Exercise stair device

Apparatus which simulates the exercise obtained while climbing stairs includes two hydraulically phased steps retained in adjacent inclined tracks in which the steps are supported in a hydraulically open-ended system, with the phasing of the steps being controlled by a pair of in-line hydraulic actuators, one each associated with a step, in which fluid forced from one actuator with a downward movement of the associated step is channeled through a variable restricted orifice to the other actuator to raise the other step. In one lightweight, compact embodiment, the device is collapsed down to a compact size through the use of steps which are foldable to the track, and through the use of a track foldable to the frame. In its open position the lower portion of the frame props up the track at an appropriate climbing angle, with upper portions of the frame extending above the track to serve as handles positioned above the center of travel of the steps.

FIELD OF INVENTION 
This invention relates to exercise devices and more particularly to an 
exercise stair which simulates the exercise encountered during the 
climbing of stationary stairs. 
BACKGROUND OF THE INVENTION 
One exercise device which simulates the exercise encountered during the 
climbing of stationary stairs is described in U.S. Pat. No. 3,970,302, 
issued to Richard McFee. In this exercise device, moveable steps are 
provided on an inclined track, with the counterforce being provided 
hydraulically, in one case by actuation of a hydraulically damped variable 
pivot lever and in another case by a hydraulic motor. In both of these 
cases, the steps are moved in opposition or phased mechanically such that 
when one step is moved downwardly by the weight of an individual, the 
other step is moved upwardly. In the McFee patent, the mechanical phasing 
of the steps is accomplished by a wire or chain from one stair to the 
other over a pulley or hydraulic motor sprocket. The mechanical phasing 
assures that when one step goes up by a predetermined amount, the other 
step will come down by this predetermined amount. It should be noted 
however that should the wire or chain break, the steps are unsupported and 
an individual can fall off the device. As will be appreciated, mechanical 
phasing results in a large number of moving parts and mechanical linkages 
which are noisy, cumbersome and expensive. Moreover, both the pivoted arm 
embodiment and the hydraulic pump embodiment of the McFee patent are 
difficult to implement because they do not accommodate the expansion of 
the hydraulic fluids occasioned by temperature increases associated with 
use, as energy expended by the user's efforts is absorbed. Also 
significant backlash accompanies use of these two embodiments which is 
annoying. Moreover, in the pump embodiment it is extremely difficult to 
provide a pump which acts symmetrically in both directions. Additionally, 
neither of the two McFee embodiments allow for compact packaging because 
the phasing apparatus is bulky and in one embodiment is accomplished by a 
large number of mechanical parts not conveniently housed in a flat package 
which would permit compact storage and ready portability. 
Additionally, in any conveniently sized pivoted arm embodiment, to adjust 
the counterforce by 5% for a 100 lb. person corresponding to a change in 
climbing rate from 60 ft. per minute to 63 ft. per minute, the fulcrum of 
the pivoted arm is to be changed by less than 1/8 inch, which is virtually 
impossible to do. This severely limits repeatability of the counterforce 
setting and the ease with which the counterforce can be varied. 
Repeatability of the counterforce setting is important because exercise 
regimens specified by exercise physiologists often progress in intensity 
from one week to another by increments of only 5% or less. 
It will, however, be appreciated that the device described in the 
above-mentioned patent has advantages over other types of exercise devices 
such as rowing machines, stationary exercise bicycles, and endless belt 
walkers. 
By way of further background, with respect to exercise bicycles, these 
devices rely on a pedal driven wheel and either a roller or brakes for 
providing the counterforce. The problem with these types of exercise 
devices is the extra amount of effort necessary to start the wheel moving 
from a dead stop. Moreover in the case of brakes, after the static 
coefficient of friction has been overcome, the brake pads or strap provide 
relatively little counterforce. Thus, adjustment of such a device is 
difficult. 
