Improvements in Roller Castors.
Year: 1889

page_text: Date of Application, 21st Dec., 1889
Complete Specification Left, 20th Sept., 1890-Accepted, 25th Oct., 1890
PROVISIONAL SPECIFICATION.
Improvements in Roller Castors.
I, EDWIN CHAMBERS JOHN DEVIS, Engineer, of Laurel Cottage, School Road,
Moseley, near Birmingham, in the County of Warwick, do hereby declare the
nature of this invention to be as follows:-
Roller castors, as usually constructed, depend for their sensitiveness in
swivelling upon the distance at which the roller is set from the axis of the
swivel pin and the wrench on the swivel pin is also directly proportional to
this distance, consequently the swivel bearing has to be made heavy to stand
its work reasonably, and even then the sensitiveness of the castor diminishes
quickly with use on account of the unevenness of the wear.
The objects of my invention are to reduce this wrench to nothing or nearly
so by making the normal position of the roller vertically under the weight or
nearly so, and to provide for the temporary automatic production of a swivelling
moment when the castor and what it carries is moved.
For the latter purpose I use an extra wide roller with little or no barrelling
on the rim, or in some cases two or more narrower rollers on one axis, and I so
construct the castor that when pressure comes on it horizontally, unless at right
angles to the roller axis, the latter cants slightly out of its horizontal position
and instead of the roller or rollers bearing on the floor along a line on their
lower side, as they do normally, they bear only at one point at or near the
extremity of such a line and are free to swivel round that point and are made to
do so by the pressure at the swivelling pin above, or a corresponding part.
The exact construction and the general appearance of the castor vary con-
siderably according to its intended uses, but in all cases the roller or rollers are
made to cant slightly in a vertical or nearly vertical plane through their axis
and about a point at or near one end of their line of contact with the ground,
and then to swivel round a line passing upwards from that point in a direction
depending on the construction of the castor.
The amount of cant or tilt necessary to the successful action of the castor is
so slight that the roller or rollers may remain in actual contact with the floor
at all the normal points of contact, if the floor is carpetted, provided the weight
is concentrated towards one end.
When more than one roller are used their rims may be barrelled as usual,
and the rim of the single roller may be reduced in diameter between the ends.
Dated this 20th day of December 1889.
COMPLETE SPECIFICATION.
Improvements in Roller Castors.
-
I, EDWIN CHAMBERS JOHN DEVIS, Engineer, of Laurel Cottage, School Road,
Moseley, near Birmingham, in the County of Warwick, 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:.
Roller castors, as usually constructed, depend for their sensitiveness in
Swivelling upon the distance at which the roller is set from the axis of the
swivel pin and the wrench on the swivel pin is also directly proportional to
this distance, consequently the swivel bearing has to be made heavy in order to
stand its work reasonably, and even then the sensitiveness of the castor diminishes
quickly with use on account of the unevenness of the wear.

page_text: The objects of my invention are to increase the sensitiveness and durability of
roller castors by providing means whereby, the eccentricity of the rollers being
made very small, the swivelling moment is increased automatically by side
pressure on the castor, or the furniture which it carries, when such pressure is
exerted in order to move the furniture.
I prefer to give the rollers a small eccentricity in order to avoid dead' points
and ensure smooth and easy working, though according to the theory of my
invention, and in some applications of it, it is not necessary to do so.
I so construct the rollers or bowls " that, instead of having a single bearing
point on the floor under the centre of their axis, they have two such points at
some distance from each other and from the vertical line through the centre
of their axis. That is to say, I use either one wide roller not barreled on the
face, or two or more narrow rollers set some distance apart from each other,
or some modification of these.
