Patent Application
20050138768
1. Field of the Invention
This invention relates to a caster, more particularly to a caster including a swivel shaft which is riveted at a point thereof to retain an antifriction bearing unit thereon, thereby steadily supporting an appliance and permitting free movement of the appliance.
2. Description of the Related Art
Referring to
The impact force during riveting of the lower portion 154 may be transmitted to the first and second outer race members 132,133 to reduce the distance therebetween, thereby adversely affecting the turning of the fork frame 12 relative to the swivel shaft 15. On the contrary, insufficient impact force applied to the lower portion 154 may result in unsteady connection between the swivel shaft 15 and the bearing seat 121. Moreover, the dimension of the proximate segment 153 of the swivel shaft 15 has to be controlled precisely so as to fit into the first rivet hole 136 in the first outer race member 132, thereby resulting in inconvenient formation of the swivel shaft 15 and the first outer race member 132.
The object of the present invention is to provide a caster which can overcome the aforementioned problems associated with the prior art.
According to this invention, a caster includes a fork frame having a bearing seat and two legs which respectively extend downwardly in an upright direction from the bearing seat and which are spaced apart from each other in a transverse direction relative to the upright direction. The bearing seat has a larger rivet hole extending therethrough along a swivel axis in the upright direction.
A wheel is mounted between the legs for rotation about a wheel axis in the transverse direction.
A first antifriction bearing includes a first outer race member which is disposed over the bearing seat and which has a first smaller rivet hole that is aligned with the larger rivet hole along the swivel axis.
A second antifriction bearing includes a second outer race member which is disposed underneath the bearing seat and which has a second smaller rivet hole that is aligned with the larger rivet hole along the swivel axis so that the first and second smaller rivet holes and the larger rivet hole form a combined rivet hole.
A swivel shaft extends along the swivel axis, and includes a proximate segment which is configured such that when inserted into the combined rivet hole, the proximate segment is fitted into the first and second smaller rivet holes, and cooperates with the first and second outer race members to define an annular space, a head which is formed around the proximate segment and which is disposed upwardly of the first outer race member, and a point which is opposite to the head along the proximate segment and which projects outwardly of the second smaller rivet hole.
A tubular bracing member, which is made from a material that is more rigid than the proximate segment along the swivel axis, is sleeved movably on the proximate segment, and is configured to fit into the annular space such that when the point is riveted, the first outer race member abuts against the head through the tubular bracing member.
Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiments of the invention, with reference to the accompanying drawings, in which:
Before the present invention is described in greater detail, it should be noted that same reference numerals have been used to denote like elements throughout the specification.
Referring to
The fork frame 3 includes a bearing seat 32 and two legs 31 which respectively extend downwardly in an upright direction from the bearing seat 32 and which are spaced apart from each other in a transverse direction relative to the upright direction. The bearing seat 32 has a larger rivet hole 321 which extends therethrough along a swivel axis in the upright direction.
The wheel 2 is mounted between the legs 31 by a pin 30 for rotation about a wheel axis in the transverse direction.
The antifriction bearing unit 4 includes first and second antifriction bearings 43,44. The first antifriction bearing 43 includes a first outer race member 41 which is disposed over the bearing seat 32 and which has a first smaller rivet hole 411 that is aligned with the larger rivet hole 321 along the swivel axis, a first inner race 322 which is formed on an upper surface of the bearing seat 32, and a plurality of balls 431 which are interposed between the first outer race member 41 and the first inner race 322. The second antifriction bearing 44 includes a second outer race member 42 which is disposed underneath the bearing seat 32 and which has a second smaller rivet hole 421 that is aligned with the larger rivet hole 321 along the swivel axis so that the first and second smaller rivet holes 411,421 and the larger rivet hole 321 form a combined rivet hole, a second inner race 323 which is formed on a lower surface of the bearing seat 32, and a plurality of balls 441 which are interposed between the second outer race member 42 and the second inner race 323.
The swivel shaft 5 is made from a malleable material, and extends along the swivel axis. The swivel shaft 5 includes a distal segment 51 which is adapted to be connected securely to the appliance, and a proximate segment 53 which extends downwardly from the distal segment 51 and which is inserted into the combined rivet hole. The proximate segment 53 is configured to be fitted into the first and second smaller rivet holes 411,421 and to cooperate with the first and second outer race members 41,42 to define an annular space 46. A manufactured head 52 is formed around the proximate segment 53 adjacent to the distal segment 51, and is disposed upwardly of the first outer race member 41. A point 54 is formed opposite to the head 52 along the proximate segment 53 and projects outwardly of the second smaller rivet hole 421.
The tubular bracing member 45 is made from a material that is more rigid than the proximate segment 53 along the swivel axis, and is sleeved movably on the proximate segment 53 to fit into the annular space 56. Thus, when the point 54 is riveted to fasten the second outer race member 42, the first outer race member 41 abuts against the head 52 through the tubular bracing member 45. By means of the tubular bracing member 45, the impact force during riveting is transmitted to the head 52 primarily through the tubular bracing member 45.
The method of forming a swivel joint for the caster of this invention includes the following steps:
(1) forming the larger rivet hole 321 in the bearing seat 32 of the fork frame 3;
(2) forming the first smaller rivet hole 411 in the first outer race member 41;
(3) forming the second smaller rivet hole 421 in the second outer race member 42;
(4) disposing the first outer race member 41 over the bearing seat 32 such that the first smaller rivet hole 411 is aligned with the larger rivet hole 321 along the swivel axis to form the combined rivet hole;
(5) forming the manufactured head 52 around the proximate segment 53 of the swivel shaft 5 and the point 54 that is opposite to the manufactured head 52 along the proximate segment 53, and that is made from a malleable material;
(6) inserting the proximate segment 53 into the combined rivet hole so as to form the annular space 46;
(7) sleeving the tubular bracing member 45 on the proximate segment 53 to fit into the annular space 46;
(8) disposing the second outer race member 42 underneath the bearing seat 32 such that the point 54 protrudes outwardly of the second smaller rivet hole 421; and
(9) riveting the point 54.
By means of the tubular bracing member 45 which has upper and lower edges respectively abutting against the first and second outer race members 41,42, to maintain the distance between the first and second outer race members 41,42, and since the impact force is transmitted to the manufactured head 52 primarily through the tubular bracing member 45 during riveting the point 54, the gap between the second outer race member 42 and the second inner race 323, and the gap between the first outer race member 41 and the first inner race 322 can be maintained, thereby resulting in smooth rolling of the balls 441,431. Moreover, precision of the dimension of the swivel shaft 5 for fitting into the first smaller rivet hole 411 in the first outer race member 41 can be reduced for facilitating formation of the swivel shaft 5.
Referring to
Referring to
While the present invention has been described in connection with what is considered the most practical and preferred embodiments, it is understood that this invention is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretations and equivalent arrangements.
