Multiple elastic cable exercise device

An exercise device of the type employing an elastic cable to provide a restoring force comprises a handle attached to a plurality of elastic cables. The plurality of elastic cables are selectively attachable to a retainer assembly to provide a wide range of variation in restoring force exerted against the handle. The plurality of cables may also be enclosed in a flexible sheath to prevent the unattached, inactive cables from becoming entangled with each other or with the attached, active cables.

BACKGROUND OF THE INVENTION 
The present invention is related to manually operated muscle building 
exercise apparatus, specifically to apparatus that include a resilient 
elastic cable to provide resistance to motion. Such elastic cable exercise 
devices are particularly useful in that, as contrasted with barbells and 
dumbbells, a substantial resisting force can be generated by a relatively 
lightweight, portable device. 
A principal drawback to elastic cable exercise devices, however, is the 
difficulty encountered in attempting to adjust the restoring force. 
Typically, the restoring force is adjusted by increasing or decreasing the 
free length of the elastic cable. For example, U.S. Pat. No. 4,779,867 to 
Hinds discloses an elastic cable exercise device comprising a cable having 
stirrups at each end and a bar that engages the central portion of the 
cable to provide a handle for the user to pull against the cable. Hinds 
discloses that the effective free length of the cable is adjusted by 
wrapping the cable about the ends of the bar. As noted in Hinds, however, 
wrapping the cable about the bar to shorten the effective length has an 
untoward side effect in that, in use, the cable exerts a torque on the bar 
and/or can slip off the end of the bar. Hinds therefore discloses an 
improvement comprising a pair of lugs at each end of the bar designed to 
retain the cable to prevent the wrapped cable from slipping over the ends 
of the bar during use and to prevent the cable from exerting a torque on 
the bar. Hinds does not, however, address the inherent limitations in the 
range of restoring force adjustments that can be made in such exercise 
devices employing a single cable. 
Single cable elastic cable exercise devices suffer from an inherent 
limitation in the range of restoring force adjustment that can be made, 
because the only practical method for making adjustments is to shorten or 
lengthen the effective length of the cable. Elastic cables are similar to 
springs in that they exert a force that is proportional to displacement. 
Although elastic bands do not behave linearly, as do metallic springs, 
elastic bands can nevertheless be characterized as having an effective 
spring rate. Since, like a spring, an elastic cable exerts a force that is 
a function of displacement, elastic cable exercise devices do not exert a 
constant restoring force as do ordinary weight sets. Therefore, in order 
to simulate as closely as possible the constant force exerted by an 
ordinary weight set, elastic cable exercise devices are typically operated 
in such a way that the tensioned length of the cable changes by the 
minimum percentage possible over the full range of the exercise. A 
constant force is most nearly simulated using the a long cable (of low 
spring rate) stretched initially to provide the desired preload, which is 
then exercised over a short stroke. Obviously, this arrangement is not 
feasible in many instances. 
Shortening or lengthening the effective length of the elastic cable to 
adjust the preload can accomplish only a very limited variation in the 
restoring force because the preloaded cable must still have sufficient 
reserve stretch to extend through the full range of motion of the 
particular exercise. Beyond a certain point, typically about 300% or so, a 
latex cable exhibits a rapid increase in its effective spring rate. 
Accordingly, if a large reduction in the free length of the cable is 
attempted to achieve a substantial increase in preload, the result will be 
a cable that cannot be stretched through the full range of motion 
necessary to perform the exercise. Thus, to accommodate a full range of 
potential users, manufacturers of single cable elastic cable exercise 
devices must provide a selection of interchangeable cables of different 
effective spring rates, with the concomitant increase in cost, and 
decrease in ease of use. 
SUMMARY OF THE INVENTION 
The present invention is an improvement over the prior art devices in that 
it includes, in a single apparatus, a plurality of elastic cables that can 
be selectively engaged to provide a substantially wider range of 
resistance than is possible with a single cable apparatus. In one 
embodiment, a flexible sleeve surrounds the plurality of cables to retain 
the cables that are not currently in use, thereby preventing the inactive 
cables from becoming entangled with each other or with the active cables. 
In another embodiment a handle assembly operatively attached to the 
plurality of elastic cables includes a hollow cylindrical handle adapted 
to receive an exercise bar. By inserting opposite ends of the exercise bar 
into a pair of handle assemblies, the individual handle assemblies are 
converted into a single exercise bar assembly.

