US2476243A - Expansion pocket for dowel bars - Google Patents

Description

July 12, 1949. F.o. HELTZiEL v 2,473,243

v EXPANSION POCKET FOR DOWEL BARS Filed Nov. 29,- 1945 F" .4 66 24 AME? 12 Fig.5

awe/whom Francis QHeli' eZ wk; I? l 06, 12 mvmww Patented July 12, 1949 UNITED STATES PATENT OFFICE 4 Claims.

The invention relates to expansion and contraction joints for concrete paving construction, and more particularly to an expansion pocket for dowel bars for sustaining in alignment separately formed adjacent section: of the paving.

Highways and similar paving, especially when constructed of concrete, are formed in sections or slabs, and it is common practice to leave a space between the adjacent edges of the slabs, which space is filled with a compressible material which will permit expansion of the concrete slabs and consequent compressing of the packing material without resulting injury to the slabs.

It is customary to join these slabs so that they will not become displaced and permit one slab to sink below the surface of another and thus cause an uneven road surface, and the usual method is to place transload dowel bars at frequent intervals which extend about half into one slab and half into an abutting slab.

When the pavement becomes heated the slabs will expand and upon cooling the slabs will contract. This working of the slabs sometimes places considerable shearing strain on the dowel bars making it necessary that the ends of the dowel bars must not be restricted against movement. It is thus necessary that the ends of the dowel bars not be restricted against movement, or at least one end of each dowelbar be free to move into the adjoining slab as expansion occurs.

For this reason it is common practice to place an expansion cap upon one end of each dowel bar, the type of expansion cap most commonly used consisting of a thin metal cylinder with closed end and one or more indentations or stops. It frequently occurs that too tight a fit is provided causing the cylinder to expand and destroying the same as an expansion cap.

It also happens that the cylinder is driven onto the dowel bar beyond the stop thereby causing seepage of cement and loss of expansion.

The object of the present improvement is to provide an expansion pocket for the dowel bars which are provided for the necessary expansion and contraction of adjacent slabs of cement and to permit room for the ends of the dowel bars to move into and out of the expansion pocket during the relative movement of the concrete slab.

Another object is to provide an expansion pocket which will overcome the difficulties and disadvantages of present practice.

A further object is to provide a sealed dowel expansion pocket which prevents the seepage of cement into the pocket.

A still further object of the invention is to provide an expansion pocket comprising a box of sheet metal or the like adapted to fit upon one end of the dowel bar and having a shaped insert, formed of sheet metal or the like, normally acting as a stop to position the box relative to the dowel bar but capable of being pushed into the box when expansion occurs.

Still another object is to provide such an expansion pocket in which the shaped insert is provided with ears or wings at its side edges normally engaged in grooves or channels at the side edges of the box, the dowel bar being of I-shape so that when the shaped insert is pushed into the pocket by expansion the ears or wings thereof will be forced along the web of the dowel.

The above objects, together with others which will be apparent from the drawing and following description or which may be later referred to, may be attained by constructing the improved expansion pocket in the manner hereinafter described in detail and illustrated in the accompanying drawing, in which;

Figure 1 is a transverse section through an expansion joint between two adjacent slabs of concrete, showing a dowel bar located therethrough and provided with the improved expansion pocket;

Fig. 2 a detached perspective view of the improved expansion pocket;

Fig. 3 a front end elevation of the expansion pocket;

Fig. 4 a fragmentary, sectional view showing one end portion of a dowel bar with the improved expansion pocket mounted thereon;

Fig. 5 a section taken as on the line 55, Fig. 4; and,

Fig. 6 a view similar to Fig. 5 showing the manner in which the shaped insert is pushed into the expansion pocket when expansion takes place.

The dowel bar, indicated generally at ID, to which the improved expansion pocket is applied, is preferably of substantially I-shape in cross section, as shown in my prior Patent No. 2,309,- 767, issued February 2, 1943, and comprises the upper and lower flanges ll, connected by the web 12.

Each dowel bar may be supported upon a chair which may be formed from a single length of strap iron, wire or the like and may comprise the horizontal base portion l3, the upright forward leg M formed at the forward end of the base portion, the upright rear leg I5 formed at the rear end of the base portion and the forwardly disposed horizontal portion [6 at the upper end of the rear leg, a pin or stake l1 being driven through suitable apertures in the chair and into the road foundation or base to anchor the chair in position. Tie rods 18 may be welded or otherwise attached to the chair for connecting several similar chairs of each joint together.

The chair supports one end portion of the dowel bar It within the end portion of a concrete slab it), the other end portion of the dowel extending into the adjacent edge portion of an abutting concrete slab 20, the dowel bar being located through suitable openings in the removable joint strip 2| and the premolded joint 22, which may be formed of any usual and well known compression material, such as an asphalt or bitumen composition, as in ordinary practice.

