referring to fig5 an in - line roller skate in accordance with the present invention is generally comprised of a boot 1 , a front wheel frame 2 , a rear wheel frame 3 , two rivets 4 , two ball socket shells 5 , a brake pad 6 , and four wheels 7 . the boot 1 is injection - molded from plastics , comprising a front stud 10 and a rear stud 11 raised from the sole , a first through hole 100 at the front stud 10 through the sole , a second through hole 110 at the rear stud 11 through the sole , a first spring holder 12 integral with the sole between the front stud 10 and the rear stud 11 , the first spring holder 12 comprising a recess 120 , a mounting groove 121 and a notch 122 , a second spring holder 13 integral with the sole between the first spring holder 12 and the rear stud 11 , the second spring holder 13 comprising a recess 130 , a mounting groove 131 and a notch 133 , two spring elements 14 ; 15 respectively mounted in the recesses 120 ; 130 , two pairs of locating pins 16 respectively mounted in the recesses 120 ; 130 at two opposite ends to secure the ends of the spring elements 14 ; 15 in place , two pairs of locating slots 17 ; 18 formed at the sole and respectively spaced between the studs 10 ; 11 and the spring holders 12 ; 13 , and two metal plates 19 each having two ends respectively fastened to the locating slots 17 ; 18 . the wheel frames 2 ; 3 are injection - molded from plastics , and fixedly fastened to the sole of the boot 1 by the rivets 4 , and longitudinally arranged in a line . each wheel frame 2 or 3 comprises a through hole 20 or 30 connected to the first through hole 100 or second through hole 110 on the boot 1 by the respective rivet 4 , a pair of thrust ball bearings 21 or 31 mounted around the respective rivet 4 and disposed at two opposite ends of the through hole 20 or 30 , a receiving trough 22 or 32 is mounted at the top near one end , a coupling flange 24 or 34 raised along one side of the receiving trough 22 or 32 , a projecting block 25 or 35 at one end of the coupling flange 24 or 34 , two retaining holes 220 or 320 provided in the receiving trough 22 or 32 at two opposite ends , a metal plate 23 or 33 mounted in the receiving trough 22 or 32 , the metal plate 23 or 33 having two opposite ends respectively fastened to the retaining holes 220 or 230 , a screw hole 26 or 36 at the bottom near one end , and two transverse axle holes 27 or 37 , and two bolts 28 or 38 respectively mounted in the transverse axle holes 27 or 37 to hold the respective pair of wheels 7 in a line . the rivets 4 are respectively fastened to the through holes 100 ; 110 on the boot 1 and the through holes 20 ; 30 on the wheel frames 2 ; 3 to secure the wheel frames 2 ; 3 to the boot 1 , enabling the wheel frames 2 ; 3 to be turned about the rivets 4 leftwards or rightwards . the ball socket shells 5 are respectively mounted in the receiving troughs 22 ; 32 . each ball socket shell 5 has two ball holes 50 , and two steel balls 51 mounted in the ball holes 50 and peripherally projecting out of the ball holes 50 from the ends of the ball holes 50 and retained in close contact with the metal plates 19 ; 23 ; 33 . the steel balls 51 can bear the pressure from the wheels 7 and help the front wheel frame 2 and the rear wheel frame 3 deflect under the sole of the boot . the brake pad 6 can be fastened to the screw hole 26 on the front wheel frame 2 or the screw hole 36 on the rear wheel frame 3 . the wheels 7 are respectively mounted in the wheel frames 2 ; 3 are turned about the bolts 28 ; 38 . the assembly process of the in - line roller skate is outlined hereinafter with reference to figs . from 5 through 7 . the ball socket shells 5 with balls 51 are respectively mounted in the receiving troughs 22 ; 32 , then the front wheel frame 2 and the rear wheel frame 3 are respectively attached to the sole of the boot 1 , permitting the coupling flanges 24 ; 34 and the projecting blocks 25 ; 35 to be forced into engagement with the mounting grooves 121 ; 131 and notches 122 ; 132 of the spring holders 12 ; 13 respectively ( see fig8 ), then the spring elements 14 ; 15 are mounted around the receiving troughs 22 ; 32 and fastened to the spring holders 12 ; 13 to hold the wheel frames 2 ; 3 in alignment , and then the rivets 4 are respectively fastened to the through holes 100 ; 110 on the boot 1 and the through holes 20 ; 30 on the wheel frames 2 ; 3 to secure the wheel frames 2 ; 3 and the boot 1 together and at the same time the thrust ball bearings 21 are respectively mounted around the rivets 4 and retained at top and bottom sides of the wheel frames 2 ; 3 , and then the wheels 7 are respectively fastened to the front wheel frame 2 and the rear wheel frame 3 by the bolts 28 ; 38 , and then the brake pad 6 is fastened to the screw hole 26 on the front wheel frame 2 or the screw hole 36 on the rear wheel frame 3 . referring to figs . from 8 through 10 and fig7 again , when the user skates straightway forwards , the four wheels 7 are longitudinally aligned . when making a turn or changing the skating direction , the roller skate is slightly tilted leftwards or rightwards subject to the desired direction , thereby causing the wheels 7 to deviate from the longitudinal central line c at an angle θ ( see fig9 ), and therefore the wheels 7 are moved forwards along a curve line . when the wheels 7 are forced to deviate from the longitudinal central line c , the spring elements 14 ; 15 are stretched by the receiving troughs 22 ; 32 of the wheel frames 2 ; 3 to expand . the angle of deviation is controlled by the tilting angle of the roller skate and the constraint of the projecting blocks 25 ; 35 and the notches 122 ; 132 ( see fig1 ). when the tilting force is released from the roller skate , the steel balls 51 are rotated in the respective ball holes 50 between the metal plates 19 ; 23 ; 33 , enabling the wheel frames 2 ; 3 to be deviated from the longitudinal central line c smoothly . because the steel balls 51 are rotatably retained between the metal plates 19 ; 23 ; 33 , the rotation of the steel balls 51 does not damage the surface of the sole of the boot 1 and the wheel frames 2 ; 3 . when the tilting force is released , the spring elements 14 ; 15 immediately return to their former shape , and the wheels 7 are returned to the longitudinally aligned position . if the skater is going to fall when skating , the wheels 7 are automatically forced to deviate from the longitudinal central line c at an angle , so as to support the skater in a balanced manner . further , because the wheels 7 are respectively mounted on the front wheel frame 2 and the rear wheel frame 3 , the front wheel frame 2 and the rear wheel frame 3 are forced to deflect separately when the roller skate is tilted in one direction . therefore , the front wheel frame 2 and the rear wheel frame 3 receive no torque when the skater changes the skating direction . this design greatly prolongs the service life of the in - line roller skate . figs . 11 and 12 show an alternate form of the present invention . according to this alternate form , the boot 8 has two holders 82 ; 83 integral with the sole between the studs 80 ; 81 . the holders 82 ; 83 each comprise a mounting groove 821 ; 831 and a notch 822 ; 832 . two sets of locating rods 84 ; 85 are raised from the sole of the boot 8 and respectively spaced between the studs 80 ; 81 and the holders 82 ; 83 . two spring elements 86 ; 87 are respectively fastened to the locating rods 84 ; 85 , each having two opposite ends respectively clamped on opposite ends of the receiving troughs 22 ; 32 ( see fig1 and 14 ). the operation of this alternate form is similar to the aforesaid first embodiment of the present invention .
a in - line roller skate having a front wheel frame and a rear wheel frame respectively pivoted to the sole of the boot thereof by rivets and arranged in a line to hold a respective pair of longitudinally aligned wheels , a brake pad selectively fastened to the front wheel frame or rear wheel frame , and two ball socket shells respectively mounted in receiving troughs on the wheel frames , the ball socket shells each holding two steel balls in close contact with the sole of the boot , allowing the wheel frames to flex with sole when the roller skate is tilted to change its skating direction . flanges and notches are respectively provided at the wheel frames and the sole of the boot to act against the ball socket wheels and to limit the deviating angle of the wheel frames .