Aside from getting the wheel started, in all of the above-mentioned 
devices, the amount of counterforce is not readily adjustable and is 
non-linear. More specifically, the above-mentioned exercise cycles are to 
a certain extent speed sensitive in that the counterforce applied to the 
reaction part actuated by the user is speed dependent. For instance in the 
exercycle, the counterforce lessens substantially as the user exercises 
since the heating up of the friction pads results in a decreased 
coefficient of friction during exercise. This is also true for the 
resilient rim exercycles in which the roller forms a standing wave which 
makes the exercycle easier to pedal. 
By way of further background, perhaps one of the more important problems in 
terms of home use exercise devices is the noise and vibration associated 
with these devices. When these devices are utilized in apartments, for 
instance, the noise and vibration can be so significant that the user is 
required to forego the use of the exercise device due to the annoyance it 
causes neighbors. Moreover, if the user prefers to watch television or 
listen to radio during exercise, the exercise device is sometimes so noisy 
that it drowns out either the television or the radio. In all of the prior 
art devices mentioned above, there are a plurality of mechanical parts and 
mechanical linkages which are inherently noisy. For instance, bike chains, 
rollers and pivoted levers are amongst those mechanical devices which 
create considerable noise during operation. 
SUMMARY OF THE INVENTION 
The subject device is an all-hydraulic, quiet exercise stair device having 
a pair of steps which move in opposition along an inclined track. The 
steps are linked together hydraulically in an open-ended system in which 
the fluid from one hydraulic actuator supporting one step is metered 
through a variable orifice metering valve to the actuator for the other 
step and visa-versa so that the rate at which the steps may be actuated is 
infinitely and linearly variable by controlling the flow rate from one 
actuator to the other. The subject device has the advantages of 
repeatability and easy adjustability of flow rate which sets the speed, 
gentle failure mode, permits fluid expansion, low noise and compactness. 
It is a feature of this hydraulic system that restricting the orifice 
decreases the flow rate which increases the time for a step to descend 
with a given body weight. This means that the exercise rate is slower and 
therefore the equivalent climbing rate is slower. To obtain more exercise, 
the orifice is opened to permit more rapid stair climbing. This means that 
the number of step actuations per minute may be increased, and in fact can 
be increased to such an extent that it is equivalent to running up stairs 
or a slope. Thus, aerobic exercise is increased with an increase in the 
orifice of the metering valve, thereby increasing heart rate, respiration 
rate, and resultant caloric burn-off. The system thus controls the maximum 
rate at which a user may exercise in a very convenient fashion. 
Moreover, the increased volume of hydraulic fluid that occurs as a result 
of the increased temperature during exercise is accommodated by a rise in 
the position of the steps. Thus, the present invention accommodates 
thermal expansion of the hydraulic fluid during exercise without special 
valving, accumulators or additional cooling elements since expansion of 
the fluid merely increases the step height. 
As important, the steps are phased hydraulically rather than mechanically. 
The use of the totally hydraulic system without mechanical phasing results 
in an exceptionally quiet, simple system. Moreover in its failure mode, 
the subject device deposits the individual gently to floor level as 
opposed to abruptly dropping him. 
The hydraulic actuator utilized to support the stairs or steps may employ 
either a hydraulic ram or a piston cylinder. The hydraulic ram has only 
one seal, namely the rod seal, as opposed to a rod seal and a piston seal 
used in a piston cylinder. The use of hydraulic rams avoids internal 
leakage problems associated with piston seals because no piston seal is 
used. Moreover, the hydraulic ram is lower in manufacturing cost. With 
respect to external leakage in open-ended systems, hydraulic rams are 
preferable because low cost piston cylinders invariably leak oil which can 
damage carpeting or rugs. 
