US2500262A - Load transfer device - Google Patents

Description

.March 14, 1950 w. J. PARRQTT LOAD TRANSFER DEVICE Filed May 4, 1945 b m {MW I N vE/vToR I l i, v

Patented Mar. 14, 1950 UNITED STATES PATENT OFFICE 9 Claims.

This invention is a novel and efficient load transfer device particularly adapted for use in expansion and contraction joints of concrete roads and pavements, or the like, to transfer the load from one slab to an adjacent slab by means of a series of dowel bars; and the principal ob ject of the invention is to provide primarily an efiicient yet simple and economical device for supporting, positioning, and holding the dowels in their proper alignment for transferring loads from one concrete slab to an adjacent one through an expansion, or contraction joint.

In the case of expansion joints, other known devices generally support the fixed halves of the dowels in one slab, while the unfixed and unsupported halves in the adjacent slab are painted or greased in order to break the bond with the concrete, small sleeves placed at the greased ends to' provide a clearance usuall equal to the width of the expansion joint. Due to the movement of the unfixed ends of the dowel bars, certain stresses are set up in the concrete adjacent thereto, and usually no provision is made for distributing these stresses through the full width of the pavement. Another object of the invention is to provide a lead transfer device for expansion joints adapted to support a series of sleeves in proper relation and position with respect to the road bed prior to pouring the concrete, the sleeves slidably receiving the dowel bars projecting from one end thereof, and the sleeves having their other ends closed to form expansion chambers for the dowel bars into which the bars may project when the concrete slabs expand.

Another object of my invention is to provide a load transfer device in which the. unfixed halves.

of the dowel bars are supportedand heldin their proper and exact alignment by means, of. the sleeves, the length of which sleeves is equal to approximately one half of the bar, with a clear-- ance at the closed end whichserves as an expansion chamber equal to or greater than the width of the joint. The sleeves in turn are supported from the subgrade by rectangular legs made of.

steel bars. In order to'distribute thestresses set up by the movement of the dowel bars through the entire width of .the concrete pavement, stee] bars arep-laced parallel tothejoint extending the full width of the concrete pavement. These bars also serve to space, hold, and position the sleeves in their proper and exact position, thereby permitting the movement between the concrete pavement and all the unfixed halves of the dowel bars in the same and correct direction. By this paralle] movement, one section of pavement is pre- 55 vented from rising abovethe other adjacent section and the loads are transferred from one to the other uniformly, which prevents the cracking and shaling of the concrete pavement adjacent tothe joint.

Other minor objects of the invention will be hereinafterset forth.

vI will explain the invention with reference to the accompanying drawings which illustrate sev eral practical embodiments thereof, to enable others familiar with the art to adopt and use the same; and will summarize in the claims the novel features of construction, and novel combinationsof parts, for which protection is desired.

In said drawing:

Figure 1 isa perspective view of my novel load transfer device positioned upon the subgrade of a road at an expansion joint prior to pouring the concrete.

Fig. 2 is an enlarged transverse section on the line 2-2, Fig. 1, showing the concrete slabs adjacent the joint.

.Fig. 3 isa transverse section of a modified device for a contraction joint.

Fig, 4 .is a transverse section through the deto .as indicated in Fig. 2 to form a unitary structure, said bars maintaining the legs I in proper spaced relation across the entire width-of theroadbed. BarsZ, 3 may be slightlybowed to correspond with the camber of the finished road.

The lower corners of the legs I are secured to a zigzag bar 4 which is welded in one lower corner of one leg and isdefiected ina'substantially horizontal plane and is welded in the other lower corner of the adjacent leg I, as clearly indicated in- .Fig. 1, thesingle bar 4 dispensing with the necessity of providing a pair of bars corresponding in arrangement to the bars 2, 3 connecting the upper portions of the legs.

The .above arrangement provides a rigid struc" .ture adapted .to seat clearly upon the prepared subgrade prior to pouring theconcrete and is of a length sufficient to extend across the entire width of the finished road .bed.

