Exercise Machines Using Vacuum Cylinders

Jul 27 17:21:58 View QTML

I just filed a provisional patent on some of the tech used on this site. I needed to do so within a year of making this site public and that deadline draws near!

In the process of getting myself into patent mode, I went into my files and pulled out a patent application I had written many years ago for a family of exercise machines. Since I was short on funds I attempted to do the application myself, and the process dragged out over several years. Doing the drawings was particularly challenging. I went through two cad programs -- Drafix CAD and AutoCad LT -- before opting to make a small library of 3D drawing functions in PostScript, and use the C preprocessor to include this library into the respective PostScript files used for the figures.

While this may seem difficult compared to using a visual drawing program, with PostScript I could make functions for drawing various parts and set the sizes for such parts as call frame parameters. This was handy for making multiple vacuum cylinders.

Anyway, when I got to the point of doing the actual filing, I choked and hired a law firm to clean up my application and put it in the right format. (The Patent Office makes the IRS seem friendly by comparison.) Alas, by that time, a Taiwanese inventor had gotten a patent on a similar device, and so the Patent Office rejected mine. While I could have made a case that mine was superior and the Taiwanese device was defective, I had already dropped $5K on project and was loathe to spend more.

Anyone handy in the machine shop is free to build a device based on this application. I don't know how well it would work as I never built a model. I do not know the ideal means to get a good seal without creating too much friction, and how to make the moving parts light enough to avoid too much momentum yet strong enough to handle the forces involved.

Finding a bicycle pump you can take apart might be the way to proceed. If you can flip the mechanism used as a check valve, you have a lightweight vacuum cylinder...

I do know that I achieved 15 pounds of new muscle one summer when doing a power based training regimen. By power I mean force times speed. With free weights such a workout produces a great deal of dangerous momentum. I was young enough to get away with it at the time, but wouldn't dare try such a workout today with my aging body.

But with machines based on the application below, I would be tempted to see how a power based workout would work for those getting AARP advertisements in the mail.

Figures

[I am putting the figures early in order to keep your attention. You might want to skim or skip the background of the invention.]

Background of the Invention

Free weights, such as barbells and dumbbells have proven both popular and effective as tools for muscular conditioning, both for training in many sports, improving physical appearance and improving health in general. However, free weights have several limitations. First, working out with free weights can be dangerous. If the user loses control of the weight, the weight can fall causing injury or even death. Second, free weights are limited in the force curves and angles they can produce. They only pull downward. Finally, free weights suffer from inertial effects. When the weight is accelerated upward, the force required is greater than nominal; when the weight is accelerated downward, the force is less than nominal. This allows "cheating", robbing the exerciser of work during part of the stroke. More important, at the end of the lowering part of the exercise, acceleration is required to bring the weight to a halt. If the exerciser has allowed the weight to lower too quickly, he may find he has insufficient strength to stop the weight, resulting in muscular pulls or other injuries.

Some of the dangers from free weights can be averted by have a training partner to help maintain control of the weight as the trainee fatigues. This solution is not always convenient. Another proposed solution is to work out in slow motion to reduce inertial effects. However, this solution is relatively unpopular for several reasons. First, slow lifting is painful due to lactic acid buildup in the muscles. Second, many sports require high power (force times speed) output from athletes. Since most athletes want to train as they play, slow motion lifting is unacceptable.

The most popular replacement for free weights consists of weight stack machines. An example (with supporting framework omitted) is shown in FIG. 1. This particular example is for doing leg extensions. The user sits in the chair 29 and places her feet behind pad 32. Extending her legs results in turning cam 30, which pulls a cable 22 via several pulleys 21, which lift several heavy plates 24. The plates travel on rails 23, so they cannot fall in an uncontrolled fashion as in free weights. The user selects the number of plates to lift by placing a pin 33 through a hole in 28 in the bottommost desired plate. The pin goes through a hole in the shaft 26 that is attached to the cable.

