Centering bar for architectural joint systems

A one-piece molded or cast centering bar, for an architectural joint system, is disclosed. The centering bar, which is designed for cooperation with spaced guide rails, mounted on opposed, relatively moveable structures, has a central base section and integral arm portions extending radially therefrom in opposite directions. Integral guide means are carried at the outer ends of the respective arm portions, and engage guide grooves in the respective guide rails. The centering bar is pivotally connected to a cover plate, which spans the space between the moveable structures. As the structures move toward and away from each other, the centering bar functions in a known manner to maintain the cover plate symmetrically positioned with respect to the open space.

BACKGROUND AND SUMMARY OF THE INVENTION 
Architectural joint systems commonly are installed to bridge over open 
space provided between two adjacent architectural structures which are 
expected to have relative movement, resulting from normal expansion and 
contraction, seismic activity or otherwise. One frequently employed type 
of architectural joint system incorporates a cover plate which extends 
over the open space and has side margins supported by the relatively 
movable structures on either side thereof. A centering mechanism is 
provided for maintaining the cover plate in centered relation to the open 
space, as the structures move toward and away from each other. Typically, 
such centering mechanisms involve the provision of guide rail means on 
each of the structures defining guide grooves or channels which extend 
along the adjacent edges of the structures. A plurality of centering bars 
are pivotally connected to the cover plate at various points along its 
length and are provided at their opposite ends with guide elements 
arranged to be received in the beforementioned guide grooves. Movement of 
the structures toward and away from each other causes the centering bars 
to pivot about their center points connected to the cover plate. This 
results in the center plate being held in a symmetrical, centered position 
relative to the movable structures. 
Early designs of centering mechanisms of the type described above are shown 
in U.S. Pat. No. 3,183,623 and U.S. Pat. No. 4,566,242. Especially 
advantageous forms of such centering mechanisms are shown in my copending 
U.S. Pat. application Ser. No. 881,493, filed May 11, 1992. The present 
invention is directed particularly to a novel and advantageous form of 
centering bar element for utilization in such mechanisms. 
In centering bar devices of known design, it is common to form the main 
body of the bar of a length of metal strip of the desired length, on the 
opposite ends of which are mounted guide elements of a suitable size and 
shape. For some installations, the guide elements may be spheres or 
semi-spheres, or perhaps cylinders, formed of plastic. The guide elements 
may also be formed of metal, depending on the load requirements. 
Conventionally, the guide elements are fastened to the flat metal bars by 
mounting pins or the like, which are fixed in the flat bar and extend 
upward into the guide element. In the case of the beforementioned U.S. 
Pat. No. 4,566,242, the metal bar is embedded into plastic guide elements. 
For attachment of the centering bar to the cover plate, the metal bar may 
be provided with a threaded center opening, for example, or a threaded 
sleeve or the like may be attached to the center of the bar. 
In any of a number of its existing forms, the centering bar constitutes a 
relatively labor intensive, costly component, which inherently has 
significant weaknesses, especially in the attachment of guide elements to 
the outer ends of the main metal bar. 
In accordance with the present invention, a novel and significantly 
improved centering bar device is provided, which is not only significantly 
less costly to manufacture, but is at the same time greatly improved in 
performance. Specifically, the centering bar is designed and constructed 
as a single, integral unit, advantageously molded of engineering plastic 
materials, or cast of metal. Importantly, the guide elements, mounted at 
the opposite ends of the centering bars, are integral portions of the bar 
as a whole, greatly increasing the strength of the unit at the critical 
outer end region. In the center of the unit, there is provided an integral 
base section, which extends at least in one direction. Usually downward, 
and preferably upward as well, from the radially extending arms which form 
the main body of the bar. Strengthening means, typically in the form of 
tapered webs or the like, extend from the base portion outwardly along the 
arm portions. 
For a more complete understanding of the above and other features and 
advantages of the invention, reference should be made to the following 
detailed description of a preferred embodiment of the invention and the 
accompanying drawings.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION 
Referring now to the drawing, and initially to FIG. 1, reference numerals 
10, 11 designate generally adjacent architectural structures, which are 
relatively movable with respect to each other and are separated by an 
intervening space 12. The structures 10, 11 may be of any type, including 
floors, walls, roof sections, etc. The particular form of architectural 
joint illustrated in FIG. 1 is representative of a floor joint, for 
example. 
In the illustrated arrangement, each of the floor sections 10, 11 is formed 
with a block-out 13 mounting angle members 14 secured by anchor bolts 15. 
Guide rail elements 16 are anchored to the angle members 14, by means of 
bolts 17. The guide members 16, and techniques for mounting and utilizing 
the same form the subject matter of and are described and claimed in my 
beforementioned copending application. For the purposes of the present 
description, it is sufficient to note that the guide rail members are 
formed with continuous, downwardly opening semi-cylindrical guide grooves 
18. 