In one embodiment, the hydraulic cylinders are flexibly mounted to a base 
plate and are provided with a flexible interconnection between the end of 
a hydraulic cylinder and the metering valve, such that the actuator rods 
in the hydraulic cylinders may move off-axis without side forces on the 
rod seal. The main purpose of the flexible mounting is to eliminate side 
forces on the rod seal. Elimination of side loading greatly enhances rod 
seal life and avoids leaks. Since leaks are a major fault mode of 
hydraulic systems, this is an important product life factor. The 
reliability of this type mounting system also increases the safety of the 
device as well as the longevity of the hydraulic actuators. 
The compactness and stowability of the subject exercise stair in one 
embodiment is due in part provided by in-line, hydraulic cylinders carried 
totally within the track so as to achieve a flat package. Additionally, 
for storage the steps are foldable to the track and the track is folded to 
a frame to which it is hinged. The lower portion of the frame serves to 
prop up the track at a predetermined angle, with upper portions of the 
frame extending above the track serving as handles. In a preferred 
embodiment the handles are telescoping and are positioned above the center 
of travel of the steps. Various frame/track folding methods are described 
hereinafter. 
When not in use, the frame is pivoted or swung to a point parallel to and 
flush with the track. In one embodiment, the steps are folded down to the 
plane of the track such that the entire device may be conveniently stowed, 
especially under a bed. With the frame swung into place parallel to the 
track, wheels on the frame contact the floor such that the entire device 
may be moved wheelbarrow fashion. 
While the subject exercise stair is extremely quiet in operation due to the 
simplicity of its operation, the exercise stair can be made even quieter 
through the utilization of oil-impregnated wooden skids for the steps 
instead of the rollers used in the aforementioned McFee patent. In one 
embodiment the oil-impregnated wooden skid is 60% oil by weight.

BRIEF DESCRIPTION OF THE DRAWINGS 
These and other features of the subject invention will be better understood 
in connection with the detailed description taken in conjunction with the 
drawings of which: 
FIG. 1 is a diagrammatic illustration of the subject exercise stair 
illustrating hydraulic phasing and the hinged frame configuration; 
FIG. 2 is a schematic illustration of a prior art system for phasing stairs 
illustrating a mechanical phasing technique; 
FIG. 3 is a schematic illustration of the hydraulic system utilized for 
mechanical phasing of the stairs of FIG. 1; 
FIG. 4 is a schematic illustration of the hydraulic phasing system of FIG. 
3, illustrating the direction of the counterforce provided for the 
actuator coupled to the stair which is moving downwardly; 
FIG. 5 is a diagrammatic illustration of the stair track illustrating the 
hydraulic actuator support for the stair steps and flexible base pivots 
for the actuators; 
FIG. 6 is a diagrammatic illustration of the flexible joint for the base of 
the actuator of FIG. 5; 
FIG. 7 is a side view of the exercise stair showing the folding of the 
frame to the track and also illustrating the collapse of the steps to a 
position flush with the track; 
FIG. 8 is a diagrammatic illustration of the storage of the subject 
exercise stair underneath the bed in its folded or collapsed condition; 
FIG. 9 is a side view of the subject exercise stair illustrating in 
phantom, the swinging of the frame away from the track; 
FIG. 10 is a diagrammatic illustration of a portion of the track and a 
portion of the frame in their assembled position; 
FIG. 11 is a diagrammatic illustration of an alternative track folding 
method; 
FIG. 12 is a diagrammatic illustration of a still further track folding 
method; 
FIG. 13 is a diagrammatic illustration of the positioning of a carrying 
strap on one side of the track to facilitate carrying; and, 
FIG. 14 is a diagrammatic illustration of an alternative hydaulic phasing 
system using rods in tension and piston seals as opposed to rods in 
compression and rod seals. 
DETAILED DESCRIPTION 
In order to provide for an exercise device in which the counterforce to the 
individual is easily controlled and referring now to FIG. 1, in one 
embodiment an exercise stair 10 is provided with a dual track 12 and a 
frame 14 which is double-hinged at 16 and 18 with a hinge strap 20 such 
that the assembled exercise device takes on an A-frame configuration with 
an inclined track 12 and an inclined frame 14. 
