Valve-less fluid control circuit for rhythmic action devices

A valve-less fluid control circuit for controlling rhythmic action devices, such as circulatory assist devices. The fluid control circuit has a plurality of pressure sensitive fluid oscillators for circulating a fluid. Each fluid oscillator includes a capacitance chamber unit for peristaltic pumping of fluid after being filled via an input conduit and a resistance conduit. A first control conduit provides an outlet of fluid from the capacitance unit during peristaltic pumping, and when the pressure of the fluid in the first control conduit reaches a certain level relative to the pressure of fluid in the input conduit, the fluid is directed through an interactive region and exits the first fluid oscillator through an exhaust conduit. A coupling unit couples the output of the first fluid oscillator to the input conduit of the successive fluid oscillator, so that the expansion and contraction of the capacitance chambers occurs successively without the need for valves and/or complicated control circuitry, such as solenoids and cams. A return conduit at the last fluid oscillator returns the fluid to a second control conduit of the first fluid oscillator to refill the first capacitance chamber.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to mechanical devices providing rhythmic
 action. More particularly, the invention relates to fluid control circuits
 providing rhythmic action for sequential compression devices, such as
 circulatory assist devices.
 2. Description of the Related Art Various examples of fluid control
 circuits for sequential compression devices used to assist patients in
 circulating fluid around a limb or limbs are provided by U.S. Pat. Nos.
 4,396,010 (to Arkans), 4,481,937 (to Arkans) and U.S. Pat. No. 4,858,596
 (to Kolstedt). The contents of these patents are incorporated by reference
 herein as background material.
 Prior art fluid control circuits utilize a series of valves and pressure
 relief valves, which must be periodically opened and closed, for
 circulating the liquid through a sleeve or cuff. Opening and closing of
 the valves requires either a series of solenoid controls (with
 sophisticated electronic controls) or cam actuators. The hardware
 necessary for the control of opening and closing valves uses large amounts
 of power and increases the bulk of such devices.
 In addition, the mechanical action of the valves, solenoids and cams are
 prone to wear and tear, which will degrade the quality of the compression
 device over time, requiring high costs for maintenance and repair. Thus,
 there exists a need in the art for improvement in fluid control circuits.
 One of the present inventors previously designed a valve-less artificial
 heart utilizing a dual fluid oscillator (U.S. Pat. No. 3,599,244, the
 content of which is incorporated by reference herein as background
 material), which relies on the dynamic flow properties of blood for its
 operation. In this device, the system provides better reliability than
 prior art artificial hearts using mechanical valves, which often fail.
 However, the dual fluid oscillator of the prior art requires the placement
 of a pump at each output having a pressure, which is directly related to
 the input pressure, and is inversely related to the pressure head against
 which it is being pumped. Moreover, the fluid from one part of the dual
 fluid oscillator does not directly transfer the fluid to the second (or
 any other) oscillator, as would be required in a sequential compression
 device.
 Finally, the prior art dual fluid oscillator also requires that the
 oscillator portions must be arranged contiguously with each other so that
 a filling of a first fluid oscillator with a working fluid increases the
 pressure to such a level that the pressure against a common diaphragm
 causes the diaphragm to press against the second fluid oscillator,
 emptying the second fluid oscillator.
 SUMMARY OF THE INVENTION
 Accordingly, it is an object of the present invention to develop a fluid
 control circuit having a plurality of fluid oscillators which can
 circulate the working fluid successively to each particular fluid
 oscillator without requiring the opening and closing of a series of
 valves.
 To this end, according to the present invention, there is provided a
 valve-less fluid control circuit for controlling rhythmic action devices,
 such as circulatory assist devices. The fluid control circuit has a
 plurality of pressure sensitive fluid oscillators for circulating a fluid.
 Each fluid oscillator includes a capacitance chamber unit for peristaltic
 pumping of fluid after being filled via an input conduit and a resistance
 conduit. A first control conduit provides an outlet of fluid from the
 capacitance unit during peristaltic pumping, and when the pressure of the
 fluid in the first control conduit reaches a certain level relative to the
 pressure of fluid in the input conduit, the fluid is directed through an
 interactive region and exits the first fluid oscillator through an exhaust
 conduit. A coupling unit couples the output of the first fluid oscillator
 to the input conduit of the successive fluid oscillator, so that the
 expansion and contraction of the capacitance chambers occurs successively
 without the need for valves and/or complicated control circuitry, such as
 solenoids and cams. A return conduit at the last fluid oscillator returns
 the fluid to a second control conduit of the first fluid oscillator to
 refill the first capacitance chamber.
