US2181623A - Slab joint - Google Patents

Description

S. KLEIN SLAB JOINT Nov. 28, 1939.

e sheets-sheetv 1 Filed May 9, 1936 :jai-'u u u 'ULI Jgl mvENmR. v Jani/J //e//z .ATTORNEYS S. KLEIN SLAB JOINT Nov. 28, 1939.

Filed May 9, 1936 6 Sheets-Sheet 2 ATTORNEYS N0v.28,1939. SKLEW 'l 2,181,623

SLAB JOINT Filed May 9,11936 6 Sheets-Sheet 3 MINI INVENT OR.

ATTORNEYS` Nov. 2s, 1939. s. KLEIN 2,181,623

SLAB JOINT Filed May s, 193s 6 sheets-sheet 4 97 9/ 93 95 ai 93 I ll /3 /4 /5'2 u 77 l l V w l INVENTOR. Sande/Klein S. KLEIN SLAB JOINT Nov. 28, 1939.

File@ May 9, 195e e sheets-'sheet 5 y INVENTOR. azfzzze/ /f/e//z TTORNEYS NOV. 28, 1939. KLEIN c 2,181,623

SLAB J0 INT Filed May 9, 1936 6 Sheets-Sheet 6 INVENTOR. .5a/7706! /2 /6/'1'2 im, @W

ATTORNEYS Patented Nov. 28, 1939 SLAB JOINT Samuel Klein, Chicago, Ill., assignorrto National Road Joint Manufacturing Company, Chicago, Ill., a corporation of Illinois Application May 9, 1936, Serial No. 18,845

22 Claims.

The present invention relates to slab joints, which are more commonly known as expansion and contraction joints. Such joints are provided between slabs of concrete and the like'in the building of concrete roads, floors, runways, artificial lakes or'pools, and numerous other structures made Wholly or partly of concrete or like material upon which destructive effects are produced by changes of temperature and weather conditions.4

An object of the invention is to provide an improved slab joint structure which will effectively allow for many successive'expansions and contractions of monolithic slabs, without 'destruction of or injury to the joint, and which can not be impacted with foreign objects or substances to the extent of destroying the exibility necessary for free expansion and contraction of adjacent slabs.

Another object of the invention is to provide an improved slab joint which effectively precludes entry of water or other substance between and beneath adjacent slabs, where destructive action ordinarily has its inception.

A further object of the invention is to provide a joint form which may be factory assembled at low cost, and s-hipped in the assembled condition to the job upon which it is to be used.

A still further object iscto provide a joint form which may be erected in sections, and eiectively spliced to furnish a continuous structure that will not permit leakage of water or entry of foreign objects between the slabs.

Another object is to provide a novel joint form structure which includes dowel pins or load transfer means, and simple means for positioning and maintaining them in parallelism with a given line or axis.

Another object is to providein a device of the character stated, effective and durable means forconnecting and strengthening adjacent slabs in the region of the joint, to eiectually resist forces which tend to crack, break, and relatively displace the slabs.

Another object of the invention is to provide a new and impro-ved type of flexible seal channel for slab joint structures, and a novel method of fabricating said channel.

The foregoing and other objects are attained by the means described herein and disclosed in` the accompanying drawings, in which:

Fig. 1 is a fragmental perspective` view of a. long dowel pin assembly for eiecting a slab joint in accordance with the invention.

Fig. 2 is a top plan View of an assembly similar to Fig. 1, but showing one of greater length.

Fig. 3 is an enlarged cross-sectional View taken on line 3-3 of Fig. 2, and showing, in addition, a securing stake driven into the sub-grade to hold the assembly in position.

(Ci. sul-1s) Fig. 4 is a fragmental side elevation of a joint form embodying the invention.

Fig. 5 is a top plan view of a short length' .of

seal channel which forms part ofthe joint form.

Fig.'6 is a fragmental plan vie of a joint form spliced to furnish a continuous leak-proof form.

Fig. 7 is a' diagrammatical viewl showing a joint form end, and means associated with the form providing a slab strengthening structure and cooperative load transfer means, the latter com- Fig. 13 is an enlarged cross-sectional view of the Fig. 12 device, taken on line lil- I3 of Fig. 12. Fig. 14 is a cross-sectional view of a Vshort .dowel pin load transfer means, as used in connection -with filler joints of materials other than metal.

Fig.- 15 is a fragmental perspective view of a removable plate which forms part-of the Fig. 14 .construction.

Fig. 16 is a detail perspective view of a premolded ller element that may-be applied to the' joint Iform after formation of adjacent slabs.

Fig. 17 is a fragmental side elevational view of a joint form of modied construction.

Fig. 18 is a cross-sectional View taken on line i8|8 of Fig. 17. Figs. 19, 20, 21, and 22 are views illustrating a series of steps and apparatus employed in a process for the manufacture of seal channels which form part of the present invention.

For purposes of convenience and clarity of un'- derstanding only, and without limitation of the )present invention t0 any particular use, the invention will be described as applied to a concrete roadway comprising adjacent spaced slabs poured during construction of the roadway. AThe use of roadways by heavy trucks and other vehicles operating at high speeds has, in the past several years, presented a number of true structural concrete problems. As is well known, concrete presents problems in various forces, namely, compression, diagonal shear, true shear, tension, and diagonal tension, the vproblem being magnified and rendered increasedly complex d ue to the nature of the present day trafila. The usageof of compressible and shifting subgrade presents a structural cantilever problem, involving in addition to simple vertical shear, the far more critical element of bending, with resultant direct tensions, compressions, and what is most serious in concrete, diagonal tension. One need only examine concrete highways of the past few years, to reach the conclusion thatI the deleterious effects of the forces to which the roadway is subjected, have not been overcome. The effects of the forces above referred naturally have been manifest at the expansion joint, where premature checking and cracking are most likely to occur. Even the use of load transfer elements across the joints, and high strength concrete mixtures, have not solved the problems mentioned, vpartly because of faulty design and placement of the load transfer means and partly because of the lack of appreciation of the magnitude and directions of the forces acting to crack and break the slabs that comprise the roadway. A niostcommon cause of premature breakage and cracking of the concrete along the joint, was attributable to slab connecting means of extensive4 area, imbedded in the adjacent edges of the slabs in such a manner as to. render impossible the proper and suiilcient bonding of the mass above and below the imbedded slab connecting means. Another fault of prior joint constructions resided in the failure to vexclude water and other foreign substances, which invariably promoted upheaval by freezing beneath and between the slabs or, in the case of the admission of dense particles, caused complete closure of theLjoint and precluded normal'expansion of the slabs, resulting in heaving, crumbling or cracking of the concrete at locations near the joints. The elimination of all these faults has been taken into consideration in designing the joint structure of the present invention, so that the region of the slab joints will withstand the injurious effects of fast and heavy traflic, temperature changes, and water conditions, for a period of time corresponding to the life of the rest of the pavement.

