Safety floating step assembly for platform

Safety floating step assembly for pivotal connection to platforms and the like, being self-leveling through a single pair of parallel four-bar linkages and adjustably movable to the same and different horizontal levels of position relative to the platform and to the top of different height vehicles that may be located alongside the platform and being provided with a locking mechanism for releasably locking the floating step assembly at any desired horizontal level.

BACKGROUND OF THE INVENTION 
The present invention is directed to an adjustable floating step 
arrangement for pivotal connection to platforms and the like by which 
personnel may achieve safe access to the top of various height tank 
trailers, railway tank cars, hopper cars and other carriers requiring 
access to their tops. 
In loading tanker trucks by manually handling a filling hose, for instance, 
an operator needs to reach the top of the tank of the truck, usually from 
a platfrom that may be located at a level higher or lower than the top of 
the tank of the vehicle concerned or adjacent thereto. When the operator 
attempts to step from the platform onto the top of the tank, he often 
finds the tank top to have a curved and smooth surface from which he runs 
the risk of making a misstep, thus possibly slipping and falling to the 
ground. The risk is significantly increased during inclement weather, as 
during rain, snow, sleet and freezing weather. 
U.S. Pat. No. 4,013,140 discloses one form of step construction by which an 
operator may obtain access from a platform to the top of vehicles of 
various heights, such as tanker trucks at hydrocarbon loading stations. 
The patent discloses a flight of steps, which at one end is pivotally 
connected to a platform and at the other end is adapted to be moved into 
contact with and to be supported by the top of the vehicle. The treads of 
the steps disclosed remain horizontal irrespective of the inclination of 
the steps by means of a parallelogram linkage. In constructions of the 
type represented by this patented disclosure, the multiple linkages shown 
connecting the individual steps in time tend to become rusted due to their 
exposure to the weather and thus the steps become less freely movable. 
This construction requires more maintenance to maintain free movement and 
to preclude or minimize rusting. Although tank tops are fairly sturdy, 
they can be damaged or punctured if through carelessness or accident the 
movement of the steps into contact with the tank top should be too fast or 
the operator should attempt to walk down the steps while the steps have 
not yet contacted the tank top and the weight of the operator suddenly 
forces the steps into sudden contact with the tank top. 
U.S. Pat. No. 4,013,140 discloses a collapsible step arrangement which may 
serve as a stairway or step ladder and which also employs a parallel 
linkage arrangement by which the steps may remain horizontal when in the 
opened position. This patent also discloses a latching arrangement by 
which the steps and parallel linkages may be locked in the closed or 
collapsed position to prevent unintended reopening of the step 
arrangement. 
U.S. Pat. No. 2,498,375 discloses an adjustable ladder employing a parallel 
linkage arrangement in which cams are used to lock the pivotal steps so 
that the steps will remain level at the desired adjusted inclination of 
the ladder. 
An object of the invention is to provide a safety floating step assembly by 
which an operator may have safe access from a platform to the top of the 
tanks of trucks and the like, the safety floating step assembly being 
self-supporting and independent of support by and or engagement with the 
top of such tanks. 
Another object of the invention is to provide a safety floating step 
assembly havng a single pair of spaced apart side-by-side parallel 
four-bar linkages for supporting a step assembly by which an operator may 
obtain safe access to the top of tanks from a platform or the like, and 
which has relatively few moving parts requiring maintenance. 
Still another object of the invention is to provide a safety floating step 
assembly, which is pivotally connected to and from a platform or the like 
and is provided with a locking arrangement at the location of the pivot 
for releasably locking the floating step assembly at different positions 
relative to the height of the tank of the vehicle positioned alongside the 
platform or other carrier. 
Other objects of the invention will become apparent to those skilled in the 
art to which this invention pertains when reading the disclosure that 
follows. 
SUMMARY OF THE INVENTION 
The invention is thus directed to a safety floating step assembly for 
connection to a platform that extends generally horizontally and provides 
access to the top of tanks of different height vehicles or other carriers 
that may be located alongside the platform. By "platform" it is meant any 
generally horizontally disposed structure which enables an operator to 
obtain a desired initial height with respect to the top of a tank on a 
vehicle or other carrier that will be expected to be in position alongside 
the structure for loading through the top of the tank, or cleaning the 
tank, or possibly even unloading through the top of the tank. The 
"platform" could also be the floor of a building adjacent to an access 
made through the wall of the building with the floating step assembly 
being pivotally connected to the wall of the building but still located 
adjacent such floor. 