Machines of this sort afford several advantages over free weights: Placing a pin in a hole in the weight stack is quicker than adding plates to a barbell. The user interface to the weight can be other than a handle, such as the shin pad in the example. This allows exercising the legs at angles difficult to achieve with free weights. Third, the force can be translated from the up/down of gravity to an arbitrary curvilinear profile. In the example, the force has been converted to a constant torque about a fixed axis. Fourth, the amount of force as a function of the lift can be arbitrarily set by changes in leverage. In the example, the circular cam 30 could be replaced by a cam of varying radius to produce a force curve that more closely matches the strength curve of the user. Finally, the limited motion of the parts of such machines greatly reduces the chance of injury should the user lose control due to exertion.

Because of these advantages, a great many machines of this class have been devised and widely deployed in both commercial gyms and home workout rooms.

However, these machines still share one of the defects of free weights: inertia effects.

Several replacements for the weight stack 27 have been devised with varying degrees of success. One type of replacement for weight stacks consists of hydraulic cylinders producing isokinetic resistance, such as U.S. Pat. No. 3,359,802 issued to C. E. Sollenberger on Dec. 26, 1967. As the user lifts, a piston forces fluid through a constricted opening. This produces a highly speed dependent frictional force. Adjustments of the opening do not so much change the force provided by the machine as the top speed with which working out is possible. Such machines have negligible inertial effects; however, they have two disadvantages that limit their popularity. First, the speed limiting force curve discourages working out to full performance. The visible result of the workout is largely independent of effort expended. Some hydraulic cylinder designs, such as U.S. Pat. No. 3,606,318 issued to James B. Gilstrap on Sept. 20, 1971, overcome this defect by using constant pressure valves. The second defect, however, is shared by all such hydraulic machine: they produce only concentric (lifting) resistance. No force is pushed against user during the eccentric (lowering) part of the exercise. Given that some studies show that it is the eccentric part of the exercise that provides the most stimulus for muscular growth [], this is a serious defect.

Another weight stack replacement consists of an array of resilient materials that can be independently engaged. For example, U.S. Pat. No. 4,620,704 issued to Tessema Shifferaw on Nov. 4, 1986, uses a set of resilient rods. One difficulty with this approach is that we now have a positional dependent force curve to deal with. U.S. Pat. No. 4,811,946 issued to Stanley J. Pelczar on Mar. 14, 1989, uses pre-wound springs to lessen this effect. However, this is a complicated arrangement subject to friction. And all solid resilient materials are subject to fatigue over time.

A type of spring that is simple and does not wear out consists of a cushion of air. Several pneumatic devices have been designed using this principle, such as U.S. Pat. No 177,251 issued to Homer U. Johnson on May 9, 1876. However, air springs suffer from position-dependent force curve. The aforementioned patent treats this as a feature, where the ability to lift a certain distance provides a test of strength. Other devices, such as U.S. Pat. No. 4,728,101 issued to David M. King on Mar. 1, 1988 and U.S. Pat. No. 4,826,156 issued to Beat Dreier on May 2, 1989, use a large reservior of air as the spring. This virtually eliminates position dependence of the force curve, but requires pumping up the reservoir prior to exercising. This necessitates having electrical or pneumatic lines running to the equipment in the gym, or requiring users to operate manual air pumps prior to exercising, in order to be able to adjust the resistance.

Finally, there are complex arrangements of electrical motors with various feedback mechanisms for simulating the action of weights, inertialess constant forces, or other force functions, such as U.S. Pat. No. 5,020,794 issued to William H. Englehardt, Olgerts J. Svilans, and Augustine Nieto on Jun. 4, 1991. While this is a very general approach, the apparatus becomes expensive to build and maintain, and it becomes necessary to run electrical wiring throughout the gym.

A simple, readily available source of speed and position independent force is that of a piston drawing a vacuum. This mechanism has been utilized in the prior art, albeit not effectively. U.S. Pat. No. 767,008 issued to Lucien Pelletier and Gaston Monier, Jr. on Aug. 9, 1904 [assigned to…], and U.S. Pat. No. 3,471,145 issued to Isaac Berger [assigned to …] on Oct. 7, 1969 both utilize a single vacuum cylinder. To provide multiple values of resistance, a bleed valve is provided to let air into the vacuum cylinder at a variable rate. The amount of air allowed in the cylinder is time-dependent, thereby defeating the speed and position independence that a vacuum cylinder affords. Finally, the purging of this air on the return stroke provides resistance in the opposite direction, making these devices useable for concentric workouts only.