With reference to the drawings, it shouldbe noted that the character G indicates the subgradeand that the character L in all the illustrations, indicates the level of poured concrete which constitutes the slabs S.

Figs. 1 to 4 inclusive, illustratev a slab joint structure of the long dowel pin variety, including various improvements over the long dowel pin structures heretofore employed in the construction of concreteroadways. The characters 20 and 2| indicate construction elementsknown as road rails, said rails being employed to establish or define the lateral limits of a slab to be poured. The road rails generally are positioned accurately to not only define the width ofthe slab, but also to establish thethickness oi' the pavement. Under ordinary circumstances, the road rails are parallel to each other and to the axis of the. roadway.

Within the limits er the raus, there is peei-` tioned a joint form, indicated generally by the character 22, whereby adjacent slabs are initially spaced apart a proper distance toallow for natural expansion and contraction o f the slabs.` 'I'he dowels or shear pins 23 are adapted to extend 'site ends of the dowels or shear pins 23.

it insures a free straight-line expansion and contraction of adjacent slabs, without undue strain and wear between the dowel pins and the concrete in which they move when the slabs are set and begin to expand and contract under varying temperatures and water conditions.

The dowel frame referred to may comprise a pair of transverse rigid members 25, which may be in the form of angle irons if desired, said members being preferably of a length approximating'the distance between the road rails 20 and 2|. At measured distances from the ends of the members 25, are fixed a series of dowel sockets 2 6, the spacing of the sockets being such that the sockets of each ofthe transverse elements 25 provide pairs of sockets for reception of the oppo- When the opposite ends of the dowelstor shear pins automatically assumepositions in parallelism with the roadway rails, and since the transverse ele-v positions other than positions of parallelism to ils.

one another and to thel road r Each socket supporting member 25 is provided' with suitable shoes or standards 21 which support the socket supports at a proper elevation above the subgrade, The shoes may be riveted orv otherwise securely fastened to the members 25, as indicated at 28 of Fig. .3. To render the shoes adjustable to the subgrade, and to simplify shipping or crating problems, the rivets 28 may be suiiciently loose to provide'lfor rotation'of the fshoes to substantial parallelism with the vertical plane of the socket support member 25. To provide for initial expansion of the slabs, certain ones of the dowel sockets may be provided' with destructible space thimbles 29 which are so positioned within/the sockets as to assure expansion spaces'30 for the dowels. Thus, by refere ence to Fig. 3; it will be understood that movement of the slabs S toward one another will result in advancing the dowel sockets toward each other, causing the dowelor shear pin 23 to crush the thimble 29 in the rear end of the socket, thereby preventing cramping or endwise compression of the dowels by the irresistible force of expansion of the slabs. The sockets may be flared at their open ends, as indicated at ,31, for easy reception of the dowel ends, and the slots 32 of the sockets, which afford a resilient or yielding connection between the sockets and the dowel ends, are closed by the space thimbles 29 to prevent entry of grout into' the space 30 reserved for the dowel ends upon expansion of the slabs toward one another. The entire dowel assembly may be held in position by means of suitable stakes 33, or the assembly may be suitably wired together to prevent relative shifting of the parts.

`As will be evident, expansion of the adjacent slabs toward one another must not meet with resistance at the jointform member 22. The joint form is accordingly made in the manner disclosed in either of Figs. 3 and 8. The construction illustrated in Fig. 3 will first be described.

The side walls 34 and l5 of the form may be constructed of pressed sheet metal secured together in such a manner as to provide a communicating Joint chamber 3l and seal` channel material, is extracted from elements, and also chamber 31. The seal channel chamber is preferably, though not necessarily, provided with opposed locking beads 38 and 39, which hold in position a continuous seal channel 4I) that extends inwardly past the beads and into the chamber 31. Extended outwardly of the channel, at the top thereof, are the flanges 4I and 42 and the anchor arms 43, the flanges and anchor arms being imbedded in the concrete slabs. Suitable depressions 44'may be provided in the anchor arms to provide-a lockin additionA to the lock provided by each anchor. Before the slabs are poured, a temporary slab separating member 45 isinserted into the seal channel 40, and as disclosed iny Fig. 1, said separating member completely closes the seal chamber across the top and along the ends thereof. After pouring and setting of the concrete slabs, the slab separating member 45, which is preferably of metal or other nonporous strong replaced by apremolded bituminous mastic ller element 46 (Fig. 4) having substantially the same shape as the temporary slab separating member 45. It is to be understood, of course, that the mastic or plastic substance kept in a' fluidl or semi-fluid state on the job, may be poured into the channel 40 and the space between the slabs as a substitute for the premolded mastic element 46, if desired. The premolded element, however, affords a convenient manufactured iiller means for expansion joints of the character described,

and may be used 1n lieu of the metal separating member 45 aforesaid. The continuous seal chanf nel as disclosed in Figs. 1, 2, 3, and 5, preferably is fabricated of copper or other suitable material which will withstand the destructive action of the the repeated distortion to which it is bound to be subjected by the expansion and contraction of the concrete slabs. Further details concerning the flexible seal channel will be treated hereinafter.

The interior of the joint form is required to be waterproof, and the form must be so constructed as to crush readily when the slabs S expand and move toward one another. For this reason, side wall 34 may be provided with a spacer, which may be in the form of a button 45, the crown of which is adapted to abut another button carried by the spaced wall. The button 41 is rendered deformable by providing a third button 48 over it so as to furnish an air space 45 into which the concrete can not enter when poured against the side wall 35 of the joint form.. In order to provide the air space 4S the inner face of the side 35 is provided with an assembly plate 50 which may be spot welded or otherwise fixed to the wall 35, and clinched at its lower end 5I within an enclosing double flange 52 that forms part of the base of the joint form 35. The ange 52 may be spot welded to the lower edge 5| of the construction plate 50, to provide a rigid structure. The free end 53 of ange 52 extends across the joint chamber 3B at the base of the form, and is slidingly received, between a double base flange 54 of the opposite wall 34, thereby to provide a sliding fit of end 53 in base part 54 and allowing for free expansion of the slabs toward one another in the region of the base of the joint. At approximately the location 53, a series of weak spot welds may be resorted to for temporarily binding the element 53 to element 54, thereby keeping the structure assembled during shipment and placement thereof on the job. It will be noted that the substantially horizontal free end 53 of the joint wall 35 provides a seal forexcludthe channel 4B and the ing from the joint chamber 36 any grout or foreign material from the sub-grade. It is of `course evident that water seepage past the seal channel 40 and into the space between the joint form walls, is impossible due to the fact that the seal anges 4I and 42 are imbeddedin the slabs to provide a continuous seal from the bottom of each slab, a, t the sides thereof, upwardly along the sides and across the tops of the slabs.

