US3881833A

US3881833A - Load transfer assembly

Info

Publication number: US3881833A
Application number: US482331A
Authority: US
Inventors: Richard G Mcmullen
Original assignee: Acme Highway Products Corp
Current assignee: Acme Highway Products Corp
Priority date: 1974-06-24
Filing date: 1974-06-24
Publication date: 1975-05-06
Anticipated expiration: 1992-05-06
Also published as: CA1032002A

Abstract

A plurality of dowels positioned by a knockdown frame structure having a plurality of opposed supporting elements gripping the dowels adjacent opposite ends thereof for ease of handling prior to installation, with alternate elements releasing the dowels adjacent one end thereof automatically upon installation for movement relative to the wire frame structure upon expansion and contraction of the surrounding pavement.

Description

1 .1 United States Patent 111] 3,a1,33 McMullen May 6, 11975 LOAD TRANSFER ASSEMBLY 2,486,527 11 1949 l-lillberg 404/56 x 2,608,142 8/1952 Jacobson 404/60 [75] Inventor: Richard G. McMullen, Fayettevllle, 2,858,749 11/1958 Crone 404/63 3,104,600 9/1963 White 52/688 [73] Assignee: Acme Highway Products Corporation, Buffalo, NY. Primary ExaminerNile C. Byers, Jr. [22] Filed June 24 1974 Attorney, Agent, or Firm-Christel & Bean [21] Appl. No.: 482,331 [57] ABSTRACT [52] Us Cl 404/60 52/688 A plurality of dowels positioned by a knockdown [51] i 11/14 frame structure having a plurality of opposed support- [58] Field 63 56 ing elements gripping the dowels adjacent opposite 6 ends thereof for ease of handling prior to installation, with alternate elements releasing the dowels adjacent [56] References Cited one end thereof automatically upon installation for movement relative to the wire frame structure upon UNITED STATES PATENTS expansion and contraction of the surrounding pave- 1,870,487 8/1932 Bitney 52/688 m m, 1,871,809 8/1932 Lampert 52/688 2,150,982 3/1939 McFarland 404/62 10 Claims, 7 Drawing Figures L70 1 I s 36 I W ,2 k 1 1 L. as l I i w 3 PATENTEDHAY 8875 3881.888

SHEET 1: OF 3 .KTEHTED HAY 81% SHEEI 30F 3 LOAD TRANSFER ASSEMBLY BACKGROUND OF THE INVENTION This invention relates generally to a load transfer assembly for pavement joints.

In the construction of highways and the like formed of concrete or other paving materials, it is customary to form transversely extending joints at regular intervals therealong to accommodate thermal expansion and contraction. Generally, such joints consist of transverse slots formed after the concrete or other material has been poured and at least partially set by sawing through the top surface of the pavement down to a predetermined depth. Subsequently, transverse cracks develop in the concrete pavement and migrate downwardly from the slots, separating the pavement into sections.

Dowels often are employed to connect and maintain adjacent pavement sections in alignment during contraction and expansion and to prevent relative vertical displacement therebetween under loading so as to maintain a coplanar roadway surface. Typically they are supported by wire basket or other assemblies in laterally spaced relation above the subgrade prior to the pavement pouring operation. Then concrete is poured and hardens with the dowels embedded therein, the subsequently formed slot being disposed above and along the row of laterally spaced dowel rod.

Dowels conventionally have been formed of steel and welded to a supporting wire framework, with the resulting disadvantage that assembly of the dowels and wire framework usually must be accomplished where the welding can most conveniently be carried out, usually away from the point of use, thereby requiring transport and handling of the relatively bulky assemblies. Also, steel dowels are susceptible to the corrosive action of liquids, deicing salt solutions and other deleterious agents which accumulate in the contraction grooves and often leak past defective fillers used to seal such grooves.

Attempts made to solve the corrosion problem by coating the steel rods with a varnish or a primer, or by covering such rods with a corrosion-resistant protective sheathing or jacket, have not completely solved the problem because portions of the jacket are destroyed in order to effect a weldment between the dowel and its supporting wire frame, exposing the dowel to the corrosive action of the deleterious agents leaking past the groove filler.

SUMMARY OF THE INVENTION Accordingly, it is a primary object of the present invention to provide an improved load transfer assembly which can be delivered to the site in knockdown condition and quickly and easily assembled on the job without welding and by relatively inexperienced personnel.

It is also an object of this invention to provide the foregoing in a load transfer assembly which is not destructive of coated metal dowels and will effectively support non-metallic dowels.

