Force feedback system for continuous passive motion device

Abstract: A method for providing force feedback in continuous passive motion systems, for use in treating or preventing low back pain in an individual. The method comprises the steps of: providing a mechanism to initiate continuous passive motion for the spine; providing a system for measuring the force exerted by the mechanism on an individual's spine; and providing a system for controlling the force exerted by the mechanism on an individual's spine. A timer may be provided for the basic control of the mechanism. Suitable apparatus comprises, a back support (12) having a force applying section (16). The force applying section has a mechanism (13, 14, 15) for initiating continuous passive motion to an individual's back. Force measuring transducer (17) is positioned at the point where the force applying section contacts the individual's back and a logic system controls the operation of said force applying section based upon the measurements obtained from the force measurement means.

Description: This invention pertains to continuous passive motion methods and means, and concerns such continuous passive motion methods and means as they are applied in the treatment and/or prevention of back pain. Back pain is a very widespread malady in the United States. Lower back pain can be caused by disease, injury or congenital defect. There are many different types of relevant therapeutic machines on the market today. There have been a number of patents issued in the continuous passive motion field including the U S Patent No. 4,981,131, issued to the applicant Rowland G Hazard for a Passive Motion Back Support. This patent shows a pneumatic based apparatus for providing continuous passive motion in treating or preventing back pain. A number of devices provide mechanical apparatus for the same purpose. The key difficulty inherent in these designs and requiring solution in order to optimize the user's comfort is the need for force feedback to control the support devices. Without such feedback, devices cannot accommodate variations in the user's spinal compliance, posture and position. What is needed is a means than will provide force feedback for mechanical and pneumatic devices that deliver back support and continuous passive spinal motion. International Patent Application No. PCT/SE 82/00263 (publication no. WO 83/00620) discloses apparatus for treating back ailments in which means are provided for sensing the pressure applied by a mechanical support to the small of the back, and a vertical support plate against which the support rests can be adjusted in response to the measured pressure. In another embodiment the means for supporting the small of the back is a hollow member filled with a liquid or gas, the flow of liquid or gas to and from the hollow member being controlled in dependence on the sensed pressure and optionally in dependence upon a predetermined time-pressure programme. The invention provides continuous passive motion apparatus In accordance with Claim 1 Preferably, in the first part of the cycle the continuous and automatic control tends to hold the force within a predetermined range. In the second part of the cycle the force can be reduced substantially to zero. Further features of this invention will become more apparent by reference to the following description taken in conjunction with the following figures, in which: Figure 1 is the logic chart of the logic system means; Figure 2 is the chart of the feedback cycle of a continuous passive motion backrest through a full cycle of increasing and decreasing force induced to the spine; Figure 3 is a perspective view of one embodiment of the novel means in position in a chair; Figure 4 is a side elevational view of an embodiment of the means according to the invention in the form of a cam driven mechanical device; and Figure 5 is a side elevational view of a rack and pinion mechanical device according to the invention. As shown in the figures, one means 10 according to the invention comprises a logic box 11 that is positioned in a chair 1. The means have a continuous passive motion support 12 and have some type of motor (mechanical) or pneumatic drive 13. Two examples of mechanical drives are shown. In figure 4, a cam driven device is shown. The device comprises a motor 13 having its shaft connected to a cam drive 15 by means of a belt 14. The device has a flexible support panel 16 and a load cell or transducer 17 to measure force between the support and the user's back. The cam 15 drives the support panel 16. As shown in Figure 5, the mechanical device is driven by means of a rack and pinion arrangement. The device has a motor 13 driving a pinion 18 using a belt 14. The pinion 18 activates piston 19 which, in turn, moves support panel 21. A compression spring 20 is used to counterbalance the actions of the piston 19. The support panel contains a load cell or transducer 22. A spring and cable type mechanical system could also be used. A pneumatic apparatus, as described in applicant's previous patent can also be fitted with the logic system and the force sensing devices. All the above-described means provide a backward and forward motion of a support that is in contact with an individual's back. The motion includes lordotic and kyphotic movements of the spine such that flexion and extension alternately occur between adjacent vertebrae. The mechanisms cyclically impose increasing and decreasing force against the user. The control of the motion can be accomplished by means of a timer. However, the logic system of the means will override the signal sent to the motor by monitoring the force against the user's back. Using feedback from the force transducer, the logic system can regulate the motion to allow the desired amounts of the lordotic movement despite variations in spinal compliance and in the individual's posture and position. The logic of the override control of the circuit is shown in Figures 1 and 2. Low force input from the force transducer between the support and the user's back is mediated by the logic box to signal the motor to rotate in a forward direction. The forward rotation is transmitted to the drive device to create forward displacement of the support to induce greater support to the user's spine. Middle range input from the force transducer signals the motor to rest in neutral with no motion off the drive device. Force input in the high range signals the motor to rotate in reverse, causing the mechanism to revolve back away from the user's back.

Claims: Continuous passive motion apparatus for use in treating or preventing low back pain and providing comfort in an individual, in the seated position, the apparatus including at least one static back support (10) attached to a seat; a mechanism (12, 13; 13-16; 13, 14, 18-21) adjacent to said static back support to exert a force on the lumbar area in order to produce lordotic motion for the spine; and a timer for varying the force exerted in a predetermined cyclic manner, wherein in a first part of the cycle a force is exerted increasing the lordotic position of the spine from its original state, and a second part of said cycle comprises a period of reduced force decreasing the lordotic position of the spine allowing it to be returned to its original state such that flexion and extension alternately occur between adjacent vertebrae of the spine; characterised in that the apparatus includes; force measuring means (17, 22) providing an output indicative of said force; means (11) which is responsive to said output for controlling the force exerted by the mechanism and includes a logic system means for overriding the timer in the first part of the cycle for maintaining the predetermined variation of the force. Apparatus according to claim 1 wherein the logic system varies the force such that in said first part of the cycle the continuous and automatic control tends to hold the force within a predetermined range. Apparatus according to claim 1 or claim 2 wherein the logic system varies the force such that in said second part of the cycle the force is reduced substantially to zero. Apparatus according to any preceding claim, wherein said mechanism (12, 13; 13-16; 13, 14, 18-21) comprises a pneumatic operated unit.

Inventors: HAZARD ROWLAND G, REINECKE STEVEN M, HAZARD, ROWLAND G., REINECKE, STEVEN M.
Applicants: HAZARD ROWLAND G, REINECKE STEVEN M, HAZARD, ROWLAND G., REINECKE, STEVEN M.
Application year: 1993
Main classification: A61H1
IPC codes: A61F5, A61H1, A61H23