It is important to observe that the seal flangesA 4I and 42 are not extended into the slab ends for any considerable distance, and the anchor arms are likewise short and considerably spaced apart so as to permit extensive and suicient bonding of the sab material in the space 55 between the arms. It may here be stated that many expansion joint failures are properly attributable to the provision of extensive seal flanges and anchor arms which, in effect, separated the relatively thin concrete portion above the seal flanges, from` the concrete below the flanges. In the present invention, adequate space has been provided 'between the anchor arms t0 permit substantially uninterrupted bonding of vthe concrete above and below the parts of the seal channel that are anchored in the slabs, so A that there is no appreciable dividing structure between the concrete above the seal channel anchorage,lfrom that below the anchorage. The seal flanges accordingly are made as narrow as possible for preventing water seepage into the interior of the joint form, and the anchorages themselves are of minimum area and vextent to avoid separation of each slab into disconnected or unbonded parts. I have found that satisfactory results are obtained by positioning the flanges 4| and 42 at a distance below the upper face L of the slab, approximating three times the width of the flanges. For. example, each of the flanges 4I and 52 is of a one-half inch width, intermediate the anchor arms 43, and are disposed one and one-half inches below the face L of the concrete slab. 'I'he referred to width of the flanges is indicated at W of Fig. 5. The anchor arms 43 are spaced at such a distance from one another, as to have no effect upon the indicated 3-to-1 relationship stated, and they function only as anchoring means for the outermost or free edges of the flanges 4l and 42. The depressions or corrugations t4 are provided in the anchor arms to strengthen the arms and furnish additional anchorage in the concrete.

The openings 24 of the form walls 34 and 35, are flanged inwardly as disclosed in Fig. 3, so as to support a corrugated or collapsible ferrule 56 which forms'a passageway for the dowel and provides a closure or seal between the passageway and the hollow interior of the form. It will be noted that opposite ends of the ferrule fit about the inwardly turned flanges of the dowel openings, and are thereby maintained in place after assembly of the joint form. The ferrules may be of any suitable construction, those illustrated being in the form of cylinders corrugated at several locations between their ends, so that the ferrules may be deformed or collapsed in the manner of accordion pleated devices or bellows structures. It will be noted that the ferrules preclude entry of grout into the hollow interior of the joint form, even though the dowels may not fit tightly therein. 'v space for collapse of the ferrules, the metal surrounding the openings 25 preferably is bulged outwardly as at 51. Other bulges 58 in the side walls of the form, at the sides of the seal chanends of each joint form, so that entry of grout or other foreign substance is effectively preinclude collapsible ferrules.

separate heavy plate 1I, one end.12

,snap action holding means which sleeves 16 effectively seal said openings. channel member III nel 40, permit a maximum movementof the slabs toward'one another without injury to the seal channel. It is to be understood that the bulges 59 indicates a block or plug of rubber or othersealing material which closes any openings that might occur where the seal channel 48 and its component parts meet the base of the joint form. A plug or seal such as 519 is provided at opposite vented.

In instances where it is necessary or desirable to tionship, 60 is employed. 'I'he splicing element may be constructed in various ways, that indicated in Fig. 6 being a plate of rubber, mastic or the like, having substantially vertical edges BI and a horizontal upper edge 62, the meeting points of said edges being curved as at 63 complementarily to the curve o f the seal channel 40 where the channel turns from horizontal to vertical disposition. 'I'he splice member 60 is of such thickness as to fit snugly within the vertical run of the seal channel, and partly about the vcurved portion thereof at 63, so as to dispose the splice joints within 'the confines of the joint forms,'rather than exteriorly thereof. The height f the splicing member 80 preferably is such that a continuous length of preniolded mastic ller may rest upon the upper edge 62 while extending along the horizontal runs of the channel of the spliced joint forms. Joint form splicing means may be constructed also of metalsand such will hereafter be described in connection with Fig. -12 of the drawings.

Fig. 7 is an end view showing diagrammatically a joint form having the side walls 6I and 65 and a base B6 adapted to rest upon the subgrade, the upper portion of the'form carrying" a mastic ller B1 in substantially the same manner as the device of Fig. 3 carries the slab separating member 45. 'I'he form of Fig. '7 is provided with the spacer buttons for the' purpose previously described and the opposed side walls of the form have openings 88 and 69 for reception of a short shear pin or dowel 1U, all of which is most clearly shown in Fig. 8. Inthe modified structureof Figs. 7 and 8, the base of the form includes a of which is clamped within the clinch structure 13 formed at the lower end of the assembly plate 148. The includes the locking beads 14 are substantially the same as, disclosed in Fig. 3. It will be noted, however, that the joint form of Fig. 8 may or may not .The metal surrounding the openings 68 and 69 isnot pressed outwardly in the manner tion. The sides of lthe form are flat in the region of the dowel or pin openings and the large flanges 15 of the pair of shear pin bearings or The place two joint forms 22 in end to end relaas disclosed in Fig. 6, a splice element of the Fig. 3 construcl ymay be extended along the ,f bottom ot the form members and il. In auch y.

' construction the form members 6I and 85 are V preferably curved at the lower outer edges thereof as well as at the upper outer edges thereof. This form of the invention is shown in Figs. 17 and 18. It is to be understood that the opposite ends of the member 40 will overlap or be joined in any suitable manner to provide a continuous member.

'I'he shear pin bearings or sleeves are adapted to be imbedded in the concrete slabs at op'posite sides of the joint, so as to structurally reinforce the adjacent ends of the slabs. One end of the shear pin 10 is fitted tightly into the bore 11 of one of the bearings or sleeves, for example, the one at the left of Fig. 8, while the bearing or sleeve at the right very snugly but slidably receives the opposite end of the dowell or shear pin.k

A convenient mode of `securing the snug or tight t of the dowel ends in the sleeves or bearings, without danger of absolute fixation, is to roughen or knurl the dowels as at 210 along a portion of their length, and preferably at a distance from the dowel ends so that the dowel ends may be started into the sleeves with ease, and thereafter pressed or forced in place. For a better illustration of the knurled or roughened portion, Fig. 14 may be referred to. That end of the shear pin or dowel which is adapted to slide within a bearing or sleeve, which end may be that end indicated by the character 18, may be protected from entry of grout in any suitable manner such as by means of a closure plate 19 at the outer end of the bearing or sleeve or by closing the end at 19 in the forming of the sleeve. This provides an air pocket 180 at one end of dowel 10.