Extensible arms 22 and 24 are telescoped from the upper porttions 26 and 28 
of upstanding frame members 30 and 32 such that the handle portions 33 are 
positioned above the tracks preferably at the midpoint in the travel of 
the steps in their tracks. A bottom cross member 34 is provided to 
complete the bottom of the frame, whereas a horizontal spacing member 36 
is provided at a point adjacent hinge point 18, yet far enough from the 
track to prevent pinching if spacing member 36 is held during opening of 
the device. The bottom of the frame is provided with wheels 38 as 
illustrated. 
Inclined track 12 is provided with tracks generally indicated at 40 and 42. 
Channels 44 and 46 in respective tracks house carriages 50 and 52. Steps 
54 and 56 are mounted to carriages 50 and 52 respectively, with the 
carriages being supported hydraulically by in-line, full stroke hydraulic 
actuators 58 and 60. 
Actuators 58 and 60 are connected hydraulically at their bases by an 
adjustment or metering valve 62 which controls the counterforce to the 
individual, here illustrated in dotted outline at 64, as the individual 
shifts his weight to a step which is to be moved downwardly. As will be 
described, in one embodiment carriages 50 and 52 are mounted for 
reciprocation within their respective tracks in a sliding fit. 
In operation, the individual utilizing the exercise stair steps down on one 
step which offers resistance to the individual's weight in accordance with 
the setting of valve 62. When the step associated with this downward 
pressure reaches its lower limit, the individual then shifts his weight to 
the upper step and the process is repeated such that the equivalent of 
stair climbing exercise is achieved. 
As mentioned hereinbefore, the phasing of the steps, that is the movement 
of one step relative to the other, is achieved completely hydraulically 
with no mechanical phasing of the steps involved. Referring to FIG. 2, in 
the prior art steps 70 and 72 are mechanically linked together by a cable 
or chain 74 which runs over a pulley 76 such that as one step descends, 
the other moves up to the exact extent that the opposing step moves down. 
It has been found that it is not necessary to obtain the feel of stair 
climbing, that one step move up precisely by the same amount that the 
other step moves down. This permits complete hydraulic phasing of the 
steps such as illustrated in FIGS. 3 and 4, and also provides an extremely 
quiet exercise device. 
Referring to FIG. 3, in a preferred embodiment each actuator is a hydraulic 
ram as opposed to a piston cylinder which has both piston seals as well as 
rod seals. Each ram is a rod 78 mounted for translation in a cylinder. 
Note that the only sealing is that which is accomplished at the top of the 
actuators by rod seals 82 as illustrated. The rod seals are preferable to 
piston seals because rods can be inexpensively manufactured to tighter 
tolerances than can the inside dimension of a conventional hydraulic 
cylinder to which a piston is sealed. While it is possible to utilize 
conventional hydraulic cylinders with piston seals at the lower ends of 
the rods, e.g. piston cylinders, in an open-ended system it has been found 
that piston seal leakage can occur which results in exterior oil leakage 
and loss of stroke and phasing. For closed systems if piston seal leakage 
occurs, stroke and phasing can be restored by use of a bypass involving an 
additional circuit and valve to return the fluid to the proper side of the 
piston. 
It will be appreciated that that which produces the hydraulic pressure is 
the end of the rod which is the only surface of the actuator on which the 
fluid works. Referring to FIG. 4, when a force is applied to the rod in 
actuator 60 by virtue of the weight of the individual applied to step 56, 
a counterforce f(v) acts against end 80 of the rod within actuator 58. 
This flow rate is dependent upon the pressure across variable orifice 84 
in which the pressure P.sub.1 to the left of this orifice is greater than 
the pressure P.sub.2 at the time that the force f is applied to rod 78 in 
actuator 58. 