The floating step assembly is self-leveling and is adjustably movable to 
the same and different horizontal levels of position relative to the 
platform. It is pivotally connected to the platform by a shaft that is 
rotatably supported by the platform. A pair of parallel four-bar linkages 
is secured at one end to the shaft, and at least one step is operatively 
supported by and from the parallel four-bar linkages at their other end. 
The pair of parallel four-bar linkages includes a pair of main support arms 
that are connected to the shaft for rotation therewith within parallel 
planes that project generally at right angles relative to the horizontal 
surface of the platform. The main support arms have extending beyond the 
end of the platform portions between which a second shaft is connected. 
The second shaft serves to provide part of the support for suspended 
pivotal movement therefrom of the step from such outer portions of the 
main support arms. 
A first pair of spaced-apart support members is fixed to the platform and 
projects at right angles from and above the surface of the platform a 
predetermined distance; and a second pair of spaced-apart support members 
is fixed to either side of the suspended step and projects at right angles 
from and above the step to the same relative predetermined distance as the 
first pair of spaced-apart support members. 
A pair of link members is pivotally connected to and between the upper end 
portions, respectively, of the first and second pair of spaced-apart 
support members. Each link member is parallel to one of the main support 
arms and remains parallel in any position assumed by that one main support 
arm. 
A locking arrangement is provided for the floating step assembly by which 
the floating step assembly may be releasably locked at any desired 
horizontal level, and especially to be securely locked against unintended 
further downward movement while the operator is standing on the step. The 
locking arrangement involves mounting a toothed gear on and securing to 
the first-mentioned shaft on which the main support arms are pivotally 
conneced to the platform. A pawl is releasably biased into selective 
locking engagement against any selected one of the teeth of the toothed 
gear, and a movable shipper is adapted to be manually actuated by the 
operator to disengage the biased pawl from such selective locking 
engagement when the operator has stepped back onto the platform. The pawl 
cannot be released while the operator is standing on the step because the 
amount of friction and moment of force exerted on the pawl by the operator 
when standing on the step would be too high to be manually accomplished. 
The safety floating step assembly may be provided with counterbalancing 
weights at the innermost end portions of the main support arms, or a 
constant torque spring motor arrangement may be connected to the 
first-mentioned shaft by which the main support arms are pivotally 
mounted. 
Each of the main support arms is preferably provided with a fixed annular 
hub about intermediate the length of the main support arm, and an 
arrangement is interposed between the interior surface of each of the 
annular hubs and the exterior surface of the first-mentioned shaft for 
frictionally radially clamping the main support arms to the 
first-mentioned shaft for initial alignment of the step relative to the 
platform and of the main support arms with each other.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
In reference to the drawings, the safety floating step assembly 10 is 
connected to shaft 12 for pivotal movement therewith, the shaft being 
supported for rotative movement by platform 14. Shaft 12 is of sufficient 
diameter and strength so as to withstand the torque produced by the moment 
of force that will be exerted upon it when an operator is standing upon 
the step 16 that is at a cantilevered position with respect to the shaft 
and platform. 
The step 16 is supported for movement to different horizontal levels of 
position by a pair of parallel four-bar linkages 18, which include a pair 
of parallel, spaced-apart main support arms 20 which are connected to the 
shaft 12 for rotation therewith within parallel planes that project 
generally at right angles relative to the horizontal surface of the 
platform; and a first pair of spaced-apart support members 22 fixed to the 
platform and a second pair of spaced-apart support members 24 fixed to 
either side of the step 16. The first pair of spaced-apart support members 
22 project at right angles from and above the surface of the platform a 
predetermined distances, and the second pair of spaced-apart support 
members 24 project at right angles from and above the surface of the step 
16 to the same relative predetermined distance as the first pair of 
spaced-apart support members 22. A pair of link members 26 is pivotally 
connected to and between the upper end portions, respectively, of the 
first and second pair of spaced-apart support members 22, 24, with each 
link member being parallel to one of the main support arms 20 and 
remaining parallel thereto in any position assumed by that one main 
support arm. The step 16 is pivotally suspended in part from the first and 
second pair of spaced-apart support members and the link members. 
Each main support arm 20 has about intermediate its length an annular hub 
28 fixed thereto. The annular hub is adapted to mount the main support arm 
upon the shaft 12, and a locking assembly 30 is interposed between the 
interior surface of the annular hub and the exterior surface of shaft 12 
for frictionally radially clamping the main support arm to the shaft 12. 
