Button having plastic resin head

This invention relates to improvements in a button comprising a plastics head and a metallic leg or legs.

Buttons with plastics heads are in extensive use for ornamental effects of the head designs as well as for fastening purposes. Of these buttons, some types are known which combine a plastics head with a metallic leg piece. Varied means for joining the head and the leg piece are available according to the kinds of the plastics, but none of them thus far provided have proved fully satisfactory.

FIGS. 1 to 3 illustrate an example of the prior art using a thermosetting resin. A metallic leg piece as shown in FIGS. 1 and 2, which consists of an annular base 1 having upright legs (in this case, prongs with pointed tips) 2 with which the button is to be secured to a garment, is placed, together with a thermosetting resin, into a mold 3 and jointed integrally by thermally setting the resin to form a button head 4. In order that the leg piece can be securely embedded in the plastics head, its base 1 is annularly shaped to permit the resin to cover it completely. The button head of thermosetting resin is so hard that it is rarely scratched and permits sophisticated designs. When the button head 4 is placed in the cavity of a fitting die for attachment to a garment and a sufficient pressure for attachment is applied to the legs 2, localized forces will be exerted on the annular base 1 and hence on the button head 4, often causing cracks in the head and making the button defective. Indirectly responsible for the cracking are internal stresses that arise from the difference in thermal shrinkage coefficients between the button head and the leg piece upon the thermosetting treatment and cooling. FIGS. 4 and 5 show another conventional button which uses a rigid thermoplastic resin. A leg (in this instance a tubular stem) having a conically flaring end is inserted into a button head 6 having a recess 5 with a correspondingly spread botton. The leg is pressed in the direction of the arrow to expand the conical end so that, as shown in FIG. 5, the flaring end is flattened solidly against the spread bottom of the recess 5 to form a button. For this application a thermoplastic resin is usually used because a button head of a thermosetting resin tends to crack unless the dimensions are strictly controlled to exacting tolerance. However, a thermoplastic resin button head is not aethetically attractive, is easy to scratch or damage, and lacks resistance to heat and chemicals. FIGS. 6 and 7 illustrate a further conventional button which consists of a leg piece 11 fitted at its base flange into a recess 8 surrounded by a circular ridge 9 of a button head 10 of a rigid thermoplastic resin (FIG. 6), with the ridge 9 crimped flat against the flange (FIG. 7). The button head of this design can be made solely of a thermoplastic resin as the ridge 9 is deformed.

The object of the present invention is, therefore, to provide a button which has a rigid plastic button head free of cracking, resistive against scratch, damage, heat and chemicals and aesthetically attractive.

Briefly, the button according to the invention is characterized in that it comprises a button head of thermally set polyester resin having an internally expanded cavity, and a metallic leg piece including a generally disc-shaped base with a diameter larger than the diameter of the inlet of the cavity and at least one leg upstanding from the base, the disc-shaped base being fitted through the narrow inlet into the expanded cavity. The construction defined above enables the button to have a thermally set resin head which retains the desirable properities of the thermosetting resin. In addition, the base of the leg piece, being disc-shaped, disperses the pressure that is applied when the piece is attached to a garment, thus preventing cracking of the button head despite the fact that the latter is made of a thermally set resin. Preferably the cavity or the recess of the button head has a curved bottom and the disk-shaped base has also a complementary curved bottom. These bottons act together to uniformly disperse the force applied when the buttom is attached to a garment.

FIG. 1 is a front sectional view of a leg piece of a conventional button;

FIG. 2 is a plan view of the leg piece;

FIG. 3 is a front sectional view of the button showing how the button head is fitted to the leg piece;

FIG. 4 is a front sectional view of another button of the prior art;

FIG. 5 is a sectional view of the button in FIG. 4 as assembled;

FIG. 6 is a front sectional view of yet another button of the prior art;

FIG. 7 is a sectional view of the button as assembled;

FIG. 8 is a front sectional view of the leg piece of a button embodying the invention;

FIG. 9 is a plan view of the leg piece;

FIG. 10 is a sectional view of the button head of the button according to the invention;

FIG. 11 is a plan view of the button head;

FIG. 12 is a front sectional view of the button; and

FIGS. 13 and 14 is a front sectional view of another embodiment of the button of the invention.

The present invention will now be explained in detail with reference to the accompanying drawings which illustrate preferred embodiments of the invention.

FIGS. 8 through 12 show a button embodying the invention as comprising a button head 12 and a leg piece 13 with which the button is to be secured in place. The button head 12 is made of a thermosetting polyester resin and has an ornamental face on the front side and a circular cavity 15 narrow at the inlet but internally expanded as at 14 on the rear side. The button head 12 is preformed before uniting with the leg piece 13. The leg piece 13 consists of a generally circular base 17 of substantially the same contour as the bottom of the cavity 15 in the button head 12, and a plurality of legs 19 upstanding from points radially inside of the periphery 18 of the base 17. An important feature of the leg piece 13 is that the base 17 is circular, not annular, in shape so as to avoid any stress concentration at the time the piece is attached to the garment. Preferably, the bottoms of the base 17 of the leg piece 13 and the cavity 15 of the button head are complementary rounded to uniformly dispense the stress when the button attached a garment. The dimensional relation between the diameter of the base 17 of the leg piece 13 and the diameter of the inlet 20 of the cavity 15 of the button head 12 is such that the diametral difference is fairly large provided it does not hamper the fitting of the base into the cavity 15. This relation can be experimentally determined with ease. The internally expanded portion 14 of the cavity 15 of the button head 12 is designed to have substantially the same diameter as, or be larger than, the base 17 of the leg piece 13.

The button head 12 and the leg piece 13 of the structures described above are joined together in the following way. The head 12 is held in the cavity of a die having a supporting surface complementary or corresponding to the head surface 16. The head is then heated to a temperature at which the polyester resin softens slightly, e.g., about 50° C., and the base 17 of the leg piece is snapped into the cavity 15 of the head. In this manner the button head of polyester resin can be readily united with the leg piece without the danger of cracking.

When securing the button thus assembled to a garment, the force applied for its fitting is distributed over a broad area of engagement between the base 17 of the leg piece 13 and the cavity 15 of the button head 12. This eliminates the cracking problem despite the use of the thermosetting resin. On the other hand, the button takes the advantage of polyester resin's excellent appearance and feeling, rigidity, and resistance to heat and chemicals well comparable to those of natural stones, tortoiseshell, and the like.

FIG. 13 presents another embodiment of the invention, in which 21 is a button head of thermoset polyester resin and 22 is a leg piece having a flat disc-shaped base 23 and a tubular leg 24. This button is also assembled in the same way as the embodiment already described.

FIG. 14 is a third embodiment of the invention, in which 31 is a button head of thermoset polyester resin and 32 is a leg piece having an annular flange 35 and a tubular leg 34. The annular flange 35 is fixedly covered by a disc-shaped base 33 having a curved bottom face.

It should be obvious to those skilled in the art that numerous modifications and alterations of the embodiments so far described are possible without departing from the spirit and scope of the invention.