With respect to actuator 58, at the time force is applied to actuator 60, 
rod 78 in actuator 60 will be in its lower position. In terms of the 
operation of the device, when the individual shifts his weight to step 56, 
there is no weight applied to step 54 and therefore there is no back 
pressure across orifice 84 assuming that step 54 is completely unweighted. 
With step 54 unweighted, the rod within actuator 60 moves in the direction 
of arrow 86, but moves upwardly slightly more slowly than step 56 
descends. There is thus a certain very small time lag in the rise of step 
54 with the descent of step 56. It is however a finding of this invention 
that this time lag is not significant since the user does not particularly 
care what the unweighted step does as long as it moves upwardly at some 
time prior to the time that the user wishes to shift his weight to this 
step. This being the case, it is not necessary to utilize mechanical 
phasing in order to satisfy the user's need for realistic stair climbing 
experience. Note that there is a cushioning air bubble 87 at the top of 
each actuator to damp sharp hydraulic forces which may be applied to the 
end of the actuator rod by stamping on a step. 
As the exercise stair is utilized, energy is imparted to the hydraulic 
fluid within the actuators. Under ordinary circumstances it is necessary 
to accommodate the expansion that is built up by the energy imparted to 
the fluid. However, as illustrated in FIG. 3, when heat is added to the 
hydraulic fluid, since the system is hydraulically open-ended, the 
expansion of the fluid with heat results only in a rise in the position of 
each of the steps as illustrated by dotted outlines 90. The position of 
each of the steps will rise identically and is caused by an identical 
extension in the positions of rods 78 as illustrated at 92. 
Because of the open-ended hydraulic system, the amount of counterforce 
provided by each step does not vary perceptibly during use even though a 
considerable amount of energy is added to the system. All that occurs with 
extended use is a simultaneous rise in the position of the steps. The 
resulting expansion of stroke is no problem to the user and it does not 
effect the exercise rate which is essentially a function of the rate of 
flow through orifice 84. 
The advantages of the total hydraulic open-ended system are the resolution 
with which the climbing rate can be adjusted by valve 62, the 
repeatability of the exercise rate with the setting of valve 62, and the 
uniformity of the counterforce provided by the system. The rate at which 
the weight is shifted by the individual in the stair climbing exercise 
does not affect the counterforce to any perceptible degree and thus the 
subject exercise device is speed independent. The exercise variable is 
solely the size of the restricted orifice as dictated by valve 62 which 
sets the maximum rate at which the exercise can be performed, all other 
parameters being equal, such as the size of the rods, viscosity of fluid 
over the operating temperature range, and the volume of the actuators. 
Additionally, the force necessary to move a step downwardly is uniform over 
the exercise cycle and there is no starting friction to be overcome. Thus 
exercise may take place smoothly and at a uniform rate unlike most prior 
art devices. 
With respect to safety, the most likely failure mode of the subject 
exercise device is either fluid leakage around the seal, a rupture of the 
actuator, or a rupture of the interconnect lines 94 and 96 between 
actuators 60 and 58 and valve 62. Upon rupture of any of these lines or 
actuators, the result is the movement of the steps downwardly but at a 
controlled rate. The rate is sufficiently slow to deposit the individual 
at the bottom of the tracks without harm. 
TRACK/STEP DETAILS 
Referring now to FIG. 5, a detailed cut away view of dual track 12 is 
illustrated in which like reference characters are utilized for like 
elements as between FIG. 1 and FIG. 5. With respect to the individual 
tracks 40 and 42, the bottom portion of the track is made up of a plate 
100 which forms the back portion of the track. Channels 102 are mounted to 
plate 100 such that they are open to each other in pairs as illustrated, 
and carriages 50 and 52 are mounted in the tracks formed in this manner. 
In one embodiment each carriage includes a double-plate configuration in 
which plates 101 and 103 are mounted in spaced-apart adjacency. The 
carriage has a rounded head portion 104 and rounded bottom corners 106. 
This double-plate frame is mounted to skids 108 and 110 on either side 
thereof, with the skids mounted in a sliding fit to the respective track. 
