US2358328A

US2358328A - Joint

Info

Publication number: US2358328A
Application number: US313128A
Authority: US
Inventors: John N Heltzel
Original assignee: Individual
Current assignee: Individual
Priority date: 1940-01-09
Filing date: 1940-01-09
Publication date: 1944-09-19
Anticipated expiration: 1961-09-19

Description

Sept. 19, 1944.

J. N. HELTZEL JOINT Filed Jan. 9, 1940 2 sheets-shea 1 'lll/l j sept.- 19, 1944. J. N. HELTZEL 2,358,328

JOINT Filed Jan. 9, 1940 2 Sheets-Sheet 2 v n., f, a

Patented Sept. 19, 1944 yUMTED STATES PATENT oFFica JOINT a John N. Heltzel, Warren, Ohio Application January 9, 1940,'serial1v0. 313,128

(o1. :i4-1s) 5 Claims.

This invention relates to improvements in joints and joint installing apparatus for concrete roads, floors, walls, revetments, and other structures constructed of plastic setting material. The present application is a continuation in part of my copending application Serial No. 708,155, filed January 24, 1934.

Modern traflic conditions on highways have necessitated an increased use of load transfer members bridging joints, either longitudinal or transverse, between the concrete slabs from which such highways are principally constructed. The problem is not solved by the mere addition of load transfer dowels, such as commonly employed. for the shrinkage of plastic concrete when drying sets up a frictional 'drag on the imbedded dowel bars, with the consequent breaking of the concrete at points remote from the joints between the slabs. It ha-s been found, also, that where dowel bars alone are depended upon, there is an inevitable warping of the concrete slabs which tends to bend the dowel bars. This bending prevents restoration of the slabs to their initial condition on the subgrade and in addition, there is a constant breaking away of concrete or falling off of the material at the faces of the concrete slabs in the areas surrounding and adjacent to the dowel bars.

An object of the present invention is to provide improved means for producing joints in concrete roads and the like, utilizing dowel means in which friction with respect to the surrounding concrete is reduced to a minimum by a novel structure of dowel and bearing therefor.

Another object is to provide, in such joints, means to eliminate tension in the concrete itself and to conne such tension directly to the dowel means constituting load transfer elements extending between the respective slabs.

Another object is to provide an improved dowel bar construction -and installation therefor, in

- which the dowel assembly is provided with stress reducing means extending appreciably into the body of the surrounding concrete in the respective slabs between which a joint is formed.

A further object. is to provide a dowel assembly having means for automatically positioning the dowel members at right angles with respect to the joint forming member with' which the dowel means is associated in producing a joint.

A still further object is toprovide in a dowel assembly and in a road joint installation, means for transferringvertical load strain to the dowel means by the employment of shear plates associated with the dowels.

Still another object is to provide insuch constructions, means for automatically eecting relative shift between cooperating dowel members associated with spaced concrete slabs in the formation of a joint as the green concrete shrinks in the process of drying out, thereby compensating for the shrinkage and relieving the slabs from frictional strains.

Other objects will become apparent from the description.

In the accompanying drawings:

Figure l is a perspective view of a shear plate and dowel construction, and illustrating the use of plural dowel elements in connection with socket means carried by shear plates.

Figure 2 is substantially a fragmentary vertical section through a dowel bar housing of the type employed in the installation shown in Figure 1.

Figure 3 is a perspective view of another embodiment of joint construction and illustrating the use of shear plates of different relative sizes associated with dowel means and stress reducing elements connected with marginal reinforcing means for supporting the joint assembly on a subgrade during pouring oi the concrete.

Figure 4 is a vertical section through a joint, illustrating a further embodiment of shear plate and dowel construction in which the dowel socket is provided with means for expanding the A-shear plates in opposite directions to compensate for shrinking of concrete while it is drying out.

Figure 5 is a perspective view of still another type of joint installation embodying an alternative construction of shear plate and integral dowel means and socket therefor.

Figure 6 is a vertical 'section through a joint illustrating a different type of shear plate and dowel assembly in which the dowel is floated upon anti-friction bearing means housed within the dowel receiving socket.

Figure '7 is a perspective view illustrating a further modification of the dowel bearing'arrangement generally disclosed in Figure 6, and detailing a different type of dowel housing and anti-friction support therefor.

plates, stress reducing elements. etc., as -well as' force to 'insure an expanding separation of the shear plates carrying the dowel and the dowel socket during the pouring of the concrete forming the slabs with which they are associated. It has been found that concrete shrinks considerably in dryingV out and the contraction resulting, if resisted by the frictional binding engagement against immovable doweling means, very often causesa rupture in the concrete at 19.' points remote from the joint. In order to comever a particular illustration or reference ismade to a particular type of joint, the structure disclosed may equally as well be employed in connection with other types of joint installation as above noted.

