US 2877520 A
Description (OCR text may contain errors)
United States Patent CONNECTOR John C. Jureit, Miami, Fla. Application September 12, 1956, Serial No. 609,434 4 Claims. (Cl. 20-92) This invention relates to metal connectors and more particularly relates to metal connectors for connecting and joining timber which must bear a structural load.
The problem of joining timbers in the construction of structural wooden frame members of various types has received continuous and active attention since well prior to the advent of nails. The object of this activity has been the development of a structural timber connector which is at one time low in cost, mountable with a minimum of labor, and productive of a strong joint. Various types of specialized metal connectors have been utilized such as truss shoes and channel shaped members, which are generally secured to the timbers by nails or bolts inserted from the outside of the metal connector. These connectors are generally relatively high in cost and require the manual driving of a large plurality of nails, or the insertion and tightening of a large number of bolts in the formation of each joint. This manual labor slows the assembly of the joints and substantially increases the cost of the finished frame structure.
These disadvantages were recognized and another attempt at solution of the problem was made. According to this proposed solution, plates having fingers projecting therefrom were utilized. Some of these connectors were heavy cast members that were bolted between timbers in a lap joint. Others comprised sheets of metal from which a large number of small triangular metal tabs were struck. These plates were pressed into the surface of the wood and held in position by means of nails or bolts.
In my copending application Serial No. 537,336, filed September 27, 1955, I disclosed an improved metal timber connector comprising a metal body or lattice work from one side of which a plurality of teeth or nails project. While that connector has been found more or less satisfactory for the purpose for which it was utilized, I have now found that marked improvements may be made if certain changes in the connector are made and if certain critical relationships are adhered to.
It is accordingly a primary object of the present invention to provide an improved metal timber connector.
It is another object of the invention to provide an improved metal timber connector which is low in price, applied with a minimum of labor, and productive of a strong joint.
It is another object of the invention to provide an improved metal timber connector having a unitary skeletal structure utilizing a minimum of metal wherein the connectors may be manufactured without metal wastage.
It is another object of the invention to provide an improved metal timber connector Which affords a maximum of joint strength for a minimum of metal used in making the connector.
These and further objects and advantages of my invention will become apparent upon reference to the following description and claims and the appended drawings wherein:
Figure 1 is a plan view of a connector according to one embodiment of my invention;
2,877,520 Patented Mar. 17, 1959 Figure 2 is a vertical section of a portion of the connector of Figure 1 showing the arrangement of the teeth or nails;
Figure 3 is a vertical cross section showing one of my connectors joining a pair of timbers;
Figure 4 is a vertical section along the longitudinal axis of the connector showing the details of a single tooth; v
Figure 5 is a vertical section perpedicular to the longitudinal axis of the connector showing the details of a single tooth;
Figure 6 is a plan view of a web member having connectors according to my invention;
Figure 7 is a vertical section of the web member of Figure 6 along the line 7--7 of Figure 6; and
Figure 8 is an elevation showing the web member of Figures 6 and 7 in use in a truss.
Referring to Figure 1 there is shown a metal plate 10 having a plurality of rows 12-26 of teeth or nails 28 struck therefrom. The nails are struck in a staggered fashion such that the centers of teeth or nails in one row are opposite the metal between teeth in the adjacent rows. These teeth may be formed by a single shearing and bending operation or by separate shearing and bending operations. The teeth to the left of the center line 30 are struck from slots 32 which extend from the teeth toward the center line, while the teeth 34 to the right of the center line 34 are struck in the opposite direction, so that the slots 36 extend from the teeth 34 toward the center line. This particular configuration of teeth is important since I have found that when the teeth 34 in Figure 3 are stressed in the direction of the arrow B and teeth 28 stressed in the direction of the arrow A, a considerably higher strength is obtained than if all teeth were struck from the plate in the same direction. Applying a load to timbers 29 and 31 in the directions of arrows A and B in Figure 3 forces each tooth back upon itself and actual test results show that the joint is much stronger than when the teeth are loaded in the opposite direction.
The ends of plate 10 are sheared in a zig-zag pattern as shown at 38 and 4 0, since I have found that this provides a maximum holding strength for any given amount of metal. That is to say, if plates 10 are being cut from an elongated strip of metal, a straight shear across the ends of the plates would diminish the number of load bearing teeth or nails in each plate. Thus considering plate it shown in Figure 1, if the left end of the plate were to be sheared along the line 39, the plate would lose four teeth. The same is true with repect to the right end of the plate. The connector made from the plate 41 shown in broken lines in Figure 1 would not gain these lost teeth but would have four shortened teeth with square ends. The use of the zigzag sheared ends thus results in a worthwhile conservation of metal and reduction in connector cost.
