Caster with braking mechanism

Rolling and swiveling movements of a caster are simultaneously braked by a movable brake member which extends between the forked legs of the caster and has one end downwardly movable into frictional contact with the tread surface of the caster wheel and another end downwardly movable into frictional contact with an upwardly-facing annular surface on the non-swiveling base of the caster. The brake member is moved to its braking position by a lever-actuated pin concentric with the swivel axis.

BACKGROUND AND SUMMARY 
This invention relates to casters and concerns in particular the braking 
device for casters for carts, wagons and the like used aboard 
passenger-carrying vehicles such as jet planes, railroad cars and ships. 
A conventional caster consists of a rotary thrust bearing secured to the 
cart, a wheel for rolling on the floor, and a generally curved fork 
connected to the thrust bearing and holding the wheel axle by its 
bifurcated ends. The fork and wheel as one are capable of swiveling motion 
around the center of rotation of the thrust bearing. Means are also 
provided for braking the wheel. The fork is so curved that the wheel axis 
is not directly under the center of the bearing but is offset therefrom. 
Due to this offset relationship, movement of the cart causes the fork to 
swivel to turn and bring the wheel to the trailing side of the cart. There 
is, however, no means of braking this swiveling motion. 
When a cart equipped with conventional casters is in service aboard an 
airliner, and is at standstill in braked condition, its casters are all 
oriented in a direction on the trailing side of the previous direction of 
cart movement. When the plane banks, the cart experiences a push exerted 
by by the floor and, depending on the direction of this push relative to 
the orientation of the casters, the casters may swivel to reorient 
themselves, causing the cart to jog or jolt. When the plane rocks or 
pitches, the cart may shake or sway to and fro, forcing the articles on it 
to rattle or even spill liquid contents. The present invention purports to 
prevent such jogging, jolting and shaking motions of the cart by providing 
a novel means by which a braking force can be simultaneously applied to 
the wheel and to the thrust bearing. 
According to the present invention, a caster is provided with a brake 
member which extends between the forked legs of the caster and serves 
simultaneously to brake the caster wheel and oppose the swiveling tendency 
of the caster fork. The brake member has one end for frictionally engaging 
the caster wheel to prevent rolling movement and another end for 
frictionally engaging an annular surface attached to the caster base to 
prevent swiveling movement. An actuator is provided for moving the brake 
member to and from its braking position. 
The details of the braking device according to my invention will be made 
clear from the preferred embodiment thereof described below and 
illustrated in the attached drawings.

