Reciprocable load resisting device

Abstract

A load resisting device for use in an exercise machine which includes a cylinder, a piston which is movable in a first direction inside the cylinder against a force generated by air pressure in the cylinder, and an O-ring seal, mounted to the piston, which provides a seal between the piston and the cylinder, when the piston is moved in a first direction, and which allows air to bypass the O-ring when the piston is moved in a second direction which is opposite to the first direction.

Description

BACKGROUND OF THE INVENTION

This invention relates to a load-resisting device which is suitable for use in an exercise machine such as a rowing machine, a lifting or curl machine or any similar apparatus which requires muscular energy for activation.

In an exercise machine of the aforementioned kind it is desirable to provide a load-resisting device which offers resistance to effort which is exerted by muscular force, which is of inexpensive construction and which is easily adjustable, in respect of its load-resisting characteristics, to suit different users.

SUMMARY OF INVENTION

The invention provides a reciprocable load-resisting device which includes a cylinder with an inner closed end and an outer, open end, a piston which is reciprocably located inside the cylinder thereby defining a volume of variable size inside the cylinder between the inner closed end of the cylinder and a first side of the piston, a rod which is fixed to the piston and which extends from the cylinder through the outer, open end, a first mounting formation on the cylinder, a second mounting formation on the rod, a one-way valve which is associated with the piston and which opens to allow fluid to flow into the volume when the piston is withdrawn from the cylinder and which closes when the piston is moved into the cylinder so that the piston causes fluid inside the volume to be pressurised, an outlet from the volume through which fluid can flow when the volume is pressurised, and a control mechanism which is adjustable to control the rate at which fluid can flow from the volume.

Although the load-resisting device can be used with any suitable compressible fluid it preferably is used with air.

Preferably the outlet returns fluid which flows from the volume to the cylinder on a second side of the piston.

A cap may be fixed to the outer, open end of the cylinder and include an opening through which the piston rod extends.

In one form of the invention the device includes a bypass conduit which extends from the volume to a portion of the cylinder between the second side of the piston and the outer end of the cylinder and the control mechanism is engaged with the bypass conduit.

In a second form of the invention the control mechanism is mounted to the piston so that fluid can flow through the piston, or bypass the piston, when it flows from the volume to the cylinder between the outer, open end and the second side of the piston. In this form of the invention the control mechanism may be adjustable to allow fluid to flow, inside the cylinder, from the first side of the piston to the second side.

The one-way valve may be of any appropriate kind. In one form of the invention the valve is formed by an O-ring which is mounted to the piston and which is moved from a sealing position, when the piston is moved into the cylinder, to a non-sealing position, when the piston is withdrawn from the cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is further described by way of examples with reference to the accompanying drawings in which:

FIG. 1 is a perspective view of a load-resisting device according to a first form of the invention in an exploded configuration,

FIG. 2 is an enlarged view of some of the components shown in FIG. 1, and

FIGS. 3 and 4 correspond respectively to FIGS. 1 and 2 of a load-resisting device according to a second form of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1 and 2 of the accompanying drawings illustrate a load-resisting device 10 according to a first form of the invention which includes a cylinder 12, a piston 14 and a piston rod 16.

The cylinder includes a cylindrical tube 18 with inner and outer ends 20 and 22 respectively. The end 20 is closed by means of a cap 24 which includes a clevis 26 by means of which the cylinder can be anchored, in pivotal fashion, to suitable supporting structure in an exercise machine, not shown.

A cap 28 is used to close the outer end 22 of the cylinder. The cap has an opening 30 through which the rod 16 passes. The opening 30 also acts as a bush for the rod. A fixing member 32, which carries a clevis formation, is fixed to an outer end of the rod 16 and serves to anchor the rod to a movable component, not shown, of an appropriate exercise machine, not shown. In use of the exercise machine force is applied directly or indirectly to the rod by a person using the machine. The exercise machine may be a rowing machine, a curl-type machine or the like, typically in which reciprocating movement takes place against a resistance force of adjustable magnitude.

