Land vehicles – Wheeled – Coasters
Reexamination Certificate
2001-07-20
2002-07-16
Lerner, Avraham (Department: 3618)
Land vehicles
Wheeled
Coasters
C280S011270, C016S03500D
Reexamination Certificate
active
06419249
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a roller board, more particularly to a roller board with a pivoting roller unit which is adapted to provide enhanced stability during turning movement.
2. Description of the Related Art
Referring to
FIG. 1
, a conventional roller board
1
is shown to include a horizontal rigid platform
10
, first and second longitudinally spaced-apart base plates
21
disposed beneath and fixed to the rigid platform
10
, first and second longitudinally spaced-apart wheel assemblies
30
,
40
mounted on the platform
10
adjacent to the base plates
21
respectively, and first and second longitudinally spaced-apart roller units
2
mounted on the base plates
21
respectively.
With reference to
FIG. 2
, each of the base plates
21
has a cam retaining bore
211
and an accommodating chamber
210
which surrounds the cam retaining bore
211
and which spatially communicates with the cam retaining bore
211
. Each of the roller units
2
includes a caster
22
mounted rotatably to the base plate
21
underneath the retaining bore
211
, a roller
221
journalled to the caster
22
, and a cam mechanism. The cam mechanism includes a cam
234
in the form of a rotatable shaft that is connected to the caster
22
, and extends into the chamber
210
via the retaining bore
211
in the base plate
21
, and that has an outer circumferential wall which defines a cam face
235
with a pair of diametrically opposite horizontal flat sides
237
and a pair of diametrically opposite curved sides
236
between the flat sides
237
. A cam follower is disposed within the chamber
210
of the base plate
21
, and includes an urging spring
24
that has a first end fixed to the base plate
21
and a second end which abuts against a selected one of the flat sides
237
for urging the cam
234
in a radial direction relative to the cam
234
. Under this condition, the cam
234
is rotatable along with the caster
22
between a first position, in which, the second end of the urging spring
24
abuts against the cam face
235
at one of the flat sides
237
for urging the caster
22
to be maintained in a travelling direction parallel to a longitudinal axis of the base plate
21
, as best shown in
FIG. 3
, and a second position, in which the second end of the urging spring
24
abuts against the cam face
235
at one of the curved sides
236
for urging the caster
22
to be maintained in a transverse direction relative to the longitudinal axis of the base plate
21
, as best shown in FIG.
4
. Each of the wheel assemblies
30
,
40
includes a pair of fixed wheels of a diameter that is smaller than that of the roller
221
to facilitate turning of the roller board
1
when the roller unit
2
rotates about its axis by virtue of swaying action of the rider's weight to forward, rearward or lateral sides of the platform
10
.
One disadvantage encountered during use of the aforesaid conventional roller board
1
resides in that during turning of the roller board
1
by virtue of swaying action of the rider's weight, the second end of the urging spring
24
provides an abrupt change in orientation of the roller unit
2
upon reaching a juncture joined by an adjacent pair of the flat side
237
and the curved side
236
. Such a sudden change in orientation of the roller unit
2
results in unstable stance of the rider on the roller board
1
, and can cause the rider to fall off the roller board
1
in case the travelling speed of the roller board
1
is relatively high.
SUMMARY OF THE INVENTION
The object of this invention is to provide a roller board provided with a cam mechanism that is adapted to overcome the aforesaid disadvantage associated with the conventional roller board.
Accordingly, a roller board of the present invention includes a base plate, a roller unit, and a cam mechanism. The base plate has a cam retaining bore and an accommodating chamber which surrounds the cam retaining bore. The roller unit includes a caster mounted rotatably to the base plate underneath the cam retaining bore, and a roller journalled to the caster. The cam mechanism includes a cam in the form of a rotatable shaft that is connected to the caster and that extends into the accommodating chamber via the cam retaining bore of the base plate. The cam has a top end which defines an annular cam face with a pair of diametrically opposite lowermost points and a pair of diametrically opposite uppermost points between the lowermost points. A cam follower is disposed within the accommodating chamber of the base plate, and includes an urging spring that has a first end fixed to the base plate and a second end which is disposed above and which abuts against the cam face for urging the cam in an axial direction relative to the cam. The cam is rotatable along with the caster between a first position, in which, the second end of the urging spring abuts against the cam face at one of the lowermost points for urging the caster to be maintained in a travelling direction parallel to a longitudinal axis of the base plate, and a second position, in which, the second end of the urging spring abuts against the cam face at one of the uppermost points for urging the caster to be maintained in a transverse direction relative to the longitudinal axis of the base plate. Rotation of the cam between the first and second positions results in upward and downward movements of the second end of the urging spring in the axial direction.
In use the entire weight of the rider is concentrated on the urging spring, and movement of the second end of the urging spring between the first and second positions incurs a sufficient friction force, which in turn, ensures smooth and stable revolving of the roller unit relative to the base plate during swaying action of the rider for turning the roller board of the present invention.
REFERENCES:
patent: 4181316 (1980-01-01), Brand et al.
patent: 4246677 (1981-01-01), Downing et al.
patent: 4280246 (1981-07-01), Christensen
patent: 4336629 (1982-06-01), Jarvis, Jr. et al.
patent: 4553767 (1985-11-01), Robjent et al.
patent: 4595209 (1986-06-01), Tsai
patent: 5833252 (1998-11-01), Strand
patent: 5975546 (1999-11-01), Strand
patent: 5979916 (1999-11-01), Gatel et al.
patent: 6315312 (2001-11-01), Reyes et al.
Avery Bridget
Lerner Avraham
LandOfFree
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