Summary of the Current Invention

The current invention utilizes vacuum in a simple fashion that preserves the speed and position independence of pulling a vacuum in a sealed cylinder, while allowing the user to set the amount of force over a wide range of values.

The procedure is simple, yet unknown to prior art: utilize an array of airtight vacuum cylinders, that can be independently engaged, much as a weight stack machine can engage a variable number of plates of fixed weight. The result is a family of exercise machines that have the same ease of use as weight stack machines, without their high inertia. The machines are simple to manufacture and maintain, require no electricity, are lighter in weight than weight stack machines, and can even be used in zero gravity environments. Further, the current invention is not constrained to a vertical orientation, so the number of pulleys and/or levers can be reduced for those exercise machines for which the user moves the handles/pads in a non-vertical direction.

Detailed Description of the Current Invention

In the embodiment to be described, the current invention serves as a replacement for the weight stack 27 of a prior art cable machine such as that shown in FIG. 1. FIG. 2 3 is the same as FIG. 2 save that the machine has been lifted from it initial position by the user (not shown). These figures show only the force mechanism. The structural framework and human interface has been omitted as there are many possible permutations known to the current state of the art.

Like the prior art, we have a cable 40 coupled to a mechanism which provides downward force. In lieu of heavy plates, there are six vacuum units providing forces of 5 pounds 60a, 40 pounds 60b, 80 pounds 60c, 160 pounds 60d, 20 pounds 60e and 10 pounds 60f. These force values allow setting from 5 to 315 pounds in 5 pound increments with the fewest possible vacuum units. Other values are possible, such as having vacuum units of force values corresponding to standard Olympic weight plates.

The arrangement of the vacuum units is designed to keep torque on the carriage 42 at a minimum for all possible force combinations. This torque could be eliminated entirely by using matched vacuum units placed symmetrically about the cable; however, this would require more vacuum units.

The vacuum units are rigidly attached to a base plate 61 and a collar plate 54. These two plates are to be attached to the framework of the particular machine (not shown). On front of the collar plate is a sign plate 55 on which is inscribed the force values of each of the vacuum units. Attached to the sign plate is a shelf 57 with holes 47 in front of each vacuum unit. In these holes are placed those pins 50 for those vacuum units that are not currently engaged.

Also attached to the base plate 61 and extending through the collar 54 are a pair of rails 45. Riding on these rails is the aforementioned carriage 42. The carriage consists of pairs of parallel plates 43, 44 that are rigidly attached to a pair of sleeves 46 which slide on the rails. The carriage is attached to the cable 40 by a bolt 41.

For each vacuum unit there are holes 48 in the plates 43, 44 of the carriage. When the carriage is in the starting position, the user can engage the desired vacuum units by moving pins 50 from the shelf 57 to the corresponding holes in the carriage 42. In these figures, the 80 pound 60c and 20 pound 60e vacuum units have been engaged for a total force of 100 pounds.

As can best be seen in FIG. 3, from each vacuum unit there protrudes a shaft 53 terminated by an eyelet 49. When the carriage is in its starting position, the sleeves 46 rest on washers 51 which hold the carriage in a position so as to align its holes 48 with the eyelets 49. The eyelets 49fit in the gaps between the pairs of parallel plates 43, 44 that make up the carriage 42. Thus, when pins 50 are inserted through holes in the carriage, they also go through the corresponding eyelets 49. When the cable 40 pulls the carriage 42 upward, the engaged shafts 53 of the selected vacuum units are likewise pulled upwards.

To see how the vacuum units provide their downward force we turn to Figures 4 and 5 . FIG. 4 shows a vacuum unit 60 in cross section in its initial position. FIG. 5 shows a vacuum unit 60 in cross section at full extension. The section for both figures is taken from line 4 in FIG. 3.