In a preferred embodiment the skids are made of oil-impregnated wood to 
eliminate noise associated with systems which use rollers. As mentioned, 
the oil-impregnated wooden skid is as much as 60% oil by weight. 
Actuator 58 is mounted such that a top portion 112 extends through the 
double-plate structure in a slot (not shown), with the associated rod 78 
being attached at 114 to the top portion 104 of carriage 52. Because of 
the double-plate configuration of the carriage, as illustrated by carriage 
50, a major portion of the body of actuator 60 can extend to the interior 
of the carriage as this carriage is moved downwardly. Thus, the actuator 
can be made relatively thin and relatively long. In one embodiment the 
actuator has an inside diameter of 22 mm, with a rod having an outside 
diameter of 10 mm, the length of the actuator being 18 inches and the 
length of the rod being 15 inches. 
Base 112 of each actuator is mounted to a base plate 114 in a flexible 
joint generally indicated at 116, so as to accommodate off-axis movement 
as illustrated by dotted line 118. Each of the connecting lines between 
the actuators, here illustrated at 120 and 122, has an intermediate 
flexible linkage 124 so as to accommodate the off-axis movement of the 
actuators. This flexible connection is illustrated in greater detail in 
FIG. 6. 
Referring to FIG. 6, the base of actuator 60 is provided with an annular 
groove 130 in which is located a C-ring 132 which limits the upward 
movement of a rigid washer 134 which bears down on a resilient gasket or 
washer 136. C-ring 132 limits the downward movement of actuator 60, 
whereas an insert 140 prevents upward movement of actuator 60. In one 
embodiment, insert 140 has an annular flange 142 and a cylindrical 
extension 144 which is friction fit to the exterior or outer dimension of 
the base of actuator 60. 
The resiliency of washer 136 permits off-axis movement of actuator 60 in 
such a way that the actuator may cant relative to base plate 114. Any 
canting of the actuator is accommodated by the resilient or flexible 
connection provided by linkage 124. This configuration permits limited 
movement of the actuators and reduces the amount of leakage at seal 82 due 
to wear from side loading caused by manufacturing tolerances which result 
in lateral carriage motion within the tracks. 
FOLDING FOR STORAGE 
As mentioned, one of the features of the subject exercise stair is its easy 
stowability due to its compact design. The containment of all of the 
hydraulics within the track permits the device to be folded such that the 
track lies against the support frame. As will be described, there are a 
number of methods for permitting this folding as demonstrated by the 
devices of FIGS. 7, 9, 10, 11 and 12. Moreover foldable steps, telescoping 
arms and wheels shown in FIGS. 5 and 8 also contribute to the compact, 
portable design. 
Referring to FIG. 5, step 56 is mounted to carriage 52 at hinge points 144 
and 146 in which the top portion of the step is hinged at 144. An 
upstanding support 148 is hinged at 146, with step 56 being provided with 
a downwardly projecting flange 150 having a slot 152 extending along the 
length thereof. The weight of an individual on a step urges pin 154 in the 
direction of arrow 156 until it reaches the end of slot 152. Thus step 56 
provides steady support for the weight of the individual. 
As also illustrated in FIG. 7, the steps may be collapsed for storage into 
the plane of dual track 12 by moving step 56 up and then down. This causes 
pin 154 to move in the direction of arrows 160 which causes step 56 first 
to move upwardly and then downwardly as illustrated by arrow 162 so that 
it moves to a position illustrated in phantom at 164, which is an 
intermediate position. Thereafter, the step may be moved until it is flush 
with the top surface of track 12. 
FIG. 7 also serves to show the collapsed configuration of the exercise 
stair in which frame 14 is folded flush with the track 12, with arms 22 or 
24 telescoped into the frame. The folding of the stair to its collapsed 
position is a function of the double-hinged pivot 20. The operation of 
double-hinged pivot 20 will be described in connection with FIGS. 9 and 
10. 