The piston 14 includes a socket 34 and an enlarged collar 36. The collar has a projecting portion 38 which is formed with a flat surface 40. A flexible O-ring 42 is positioned in a groove 44 formed in the portion 38. The groove does not extend over the flat surface 40 and the O-ring is positioned so that it abuts an inner side 46 of the collar surrounding the portion 38.

The cylinder has an outlet opening 50 and an inlet opening 52 formed through its wall near the inner end 20 and the outer end 22 respectively. A bypass conduit 54 is connected to the outlet 50 and, via a control mechanism 56, to the inlet 52.

The control mechanism 56 includes a housing 60 with an internal passage 62 in which is located a ball 64. The ball rests on a seat 66 to close the passage and is biased into engagement with the seat by means of a spring 68. The force which is exerted by the spring on the ball can be adjusted by rotating a knob 70 which is threadedly engaged with a threaded column 72 which projects from the housing and which houses the spring 68.

The piston, when located inside the cylinder, defines a closed volume of variable size inside the cylinder between the inner end 20 and a first side 80 of the piston. The outlet 50 is in communication with this volume. A second volume is defined between a second side 82 of the piston and the cap 28. The inlet 52 is in communication with this volume. The cap 28 has a number of bleed passages 84 which allow air to flow into and out of the second volume.

In use of the device the piston is reciprocated to and fro by a user in a manner which depends on the nature of the exercise machine with which the device is used. The O-ring seal provides a one-way valve function as follows. When the rod is moved telescopically into the cylinder the O-ring 42 is pushed against the side 46 of the piston to a sealing position at which the O-ring forms an air seal. The air inside a first volume in the cylinder, ie. on the first side 80 of the piston, is compressed and attempts to flow through the outlet 50. The free escape of air through the outlet is constricted by the control mechanism 56. The rate at which air can escape from the first volume is determined by the bias force which is exerted by the spring 68 on the ball 64. This force can be adjusted with ease merely by rotating the knob 70 in one direction or the other.

The air which flows through the control mechanism 56 is returned to the second volume inside the cylinder defined between the second side 82 of the piston and the cap 28. The air is returned to the cylinder, as opposed to being allowed directly to atmosphere, for the air flowing from the first volume is under pressure and, when venting directly to atmosphere, can be fairly noisy. By returning the air to the cylinder the noise level is reduced.

When the rod is retracted from the cylinder, inside the cylinder, from the second side 82 of the piston to the first side 80, the O-ring 42 moves slightly away from the side 46, because of a slight frictional drag against an inner wall of the cylinder and, due to the flat surface 40 on the portion 38, the O-ring takes up a non-sealing position in which a passage is created on the piston through which air can flow. Thus, on a return stroke little of any resistance is offered to the user.

Pressure equalisation inside the cylinder can take place, as necessary, by virtue of the bleed passages 84 which allow air to flow into or out of the cylinder, on the second side of the piston.

The cylinder 12 preferably has a fairly large diameter, for example of the order of 100 mm, so that although the pressure which is generated inside the first volume is not unduly high a fairly significantly force is nonetheless generated which acts in a load-resisting manner to restrain movement of the rod 16, in a yielding manner, into the cylinder. The load-resisting force can, as has been noted, be adjusted readily merely by rotating the knob 70.

FIGS. 3 and 4 illustrate a load-resisting device which is designated 10A. Where applicable components in the device 10A which are the same as components in the device 10 bear similar references numerals.

A principal difference between the device 10A, compared to the device 10, is that the bypass conduit 54 and the control mechanism 56 are replaced by a control mechanism 90.

A piston 14A has a circular serrated formation 92 which is rotatably mounted to a body portion 94 of the piston. A spring 68 bears against a ball 64 which is positioned to engage with a seat 66 at an end of a passage 62 which extends from one side of the piston to the other (shown in dotted outline in FIG. 4). A cap 28A has serrated formations 96 which are complementary to the formations 92. A piston rod 16 has a threaded end 16A which passes through an opening 30 in the cap and which is engageable with a threaded socket 98 in the piston. The cap has a circumferential groove 100 on a projection 102 which extends into an outer end 22 of the cylinder 12. A circlip 104, which is engaged with opposing slots 106 in the cylinder, is also engageable with opposing portions of the groove 102 when the cap is mated to the cylinder.