Referring to Figures 4 and 5 I have found that there are certain critical relationships in the dimensions of the teeth which must be adhered to if a satisfactory connector is to be produced for structural uses. If the metal plate is too thin, the nails bend when pressed into the wood. If the nails are too short, lateral resistance (shear) and withdrawal resistance (pull-out) are inadequate. If the nails are too long they tend to bend on being pressed into the Wood. If the nails are too wide they tend to chop the wood grain rather than separate it and substantially reduce the strength of the joint. In order to provide a satisfactory joint which needs no further connection members, I have found that nail length L in Figure 5 must be at least 6 times the thickness T of the metal plate and should not be over approximately 17 times the metal thickness to withstand bending upon pressing. A length equal to approximately 12 times metal thickness has been found quite satisfactory. The thickness of the metal should be from approximately 70% to a 100% of the width of the nail or, in other words, the width of the nail should be 1.4 to 1.0 times the metal thickness. The nails in a given row along the grain of the wood should be spaced apart at least times the nail width W and adjacent rows across the than 3 rows are used the metal plate lacks the rigidity to prevent buckling and twisting of the plate and nails and cannot maintain the nails in an optimum anchoring position. For this reason the use of a plurality of separate single or double row connectors is completely unsatisfactory.
A further important feature of my invention is that one side of the ends of the nails are provided with a radius as shown at 42 in Figure 4. This radius must be on the side of the nail remote from the butt joint between the timbers. When the nails are formed in this manner I have found that pressing the nails into the .wood causes the nails to bend toward the butt joint as shown in Figure 3, and give considerable added strength to the joint. X-rays of connections made with connectors in which the nails have this radius show that this bending definitely does occur and that the angle of the bend C is on the order of 6 to Referring to Figures 6 and 7 there is shown a web member 44 having a channel shaped center section 46 and plate shaped ends 48 and 50. The plates 48 and 50 are provided with teeth arranged according to the invention, and the web member is then utilized as a structural member in trusses and other construction. Thus referring to Figure 8 there is shown a portion of a truss comprising an upper chord 52 and a lower chord 54 braced by means of a web member 56 having plate ends 58 and i 60. The nails in the plates are struck therefrom in the manner indicated in Figure 1, that is so that the nails are at the end of the slots towards which the members are to be loaded. Web members of this type permit extremely rapid semi-automatic assembly of roof trusses which greatly decreases the unit cost of these items.
It will be apparent from the foregoing that I have provided an improved wood connector which may be used to connect structural members which are to be subjected to structural loading. The connector is simple and economical to manufacture and may be applied with a minimum of labor. Butt joints may be formed without external projections from the timbers so that the structural frames thus formed may be stacked for easy handling.
The connector of my invention may be applied without the use of any external nails or bolts and provides completely satisfactory strength and withdrawal resistance when applied in this manner. In order to provide such a satisfactory connection my connectors must be made in the disclosed manner and dimensions. When so made it is found that the teeth are so long that conventional hammering and jacking operations are inadequate to apply the connectors without twisting in a rotary direction and flattening against the wood. It is well known that most materials can take higher loads if the loads are applied for short periods of time. This principle is applied with my connectors which I have found must be very rapidly driven in. A punch press has been found very satisfactory for this purpose.
The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
What is claimed and desired to be secured by United States Letters Patent is:
1. A structural joint for transmitting a structural load consisting of a pair of structurally butted wooden mema hers, at least one metal plate having substantially parallel faces structurally joining said members, at least three spaced substantially parallel rows of elongated teeth struck from said plate to leave three spaced rows of slots, said teeth having a width on the order of the thickness of said plate so as to be slender and nail-like in appearance from all directions and having a length equal to at least six times the thickness of said plate, a first pair of substantially parallel sides of each said tooth being formed by said faces of said plate, a second pair of substantially parallel sides of each said tooth joining said first pair of sides, said teeth terminating in pointed ends and extending away from said plate substantially normal thereto, and imbedded in said wooden members.
2. A structural joint as set out in claim 1 wherein the teeth to the left of a center line through said plate perpendicular to the rows are struck in a direction so that the slots left by the striking extend from the teeth toward the center line, and the teeth on the right side of the center line are struck in an opposite direction so that the slots left by the striking also extend from the teeth toward the center line.
3. A structural joint as set out in claim 1 wherein said wooden members are structurally joined by a pair of said plates on opposed sides thereof, said teeth from said plates being imhedded in said wooden members and the teeth of said opposed plates extending towards one References Cited in the file of this patent UNITED STATES PATENTS 527,184 Richey Oct. 9, 1894 705,626 Vogel July 29, 1902 1,470,251 Ahlvin Oct. 9, 1923 2,369,525 Blaski Feb. 13, 1945 2,827,676 Sunford Mar. 25, 1958