In combination with such rollers I provide means whereby their axis is
canted slightly out of the horizontal when pressure is put on them (as in moving
the furniture) otherwise than at right angles to such axis, the effect of which
is that this swivelling force, instead of acting round the centre of the axis,--a
point very near to the line of such force, acts round a point near the extremity
of the axis, which point is at a considerable distance from the line of such
force. This is shown in the diagram Fig. 1 of the appended drawings, in
which the full lines apply to my improved castor and the dotted ones to an
ordinary roller castor of the same eccentricity. With a force F, exerted in
the direction indicated by the arrow passing through the swivelling centre C
the point B lifts slightly and A becomes a swivelling point, and the arm A A¹
of the swivelling "couple" is thus, in the case of my castor, about twice what
it would be, a a', in the case of the ordinary castor. When the force F₂ is at
right angles to the axis of the rollers there is no swivelling effect in either
castor, and of course none is required. When the force F3 is parallel to the
axis the swivelling arm or moment is the same in the two castors, but in this
case while, in the ordinary castor, it is at its maximum and diminishes quickly
down to zero as the castor swivels round, reaching a very small amount con-
siderably before the roller has taken its right direction, in my castor on the
other hand it is not near its maximum but begins to increase immediately
the furniture is moved and increases quickly up to its maximum as the castor
swivels round, afterwards diminishing again, but remaining always of consider-
able amount as long as the roller or rollers are, in any degree, out of their right
path, namely the amount due to the arm A a. Also with a force in the direc-
tion F, during the first instant the motion of my castor, or rather of the
wheel A consists largely of rolling and in a less degree of swivelling, while
that of a in the ordinary castor consists wholly of swivelling and as, as is well
known, a wheel swivels or alters its direction more easily when it is rolling
or altering its position than when it is stationary, it follows that my castor,
even at the moment under consideration, swivels more easily than the ordinary
castor, and as a matter of fact I find that this difference is very marked.
To obtain the canting of the axis of the rollers I prefer to use what I call a
conical axis, that is one which is inclined, in a greater or less degree, from the
vertical, and which I constrain to describe a conical or equivalent path round a
vertical axis, and round which again I allow the axis of the rollers to oscillate,
the latter being at right angles to the conical axis, though preferably not
exactly intersecting it.
The roller axis being at right angles to the conical axis and being normally
kept horizontal by the weight of the furniture, it is necessarily tangential to
the cone described by the conical axis, or parallel to a tangent, but the conical
axis being between the furniture and the rollers the first effect of side pressure
on the furniture is to make that axis describe its conical path, while the rollers,
retarded somewhat by friction, do not follow it round at once, and consequently

page_text: their axis is temporarily and slightly deflected from its parallelism to a tangent
to the cone, and being always at right angles to the conical axis it foliows
that it is also temporarily and slightly deflected from the horizontal. The
amount of this deflection or "canting "varies with the nature of the floor but is,
in any case, very small and on a smooth, hard floor is hardly perceptible, as it
generally stops as soon as the weight of the furniture has been all or mostly
taken off the one point of contact with the floor and concentrated on the other,
and it is chiefly because the rollers do not altogether leave contact with the floor
at either point that I prefer to use two rollers so that they shall be free to move
in any direction without dragging.
Referring now to the accompanying drawings, Figs. 2 to 10, inclusive, show
various patterns of my castor in which the pin or spindle A which contains
and carries the conical axis also carries the horizontal axis B of the rollers and
is, by means of its spherical end a, working in a cup, enabled to perform both
the conical and the oscillatory movement itself. The pin A is enclosed by a
tube or socket C, somewhat larger in diameter than itself, so that, while the
weight of the furniture keeps the pin at the side of the tube the latter con-
strains the former to a conical path. In Fig. 9 there is, strictly speaking no
horizontal axis to the rollers, it being broken and inclined for constructive
purposes, but it is evident that a horizontal line through the axes is exactly
equivalent, for the present purpose, to a horizontal axis. Figs. 11 & 12 show
two views of a similar castor, but in which the functions of the pin A and
tube C are interchanged, the former being fixed and the latter describing the
conical and oscillatory movements round it and carrying the roller axis. Figs. 13
to 18, inclusive, show various patterns in which the conical and the oscillatory
movements are given by two separate parts. Thus in Figs. 13 to 16, inclusive,
the main pivot pin or tube A is allowed to oscillate or swivel only and is made
in one with an inclined pivot pin or tube E, so that the latter moves in a conical
path, while a separate piece D,-pin or tube, as the case may be,-oscillates
about and carries the roller axis. In Fig. 17 the pin A is constrained to its
conical motion by a spherical flange a bearing on a fixed spherical plate C, on
which it slides, and in Fig. 18 by a small Hange a on the edge of which it
tilts, in both these cases a separate piece D being used to give, not only the
oscillatory movement necessary for the canting of the rollers, but also the
main swivelling of the castor.
