US2092106A

US2092106A - Fabrication of composite structural

Info

Publication number: US2092106A
Authority: US
Publication date: 1937-09-07
Anticipated expiration: 1954-09-07

Description

Sept. 7, 1937. E. D. CODDINGTON FABRICATION OF COMPOSITE STRUCTURAL MEMBERS Filed Sept. 3, 1935 2 Sheets-Sheet l Sept. 7, 1937. E. D. CODDINGTON FABRICATION OF COMPOSITE STRUCTURAL MEMBERS Filed Sept. 5, 1935 2 Sheets-Sheet 2 Patented Sept. 7, 1937 UNITED STATES FABRICATION OF COMPOSITE STRUCTURAL MEMBERS Edwin D. Coddington, Milwaukee, Wis., minor to Reynolds Corporation, New York, N. Y., a corporation of Delaware Application September 3, 1935, Serial No. 39.022

' members designed to take the place of lumber in building construction, and the process of fabrieating such members.

In the manufacture of such structural members it is common practice to stuff the imperforate sheet metal tubes or casings with a plastic cementitious filling material. This cementitious filling material, in order to render it sufficiently fluent for penetration into all the corners of the easings (which may assume various cross-sectional shapes) is combined with an excess of water over that required for hardening. Notwithstanding this surplus of water, hardening of the material commences almost immediately after the introduction of water and it has been found by experience very diilicult to avoid adding more water to the mixture and remixing in order to maintain proper plasticity during the filling step. This additional water is unnecessary to promote the hardening action and remixing disturbs the particles of material which have attained intermediate stages of hardness, and by reason of this excess of moisture the resulting product takes a long time to dry. Consequently the product is inferior to that obtained when the volume of water combined with the components of the mixture is such as to avoid over-wetting of the material and when the water is introduced in such a way as to avoid interference with the hardening action after its commencement. The structural units after filling are laid aside for a time sufficient to allow the filler to cure and the hardening action to continue'until the filler becomes transformed into a hard core. and, depending upon the nature of the filler, may extend over several weeks or even months.

Since the excess moisture contained in the filler can evaporate only through the open ends oi. the tube, the curing progresses from the ends inwardly of the tube toward its middle. And, because it requires a longer time for the'moisture adjacent the middle of the tube to effect its escape than that nearer its ends, it sometimes happens that a structural member is prematurely incorporated in a building before the drying has proceeded to completion and before the member possesses sufficient strength to carry the load it is called upon to sustain. Thus, a structural member that may test satisfactorily at points adjacent its ends may conceivably fail at its middle when placed under compression due to lack of homogeneity of the filler. Or, owing to incomplete drying, the flller may not securely retain nails that are driven into it as, for example, in the attachment of lathing to the building framework.

While it has been heretofore proposed to utilize as an ingredient of the filling material hydraulic cement which has the capacity to set in the pres- This curing action proceeds slowly ence of water. this expedient does not wholly avoid the difliculty becausev of the presence of other components of the filler, such as sawdust. which are unfavorably affected by a surplus of moisture.

It is an object of my invention to provide a process for forming composite structural members which overcomes the above objections. According to this process the casing is provided with a multiplicity of perforations, the filling material solidly packed into the casing while in a dry state, and moisture then introduced through the perforations intothe filler so as to supply the necessary water of crystallization to the, same and render it cohesive. The time interval during which the casing is subjected to the moistening operation is carefully regulated so as to avoid over-wetting of the material. The member is laid aside for a short time to complete the curing and hardening of the filler, during which interval excess moisture evaporates from the confined material through the perforations in the casing.

As the filling material, I prefer to employ a substantially dry mixture of gypsum, Portlandcement and sawdust. This material when wetted becomes plastic and, upon crystallization of the gypsum and cement components and drying out of the sawdust, sets into a comparatively hard mass composing the core of the member. Such a mixture is preferable to one containing silica or other components of a gritty nature in that it is more adhesive, by virtue of which fact it clings more tenaciously to nails which may be driven thereinto and consequently offers appreciable frictional resistance to their withdrawaL' In addition, the completed structural members may be sawed to length in substantially the same manner as lumber.

