Fluid Pressure Controlled Means For Producing Peristaltic Operation Of Series-connected Inflatable Chambers In Therapeutic Devices, Pumps And The Like

Abstract

A device comprising a series of inflatable chambers connected in series by valve means operative to produce a continuous propagation of pressure pulses sequentially along the series of chambers by controlled inflation and deflation of the chambers. Embodiments are shown in therapeutic devices for lowering the incidence of thromboembolism and for generally improving veinous and secondary blood flow. Another embodiment is shown as a peristaltic pump. No distributor is required for the requisite timed inflation and deflation of successive chambers, such timed operation being achieved by a plurality of valve means which may be identical, one such valve means connecting each successive pair of connecting chambers to form a series. The supply of fluid pressure to and the exhausting of fluid pressure from successive chambers in the series is controlled by elements of each valve means which are responsive to the differential in pressure between the pair of chambers connected by that valve means. Due to employment of such valve means the chambers may be modular units and the valve means may be modular units whereby chambers and valve means may be plugged together to make a series of any desired length. When embodied as a therapeutic device it may be assembled by unskilled persons and applied to patients in widely different age and body contour groups. BACKGROUND OF THE INVENTION The invention disclosed herein is embodied in therapeutic devices and in a form of peristaltic pump. Considered first from the standpoint of therapeutic devices the following patents are illustrative of the prior art of which applicant is aware. U.S. Pat. Nos. 2,528,843 and 2,533,504 disclose devices in which separate inflatable chambers are attached together as a group and individually fitted to the contours of the limb of a patient. U.S. Pat. Nos. 1,608,239; 2,345,073 and 2,361,242 disclose devices in which separate inflatable chambers are incorporated in garment-like structures which adjustably encompass the limbs and torso of a patient. British Pat. No. 483,111 and related British Pat. No. 483,132 of Apr. 12, 1938 disclose a device in which separate inflatable chambers are incorporated in a gaiter which adjustably encompasses the limb of a patient. In all of the patents listed above a fluid such as air, is pressurized and supplied to a mechanically driven distributor valve arrangement from which the pressurized air is individually conducted by separate tubes to the inflatable chambers. In some cases the chambers are divided into groups served by common ports in the distributor valve and by branching tubes thus reducing the number of tubes which must run all the way back to the distributor valve. In all cases, however, a great number of tubes is required and the complete device is bulky, complicated and likely to require close supervision in operation. Considered, second, from the standpoint of peristaltic pumps, U.S. Pat. No. 3,429,266 discloses an arrangement of inflatable chambers through which a flexible tube extends exposed directly to the pressurized fluid supplied to the chambers in an appropriate sequence. The pressurized fluid tends to collapse the flexible tube thus forcing a flowable material therein to progress along the flexible tube in a manner typical of peristaltic pumps. In this patent an air compressor and a mechanically driven distributor valve is used to supply the chambers through individual tubes which all extend from the distributor to the particular chamber which each tube serves. French Patent No. 1,175,431 discloses several modified forms of peristaltic pumps including several in which common mechanically driven distributor valves are used and one in which a fluid pressure operated supply and exhaust valve and a fluid pressure operated pilot valve are used for each inflatable chamber in the series. The pilot valve for each chamber senses the pressure in the chamber against the pressure in the supply manifold. When the pressure in that chamber rises substantially to equal the supply pressure the pilot valve sends a fluid pressure signal to the supply and exhaust valve of the immediately preceding chamber to initiate exhaust of that chamber and simultaneously sends a fluid pressure signal to the supply and exhaust valve of the immediately following chamber to initiate inflation of that chamber. When that following chamber is fully inflated, as measured against supply pressure, the pilot valve thereof will send appropriate signals to the supply and exhaust valves of the chambers which now precede and follow it. For this device to operate continuously, once it is started, the pilot valve and supply and exhaust valve of the last chamber in the series must be connected with the valves of the first chamber in the series. To stop this device each supply and exhaust valve must be manually pushed into the exhaust mode. To start this device all supply and exhaust valves must be in the exhaust mode and a cock in a special conduit must be manually opened so that the first chamber may be pressurized. The starter cock must be closed as soon as the pump starts in order to prevent the first chamber from remaining inflated and permanently blocking the system. SUMMARY OF THE INVENTION In contrast with the prior art of which applicant is aware this invention provides in combinations, such as therapeutic devices and peristaltic pumps, wherein a continuous propagation of pressure pulses is produced sequentially along a series of chambers by controlled inflation and deflation of such chambers, the control of the required inflation and deflation by valve means which operate automatically to open and close inlet and exhaust passageways for each chamber in response to the differential in fluid pressure between that chamber and the chambers in the series which immediately precede and immediately follow that chamber. A valve means of this type is disposed between each pair of immediately adjacent chambers in the series. With this arrangement the series of chambers may be made up of any required number of chambers, the last chamber in any such series is not connected back to the first in the series, the operation of the series is self starting irrespective of the random modes in which the valve means may be when start-up is required and no mechanically operated distributor, timing device or equivalent thereof is utilized. The frequency of the complete cycle of inflation and deflation of each chamber and the rate of propagation of waves of pressure along the series is predetermined by the characteristics of valve means as related to the characteristics of the inflatable chambers. Preferred, but exemplary, forms of valve means forming a part of this invention comprise body parts which are movable relative to one another by oscillation about an axis between two stable positions in response to the differential in fluid pressure existing in two adjacent chambers of the series. These, or equivalent, valve means may be made in modular form for connecting a series of modular inflatable chambers into a series of any desired length or they may be used in non-modular embodiments providing a selected number of permanently arranged chambers for specific applications. When embodied in therapeutic devices the present invention provides combinations that may be started or stopped or monitored in operation by unskilled personnel and which do not require, and thus preferably do not have, any adjustable controls or other elements which, if provided or required, could be improperly adjusted or tampered with by unskilled personnel. Such therapeutic devices are for the purpose of preventing or reducing the formation of thromboembolism and for generally improving veinous blood flow. They serve to prevent stasis in the deep veins of the limbs of persons who are hospitalized, operative, non-ambulatory or otherwise recumbent or non-active and they also provide peristaltic pumping action to assist normal veinous blood from flow when such is required or desirable.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a somewhat diagrammatic perspective view of a therapeutic device embodying the present invention and showing it applied to the lower leg of a patient;