I prefer that the oscillating centres should be in the form of pivots and have
spoken of them as such, but when desired the pins may be made to work on
shoulders, as shown in Figs. 21, 22, & 25 in some forms.
I will now describe some details of construction:-Figs. 2 & 3 show the form
in which the rollers may be made when single wide rollers are used and they
are made of metal, the hollow in the middle being for the purposes of ensuring
that the bearing points are wide apart, of economising metal, and lightening
the appearance of the castor. Figs. 4 & 5 show advantageous proportions for
double rollers when they are used. It may be understood that either single
or double rollers may be used for any of the patterns described, though I
prefer double rollers for the reason already stated and because they are better
in appearance and in most cases allow of the height of the castor being reduced.
The roller axis should be at a distance from the conical axis (that is, the
centre line of A in Figs. 3 to 10, of C in Fig. 11, and of D in Figs. 13 to 18)
of about for ordinary chair castors to 3" for large castors. The inclination
of the conical axis to the vertical may be about 15° though a smaller angle is
sufficient if the castor is well proportioned and a larger angle is chiefly dis-
advantageous when and because it unnecessarily increases the eccentricity of
the rollers, and when very large it makes the effort necessary to cant the rollers
inconveniently great. Where the single pivot is used however, as in Figs. 3
to 10 this angle may be less and may be determined by making the tube or
socket from " to "larger in diameter at the mouth than the pin which works
1"

page_text: in it, according to the size of the castor, the pin being from 3" to 2" long
from the centre of the pivot to the mouth of the tube; but it must be under-
stood that these proportions are given as approximate only, and for castors of
good workmanship, and do not necessarily hold equally well for all designs and
for common workmanship. The tube may have an enlarged mouth as shown
in Figs. 2 & 3 for a bush in on the pin to work in, to diminish wear and friction.
The diameter of the rollers may be made equal to that of the plate or socket by
which the castor is attached to the furniture, and the width of the rollers
(along their axis) may be the same or a little less. Other proportions can be
determined with sufficient accuracy from the drawings.
In the castors shown by Figs. 3 to 10, inclusive, the pin or spindle A works
on a spherical pivot in the tube or socket C and carries at its lower end the
axle pin B of the rollers, either by the usual means of a "horn," as in Figs. 2, 3,
6 & 7 or by a central block or boss, as in Figs. 4, 5, 8, 9, & 10.
The means of holding together the pin A and tube C are various; thus in
Fig: 3, the pin has a shoulder d at its upper end and beneath this shoulder
project one or more pins, e, e, screwed through the sides of the tube. In Fig. 5,
the pin A has an enlarged spherical end a, and is passed through the tube from
the top before being attached to the piece B carrying the rollers.