When the Fig. 8 construction is assembled at the factory, the dowel or shear pin andthe pin bearings or sleeves are applied, so that the entire assembly may be placed on the subgrade as shipped from the factory. The parts cannot be disconnected because of the tightness of the fit between `the dowels and the s'leeves. The assembly may be shipped from the factory with the l mastic filler 61 applied, ora slab separating member such as 45 of Fig. 3 may be substituted therefor, said separating member to be removed and replaced with a mastic filler after pouring and setting of the slabs. 'Ihe Fig. 8 assembly may be staked to the subgrade, or otherwise rigidly supported during the pouring of the slabs. The bottom closure plate 1| may be of rust-proof material, so that it will remain in position for excluding entry of solid materials into the hollow interior of the formfor to the space between the slabs, long after the form has rusted away. The

continuous seal channel which holds the filler 61v may be identical with the channel of Figs. 1 to 5 inclusive, and is adapted to extend horizontally across the form and vertically along the vertical side -edges thereof in substantially the manner disclosed in- Fig. 4. The shear pin` bearings o r sleeves 16 are provided withsuitable ribs and bearing faces 80 and 8|, as well as with flanges 82, for effectively keying them in the material of the slabs. referred to as wings or wing bearings having upper and lower faces substantially horizontal in the slabs, to afford substantial resistance to vertical wearing of the sleeves 1l inthe slabs. It will be noted that the dowel of the forms of the present device, is disposed in a plane which substantially evenly divides the thickness of the slabs. It. should be noted also that the dowels support Qta weight of the joint fonn, rather .than the form luprtmg the weight of 'I'he flanges 8| may more properly bev or shear pin in ,all

the dowels, in Figs; 1,-3, 4,and 14. In instances where the structure of Figs. '1, 8 and 11 are provided with dowel bearings of the type disclosed in Figs. 9 and 10, the weight of the joint form is likewise supported by the dowels", the object vof this being to facilitate setting of the joint form at right angles to the subgrade, and to insure a substantial setting for the joint form structure. It will be noted that the bearings or sleeves 83 of Figs. 9 and 10 are similar to the bearing or sleeve shown in Fi'gs. '7 and 8, except for the addition of a shoe 84 which rests on the subgrade, and which may be secured thereto by means of one or more stakes 85. The leg 86 which connects 'the shoe portion to the bearing or sleeve portion may be of any desirable shape, a straight leg being shown in Fig. 9and a curved leg being shown-in Fig. 10. The figures just mentionedv naturally suggest legs of angular or other configuration.

At this point'in the description, it is appropriate to consider various characteristics of the dowels and the dowel sleeves or bearings mentioned in the precedingparagraph. In computing and testing for a determination of a proper length and diameter for the dowels, it was found that extreme length was unnecessary, and that a small diameter of dowel would easily withstand the shear forces that occur between adjacent slabs. The use of a small diameter dowel, however, provided an insumcient bearing in the concrete of the slab, so that loads on the upper face of the slab caused the dowel to shear the concrete in which it was imbedded. To overcome this destructive shearing action, it was determined that suiiicient bearing could be furnished to distribute the load, by making the dowels of a larger diameter than was necessary to take care ofthe vertical shear between slabs, but dowels of such a large diameter were found to be an expensive expedient. Further efforts to solve the problem eventuated in the provision of the disclosed construction comprising dowels of small diameter suitable to take care of the shear between slabs, associated with the larger diameter dowel bearings or sleeves to be embedded in the slabs for increasing the bearing area and thereby distributing the load over substantial bearing Aareas in the slabs. The actual diameter of the bearing or sleeve was held to a minimum by providing the horizontal sturdy wings or bearing eX- tensions indicated at 8|. The enlarged areas of the dowel bearings or sleeves not only provide for effective load distribution, but they prevent breaking down of the bond between the concrete and the bearing or sleeve elements. Instead of the dowels sliding in the concrete, they slide in the bearings or sleeves, upon expansion and contraction of the slabs. f

Attention is now directed to the general combination disclosed in Fig. '1, which exemplifies a complete set up for obviating the destructive ef,- fectsof the various forces referred to in the introduction which follows the description of the 'drawing figures. Besides the dowel or shear pin structure disclosed in detail in Fig. 8, the combination includea pair of wire mesh reinforcement elements 81 ,each of which is in the shape of a long invert-ed channel having supporting legs 98 and 89, and an intermediate horizontal portion 99.

The portion 99 is adapted to be disposed comparatively close to the upper surface of the slab, while the supporting leg |39 rests close -to,an adjacent wall. of the` joint form. This type vof reinforcement is adapted to tie the concrete mass together in a plane well above the middle of the slab, so as to overcome the torsional, bending, and cantilever forces which would occur in the upper region of the slabs in the event of undermining of the subthe mesh reinforcement in the lower portion of the slab. It should be understood, however, that mesh reinforcement in the lower portion of the slabs may be provided for, if desired, bymaking the member 81 in the shape of a tube having four or more sides instead of the three sides indicated by the characters 88, 89 and99. The bearing or sleeve structures disclosed in Figs. 9 and 10 may readily find application to the general combination of`Fig. 7, as will be understood. It should be noted also that reinforcing mesh means having substantially the characteristics of those indicated at 81, are applicable to joint form assemblies as shown in Fig. 1 as well as in other than those specifically disclosed in the present description and illustrations.

Fig. 11 discloses the joint form of Fig. 7, in side elevation, without a'showing of the mesh rein-l forcements 81. It will be noted that Fig. 11 includes a pair f premolded mastic end pieces 9| and 92, each of which has a horizontal leg 93- and a vertical leg 94. The freevend 95 of each horizontal leg is adapted to abut the opposite ends of an intermediate length 96 of premolded mastic supported-within the seal channel 49 of the joint form. r The separation of the mastic filler into end pieces and intermediate sections has several advantages, some of which are a reduction in cost of manufacture, ease in handling and shipping, and the like. A further advantage is that the end mastic piece 93, for example, may be removed to advantage when it is necessary or desirable to Splice two joint forms in'end to end relationship. To effect the splice just mentioned, it is necessary only to remove the end section of premolded mastic filler piece 93, and to replace it with a straight horizontal section 91 of premolded mastic filler carried by the splicing member 98.` The latter may be of the character disclosed in Fig. 6, or it may be of metallic construction as disclosed in Figs. 12 and 13. The side walls 99 and |90 of the'splice member are spaced apart a proper distance to enable them to enter and snugly t within the vertical run |9| of the seal channel 49 of Fig. 11. It will be noted that the splice member itself has a base portion |92 and a channel supporting portion |93 similar to the corresponding -parts of the joint form. The length of the Abase portion |92, however, is somewhat diminished so` as to substantially abut the base portion |93 when the side walls of the splice member are inserted into the seal channel section |9I. Like the joint form itself, the splice member may be provided with a seal channel member .|94 corresponding vto the seal channel member of the joint form. Thus, a pair of joint forms connected by'means of a splice member of the character disclosed in Fig. ll2, will become a continuous or composite joint form of a desired length. It is preferable, though not necessary,rthat the Splice member 98 u ends of the pin are received in the pin bearings l the lower edge thereof.

be provided with the collapsible button arrangement |05, which corresponds to that of Figs. 1, 7 and 8. It is to be understood, further, that the side walls of the joint, as well as those of the splice members, may be provided with spacing means of a type other than the button type.