FIG. 2 is a perspective view of one of the inflatable toroidal chambers shown in FIG. 1;

FIG. 3 is a perspective view of a modular valve means for use in assembling a device such as that illustrated in FIG. 1;

FIG. 4 is a horizontal sectional view taken generally along the line 4--4 in FIG. 3 and showing interior parts of the valve means in one stable position;

FIG. 5 is a view similar to FIG. 4 but showing the interior parts of the valve means in a second stable position;

FIG. 6 is a vertical sectional view taken along either of the lines B--B in FIG. 1;

FIG. 7 is a view similar to FIG. 4 but showing a modified form of valve means;

FIG. 8 is a view similar to FIG. 5 but showing the modified form of valve means illustrated in FIG. 7;

FIG. 9 is a diagrammatic view for use in explaining the operation of the valve means shown in FIGS. 4 and 5;

FIG. 10 is a diagrammatic view similar to FIG. 9 but showing a different operative relationship of certain elements of the valve means;

FIG. 11 is a perspective view of a modified form of toroidal chamber which may be used in the present invention;

FIG. 12 is a sectional view along the lines 12--12 in FIG. 11;

FIG. 13 is a perspective view of a modified form of therapeutic device similar in some respects to that shown in FIG. 1;

FIG. 14 is a sectional view taken along the lines 14--14 in FIG. 13; and

FIG. 15 is a somewhat diagrammatic view illustrating an embodiment of the present invention in a peristaltic pump.

DESCRIPTION OF PREFERRED EMBODIMENT

Referring now to the drawings in FIG. 1 a preferred embodiment of the present invention is shown as a therapeutic device fitted to the lower leg of a patient. The device comprises a series of separate, modular hollow chambers of toroidal shape, made of an elastomeric fluid-tight material each of which is capable of being expanded and contracted in radial directions respectively in response to the introduction of a pressurized fluid into the interior thereof and the exhausting of such fluid from the interior by opening the interior to a region of lower fluid pressure. Most conveniently the fluid may be ambient air pressurized by a compressor and the exhaust region may be the ambient atmosphere in which the patient is located, although any suitable gaseous or liquid fluid may be used if so desired. For therapeutic or patient-comfort reasons the fluid may be warmed or cooled by suitable devices, not shown, if the temperature of the compressed or pressurized fluid is not otherwise suitable.

In FIG. 1 there is diagrammatically shown a pressurizing device 10, illustratively an air compressor, connected with a supply manifold 12. The toroidal chambers are identified as a series starting with n-2 near the ankle of the patient, and progressing through n-1, n, n+1, n+2, et seq. to a position near the knee of the patient. The internal and external diameters of the chambers n-2, et seq. may be varied individually or in groups in accordance with the contours of the portion of the human body to which they are to be fitted. In the illustrative example the toroidal chambers near the ankle are relatively small in such diameters and chambers having greater diameters are progressively distributed over the calf and to the region of the knee. The size and distribution of the modular toroidal chambers should be such that when each is in the deflated or contracted condition the inner diameter will surround the patient's leg in a relatively loose condition, not exerting any substantial radially inward pressure upon the surrounded tissue. When each toroidal chamber is inflated or expanded the inner diameter will be reduced and a yielding radially inward pressure will be exerted upon the surrounded tissue.

It is intended that the user of this invention will have available from inventory or from a medical supply house a rather widely ranging selection of sizes of the modular toroidal chambers to make possible the selection of properly fitting series for the upper and lower portions of the arms and legs of persons of differing bodily contours within all age groups.