The improved expansion pocket to which the invention pertains is mounted upon the end portion of the dowel bar which is located within the concrete slab 2D and may comprise a sheetmetal rectangular box shaped member indicated generally at 23. The side walls of this box-shaped member are equi-distantly recessed from the open end thereof, so that the upper and lower portions of the box are continued above and below said recesses as upper and lower channel portions 24, upper and lower walls respectively of which are preferably .of double thickness as best shown in Figs. 2, 3 and 4, adapted to slidably receive the upper and lower flange portion ll of the :dowel bar, and preferably having the flared outer ends 25. v

The primary object for forming these upper and lower walls of double thickness-is to provide flexibility .to accommodate variations in the size of the dowel bars, commonly known as mill-tolerance, and at the same time provide a perfect seal against grout seepage.

The side walls of the box 23 at the ends of said recesses are provided with the grooved or channel flanges 26 which receive the-ears or wings 21 formed upon the shaped collapsible closure insert plate 28, of sheet metal or similar material.

As shown quite clearly in Figs. 1, 2 and 4 to 6 of the drawings, the channel portions 24 extend a considerable distance beyond the insert plate 28 at the-open end of the box.

When the expansion pocket is placed upon the end of thedowel bar, as shown in Figs. 1', 4 and 5, it contacts the end of the dowel bar acting as a stop to position the expansion pocket thereon.

In practice the structure is set up in the manner illustrated in Fig. 1 and above described and with the parts of the structure in this position, the concrete forming the slabs 1 9 and 20 is poured, completely enclosing the structure in the roadway as shown in Fig. 1. As the material of the slabs sets, the entire structure will become bonded to the slabs except the end of the dowel bar located in the slab 2B which will be free to slide in the expansion pocket 23.

Upon expansion of the slabs the free end of the dowel bar will be forced into the box portion of the expansion pocket pushing the shaped insert 28 therein and bending the ears or wings 2! as they are forced out of the grooves or channels 26, these ears or wings being accommodated upon opposite ends of the web portion 12 of the dowel bar as shown in Fig. 6.

Upon further expansion the dowel bar will move further into the box of the expansion pocket and upon contraction of the slabs the end'of the dowel bar-will of course move out of said box.

From the above it will be seen that a simple, inexpensive and eflicient expansion pocketis provided which overcomes the objections and disadvantages of present practice and will not permit seepage of cement and consequent loss of expansion, and that the shaped insert provides a perfeet seal and a fool-proof stop for perfect expansion.

I claim:

1. An expansion pocket for use in connection with a dowel bar that is positioned between ex pansible members, said expansion pocket comprising a rectangular box-shaped member open at its inner end, the side walls thereof being equidistantly recessed from :the open end thereof so that the upper and lower portions of the box above and below said recesses form channels for slidably receiving the adjacent end portion of the and a collapsible closure plate having ears detachably connected to said flanges to normally close the open ended the box and provide a stop for contact with the end of the dowel bar.

2. An expansion pocket for use in connection with a dowel bar that is positioned between expansible "members, .said expansion pocket :comprising a rectangular box-shaped member of oblong cross section open at its inner end, the side walls thereof being \equi-distantly recessed from the open end thereof so that the upper and lower portions of the boxabove and below said recesses form channels for slidably'receiving the adjacent end portion of the dowel bar, flanges at the ends of said recesses and .a collapsible closure plate havingears detachably connected to said flanges to normally close :the open end of the box and provide a stop for contact with the end of the dowel bar.

.3. An expansion pocket for use in connection with a dowel bar that is positioned between expansible members, said expansion pocket comprising a rectangular box-shaped member open at its inner end, the side walls thereof being equidistantly recessed from the open end thereof so that the upper and lower portions of the box above and below said recesses form channels for slidably receiving the adjacentend portion of the dowel bar, the ends of said channels being flared, flanges at the ends of said recesses and a collapsibleclosure plate having ears detachably con nected to said flanges to normally close the open end of the :box and provide a stop for contact with the end of the dowel bar.

4. An expansion pocket for use in connection with a dowel bar that is positioned between expansible members, said expansion pocket comprising a rectangular box-shaped'member formed of sheet material and open at its inner end, the side walls thereof being equi-distantly recessed from the open end thereof, so that the upper and lower portions of the box above and below said recesses form channels for slidably receiving the adjacent end portion of the dowel bar, the sheet material being lapped at the top and bottom of the box to provide a double thickness extending the entire length of the box, flanges at the ends of said recesses and a collapsible closure plate having ears detachably connected to said flanges to normally close the open end of the box and provide a stop for contact with the end of the dowel bar.

FRANCIS O. HELTZEL.

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

2,149,396 Klein Mar. 7, 1939 2,181,623 Klein NOV. 28, 1939 2,255,599 Olmsted Sept. 9, 1941 2,410,099 Olmsted et a1. Oct. 29, 1946

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