US2827676A

US2827676A - Grip plate for truss

Info

Publication number: US2827676A
Application number: US414365A
Authority: US
Inventors: Sanford Arthur Carol
Original assignee: Individual
Current assignee: Individual
Priority date: 1954-03-05
Filing date: 1954-03-05
Publication date: 1958-03-25
Anticipated expiration: 1975-03-25

Description

March 25, 1958 A. c. SANFORD 2,827,676

GRIP PLATE FOR TRuss Filed March 5, 1954 a '6 42a e25 N A A F' 6 5 v 5;; v 5; (Q 6 Q5 5256 LL.

in N

INVEN TOR. ARTHUR CAROL SANFORD 4 ATIORN EYS -m d M r, 25, 1958 GRIP PLATE FOR TRUSS Arthur Carol Sanford, Fort Lauderdale, Fla.

Application March 5, 1954, Serial No. 414,365

2 Claims.- (Cl. fil -92) The invention relates generally to roof trusses, and more particularly to grip plates designed to strengthen the heel joints of wood trusses.

In my copen'ding application Serial No. 360,785,, filed June 10, 1953, now abandoned, and entitled Truss Construction, I disclose an improved wood truss construction.

utilizing novel grip plates abutting the sides of the heel joints and other joints of the truss, said plates having a multiplicity of closely spaced projections embedded into wooden truss members.

The present invention. comprises improvements in the specific construction of such grip plates, and also improvements in the manner of applying the grip plates to the sides of a joint between two wood members of the truss,

and this application is a continuation in part of said application, Serial No. 360,785.

In said application Serial No.- 360,785 it was pointed out that by applying the grip plates to the sides of the truss joints the loads could be distributed over a relatively large area, thus strengthening the joint without notching or otherwise weakening or injuring the wood fibers. Accordingly, the allowable span of the truss can be increased and the allowable pitch can be lowered. Moreover, a simple and lightweight truss can be inexpensively prefabricated from standard two by fours having the novel grip plates at the joints without requiring any additional joint connecting means.

It is an object of the present invention to provide an improved truss construction having improved grip plates applied to the sides of its joints.

Another object is to provide an improved grip plate for distributing the load at the joint between two members of a wood truss.

A further object is to provide an improved joint construction for the members of a wood truss.

Another object is to provide a novel wood truss which has high strength at its heel joints without notching the truss members or adding means to take the thrust.

A still further object is to provide an improved, inexpensive wood truss construction which' has increased strength to permit its use inlower pitches and longer spans than conventional trusses of the same type.

These and other objects are accomplished by the improvements comprising the present invention, a preferred embodiment of which is shownby way of example in the accompanying drawing and described in detail in the following specification. Various modifications and changes in details of construction are comprehended within the scope of the invention as defined in the appended claims.

, Referring to the drawing:

Fig. 1 is a side elevation of a low pitch truss embodying the novel grip plates;

Fig. 2 is an enlarged fragmentary elevation of one of the heel joints of said truss;

Fig. 3 is a similar view with parts broken away to show the grip plate on the opposite side of the joint; and

Fig. 4 is a further enlarged fragmentary sectional view as on line 4-4, Fig. 2.

The improvedtruss shown in Fig; 1 is composed of top and bottom chord members and strut members. all made from standard wood two by foursconnected to-- gether in one plane. The bottom chord member 10 ex-' tends the full span of the truss, andthetop chordmembers 11 rest on the ends of member 10 and overhang the same as indicated at 12. A vertical strutmember. 13 extends from the apex of the top chord to the center of the bottom: chord 10, and vertical members 14 extend from intermediate portions of the topchords downwardly to the bot-' tom chord. Inclined strut members 15 extend from the joints 16 between vertical members 14-and top chords-11 to the base ot the central vertical member.

As shown in Figs. 2 and 3, the: ends of the bottom chord 10 may have. their upper surfaces beveled off form-- ing. inclined surfaces. 10" conforming to the slope of the top chords 11, where the top chords 11 reston the bottom loads encountered in housing construction, with more than the required safety factor.

The joints at the heels of the truss between the upper chord members 11 carrying compression stressesand the lower chord 10 carrying tension stresses are indicated generally at 18. These are the points where the greateststrength is required, and the joints are made by securing the novel metal grip plates 2% and 2]. to opposite sides of the joints. The plates are preferably trapezoidal in shape to conform to the joined portions of the members 10- and- 11, and areprovided with a multiplicity of closely spaced teeth or pointed projections 22 punched out of the' metal, which may be 16 gauge sheet steel galvanized if desired.

The projections 22 are preferably generally triangular and bent out substantially at right angles to the plane of the plate as shown in Fig. 4, so that they readily pene trate into the fibers of the woodmembers 10 and 1 1 when: pressure is applied normal to the outer surface of. the plate. The size of the projections may be varied some what, but excellent results are obtained in respect to dis tribution of stresses by making the projections isosceles triangles A inch on each side with an altitude'at the. apex of about /1, inch, and spacing the prdjections on 1 inchcenters in staggered rows 1 inch apart. Each projection forms a substantially triangular opening 23 in the plate.

According to the present invention, each projection is crimped or dished along a line 24 extending from its apex to the base, as best shown in Fig. 4, to give the projection a slightly angular shape when viewed edgewise as in Fig. 3, preferably angled concavely toward the opening; 23 from which the projection is formed. This crimping materially increases the rigidity and strength of each" projection, especially in respect to resisting bending or rolling back of the projections under heavy loadsimposed in opposite directions parallel to the plane of the plate, placing the plate under tension. Moreover, the slightly angular shape of the projections facilitates their penetration into the grain of the wood without shearing the fibers.

