Anti tip shoe

A mobile storage system is provided with safety devices that increase the stability of the movable carriages. The safety devices includes shoe plates mounted to the carriages proximate each carriage wheel and above the rails. A nylon shoe is attached to the bottom of each shoe plate near the rail. The shoe plates are adjustable to position the shoe with minimum running clearances with the rails. Only a small amount of initial tipping causes the shoes to contact the rails and support a carriage against further tipping. The increased spread between the anti tip shoes compared with the spread between the wheels provides increased resistance to overturning forces by the square of the ratio of the spreads.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention pertains to safety devices, and more particularly to 
apparatus for increasing the safety of mobile storage systems. 
2. Description of the Prior Art 
The use of mobile storage systems to conserve valuable floor space in 
offices, factories, and warehouses is widespread. Mobile storage systems 
typically include movable carriages that are relatively long and high in 
relation to their width in the direction of movement along the system 
rails. Consequently, the possibility exists that, under certain extreme 
conditions, a top heavy or eccentrically loaded carriage may tip in the 
direction of motion. 
Various equipment has been developed to reduce or eliminate the possibility 
of carriage tipping. In one type of design, the longitudinal distance 
between the carriage wheels is increased to a practical maximum. The 
increased wheel spread increases the carriage stability by creating an 
increased moment arm for resisting overturning forces. 
A second type of design for preventing the tipping of movable carriages 
employs rigid interfitting members on the carriage and the system rails. 
Normally, a running clearance exists between the carriage and rail 
members. However, should the carriage start to tip, the carriage member 
contacts and is restrained by the rail member against further tipping. 
U.S. Pat. No. 4,618,191 discloses a satisfactory anti tip device of the 
second type. Although the prior anti tip designs have given good results, 
they possess certain disadvantages related to cost and manufacture. 
Overhead style anti tip devices are also known. Those designs require 
several inches of overhead space, however, which is a great disadvantage. 
Thus, a need exists for an improved design for increasing the stability of 
mobile storage system movable carriages. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, an inexpensive anti tip device is 
provided that greatly increases the safety of mobile storage systems. This 
is accomplished by apparatus that includes nylon shoes that are adjustably 
mounted to the system carriages in close proximity to the rails. 
A shoe plate is mounted over each system rail proximate each carriage 
wheel; thus, a carriage has at least four shoe plates. Each shoe plate is 
mounted to the carriage by means of a pair of fixed screws. An eccentric 
adjusting shaft adjusts the vertical location of the shoe plate on the 
carriage. A nylon shoe is attached to the lower end of each shoe plate and 
in close proximity to the rail. The adjustment feature of the shoe plates 
permits positioning the shoes very slightly above the rail. Consequently, 
the shoes will contact the rail and the shoe plates will support the 
carriage after only a very slight amount of tipping. The nylon material 
produces only a minimum amount of friction should a moving shoe contact 
the rail, and the nylon does not damage the rail. 
Other objects, aims, and advantages of the invention will become apparent 
upon reading the disclosure.

DETAILED DESCRIPTION OF THE INVENTION 
Although the disclosure hereof is detailed and exact to enable those 
skilled in the art to practice the invention, the physical embodiments 
herein disclosed merely exemplify the invention which may be embodied in 
other specific structures. The scope of the invention is defined in the 
claims appended hereto. 
Referring to FIGS. 1-3, a movable carriage 1 is illustrated that includes 
the present invention. The movable carriage is normally employed in 
conjunction with other similar carriages and fixed units in a mobile 
storage system. However, it will be understood that the invention is not 
limited to movable storage applications. 
The carriage 1 is supported for longitudinal movement in the direction of 
arrows 3 by wheels 4 and axles 6. The wheels 4 roll along parallel rails 
5. Longitudinal movement in the direction of arrows 3 may be accomplished 
by conventional manual or power means, as is known in the art. The rails 5 
are supported above the building floor 7 by a frame 9. A suitable frame 9, 
which includes leveling screws 10, is disclosed in U.S. patent application 
Ser. No. 766,249. 
As best shown in FIG. 1, the carriage 1 is relatively high in relation to 
its width in the longitudinal direction 3. As a result, under extreme 
conditions, an obstacle placed in the path of a top heavy or eccentrically 
loaded carriage may produce an inertia force 11 that causes the carriage 
to tip, as is illustrated by the phantom lines 13. 
In accordance with the present invention, the stability of a movable 
carriage 1 in the longitudinal direction 3 is greatly increased by the use 
of anti tip shoes 15. An anti tip shoe 15 is mounted to the carriage 
outboard of each wheel 4 and over the corresponding rail 5. Referring to 
FIGS. 2-4, each anti tip shoe comprises a generally rectangular shoe plate 
17. Each shoe plate 17 is mounted in a vertical orientation to the outside 
of the carriage frame 19 by means of screws 21. The screws 21 may be 
self-tapping, if desired. Large clearance holes 23 are machined in the 
shoe plates, and washers 25 are placed under the screw heads. Alternately, 
longitudinally extending slots may be employed to give vertical clearances 
around the screws. The lower end 27 of each shoe plate extends below the 
bottom of the carriage frame 19. Attached to the shoe plate lower end, as 
by a screw 26, is a nylon shoe 29. 
To adjust the position of the shoe 29 in relation to the rail 5, an 
eccentric adjusting shaft 31 is provided. The eccentric adjusting shaft 31 
includes a head 33, a shoulder 35, and a threaded end 37. The shoulder 35 
has an axis that is non-concentric with the axis of the threaded end 37. 
The shoulder closely fits within a through hole 39 in the shoe plate 17. 
The eccentric adjusting shaft threaded end 37 is received within a hole 40 
in the carriage and is retained by a nut and washer 41. 
To set the nylon shoes 29 in proper relation to the rails 5, the screws 21 
are loosened. Turning the eccentric adjusting shaft head 33 causes the 
shoe plate 17 to be correspondingly raised or lowered until the desired 
running clearance 43 is produced between the shoe and rail. The screws 21 
are then tightened. The present invention permits very small clearances 43 
to be established between the rails and shoes. Consequently, the carriages 
are positively supported after only a very small amount of initial tipping 
induced by the inertia force 11. 
Because the anti tip shoes 15 of the present invention are placed outboard 
of the wheels 4, the longitudinal spread between the shoes 29 is greater 
than the spread between the corresponding wheels. Consequently, the 
rotational resistance to carriage tipping provided by the positive 
supports of the anti tip shoes is increased over the tipping resistance 
provided by the wheels. The rotational resistance to tipping is 
proportional to the square of the distance between the shoes according to 
the formula Kr=1/2.times.Kw.times.L.sup.2, 
where Kr is the rotational resistance to tipping, 
Kw is the resistance to vertical motion at the shoes under the influence of 
the inertia force, and 
L is the distance between the shoes. 
Accordingly, a relatively small increase in spread between the shoes 
compared with the spread between the wheels can produce a relatively large 
increase in resistance to carriage tipping. As a consequence, carriage 
safety and stability are correspondingly increased. 
Thus, it is apparent that there has been provided, in accordance with the 
invention, an anti tip shoe that fully satisfies the aims and advantages 
set forth above. While the invention has been described in conjunction 
with specific embodiments thereof, it is evident that many alternatives, 
modifications, and variations will be apparent to those skilled in the art 
in light of the foregoing description. Accordingly, it is intended to 
embrace all such alternatives, modifications, and variations as fall 
within the spirit and broad scope of the appended claims.