As explained more fully in the above generalized description of the present invention the pressurized fluid is directed to and exhausted from the individual toroidal chambers n-2 et seq. in a predetermined repetitive sequence such as to provide continuous stressing and unstressing of the tissues in the regions surrounding the blood vessels of a patient in a continuous pattern of pressure pulses which are propagated wave-like along the series of toroidal chambers. At any given moment several of the toroidal chambers will be at or near maximum fluid pressure while others are at or near minimum fluid pressure and the remaining toroidal chambers which lie between those at high or low pressure will be under rapidly increasing or decreasing pressure.

In this preferred form of the invention wherein the chambers n-2, et seq. are modular there are provided modular valve means which serve as physical connections between each chamber and the chamber immediately downstream thereof, thus to establish the series. Each of these valve means includes elements which are responsive to the differential in fluid pressure between the two chambers which the valve means physically connects to control the supplying and exhausting of those chambers. As shown in FIG. 1 the valve means just referred to are shown as relatively small boxes 14 which are positioned in recesses 16 and 18 (FIG. 2) formed in each of the modular chambers n-2, et seq. Preferably the recesses 16 and 18 are offset radially of each chamber and open on opposite sides thereof as shown in FIG. 2 in order that when a series of chambers is connected as shown in FIG. 1 the valve means 14 will lie rather widely spaced along two spaced parallel lines thus causing less stiffening of the assembly of chambers than would be caused if all of the valve means 14 were arranged along a single line.

Each valve means 14 is connected by a tube 20 to the supply manifold 12 and is connected by a tube 22 to an exhaust manifold 24. Also each valve means 14 is connected, preferably by a suitable simple plug-in device with each of the chambers between which it is positioned. Illustratively, as shown in FIGS. 3 and 4, for example, each valve means 14 may be provided with beaded nipples 26, 28, 30 and 32 protruding from the four sides thereof. The supply tubes 20 may be made of elastomeric material and secured upon the nipples 26 of the several valve means 14 and the exhaust tubes 22 may be secured upon the nipples 28. The nipples 30 and 32 may be inserted into suitable openings, such as the opening 34 shown in FIG. 2, in the adjacent chambers in the series n-2 et seq.

Referring again to FIG. 1 the upstream end of the first toroidal chamber n-2 is connected by a tube 36 inserted into an opening such as 34 (FIG. 2) with a flow-restricting device 38 and and tube 40 with the supply manifold 12. Illustratively the flow-restricting device 38 may take the form shown in FIG. 6 with inlet and outlet nipples 42 and 44 separated by a disc 46 having an orifice 48 of predetermined small area through which compressed air flows constantly from manifold 12 to the interior of chamber n-2. As will be explained below chamber n-2 is connected to a valve means 14 in which an exhaust pathway is periodically opened and closed for chamber n-2. The rate of flow of the compressed air from manifold 12 to chamber n-2 is so determined by the flow-restricting device 38 that a predetermined period of time is required for the pressure in chamber n-2 to rise, when the exhaust is closed, substantially to the supply pressure maintained in manifold 12. When such pressure is reached it will hold at that level unless or until the pressure in the chamber n-1 is at or reaches exhaust level at which time the exhaust for chamber n-2 will open and pressure therein will drop rapidly even though the restricted flow of supply air continues through the device 38. The action just described is related with the timed operation of the series of chambers as will be more fully discussed below.

Similarly, in FIG. 1 there is shown a flow-restricting device 50 positioned in an exhaust tube 52 emerging from the last chamber n+6 and leading through a tube 54 to the exhaust manifold 24. The exhaust flow-restricting device 50 may be similar to or identical with the device 38 shown in FIG. 6 and the function thereof in relation to the timing of the series of chambers n-2 et seq. will be explained below. An adjustable throttle valve could be used instead of the simple flow-restricting devices 38 and 50 but such is not regarded as essential or advisable as will be made more clear hereinbelow.

Referring now to FIGS. 4 and 5 a typical valve means 14 is shown. For illustrative purposes it will be assumed that this particular valve means 14 is positioned between chambers n and n+1, the chamber n being the upstream chamber and the chamber n+1 being the downstream chamber with respect to this particular valve means 14. The position of the parts shown in FIG. 4 is that assumed during the time that pressurized fluid is flowing into upstream chamber n to raise the fluid pressure therein. The position of the parts shown in FIG. 5 is that assumed when the fluid pressure in chamber n has been raised to substantially equal the supply pressure maintained in manifold 12 and when the fluid pressure in downstream chamber n+1 has fallen to substantially equal the exhaust region pressure, in the present illustrative example the latter pressure being substantially that of the ambient atmosphere.

The valve means 14 shown in FIGS. 4 and 5 comprises a stationary valve body 56 and a movable valve body 58 positioned in body 56 for limited oscillatory movement about a central axis indicated at 60. The bodies 56 and 58 may be made of metal or of an appropriate molded plastic material. The bodies 56 and 58 each have a plurality of mating surfaces which constitute portions of cylinders formed about the axis 60 whereby the movable body 58 is freely movable about axis 60, the mating surfaces being reasonably accurately fitted and being sufficient in area to effectively isolate or seal off the several recesses, passageways and parts now to be described.