Thus, when the

plates

20 and 21 are applied to opposite sides of the heel joints of the truss the tensile strength of the steel plates is the critical strength because the combined shear strength of its embedded teeth exceeds the tensile strength of each plate. By providing the joint between members it) and 11 generally along the length of the plate or substantially along a diagonal thereof, maximum strength of the plate in tension is utilized as .compared with a transverse joint.

Another feature of thepresent invention is. that.the two

plates

20 and 21 at each" heel joint consist of one right and one left plate, the projections 22 of thetwo plates being turned in opposite directions relative to each other; As shown in Figs. 3 and 4, inthe plate 20 the triangular openings from which the projections 22 are punched are on the left side of the projections, while in the plate 21 the triangular openings are on the right side of the. projections. This arrangement of right and left teeth provides for substantially equal resistance to stresses transmitted through the wood members at the joint in any direction parallel to the plates. It will be seen that pairs of

plates

20 and 21 can .be used at both ends of the truss by reversing each plate and applying it to the opposite side of the truss from that to which it is applied at the other end.

The

plates

20 and 21 may be easily and quickly applied to the joints by first tacking the plates in position with a few stitching nails 25 driven into the wood through openings 23 along the edges of the plate. These nails may be corrugated or screw nails to increase their holding power and'serve only to hold the

plates

20 and 21 temporarily in position on opposite sides of each joint 18 'with the points of projections 22 substantially con-i tacting the Wood surfaces, until the plates are subjected by mechanical or hydraulic pressure to embed the projections, as well as the nails, firmly into the wood fibers. The wood members are then joined together at as many points as there are projections so that the load is uniformly distributed among the numerous projections and the Wood fibers are nowhere subjected to a concentrated load which would weaken or injure them. Since the stresses in the top chords 11 are all compression and the stresses in the bottom chord are all tension, the projections 22 are all in shear, and the total shear strength of the'joint is very high because it is equivalent to the shearing strength of one projection multiplied by the number of projections.

By .using the novel grip plates on opposite sides of the heel joints in the manner described, the pitch of the truss can be lowered and its span increased within the normal load requirements of low cost housing without the necessity of notching or otherwise weakening the chord members, and the chord members 11 can be extended beyond the ends of the bottom chord as desired.

The T-shaped plates 26 at the apex joint, the rectangular plate 27 at the center of the bottom chord, and rectangular plates at the intermediate joints 16 can, if desired, all be the

same typeas plates

20 and 21. Itis not necessary, however, to provide rights and lefts of

plates

26, 27 and 28 in order to have the teeth on opposite sides of the joint turned in opposite directions because the plates are symmetrical and are therefore reversible. The joints where

plates

26, 27 and 28 are used involve stresses 'of substantially less magnitude than the heel joints 18, so'that smaller plates and fewerstitching nails are required. The joints at the bases of vertical members 14 involve so little stress that almost any type of small attaching plate 29, with or without teeth, can be used satisfactorily. V r

The use of the novel grip plates greatly facilitates prefabricating strong and lightweight trusses from two by four members, using modern production methods. The

' two by four truss members'can be laid flat in proper out the areas of the plates, said projections embedded position to assemble the truss on its side, the jointplates applied temporarily by stitching nails, and then pressure applied by a suitable press to embed the projections into the wood. The prefabricated truss has all its members in one plane for easy stacking and shipment, and its simplicity and lightness of weight makes it easy to handle and erect.

What is claimed is:

1. In a truss structure having a top wood chord member carrying compression stresses resting on the end of a bottom wood chord member in the same plane and carrying tension stresses forming a heel joint, metal grip plates abutting both sides of said heel joint and having a multiplicity of closely spaced pointed projections bent out of the plates and distributed substantially uniformly throughinto the wood of said top and bottom chord members and each tooth being dishedtransversely of the direction of its penetration into the wood to, facilitate'its penetration without shearing the Wood fibers, stitching nails forced through each plate from its exterior and drawing the plates against the chord members at a plurality of spaced-apart locations, said projections and said nails being the sole means connecting the plates to the chord members, and said projections having an aggregate strength in shear greater than the combined compression and tension stresses transmitted by said top and bottom chord members.

2. In a truss structure having a top wood chord member carrying compression stresses resting on the end of a bottom wood chord member in the same plane and carrying tension stresses forming a heel joint, metal grip plates abutting both sides of said heel joint and having a multiplicity of closely spaced pointed projections bent outof the plates and distributed substantially uniformly throughout the areas of the plates, said projections embedded into the wood of said top and bottom chord members and each tooth being dished transversely of the direction of its penetration into the wood to facilitate its penetration without shearing the wood fibers, the projections in opposite plates being bent inwardly therefrom in opposite directions substantially transversely of the tension and compression stresses in said chord members, stitching nail s forced through each plate from its exterior and drawing the plates against the chord members at a plurality of spaced-apart locations, said projections and said nails being the sole means connecting the plates to the chord members, and said projections having an aggregate strength in shear greater than the combined compression and tension stresses transmitted by said top and bottom chord members.

References Cited in the file of this patent UNITED STATES PATENTS Germany Oct. 2, 1952 U S. DEPARTMENT OF COMMERCE PATENT OFFICE CERTIFICATE QF CORRECTION Patent NQa 2,827,676 March 25, 1958 Arthur Carol Sanford It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction an d that the said Let oers Patent should read as corrected below.

Column 4, list of references cited, under "UNITED STATES PATENTS", add the following:

874,514 Lindow Dec 24, 190? 2,369,525 Blaski Febo 13, 1945 2,477,163 Barnett July 29, 1949 OTIER REFERENCES "Engineering in Timber", TECO, back of cover sheeto "I Signed and sealed this 20th day of May 1958,

(SEAL) Attest:

KARL H AXLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents