You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
FIELD OF THE INVENTION 
     This invention relates to a bolt-less device for fastening a rail to a tie. 
     BACKGROUND OF THE INVENTION 
     According to a known conventional method of fastening a rail to a tie, a single plate spring or a double-folded plate spring is placed on a tie in abutment with the flange of a rail and a spring seat, and then the plate spring is fastened to the tie with a bolt inserted downwardly through a hole in the plate spring. The disadvantage of this conventional method is that the bolt is likely to loosen due to vibrations caused by trains. Moreover, this arrangement permits the rail to be tilted by a transverse force applied to the rail by trains. Since the tilting action cannot be held below prescribed limits, the possibility of a derailment is increased. 
     OBJECTS OF THE INVENTION 
     Accordingly, an object of this invention is to eliminate the aforementioned disadvantages of conventional rail fastening devices. 
     SUMMARY OF THE INVENTION 
     More specifically, the present invention provides an improved rail fastening device utilizing a spring member having a lower portion terminating in a shaped free end adapted to engage the flange of a rail and an upper portion which tapers toward a free end which engages the topside of the rail flange. An anchor with a shaped hole projects upwardly through the lower portion and rotatably and slidably receives a fastening element having a cam lobe and a detent adapted, when rotated and slid axially into the anchor, to stress the spring member and fasten the rail flange to its underlying tie. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front elevational view of a rail fastening device constructed according to the present invention; 
     FIG. 2 is a plan view of the device illustrated in FIG. 1; 
     FIGS. 3a, 3b and 3c are a front elevational, a plan, and a longitudinal sectional view, respectively, of an anchor used in the present invention; 
     FIGS. 4a, 4b, 4c and 4d are a front elevational, a plan, a rear elevational as seen from the side of the insertion guiding part, and side elevational views respectively, of a fastening member used in the present invention; and 
     FIGS. 5a, 5b and 5c are views illustrating certain components of the device in various operative positions, FIG. 5a being a plan view in which the fastening member has been rotated into a fastening position, FIG. 5b being a plan view in which the fastening member has been driven into the hole in the anchor to a locking position, and FIG. 5c being a side elevational view of the fastening member according to the present invention to facilitate understanding of the function of the device. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     Referring now to FIGS. 1 and 2, 1 designates a tie on which a rail 3 is mounted with an insulating elastic pad 2 provided between the rail 3 and the tie 1. On each side of the flange 3a of the rail 3, a spring receiver 6 is placed on the tie 1 in abutment with a transverse pressure receiving protrusion 1a formed in the tie 1. A spring 7 is disposed between the spring seat 6 and the flange 3a and is fastened to the tie 1 by means of a fastening member 5 having a cam section which is inserted in a hole formed in the head of an anchor 4 and turned. 
     The spring 7 is formed by bending a single plate in a generally oval shape in elevation. The spring 7 has a predetermined length between its free ends 7e and 7c, and the thickness of the upper spring portion 7a of the spring 7 is tapered from a maximum thickness at about the middle of the length of the plate forming the spring 7 toward the free end 7e of the upper spring portion 7a to provide an optimum spring constant for the spring 7. The lower spring portion 7b has a horizontally-disposed flat portion connected to the upper spring portion 7a by a curved portion 7g which engages the spring receiver 6 placed in contact with the transverse pressure receiving protrusion 1a of the tie 1. The free end 7e of the upper spring portion 7a is adapted to press against the upper side of the flange 3a. The free end 7c of the lower spring portion 7b is formed by bending the lower spring portion 7b into dog-leg or crank-shape having a vertical portion 7f which engages against the side edge surface of the flange 3a and an inturned portion which overlies the upper surface of the flange 3a with a space 8 between the underside of the free end 7c and the upper surface of the flange 3a. A hole 7d for receiving the head of the anchor 4 is formed in the lower spring portion 7b. 
     As shown in FIG. 4, the fastening element or member 5 has an insertion guiding portion 5d formed at the tip, a cam portion 5a for depressing the lower spring portion 7b of the spring 7, a detent portion 5c extending perpendicularly with respect to the cam portion 5a, and a hexagonal head portion 5b adapted to be engaged by a wrench, the portions being formed successively and continuously along the fastening member proper. 
     As best seen in FIG. 3b the anchor 4 has a root which is insulated by an insulating member 4b and which is buried in the tie 1. The head of the anchor 4 is exposed over the tie 1 and is received through the hole 7d of the lower spring portion 7b. A hole 4a is formed in the head of the anchor 4 for receiving the fastening member 5. As will be described, the fastening member 5 is inserted through the hole 4a and is turned to secure itself with respect to the lower spring portion 7b. 
     To assemble the rail fastening device, the spring 7 is fitted on the head of the anchor 4 and the spring receiver 6 with the free end 7e of the upper spring portion 7a placed in contact with the upper surface of the flange 3a and with the vertical part 7f pressed against the side edge of the flange 3a and with the curved part 7g pressed against the spring receiver 6. Thereafter, the fastening member 5 is inserted through the hole 4a formed in the head of the anchor 4 with the insertion guiding part 5d directed forward (downwardly in FIG. 5a) and the hexagonal head 5b directed rearward. During insertion, the cam section 5a is directed away from the rail. When the cam section 5a is aligned with the lower spring portion 7b, a wrench 9 is engaged with the hexagonal head 5b and is operated to turn the fastening member 5 as shown by the arrow in FIG. 1 into the solid line position. This causes the lower spring portion 7b to be depressed with the cam section 5a. Thereafter the fastening member 5 is driven into the hole of the anchor 4 by striking the hexagonal head 5b with a hammer until the detent surface section 5c of the fastening member 5 is engaged with a flat surface in the shaped hole 4a formed in the head of the anchor 4. This engagement prevents the fastening member 5 from turning in the reverse direction, i.e. in the direction opposite the arrows in FIG. 1. In this state, the underside of the free end 7c of the lower spring portion is spaced from the upper surface of the flange 3a by a suitable gap or space 8, for instance about 10 mm. The fastening member 5 can be removed by reversing the aforementioned procedure. 
     According to the rail fastening device of the present invention as described hereinbefore, when the rail is pushed outward with respect to the head thereof by a transverse pressure applied by trains, the rail tends to tilt or pivot lengthwise. This causes one flange to raise relative to the tie 1; however, the rising movement of the flange is restricted by the inturned portion of the free end 7c of the lower spring portion 7b. Thus, the free end 7c of the lower spring portion, and the thinner free end 7e of the upper spring portion of an optimum spring constant, cooperate to hold down the rail, while the vertical portion 7f of the free end 7c of the lower spring portion 7b restrains the rail from transverse movement. Accordingly, since the tilting of the rail can be effectively prevented, the derailing of trains due to increases in the track gauge can be prevented. Furthermore, since the rail fastening device of the present invention is not loosened by vibrations caused by trains, the disadvantages of the conventional bolt type fastening devices are eliminated.

Summary:
A rail fastening device comprises a curved tapered spring having free ends adapted to engage a rail flange for preventing lateral and tilting motion of the rail. The spring is secured by a fastening element having a detent which is rotated and slid into a shaped hole in an anchor embedded in the tie on which the rail is supported.