Contraction and expansion management (CEM) joint
As ambient conditions change around a truss structure, such as a wooden truss in an attic, webs of the truss are affected by changes of moisture and temperature in the air. As the end-grain of the webs expand and contract, a contraction and expansion management (CEM) joint minimizes unwanted expansion and contraction in the truss chord. An elastic layer such as an elastomer in the CEM joint absorbs expansion while plates around the CEM joint maintain rigidity of the chord, keeping it secure to the walls. As the moisture and temperature in the attic decrease, the end-grain of the truss returns to its original state.
This invention relates generally to the inclusion of contraction and expansion management (CEM) joints in truss structures to minimize distortion, lift, and other problems encountered with expansion and contraction of the truss structure, especially relative to the structure around the truss.
BACKGROUND OF THE INVENTIONThe extensive use of trusses in modern construction enables many structural capabilities. Trusses are used in a broad range of applications ranging from steel superstructures and commercial applications to wooden roof supports for houses.
Attics of modern houses typically have trusses rather than rafters and ceiling joists. Because trusses typically are constructed from several members, trusses are susceptible to deformation from expansion and contraction. For example, as a wooden truss loses moisture over time, and as the temperature and humidity of the surrounding environment fluctuates due to changing weather conditions, the spanning member of each of the various trusses used to construct a roof will flex or bow in response to these changing environmental conditions. As these conditions fluctuate and as the spanning member begins to flex or bow, the nails or like implements which are typically relied upon to secure the truss to the various plate members of the interior walls often bend, allowing a bowing or flexing action to occur. The bowing or flexing of each of the spanning members can become significant, and often results in a bulging exceeding ½″ to about ¾″ at various points.
When such bowing or flexing of one or more of these spanning members occurs, wall board or dry-wall board secured to the underside of the spanning member deforms. For example, a portion of a ceiling of an interior room is typically lifted upward. When this occurs, the tape at the joints of upper side walls is pulled outward of the joint as the ceiling wall board or dry wall is lifted upward, thus causing significant damage to the finish of the corners of the interior rooms of the dwelling and further causing an unsightly and unfinished appearance. This problem is sometimes called “truss lift” or “truss uplift.”
This particular problem has been known and is described in U.S. Pat. No. 6,009,681 issued to inventor L. Kozloff. The '681 patent is directed to a truss bracket for securing a spanning member of a truss to a wall plate member of an interior wall of a building such as a residential house.
The '681 patent describes the problem of truss members bowing or flexing. It notes that wall board or dry-wall board secured to the underside of the spanning member can deform due to fluctuations in moisture and temperature. The truss bracket of the '681 is designed to more securely affix the truss chord to ceiling, thereby reducing deformation. However, this solution seeks to control rather than accommodate contraction or expansion, and over time, the bracket can come loose or cause damage to the ceiling. In some cases, damage results when the bracket causes the wall to lift along with the truss.
Accordingly, there is a need for an improved device to address the problem of truss lift associated with truss member expansion and contraction.
SUMMARY OF THE INVENTIONThe present invention provides a novel solution to truss lift and other problems associated with expansion and contraction of truss members. An anti-lift contraction and expansion management (CEM) joint is provided within the truss that accommodates expansion and contraction forces without permitting deformation of the truss. Damage to the surrounding structure resulting from truss expansion and contraction is thereby avoided.
A CEM joint is included within at least one member of a truss. The CEM joint has a receptacle segment and an insertion segment. The receptacle segment may have a plate extending along a cross-section of the truss member, which acts as a stop. Next to the plate stop is an elastic layer such as an elastomer gasket. Surrounding the sides of the receptacle, and extending beyond the plate and gasket, is a plate sleeve which fits around the insertion segment. The plate sleeve may have one or more holes for receiving one or more buttons located on the insertion segment which lock the insertion segment into place once the buttons are depressed, the insertion segment is placed inside the receptacle, and the buttons are raised through the holes.
The contraction and expansion management truss device of the present invention comprises a truss having a CEM joint situated in a member of the truss. The term “expansion” as used in this written description encompasses both expansion and contraction. The CEM joint of the present invention is an expansion point comprising a receptacle segment, an insertion segment, and a means for attaching the two segments.
The truss of the present invention incorporates a CEM expansion joint. Such a truss has an expansion joint situated in a member of the truss, the truss comprising: (1) at least one chord member and at least one web member; (2) an expansion joint situated in a truss member, and (3) a means for attaching the insertion segment to the receptacle segment.