The perforations formed in the casing are comparatively small in size and extend throughout the length of the member. Preferably they are punched so as to present burrs upon the inner surface of the casing which become embedded in the filler and upon hardening of the latter serve to anchor the casing to the core. These perforations thus serve the dual function of permitting moisture to be slowly absorbed by the enclosed body of cementitious material through the walls of the casing, and allow the removal of excess moisture from the material by evaporation. Dehydration of the filler thus takes place at a comparatively uniform and rapid rate, and the member may be safely incorporated in a building structure a relatively short time after its manufacture.

Another object of the invention is to provide a composite structural member having perforations formed in its casing adjacent its middle, and

preferably coextensive with its length, to accomplish the purposes above described.

The improved form of apparatus described in connection with the process of this application forms the subject of my divisional application,

Serial No. 65,481, filed February 24, 1936.

* process herein disclosed;

Figure. 2 is a front elevation of the apparatus for filling tubular casings in the manufacture of structural members of the type illustrated in Fig. 1;

Figure 3 is a side elevation of the apparatus of Fig. 2;

Figure 4 is an enlarged perspective view of the reciprocating rack case for supporting a series of casings during the introduction of filling material thereinto;

Figure 5 illustrates a tub designed for immersion of the structural members;

Figure 6 is a detail view of the agitator baskets to cause flowing of the material from the hop- Figure 7 is a cross-sectional view ofa pair of companion spouts; and

Figure 8 is a detail view of one of the agitator baskets.

In Fig. l is shown one form of composite structural member, suitable for use as a building stud, adapted to-be manufactured by the process of my invention. Such members comprise generally a casing i of light, nail-penetrable sheet metal and a hardened core 2 of cementitious material into which nails may be driven without cracking or crumbling the material. In this form of stud which is more particularly described and claimed in my copending application Serial No. 39,023, the sides 3 of the casing are dished while the top andbottom faces 3a are plane.

In the preliminary stage of manufacture of such structural members, an elongated strip of sheet metal is passed between suitable forming rolls to bend the sheet into the desired crosssectional contour and, in the form of structural member shown in the figure, to unite the overlapped edges of the sheet by a lock seam 3b extending lengthwise of the member. Any suitable mechanism for bending the members to shape may be employed, and since such mechanism is well known in the metal working art, a description of the same is unnecessary. Either before, during or after formation of the casing rows of smallperforations 4 are punched at closely spaced intervals along the sides of the casing adjacent its top and bottom.

The casing Lwhich assumes a tubular shape is adapted to receive a filling material. This filling material, as already stated, is preferably composed of a substantially dry mixture of gypsum, Portland cement and sawdust represented in approximately the proportions, by weight, 55:20:9. This material after moistening solidifies into a relatively hard nailable mass possessing many of the desirable characteristics of wood, such as lightness, nailability, sawability and strength.

The apparatus which I employ for packing the casing with filling material is diagrammatically illustrated in Figs. 2 and 3. This mechanism comprises generally a common hopper 6 into which the filling material is adapted to be in= itially delivered; a

rack case I located below the hopper and designed to support in vertical position a series of tubular sheet metal casings i in such a manner that material 'flowingfout the bottom of the hopper discharges into the upper ends of the casings; a waste collector 8 located below the rack box for recovering spilled material; a feeding mechanism 9 for urging the material from the hopper into the open ends of the casings; and a vibrating mechanism ill for reciprocating the rack case I to solidly packthe material within the casings.

The hopper 6. is supported upon a platform l3 located at the top of a. tower, indicated: generally by the reference numeral ii. The top of the hopper opens through the upper side of the platform and is extended in 'a direction crossewise thereof. The hopper terminates at its bottomin a series of downwardly depending spouts l2 disposed a substantial distance above the ground level. The series of spouts l2 are arranged in closely spacedpairs and maybe of any suitable shape, but desirably corresponding to that shown in Fig. 7. Each pair of companion spouts is designed to feed material into theexpanded crosssectional areas of a casing I located upon opposite sides of its constricted mid-section, and the two companion spouts together assume the general contour of the cross-section of a casing, but beingsmaller in outline. These spouts are adapted to be used in filling all standard sizes and shapes of casings.

