Abstract
A shrinkage compensating device for seismic restraint in wood building construction combines a spring-operated take-up device (TUD) with a ratcheting split nut. The split nut, attached to or formed as part of a rotatable component of the TUD, acts as the securing nut for the TUD and allows the TUD with the split nut to be slipped over the top of a threaded rod and pulled down along the rod into place against a structural member. Several forms of attachment of the split nut to the spring-operated TUD are disclosed, as is a simplified rotatable split nut version.
Claims
1. A shrinkage compensating device for seismic restraint in wood building construction, comprising: a spring-operated take-up device (TUD) comprised of inner and outer cylinders threadedly engaged together and a coiled spring connected to the two cylinders so as to cause relative rotation of the two cylinders so that one cylinder tends to extend from the other due to rotation along threads when an activation pin is removed from the TUD, a split nut including a casing containing a plurality of internally threaded nut segments retained in a circular array in the casing, the nut segments being resiliently urged in an axial direction against inclined surfaces of the casing to urge the segments inwardly toward one another, allowing ratcheting movement of a threaded rod through the split nut in one direction only, and the split nut being attached to an upper end of the TUD such that the TUD with split nut can be slipped over the top of a threaded rod and pulled down the rod into place against a structural member, whereby slack inherent in placement of the split nut is taken up by relative rotation of the cylinders of the TUD and resulting expansion of the TUD when the TUD's activation pin is disengaged, so that the split nut engages fully with the thread of the threaded rod.
2. The shrinkage compensating device of claim 1, wherein the split nut is attached to the TUD by an integral, unitary connection between said one cylinder and the casing of the split nut.
3. The shrinkage compensating device of claim 1, wherein the split nut is attached to the TUD buy a threaded connection between the casing of the split nut and said one cylinder of the TUD.
4. The shrinkage compensating device of claim 3, wherein the threaded connection between the casing of the split nut and said one cylinder is a reverse thread.
5. The shrinkage compensating device of claim 4, wherein said one cylinder is the outer cylinder, the inner cylinder being adapted to engage against a component of wood building construction, and the inner and outer cylinders are threadedly engaged together via reverse threads, so that clockwise rotation of said one, outer cylinder relative to the inner cylinder causes the outer cylinder to extend from the inner cylinder, without tending to unscrew the split nut on a threaded rod with standard threads, and said one, outer cylinder has internal reverse threads for engagement with threads of both the inner cylinder and the casing of the split nut.
Description
DESCRIPTION OF THE DRAWINGS
(1) FIG. 1 is an elevation view, partially in perspective, showing a typical framing situation in a multiple-story building, with a seismic restraint in the form of a long vertical connecting rod, in accordance with prior art.
(2) FIG. 2 is a perspective view showing a prior art installation of a spring-activated TUD and seismic restraint system such as in FIG. 1.
(3) FIG. 3 is a perspective view showing a spring-actuated TUD as in the prior art.
(4) FIG. 4 is a perspective view showing a split nut, ratcheting TUD as installed in a seismic restraint system as in prior art.
(5) FIG. 5 is a perspective view showing a prior art ratcheting split nut TUD in greater detail.
(6) FIG. 6 is a perspective view showing an embodiment of the combined TUD of the invention.
(7) FIG. 7 is a perspective view showing the combined device of FIG. 6 in place in a seismic restraint system at the top plate of wood framing construction.
(8) FIG. 8 is a sectional view showing one manner of connection of the ratcheting TUD to the spring-actuated two-cylinder base.
(9) FIG. 9 is a sectional view showing a modification of the combined TUD, wherein the spring-actuated TUD and the split nut have an integral component.
(10) FIG. 10 is a sectional view showing another embodiment of the invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
(11) In the drawings, FIG. 1 schematically shows an installation of a seismic restraint rod 10 in a multi-story wood-frame building. The lengthy vertical threaded rod 10 is fixed into the building's foundation 12 and extends up through ceiling and top plates 14 and 16 at the top of a first floor and up to a connection with a top plate 18 at the roof level. Roof rafters 20 are indicated in the drawing. The restraint rod 10 extends through holes in the various plates 14, 16 and 18, and a nut 22 is tightened down on the rod at the top end, with a washer or metal plate 24 bearing against the upper side of the top plate 18.
(12) As is well known, the problem with such seismic restraint systems is that wood structural members shrink over time, particularly in width or thickness dimensions. Thus, take up devices or TUDs have been developed to act dynamically to take up shrinkage in height, i.e. lessening of the distance from the foundation to the top plate. A spring actuated TUD 26 is shown in FIGS. 2 and 3, as known in the prior art. Such TUDs have an outer cylinder 28, an inner cylinder 30 rotatable within and connected by threads to the outer cylinder, and a tightly wound coil spring 32 that is restrained by an activation pin 34 until the TUD has been installed. As shown in FIG. 2, such a spring-actuated TUD 26 is used with a nut 22 to tighten the TUD down against the top plate on the threaded seismic restraint rod 10. Washers or bearing plates are typically used at 36 and 38, i.e. between the TUD and the wood top plate 18 and between the nut 22 and the upper end of the TUD 26. The pin 34 is pulled to release the coil spring and activate the TUD.