Another object of this invention is to provide a novel wire frame structure effectively supporting and maintaining the assembled dowels in position without welding prior to the concrete pouring operation and releasing the dowels at one end for relative movement automatically upon installation.

In one aspect thereof, the load transfer assembly of this invention is characterized by the provision of a wire frame structure comprising a plurality of dowel gripping portions and a plurality of dowel guide portions axially aligned therewith and also gripping the dowels prior to final installation, the guide portions releasing the dowels and thereafter providing sliding support therefor, upon installation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view of one form. of load transfer assembly of this invention partly in elevation and partly in section taken about on line l-1 of FIG. 2, showing the same as it appears in use, the pavement and joint being outlined in phantom;

FIG. 2 is a top plan view thereof, parts being broken away for convenience in illustration;

FIG. 3 is a vertical sectional view thereof on an enlarged scale, taken about on line 3-3 of FIG. 1, parts being broken away for convenience in illustration;

FIG. 4 is a fragmentary perspective view of a dowel gripping support element; and

FIG. 5 is a fragmentary perspective view of a dowel guide support element, both elements forming part of a load transfer assembly of this invention, the dowel being shown in phantom;

FIG. 6 is a view similar to FIG. 1 but showing the dowel gripping and guide elements prior to anchoring the assembly to the subgrade; and

FIG. 7 is a view similar to FIG. 6, but showing the load trnsfer assembly of FIG. 6 anchored to the subgrade and ready for use.

DETAILED DESCRIPTION OF AN ILLUSTRATIVE EMBODIMENT Referring now in detail to the illustrative embodiment depicted in the drawings, there is shown in FIGS. 1 and 2 a load transfer assembly installed and in use, comprising a plurality of laterally spaced, elongated dowel rods 12 supported on a wire frame structure, generally designated 14, and embedded in adjacent pavement sections 16, such as are used in highways for example. In a typical highway construction, a series of sections 16 are formed in an end-to-end relation lengthwise of the highway and separated by transversely extending longitudinally spaced joints in the form of grooves 18, which accommodate expansion and contraction of pavement sections 16 due to temperature variations. Grooves 18 usually are sealed by suitable resiliently yieldable fillers or seals 20 to preclude the ingress of liquids and solid particles, and can be formed after the concrete or paving material has been poured and at least partially set by sawing through the top surface of the cast pavement to a predetermined depth. Transverse cracks 22 extending from the bottom of grooves 18 downwardly to the subgrade 24 develop during subsequent contraction of the hardening pavement to complete the formation of separate sections 16.

Dowels 12 are laterally spaced at generally equal intervals crosswise of the highway at each joint with their respective opposite ends embedded in the adjacent pavement sections 16. Dowels 12 are located above subgrade 24 approximately midway between the latter and the upper surface of the roadway in substantial alignment crosswise of the highway, the central portions of dowel rods 12 preferable being positioned in alignment with groove 18.

Dowels 12 are loaded transfer devices, connecting the separate adjacent pavement sections 16 together and maintaining them in alignment when such sections undergo thermal contraction and expansion, causing them to move relative to each other and to dowels. 12. Dowels 12 transfer loads from one pavement section 16 to the other and prevent vertical displacement between adjacent pavement sections so as to maintain the upper surface of the roadway substantially planar under all reasonable loading conditions.

Dowels 12 typically are formed of steel rod, but it is a feature of this invention that they may be formed of any material and construction.

Wire frame structure 14 supports dowels 12 in proper position prior to and during the pouring of the concrete or other paving material, and can be formed to support any number of dowels 12 at the desired positions transversely of the highway. It should be understood that the number and spacing of dowels can vary as determined by the width of the highway and the specifications of a particular installation.

Frame structure 14 comprises a pair of frame sections extending crosswise of dowels 12 in spaced apart relation adjacent the opposite ends thereof, the frame sections being joined only by the dowels. The frame sections are identical but oppositely facing, as shown, and comprise

lower wires

26 and 28, respectively, in substantial parallelism. A plurality of

rod supporting elements

34 and 36 are mounted on each frame section in alternating relation, the sections being arranged so that opposing support elements are staggered with each gripping support element 34 being axially aligned with a guiding support element 36 for engaging the opposite ends of a dowel 12, whereby a given dowel rod 12 is gripped by an element 34 at one end while the next adjacent dowel rod is gripped by an element 34 at the opposite end.