An important feature of my frame l-4 is its stability and its ability to remain rigid-with,- the subgrade, preventing displacement during" Upon the bars 2, 3 are a series of dowel sleeves Y 5 conveniently formed from lengths of pipe or tubing of desired internal diameter having one end terminating adjacent the bar 2 and theother end closed as at 6a, the sleeves 6 being welded in spaced relation to the bars 2, 3 and disposed transversely of the roadway. Adjacent the closed end to of each sleeve is a depression lib, and entering the outeropen end of each sleeve 6 is a dowel bar I so positioned that its inner end contacts the depressed portion 6b which initially limits the inward movement of the bar in the sleeve. The space between the inner end of the dowel bar I and the closed end 641 of sleeve 6 forms an expansion chamber X into which the end of the dowel bar '1 may enter under expansion of the roadbed, the end of the bar expanding the depressed portion 6b under pressure of roadway expansion to its substantially normal position, and thus entering the said expansion chamber. The depression 6b, however, initially holds each dowel bar I in such position that the expansion chamber, indicated at X (Fig. 2), will be provided in the load transfer device while the concrete is being poured. As the tightfitting sleeves 6 extend over the entire half of the unfixed halves of the dowel bars I, there is no question of the free movement of the bars I.

Welded or otherwise secured to the under sides of the legs I are horizontal clips 8 (Fig. 2) the outer ends of which are adapted to be bent upwardly as at 8a across the outer surface of a sheet of pre-moulded expansion material M to hold same in place opposite the outer ends of the sleeves 5 before the concrete is poured, the expansion material M having holes therein for the passage therethrough of the dowel bars 1. The material M is well known in the art and forms no part of my present invention.

Thus the dowel bars I are held in their proper and correct positions by the metal sleeves E in such a manner as to provide free movement therein of the dowel bars '1 upon expansion of the concrete slabs C and C, the expansion chambers X providing the additional space necessary for recovering the unfixed ends of the dowel bars I when expansion of the concrete slabs C-C' occurs.

By the above arrangement the unfixed halves of the dowel bars 1 are supported and held in their proper and exact alignment by the sleeves 6 which are of a length equal to about half of the bars 1, said sleeves having clearances at their closed ends 6a. forming expansion chambers X which chambers are equal to or greater than the width of the joint itself. The sleeves 6 in turn are supported on the subgrade by the rectangular legs I made of steel bars. In order to distribute the stresses set up by the movement of the dowel bars I through the entire width of the concrete pavement the steel bars 2, 3, 4 are disposed parallel to the joint and extend the full width of the concrete pavement.

[5 portions of the series of legs; a spaced series of These bars 2, 3 also serve to space, hold, and position the sleeves B in their proper and exact positions, thereby permitting the movement between the concrete pavement and all the unfixed halves of the dowel bars I within sleeves 6 in the same direction. By this parallel movement one section of pavement is prevented from rising above the adjacent section, and the loads are transferred from one to the other uniformly, which prevents the cracking and shaling of the concrete pavement adjacent the joint.

The arrangement shown in Figs. 1, 2 thus forms an efiicient load transfer device for expansion joints in the concrete roadway, the concrete CC' being poured to form the surface of the load after the parts shown in Fig. 1 have been properly assembled on the prepared subgrade as hereinbefore explained.

In the case of a contraction joint, no provision is made for expansion of the concrete, but instead, a predetermined plane of weakness is established by inserting a steel plate between two sections of the concrete pavement. This plate may extend through the total depth of the pavement or only through its upper half. Dowel bars, however, are also used for transferring the loads from one section of the concrete pavement to the other. In Fig. 3, one modification is shown in which the device is arranged for a contraction joint rather than an expansion joint. In this modification the legs I and the bars 2, 3. 4 are arranged in the same manner as above described in connection with Figs. 1 and 2. A predetermined plane of weakness is established by use of a plate 9, preferably sheet steel, which is welded to the legs as indicated at 9a (Fig. 3), the plate 9 taking the place of the premoulded expansion material M (Figs. 1-2) and having holes therein for the passage of the dowel bars. In this type of joint the dowel bars 7' are welded directly to the tops of the reinforcing bars 2, 3 of the frame, the sleeves 6 shown in Figs, 1, 2 being omitted. Preferably bars I are formed of round steel, and extend through holes in the plate 9 for a distance equal approximately to the width of the legs I, as clearly indicated in Fig. 3. Thus, in Fig. 3 the dowel bars i are directly welded to the frame bars 2, 3 rather than slidably mounted in sleeves, such as 8 in Figs. 1, 2.