In FIG. 4 a supply tube 20 is fitted to nipple 26 opening into supply passageways 62 and 64 formed in stationary body 56. The passageway 64 is, in this position of parts, blocked off by the cylindrical surface of a portion 66 of the movable body 58.

An exhaust tube 22 is fitted to nipple 28 opening into passageways 68 and 70 formed in stationary body 56. The passageway 70 opens into an arcuate recess 72 defined by a radial wall 74 of stationary body 56 and a radial wall 76 of movable body 58, the recess 72 being isolated from inlet passageway 82 in this position of the parts.

The nipple 30 is inserted into an opening such as 34 (FIG. 2) in chamber n and communicates with a passageway 78 having two circumferentially spaced branch passageways 80 and 82 all formed in the stationary body 56. The branch passageways 80 and 82 are, in this position of the parts, blocked off respectively by the cylindrical surfaces of portions 84 and 86 of the movable body 58. A relatively small bleed passageway 88 opens off branch passageway 82 and communicates through passageways 90 and 92 with an arcuate recess 94 defined by a radial wall 96 of stationary body 56 and a radial wall 98 of movable body 58. The fluid pressure existing at any moment in chamber n is thus exerted through the passageways 78, 82, 88, 90 and 92 upon the radial wall 98 of movable body 58 within recess 94 and thus tends constantly to rotate movable body 58 counterclockwise with an effective force which varies with the fluid pressure existing in chamber n.

The nipple 32, in FIG. 4 is inserted into an opening such as 34 (FIG. 2) in the downstream chamber n+1 and places that chamber in communication with passageways 100, 102 and 104, all formed in the stationary body 56. The passageway 104 in the position shown in FIG. 4 is blocked off by the cylindrical surface of a portion 106 of movable body 58. A bleed passageway 108 opens off passageway 102 and communicates with an arcuate recess 110 defined by a radial wall 112 of stationary body 56 and a radial wall 114 of movable body 58. In the position of the parts shown in FIG. 4 the fluid pressure existing in chamber n+1 will be exerted through passageways 100 and 108 upon the wall 114 of movable body 58 and will tend to hold the movable body 58 against counterclockwise movement with an effective force which varies with the fluid pressure in said chamber n+1.

With regard to FIG. 4 it will be noted that the fluid pressure in chamber n is exerted on the wall 98 in recess 94 and that the area of wall 98 is quite small and that the wall 98 is relatively close to the central axis 60 of movable body 58. In contrast with this the fluid pressure in chamber n+1 is exerted upon the relatively large area of wall 114 in recess 110 and the wall 114 includes portions which are substantially further away from axis 60 than is the case with the wall 98. For both of these reasons a substantially greater fluid pressure is required to produce a given amount of torque by exertion upon wall 98 than is required to produce the same amount of torque by exertion upon the wall 114. As a practical example for use in the apparatus shown in FIG. 1 the compressor 10 may be designed to provide an adequate flow of air at about 20 p.s.i. (gauge) in manifold 12. When air at this pressure is supplied to chamber n it will inflate and the elastomeric material of which the chamber is made will be stretched until the fluid pressure in chamber n rises to substantially the supply pressure of 20 p.s.i. It is only when the fluid pressure in chamber n reaches substantially the supply pressure and when, also, the fluid pressure in chamber n+1 is at or drops to substantially that of the ambient atmosphere that the force exerted on wall 98 by chamber n is sufficient to overcome the resistance of the force exerted on wall 114 by the fluid pressure in chamber n+1. When this occurs the movable body 58 will start to move counterclockwise about axis 60 toward the position shown in FIG. 5.

As the movable valve body 58 moves from the FIG. 4 position to the FIG. 5 position the cylindrical surface of portion 86 of the movable body 58 will uncover the branch 82 of passageway 78 whereupon the pressurized fluid from chamber n will enter the now expanding recess 72 exerting force on wall 76 to add torque urging the movable body 58 counterclockwise and also flowing through the exhaust passageways 70 and 68 to the exhaust tuve 22. Thus the fluid pressure in chamber n will progressively reduce at a rate determined by several factors during the period of time required to move the body 58 from the FIG. 4 position to the FIG. 5 position. At first, with the pressurized fluid flowing only into recess 94 through the bleed passageways 88, 90 and 92, the rate will be very low but as the branch passageway 82 is progressively opened the pressure will drop progressively more rapidly due to the onset of flow to exhaust. An additional factor becomes involved in the form of the valve shown in FIGS. 4 and 5.