In Fig. 14 is represented an expansion Joint including load transfer means of novel construction, without the inclusion of metallic joint forms. In this modification, |06 indicates a long sheet of preformed mastic material, rubber, or the like, of a height approximating the thickness of the slabs S, supported `,upona short dowel pin |01. 'I'he |08 and |09 as explained in connection with Figs. 'I and 8. The-pin bearings may be provided with either of the leg and foot members disclosed in Figs. 9 and 10, to support the mastic sheet in a substantially vertical position between the enlarged faces of the flanges and ||2. To impart the necessary rigidity to the mastic sheet before the concrete is poured, a metal platel I3 of a substantial nature, is placed beside the mastic sheet and supported in a substantially vertical position between the flanges ||2 and ||4 of the bearing or sleeve |09. To provide for removal of the metallic plate I3 after the concrete slabs are set, a slot is provided therein extending from approximately the middle of the metallic sheet to countersunk as at H6, to provide a fin ||1 that fits quite accurately between the flanges 2 and 4 to maintain the removable plate substantially at right angles to the axis of the load transfer dowel or pin. Upon removal of the metallic plate i3, the mastic filler remains in position to permit expansion and contraction of the slabs S, While the dowel and dowel bearing elements perform'to maintain thev alignment of the slabs. The space remaining after removal of the plate N3 may be filled with fluid or semi-fluid mastic, if desired.

In Fig. 16 is disclosed an end portion of a premolded hollow joint ller shaped to tthe channel seal of a. joint form, said filler being constructed of rubber or composition material. When constructed of rubber or like' substances, the filler not only performs to preclude entry of water intorthe slab joint, but lit also tends to expel from the joint any foreign particles capable of compacting and solidifying within the* joint. The channels or air spaces may be varied to meet the requirements of the construction work in which the filler or closure is to be employed. The vertiealleg |20 is adapted to extend to the baise of the joint form, as disclosed in Figs. 1, 4, and 11.

AReference is now made to the modification shown-'in Figs. 1'1" and 18i wherein the seal channel 40 extends entirelyv around the joint,

form structure rather than along only' the top and sides thereof Fig. 11, for example. ,When the seal flanges 4| and 42 and their anchor arms 43 are embeddedin adjacent slabs of concrete, there naturally results a completely'enclosed airspace which is definedv by the seal channel. 'I'his air space is permanent, due to the fact that theseal channel is highly resistant to corrosion and the destructive effects of the elements, it being of copper or similarly 4permanent metal. Also, the sealI y channel .expands and contracts laterally Ylike a The walls of the slot are as explained in `connection with form therein to fill the space and interfere with free expansion and contraction of the slabs.

The characters |21 indicate sheets of mastic or bituminous ller, or of rubber, supported within the seal channel as heretofore explained. 'I'he seal channel may be provided with the snapaction locking beads |28 to maintain the channel in position relative to the opposed form walls |20 and |30, all as explained in the description of other forms of the device. In' all forms of the invention, the form walls which support the seal channels are made of inexpensive sheet metal, such as 'iron sheeting or low grade steel. The form walls developed from -this material are intended to render rather temporary service,

namely providing a space between adjacent slabs of concrete and positioning the non-corrosive seal channel 40, the dowels, their bearing or sleeves, and the base plates such as 1|, until such parts are firmly embedded in or anchored relative to the slabs of concrete. Thereafter, the form is expected to rust away or, corrode, leaving intact the seal channel and the load transfer elements.

The seal channel of the Fig. 17 and Fig. 18 device may be made 'in one or more sections welded, brazed or otherwise suitably joined as at the overlap |3|.`V The exact manner of making the channel continuous is, of course, immat/arial, except that theA method of manufacturing or fabricating it is believed to be novel, and the method will hereinafter be disclosed.

The form dis'closed in Figs. 17 and 18 may be supportsherein disclosed. Attention may be directed to Fig. 18 for an excellent disclosure of the knurled or roughened portion 210 of the dowel or shear pin 10.' The several Icharacters |32 of Figs.'1'7 and 18 indicate spacer buttons such as were described in connection -with Figs. 3, 8 and 13, and at |33 is shown a corrugated cylinder or ferrule corresponding to the element 56 of Figs. 3 and'8. In the Fig. 18 modification, the use of thecorrugated cylinder is, not ordinarily required, though it is permissible.

It should be noted that Figs. 17 and 18 disclose an important modification of the Fig. 10 dowel bearing or sleeve member, which consists in the addition of one or more vertical extensions |34 having free linear 4edges |35 adapted'to reach and abut the bulges |30 or other substantial projecprecluding rotation of the bearings or sleeves may,./

ofcourse, be of 4one design or another, but in the preferred form, such rotation-precluding means should not penetrate the form wall and thereby'` allow for possible entry of grout. By providing cooperativemeans as stated, for precluding rotation of the dowel bearings or supports relative to the form walls, a rigid and sturdy assembly is made possible by the mere forcing of the right- 1 hand sleeve 83 onto the corresponding end of the dowel, until the knurled portion 210 snugly enters the sleeve. 'Ihe abutments at |35+|36 thereupon will be engaged, to prevent rotating of the sleeves, while at' the same time the ange or plate portion 31 of each sleeve will flatly abut the form and prevent grout from entering be-l tween the form walls through the dowel aperture,

in the absence o f a cylinder such as |33. As will be readily understood, a single abutment such as |35 on each dowelbearing support member,

