 2 so asto cutoff the desired charge of plastic concrete as it leaves the hopper and passes through the discharge opening 2| into the mold, the shear blade or the like being adapted to thus also close the discharge opening, until the next mold is in position to receive another charge of the plastic material. The said shear blade 5| or the like may be of a slidable or rotary nature, for instance, a slidable shear blade may be adapted to reciprocate or move intermittently between the hopper and the mold byrneans of suitable operating gear indicated at 52, or a rotary shear blade may be adapted to pass between the hopper and the mold' and thus cut off the successive charges of plastic concrete and close the bottom of the hopper whilst the next mold is moving into position thereunder. The shear blade may be operated in synchronism with the endless conveyor carrying the molds so that the latter are successively brought beneath the discharge opening of the feed hopper at the proper period to receive the charge.

Preferably, however, the successive charges of plastic concrete are parted or removed from the bulk supply 50 within the feed hopper or receptacle'by moving the molds in close succession beneath the hopper by means of the endless conveyor as aforesaid.

After the molds have been passed beneath the feed hopper or the like and filled with the predetermined charges of plastic concrete which is then subjected to the rotary trowelling action and, if desired, to the action of the rollers and/or stationary trowelling plates as aforesaid, they may be removed from the machine with the slabs therein for curing or lsetting and for any desired finishing treatment such as the aforesaid hand rolling to produce a roughened ornamental surface, prior to the removal of the slabs, or the like from the molds.

The invention ensures a homogeneous, strong and generally improved product and owing to the manner in which the material is vibrated or agitated, during its passage through 'the feed hopper, and is fed from the latter into the molds by the gravitational pressure and agitation of the material in the hopper, after which the material in the molds is preferably subjected to the action of the rotary trowels and if desired, to the subsequent rolling and finishing operations, the manufacture of the articles is greatlyv facilitated and improved and a continuous output may be obtained from the machine with a minimum of hand labour.

Having now described my invention what I claim as new and desire to secure by Letters Patent is:

1. In apparatus for molding slabs from a semif dry or non-plastic cementitious material, a feed hopper having a wall in the form of a' knocker plate hinged at its upper end and hanging freely therefrom, and means for imparting forcible impacts to said knocker plate adjacent the lower edge thereof in order to convertya non-plastic semi-dry mixture contained therein into a plas- Y tic and substantially homogeneous condition by the time it reaches the bottom of the feed hopper.

2. In apparatus for molding concrete slabsand the like, the combination of a feed hopper having a wall in the form of a hinged knocker plate, and means for imparting forcible impacts to said hinged plate. Y

3. In apparatus for molding slabs from a semidry or non-plastic cementitious Cmaterial, a feed hopper having a pair of opposite walls each in the form of a knocker plate hinged at its upper end and hanging freely therefrom, and means for imparting forcible impacts to said knocker plates adjacent the lower edges thereof in order to convert a non-plastic semi-dry mixture'con- 'the other plate in the opposite direction.

5. In apparatus for molding slabs from a semidry or non-plastic cementitious material, a feed hopper having a pair of opposite walls each in the form of a knocker plate hinged at its upper end and hanging freely therefrom, means for imparting forcible impacts to said knocker plates adjacent the lower edges thereof in order to convert a non-plastic semi-dry mixture contained therein into a plastic and substantially homogeneous condition by the time it reaches the bottom of the feed hopper, and means for adjusting the intensity of such impacts, comprising hinged levers associated with said knocker plates to move the latter in relation to the impacting means.

6. In apparatus for molding slabs from a semidry or non-plastic cementitious material, a feed hopper having a wall in the form of a knocker plate hinged at its upper end and hanging freely therefrom, means for imparting forcible impacts to said knocker plate adjacent the lower edge thereof in order to convert a non-plastic semidry mixture contained therein into a plastic and substantially homogeneous condition by the time it reaches the bottom of the feed hopper, and means for conveying a series of open topped molds successively beneath a discharge opening at the bottom of said hopper, said feed hopper having a compartment for a liquid cementitious material, said compartment being located adjacent the rear of the hopper and adapted to deliver the liquid cementitious material into the molds where the latter successively enter beneath the discharge opening at the bottom of the hopper.

7. In apparatus for molding slabs from a semid'ry or non-plastic cementitious material, a feed hopper having a pair of opposite walls each in the form of a knocker plate hinged at its upper end and hanging freely therefrom, means for compartmentbeing positioned to deposit its con' tents into a moldbeneath the same prior to deposition of material from the main compartment.

8. An apparatus of the character described comprising a feed hopper provided with inner and outer walls, an opposed pair oi' said inner walls being formed ashinged knocker plates and knockers for alternately impacting one plate in one direction and the other plate in the opposite direction.

9. An apparatus of the character described comprising a-feed hopper provided with inner and outer walls, an. opposed pair of said inner .walls being formed as hinged knocker plates and knockers for alternately impacting one plate in `one direction and the other plate in the opposite direction, and means for adjusting the intensity of such impacts.

WALTER REGINALD HUMIE.

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