As shown in FIGS. 4 and 5 the movable valve body 58 has formed therein a passageway comprising two aligned portions 116 and 118 connected by a ball check valve 120 affording free flow of pressurized fluid from portion 116 to portion 118 but effective to block passage of pressurized fluid from portion 118 to 116. As the movable body 58 rocks counterclockwise towards the FIG. 5 position the passageway portion 116 opens into branch 80 of the passageway 78 communicating with chamber n. When this occurs the pressurized fluid from chamber n not only will flow to exhaust as described above but also will flow through passageway portion 116, past check valve 120, into passageway portion 118 and outwardly through passageways 104, 102, 100 and nipple 32 to chamber n+1. It will be understood for this to occur that the passageway portion 118 in movable body 58 has been brought into register with the passageway 104 in stationary body 56 as a result of counterclockwise movement of body 58 into the FIG. 5 position. Consequently so long as the diminishing fluid pressure from chamber n remains above the fluid pressure in passageway portion 118, pressurized fluid from chamber n will flow through movable valve body 58 to chamber n'1 with the parts in the FIG. 5 position.

In the FIG. 5 position a supply passageway 122, for chamber n+1, which is formed in movable body 58 has been brought into register with the supply passageways 64 and thus into communication with supply passageway 62, nipple 26 and supply tube 20. Pressurized fluid thus will flow through the passageway just mentioned into portion 118 and on to the chamber n+1. As chamber n+1 begins to inflate, against the resistance of the elastomeric material from which it is made, the fluid pressure therein and in passageway portion 118 will progressively rise and eventually will substantially equal the diminishing fluid pressure of chamber n whereupon the ball check valve 120 will close. At this juncture chamber n+1 will be connected directly with the supply tube 20 and will continue to inflate and chamber n will continue to exhaust through the passageways described above.

The movable body is held in the FIG. 5 position by contact with a stop 111 in recess 110. It will be noted that the recess 110 is sufficiently large in unoccupied volume in this position that the air trapped therein is not so compressed as to be effective to return the body 58 towards the FIG. 4 position.

A relatively small bleed passageway 124, 126, 128 is formed in movable body 58 and extends from passageway portion 118 to an arcuate recess 130 defined by a radial wall 132 formed on stationary valve body 56 and a radial wall 134 formed on the movable body. A similar bleed passageway 136 extends from passageway portion 116 and opens into an arcuate recess 138 defined by a radial wall 140 formed on stationary body 56 and a radial wall 142 formed on movable body 58. So long as ball check valve 120 remains open the fluid pressures directed by the bleed passageways, just described, to recesses 130 and 138 will be approximately equal. However, when check valve 120 closes and the fluid pressure in passageway portion 118, and thus in chamber n+1, rises relative to that in portion 116 a gradually increasing force is exerted on wall 134 of recess 130 whereby, after a delay deliberately designed into the small dimensions of the bleed passageways the torque developed in recess 130 will be sufficient to start movement of the movable body 58 in a clockwise direction thus beginning a portion of the cycle wherein the supply to chamber n+1 is to be cut off and the exhaust of chamber n is to be closed.

In the FIG. 5 position the passageway 108 is blocked by the cylindrical surface of the movable body 58. When clockwise movement of the body 58 is initiated by the intersection of the bleed passageways as just described the passageway 108 will remain blocked for a predetermined period of time since the initial clockwise movement of body 58 is relatively slow. As such movement continues, however, the wall 114 of recess 110 will open passageway 108 whereupon the now relatively high fluid pressure existing in chamber n+1 and the supply passageways leading to that chamber will be directed into recess 110 and will be effective by exerting force upon wall 114 to rapidly complete the return of movable body 58 to the FIG. 4 position, in which it comes to rest against a stop 73 in recess 72. The torque developed in recess 110 by the fluid pressure of chamber n+1 will be substantially greater than any torque now being developed in recesses 138, 94 and 72 by the fluid pressure existing in exhausted chamber n and in the exhaust manifold 24.

Upon the return of movable valve body 58 to the FIG. 4 position as just described chamber n is now ready to be inflated by the action of the valve means 14 lying between chamber n and chamber n-1. Also, since chamber n+1 is now fully inflated it will initiate action of the valve means 14 lying between chambers n+1 and n+2 to cause exhausting of chamber n+1 and inflation of chamber n+2.

In FIG. 1 the apparatus is shown with the first chamber n-2 of the series positioned near the extremity of the patient's leg whereby the pulsating wave-like action will be propagated upwardly of the leg. such disposition may be preferred by the physician in charge because of the peristaltic pumping action which is effective upon the veins in the same return direction as natural veinous flow. The apparatus of this embodiment is intended not only as a device for producing alternating compression and expansion of tissues in which secondary flow can be produced only by motion, muscular stressing and the like but also as a peristaltic pump.

In FIG. 1 there is shown only nine chambers n-2 et seq. encompassing the entire length of the lower leg. It will be understood that a greater number of chambers may be used. Also the chambers may be semi-circular in cross section instead of circular or squarish as shown in FIG. 1. A modification illustrating such semi-circular cross-sectional shape is shown in FIGS. 11 and 12 and will be described below.

In the embodiment shown in FIGS. 1 through 6 the valve means 14 each include the passageway 116, 118 and ball check valve 120 by means of which some of the pressurized fluid from the upstream chamber is directed into the downstream chamber. While this provision may result in some small saving in quantity of compressed air or other pressurized fluid a probably more significant advantage lies in the fact that exhaust occurs at a lower average pressure and volume.