shape that is'merely punched and shaped in an ordinary manner. The sealing channel referred to throughout this description is indicated generally by the character ,40, it being unnecessary to again explain the function and nature of 'the sealing flanges and anchor portions thereof. In the manufacture of the sealing channel (Figs. 19, 20, 21 and 22), a strip |40 of metal of proper width and length to t a. joint form, is fed to a press and cutting die mechanism for the purpose of forming the extending arms 43 thereof as illustratedinrigia msmuchofthetreatmentf of a strip may be formed by ordinary means, which may be either rolling dies or reciprocating press elements, and if depressions such as 44 ofl Fig. 5 are to be made in the extending arms, such can be accomplished in the same operation. As the next step of the process, the strip of Fig.A 19 is subjected to a simple pressing. operation which imparts thereto the formation disclosed by Fig. 20, wherein the characters |4| and |42 indicate the locking beads cf the seal channel. The pressing operation last mentionedis applied to only an intermediate portion of the strip, leaving a foot or two of the ends in the formation disclosed by Fig. 19. This intermediate portion thereupon is subjected to pressing dies such as |43 and |44 of Fig. 21, whereby the strip, excepting the ends thereof, is given its final cross-sectional configuration as seen in Fig. 3. The ends of the strip, it should be noted, are still in the Fig. 19 condition. These ends are then subjected to a special treatment whereby they are pressed to form'the vertical channels and curved to fit a joint form end, all as disclosed in Figs. 4,- 6 and 11. 'I'he curving of the strip end involves not only a press operation, but also a simultaneous stretching' operation upon the end undergoing pressing. To accomplish this, the strip end is placed lengthwise between a convex die |45 and a concave die |46, said dies having complementary tongue and groove elements |41 and |48 for pressing the channel groove into the strip end. The upper die has one or more pressure blocks or plungers |49 which engageand hold the strip while it is being curved and channeled, the eiect of such engagement and holdingbeing to stretch tlrev strip end longitudinally while it is being pressed into channel formation. For example, the strip end of Fig. 19 is rst bent transversely to lfit between the die parts |45 and |46. As the die part |46 descends, the tongue and groove elements |41 and |48 thereof begin to channel the strip end, but at substantially the same time, the spring plungers or pressure blocks |49 are pressing tightly against the tongue with the meterial of the strip interposed, so'that further downward movement of die part |46 must proceed while the blocks or plungers arrest downward feeding of the strip towardA the apex'of the die, The further downward advancement of die part |46 causes the plungers to more tightly hold the material of the strip while the plungers pivot outwardly about their mounting pin's |50. As is evident from the disclosure of Fig. 22, the plunger works in a sleeve( |5| and said sleeve is pivoted at |50 so as to be capable o f movement through the recess |52 in the die part. 'I'he pressure spring is shown at |53. The holdingaction of the plungers or pressure blocks results in a stretching of the metal of the'channel strip in the region of the base thereof, and Vthe effect of the stretching is such as to prevent crinkling and crystallization of the metal which forms the base of the channel, while the tongue and groove elements press the curvature into the strip. The stretching force is regulated so as to elongate the channel strip to the extent of prventing compression of the structure ofthe metal at the inlside of the bend Vor curve, so that the metal at that location will be of substantially the same thickness as the metal of the channel alongv the straight portions thereof. By reason of this manner of treatment, the metal of the channel is rendered quite ductile and free of initial crystallization, with the result that repeated transverse expansion and contraction of the channel at the curved portion thereof is made possible without danger of early breaking or cracking.

After the stretching and bending operation just described, the channel strip may be rolled or otherwise treated to form locking beads along the curve, if desired. It should be understood that other methods of curving and stretching the channel member may be capable of operating upon the channel member after formation of the bead |25, but whatever may lbe the specific nature o f the process or apparatus involved,-I claim as my invention the curving and stretching of a channel member, either simultaneously or alternately, for the purpose of rendering the curved channel member capable of withstanding a much greater number of lateral expanding and contracting forces than could be withstood by a curved channel member when not treated in accordance with the invention. The use of copper or similar metal forV the channel member is considered preferable, due to its ductility, its resistance to deterioration, and the ease with which it may be worked in the formation of the channel member. It is conceivable, of course, that various alloys having the characteristic mentioned, may furnish the same advantagesas'the metal mentioned, and that the curvature and stretching above explained may be produced by the use of a roller die.

The copper sealing channel in practice, is in. `tended to flex as may be required due to temperature changes and consequent expansion and contraction of the slabs. By forming the curved parts of the channel 40 at the ends of the forms in accordance with the method explained herein,

it is possible to`assure-numerous contractions,

expansions, extensions or other movements, before crystallization renders the seal ineffective. In fact, tests have shown that these curved parts of the seal channel will function as'long or as often as do the intermediate portions of the channel. A seal of the character disclosed herein will easily function for the estimated life of a modern concrete roadway,'namely, thirty years, before failure of or destruction ofthe Seal. Tests establishing these facts have been conducted in accredited testing laboratories. Y

The` devices shown herein are preferably assembled at a factory and are shipped to the job as complete units, one each of which is positioned at each place at which an expansion joint the -recesses along is desired. By so 'assembling and positioning the expansion joints 'as-separate. units, it is possible to obviate the errorsthat commonly occur asa result of carelessness and `incompetence of unskilled labor that is now vrelied on/to position expansion forms heretofore used' and built up on the job.

Preferably the beads Hl and |42 do not extend around the corners or curves ofthe seal channel 40 because of slight manufacturing variancesv side walls each having upper and lower edges' and an end, said ends being curved where they meet the-upper edges of the walls, and a continuous integral ductile sheet metal seal channel depressed between the sidewalls, following the curve and extending along the upper edges `and ending adjacent to the lower edges at the ends of the walls.

2. A slab joint form comprisingfa pair of spaced side walls each having upper and lower. edgesand an end, said ends being curved where they meet the upper edges of the walls, and a continuous integral ductile sheet metal seal channel following the curve and extending along the upper edges and ending adjacent to the lower edges at the ends of the walls, the seal channel being wider than the space between the walls and having a substantial disposed between the walls, and cooperative means on the seal channel and the walls for effecting a snap-action connection therebetween.

3. In a slab joint structure, the combination of a plurality of joint forms each of which comprises spaced walls and has an end, the forms being disposed with an end of one form adjacent the end of the next form whereby to extend the forms in substantial longitudinal align'- ment, a seal channel connecting the edges of the walls and extending into the space between the walls whereby to provide a recess in the end` of each form, and asplicing memberhaving opposed edges conforming in shape and si'ze to the recesses in the ends of the forms and fitted within the recesses of the forms to provide a sealed connection between the ends of the forms. v

4. In a slab joint structure, the combination of a plurality of aligned joint forms each of which comprises spaced walls and has an end and an upper edge, continuousintegral ductile sheet metal channel means along the upper edge and along the end of each form and extending into the space between said walls whereby, to provide an outwardly opening recess, a form splicing member having opposed edges fitted within the ends of the forms, and a joint filler strip on the splicing member extended beyond the opposed edges of the splicing member and into the recesses of the upper portion of the channel of each form.

