Apparatus for generating pulses of fluid pressure

Abstract

Apparatus for supplying pulses of fluid pressure to a chamber has means for supplying pressurized fluid to the chamber and means responsive to the pressure of the fluid in the chamber for controlling the supply means to provide pulses of pressure fluid. Additional means for sequentially selecting one of a plurality of such chambers to be supplied with pressure are provided in a preferred embodiment and the control, selecting and sequencing means are fluidic elements.

Description

BACKGROUND OF THE INVENTION

The arts of fluid pressure devices are among the oldest known to man. Some have been in continuous use at least from the classic Greek period. In spite of the age of these arts, new developments continue to be made.

One recent contribution is the art of fluidics in which fluid flow is utilized to perform control functions. Devices for performing both logic and sensing control functions are known.

Another recent development is described in U.S. Pat. No. 3,179,106 issued Apr. 20, 1965, in the name of Paul A. Meredith. This patent discloses a method and apparatus for preventing venous blood clotting through the application of rapid pulses of minimal external pressure to human body members. The pressure is applied by inflatable bladders fashioned to fit about the body members. The bladders are connected to pressure chambers having mechanically driven diaphragms for generating pressure pulses in the connected bladders. The mechanical diaphragm pressure system is subject to wear. Additionally, the bladders have flexible walls for conforming to body members and for patient comfort. Accordingly, the bladders vary in inflatable volume through the application of body member weight to the flexible walls of the bladder. As the volume of the bladder varies, the pressure generated by particular movement of the pressure generating diaphragm also varys. Since the particular pressure applied to the body members is an important part of the treatment, such a result is undesirable.

An improvement to the apparatus for providing pressure pulses is disclosed in U.S. Pat. No. 3,307,533 issued Mar. 7, 1967 in the name of Paul A. Meredith et al. This patent discloses an electro-mechanically driven, rotary valve providing both means for applying pressure to bladders and means for exhausting air from the bladders. Again, no pressure-responsive means are provided and the electromechanical drive requires a source of electric power rendering the apparatus less portable than if such power were not required.

SUMMARY OF THE INVENTION

Accordingly, an object of the invention is to provide pressure responsive, portable apparatus for producing pulses of fluid pressure particularly useful for inflating bladders applying pressure to body members.

To this end, the invention has a source of pressurized fluid and means for supplying the pressurized fluid to a chamber which, preferably, is an inflatable bladder. Means responsive to the pressure of the fluid in a chamber controls the supply means to provide a pulse of fluid pressure to the chamber. In a preferred embodiment, means for selecting and means for sequencing among a number of chambers to be supplied with fluid pressure are provided. The preferred embodiment is additionally entirely of fluidic control elements so as to improve portability of the apparatus.

DESCRIPTION OF THE DRAWINGS

A preferred embodiment will now be described with reference to a schematic of the embodiment which is intended to be illustrative of and not a limitation on the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The schematic of the preferred embodiment has three cooperatively connected sections. The first section generally indicated at 10 sequences the application of pressure to one bladder 12 of a plurality of bladders. A second section of the schematic generally at 14 controls the sequential application of pressure as pulses. A third section of the schematic generally at 16 determines the time between successive, sequential pressure pulses supplied to the bladders. Accordingly, a bladder is selected for inflation by the sequence section of the schematic, the selected bladder pulsed with pressure fluid until the control section 14 terminates the pressure, and the apparatus then remains quiescent until the timing section 16 signals the sequencing section to again select and supply a bladder with pressure. All of the elements of the schematic are fluidic and accordingly may be operated from a source (not shown) of pressure fluid, preferably air, to provide fluid flow control signals at appropriate ports of the elements.

The sequence section has a pair of flip-flops 18 and 20 for selectively driving a series of OR gates 22, 24 and 26 each of which is operatively connected to a valve 28, 30, and 32, respectively, which controls the supply of pressurized air to a bladder. Each of the bladders and valves 28, 30 and 32 is of similar construction and operation; accordingly, only the construction and operation of bladder 12 and connected valve 32 need be described.

An input signal responsive port 34, 36 and 38 of each of the OR gates 22, 24 and 26, respectively, is connected to a one-shot device 40, 42 and 44, respectively, each through an OR gate 46 for power amplification. A signal responsive output of each one-shot 40 and 42 communicates with a control port 46 and 48 of the flip-flops 18 and 20, respectively, while a signal responsive output from one-shot 44 communicates with control ports 50 and 52 of the flip-flops 18 and 20, respectively, which ports are complementary to the ports 46 and 48.