In the modified form of valve means illustrated in FIGS. 7 and 8 no passageway is provided for flow of pressurized fluid from the upstream chamber through the valve means and into the downstream chamber. However, the valve means is responsive to the differential in fluid pressure between the upstream chamber and downstream chamber to control the supplying and exhausting functions and to produce the same timing results as achieved by the valve means 14 described above.

In FIGS. 7 and 8 a valve means 114 comprises a stationary valve body 146 and a movable valve body 148. The stationary body 146 for purposes of illustration may be identical in all respects with the stationary body 56 in FIGS. 4 and 5. The movable body 148 in FIGS. 7 and 8 is provided with a bleed passageway 150 leading to an arcuate recess 152 and a bleed passageway 154 leading to an arcuate recess 156. The movable valve body 148 also has a supply passageway 158 which corresponds exactly with the passageway 122 in FIGS. 4 and 5. In the position shown in FIG. 7 the bleed passageways 150 and 154 as well as the supply passageway 158 are all cut off by appropriate cylindrical surfaces of the stationary valve body as is the case in FIG. 4, described above. In this FIG. 7 position the fluid pressure from chamber n is exerted in recess 160 while the fluid pressure from chamber n+1 is exerted in chamber 162, all as in the case in the FIG. 4 illustration. When the fluid pressure in chamber n reaches substantially the supply pressure and when the pressure in chamber n+1 fails substantially to exhaust pressure the superior force now exerted in recess 160 will cause the movable body 148 to move counterclockwise toward and into the position shown in FIG. 8 as described above in connection with FIGS. 4 and 5.

In the FIG. 8 position the bleed passageways 150 and 154 are in communication respectively with chamber n and chamber n+1 whereby the differential in fluid pressures in these two chambers is sensed in the recesses 152 and 156. As is the case in FIGS. 4 and 5 when the fluid pressure in chamber n+1, which is being inflated, rises to approximately equal the pressure in chamber n, which is being exhausted, clockwise movement of movable body 148 commences and proceeds relatively gradually so that chamber n+1 may be fully inflated and chamber n may be fully exhausted before the movable body is rapidly moved to the FIG. 7 position by the fluid pressure of chamber n+1 exerted through bleed passageway 164 in the recess 162.

As has been noted above the use of the modified valve means 148 shown in FIGS. 7 and 8 in apparatus such as shown in FIG. 1 may be expected to require somewhat greater quantities of compressed air than is the case when the valve means 14 of FIGS. 4 and 5 is used.

There are specific aspects and advantages of the present invention which may be better understood by reference to the diagrammatic illustration in FIG. 9 in which the several valve elements and pressure-differential valve control elements which are combined in the valve means 14 of FIGS. 4 and 5 are illustrated in individual fashion. In FIG. 9 it will be observed that the chamber n-2 is supplied from manifold 12 through the flow-restricting means 38 at a constant rate. Assuming that the exhaust valve V4 of chamber n-2 has just been closed the fluid pressure in that chamber will rise at the rate predetermined by means 38 until it reaches substantially the supply pressure in manifold 12. At this time the pressure in chamber n-2 is exerted on the valve V1 which lies between chamber n-2 and chamber n-1. Valve V1 is assumed for this illustration to be a flap-type check valve biased into the closed position, as shown, so as to open only when the pressure from chamber n-2 is substantially at supply level and the pressure from chamber n-1 is substantially at exhaust level. The valve V1 is biased in the opposite direction to close only when the fluid pressure in chamber n-1 has risen substantially to equal the fluid pressure in chamber n-2. The flap of check valve V1 thus is the diagrammatic equivalent of the pressure responsive elements in valve means 14 shown in FIGS. 4 and 5.

As indicated by conventional broken lines in FIG. 9 the valve VI of chamber n-2 is ganged with exhause valve V4 of chamber n-2 and with the supply valve V2 of chamber n-1. Thus V1 is forced open when chamber n-2 is ready to exhaust and chamber n-1 is ready for inflation and the ganging may be such that the movement of V1 to open position simultaneously causes opening of V4 in chamber n-2 and V2 in chamber n-1. From this point pressure falls in n-2 and rises in n-1 and when the differential in those pressures reaches approximately zero the valve V1 is forced back to closed condition. The ganging of the valves V4, V1 and V2 must be such as to introduce a delay in the closing of valves V4 and V2 in response to the closing of valve V1 in order to permit continued exhausting of chamber n-2 and continued inflation of chamber n-1 thus to afford a diagrammatic equivalent of the action of valve 14 as described above.

It will be recognized that the chamber n-2 represents a special case inasmuch as there is no valve element for closing the supply to this chamber. The continuous supply provided by the flow restrictor device 38 is restricted so as to be well below the rate at which the pressurized fluid will flow to exhaust when the exhaust valve is open. The pressure in n-2 will drop sufficiently, when the exhaust is open, for reversal of valve V1 at the proper time. This simple arrangement permits the use of identical valve means, such as the means 14 shown in FIGS. 4 and 5, between all chambers in any series. As will be apparent, a supply valve could be provided for chamber n-2 which needs only to be ganged with the exhaust valve V4 in this chamber to open when the exhaust closes and vice versa, such provision, however, is regarded as pointless in view of the advantages of the flow restrictor 38 as described above.