The expansion joint comprises a receptacle segment comprising a protective layer, an elastic layer, and a sleeve secured to the receptacle segment and extending outward.
The insertion segment comprises an end portion that fits into the sleeve of the receptacle segment.
The truss of the present invention may be a construction truss for a roof, a structural truss, or other truss where expansion or contraction of truss members may cause distortion of the surrounding structure. Two examples of trusses embodied in the present invention are the king-post truss (
The CEM joint 4, as illustrated in
The receptacle segment 5 further comprises an elastic layer 12 which is positioned between the protective layer 14 and the end portion of the insertion segment 6 shown in
The elastic layer 12 of the receptacle segment is intended to provide a flexible barrier to unwanted expansion in the CEM joint. As the truss member expands, the CEM joint experiences the force of the insertion segment impinging on receptacle segment. The elastic layer serves to absorb this force, limit deformation, and maintain the structural integrity of the web member. Thus, in one example, the elastic layer is made of an elastic material which absorbs force from truss member expansion by contracting in the center and pushing material outwards.
The elastic layer 12 may be made of any suitable material capable of absorbing forces due to expansion while maintaining the structural integrity of the truss member. For example, the elastic layer could comprise a hydraulic or pneumatic piston. In the embodiment illustrated in
Preferably, the ethylene propylene diene M-class rubber has a diene content from 3% to 12% by weight, and more preferably 5.5% to 10% by weight.
The CEM joint 4 of the present invention has a means for attaching the receptacle segment 5 and insertion segment 6. In
As further shown in
The sleeve 10 of the receptacle segment is designed to fit around the end of the insertion segment. It may serve multiple purposes, such as: (1) acting as part of the means for attaching the two segments; (2) minimizing distortion from contraction; and (3) evenly distributing force over the cross-section of the elastic layer. In one embodiment of the claimed invention, the sleeve surrounds the end portion of the insertion segment when the two segments are attached. The sleeve may be made from any suitable material, including metal or plastic.
In one embodiment of the present invention, the sleeve is not rigidly secured to the receptacle segment. Rather, it is fitted around the end of the truss member adjoining the receptacle segment, but may translate over at least a portion of the length of the truss member. In this way, the sleeve may accommodate contractive force when attached to the insertion segment of the CEM joint. When the member contracts, the CEM joint experiences forces pulling the segments away from each other. A sleeve according to this embodiment is attached to the insertion segment, but may translate across the receptacle segment, thereby accommodating the contractive forces that might otherwise stress or damage the CEM joint. However, not all CEM joints of the present invention employ a sleeve of this nature. Rather, it may be preferable to have the sleeve rigidly attached to the receptacle segment.
The button 7 may be depressed and passed through a slot 8 in the sleeve 10 of the receptacle segment 5, as shown in
It is intended by the present invention that where desirable, the CEM joints may be designed to be inserted into truss web members. In this instance, an ordinary truss may be converted to a modified contraction and expansion management CEM truss by placing CEM joints into truss web members. This may be accomplished by the designing the insertion segment 6 and receptacle segment 5 to be incorporated into the truss web member 3. For example, the ends of the segments 5 and 6 may be adhered to the cut away ends of the web member 3.
In this example of the invention, a continuous web member 3 is prepared by cutting away or otherwise removing a portion of truss web member roughly corresponding to the size of the CEM joint 4.
Another embodiment of the present invention is depicted in
Another view of the pin CEM joint 17 embodiment appears in
The pin 18 can be any variety of suitable members known to those of skill in the structural engineering arts. Considerations for the pin construction include rigidity, strength, surface characteristics, and means for maintaining the pin in position. Means for maintaining the pin in position include but are not limited to secondary pins, such as cotter pins, braces, ties, clips, threads, nuts, or any other suitable means. The pin may or may not be allowed to rotate in its position and may contain one or more protective layers to limit wear on the pin surface or on any contacting surface, such as that of the elastic layer 12.
The elastic layer 12 is positioned between a protective layer 14 near the end portion of the insertion segment 6. The protective layer 14 may serve to distribute stresses on the receptacle segment 5.
The expansion joint in this example has an approximately constant cross-sectional area along the length of the expansion joint and has approximately the same cross-sectional area as the truss web. However, other embodiments of the claimed invention may have cross-sectional areas that vary substantially.
The present invention may incorporate various types, sizes and shapes of trusses. Indeed, trusses for various purposes are made in various shapes, sizes and materials. In the context of residential construction, trusses are often prefabricated structural assemblies that support the roof and top floor ceilings. Trusses have been used in place of older roof framing. Most commonly, trusses are triangular and include cross members fastened with gusset plates. However, the present invention may be employed in other trusses, such as trapezoidal trusses or rectangular trusses.