Each gripping element 34 comprises an upwardly and inwardly inclined leg 38 welded or otherwise fixedly secured adjacent its opposite ends to

wires

26 and 30 or 28 and 32, as the case may be, on the inner sides thereof, and a helical loop 40 preferably of two or more turns at the upper end of leg 38. The convolutions of each loop 41) are canted and spaced so as to engage and grip the peripheral surface of dowel 12. To this end element 34 is formed of a steel having sufficient spring tending to cause loop formation 40 to close and thereby exert sufficient gripping pressure about rod 12 to secure the same against axial movement under normal conditions, and the convolutions are spaced apart by

wire

30 or 32 with the innermost convolution inclined oppositely to leg 38. By applying a counteracting force to unwind or open loop formation 40, the gripping pressure can be relaxed sufficiently to release rod 12 for axial sliding movement relative to loop formation 40. Normally, however, loop 40 will effectively grip dowel 12 both before and after installation of the assembly.

Each guide support element 36 comprises an upright leg 42 welded or otherwise fixedly secured adjacent its opposite ends to

wire

26 and 30 or 28 and 32, as the case may be, on the inner sides thereof, and an inverted J hook formation 44 at the upper end of leg 42. The outer end of hook 44 is welded or otherwise fixedly secured to wire 30 or 32, on the same side as leg 42 and,

in conjunction with

wire

30 or 32 forms a single loop of a size to receive dowel 12 with a loose fit permitting axial movement of dowel 12 relative to hook formation 44 in the installed, straight upright position of FIG. 1. Prior to installation, however, the inward and upward inclination of legs 38 and of support elements 34 spring the

upper wires

30, 32 inwardly relative to their associated

lower wires

26, 28 and thereby incline the legs 42 of support elements 36 inwardly and upwardly, canting the loops 44 relative to dowels 12 into gripping relation therewith as shown in FIG. 6. The alternating arrangement of

support elements

34 and 36 in each frame section biases elements 36 into the dowel gripping position or attitude of FIG. 6 until such time as they are forced into the dowel releasing attitude of FIG. 1.

Each support element 36 is provided with a foot portion 46 projecting laterally outwardly from the lower end of leg 42 and serving as a base adapted to engage and rest on subgrade 24. Foot portions 46 support frame 14 and offer stability in supporting dowel rods 12 in proper position, and are shaped to provide a hook formation 48 for receiving a spike or the like for anchoring frame 14 to subgrade 24. Hook formation 48 is formed in a plane generally normal to the plane containing upper hook formation 44 and leg 42, causing them to extend normal to dowels 12 and permitting relative motion therebetween when foot 46 is forced into a position substantially parallel to the upper surface of subgrade 24.

In assembling the load transfer assembly, each loop formation 40 of gripping support element 34 is opened sufficiently to enable one end portion of a dowel 12 to be passed therethrough. The other end of each dowel 12 is inserted through the loop defined by hook formation 44 of a support element 36 and elongated wire 31 or 32, the element 36 being sprung into an upright attitude relative to the dowels as required to facilitate such assembly. After insertion of dowels 12, loop formations 41) are allowed to relax toward their natural condition, tightly gripping dowels 12. The opposite ends of the dowels are gripped by support elements 36 which, when released, are biased into their canted, dowel gripping attitude by the frame construction with its upwardly and inwardly inclined legs 38. The entire assembly is held together by the gripping engagement of dowels 12 adjacent their opposite ends by the frame sections, and can be handled as a unit without need for welding. The assembly is positioned in place as a unit on subgrade 24 with the central portions of dowel rods 12 extending in a transverse row corresponding to the contraction joint subsequently formed, and with the frame sections positioned on opposite sides thereof.

When placed on subgrade 24 during installation, foot portions 46 initially are inclined at an angle relative to the upper surface of subgrade 24 as shown in FIG. 6. Spikes 56 are then inserted through the foot portion of hook formations 48 and driven into subgrade 24. Head spike 56 engages foot 46 and continued insertion of spike 56 into subgrade 24 tilts foot portion 46 into a generally horizontal plane against the upper surface of subgrade 24. This also tilts leg 42 from the inclined position (FIG. 6) against the spring bias of its frame section to a vertical position of use as shown in FIG. 7, causing hook formation 44 and

wires

30 or 32 to move therewith, releasing dowel 12 for axial sliding movement relative thereto, Thus, guide elements 36 are effective to lock rods 12 against movement for ease of handling prior to installation and to release the same for relative movement when finally installed for use.