In Fig. 4, another modification of the device for a contraction joint is shown, in which the legs I and the bars 2, 3, i are arranged as in the preceding figures. Also the dowel bars 1" are welded directly to the tops of the bars 2, 3, as in Fig. 3. In this modification, however, a predetermined plane of weakness is established by use of a plate 9' preferably of sheet steel disposed upon the tops of the dowel bars I and having its lower edge welded as at 91) to the tops of the dowel bars. Otherwise, the arrangement shown in Fig. 4 is identical with that shown in Fig. 3.

I do not limit my invention to the exact forms shown in the drawings, for obviousl changes may be made therein within the scope of the claims.

I claim:

1. A load transfer device for expansion joints between adjacent slabs of concrete roadways or the like, comprising a spaced series of parallel vertical legs of substantial rectangular shape; parallel bars secured to the upper corners of the series of legs parallel with each other and to the base of the legs; another bar secured to the lower sleeves secured to the parallel bars and transversely thereto and having open ends in vertical alignment with the inner ends of the legs and having their other ends closed; slidable dowel bars snugly fitted within the respective sleeves with their inner ends spaced from the closed ends of the sleeves and their outer ends adapted to extend beyond the sleeves a distance substantially equal to the width of the legs; and a sheet of expansion material against said vertically aligned portions and secured to the said legs.

2. In a device as set forth in claim 1, said legs comprising bars bent to form open rectangular frames having their opposed ends disposed at the central portions of the tops of the legs.

3. In a device as set forth in claim 1, the sleeves being welded to the parallel bars.

4. A load transfer device for expansion joints between adjacent slabs of concrete roadways or the like, comprising a spaced series of open rectangular parallel legs; a pair of parallel bars extending through said series of legs and secured to the upper corners of the legs parallel to the bases of the legs; a third bar extending through the series of legs and secured to lower corners of the legs; a spaced series of sleeves secured to the pair of parallel bars transversely thereto and having open ends disposed in vertical alignment with the inner ends of the legs and having their other ends closed; slidable dowel bars snugly fitted within the respective sleeves with their inner ends spaced from the closed ends of the sleeves and their outer ends adapted to extend beyond the sleeves a distance substantially equal to the portions within the sleeves; a, sheet of expansion material contacting the inner ends of the legs; and clips secured to the legs below the sheet and having their outer ends upturned across the face of the sheet opposite from the legs.

5. In a device as set forth in claim 4, said legs comprising bars bent to form open rectangular frames having their opposed ends disposed at the central portions of the tops of the legs.

6. In a device as set forth in claim 4, the sleeves being welded to the parallel bars and the clips being welded to the legs.

7. A load transfer device for expansion joints between adjacent slabs of concrete roadways or the like, comprising a spaced series of open rectangular parallel legs; parallel bars secured to the upper portions of the legs parallel to the bases of the legs; another bar secured to the lower portions of the series of legs; a spaced series of sleeves secured upon the tops of the parallel bars transversely thereto and having open ends disposed in vertical alignment with the inner ends of the legs and having their other ends closed; depressed knobs in the walls of the sleeves adjacent their closed ends but spaced therefrom; slidable dowel bars snugly fitted within the respective sleeves with their inner ends contacting said knobs and their outer ends adapted to extend beyond the sleeves a distance substantially equal to the portions within the sleeves; a sheet of expansion material contacting the inner ends of the legs; and clips secured to the legs below the sheet and having their outer ends upturned across the face of the sheet opposite from the legs.

6. In a device as set forth in claim 7, said legs comprising bars bent to form open rectangular frames having their opposed ends disposed at the central portions of the tops of the legs.

9. In a device as set forth in claim 7, the sleeves being welded to the parallel bars and the clips being welded to the legs.

WILLIAM J. PARROTT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 21,996 Oates Jan. 6, 1942 1,752,327 Briody Apr. 1, 1930 1,946,658 Angier Feb. 13, 1934 2,192,571 Bitney Mar. 5, 1940 2,245,972 Friberg June 17, 1941 2,309,767 Heltzel Feb. 2, 1943 2,319,050 Fischer et al. May 11, 1943 2,365,550 Heltzel Dec. 19, 1944

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