 More particularly, the present invention is directed to a fluid control
 circuit for controlling rhythmic action devices, the fluid control circuit
 comprising a plurality of pressure sensitive fluid oscillators coupled
 together in a ring configuration for circulating a fluid, wherein each of
 the fluid oscillators comprises: an input conduit having a first end for
 receiving a working fluid; an interactive region communicating with a
 second end of the input conduit; a resistance conduit having a first end
 communicating with the interactive region; capacitance chamber means for
 storing the working fluid and for providing a peristaltic pumping of the
 working fluid, the capacitance chamber means communicating with a second
 end of the resistance conduit; an exhaust conduit communicating with the
 interactive region; a first control conduit for controlling a direction of
 the flow of the working fluid entering the interactive region, the first
 control conduit communicating at a first end with the capacitance chamber
 means and at a second end with the interactive region, so as to provide an
 output path of the working fluid pumped from the capacitance chamber
 means, the first control conduit communicating with the interactive region
 at an angle relative to the input conduit so that when a fluid pressure of
 the working fluid in the first control conduit reaches a certain
 predetermined level relative to the fluid pressure in the input conduit,
 the first control conduit controls a flow direction of the working fluid
 entering the interactive region from the input conduit, so as to direct
 the flow toward the exhaust conduit; and wherein the fluid control circuit
 further comprises coupling means for coupling the plurality of fluid
 oscillators together so that an output from the exhaust conduit of each
 fluid oscillator is coupled to the input conduit of a successive one of
 the fluid oscillators in the ring configuration, so that the working fluid
 circulates successively through the respective capacitance chambers of the
 fluid control circuit without valves.
 The first fluid oscillator of the plurality of fluid oscillators may
 further comprise a second control conduit communicating with the
 interactive region at an angle relative to the input conduit, so that when
 a fluid pressure of the working fluid in the second control conduit
 reaches a certain predetermined level relative to the fluid pressure in
 the input conduit, the second control conduit controls the direction of
 the working fluid to flow towards the capacitance chamber means; and a
 last fluid oscillator of the plurality of oscillators may comprise a
 return conduit having a first end communicating with the exhaust conduit
 of the last fluid oscillator, and a second end communicating with the
 second control conduit of the first fluid oscillator, so that at least a
 portion of the working fluid exiting the last oscillator is recirculated
 to the first fluid oscillator from the return conduit to the second
 control conduit, so as to control the direction of the fluid to flow
 towards the capacitance chamber means.
 The capacitance chamber means of the plurality of fluid oscillators may
 include expandable sleeves which successively expand and contract as the
 working fluid is circulated successively through each of the plurality of
 fluid oscillators.
 The device means for coupling may include venting means arranged between
 the exhaust conduit of one of the fluid oscillators and the input conduit
 of a successive one of the fluid oscillators.
 At least one of the fluid oscillators may comprise a valve-less booster
 pump arranged at one of (i) the input conduit, (ii) the coupling means,
 and (iii) the exhaust conduit or at least one fluid oscillator which
 comprises a centrifugal pump arranged at one of (i) the input conduit,
 (ii) the coupling means, and (iii) the exhaust conduit.
 The device may further comprise pressure adjustment means for adjusting a
 working fluid pressure in at least one of the first conduit, the second
 conduit, and the return conduit. The pressure adjustment means may
 comprise a valve-less pump.
 The device may further comprise temperature control means to heat and cool
 the fluid.
 According to another aspect of the present invention, there is provided a
 circulatory assist device comprising a fluid control circuit for
 controlling rhythmic action devices, the fluid control circuit comprising
 a plurality of pressure sensitive fluid oscillators coupled together in a
 ring configuration for circulating a fluid, wherein each of the fluid
 oscillators comprises: an input conduit having a first end for receiving a
 working fluid; an interactive region communicating with a second end of
 the input conduit; a resistance conduit having a first end communicating
 with the interactive region; capacitance chamber means for storing the
 working fluid and for providing a peristaltic pumping of the working
 fluid, the capacitance chamber means communicating with a second end of
 the resistance conduit; an exhaust conduit communicating with the
 interactive region; a first control conduit for controlling a direction of
 the flow of the working fluid entering the interactive region, the first
 control conduit communicating at a first end with the capacitance chamber
 means and at a second end with the interactive region, so as to provide an
 output path of the working fluid pumped from the capacitance chamber
 means, the first control conduit communicating with the interactive region
 at an angle relative to the input conduit so that when a fluid pressure of
 the working fluid in the first control conduit reaches a certain
 predetermined level relative to the fluid pressure in the input conduit,
 the first control conduit controls a flow direction of the working fluid
 entering the interactive region from the input conduit, so as to direct
 the flow toward the exhaust conduit; and wherein the fluid control circuit
 further comprises coupling means for coupling the plurality of fluid
 oscillators together so that an output from the exhaust conduit of each
 fluid oscillator is coupled to the input conduit of a successive one of
 the fluid oscillators in the ring configuration, so that the working fluid
 circulates successively through the respective capacitance chambers of the
 fluid control circuit without valves, and wherein the capacitance chamber
 means of each of the fluid oscillators comprises expandable sleeve means
 for wrapping around at least a portion of a limb of a patient, and the
 sleeve means of the plurality of fluid oscillators are coupled to each
 other so that the sleeve means expand and contract successively in the
 plurality of fluid oscillators as the working fluid circulates through the
 fluid control circuit. The fluid in each of the expandable sleeve means
 may comprise air or a liquid.