A bank of casings i is adapted to be supported in upright position within the rack case 1. This rack case comprises a frame open at its top and composed of vertical side members I! and a horizontal bottom member IE, to which members 1 are attached a back cover I9 and two hinged outwardly opening doors 20 constituting a front cover. A series of vertically-extending partition members 2i are attached to the back cover i9 forming stalls for receiving and supporting a plurality of casings I in upright position within the rack case in alignment with the spouts i2. The thickness of the rack case corresponds approximately to the width of a. casing, so that when the casings are introduced laterally into the rack case and the doors 2!] are closed, the sides of the casings I will be snugly confined between the front and back covers of the rack case. Latches 22 are provided for holding the doors 20 closed. When the casings are assembled in the rack case with the latter in its lowermost position the lowerends of the standard length casings bear upon the bottom member l8, while the upper ends of the casings project above the top of the rack case to a position spaced a slight distance below the spouts l2. When the rack case moves to its upper limit of motion the spouts protrude a short distance within the casings, as indicated in Fig. 6.

The rack case is reciprocabie in a vertical direction and for this purpose there are provided pairs of guide plates 25 upon opposite sides of the rack case rigidly fastened to the tower H and arranged to embrace the side members and slightly overlap the front face of the rack case, as indicated in Fig. 3, but not sufficiently far so as to interfere with the opening and closing of the doors 20. These guide plates insure straightline vertical reciprocation of the rack case.

In order to compact the material introduced into the casings through their upper ends, and to avoid the production of air pockets" in the core. the vibration mechanism I0 is designed to mechanism l0.

impart a succession of sharp vertical impulses or pair of generally horizontally-extending arms 21 each of which is pivoted at one extremity to a shaft 28 supported within bearings 29 which are, in turn. fastened to the top of a concrete pier 30. The outer free ends of the arms are provided with eyes 3| encircling trunnions 32 projecting laterally from the side members ll of the rack case. A horizontal shaft 33 supported in bearings 34 upon the top of the concrete block 30 extends transversely below the arms 21 about midway of their length, and this shaft is rotated by a belt 35 (Fig. 4) extending between

pulleys

36 and 31 keyed respectively to the shaft 33 and a power transmission shaft 33. This power transmission shaft may be driven in any suitable manner, as by a motor 39, and a suitable clutch (not shown) may be provided for operatively disengaging the driving mechanism from shaft 33. Upon the shaft 33 at suitably spaced intervals are fixed a series of cams 43 adapted to bear against the underside of the pairs of arms 21, these cams being formed with 'convolute contours designed, during their rotation, to impart a lift to the rack case followed by a quick drop through a small vertical distance. Thus, when the shaft 33 is rotated at ordinary speed, a succession of vertical impulses is applied to the rack case.

For insuring continuous feeding of material from the hoppers 6 into the casings, the feeding mechanism 9 contemplates the provision of a series of reciprocating rods 42 eachextending vertically downwardly into the hopper 6. Each rod 42 adjacent its lower end splits into two parallel branches 43 (Fig. 6) and fastened upon the bottom of each branch is a fiat sided agitator basket 44 of open frame construction having its sides tapered at an angle corresponding to the inclination of the downwardly converging walls of the spouts l2. One of these baskets is illustrated in Fig. 8. As shown in this figure the open frame of the basket is encircled by wires 44a at spaced distances lengthwise of the basket whichperform a cutting action upon the material when the basket is raised and lowered. Angled rods 42a attached to the vertical rod' 42 and extending to a position adjacent the middle of the hopper, serve to jostle the material above the bottom of the hopper. Thus, upon raising and lowering the plug in rapid succession a series of chopping strokes is produced which tumbles the filling material down into and out through the open end of the spout, overcoming any tendency for the material, which because of possible dampness may be slightly cohesive and non-fluent, to clog. Since each spout of a pair of spouts delivers material to opposite sides of the constricted width of a casing at approximately the same speed, the filling of each casing proceeds rapidly and uniformly.