5. A slab joint structure comprising in combination, a form comprising perforated side walls spaced apartto provide a chamber, a load transfer element extended through the perforations of the side walls and having an end thereof/projecting beyond. the plane of one of the side walls and having at its other end a substantial bearportion of said excess material ing surface, and a' bearing member having a substantialbearing surface and comprising a depending supporting leg and slidably surrounding 'the projectingv end of the load transfer element,

vthe members having the substantial bearing sur' 5 y faces having end faces abutting the side walls -'beyond which the bearing members project, to close the chamber to entry of grout in the region of. the flange, the load transfer element portion disposed between said side walls having suiilcient l0 strength for meeting the maximum shear load that may be imposed on said joint structure and the horizontal width of said substantial bearing surfaces disposed at the ends o'f the loady transfer element being much greater than the 15 width of said rst mentioned portion of said load transfer element.v 6. The combination with a pair of concrete slabs having adjacent ends .thereof spaced to provide an expansion joint, of ,a plurality of load 'a transferJ elements, each comprising a bar member of a `diameter suflicient to sustain itspropor-4 tional share of shear action at such joint, said bar members being parallel with one another and with the surfaces of the slabs, said bar members extending throughl the space between the slabs and each having one end disposed within the body line of one slab and its other end disposed within the body line of the other slab, a plurality of bearing members' embedded in said slabs, a bear- 30 ing member being provided for each end of each bar member, vthe bearing members associated with each bar being .adapted to accommodate the bar member toA relative expansion and contraction of the said members and slabs, and each bearing kmember having an enlarged transverse bearing surtface adequate to transfer load from the con- I cre e to its associated bar member without destroying the bearing between the concrete and the bearing -memben and reinforcement emo bedded in the concrete and disposed 'adjacent the top face-of the concrete and thatsurface of the concrete at and along the expansion joint, the reinforcement at the top of the concrete ex' tending to a substantial distance from the -expansion joint wherebyV to incorporate within the K slabs, at thejoints thereof, the ability to with-` stand the tendency toward bending or cantilever action of the? concerete slabs incident to th movement of aload from one slab, over the eX- pansion jointonto the adjacent slab.

7. A slab'joint structure comprising in combination, a form comprising perforated side walls spaced apart to provide a chamber, the perforai tions in said side walls beingarranged in aligned pairs, a load transfer pin extended through each pair of the perforations of the side walls and having'oppositeends, bearing means on said-opposite ends each comprising a bearing sleeve having a substantial bearing surface to be embeddedin' the I slab, said sleeves each including an extending4 le`g reaching to thesubgrade so as to supportA the form in an upright position, and cooperative means on the form'and sleeves for preoluding rotation of the sleeves-` about the axes of the pins, the load transfer pin having suilicient strength for meeting maximum shearload to ,be directed l. against said'joint structure and the substantial bearing surfaces on the bearing means being of much greater width than the width of the transfer pin. v l l 8. In combination, a slab joint form and means for supporting said form in an upright position upon a slab bed, a load transfer means associated with the form to connect slabs located at opposite sides of the form, and means for overcoming the destructive effects of cantilever type forces directed upon one of the slabs, comprising an inverted channel shaped reinforcing element having a pair of legs and an intermediate leg connecting portion, one of the legs being molded in said one slab in close proximity to the form, and said intermediate connecting portion being molded in the same slab close to the upper sur face of the slab. v

, 9. A factory assembled slab joint structure comprising in combination, a form comprising upright metal Walls spaced to provide an expansion chamber, said walls being perforated transversely and including joint ller supporting means along their upper edges, a load transfer means comprising ashear pin supported in the perforations and having opposite ends extending from-the side walls, a pair of pin bearing elements each including a face abutting one of the form walls and a sleeve portion surrounding an end of said shear pin, atleast one of said sleeves having a frictionaly movable mounting upon its associated shear pin end of sulcient security to hold the shear pin in position ag nst ordinary manual handling incident to shipme t and placement ofthe joint form, said frictional relationship being inadequateto prevent relative movement of the parts incident to changes in weather conditions. A

10. A factory assembled slab joint structure comprising in combination, a form comprising upright metal walls spaced to provide anV expansion chamber, said walls being perforated transversely and including joint filler supporting means lalong their upper edges, 'a load transfer means comprising a shear` pin supported in the perforations and having opposite ends extending from the side walls, a pair of pin bearing elements each including a face abutting one of the 1 form walls and a 'sleeve portion surrounding an end of said shear pin, at least one of said sleeves having a frictionally movable mounting upon its associated shear pin end of sufficient security to hold the shear pin in position against ordinary manual handling incident to shipment and placement of thel joint'form, said frictional relationship being inadequate to prevent relative movement of the parts incident to changes in weather conditions, and means including portions of the form walls, for closing the bottom of the expansion chamber, the load transfer pin having sufcient size and strength for meeting maximum shear load that may be directed against said joint structure and the bearing elements being of much greater width than the load transfer pin. i

1l. A factory assembled slab joint sturcture comprising in combination, a form comprising upright metal walls spaced to provide an expansion chamber, said walls being perforated transversely and including joint filler supporting means along their upper edges, a load transfer means comprising a shear pin supported in the perforatons and having opposite ends extending from the side walls, a pair of pin bearing elements each including a face abutting one of the form walls and a sleeve portion surrounding an end of said shear pin, at least one of said sleeves having a frictionally movable mounting upon its associated shear pin endof sufficient security to hold the shear pin in'position against ordinary manual'handlingincdent to shipment and placement of the joint form,vsaid frictional relationship being inadequate to prevent relative movemi 0f the Pans nels-19M l@ @langes in restes? conditions, means including portions of the form walls, for closing the bottom of the expansion pansion chamber. 5 n

12. A slab joint form comprising a pair of spaced side walls each having upper and lower edges, and ends connecting the said upper and lower edges, the upper edges and ends being curved at their juncture, said walls being each of a generally rectangular formexcept for the curved upper corners thereof, and a continuous integral seal channel of`c0ppper or other noncorresive sheet metal, following the form of said upper, end and curved edges of side walls, said seal channel having a depending central portion extending into the space between said side walls and having flanges extending laterally beyond and resting upon the upper, end and curved kedges of the side walls.