 The circulatory assist device may further comprise temperature control
 means to heat and cool the air or the liquid.
 The circulatory assist device may further comprise pressure adjustment
 means for adjusting a fluid pressure in at least one of the first control
 conduit, the second control conduit, and the return conduit.
 The circulatory assist device may further comprise line pressure sustaining
 means for sustaining line pressure in the fluid control circuit and
 comprising an auxiliary valve-less pumping compartment arranged between at
 least two of the fluid oscillators.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 An embodiment of the valve-less fluid control circuit of the present
 invention is shown in FIGS. 1 through 4.
 In FIG. 1, a fluid control circuit includes a first fluid oscillator 1, a
 second fluid oscillator 9, a third (or last) fluid oscillator 16, and
 assorted coupling mechanisms 24, 25 for coupling the fluid oscillators
 together.
 As shown in FIG. 1, first fluid oscillator 1 has an input conduit 2 which
 receives a working fluid (represented by arrow A) at a first end.
 Initially, if the working fluid is a liquid, a valve-less pump (not shown)
 may propel the working fluid into conduit 2. However, if the working fluid
 is air, a compressor (not shown) may be used instead of a pump. It is also
 within the scope of the invention that the working fluid may include a
 combination of liquid and air, requiring a suitable propulsion device.
 The working fluid in input conduit 2 travels toward interactive region 3.
 Interactive region 3 is formed at the intersection of input conduit 2,
 resistance conduit 4, first control conduit 6, second control conduit 7,
 and exhaust conduit 8.
 The interactive region 3 is formed so that the working fluid normally flows
 from input conduit 2 to interactive region 3, then to resistance conduit
 4. The resistance conduit 4 is connected with a first pumping cuff 5,
 which comprises an expansive capacitance chamber which is expandable to a
 maximum size shown by the solid line and is represented in an empty or
 deflated state by the dashed line (not drawn to scale).
 The first pumping cuff 5 is provided for two purposes. The first purpose is
 to provide the capacitance required to hold the working fluid. The second
 purpose is for providing a peristaltic pumping of the working fluid from
 the first fluid oscillator 1 into the second (or successive) fluid
 oscillator 9 without opening and closing of valves.
 As the first pumping cuff 5 fills with working fluid, the chamber expands
 so as to begin the first stage of the peristaltic pumping. As the working
 fluid continues to enter the first pumping cuff 5, the pressure inside the
 pumping cuff continues to increase.
 When the pressure of the working fluid inside the pumping cuff 5 reaches a
 certain level, it begins to exit the first pumping cuff 5 through the
 first control conduit 6, even as input fluid continues to enter the first
 pumping cuff 5 from the resistance conduit 4. The pressure of the working
 fluid passing through the first control conduit 6 is proportional to the
 pressure in the pumping cuff 5.
 At a prescribed pressure, the working fluid in the first control conduit 6
 will be sufficient to force the working fluid entering the interactive
 region 3 (from input conduit 2) to flow toward exhaust conduit 8.
 When the working fluid is being directed away from the resistance conduit 4
 and is not entering first pumping cuff 5, there is a contraction of the
 first pumping cuff 5 (part of the peristaltic process). The working fluid
 remaining in the pumping cuff is forced out by the contraction and flows
 toward the exhaust conduit 8. The exhaust conduit 8 is coupled to the
 input conduit of the second fluid oscillator 9.
 Thus, the first fluid oscillator 1 of the fluid control circuit switches
 the flow of the working fluid without the use of any valves or solenoid
 mechanisms which would be required in the fluid control circuits of the
 prior art.
 The second fluid oscillator 9 (FIG. 2) receives the working fluid by input
 conduit 10 connected to exhaust conduit of the first fluid oscillator 1.
 The working fluid flows toward interactive region 11 of second oscillator
 9. The construction of the second fluid oscillator 9 is similar to the
 first fluid oscillator 1 in that the input fluid will flow towards the
 resistance conduit 12 and into the second pumping cuff 13 comprising a
 second expansive capacitance chamber.
 The second pumping cuff 13 fills with fluid and begins to expand, which
 begins the second stage of the peristaltic pumping process.
 Similar to the action in the first fluid oscillator 1, part of the working
 fluid in the second pumping cuff 13 begins to flow through first control
 conduit 14 at an increasing rate of pressure.