Referring to FIG. 8, the collapsed exercise stair 10 may be easily 
positioned under a bed 170 by virtue of wheels 38 and telescoping handles 
22 and 24 which effectively provide a wheelbarrow structure. 
Referring now to FIG. 9, in one embodiment the assembly of the exercise 
stair from its collapsed position as illustrated in FIG. 7 to its 
operating position includes the swinging away of frame 14 from track 12 as 
illustrated at dotted outline 180. In order to accomplish this, hinge 
strap 20 is rotated in the direction of arrow 182 with the pulling away of 
the frame from the track. This movement is also illustrated by arrow 184. 
Further movement as illustrated by arrow 186 causes frame 14 to be rotated 
into place as illustrated at dotted outline 188, with the frame being 
rotated about pivot 18 as illustrated by arrow 190. When in position, end 
192 of track 12 abuts a surface 194 of frame 14 so as to provide for an 
extremely stable configuration. 
As illustrated in FIG. 10, the stability of the FIG. 9 embodiment is in 
part provided by the compression of member 192 against a plate 196 carried 
on a face 194 of upstanding frame member 32. Here, member 192 is a 
cross-member having a flat face 196 which is wedged against the face of 
plate 196 and is flush with and compressed thereto by virtue of rotation 
of frame 12 in the direction of arrow 200. The downward movement of the 
lower edge 202 of member 192 is limited by a stop 204 so that when face 
198 is flush with plate 196, the downward travel of member 192 is limited. 
This compression and downward limiting stop provides for an exceptionally 
stable assembly. The stability of this type of tight fit utilizing a 
double-hinged strapped arch configuration is aided by the horizontal 
running cross piece 34 of the frame as illustrated in FIG. 1, and also by 
the horizontally running support 39 for the lower edge of the track 12 of 
FIG. 1. Moreover, since the inner flat surfaces of the hinges are pressed 
to and overlap the sides of the track on either side, the track is 
prevented from moving laterally due to the tight bolting of the hinges to 
the track and the structural rigidity afforded by horizontal spacing 
member 36. Thus lateral movement of the exercise stair is prevented by the 
straps and the two horizontally running members which contact the floor, 
whereas the straps clamp the track to the frame, such that overall 
stability is provided by the compression of the ends of the track with the 
upstanding frame members. Note that the straps limit the separation 
between the bottoms of the track and frame. 
Referring now to FIG. 11, the hinged attachment of the track to the frame 
may be implemented through the utilization of four straps as opposed to 
two. The use of a 4-bar linkage eliminates any unexpected motions of the 
frame relative to the track so that the device cannot be set up 
improperly. This eliminates the necessity for any skill on the part of the 
user of the device since during folding, the frame goes from perpendicular 
to the track to a position parallel to the track in a controlled motion. 
Moreover the 4-bar linkage provides positive positioning in the closed and 
open positions. In this embodiment a rigid strap 205 is pivoted to track 
12 at 206 and to frame 14 at 208. A second rigid strap 209 is pivoted to 
frame 12 at 210 and to track 14 at 211 such that when frame 14 is moved 
towards frame 12, it assumes a fixed set of angular orientations with 
respect to the frame as it moves from its operating position to its folded 
position and visa-versa. This set of angular orientations is established 
by virtue of the utilization of the four straps and their multiple hinge 
points so that the frame cannot flop loosely at a number of different 
angles during set up and folding. What this accomplishes is that the 
orientation of the frame relative to the track is established at a set of 
predetermined angles such that when the frame meets the track in the 
operating position, the frame is at the appropriate angular orientation 
.alpha.. At 14' midway through the swing of the frame from the track the 
frame assumes an angular orientation .beta. with respect to the track for 
the position of strap 205 shown at 205'. Note that strap 206 prevents the 
frame from assuming position 212 at angular position .gamma. when strap 
205 is at the 205' position. Thus the frame is not left to flop loose 
between folded and open positions. Likewise at 14" when the frame is swung 
inwardly towards the track, it comes to rest parallel to the track since 
its position is maintained by virtue of the four straps. 