13. A slab joint form comprising a pair of spaced side wals each having upper and lower spaced side walls each having upper end lower edges and an end, said ends being curved where they meet the upper edges of the walls, and a continuous integral seal, channel following the curve and extending alongvthe upper edges and l ending adjacentl to the lower edges at the ends of the walls, said seal channel comprising laterally extending flanges projecting outwardly beyond the side walls.

l5. A slab joint form comprising a pair of .spaced side walls each having upper and lower edges and an end, said ends being curved where they meet the upper edges of the walls, and a continuous integral seal channel following the curve and extending along the upper edges and end adjacent to the lower edges at the ends of the walls, said seal channel comprising laterally extending flanges projecting outwardly beyond the side walls, said seal channel also comprising a central corrugated portion extending longitudinally of the Aseal channel and projecting into the space between the sidewalls.

16. The combination with a pair of concerete slabs having adjacent ends thereof spaced to Provide an'expansion joint, of a plurality of load transfer elements each comprising a bar member of a diameter suicient to sustain its proportional share of shear action at such joint, said bar members being parallel with one another and with the surfaces of the slabs, said bar members extending through the space between the slabsl and each having one end disposed within the body line of one'slab and its other end disposed within the body line of the other slab, a plurality of bearing members embedded in said slabs, a bearing member being provided for each end of each bar member, the bearing members associated with each bar being adapted to accommodate the bar member to relative expansion and-contraction of the said members and slabs, and each bearing member Vhaving an enlarged transverse bearing suI ace adequate to transfer lPQ- .flom the concrete tants associated bar member without destroying `the bearing between the concrete and the bearing member, and reinforcement embedded in the concrete and disposed adjacent the top face of the concrete, the reinforcement at the top of the concrete extending a substantial distance from the expansion joint whereby to withstand the tendency toward bending or cantilever action of the concrete slabs incident to the movement of a load from one slab, over the expansion joint onto the adjacent slab.

17. In combination, a slab joint form and means for supporting said form in an upright position upon a slab bed, a load transfer means' associated with the form to connect slabs located at opposite sides of the form, and means for overcoming the destructiveeffects of cantilever type forces directed upon one of the slabs, comprising a reinforcing element having a leg molded in one slab in close proximity to the form and having a portion extending a substantial distance longitudinally of the slab and 4being molded in glei) same slab close to the upper surface of the 18. The combination with a pair of concrete slabs, of a combined slab spacing and joint providing means comprising a slab joint form, means disposed at the inside of the curve, which method for supporting said form in an upright position upon a bed for the slabs and between the pair 'of concrete slabs,a load transfer means associated with the form to connect the pair of concrete slabs, said transfer means comprising dowel pins extending through the form and being oi' a cross-section adequate to withstand the approximate maximum shear forces to be directed upon theslabs incident to movement of ltractionally supported loads-from one of said slabs to theother of said slabs and bearing sleeves within the body lines o'f the concrete slabs and each of said sleeves receiving an end of one of the' dowel pins, the dowel pins being adapted to move longitudinally relative to the sleeves, the bearing sleeves being of overall transverse proportions substantially larger than the cross-sectional dimension of the dowel pins whereby to have an effective bearing vsurface of adequate size to distribute the shear load di- .rected upon the dowel pins, to the concrete without crushing the bond betweenthe sleeves and the concrete slabs, and means for overcoming the destructive effect of cantilever type forces directed upon one of the slabs and comprising a reinforcing element embedded lin such concrete slab, close to the surface of the slab and,

extending a substantial distance from said Jointl form longitudinally of the slab.

19. The combination with a pair of concrete slabs, of a'combined slab spacing and joint providing means comprising a slab joint form, means for supporting said form in an upright position upon a bed for the slabs and between the pair of concrete slabs, a load transfer means associated with the form to connect the pair of concrete slabs, said transfer means comprising dowel `pins extending through the form and being of a cross-section adequate to withstand the approximate maximum shear forces to be directed upon y the slabs incident. to movement of tractionally supported loads from one of said slabs to the other of said slabs and bearing sleeves within the pins, to the concrete without lcrushing the bond `l0 between the sleeves and the concrete slabs, means for overcoming the destructive eifect'of cantilever type forces directed upon one of the slabs and comprising a reinforcing element embedded in such concrete slab, close to the surface of the l5 slab and extending a substantial distance from said joint form longitudinally ofthe slab, and an expansible element resistant seal extending transversely of the forni and having its opposite lateral edges anchored in the concrete slabs.

20. The method of forming a at elongated strip of ductile metal into a continuous strip having sections at right angle to one another, each of U-shape cross section and connected by an in-` termediate curvedfsection. of similar cross see- 2,5

tion and having the base of the U-shape portion comprises the steps of bending a s'trip of ductile metal into channel formation, and curving the channel while stretching it lengthwise to prehaving sections atright angle to one another, 35

each of U-shape cross section and connected by an intermediate curved section of similar cross section and havingthe base of the U-shape portion disposed at the inside of the curve, which method comprises the steps of treating a flat strip 40 of soft non-rusting metal to form a straight channel intermediate its ends, leaving the ends of the strip in a substantially flat condition, and thereafter treating said ends to bend them into Acurved channel formation while at the same time stretching said ends sufliciently yto preclude crinkling and avoid densification of/the metal at the curved portions thereof, the channels at the curved portions meeting the channel of the in- -terme'diate portion. 50 22. A`slab joint form comprising a pair of.,

spaced vertical side wallsreach having upper, lower and end `edges, saidedges being substanstially aligned at every place transversely of said pair of walls, said wall edges being curved at the upper corners thereof, and an elongated continuous integral ductile sheet metal seal coextensive with the topand end edges of the side walls and having its longitudinal central portion of generally U-shaped cross section at every o point longitudinally thereofV and comprising lat-l, erally extending iianges extending from said cen-` tral portion thereof, the said U-shaped portion being disposed between the side walls and the laterally extending flanges being supported by the adjacent edges of the side walls and extended beyond said side walls for embedment in a plastic mass disposed on opposite sides of said form.

v SAMUEL KLEIN.

CERTIFICATE OF CORRECTION. Paterit No. 2,181,625. November 2g, 1959.

SAMUEL KLEIN.

It is hereby certified that error appears in the printed specification OT the above numbered. patent requiring correction as follows: Page 9,f1rst column, lino 25, claim 9, for "frictionaly" read frictionally; and second column, line 15-111, claimlZ, fox` non-corrosive read non-Gorros ive; line 22, claim 15, for "wals" read walls; line 35, claim lh, for "end read and; and-that the said Letters Patent, should be roadwith this correction therein that the seme may conform to the record of the case in the Patent Office.

Signed. and sealed this 15th day of February, A. D. 19110.

Henry Van Arsdale, (Seal) Acting Commissioner of Patents.

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