A leading end of the rod 16 urges the spring 68 to bear against the ball 64 which acts to prevent a free flow of air from one side of the piston to an opposing side, when the piston is urged deeper into the cylinder. When the piston is withdrawn from the cylinder an O-ring 42 is moved on the piston and creates a passage through which air can bypass the piston in a manner which is similar to what has been described in connection with the device 10 of FIGS. 1 and 2.

In order to adjust the load-resisting force, which is offered by the device 10A, a user withdraws the piston 14A to the maximum extent so that the formations 92 mate with the formations 96 on the cap. The piston is restrained, if necessary, against rotation, and the cap is rotated in one direction or the other, according to requirement. An external surface of the cap has knurled formations 110 to facilitate this rotation. As the cap is rotated the piston is rotated as well and the piston rod is screwed deeper into the piston, or to some extent out of the piston, depending on the rotation direction. The degree of compression of the spring 68 is thereby adjusted and, in this way, the biasing force which is exerted on the ball 64 is varied.

The circlip is designed so that it holds the cap captive to the cylinder yet allows the cap to rotate relatively to the cylinder to enable the load-resisting force, generated by the device 10A, to be varied according to requirement.

The device of the invention can be used with any appropriate exercise machine in which a reciprocating movement is produced e.g. a rowing machine, a lifting or curl-machine, or the like. Generally the formation 26 would be fixed to supporting structure, and the formation 32 would be connected directly or indirectly to an actuator operable by a user.

Claims

1. A reciprocable load-resisting device which includes a cylinder with an inner closed end and an outer, open end, a piston which is reciprocably located inside the cylinder thereby defining a volume of variable size inside the cylinder between the inner closed end of the cylinder and a first side of the piston, a rod which is fixed to the piston and which extends from the cylinder through the outer, open end, a first mounting formation on the cylinder, a second mounting formation on the rod, a one-way valve which is associated with the piston and which opens to allow fluid to flow into the volume when the piston is withdrawn from the cylinder and which closes when the piston is moved into the cylinder so that the piston causes fluid inside the volume to be pressurised, an outlet from the volume through which fluid can flow when the volume is pressurised, and a control mechanism which is adjustable to control the rate at which fluid can flow from the volume.

2. A load-resisting device according to claim 1 wherein the outlet returns fluid which flows from the volume to the cylinder on a second side of the piston.

3. A load-resisting device according to claim 1 which includes a cap which is fixed to the outer, open end of the cylinder and which includes an opening through which the piston rod extends.

4. A load-resisting device according to claim 1 which includes a bypass conduit which extends from the volume to a portion of the cylinder between the second side of the piston and wherein the outer end of the cylinder and the control mechanism is engaged with the bypass conduit.

5. A load-resisting device according to claim 1 wherein the control mechanism is mounted to the piston so that fluid can flow through the piston, or bypass the piston, when it flows from the volume to the cylinder between the outer, open end and the second side of the piston.

6. A load-resisting device according to claim 5 wherein the control mechanism may be adjustable to allow fluid to flow, inside the cylinder, from the first side of the piston to the second side.

7. A load-resisting device according to claim 1 wherein the one-way valve is formed by an O-ring which is mounted to the piston and which is moved from a sealing position, when the piston is moved into the cylinder, to a non-sealing position, when the piston is withdrawn from the cylinder.

8. A load-resisting device for use in an exercise machine which includes a cylinder, a piston which is movable in a first direction inside the cylinder against a force generated by air pressure in the cylinder, and an O-ring seal, mounted to the piston, which provides a seal between the piston and the cylinder, when the piston is moved in a first direction, and which allows air to bypass the O-ring when the piston is moved in a second direction which is opposite to the first direction.