In order to reciprocate the rods 42, I provide a mechanism somewhat similar to the vibrating That is, a series of horizontal arms 45 are pivotally mounted at one end upon a shaft 46 mounted within a bearing 41 which may be supported upon a table 48 a suitable dis-' tance above the level of the platform i3 so that the arms 45 do not interfere with the delivery of material into the hopper 8. The reciprocating rods 42 are suitably extended vertically upwardly through the eyes of horizontal pins 49 disposed within the hopper, and these rods are united with the free outer ends of the arms 45. These arms are rocked or oscillated through a small are by means of cams 50 keyed to a shaft extending below and transversely of the arms. The shaft Si is mounted in suitable bearings upon the table 48. Shaft Si is driven by a belt 52 trained over a sheave 53 upon this shaft and a pulley 54 keyed to a second shaft which latter is directly driven by a motor 55 through suitable speed reduction mechanism. Thus, by operation of the motor, shaft BI is driven so as to rotate earns 50 which, acting against wear plates upon the lower faces of the arms 45, impart a succession of quick rising and falling movements to the arms. In order to hold the arms in engagement with the wipers, weighted blocks 55 are mounted upon the outer ends of the arms. In those situations where the filling of certain of the casings outruns or precedes the others, individually-operable cranks 4| (Fig. 3) each connected to upright slidable rods 4lb are provided for lifting the arms 45 clear of the cams 50 to arrest the fiow of material from the hopper. When the crank 4| is moved in one direction by an operator stationed on a lower platform l3a the rod 4!!) to which the crank is pivoted is projected upwardly into engagement with one of the arms 45 of the feeding mechanism raising this arm off the cam; while when the crank is released the rod 4lb drops down to out-of-the-way position with respect to this arm. Suitable means may be provided for limiting the extent of movement in opposite directions of the crank and for retaining it in adjusted position.

The bottom of rack case I is formed with cutouts 60 (Fig. 4) lying outside of the area covered by the bottoms of the. casings occupying the case, whereby any small amount of material sifting out of the casings through the perforations 4 during the filling operation fails to the bottom of the rack case and passes out through the clearance afforded by the cut-outs into the collecting bin 8 located below the rack case. In customary practice the lower end of each casing before its assembly in the rack case will be closed by a metal clip or by a plug of plastic cementitious filling material which has been allowed to harden so as to prevent the passage. of filling material out the end of the casing. Following the filllng operation, either before or after the packed casings are removed from the rack case, the upper ends of the casings may be similarly closed by metal clips or plugs of cementitious material to seal the dry filler within the casings. Where the casings to be filled are of non-standard length, it is necessary to provide a support for their lower ends above the bottom 'of the rack case. One such support 56 is shown in Fig. 4, and comprises a flat foot 51 upon which the lower end of a casing is adapted to rest. This foot is attached at its bottom to a screwthreaded shaft 58 freely passing through a plate 59 and retained in vertical adjustment with respect thereto by nuts mounted upon said shaft and engaging the top and bottom of this plate. Plate 59 may be slid horizontally into any pair of a plurality of spaced pairs of slots 59a formed in the sides of the casing stalls, so that by engaging the plate with an appropriate pair of slots and adjusting the screw-threaded shaft of the support, the upper end of a short casing may be disposed in proper relation to the pair of companion spouts l2.