The flip-flops 18 and 20 perform the sequencing function. An output port 54 of the flip-flop 18 is responsive to a control signal at the control port 46 and is connected to an input control port 56 of the OR gate 22 to which a signal at the output port 34 is responsive. Similarly, an output port 58 responsive to a signal at the input control port 50 of the flip-flop 18 is connected to an input control port of both OR gates 24 and 26 to which a signal at the output ports 36 and 38 is responsive. The flip-flop 20 is similarly connected with an output port 60 responsive to a signal at the control port 48 connected for controlling an output signal at the port 36 and an output port 62 responsive to an input control signal at the port 52 connected for controlling an output at the port 38. Since each of the flip-flops 18 and 20 continually provide an output signal at one, but only one, of their output ports, the above described connections provide an input control signal to two of the OR gates 22, 24, and 26 in each possible combination of their output signals.

Fluid flow signals from the output ports 34, 36 and 38 are connected to control their respective valves 28, 30 and 32 such that the valves are driven to the left from the position shown in the schematic in response to a signal at the ports. As seen in relation to the valve 32, the pressure fluid input line will then be closed and the pressure line connecting the valve with the bladder 12 will be connected to exhaust to atmosphere. The bladder 12 will then be deflated. On the other hand, when no signal is provided to an input control port of the OR gate 26, the gate provides a normally on output signal at the port 64. The port 64 is connected to an input control port of the valve 32 such that the valve is driven to the position shown in the schematic in which the fluid pressure source is connected to the bladder 12.

Only one bladder 12 is shown in the control section of the schematic 14 because operation of each bladder is similar and only one bladder is sequentially inflated at a time by the sequence section logic. The bladder 12 is also connected to a pressure control port 66 of a Schmitt trigger 68. An adjustable reference pressure is provided at an input port 70 opposing the pressure at port 66. So long as the reference pressure at the port 60 exceeds that at the port 66, the Schmitt trigger provides an output signal only to the exhaust port 72. However, when the pressure in the bladder as applied to the port 66 exceeds the reference pressure at the port 70, the output of the Schmitt trigger switches to the port 74 connected to a flip-flop 76 in the sequence section 10 of the schematic. Adjustment of the reference pressure accordingly adjusts the pressure in the bladder which will trigger a signal to the flip-flop 76.

The Schmitt trigger 68 is physically close to the bladder 12 to maximize pressure sensing sensitivity of the trigger. Longer connecting lines 90 to the trigger require finitely longer real time for fluid pressure to advance from the bladder to the trigger than shorter lines. In addition, elasticity or leakage in the connecting lines may further decrease the pressure sensing sensitivity of the trigger. Accordingly, the trigger is preferably mounted on the bladder. However, operability of the preferred embodiment is not limited to such mounting and the trigger may be grouped with the other fluidic elements remote from the bladder.

A signal at an output port 78 of the flip-flop 76 is responsive to a control signal from the Schmitt trigger. The output port 78 is connected to an input control port of each of the OR gates 22, 24 and 26 so as to complement the gates to provide a signal at their output ports 34, 36 and 38 respectively; of course, only one of the gates 22, 24 and 26 will not already be providing an output signal to its port 34, 36 or 38 under the influence of signals from the flip-flops 18 and 20 at another input control port. Accordingly, only one of the OR gates will actually complement in response to a single signal from the output port 78 of the flip-flop 76. Since the operation of each of the OR gates 22, 24 and 26 is analogous, as already noted, only one need be described.

It may be assumed that the embodiment is in the state illustrated in the schematic in which a signal at the output ports 34 and 36 prevents inflation of the bladders (not shown) connected to the corresponding valves 28 and 30 and has produced an evanescent signal from the one-shots 40 and 42 which are now self-disabled. The signal from the one-shots 40 and 42 has appeared at the control ports 46 and 48 of the flip-flops 18 and 20 complementing the flip-flops to provide an output signal at the ports 54 and 60, respectively, which latches the OR gates 22 and 24 with an output signal at their ports 34 and 36. The flip-flops 18 and 20 are bi-stable devices and, accordingly, will not complement from set state until they receive an active, complementing signal.

In contrast to the OR gates 22 and 24, the OR gate 26 has been in its stable condition with an output at its port 64 maintaining the valve 32 in position to supply air to the bladder 12. The signal from the output port 78 of the flip-flop 76 then complements the OR gate 26 to provide a signal at its output port 38. The signal at the port 38 complements the valve 32 to block further pressure fluid input to the bladder 12 and to connect the bladder to atmosphere for deflation and, simultaneously, provides a signal to the connected one-shot 44. The one-shot 44 then operates to provide a signal of predetermined time duration to its output port connected to the control ports 50 and 52 of the flip-flops 18 and 20. The signal duration from the one-shot 44, as well as that from the one-shots 40 and 42, is predetermined to be long enough to complement the flip-flops 18 and 20 but less than the least time required to inflate one of the bladders so that simultaneous signals from more than one of the one-shots cannot cause an indeterminate state in either of the flip-flops 18 or 20.