The last chamber n+6 shown in FIG. 9 is another special case, being a sort of mirror image of the chamber n-2. Thus, chamber n+6 does not require an exhaust valve, although one could be ganged with the supply valve V2 for that chamber. Preferably, to avoid the need for a special valve, the flow restrictor device 50 is substituted for the exhaust valve whereby the fluid pressure developed in chamber n30 6 when supply valve V2 is opened may never reach full supply pressure but nevertheless will drop when the supply valve is cut off. The time delay induced by the restrictor 50 may be approximated as to permit the pressure to fall to exhaust level at about the time the pressure in the preceding chamber in the series reaches supply level. All of the chambers lying between chamber n-2 and chamber n+6 will operate in the normal manner described above in steady state operation.

The self-starting feature will now be described in connection with FIG. 9. The flap-type valves V1 in FIG. 9 for illustrative reasons have been assumed to be biased by springs or weights into the closed positions shown in FIG. 9 and the ganging is such that all of the supply valves V2 and all of the exhaust valves V4 would also be biased toward closed position and they would automatically assume such positions when no pressurized fluid is being supplied through manifold 12. Self-starting of such an arrangement is obvious since when the compressor 10 is started, air will flow only into chamber n-2 through flow restrictor 38 and when the pressure therein rises to substantially supply level, the valve V1 will open into chamber n-1 since the latter, like all of the succeeding chambers, is at atmospheric pressure. Opening of this valve V1 will open supply valve V2 for chamber n-1 and will open exhaust valve V4 for chamber n-2. Chamber n-1 is now inflated while chamber n-2 exhausts and as a result of inflation of chamber n-1, the operation of chamber n and all succeeding chambers will be progressively initiated.

However, the preferred valve means of FIGS. 4 and 5 and FIGS. 7 and 8 preferably are not biased by weights or springs and when a device is first assembled or after any period of non-use of an assembled device, the movable interior bodies 58 or 148 thereof may be in completely random positions. By pure chance they might all be in the positions shown in FIG. 4 or FIG. 7 thus corresponding with the all valves closed positions discussed in connection with FIG. 9 and the device would start substantially as described above. Also, by pure chance, they might all be in the position shown in FIG. 5 or FIG. 8 where the valve elements corresponding with the valves V1, V2 and V4 of FIG. 9 would all be open. In that event, air supplied to manifold 12 would flow freely through and out the exhaust of all chambers from n+2 up to but excluding chamber n+6. Because of the restricted exhaust afforded by restrictor 50 in chamber n30 6, the pressure therein will rise above that in the preceding chamber n+5 (not shown in FIG. 9) to close connecting valve V1 and supply valve V2 for chamber n+6 as well as to close exhaust valve V4 of chamber n+5. Pressure now will rise in chamber n+5 to close the exhaust of n+4 and this will continue all the way back to chamber n+2 possibly without any of the chambers having come up to full supply pressure. However, chamber n+2 must now come up to supply pressure before it will open the valve V1 leading to chamber n+1 and from there on all succeeding chambers will go into normal steady state operation.

In any random arrangement of the valve means other than the two extreme cases just assumed, there must be at least one valve means in a position different from that of the valve means upstream or downstream thereof and cyclical operation will start in the chamber between these valve means and this cyclical behavior will propagated throughout the series. After a few cycles of perhaps erratic behavior all of the chambers will arranged themselves into the design pattern of operation. In the preferred valve means 14 or 144, many or all of movable bodies 58 or 148 may be in a stable position such as FIG. 4 or FIG. 5 but instead may be in some intermediate position. However, when pressurized fluid is supplied to the manifold 12, the movable bodies will be forced into one or the other of the stable positions as soon as a substantial differential in pressure is sensed between the connected chambers, and this is almost inevitable inasmuch as, absent an almost incredible coincidence, some of the chambers will be wholly or partly in communication with supply pressure while others will not. If the resultant movement of the various valve means into stable positions does not initiate cyclic action between at least one pair of chambers interior of the series, cyclic action nevertheless will be initiated at one end or the other of the series because of the constant restricted supply to chamber n-2 and the constant restricted exhaust from chamber n+6 when the flow restrictors 38 and 50 are used as illustrated in FIGS. 1 and 9. Alternatively, as stated above, a special supply valve (not shown) may be provided for chamber n-2, ganged to open when the exhaust valve V4 for chamber n-2 is closed and a special exhaust valve (not shown) may be provided for chamber n+6 ganged to close when supply valve V2 for that chamber is open. This alternative structure will operate to assure self-starting at least from one end or the other of the series just as does the structure wherein the flow restrictors 38 and 50 are used.