DETAILED DESCRIPTION 
FIG. 1 illustrates an embodiment of an exercise device 10 incorporating 
features of the present invention. The exercise device 10 includes a 
stirrup-shaped handle assembly 12 comprising a grip 14 of hollow 
cylindrical cross section attached to a U-shaped bracket 16. The outer 
diameter of the grip 14 may be padded for comfort and the inner diameter 
of the grip 14 is sized to slidingly engage the outer diameter of an end 
18 of an exercise bar 20 of generally tubular cross section. The handle 12 
may be retained on the exercise bar 20 by conventional locking means such 
as a spring pin 22 located adjacent the end 18 of exercise bar 20. 
Exercise bar 20 includes an upset 24, snap ring (not shown), or similar 
feature to constrain handle 12 to a region adjacent the ends 18. Exercise 
bar 20 is collapsible into two halves 62 and 64. The left half 62 includes 
a tip 66 of reduced diameter to permit insertion of tip 66 into the end of 
right half 64. Conventional spring pins 70 and 72 retain the assembled 
halves 62 and 64 together by engaging holes in an outer sleeve 68. The 
outer sleeve 68 may also be padded for comfort. 
Referring to FIGS. 1 and 2, secured to and depending from the lower end 26 
of bracket 16 is a resistance cartridge 30. Resistance cartridge 30 
comprises elastic cables 32, 34 and 36 surrounded by a flexible sheath 38, 
which extends to cover substantially all of the untensioned length of 
cables 32, 34 and 36. The lower extremes of elastic cables 32, 34 and 36 
terminate in "D" rings 42, 44, and 46 or other conventional fittings that 
are selectively attachable to a retainer assembly 40. The retainer 
assembly 40 holds the lower ends of the attached cables stationary such 
that when the handle 12 is moved, the attached cables are stretched to 
provide a restoring force. The inner diameter of the flexible sheath 38 is 
dimensioned such that the "D" rings 42, 44, and 46 will not easily pass 
through. Yet the inner diameter is not dimensioned so narrowly as to 
constrain the elastic cables themselves. 
With reference to FIG. 3, the upper ends of the elastic cables 32, 34, and 
36 are retained in plug 80 by inserting the ends of cables 32, 34, and 36 
each through one of a plurality of corresponding holes 82 formed in the 
lower wall 84 of plug 80. A tapered plug 86 is then pressed into the end 
of each cable. The tapered plugs 86 expand the ends of cables 32, 34 and 
36 to prevent the cables from pulling through the holes 82. Plug 80 is 
threaded into or otherwise attached by conventional means to the lower end 
26 of handle 12. Plug 80 may also be integrally formed into handle 12. 
Sheath 38 is preferably pressed onto plug 80, but may also be retained by 
adhesive or other conventional means. 
As shown in FIG. 1, an embodiment of retainer assembly 40 comprises a strap 
48 terminating at each end in a clasp 50. Clasp 50 is capable of holding 
one or more of the "D" rings 42, 44, and 46. Strap 48 is adjustable to 
accommodated variations in height of the user, the desired static preload, 
and/or the particular exercise being performed. A second exercise assembly 
comprising a handle 12 and a resistance cartridge 30 are affixed to the 
opposite end of strap 48 by means of a second clasp 50 to provide a 
balanced tensile force in strap 48 during use. In an alternate embodiment 
shown in FIG. 4, retainer assembly 40 comprises a stirrup 90 consisting of 
a handle 92 attached to a U-shaped bracket 94 terminating at a clasp 50. 
Stirrup 90 is dimensioned so as to be capable of being retained either by 
a user's foot (e.g. when performing individual curls) or by a user's hand 
(e.g. when performing a back fly exercise). 
With reference to FIGS. 5, 6, and 7, in operation, the user selects the 
number of cables to attach to the retainer for a particular exercise and 
positions the apparatus. For example, if standing forearm curls are to be 
performed, the user positions the exercise bar at waist level and stands 
on the strap 48. If fewer than all of the elastic cables are selected for 
a particular exercise, the unattached "D" rings dangle immediately 
outside, or in some cases are lightly urged by the cable against, the open 
end 48 of sheath 38. Thus constrained by sheath 38, the unattached cables 
are prevented from becoming tangled with the active cables and/or striking 
the user as the exercise is performed. This is especially helpful where 
the resistance cartridge is oriented other than vertical, such as when 
performing a chest press exercise as shown in FIG. 7. Because the handles 
12 rotatably engage the exercise bar 20 the elastic cables cannot exert a 
torque on the bar even if the bar itself is rotated through a substantial 
arc. Thus, for those exercises where the bar naturally rotates, such as 
biceps curls, an exercise device according to the present invention more 
naturally simulates the torque-free force exerted by a weight set. 
Individual arm exercises can be performed simply by sliding the handles 
off the exercise bar as shown in FIG. 8. Preferably, the effective spring 
rates of the elastic cables are different from each other, thereby 
providing N-factorial plus 1 possible composite spring rates. For example 
where cables 32, 34, and 36 are of different spring rates K32, K34 and 
K36, respectively, 7 possible composite spring rates are possible (i.e. 
K(composite)=K32; K34; K36; K32+K34; K32+K36; K34+K36; or K32+K34+K36). 
Although certain preferred embodiments and methods have been disclosed 
herein, it will be apparent from the foregoing disclosure to those skilled 
in the art that variations and modifications of such embodiments and 
methods may be made without departing from the true spirit and scope of 
the invention. For example, although three cables are shown in the 
embodiment of FIG. 2, any number of cables in excess of one is considered 
to be within the scope of the present invention. Accordingly, it is 
intended that the invention shall be limited only to the extent required 
by the appended claims and the rules and principles of applicable law.