The locking assembly, which is partially illustrated, may be of the type 
that is made by the Ringfeder Corporation in Westwood, N.J. It is a 
frictional, keyless shaft-hub locking device that provides an easily 
adjustable and releasable mechanical shrink fit. Torque or axial loads are 
transmitted by radial clamping pressures and friction between the 
functional contact surfaces of the locking assembly, shaft and hub. In 
other words, the locking assembly exerts contact pressures on both the 
shaft surface and the hub bore. The locking assembly is provided with 
socket head cap screws 32 which are tightened by a torque wrench, and 
double tapered thrust rings 34, 36, which are pulled toward each other to 
exert predetermined radial clamping pressures on slit inner and outer 
rings (not shown). Disassembly is accomplished by simply releasing the 
locking screws 32. By use of this locking assembly, the main support arms 
can be readily and precisely aligned with each other. Also the step may be 
initially aligned level with the platform. Thus also, torque and axial 
loads will be safely transmitted regardless of whether or not the main 
support arms are subjected to static, dynamic or impact loads. 
The main support arms 20 may be provided at one end with counterbalancing 
weights 38 and at the other end, where the portions of the main support 
arms extend beyond the end of the platform 14, a second shaft 40 extends 
between the portions and from which step 16 is pivotally suspended in 
part. The second shaft 40 provides increased stability for the step 16. 
A releasable locking arrangement in the form of a pawl and ratchet 
mechanism or ratchet device, such as made by Lowell Machinery Component 
Division in Worchester, Massachusetts, is provided for the floating step 
assembly and includes a toothed gear 42 which is keyed to shaft 12; a 
spring-biased pawl 44; a housing 46 for the toothed gear and spring-biased 
pawl; a shipper 48 which is pivotally movable within the housing 46 for 
movement against the spring-biased pawl to disengage it from its locking 
engagement with one of the teeth of the toothed gear; and an actuating arm 
50 which is pivotally connected to the outer end of the shipper that 
extends outside the housing 46. The actuating arm 50 is urged into an 
inoperative position by spring 52, which at its one end presses against a 
collar 54 mounted on the actuating arm 50 and at its other end may press 
against a handrail 56 fixed to the platform 14. Collar 55 limits downward 
movement of the actuating arm. The actuating arm 50 extends through the 
handrail 56. 
The releasable locking arrangement enables an operator to lock the floating 
step assembly at different horizontal positions which may be above the 
platform, below the platform or at the same level of the platform. 
OPERATION 
In operation, the step 16 may be released for movement to different 
positions when the operator with one hand pulls upwardly on the actuating 
arm against its spring-bias and with the other hand grasps the handle 60, 
which is pivotally connected to one of the main support arms 20 and serves 
to manually control the movement of the floating step assembly. This 
upward pull is transmitted to the shipper for subsequent disengagement of 
the pawl from one of the teeth of the toothed gear. The step, as may be 
noted from FIG. 1, may be moved along an arcuate path until it comes into 
abutment against a stop member 58 which is attached below the platform, or 
in abutment against the vertical support 62 for the handrail 56. Upon 
releasing the actuating arm, the pawl is automatically biased into locking 
engagement with one of the teeth of the toothed gear 42. When the operator 
steps from the platform onto the step 16, the ratchet device prevents the 
step from unintendedly moving downwardly under the weight of the operator. 
In the arrangement of the ratchet device illustrated, the spring-biased 
pawl 44 prevents the toothed gear 42 from rotating in one direction, but 
the toothed gear may be free to rotate in the opposite direction if the 
operator wants to move the step 16 to a higher level. If desired, however, 
a second pawl (not shown) may be disposed on the other side of the shipper 
48 from the first pawl to prevent movement in the aforementioned opposite 
direction without first releasing the locking arrangement. 
ALTERNATIVE EMBODIMENT 
In reference to FIG. 5, the shaft 12' may have a constant torque spring 
motor 70 suitably attached thereto, as illustrated, instead of the main 
support arms 20 being provided with the counterbalancing weights 38, as 
illustrated in FIG. 1. The one end of the spring motor is connected to 
shaft 12' and the opposite end of the spring motor is connected to shaft 
72. 
One example of a constant torque spring motor would be the Ametek Neg'ator 
constant torque spring motor, made by the Hunter Spring Division of the 
Ametek Company. 
SUMMARY 
The floating step assembly as disclosed has a rather simplified 
construction of fewer moving parts as compared to some of the prior art, 
thus requiring less maintenance. The construction, however, is rugged 
enough to serve the purposes intended; it is safe to use; easy to unlock 
for movement to different horizontal levels; and automatically locks upon 
release of the actuation lever. The step is self-leveling and can be 
adjusted in increments by means of the ratchet device so as to be spaced 
as close to and above the top of the tank of a vehicle as desired, and yet 
remain out of contact with such tank top without requiring support from 
the tank top. 
The invention has been described in detail with particular reference to 
preferred embodiments thereof, but it will be understood that variations 
and modifications can be effected within the spirit and scope of the 
invention.