After the load transfer assembly is installed in place as described above, and forms are laid out in the manner well known in the art, the flowable concrete or other paving material is poured on subgrade 24 up to the desired level forming the upper surface of the roadway and completely embedding dowels 12 therein. When the concrete is at least partially set, grooves 19 are formed transversely across the pavement in substantial vertical alignment with the central portions of the transverse row of dowels 12. Grooves 18 are formed to a depth above the level of dowels l2 and cracks 22 develop to define separate pavement sections 16.

In use, one end of each dowel rod 12 remains substantially fixed to frame 14 by gripping element loop formation 40 while the other end of each dowel is free to move axially in a hook formation 44 relative to frame 14 to accommodate movement of pavement sections 16 toward and away from each other during expansion and contraction thereof. Although one end of each dowel rod 12 is substantially fixed by means of a loop formation 40, an excessively applied axial force on dowel 12 will cause loop formation 40 to yield sufficiently to release rod 12 without damaging adjacent components or pavement. Preferably

elements

34 and 36 are staggered whereby adjacent dowels 12 are held, one at one end and the other at the opposite end, whereby alternating dowels 12 are held by each frame section embedded in the surrounding pavement section for movement therewith.

From the foregoing, it is apparent that the objects of this invention have been fully accomplished. The dowels and frame sections can be stored and shipped to the site in knockdown condition, and can be quickly assembled at the site without welding and by unskilled personnel. The assembled dowels and frame sections interact to form a stable unit which is easy to handle and install. Upon installation the dowels are released at one end for relative movement within the assembly. The supporting framework does not require dowels of a particular material of construction, and does not require destruction of dowel coatings.

A single embodiment of this invention having been disclosed in detail, it is to be understood that this has been done by way of illustration only.

I claim:

1. A load transfer support means comprising: a frame including at least one pair of opposed, spaced apart generally upright members; one of said upright members having means for gripping an end portion of a dowel against axial movement relative thereto; the other end of said upright members having means for gripping the other end portion of a dowel in one position thereof; said other member releasing the dowel for guided movement relative thereto in another position thereof; said frame normally biasing said other member into said one position.

2. Support means according to claim 1, said gripping means being selectively releasable and comprising a helically wound loop formation provided at the upper end of said one upright member.

3. Support means according to claim 1 wherein said other member means comprises a single loop provided at the upper end of said other upright member.

4. Support means according to claim 1 wherein said other generally upright member includes a ground engaging foot portion formed to provide an opening for receiving an anchoring element therethrough.

5. Support means according to claim 4 wherein said other upright chamber comprises a straight leg and said foot portion extends outwardly therefrom in a direction generally normal to said leg; said other member means includes a hook formed on the upper end of said leg and defining with a portion of said frame an opening for receiving a dowel; said leg being tiltable between an inclined position bringing said hook and frame portions into clamping engagement with said dowel for holding the latter against said axial movement and a release position generally normal to the supported dowel for permitting axial movement of a supported dowel relative to said frame.

6. Support means according to claim 5, wherein said other member is biased into said inclined position by said frame, and is tilted into said release position auto matically upon anchoring said foot portion to the ground.

7. Support means according to claim 1, wherein said frame includes second and third pairs of opposed spaced apart generally upright members spaced from said one pair of upright members on opposite sides therof; the members of said second and third pairs of upright members being reverselly positioned relative to said one pair of upright members whereby said gripping means are arranged on said frame in a staggered relatron.

8. Support means according to claim 7, wherein said frame includes a pair of frame sections each having a lower elongated wire and an upper elongated wire; said upright members being secured to each of said wire.

9. Support means according to claim 8, together with dowels extending between said frame sections and engaged by said members to complete a load transfer assembly.

10. Support means according to claim 9, wherein said one upright members have an upwardly and inwardly inclined leg secured to said wires and biasing said other members into said one position thereof.

IAHNI NU. 3,881,833

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Claim H, Line 4, "wire" should he hanged to wi.rc::--

Signcd and Scaled this

Claims

6. Support means according to claim 5, wherein said other member is biased into said inclined position by said frame, and is tilted into said release position automatically upon anchoring said foot portion to the ground.

7. Support means according to claim 1, wherein said frame includes second and third pairs of opposed spaced apart generally upright members spaced from said one pair of upright members on opposite sides therof; the members of said second and third pairs of upright members being reversely positioned relative to said one pair of upright members whereby said gripping means are arranged on said frame in a staggered relation.