(13) As the wood components shrink over time, such that their thickness dimensions decrease, the TUD 26 expands in length to take up the shrinkage. The threads between the inner and outer cylinders 28 and 30 of the TUD are reverse threads (sometimes called left-hand threads), so that the expanding rotation, caused by the released coil spring 32, rotates the upper cylinder (the inner cylinder in this case) in the clockwise direction as viewed from above. This is important in that if the rotating upper cylinder rotates the plate 38 and the nut 22, it will be in the direction of tightening the nut down on the rod 10, rather than the opposite direction which would negate the effect of the expanding TUD.
(14) Another, simpler form of TUD for seismic restraint systems is shown in the prior art drawings of FIGS. 4 and 5. These drawings show a split nut ratcheting TUD 40, which can be structured as in U.S. Pat. No. 8,881,478 or as in other similar split nuts. Split nut sections are spring-biased down against a taper or saddle that forces them together to tighten on rod threads. Downward movement of the split nut (or upward movement of the threaded rod relative to the split nut) will cam the nut section upwardly and outwardly, allowing them to slip or ratchet up the rod, thread by thread. As shown in FIG. 4, the ratcheting TUD 40 is installed above a top plate 18 of a building, with its base 42 secured down to the top plate, such as by nails. A housing or casing 43 extends up from the base 42. A bearing plate 44 is also shown in FIGS. 4 and 5.
(15) Sometimes the threaded seismic restraint rod 10 has considerable length above the plate 18, which may not always be a top plate. The advantage of the ratcheting TUD 40 is that it can be slipped over the top end of the rod 10 and simply pulled down, ratcheting its spring-loaded nut sections as it slips over the threads of the rod, rather than requiring screwing rotation down to the plate, as is required with a standard nut. Thus, it is quickly and easily installed. However, as discussed above, the ratcheting TUD does not maintain as tight a connection in the framing as is the case where rotation of a threaded connection takes place, as in the spring-actuated TUD described as reference to FIGS. 2 and 3. When the ratcheting TUD 40 is brought down to the plate and installed, its threads may be riding on top of the thread of the restraint rod 10, rather than being fully engaged, thus causing some slack. Over time, as shrinkage occurs, the rod will ratchet up through the TUD 40, slowly jumping over threads in the ratcheting fashion. Thus, there is almost always a slight bit of slack in the restraint system.
(16) FIGS. 6 and 7 show a TUD 50 according to the invention. The novel TUD 50 combines a spring-activated expanding TUD structure with a split nut, so as to have the advantages of both, and providing for elimination of slack in the system. In FIGS. 6 and 7 a spring-actuated TUD 26 is combined with a ratcheting split nut TUD 40, with the upper component of the TUD 26 fixed to the housing 43 of the ratcheting TUD. In this case the inner threaded cylinder of the TUD 26 is the upper cylinder which is connected to the ratcheting TUD 40. When the activation pin 34 is removed after installation of the combined TUD 50, the inner cylinder of the TUD 26 will rotate in the clockwise direction and the ratcheting TUD 40 will rotate along with it.
(17) FIG. 7 shows that on installation over a building's upper plate 18, the seismic restraint rod 10 has no separate nut above the TUD 50. Instead, the split nut ratcheting TUD 40 engages with the threads of the rod 10. The device is installed in the same way as a simple ratcheting split nut; it is pulled down over the restraint rod 10, ratcheting over the threads until it reaches the top plate 18, or a bearing plate 44 as shown. When thus moved into position, the split nut threads may not be fully engaged with the thread of the rod 10, i.e. the split nut threads will likely be riding on the ridges of rod threads, unless the installer assures the threads are fully engaged. Once the activation pin 34 is pulled, however, the upper cylinder and split nut device 40 will be rotated to a slight degree in the clockwise direction relative to the outer threaded cylinder of the device 26 and relative to the threaded rod 10, and the split nut/upper cylinder assembly will rise slightly. The threads will become fully engaged, with the device 50 positioned tightly against the upper plate 18. Note that the rotation of the split nut device 40 on the rod threads will be in the tightening direction, tightening the device down on the rod.
(18) FIG. 8 illustrates one preferred manner of connection of the spring-activated TUD device 26 to the split nut ratcheting device 40. Although the components could be connected together in any manner that assures movement of the ratcheting split nut 40 together with the upper cylinder of the component 26 (which could either be the inner cylinder or the outer cylinder), FIG. 8 illustrates one efficient manner of connection. In this case the inner cylinder 30 of the spring-activated TUD device 26a bears down against the top plate 18, which can be via a bearing plate (not shown). The combined TUD device 50a can be secured by fasteners (such as nails) to the plate 18, as indicated at 52.