After the casings have been filled the door of the rack case is opened and the structural meates the whole body of quantity so as not to greatly exceed the amount required for complete hydration of the gypsum and cement. This objective I accomplish by virtue of the perforations 4 provided in the casing. After the perforated casings have been packed with material and their ends closed byclips or hardened plugs of cementitious material, they are stacked upon an open frame 64 and the frame is lowered into a tub 65 filled with water, as shown in Fig. 5. The water is introduced into the tub by an'inlet pipe 66 and removed therefrom via an outlet pipe 61 flowing to waste, the flow through these pipes being controlled by suitable valves. The structural members are allowed to remain in the bath for about one=half hour (the time being variable and dependent upon such factors as the number and size of the perforations and the cross-sectionaldimensions of the members) during which time the water slowly passes through the perforations and perthe material without developing a cutting action or without otherwise interfering withthe natural repose of: the material within the casing. The members are then removed from the bath and laid aside for several days to allow excess moisture to evaporate from the filling material. Crystallization takes place gradually and uniformly without disruption of the internal structure of the core, accompanied by a slight swelling to solidly fill out the interior of the casing.

Composite structural members according to past practice have required a relatively long period for curing, since (1) the filler necessarily has contained an excessive amount of moisture so as to render it sufficiently plastic for convenient introduction into the casings, and (2), due to the absence of means for aerating the filler (the latter heretofore having been practically sealed against the atmosphere except at the two open ends of the casing), a protracted period has been required to allow evaporation of excess moisture from the material adjacent the middle of the members. As a consequence, such structural members have often been incorporated in buildings before they have possessed sufficient strength to enable them to withstand the loads, either in compression or sheanfor which they were designed. And even if the member did not completely fail, nevertheless such delayed curing and drying of the members has given rise to other objections. such as the inability of the members to frictlonally retain nails driven thereinto in the attachment of lathing, wall boards or secondary framing members to the members.

According to the present method of fabrication, these objections are eliminated for the reason that the perforations not only provide for the most eifective introduction of liquid into the filling material, but they also contribute to the rapid and uniform abstraction of moisture therefrom, enabling a member to be safely incorporated in a building a short time after its manufacture. Furthermore, while curing of the core may continue after the member is placed'into service,

nevertheless byvirtuc of aeration of the filler-by the perforations 4, complete curing is attained much more speedily than has been possible in the past with composite structural members employ ing imperforate casings.

My invention is not limited to the production of structural members of the form illustrated in Fig. 1 but may be used with any type of composite members in which a hardened core fillsa protective tubular, metal casing.

It will be obvious that variations in the mode of practicing the process described above, and

that various changes in structure anddesign of the mechanism for carrying out the process, as well as in the product obtained therefrom, may be made without departing from the spirit of my invention.

I claim:

1. A process for fabricating composite structural members which comprises incorporating a filler of cementitious material in a dry state within a tubular sheet metal casing having a multiplicity of small perforations in its wall, and introducing a liquid through the perforations into the body of filler, said perforations being sufficiently smal to prevent the escape of any substantial amount of said filler from the casing.

2. A process for fabricating composite structural members which comprises incorporating a filler of cementitious material in a dry state within a tubular casing of light nail-penetrable sheet metal having a multiplicity of small perforations in its wall disposed substantially throughout the length of the casing, and introducing a fluid through the perforations into the body of the filler, said perforations being sumciently small to prevent the escape of any substantial amount of said filler from the casing.

3. A process for fabricating composite structural members which comprises forming a strip of sheet metal into tubular shape, providing the wall thereof with a multiplicity of small perforations extending a substantial, distance lengthwise of the casing, packing the casing with a dry cementitious filler and introducing a liquid through the perforations into the body of the filler, said perforations being sufliciently small to prevent the lar casing of light nail-penetrabie sheet metal,

providing the wall thereof adjacent its midsection with a multiplicity of small perforations, packing the interior of the casing with a dry cementitious filler, and introducing a liquid through the perforations into the body of the filler, said perforations being sufficiently small to prevent the escape of any substantial amount of said filler from the casing.

5. A process for fabricating composite structural members which comprises forming a tubular casing of light nail-pcnetrable sheet metal, providing the wall thereof with a multiplicity of small perforations comparatively widely spaced apart relative to their size, packing the interior of the casing with a dry cementi-tious filler, closing the ends of saidcasing, and immersing said member in a water bath to cause the water to pass through the perforations into the body of the filler.

EDWIN D. CODDINGTON.