The signal to the input control ports 50 and 52 of the flip-flops 18 and 20 complements both of the flip-flops to provide an output at the output ports 58 and 62 for ultimately sequentially selecting a bladder to receive fluid. None of the OR gates 22, 24 or 26 immediately complements, however, as they are already maintained in their unstable condition by the signal from the output port 78 of the flip-flop 76 which continues until the flip-flop 76 is complemented.

The timing circuit 16 provides a complementing signal to the flip-flop 76. For this purpose, a timer 80 provides a signal at an output port connected to an input control port of a flip-flop 82. This signal complements the flip-flop 82 to provide an output signal at an output port 84 connected to an input control port of the flip-flop 76 complementary in control to the input port connected to the Schmitt FIG. 68. Since the bladder 12 has deflated, the output of the Schmitt trigger 68 has returned to the port 72 and the signal from the port 84 of the flip-flop 82 is thus effective to complement the flip-flop 76. No signal then appears that the output port 78 of the flip-flop 76 and the one of the OR gates 22, 24 and 26 not then otherwise disabled by the flip-flops 18 and 20, OR gate 22 in the state assumed above, returns to its stable output condition. The valve responsive to the stable output of that OR gate moves to the right, as seen in the schematic, to inflate the bladder connected to the valve. For example, the OR gate 26 would provide an output signal at the port 64 to drive the valve 32 to the right.

To avoid an indeterminate condition in the flip-flop 76 and to initiate timing of the cycle of the bladder then inflating, the signal from the port 84 of the flip-flop 82 is also conducted to a time delay relay 86 which, after a predetermined time, provides an output pulse signal to an input control port of the flip-flop 82 so as to complement that flip-flop. The predetermined time delay is such as to continue the signal from the flip-flop 82 to the flip-flop 76 long enough to insure complementing of the flip-flop 76 but less than the minimum time required to so inflate any of the bladders as to complement the Schmitt trigger 68. An indeterminate state in the flip-flop 76 is thus avoided. This timing cycle is repeated for the sequential inflation of each bladder.

Since the total real time cycle for inflating and deflating the bladder and a quiescent period between bladder inflations is controlled by the timer 80, the timer is provided with means for adjusting the time interval. In the preferred embodiment, the interval adjusting means is a manually adjustable throttle 88 which may be preset for any interval. Preferably, the interval is such as will provide the cycle of operation described in the above recited U.S. Pat. No. 3,179,106.

This patent additionally describes a longer quiescent period after each of the bladders has been sequentially inflated. For this purpose in an alternative embodiment of the invention, the throttle 88 may be responsive to inflation of a selected bladder to provide a longer timing interval and to inflation of other bladders to provide a shorter interval. For example, the port 64 of the OR gate 26 may be connected to means (not shown) for adjusting the throttle 88 to one predetermined position while the corresponding ports of the OR gates 22 and 24 each adjust the throttle to another predetermined position.

In another alternative embodiment of the invention the number of bladders to be sequentially inflated may be increased or decreased with appropriate expansion or diminution of the sequence logic in section 10 of the schematic. The preferred embodiment will also operate one or more bladders by connecting only the desired number of bladders to one of the valves 28, 30 and 32. Similarly, each of the bladders described may have several discrete sections; for example, a section for embracing each arm of a patient upon whom the apparatus is used.

Still other alternative embodiments are contemplated within the scope of the invention defined by the following claims:

Claims

I claim:

1. Apparatus for sequentially supplying fluid pressure to a system of more than two bladders according to a predetermined sequence, said bladders being adapted to apply external pressure to portions of the human body comprising:

A. a source of pressurized fluid connected to each bladder;

B. a valve connected to each bladder for controlling the flow of pressurized fluid thereto;

C. means in each bladder for sensing the pressure therein;

D. a selector for generating fluid pressure signals for actuating the pressure control valves of the bladders according to the predetermined sequence;

E. means to receive the pressure from the pressure sensors, compare said pressure with a predetermined value, and generate a fluid pressure signal when a predetermined relation between said pressures exists;

F. means responsive to the fluid pressure signals from the selector and the pressure comparator to sequentially actuate the valves to inflate and deflate the bladders; and

G. timing means associated with the pressure comparator to control the overall cycling time of each bladder.