NAIL

Abstract: A nail used to be driven into a foundation material such as a foamed concrete, various types of heat insulators or the like, having a hollow outer nail (2) and an inner nail (1) inserted into the outer nail (2), wherein an axial cut line (4) dividing the shaft (1a) of the inner nail (1) into a plurality of segments is crossed by an axial slot (7) dividing the shaft of the outer nail (2) into a plurality of segments, whereby both the shafts expand outwardly in planes crossing each other when the nail is driven into the foundation material, thereby increasing the engagement with the foundation material by the compression between the shafts and obtaining a nail with sufficient fastening force and resistance to be pulled.

Description: SPECIFICATION NAILS TECHNICAL FIELD The present invention relates to nails for use with foamed concrete and various types of heat insulating materials. TECHNOLOGICAL BACKGROUND Nails for use with materials having a restoring power, such as wood, provide a sufficient fastening effect even if they have a straight shaft, because the material itself shrinks and clamps the nail. However, if used with materials not having a restoring force, such as foamed concrete and heat insulating materials, nails having a straight shaft are liable to loosen or come off even by a slight shock or vibration. Therefore, various nails have been proposed which have their shaft splitted into a plurality of portions adapted to spread in the material at their tip when they are driven into a material. But, because their shaft portions merely spread in the material, they come off along the holes when a pulling force is applied. Thus, they could not provide a sufficient fastening effect. An object of the present invention is to provide a nail which obviates such a problem and has an excellent effect in preventing the coming off. DISCLOSURE OF THE INVENTION The present invention consists in nails comprising an inner nail split into a plurality of portions along an axial split line and an outer nail mounted on said inner nail and split into a plurality of portions along an axial split line, said inner and outer nails being arranged so that the split line of said inner nail and that of said outer nail will cross each other. BRIEF EXPLANATION OF THE DRAWINGS Fig. 1 is a front view of a nail according 9 the present invention; Fig. 2 is a vertical sectional side view; Fig. 3 is an enlarged horizontal sectional view; Fig. 4 is a vertical sectional view showing the nail completely driven; Fig. 5 is a sectional plan view showing the nail completely driven; and Fig. 6 is an enlarged sectional view taken along line VI-VI in Fig. 4. BEST MODE FOR EMBODYING INVENTION In order to describe the present invention in more detail, an embodiment of the present invention will be described below with reference to the accompanying drawings. As illustrated, the nail includes an inner nail 1, an outer nail 2 mounted on the inner nail, and a washer 3 mounted on the outer nail adjacent to the tip of the nail. The inner nail has a head 5 and a shaft la, said shaft being axially cut into two portions to a point near the head 5 along a line of cut 4. The two portions have a tapered surface 6 at their tip so as to serve as a guide when the nail is driven. The outer nail 2 is in the form of a pipe to be mounted on the shaft of the inner nail 1 and has its base secured to the head 5 of the inner nail 1. It is cut into the same number of portions as the shaft la of the inner nail 1 with wide slots 7 formed therebetween. But, the outer nail 2 may not be cut into the same number of portions as the inner nail 1. The nail may be so constructed that the inner nail 1 is integral with the outer nail 2 at the head of the nail. In Fig. 1, the outer nail 2 has its tip projecting slightly beyond the tip of the inner nail 1, but their length can be freely determined. The outer nail may have its tip shorter than that of the outer nail. The outer nail 2, too, has tapered surfaces 8 at its tip to serve as a guide for easy entering into the material when the nail is driven. In the embodiment, as shown in Fig. 3, the line of cut 4 for the inner nail 1 is adapted to be perpendicular to the slot 7 for the outer nail 2. The direction of split of the inner and outer nails can be freely changed by selecting the relative position between the cut line 4 and the slot 7. The washer 3 serves to prevent the tips of the inner and outer nails from spreading too early. The head 5 of the nail is not limited to the shape and structure illustrated. It may be provided with a threaded shaft or a mounting hole. Figs. 4 and 5 are sectional side and plan views, respectively, showing the nail of the present invention used to fasten a metal fitting B to a foundation A of foamed concrete or a heat-insulating material. In use, the nail is driven by striking its head 5 in the same manner as with an ordinary nail, with its tip passing through the metal fitting B. Driving proceeds with the tip of the nail not spreading until the washer 3 abuts the metal fitting B. When the nail is further driven after the washer has abutted the metal fitting, the nail advances into the material while bringing the washer 3 toward the head by reaction force from the foundation. The tips of the inner and outer nails spread outwardly with their tapered surfaces 6 and 8 serving as a guide. When the nail has been completely driven, as shown in Figs. 4 and 5, until the head 5 holds down the metal fitting through the washer 3, the tips of the inner and outer nails will spread in directions perpendicular to each other, as shown in Fig. 6. As the shaft of the inner nail 1 spreads, the tips of the inner nail come outwardly beyond the slot 7 of the outer nail. The material of the foundation A is tightly compressed between the split portions of the inner and outer nails. Therefore, both of the nails fasten to the material. Even if a pulling force is applied to the nail, it will not come off because the material bites into among the portions of the inner and outer nails. Thus, it provides a secure fastening effect. INDUSTRIAL UTILIZABILITY The nail according to the present invention has a secure coming-off prevention effect. It is comprised of a simple combination of an inner nail and an outer nail mounted on the inner nail. Therefore, it is easy to manufacture and suitable for mass production. It can be widely used to fasten metal parts to foamed concrete and various types of heat insulating materials.

Claims: What is claimed is: 1. A nail comprising an inner nail split into a plurality of portions along an axial split line and an outer nail mounted on said inner nail and split into a plurality of portions along an axial split line, said inner and outer nails being arranged so that their split lines will cross each other. 2. The nail as claimed in claim 1 wherein the split line for said outer nail are in the form of wide slots. 3. The nail as claimed in claim 1 wherein said inner and outer nails have inwardly tapered surfaces at their tip. 4. The nail as claimed in claim 1 or 3 wherein one of said inner nail and said outer nail is shorter than the other. 5. The nail as claimed in claim 1 wherein said inner nail has a head at one end thereof, said head being threaded. 6. The nail as claimed in claim 1 wherein a washer is mounted on said outer nail.

Inventors: WAKAI, TAKAO
Applicants: WAKAI & CO. LTD.
Application year: 1981
Main classification: F16B15
IPC codes: F16B15