A cap e,
preferably of steel, is then pressed down over the spherical head into the socket
of the castor, or, in the case of a plate castor, rivetted on to the plate, and
the latter makes a very suitable castor for ottomans and the like. In Fig. 10
the pin A has a similar enlarged head a which rests on a shoulder in the tube
as shown and works in the bearing piece d which may be screwed into the tube,
or the tube may be beaded down over it as shown. In Figs. 6 & 7 the body of
the tube C is open and the pin A is pivotted in the head of the pin g, which
is cupped for the purpose. The tube in this case consists of the plate c₁, the
ring, and the arms or ribs ca connecting the two, and the open spaces between
the ribs allow of a small pin & being put through the pin A to keep the latter
in place as also of the small screws f being put in easily. A nut may be used
in this case instead of the pin d, and the cup for the pivot a may be formed
in a boss on the bottom of a socket when a socket castor is preferred to a plate
castor. In Fig. 8 a bearing piece c,-which may be made solid, as shown,
or stamped from a piece of sheet, is cupped for the spherical head a and then
turned down over it by spinning or otherwise. In Fig. 9 the head of the pin
is similarly cupped and turned down over the enlarged spherical head a,
preferably before being put into the tube C. In Figs. 13 & 16 the pin A has
a grooved round it, near its upper end and one or more small pins e are driven
through holes drilled in the tube in such positions that the pins e project into
the grooves d, as shown. In Fig. 15 a saw cut is made in the side of the tube C
opposite the groove d and a small piece of sheet metal or of square wire e is
driven in and may be fixed firmly by a touch of solder. In Figs. 20 & 24 the
side of the tube opposite the groove in the pin A is weakened as shown at d,
in Fig. 20, by nicking with a file, or in the casting, and a tongue of metal,-
as shown at da, Fig. 20, and c, Fig. 24,-is knocked or pressed in with a flat
nosed chisel or other suitable tool. In Figs. 21 & 22 the pin A bears on a
shoulder a instead of a pivot and the reduced neck e passes through a reduced
opening at the top of the tube and through the washer d and is rivetted over
tho latter. In Fig. 19 a small hole 6 is drilled through the pin A and a wire d
passed through and bent down at one or both ends so as to lie in the grooves f
when compressed but to spring slightly out of them when free: the tube is
slightly chambered out at e by boring, coring, or otherwise, so that when the
pin A is passed into it the ends of the wire d spring into the chamber and
prevent its return; and if two holes are bored through the sides of the tube,
diametrically opposite to each other, into the lower part of the chamber e,
the spring can be compressed through them and the castor thus withdrawn.
This pattern is specially adapted for metallic bedsteads, for shipment, as the

page_text: tube can be. formed in the leg of the bedstead and the castor can be shipped
separately, thus avoiding all risk of breakage in transit. In Fig. 17 the large
washer e, and in Fig. 18 the plate e, rivetted respectively to the pin A and the
plate C, serve to keep the castor in its place.
In the double pivot patterns illustrated by Figs. 11 to 16, inclusive, and in
the patterns shown by Figs. 17 & 18, any of the means described for retaining
the pin A in the tube C may be employed also for holding the lower pivot pin
and tube or socket together, but in some cases the axle pin of the rollers may
be conveniently employed for this purpose, as shown by Figs. 13, 16, 17, & 18,
but in the double pivot patterns, Figs. 13 & 16, the pivot pin need be nicked
on one side only, as shown at d in Fig. 13, as this pivot has to oscillate only
through small angles.
The double pivot patterns, Figs. 13 to 16, are merely modifications of each
other in which the relative order or positions of the two pins and two sockets
or tubes are varied, the lowest piece D, whether pin or socket, always being
rigidly connected to the axle pin of the rollers, whether by a "horn" clasping
a single wide roller, or by a block or boss dividing two narrow rollers, and
whether made in one with it by casting or forging, or made separately and fixed
to it by rivetting or otherwise.
For many purposes, while it is desirable that the castors should work with
the minimum of effort and as smoothly and easily as possible, there are, on
the other hand, occasions when such readiness to move may be objectionable;
for instance when a person is in the act of sitting down on a chair it is undesir-
able that the latter should run away from him. Also it is well known that
weights are sometimes put on furniture and castors greatly in excess of those
which they are intended to carry and that such weights are apt to seriously
damage the castors and render them incapable of subsequent working. To
obviate both these difficulties I use a double roller castor of such eccentricity
that the crowns of the rollers come fairly under the plate or the base of the
socket on the furniture, and I fit in the pivot tube, between the top of the
pin A and the top of the tube, a small spring of helical, volute, or other suit-
able form and of such strength that when compressed by a legitimate weight
or by the weight of the chair only the rollers are clear away from the plate
or socket, but when compressed by an excessive weight or by the weight of
a person on the chair, the plate or socket rests on the rollers themselves, so.
that there is no excessive weight on the rest of the castor and that, being
66 scotched," it cannot run away.
