IMPROVEMENTS IN CASTERS FOR FURNITURE, SPINDLES, AND OTHER PURPOSES
Year: 1871

page_text: LETTERS PATENT to Martin Benson, of 9, Southampton Buildings,
London, Engineer, for the Invention of "IMPROVEMENTS IN CASTERS
FOR FURNITURE, SPINDLES, AND OTHER PURPOSES."-A communication
from abroad by Francis Alonze Gardner and Hiram Smith Turrell,
both of Danbury, Connecticut, United States of North America.
Sealed the 18th July 1871, and dated the 8th February 1871.
COMPLETE SPECIFICATION filed by the said Martin Benson at the
Office of the Commissioners of Patents, with his Petition and
Declaration, on the 8th February 1871, pursuant to the 9th Section
of the Patent Law Amendment Act, 1852.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, MARTIN
BENSON, of 9, Southampton Buildings, London, Engineer, send greeting.
WHEREAS I am in possession of an Invention for "IMPROVEMENTS IN
CASTERS FOR FURNITURE, SPINDLES, AND OTHER PURPOSES," and have petitioned
Her Majesty to grant unto me, my executors, administrators, and assigns,
Her Royal Letters Patent for the same, and have made solemn Decla-.

page_text: ration that the same is a communication to me from abroad by Francis
Alonze Gardner and Hiram Smith Turrell, both of Danbury, Connecticut,
United States of North America.
NOW KNOW YE, that I, the said Martin Benson, do hereby declare
that the following Complete Specification, under my hand and seal,
fully describes and ascertains the nature of the said Invention, and in
what manner the same is to be performed, in and by the following
statement:—
This Invention relates to improvements in antifriction bearings for
mechanisms having revolutions around vertical axes, and it consists
in so constructing the bearing surfaces that spherical rollers may be
interposed between them in such a manner that they can traverse
therein without slip.
This Invention is especially applicable to spindle and shaft steps,
cranes, millstone spindles, turbine wheel steps, railroad turntables,
baggage trundles, safes, chain and ballast boxes, portable platform
weighing scales, billiard tables, pianos, furniture casters of all kinds,
and in every situation where great weight is to be supported and rotated
on upright axes.
I am aware that friction rollers, spherical, conical, and cylindrical,
have been employed between surfaces rotating upon each other, but said
rollers have been arranged to revolve upon axes perpendicular to the
prime axes of rotation, and as the more distant parts of said rollers
necessarily travel around said prime axis in larger circuits than the
inner parts, but in equal times and revolutions, it is apparent that con-
siderable friction and slip must take place. Where conical rollers have
been employed very great friction against the outer bearings is caused
by the end thrust. The friction caused by the elasticity of the materials
of which the device is composed is not taken into account, so that will
be represented by a quantity constantly varying with the quality of the
material employed or the load to be supported.
My Invention consists in the manner of applying spherical rollers
between surfaces which have an angular relation to each other, and
which are disposed in such a manner that the axis of each of said rollers
shall be common to all the points on its surface in contact with the
bearing surfaces.

page_text: That others may more fully understand my Invention, its principles
of operations and construction, I will more particularly describe it by
referring to the accompanying Drawings.
Fig. 1 is a section and perspective view representing the Invention as
applied to a caster for furniture or other movable objects, such as
pianos, safes, weighing scales, and other objects; Fig. 2 represents a
complete vertical section of the device shewn in Fig. 1.
Fig. 3 represents a sectional elevation of the Invention as applied to
form the bearings for any vertical shaft, such as a mill spindle, crane,
turbine wheel step, and for similar purposes.
Figs. 4 and 5 represent details shewing modified methods of applying
the rollers; and Fig. 6 represents a sectional plan, the rollers placed
loosely in their cell.
Fig. 7 is a perspective view of a socket caster, and Fig. 8 is a vertical
section of a similar caster.
If a spherical roller is placed in an angular groove its contact there-
with will be at two points only, and it will roll along said groove,
revolving upon an axis parallel to a line connecting said points of
contact, and the motion of said roller will be that of a cylinder. The
relative position of the sides of said groove as to the horizon or to each
other will not affect this law. If, however, the groove is made annular,
so that the points on the surface of the roller successively in contact
with the sides of the groove will traverse around the prime axis in
circles of different diameters, then the axis of the roller will be inclined
to the line connecting said points of contact on the surface of the roller,
and these two lines will cut each other and the prime axis at the same
point. The motion of the roller will then be that of a cone.
From the above it will appear evident that a spherical roller may be
caused to roll in any annular groove around the central or prime axis of
said groove without slip, its outer part being caused to traverse a larger
circuit than the inner part in equal times and revolutions.
The principles above set forth are embodied and made operative in my
Invention for the purpose of producing frictionless bearings or steps for
upright axis.
In Fig. 3, A represents a spindle or upright shaft, which may be
supposed to belong to any machine or mechanism in which it would be
useful. The step or scat for the foot of the shaft A is formed by a