 When the pressure of the working fluid flowing through first control
 conduit 14 reaches a certain magnitude, the working fluid entering the
 interactive region 11 (from input conduit 10) will be directed toward the
 exhaust conduit 15.
 Thereafter, the second pumping cuff 13 contracts because there is no longer
 an input of working fluid into its chamber.
 This contraction forces the remaining fluid out of the second pumping cuff
 toward the exhaust conduit 15.
 The third fluid oscillator 16 (FIG. 3) is coupled to both the second fluid
 oscillator 9 to receive the working fluid and the first fluid oscillator 1
 to begin a recirculation of the working fluid.
 The input conduit 17 of the third fluid oscillator 16 is coupled to the
 exhaust conduit 15 of the second fluid oscillator 9 (coupling not shown),
 so that the fluid from the second fluid oscillator 9 enters the third
 fluid oscillator 16 and fills the third third pumping cuff 20 comprising a
 third expansive capacitance chamber via interactive region 18 and
 resistance conduit 19.
 The third pumping cuff 20 begins to expand as it fills with working fluid,
 starting the third stage of the peristaltic pumping process.
 The pressure of the working fluid flowing through first control conduit 21
 begins to increase as the pressure of the fluid inside the third pumping
 cuff 20 increases.
 Similar to the operation of the first and second fluid oscillators, the
 working fluid in the third fluid oscillator flowing from the first control
 conduit 21 to the interactive region 18 begins to divert the working fluid
 entering interactive region 18 (from input conduit 17) so that it flows
 toward exhaust conduit 22.
 At this time, the third pumping cuff 20 contracts because the working fluid
 is no longer entering its chamber to retain the expanded condition, and
 the remaining working fluid in the third pumping cuff 20 is forced out
 towards the exhaust conduit 22.
 The exhaust conduit 22 is coupled (coupling not shown) to the input conduit
 2 of the first fluid oscillator, and a return conduit 23 is coupled
 (coupling not shown) to the second control conduit 7 of the first fluid
 oscillator 1.
 Accordingly, the working fluid flowing from return conduit 23 to second
 control conduit 7 will force the fluid flowing from exhaust conduit 22
 (into input conduit 2) to be directed to the first pumping cuff 5 via the
 resistance conduit 4. In this manner, the peristaltic pumping operation
 can be restarted.
 FIGS. 4(a)-(c) show three possible coupling units for the fluid control
 circuit of the present invention.
 FIG. 4(a) illustrates a clamp 24 including a screw assembly 24a which may
 be used to connect the exhaust conduit of one fluid oscillator to the
 input conduit of a successive fluid oscillator.
 FIG. 4(b) shows a sleeve 25 which would receive both the exhaust conduit of
 one fluid oscillator and the input conduit of a successive fluid
 oscillator.
 FIG. 4(c) is a block diagram of a coupling device including a valve-less
 booster pump/vent 26 which may be used for coupling the output of one
 fluid oscillator to the input conduit of a successive fluid oscillator.
 The inline pressure may be sustained at a prescribed level by the booster
 pump. Additionally, venting of the fluid may be provided by a vent
 connected with the pump. Those of ordinary skill in the art would know
 that the actual arrangement of the venting within the fluid control
 circuit would be dependent upon a particular application of the invention.
 One particular application of the above-described fluid control circuit is
 as a circulatory assist device, for example, for aiding a patient who is
 either bed-ridden or has a weak heart, whereby the pumping cuffs
 sequentially compress portions of a limb (or limbs) to prevent fluid
 retention. However, it will be understood by those of ordinary skill in
 the art that this invention has many applications and is not limited to
 circulatory assist devices.
 The number of fluid oscillators in the fluid control circuit may be
 increased according as needed. It will be understood by those of ordinary
 skill in the art that variations and modifications of the arrangement of
 the conduits and their shape may be effected as necessary to suit a
 particular application.
 It is also within the scope of the invention to use a combination of the
 coupling devices shown in FIGS. 2-4, as well as other coupling devices
 known in the art.
 The first fluid oscillator 1 may include a valve-less booster pump 26 or a
 compressor (not shown) connected to the input conduit 2 in a multiple
 connection (such as a T-connection), so that the pump or compressor can
 begin the flow of the working fluid in the fluid control circuit from a
 reservoir portion. The T-connection allows the working fluid to enter the
 input conduit 2 of the first fluid oscillator 1 after circulating through
 the third (or last) fluid oscillator 16.
 Although the present invention has been fully described by way of example
 with reference to the accompanying drawings, it should be understood that
 numerous variations, modifications and substitutions, as well as
 rearrangements and combinations, of the preceding embodiments will be
 apparent to those skilled in the art without departing from the novel
 spirit and scope of this invention, and the appended claims.