Figure 1 illustrates an application of the invention which involves shear plates having plural dowel and socket means associated therewith. In this form each shear plate 236 and 291 has rigidly secured thereto a rearwardly projecting dowel socket indicated at 299 and 299 respectively. The plate 293 is formed with an integral laterally and inwardly directed base flange 293 which seats upon the subgrade and which is upwardly and outwardly reverted upon itself as at 29| to provide a relatively xed base which extends up into the material of the concrete slab with which the plate is associated. The dowel socket 233 is disposed slightly above the base portion 29| and is' located adjacent one side edge of the plate. At its opposite side edge, and substantially in the horizontal plane of the dowel socket, theplate 239 has rigidly secured thereto an inwardly projecting stress reducing member 292 having an upwardly and rearwardly inclined extension adapted to be embedded in the body of the concrete slab and to transmit strains remote from the joint directly to the shear plate. 'I'he member 292 is passed through the plate to provide a dowel portion, not shown on. account of the angle of the perspective, which extends transversely across the joint space into slidable housing engagement within the dowel socket 299 carried by the opposite shear plate 291. This latter shear plate is' likewise provided with a stress reducing member 293 having an angled extension similar to that of the member 292, and

wardly pressed to provide a conforming socket.

means 299 which is arranged to receive the ribbing on the opposite plate. The shear plates at their upper edges are provided with rearwardly directed top nanges which are corrugated or recessed as at 291 to provide for an anchorage of the flanges in theV body of the concrete.

Figure 2 illustratesa detail of the dowel and socket assembly used in the embodiment shown 'mineure 1. mtmscasetnesoekeasuenasm,

is welded to the-rear face of the associated shear plate 233 and'receives the dowel 394 in slidable engagement. Spring tension means, here shown as a coiledexpansion spring 299,-is disposed in the socket between the socket end and the end of the dowel bar. The'resilientmeans is normally underV tension constantly urging the dowel bar outwardly of the socket with just sumcient pensate for this and to keep the shear plates in tight binding engagement against the plastic concrete while the concrete is drying out, a spring means 293 is provided-which insures that the shear plates shall -be gently but firmly forced up against the green concrete under tension throughout the period in which it is drying. When the slabs expand and move toward one another the dowel is, of course, projected further into the socketv and this movement will then be resisted by compression of the Spring. Providing a cushioning eilect between the dowel and its socket. v

Figure 3 illustrates an embodiment of the invention in which the shear plates are of diil'erent relative sizes and in which only one assembly of dowel and socket is utilized. In this form the larger shear plate 33| is formed withan intumed base flange 332 which seats upon the subgrade. A similar flange 333 is formed at the upper edge of the plate and extends back into the body of its associated concrete slab somewhat below the top surface thereof, it being apertured for anchorage engagement with the concrete.

The shear plate V33| carries on its inner face a v rigidly attached dowel socket member 334 disposed at the upper portion of the plate and having at its inner end an integral downwardly and rearwardly inclined stress reducing extension y 339. The lower end of the extension 335 is connected with an angle member 336 seated on the subgrade in spaced arrangement inwardly from the shear plate 33| and extending longitudinally of the joint. Preferably the connection is made by extending the ends of the member 335 through an aperture provided for the purpose in the upstanding flange of the angle member; however, any suitable form of connection may be employed. At one side the dowel socket member 334 is welded or otherwise rigidly connected to a companion stress reducing extension 331 that is rigidly secured at its outer end to the inner face of the shear plate and which is upwardly and rearwardly inclined at its inner end portion to provide reinforcement for the concrete slab and to transmit distant strain directly to the shear plate. therethrough a marginal reinforcing bar 339, the bar being anchored in its receiving slot by means of the wedge pins 339. The reinforcing bar 333 and its connection may be dispensed with as it is not necessary to the operative organization of the joint. In this embodiment the dowel socket contains a resilientmember 349, preferably a rubber pad, although it may be an expansion spring, which bears against the inner end of the dowel bar 34| to provide a cushioning element as well as a meansfor normally urging the bar outwardly with respect to the socket.

The dowel bar 34| is rigidly mounted in a supporting member 342 and rigidly secured on the inner face of the shear plate 343 which is disposed on the opposite side of the joint strip 344. The plate 343 is'relatively smaller than the plate 33| and is supported in position above The extension 331 is provided to receive` outward from its central portion.

the subgrade by means of the extension 342 which corresponds in shape and function to the mem-ber 334 associated with the shear plate 33|. The extension 342 is likewise connected at its lower end to al companion angle member 338 seated on the subgrade and extending longitudi-V nally of the joint. Also, the shear plate 343 has rigidly secured to its inner face a stress reducina member 345 which corresponds in shape and function to the stress reducing member 331 and which may likewise be associated with the marginal reinforcing bar 338 secured by the Wedge pin 339 in the slot provided for the purpose within the extension. In this embodiment the two shear plates are held firmly against opposite faces of the joint strip during pouring of the concrete by means of a tie wire 326 passed through the upper edge portion of the joint strip and tied into anchorage apertures provided in the respective top flanges 341 and 333 of the shear plates. After the concrete has set the tie wires 326 maybe clipped and the Joint finished in the usual manner. If desired the plates may be connected by employing connector clips.