Three methods of carrying this out are shown in Figs. 23, 24, & 25. In
Fig. 23, h is a helical spring pressing on the bearing piece k in which the pivot a
works. In Fig. 24 the pivot a works directly in the spring h, the lower coils
of which are wound to suit the cone of the pivot. In this figure the spring
is shown compressed under abnormal weight and the plate of the castor resting
on the rollers themselves. In Fig. 25 a volute spring his shown, the central
coil of which rests on a shoulder k on the pin A, the reduced neck e passing
upwards through the spring and the washer d and being rivetted over the
latter. The tube C is chambered out to take the outmost coil of the spring
so that the latter also serves to keep the pin A in the tube, though, if pre-
ferred, of course a bearing piece can be used with this spring, as shown in
Fig. 23.
Some of the patterns of my castor, such as those shown by Figs. 4 & 5,
6 & 7, 11 & 12, 16, 17, & 18 are well adapted to be fitted to furniture by
means of either sockets, such as shown in Figs. 4 & 5, & 17, or plates, such
as shown in the remainder; others, such as those shown in Figs. 2 & 3, 8, 9,
10, 13 & 14, & 15, are better adapted to be fixed by plates, as shown, and in
these cases large screws g, such as are ordinarily employed for plate castors,
can be used, as shown in Figs. 3, 6, & 9, or plain pins 9, as shown in Figs. 11

page_text: & 16, they being fixed to the plates or tubes by any suitable method, and
the plates being further secured by small screws f.
In some patterns, such as those shown by Figs. 3, 9, 10, 13 & 15, the tube C
may be made long enough to give the castor sufficient firmness without the uso
of any pin g; and in Fig. 8 a cheap pattern is shown in which the bearing
piece c, with which the hole in the leg of the furniture is made a tight fit,-
is driven into the leg to the required distance and the plate C fixed on after-
wards by means of the screws f.
Where a large screw g is used it may be turned by means of a key fitting in
holes in the plate, as is commonly done, or by a spanner fitting a hexagon,
such as shown in Figs. 2 & 3, formed on the end of the tube C projecting
downwards from the plate, and whether it is screwed or plain it may be
held in the plate or tube by any effective method, such as that shown in
Figs. 3, 6, 9, 11, & 16, where it is put in from below against a shoulder and
rivetted from above by cutting down the angles of the square neck which
passes through the plate or the top of the tube and prevents them turning on
each other.
I am aware that double rollers and wide single rollers have already been
used and proposed for use in castors, as also vertical pivots in combination
with such rollers, and helical springs to transmit the weight of the furniture
to the castors for various purposes other than those I have described, but I
do not know of any castors having been made or proposed to be made on
and in recognition of the principle herein before described whereby wide
reaching rollers are so mounted that a slight side pressure on them, through
the furniture, easily and necessarily forces their axis to cant slightly from
the horizontal and thus largely increases the swivelling moment.
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 castors for carrying furniture and the like the use of a roller or
rollers having bearing points on the floor at some distance from each other in
the direction of their axis, together with means by which said axis, or an
equivalent line, is canted from its horizontal position when side pressure is
put on to the furniture, substantially as and for the purpose described.
2) In combination with my double roller castors, a spring arranged to
transmit the weight of the furniture to the castor, and to be compressed so
far by weight exceeding a certain limit that the furniture rests directly on
the rollers, substantially as and for the purposes described.
3) The manufacture and use of furniture castors substantially as described
with reference to the various drawings appended hereto.
Dated this 16th day of September 1890.
EDWIN C. J. DEVIS.