A vacuum unit consists of a cylinder 58 screwed into the base 61. Inside this cylinder is a piston 75 wrapped in an O-ring 74 to provide an airtight seal against the piston. This piston 75 is attached to the already seen shaft 53 which is terminated by an eyelet 49. Just above the piston on the shaft is a tall washer 70. This provides a stop against the cap 63 that is screwed on to of the cylinder 58in order to keep the check valve 71 from being crushed. (The function of the check valve will be covered later)

The cap is provided with three vent holes 64 to keep the region above the piston 68 at atmospheric pressure as the piston is pulled upward. To keep dust from settling in through these holes, a dust cap 52 is mounted above the cap 63 on three supports 66 terminated by snap fasteners 67 which fit in holes 78 in the cap 63. The cross section shows only two of the vent holes and supports for the dust cap. A better view of how these are arranged can be seen by looking at FIG. 6, which shows a perspective view from above of the cap 63. This figure shows the arrangement of the vent holes 64, holes for the snap fasteners 78 as well as the hole for the shaft 65.

Going back to FIG. 4, we see that in the starting position, the piston 75, rests on a pad 76. This pad is of an elastic substance such as rubber to provide some shock absorption when the piston is lowered rapidly. The pad is in the shape of a truncated cone on order to allow some room for deformation. However, the room for deformation should be kept to a minimum to reduce the amount of air that is below the piston 75 in the initial starting position.

In FIG. 5, the piston has been pulled upwards as far as it can go. The tall washer 70 rests against the cap 63 preventing further travel. The region 68 above the piston is at atmospheric pressure since this region is vented to the outside by the aforementioned vent holes 64. The region 69 below the piston is at a near vacuum. There will be some air from deformation space around the pad. Also, a small amount of air could leak around the O-ring as the piston is raised. However, this deviation from perfect vacuum is negligible for our purposes save at the very beginning of the lift, where the deformation space is significant compared to the total volume of the region below the piston. The net result is a downward force equal to atmospheric pressure multiplied by the area of the piston. This force is effectively independent of the position of the piston and the speed at which it was raised.

The function of the check valve 71 is best illustrated by looking at a cross section of the piston as seen in FIG. 7. The check valve provides a one-way flow of air through a passage 79 bored in the piston. The purpose is as follows: the seal of the O-ring 74 against the cylinder 58 is not expected to be perfect. Over time, air can work its way around the seal. By providing the passage and check valve, this air can be easily purged by occasionally pushing the piston down against the pad 76.

An alternative arrangement would be to replace the piston with a cup washer. This is shown in FIG. 8. FIG. 9 shows the same arrangement in cross section. In this alternative embodiment, the tall washer has been replaced by a tall nut 80 into which the shaft 53 is screwed. Below this nut is a cup washer 83 sandwiched between upper 84 and lower 82 washers. This sandwich is bound to the nut by a fat machine screw 81. If this alternative arrangement is used, the shape of the pad 76 should be changed to nearly conform to the bottom profile of this arrangement in order to minimize air underneath at the starting position.

Arrays of independently engaged vacuum units such as in FIG. 2 are not limited to use in machines currently using cables attached to weight stacks. Weight stack machines have also been developed using combinations of levers and rollers to couple handles and/or pads to the weight stack. There are also weight stack machines for which the handles or pads pressed by the exerciser are rigidly attached to a carriage traveling on rails parallel (or the same as) those rails on which the weights of the weight stack travel. There are also weight machines which use the barbell plates instead of a stack of plates to provide downward force. For all machines of these types, similar machines could be made with the vacuum units of the present invention replacing the weights.

However, the present invention is not limited to replacing weights. Unlike weight stacks, vacuum cylinder provide their force irrespective of their orientation (save for the weight of the piston and shaft, which can be easily compensated). Thus, the present invention can also be used in exercise machines currently designed to use springs, pneumatic or hydraulic cylinders, or electric motors and so forth, as well as exercise machines of future design that need a source of both concentric and eccentric force.

Tags: weight training exercise patents