In order to aid in the stability of the assembled device, a block 213 is 
positioned to limit the upward movement of strap 205 such that when strap 
205 rests against the bottom edge of block 213, frame 14 is in the proper 
position with respect to the track. 
In an alternative embodiment, and referring now to FIG. 12, the frame 214 
may be divided into arms 215 and legs 216 as illustrated. Arms 215 are 
pivoted to track 217 at pivot points 218 whereas legs 216 are pivoted to 
track 217 at pivot points one of which is shown at 219. Stabilizing bars 
220 and 221 are provided respectively between the arms and the legs to 
provide lateral stability. The arms and legs are maintained in the 
positions illustrated by straps 222 and 223, having a common releasably 
engageable hinge pin 224 mounted through a slot 225 in track 217. The 
other ends of straps 222 and 223 are pivotally mounted respectively to 
legs 216 at 226 and to the arms at 227. 
In operation, hinge pin 224 is held at the end of slot 225 as illustrated 
by the force exerted on legs 216. This in turn holds the arms in place. 
When it is desired to collapse and fold the arms and legs to the track, 
hinge pin 224 moves in the direction of arrow 228 as the arms and legs are 
moved in the direction of arrows 229. 
In this embodiment the arms and legs are folded down to the plane of the 
track in a clam shell arrangement to provide an extremely compact and 
portable device. Setting up of the device merely entails movement of the 
arms and legs away from the track to the positions shown in FIG. 12. 
What has been described are a number of alternative methods of providing a 
collapsible, compact, portable exercise stair in which props and arms may 
be readily folded to the track for storage. 
With respect to portability, as illustrated in FIG. 13, a back portion 201 
of the track plate 100 may be provided with a handle 203 such that the 
entire device may be carried as illustrated in this Figure. 
PISTON CYLINDER EMBODIMENT 
Referring now to FIG. 14, in an alternative embodiment steps 230 and 232 
may be hung from hydraulic cylinders 234 and 236 respectively, with each 
of the steps being coupled to a respective cylinder by a rod 236 and 238 
respectively. Piston seals 240 are provided at the end of each of the 
rods, with the end of the cylinders being mounted to a cross-member 242 
within a frame 244. A valve 246 is interposed in a line 248 which 
communicates with the base of cylinder 234 at point 250, and with the base 
of cylinder 236 at point 252. Rods 236 and 238 are joined at their other 
ends to step frames 254 and 256 respectively. 
In this embodiment the cylinders are hung from the top of the frame and the 
steps are supported by rods which are in tension. It will be appreciated 
that rods in tension can be made smaller than rods in compression which 
translates into less weight and less cost. Also with the hanging of the 
cylinders and the rods in tension, there is a convenient self-alignment of 
the rods within their respective cylinders. 
Moreover, in the FIG. 14 embodiment the hydraulic pressure is typically 
much lower for the hydraulic ram embodiments of FIGS. 1-6. The reason for 
this is that the effective area of the piston can be larger in a piston 
cylinder than in a hydraulic ram. The lower operating pressure increases 
the lifetime of the apparatus and is therefore of advantage. 
Additionally, the effect of thermal expansion on stroke can be much less in 
the piston cylinder embodiment as compared to the positive displacement 
cylinder. In one embodiment the thermal expansion is one-ninth that of the 
positive displacement cylinder embodiment. 
As a further advantage to the hanging of the cylinders, is the ability to 
place the adjustment valve in a more convenient position without 
complicated plumbing and thus higher cost. 
Having above indicated a preferred embodiment of the present invention, it 
will occur to those skilled in the art that modifications and alternatives 
can be practiced within the spirit of the invention. It is accordingly 
intended to define the scope of the invention only as indicated in the 
following claims.