DESCRIPTION OF A PREFERRED EMBODIMENT 
Referring to FIGS. 1, 2 and 3, a rotary thrust bearing is of the ball type 
and has two circular rows of steel balls 2 and 4 and five concentric 
elements described below, each having a circular hole at its center. These 
elements are: a base 1 to be bolted or otherwise secured to the horizontal 
bottom face of a cart or other body, a first retainer 3 located 
immediately under base 1 and provided with a race for the row of steel 
balls 2, a fork 7 having two legs secured rigidly to retainer 3, a ring 12 
attached rigidly to the underside of the rim of base 1 and having an 
annular groove 13 in its outer edge, said goove being horizontal and 
opening out radially, a flanged vertical bushing 6 filling the center hole 
space formed by the base 1 and the retainer 3 to rest on and depend from 
the base 1 by its top flange, and a second retainer 5 located under the 
retainer 3 and resting on the bottom flange of the bushing 6. Retainer 5 
provides a lower race for the row of steel balls 4. 
With the exception of bushing 6, the above-named concentric parts are 
generally flat in section and stacked in such a way that the weight of 
vertical loads thereon, acting on the base 1, are transmitted downward 
through the balls 2 and the retainer 3 to the fork 7 whose legs carry the 
bolt and nut assembly 9 which provide the wheel shaft. The second retainer 
5 with the balls 4 facilitates the rotary or swiveling motion of the first 
retainer 3 and helps maintain the concentricity between the retainer 3 and 
the base 1. Bushing 6 supports the second retainer 5 by its flange and 
serves another purpose described below. 
As seen in FIG. 1, the flanges of bushing 6 have beveled mating faces but 
these faces may have other shapes. It is desirable that the inside 
diameter of the bushing 6, providing a vertical passage 6A, be relatively 
large; and that the annular groove 13 is deep enough to present a wide 
upwardly facing annular surface 13A. 
As seen in FIGS. 1, 2 and 3, a brake member 11 is a flat strip-like piece 
with parallel sides, curled over to enter the annular groove 13 at one 
end. Brake member 11 extends under the thrust bearing and between the two 
legs fo fork 7 with small side clearances. An end portion 11A of member 11 
overlies the tread surface of caster wheel 8, and is preferably provided 
with a friction lining on its underside. A cylindrical round pin 10, 
located in the bore of the bushing 6, has its top end held down by a lever 
arm 14 and its bottom end affixed to the brake member 11. As shown in FIG. 
2, the lever arm 14 extends above pin 10 and projects laterally beyond the 
thrust bearing in such a way that the outer end can be moved up and down. 
A hinge or fulcrum is provided at an intermediate point lengthwise of the 
arm 14 by pivot pin 15. When the outer end of the lever arm 14 is pulled 
up, a downward push will be exerted on the pin 10 with a mechanical 
advantage dependent on the leverage. The fulcrum arrangement is not 
limited to the hinge-like construction using the pin 15 but can be devised 
differently according to any known method. 
When the lever 14 is moved to exert a downward push on pin 10, the pin 10 
moves end portion 11A of the brake member 11 downwardly from a retracted 
position to an engaged position where it frictionally bears on the tread 
surface of wheel 8. At the same time, end portion 11B of brake member 11 
is moved from a retracted position to an engaged position where it 
frictionally engages against the upwardly facing annular surface 13A of 
the groove 13. Thus, the end portion 11A directly brakes the wheel 8. 
Frictonal engagement between the end portion 11B and surface 13A prevents 
the member 11 from being turned by the two legs of fork 7. Since the fork 
7 is integral with the first retainer 3 of the thrust bearing, the 
friction produced by the lever action of the arm 14 at the end portion 11B 
has the effect of indirectly braking the swiveling tendency of the thrust 
bearing. 
When an airline food and beverage service service cart is fitted with four 
casters constructed according to this invention, there are four lever arms 
14. A single control lever connected to any suitable external linkage may 
actuate these four arms in the manner explained above, in order to effect 
the double-action braking simultaneously on all four casters. 
The lever arm 14 and the pin 10 may be engaged inseparably or left 
unengaged but kept in contact with a spring for urging the brake member 11 
toward the arm 14. The legs of fork 7 along the sides of shoe 11 should be 
sufficiently wide in order for the fork 7 to experience a large resistance 
to swiveling torque when the caster is subjected to reorientation forces. 
The lengths of the end portions 11A and 11B should be proportioned to give 
an appropriate balance of frictional forces at end portions 11A and 11B, 
to produce the desired double-action braking. The brake shoe 11 is shown 
in FIGS. 1-4 as a strip-like piece with a uniform width but, in order to 
obtain a larger frictional contact area relative to the bottom side face 
13A of groove 13, may be shaped arcuately to form end portion 11C as shown 
in FIG. 5 
It will be seen from the foregoing description that the braking device 
according to this invention permits the caster as a whole to be 
frictionally braked merely by operating lever arm 14 to prevent the caster 
from rolling and swiveling when an external force, due mainly to gravity, 
acts on the cart. Specifically, a service cart or wagon fitted with the 
casters of this construction can be readily and effectively restrained and 
made to stand solidly on a tilting, pitching or rocking floor so that when 
used to serve passengers in a jet plane, for instance, the flight 
attendant need not restrain the standing cart at each stop along the 
aisle. This frees the attendant's hands for handling articles on the cart, 
and prevent the spillage of liquid and the bouncing and rattling of the 
cart and its contents. 
Persons familiar with this art will realize that the invention may be 
practiced by many devices other than the specific embodiment disclosed 
hereinabove. For example, the ball bearing may be eliminated from the 
thrust bearing and a wide variety of actuating devices may be used. 
Therefore, it is emphasized that the invention is not limited solely to 
the disclosed embodiment, but is encompassing of modifications thereto and 
variations thereof falling within the spirit of the following claims.