The many features and advantages of the present invention are apparent from the written description and thus, it is intended by the claims to cover all such features and advantages of the invention. Further, since numerous modifications and changes will readily become apparent to those skilled in the art, it is not desired to limit the invention to the exact construction and operation as illustrated or described. Hence, all suitable modifications and equivalents may be resorted to as falling within the scope of the invention.
Claims
1. A truss having an expansion joint situated in a member of the truss, the truss comprising:
- a. at least one chord member and at least one web member;
- b. an expansion joint situated in a truss member, the expansion joint comprising i. a receptacle segment comprising 1. a protective layer; 2. an elastic layer; and 3. a sleeve secured to the receptacle segment and extending outward; ii. an insertion segment comprising an end portion that fits into the sleeve of the receptacle segment; and iii. a means for attaching the insertion segment to the receptacle segment.
2. The truss of claim 1 wherein the expansion joint is situated in the truss web member.
3. The truss of claim 1 comprising a plate protective layer in the receptacle segment.
4. The truss of claim 1 comprising a metal plate protective layer in the receptacle segment.
5. The truss of claim 1 wherein the elastic layer is an elastomer.
6. The truss of claim 1 wherein the elastic layer is ethylene propylene diene M-class rubber.
7. The truss of claim 1 wherein the elastic layer is ethylene propylene diene M-class rubber having an ethylene content from 45% to 75%.
8. The truss of claim 1 wherein the elastic layer is ethylene propylene diene M-class rubber having an ethylene content from 65% to 70%.
9. The truss of claim 1 wherein the elastic layer is ethylene propylene diene M-class rubber having a diene content from 3% to 12% by weight.
10. The truss of claim 1 wherein the elastic layer is ethylene propylene diene M-class rubber having a diene content from 5.5% to 10% by weight.
11. The truss of claim 1 wherein the means for attaching the insertion segment to the receptacle segment comprises a hole located in the receptacle sleeve and a corresponding button on the insertion segment, which button may be depressed, inserted into the receptacle sleeve, and extended through the hole, thereby attaching the insertion and receptacle segments.
12. A construction truss having an expansion joint situated in a member of the truss, the truss comprising:
- a. at least three wooden chord members and at least two wooden web members;
- b. an expansion joint situated in a truss member, the expansion joint comprising i. a receptacle segment comprising 1. a protective layer; 2. an elastic layer; and 3. a sleeve secured to the receptacle segment and extending outward; ii. an insertion segment comprising an end portion that fits into the sleeve of the receptacle segment; and iii. a means for attaching the insertion segment to the receptacle segment.
13. The construction truss of claim 12 wherein the sleeve is slidably mounted on the receptacle segment and locked into place by means for connecting the receptacle.
14. The construction truss of claim 12 further comprising a cleated surface on at least one truss member.
15. The construction truss of claim 12 wherein the expansion joint has an approximately constant cross-sectional area along the length of the expansion joint and has approximately the same cross-sectional area as the truss web.
16. An expansion joint for minimizing distortion in a truss, the expansion joint comprising: a receptacle segment extending from a portion of a truss member, and an insertion segment extending from a portion of a truss member,
- a. a receptacle segment comprising i. a protective layer; ii. an elastic layer; and iii. a sleeve secured to the receptacle segment and extending outward; and
- b. an insertion segment comprising an end portion that fits into the sleeve of the receptacle segment; and
- c. a means for attaching the insertion segment to the receptacle segment.
17. The expansion joint of claim 16 wherein the elastic layer is an elastomer.
18. The expansion joint of claim 16 wherein the elastic layer is ethylene propylene diene M-class rubber.
19. The truss of claim 16 wherein the means for attaching the insertion segment to the receptacle segment comprises a hole located in the receptacle sleeve and a corresponding button on the insertion segment, which button may be depressed, inserted into the receptacle sleeve, and extended through the hole, thereby attaching the insertion and receptacle segments.
Type: Application
Filed: Apr 16, 2010
Publication Date: Oct 20, 2011
Applicant: Neuro Guard, Inc. (Sugar Land, TX)
Inventors: Carter E. Morrett (Veedersburg, IN), Jeffrey A. Kunze (Houston, TX)
Application Number: 12/662,427
International Classification: E04B 1/68 (20060101); E04B 1/21 (20060101); E04H 12/00 (20060101); E04C 2/20 (20060101);