Improvements in Ball Castors.
Year: 1899

page_text: Date of Application, 10th Jan., 1899-Accepted, 11th Feb., 1899
COMPLETE SPECIFICATION.
Improvements in Ball Castors.
I, WALTER WHITFIELD BOSTWICK, of No. 193, St. John's Place, in the Borough
of Brooklyn, in the City and State of New York, United States of America,
Mechanical Engineer, do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained in
and by the following statement:-
This invention relates to that class of castors known as ball castors, in which a
large central ball constituting the foot of the castor supports its load through the
intervention of a series of smaller antifriction balls. In such castors as heretofore
constructed there has always been more or less tendency to the occasional binding
of the antifriction balls and the consequent development between the parts of
the castor of sufficient friction to produce the binding of the central ball and the
destruction of the efficient action of the castor. The object of my invention is
to overcome this defect and to insure the rolling action of the antifriction balls,
and so to insure the rolling action of the central supporting ball, and to this end
my improvements consist in certain novel features hereinafter described with
reference to the accompanying drawings in which:-
:-
Figure 1 represents an elevation of a portion of a leg of a piece of furniture
having applied to it a castor embodying my invention; Figure 2 a central vertical
section of the same; Figure 3 a horizontal section in the line 3-3, of Figure 2;
Figures 4 and 5, elevations of castors illustrating modifications of my invention.
Similar letters of reference designate corresponding parts in all the said figures.
Referring first to Figures 1, 2 and 3, A, B, designate the body of the castor
which is represented, for convenience of construction, as consisting of an upper
member A in the form of a socket, for the reception of the furniture leg C, and a
lower member B, also in the form of a socket, which receives in its lower part
the central main ball or roller D) and the open bottom of which is contracted to
retain the said ball or roller. These sockets are screwed together at s. Above the
said ball or roller there is placed within the said body upon a shoulder b in the
lower member B, an internally flanged ring E which is held to said shoulder by
the lower end of the upper socket A, and through which the upper part of the
ball 1 protrudes a little way. This ring is removable for the introduction of the
ball D when A and B are separated. From the upper part of the body there
projects downwards a rigid stem F terminating in a disk which has a concave
lower face, the said disk being concentric with the ball D), The space between the
ring E and the bottom of the socket A forms a ball chamber for containing the
antifriction balls which are placed promiscuously within said chamber in
sufficient number to fill or nearly fill all the space therein not occupied by the
bearing disk F1 and its stem. The depth of the space between the ball 1) and
the bearing disk is just sufficient for the antifriction balls to roll across
between them in any direction. The upper face of the disk surrounding its
stem is rounded off downward and the spaces between it and the top of the ball
chamber and between its edges and the interior of the ring E are sufficient for the

page_text: balls cc to pass freely within and through them, the edges of the disk and the
interior of the ring being rounded to facilitate the rolling of the balls up and
down between the portion of the chamber above the disk and the portion below.
The number of the antifriction balls in the chamber should be more than
sufficient to fill the whole of the space between the disk F and the bearing ball,
and may be many times more. The balls may be inserted in any convenient way
but the most convenient way in the example represented is to place them in the
ring E, above the ball D while the upper and lower members A B are separated,
then to put the two members together in doing which the number of balls in
excess of what are sufficient to fill the space between the disk F¹ and the ball D
and which may be termed spare balls, will easily pass into the space above the
disk.
The load supported by the castor is transmitted to the bearing ball D by the
disk through the antifriction balls. In operation, the movement of the bearing
ball 1) across the floor in any direction will cause the antifriction balls between
the disk and the bearing ball to roll across the disk till they pass the edge thereof,
whence they pass freely upwards between one side of the disk and the ring E.
At the same time some of the spare antifriction balls pass downward from the
upper part of the ball chamber over the opposite side of the disk to the space
between the face of the disk and the bearing ball which is thus always kept
supplied with a sufficient number of balls. In this operation the antifriction balls
are all automatically interchangeable, those which are between the disk and the
bearing ball, and which are the only ones at any time in operation, being con-
stantly changed by reason of the number of spare ones provided and the free
and roomy passages afforded between the space above the disk which may be
termed a ball reservoir" and the space between the disk and the bearing ball. In
this operation there can be no binding of the bearing ball because rubbing friction
is almost entirely suppressed, all of such friction that exists being that between the
loosely contiguous antifriction balls which is inconsiderable.
"
The modified castors shown in Figures 4 and 5 differ from that shown in
Figures 1 and 2 only in that the upper member A¹ of the castor body instead of
being in the form of a socket to receive the furniture leg, is made with a stem A³
to enter the leg and with a flange A³ to be fastened to the bottom of the leg.
It is obvious that the castor body may be made of various forms and constructed
in many ways without departing from the principle of my invention.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:-
-
1. In a ball castor, a central bearing ball, a supporting disc above such ball, a
chamber for antifriction balls which includes spaces between said bearing ball
and disc and above and surrounding said disc, and a number of antifriction balls in
said chamber more than sufficient to fill the space between the bearing ball and
disc, substantially as herein described.
2. In a ball castor, the combination of a central bearing ball, a castor body
in which said ball is placed, a bearing disc and a stem which attaches it to the
upper part of said body, a chamber for antifriction balls provided in said body and
including spaces above and below and surrounding said disc, and antifriction balls
in said spaces, the said balls above and below the disc being automatically inter-
changeable with each other, substantially as herein described.
3. In a ball castor, the combination of a castor body, a central bearing ball in
the lower part of said body, a bearing disc affixed to the upper part of said body,
a chamber for antifriction balls provided within said body, and including spaces
above and below and surrounding said disc, a ring arranged within the said body
and forming a portion of the bottom of said chamber through which the central
ball projects, and antifriction balls within said chamber, substantially as herein
described.

page_text: 4. In a ball castor, the combination of a castor body consisting of upper and
lower separable members, a central bearing ball in the lower member, a bearing
disc affixed to the upper member, a chamber for antifriction balls between said
upper and lower members including spaces above and below and surrounding said
5 disc, a removable ring within said lower member forming a portion of the bottom
of said chamber surrounding the central ball, and antifriction balls within said
chamber, substantially as herein described.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.