In the embodiment illustratedA in Figure 4 the shear plate 391 embedded in the face of the concrete slab at one side of the joint strip 398 carries a dowel bar 399 whose inner end is bifurcated.

to provide stress reducing extensions 400 and whose outer end is provided with an enlarged head 40| slidably received in a dowel socket member 402 that is welded to the inner face of the opposite shear plate 403. The dowel bar 399 is passed through the shear plate 391 and is welded thereto to provide a rigid connection between the parts. In this form of the invention the dowel bar has a slidable bearing through an aperture provided therefor in the shear plate 403 which carries the dowel socket, and the enlarged head 40| bears against a. member 404 formed of resilient material, here shown as a block of rubber, but which may be an expansion spring or other suitable resilient means, disposed within the dowel socket. As the concrete sections move toward one another in expansion the thrust of the dowel bar within its socket is-resisted by the compressible resilient member 404 which provides a cushioning means. In the setting of the concrete from which the slabs are formed and while the material 'is yet green, the resilient member 404 exlerts an expanding tension against the dowel bar head 40| which forces the dowel bar outwardly with respect to its socket tending to separate the shear plate 391 from the shear plate 403. This separating force is sufficient tomaintain the two shear plates firmly engaged against the concrete so that the plates move back in accordance with the shrinking of the concrete and there will be no pulling away of the material from around the plates. It is to be understood that in this embodiment, while the concrete is being poured, a suitable tie means is provided to hold the shear plates firmly against the opposite faces of the joint strip', and this means is removed after the concrete has setsufiiciently to permit same.

In the form shown in Figure 5 the shear plate 421 has an integral dowel 438 placed laterally The shear plate 421 is embedded in the base of its associated concrete section and has its top flange 429 rearwardly directed somewhat below the top face of the concrete and apertured as at 430 for anchoring engagement with the concrete. The

. Both flanges are apertured in vertical alignmentto receive the inturned terminal portions of the to the top flange and seats upon the sub-grade.

arms of av substantially U-shaped reinforcing member 432- which is disposed vertically in embedded relation within the concrete of the associated slab and rearwardly ofthe shear plates.

' The bottom arm of the reinforcing member is maintained in position upon the subgrade lby means of a stake. or other suitable securing means 433. The opposite shear lplate 434 is provided with similar top and bottom flanges and is likewise equipped with one of the reinforcing members 432 also secured by a stake 433 and directed oppositely tothe member associated with the shear plate 421. These reinforcing members act to maintain the shear plates properly positioned upon the subgrade as well as serving as reinforcing members for the body of the concrete slabs in which they are disposed. The shear plate 434 is laterally pressed at its central portion to provide an integral socket 435 which receives the dowel 428 of the opposite plate in slidable engagement for transferring vertical loads across the joint from one slab to the other. The socket also carries a, resilient member 436 such as a block of rubber or a spring or the like which provides a cushion resisting the movement of the dowel into its socket and which at the same time normally tensions the dowel to movement out of its socket. By means of the resilient member 431i the shear plates, during the drying period of the concrete, are gently but firmly urged apart so that they will remain in full bearing contact against the concrete faces of the slabs in which they are embedded and vwill move in correspondence with the'shrinkage of the concrete. Y

In the type of joint shown in Figure 6 the dowel plate 413 has welded thereto a dowel bar 414 which is passed centrally therethrough and which, in rear of the shear plate is bifurcated to provide arms 415 which extend into the material of the associated concrete slab to act as stress reducing elements and reinforcing means. The dowel bar passes freely through an aperture provided therefor in the opposite shear plate 416; the aperture being larger in diameter than is the dowel bar so that a sufficientI clearance exists to permit free. movement of the dowel bal'. The plate 418 is provided on itsrear face with a flxedly connected dowelA socket 411 which receives the end of the dow'el bar and which contains between the laterally enlarged head 418 at the end of the dowel bar and the end of the socket a. coiled ,expansion spring 419 which is backed by a pad 480 of rubber or rubber resilient material. The springer the combined resilient means acting against the enlarged head. 418 of the dowel bar tends to force the bar outwardly of the socket and' thus to communicate to the shear plates 413 and 414 the lateral expanding action tending to separate the two. As the concrete of their associated slabs driesl it shrinks and by virtue of the arrangement of the resilient means within the dowel socket the shear plates 4 will be given a positive movement in the direction bottom aange 43| is lnturned ln parallel relation 76 of shrinkage of the concrete so that they will be kept firmly forced against the faces of the sections in which they are embedded. In this form of the invention the end of the dowel bar which is housed within the socket is supported on antifriction rollers 48| which are disposed between position.

being necessarily larger than the diameter of the head 418, it follows that an annular flange 482 will exist on the shear plate around the dowel bar where it passes through the shear plate 416.