(19) It is the outer cylinder 28a that is movable relative to the fixed inner cylinder in the example of a combined device 50a shown in FIG. 8. The coil spring 32, when released by removal of the activation pin, rotates the outer cylinder 28a clockwise (as seen from above) relative to the inner cylinder 30, and since the threads 54 between the cylinders are reverse threads, this causes the outer cylinder 28a to rise. A split nut housing or casing 43a is threaded into the outer cylinder 28a to make the connection, the casing or housing 43a having a depending annular flange 56 with a reverse male thread. Nut segments are shown at 53 and a spring or spring bushing at 55. Since the threads of the flange 56 are reverse or left-hand threads, the turning of the outer cylinder 28a in the clockwise direction will tighten the outer cylinder further against the split nut housing 43a, rather than tending to disengage the two components. Thus, the reverse threads of the combined TUD device 50a serve dual purposes of fastening the components 28a and 43a together, with spring force acting to further tighten the connection, and that of cooperating with the inner cylinder 30 to expand the two-cylinder device when shrinkage occurs.
(20) As described above, the expansion of the two-cylinder TUD portion will also tend to cause the threads of the split nut device to move fully into registry with the threads of the seismic restraint rod 10 (if they are not already in registry), on initial deployment of the device.
(21) Further, as discussed above, the combined TUD device 50a works to take up shrinkage in two ways: by the axial upward movement caused by rotational interaction of the threads 54 between the cylinders; and by actually rotating the split nut device 40a in a direction that will tighten the split nut down on the threaded rod 10. Two different relative thread rotations act to take up shrinkage.
(22) In a modified embodiment of the invention, not shown, the threads 54 between the cylinders can simply be eliminated, with provision for the outer cylinder to be rotatable relative to the inner cylinder. The split nut housing or casing 43a can be secured in a non-rotatable connection to the outer cylinder in any desired manner, such as one or more pins extending through aligned holes in the two components, or by notches in one and tabs in the other, to engage in the notches to prevent relative rotation. They could be connected together by any appropriate form of fastener, as could the embodiments shown in FIGS. 7 and 8. What is important is that the split nut housing 43 rotate along with the outer cylinder (the movable cylinder), and that the outer cylinder be rotatable relative to the inner cylinder or base component. Such a non-threaded embodiment will not include axial expansion for taking up shrinkage, but will rely on rotation of the split nut on the threads of the rod 10 for tightening the device 50a down on the rod as shrinkage occurs.
(23) They could be connected together by any appropriate form of fastener, as could the embodiments shown in FIGS. 7 and 8. What is important is that the split nut housing 43 rotate along with the outer cylinder (the movable cylinder), and that the outer cylinder be rotatable relative to the inner cylinder or base component. Such a non-threaded embodiment will not include axial expansion for taking up shrinkage, but will rely on rotation of the split nut on the threads of the rod 10 for tightening the device 50a down on the rod as shrinkage occurs.
(24) FIG. 9 shows a modification of the device shown in FIG. 8. Here a combined TUD 50b operates in the same way as the TUD 50a of FIG. 8, but the outer cylinder and the split nut housing or casing are one integral component 56. Reverse threads 54 act between an inner cylinder 30 and an outer cylinder component 28b of the integral device 56. Again, this could be modified to eliminate threads between cylinders, permitting simple rotation.
(25) FIG. 10 shows a simplified version of a combined spring-activated, split nut ratcheting TUD 60. In this case the two relatively rotatable threaded cylinders are eliminated. A split nut ratcheting device 40b is simply rotatable within a base or seat 62 that could be secured down to a building's upper plate 18 as shown. The freely rotatable housing 43b of the split nut device 40b is rotatable under the influence of a coil spring 32, which is active when an activation pin 34 is pulled. Again, the spring urges the housing 43b in the clockwise direction as viewed from above, so that rotation of the device 60 causes the split nut to tighten down on the seismic restraint rod 10.
(26) Installation of the TUD 60 is the same as described above, simply by slipping the device downwardly, ratcheting it over the threads of the rod 10 until the plate 18 is reached. As described earlier, this will result, more often than not, in the threads residing on ridges of rod threads, if thread engagement is not assured by the installer. This tends to be remedied, however, by release of the activation pin, causing sufficient rotation to firmly engage the threads. However, because of the strong force of the coiled torsion spring 32 and the potential for sudden rapid rotation of the split nut device, it is preferred that the installer be instructed to lower the TUD 60 almost to the plate 18, then to turn the TUD to tighten it down into place, so that the threads are firmly engaged before the base 62 is secured to the plate.
(27) The above described preferred embodiments are intended to illustrate the principles of the invention, but not to limit its scope. Other embodiments and variations to these preferred embodiments will be apparent to those skilled in the art and may be made without departing from the spirit and scope of the invention as defined in the following claims.
