Pneumatic variable resistance rehabilitation/therapy apparatus

A pneumatic circuit for rehabilitation machines to provide a variable progressive resistance for balanced strengthening of muscle groups of a user/patient, which muscle groups are related to injured, weak, or post-operative joints, including associated ligaments and tissue, said pneumatic circuit comprising in operative combination:

• a) means for supplying pressurized air to said pneumatic circuit;
• b) a cylinder disposed downstream of said pressurized air supply means and containing a reciprocating piston and rod assembly, said cylinder comprising a confined volume defined between a side wall, a first rod end and a second closed end;
• i) said reciprocating piston having a rod side and a cylinder side, a first rest condition, and a second operating condition;
• ii) said piston separating said confined volume into an evacuation zone on said rod side and a compression zone on said cylinder side, said compression zone in fluid communication with said pressurized air supply means;
• iii) said piston operating condition including a first working stroke and a second return stroke, said working stroke being defined as the movement of said piston in a direction originating from said rod end towards said closed end and said return stroke being defined as the movement of said piston in a direction originating from said closed end towards said rod end;
• c) an accumulator having a confined volume which is in communication with said compression zone of said cylinder during both of said rest and operating conditions of said piston;
• i) said confined volume of said accumulator is sufficiently large to provide a cylinder force resistance curve for said pneumatic circuit that approximates a spring force resistance curve of a mechanical spring system during compression of air in said compression zone of said cylinder by the movement of said piston during said working stroke;
• d) said cylinder includes a relief valve assembly disposed in communication with said evacuation zone of said cylinder;
• i) said relief valve assembly includes an air inlet bleed valve adapted to permit entry of air into said evacuation zone to prevent substantial vacuum resistance from forming within said evacuation zone of said cylinder during said working stroke;
• ii) said relief valve assembly includes means for controlling the exhausting of air from said evacuation zone during said return stroke;
• e) a normally open valve disposed downstream of said pressurized air supply means and upstream of both said accumulator and cylinder;
• i) said normally open valve including means for self closure when said piston changes from said rest condition to said operating condition;
• f) a pressure regulator disposed downstream of said pressurized air supply means and upstream of said normally open valve, said pressure regulator regulating the air pressure contained within both of said confined volumes of said accumulator and said cylinder;
• g) means for adjusting pneumatic circuit air pressure, said circuit air pressure adjusting means is disposed in association with said pressure regulator to permit the communication of pressurized air via said circuit from said air supply means to said confined volumes of said accumulator and said cylinder when said piston is in said rest condition and said normally open valve is open, so that the cylinder force resistance curve associated with said reciprocating piston during said operating condition may be controlled in an infinity variable manner, said pneumatic circuit air pressure adjusting means operates independently of said means of said relief valve assembly for controlling the exhausting of air from said evacuation zone of said cylinder;
• and
• h) said cylinder and said accumulator together providing progressive resistance to a member actuated by a user/patient and said means for controlling the exhausting of air from said evacuation zone during said return stroke permits said resistance to smoothly and continuously decrease back to its original level and to provide substantial reduction in stop shock upon user/patient release of force on said member in said return stroke, said progressive resistance and said controlled return without stop shock together providing an exercise cycle which closely replicates the physiological function of the affected muscle groups.

A physical therapy and rehabilitation device for balanced strengthening of muscle groups associated with an extremity of an operator/patient in a controlled manner, which muscle groups are related to injured, weak, or post-operative joints including associated ligaments and tissue, said device including a member against which said operator applies force in a work stroke, which member has a return stroke, the improvement which comprises in operative combination:

• a) means for progressively increasing resistance to movement by said member over the work stroke of said physical therapy and rehabilitation device;
• b) means for controlled, progressively decreasing resistance to movement by said member over the return stroke of said physical therapy and rehabilitation device to provide minimum resistance at a point of maximum flexure of a user's extremity;
• c) means for selectively setting an initial resistance level of said means for progressively increasing resistance;
• and
• d) said resistance setting means operates independently of said means for controlled progressively decreasing resistance of said member return stroke.