The flange serves to retain the lubricant within the socket member and further acts as a stop or raceway which retains the roller members 48| ln In this type of joint the Joint space may be sealed at its bottom by a suitable plastic setting sealing medium 488 and, where no joint strip is employed, it may be sealed at the top by a metal insert 484 of V-shaped form which is forced between the shear plates and which supports a body of moldable material 488 at the dividing line between the top faces of the joint slabs. l

Figure 7 illustrates a further embodiment of the principle disclosed in Figure 6. In the form shown in Figure 7 the shear plate 488 at one side of the Joint has a substantially rectangular cross section dowel bar 481 -passed centrally therethrough and welded to the rear face of the plate. 'I'he dowel bar 481 at its rear end has suitably secured thereto a rearwardly extending reinforcing element in the form of a substantially U- shaped bar 488 which is connected to the upper edge of the dowel bar and, if desired, a second and similar bar 489 is rigidly secured to its under face. These bars extend well back into the body of the concrete forming the slab with which they are associated to serve as stress reducing elements as well as reinforcing means. The dowel bar extends transversely across the joint space and through an enlarged aperture provided therefor in the opposite shear plate 498, which plate has extending from its rear face a dowel socket member 49| which may also have secured there to reinforcing members 492 and 493 which are generally similar to the

members

488 and 489 at the opposite side of the joint. Atits inner end the dowel.socket.49| is closed by a vertical plate 494 which supports internally thereof a resilient member 495, here shown as a rubber block or pad, which bears against an enlarged head 496 on the inner end of the dowel bar within the socket. In this embodiment of the invention the portion of the dowel bar which is housed within the dowel socket is transversely grooved at itstop and bottom faces to provide a socket 491 which seats upper and lower arcuaterocker members 498 that function as anti-friction bearings for the ilxed dowel bar within the socket members. These rockers are provided with arcuate outer surfaces which bear against the top and bottom portions of the dowel socket so that they oscillate on horizontal axes in accordance with the relative movement of the dowel bar and its socket.

Figure 8 illustrates the position of the parts shown in Figure 7 when the concrete sections have expanded to approximately their maximum position with the dowel bar housed to its fartht extent within the socket. It will be noted that the rockers 498 are tilted on their axes.

1. In a joint for concrete sections, load transfer means bridging the joint and extending into the sections in xed relation to one and slidable freely at all times in the other, a load bearing -plate in each section face and supporting said load transferV means, a housing for said load transfer means fixed to the bearing plate in the section iin which said transfer means is slidable, and resilient means in said housing engaging the load transfer means under tension normally urging the transfer means outwardly of the housing.

2. In a joint for concrete sections, a load bearing plate in each section face, dowel means extending through and between said plates into the sections, said dowel means being ilxedly embedded in one section and fixed to the bearing plate in that section and'being slidable freely at all time in the other bearing plate and section, said other bearing plate having dowel socket means xed thereto, and resilient means tensioned between a portion of said socket and the dowel and normally urging separating movement between the bearing plates.

3. In a joint for concrete sections,` shear plates embedded in the opposed section faces, a dowel member rigidly secured to one plate and slidable freely at all times through an aperture provided in the other, a socket secured on the inner face of said other plate and housing the free end portion of said dowel member entirely out of contact therewith, anti-friction bearings in said socket and supporting the end portion of the dowel member, and resilient means between a portion of said socket and the dowel member and normally urging the dowel outwardly of the socket.

4. In a joint for concrete sections, shear plates embedded in the opposed section faces, a dowel member rigidly secured to one plate and freely slidable through an aperture provided in the other, a socket on said other plate and housing the free end of the dowel member, and movable anti-friction bearings between said dowel member and the socket and supporting the dowel member therein.

5. In a joint for concrete sections, shear plates embedded in the opposed section faces, a dowel member rigidly secured to one plate and freely slidable through an aperture provided in the other, a socket fixed on said other plate and housing the free end of said dowel member entirely out of engagement therewith, said free end of the dowel member having opposed arcuate recesses therein, rocker members having rounded ends bearing in said recesses, and said rocker members having enlarged arcuate heads bearing on the socket walls, the rocker members comprising the sole support of the dowel member the socket.

JOHN N. HELTZEL.