A cover plate 19 bridges the joint space 12 and has opposite side margins 
20 overlying and supported by the opposed floor surfaces 21. In accordance 
with known general principles, the cover plate 19 is connected by screws 
22 to a plurality of centering bars, generally designated by the reference 
numeral 23 and to be described in greater detail. The centering bars are 
of greater length than the maximum width of the space 12, so as to lie at 
an acute angle to the respective guide grooves 18. The centering bar 
includes guide means 24 at each end slidably engaged in the guide grooves 
18. Accordingly, as the floor structures 10, 11 move toward and away from 
each other, the centering bars 23 are caused to pivot about the mounting 
screws 22, causing the cover plate to be maintained in a centered or 
symmetrical position relative to the floor sections 10, 11 during movement 
thereof. 
In accordance with the present invention, the centering bar 23 is of a 
unitary, integral construction throughout. For certain, relatively low 
stress applications, the centering bar advantageously is formed of 
injection molded engineering plastics. For applications requiring greater 
strength, the part may be a unitary casting of appropriate metal. 
Pursuant to the invention, the centering arm 23 includes a central base 
section 25, typically of cylindrical configuration. Arm portions 26, 
integral with the base section 25, extend radially outward in opposite 
directions for a predetermined distance calculated to be somewhat greater 
than the space 12 in the system in which it is to be employed. At least 
one portion 27 of the base section 25 projects vertically (preferably 
downward) from the arm portions 26, and advantageously a second portion 28 
projects vertically in the opposite direction from the arm portions. 
Stiffening elements 29 of outwardly narrowing tapered configuration extend 
from the lower projection 27 of the base section radially outward along 
the arm portions 26 to impart stiffness against vertical flexing. In 
appropriate cases, stiffening elements 29 may be provided, either 
alternatively or in addition along the top of the arm portions 26. 
At the outer ends of the arm portions 26, there are provided guide elements 
24 of generally semi-spherical configuration. These elements are 
integrally joined to the outer end extremities of the arm portions 26. 
Particularly where the guide elements 24 are of semi-spherical 
configuration, the entire base area, i.e., the full diameter of the 
spherical form, can be joined with the arm portions 26. To this end, it is 
advantageous that the arm portions have a width equal to or greater than 
the diameter of the guide elements 24. 
As shown in the drawings, the central base portion 25 has a vertical height 
greater than the thickness of the arm portions 26. A vertical bore 30 
extends through the center of the base portion 25 and is adapted for 
reception of the mounting screw 22. To advantage, the vertical bore 30 is 
not tapped, but is smooth walled, in which case the mounting screw 22 is 
of a self-tapping type. 
For installation of the cover plate and centering bars 23, the centering 
bars can be loosely attached to the cover plate by screws 22, and oriented 
generally lengthwise of the open space 12. After the cover plate is laid 
over the space 12, the screws 22 are tightened. Initially, the centering 
bars 23 will tend to rotate, but will be limited in rotation by outer 
walls 31 of the guide grooves 18. When the screws 22 are properly 
tightened, a slight downward force may be exerted on the cover plate 19, 
and a corresponding upward force on the arm portions 26 of the centering 
bar. The stresses of the upward force on the centering bar are effectively 
resisted by the stiffening elements 29. 
In some cases, it may be desirable to specifically limit the vertical 
stresses on the centering bar 23 and/or cover plate 19. In such a case, 
the vertical height of the upward projection 28 of the central base 
section is pre-calculated, so that the upper surface 32 of the base 
section contacts the bottom surface 33 of the cover plate, when the 
centering bar is in its normal, operative position, thus limiting the 
vertical stresses that can be applied to the centering bar 23 and to the 
cover plate 19. A vertically extended central base section 25 is indicated 
by broken lines 34 in FIG. 1. Since the distance between the bottom 
surface of the cover plate and the guide grooves 18 is known in advance 
from the design of the architectural joint system, the vertical height of 
the central base section 25 can easily be pre-calculated to come into 
contact with the bottom surface of the cover plate before overstressing of 
the parts is realized. 
The unitary centering bar device of the invention, although simplified in 
nature, represents an improvement of major significance compared to the 
existing devices. The production costs of the device of the invention are 
in the order of one half the cost of conventional devices. At the same 
time, the device of the invention provides significantly superior 
performance characteristics, especially in the strength of the device 
where the guide elements join with the radially extending arm portions. 
Whereas conventional devices are labor intensive, the device of the 
present invention may be replicated by largely automatic molding or 
casting procedures, with assurance that dimensions and tolerances will 
have a high degree of uniformity. 
It should be understood, of course, that the specific forms of the 
invention herein illustrated and described are intended to be 
representative only, as certain changes may be made therein without 
departing from the clear teachings of the disclosure. Accordingly, 
reference should be made to the following appended claims in determining 
the full scope of the invention. By way of example, in the above 
description and in the following claims, directional and orientational 
references, such as top, bottom, upward, downward, etc. are employed for 
convenience of description only as the elements of the structure perform 
identically whether oriented horizontally, vertically or otherwise, and 
whether used in the orientations illustrated in the drawings or in 
reversed or upside down orientations.