page_text: plate B, provided with a flange b. In Fig. 3 the flange b is perpendicular
to the surface of the plate B. The spherical rollers C are placed upon
said plate and within said flange, as shewn in Figs. 3 and 6. The points
of contact of the roller and the seat will be upon the line a. If the
roller C be caused to pass along the surfaces of B and b, then those
points of contact will be transferred along two parallel lines around the
surface of said roller, and said lines will, if prolonged, form circles of
different diameters. The motions of the roller will then be that of a
cone. These different circles being parallel have a common axis, and
said axis is that of a cone, which would describe a similar circuit,
namely, a cone whose apex would touch the prime axis represented by
the line c.
The line d represents the axis of revolution for the rollers C,
and the line a describes one side of the cone above described. I prefer
to employ spheres instead of cones, because the surface of B or C is
always tangential to the surface of the roller at the point of contact.
When the rollers are placed loosely in a cell, as shewn in Fig. 6, then
they revolve on their natural axes, but when a smaller number of rollers
than required to fill the cell is desired it becomes necessary to employ
some means to maintain them at equidistant points, and the most ready
means for that purpose consists of the arms e, which radiate from an
independent plate ƒ (or some equivalent mode of construction), said
arms being plate in line d, the true axis of the roller C.
Each roller
is perforated along its axis, and one of the arms e is inserted through
said perforation. A small number of rollers may thus be employed,
and the load equally distributed upon them. It will be perceived that
no labour will be imposed upon the platef and arms e, because said plate
lies loosely in its place, and the arms e serve no purpose but to retain
the rollers in proper relative positions. The shaft A is formed with a
conical foot to rest against the several rollers, as shewn in Fig. 3, and
the surface of said conical foot is calculated at such an angle as will as
nearly as possible secure an equal pressure of the roller against its two
points of contact. It will appear evident that when the shaft A revolves
the rollers C upon which it is supported will also revolve and roll along
the surfaces of B and b without slip, and therefore without friction, as
shewn in Fig. 3, the flange 6 being perpendicular to the surface of B,
the angle of the axis d will be about 57° above a perpendicular of the
prime axis c, and the line a will be about 45° above said perpendicular.
In Figs. 4 and 5 the axis of the rollers are down at 45°, and the
consequent necessary modification of the bearing surfaces are shewn.

page_text: It will appear evident that so far as the principles of operation are
concerned it is immaterial whether the step B is made the stationary
or the movable part.
Any modification of the above-described Invention which may be
necessary to adapt it to support any shaft or object revolving around
a vertical axis will not involve any further Invention, and therefore no
further detail of description is required.
To adapt this Invention to the purposes of casters for furniture and
all objects or articles designed to be moved from place to place, it is
necessary to attach a wheel or roller E whose axis does not cut the
prime axis c, but is a little way removed from the same, so that the
article of furniture or other object is moved forward the bearing wheel
will swing upon the prime axis and come into the plane of progression.
The wheel E is mounted between two lugs or ears F which support the
ends of its axle, only one of said ears is shewn in the Drawing (Fig. 2),
and said ears are attached to the rotating part of the device.
In Figs. 1 and 2 the caster is represented as consisting of a plate B
provided with an annular flange perpendicular to said plate; the
spherical rollers C are placed within said flange, and resting against its
inner surface and against the surface of the plate b. A platef provided
with radial arms e set to the normal angle of the axis of the roller C
may be also employed to maintain said rollers at equidistant positions.
In the Drawings, Figs. 1 and 2, the plate B is shewn as being provided
with a laterally projecting flange G, by means of which the caster may
be secured to the articles of furniture or other object to be supported
upon it. Other modes of attachment, however, may be substituted,
such as the ordinary socket shewn in Figs. 7 and 8. The axis of the
wheel E is within the circle described by the rollers c, and the load is
therefore at all times supported by the entire number of rollers, and
never by a part of them only, the wheel E will therefore move around
the formal axis c with the greatest possible freedom, and supposing the
parts of the device to be composed of unyielding material the freedom
with which it will move around said prime axis will not be affected by a
change of load.

page_text: rollers can revolve upon its natural axis in passing around the prime
axis, as described, to form an antifriction bearing for mechanism having
revolutions in horizontal planes.
Second. The step B, constructed with an annular flange 6 in com-
bination with the revolving part A constructed with a conical face, and
the spherical rollers c, to operate in the manner set forth.
Third. The step B, constructed with a flange 6 in combination with
the revolving part A constructed with a conical face, the spherical
rollers C, and the caster wheel E, as set forth.
Fourth. The plate for its equivalent constructed with the radial
arms e set so as to conform to the natural axis of the rollers C, in com-
bination with said rollers and the surfaces between which said rollers act.
In witness whereof, I, the said Martin Benson, have hereunto set
my hand and seal, this Eighth day of February, in the year of
our Lord One thousand eight hundred and seventy-one.