If, as a result of the almost incredible coincidence mentioned above, all of the valve bodies 58 of FIGS. 4 and 5 or 148 of FIGS. 7 and 8 were in identical intermediate positions such that the rate of supply and exhaust to all intermediate chambers happened to be exactly equal, no differential in pressure would be established between any of the interior chambers and all of the valve bodies might remain in the original intermediate position. However, this condition would be the same as if all exhausts were wide open and the restricted exhaust of chamber n-2 would be effective to starting cycling from the downstream end as explained above. Such coincidence is made all the more incredible when it is recalled that the preferred forms of valve means 14 or 144 and the chambers themselves are to be mass produced and could not be expected to be sufficiently identical for this coincidence to arise.

The feature of self-starting without any need for pre-arrangement of the valve means, or any of them is a particularly important advantage of the present invention. Among other things it makes practical the modular system illustrated in FIG. 1.

In steady state operation the chamber n, of course, will start inflating each time the two control factors are satisfied, that is when chamber n reaches exhaust level at a time that chamber n-1 is at supply level or when chamber n-1 reaches supply level at a time that chamber n is at exhaust level. Obviously, also chamber n may reach exhaust level at the same instant that chamber n-1 reaches supply level and inflation of chamber n will start at that same time. However, it is a specific feature of this invention that such precision of timing is not required whereby the valve means employed need not be clostly precision-matched devices. also, the chambers need not all be of the same size or volume, as indeed they are not in the embodiment shown in FIG. 1. If a relatively small chamber precedes a larger one in the series the smaller chamber ordinarily will reach supply pressure before the larger downstream chamber has exhausted to exhaust level. The valve VI between such chambers will wait until the larger chamber has exhausted to proper level. If a larger chamber precedes a smaller chamber in such a series, the valve VI between these chambers will wait for the larger chamber to reach supply level. It will be appreciated that the differences in volume here contemplated must lie within a reasonable range of variations such as is illustratively shown in FIG. 1. Otherwise it may be preferable to provide valve means with appropriately altered flow rates or time delays to couple chambers of substantially different volume. Furthermore, the modular chambers of FIG. 1 may be with smaller cross-sections for larger diameters whereby to have volumes more nearly equal throughout the series.

The frequency at which pressure waves are propagated lengthwise of a series of chambers in accordance with the present invention is determined by the rates at which the pressurized fluid flows into and out of the chambers and upon the inflation characteristics of the chambers themselves. The rates of flow, of course, are established by the sizes of the tubes and valve passageways through which the fluid at any given supply pressure will flow against any given back pressure offered by the chambers. While the chambers might be rigid in some presently unknown embodiment and the valve means provided herein would operate perfectly with such chambers, no presently discernable purpose would be served by such a combination. The preferred chambers will expand and contract and any such chambers will exhibit a yielding and extended resistance to expansion and will contribute a yielding and extended force to exhaustion. This is a major factor in design of the embodiment of the invention shown in FIG. 1 as it is in the design of a peristaltic pumping device such as will be described hereinbelow.

The ganging pattern of FIG. 9 may be turned through 90.degree. thus to gang each valve V1 with the supply valve V2 of the upstream chamber and the exhaust valve V4 of the downstream chamber. While this would no longer be a diagrammatic equivalent of the valve means 14 the operation would be the full equivalent of that achieved by the means 14 and the illustrated arrangement in FIG. 9.

In FIG. 10 there is shown a modification in the ganging of the valve elements which also does not constitute a diagrammatic equivalent of the valve means 14 shown in FIGS. 4 and 5. In FIG. 10 the valve V1 leading into each of the downstream chambers is ganged with the supply valve V2 and the exhaust valve 74 for that particular chamber. Considering first chamber n, the valve V1 leading thereto from chamber n-1 will open only when the fluid pressure in n-1 reaches substantially supply pressure and the fluid pressure in chamber n reaches substantially exhaust level. When V1 opens it is ganged to close exhaust valve V4 of chamber n and to open supply valve V2 of that chamber. As the fluid pressure rises in chamber n to substantially equal the falling pressure in chamber n-1 the valve V1 will be moved back to closed position. A time delay device is built into the ganging arrangement whereby exhaust valve V4 and supply valve V2 in chamber n remain closed and open respectively for a period sufficient to permit fluid pressure in chamber n to rise substantially to supply level. When this occurs the valve V1 downstream of chamber n will open and the inflation of chamber n+1 starts. It must be pointed out that the modification shown in FIG. 10 will require valve elements quite closely matched and of greater precision than is the case with the preceding embodiments and that there is much less tolerance for variations in volumes of the chambers in a series. This is because the exhaust valve V4 of each chamber will open at a fixed time after the upstream valve V1 opens and thus the chamber n, for example will not wait at full pressure for the downstream chamber n+1 to exhaust. The ganging in FIG. 10 may be altered to gang the downstream valve V1 of each chamber with the inlet and exhaust valves V2 and V4 of that same chamber with results much the same as achieved by the illustrated ganging.

In the modification shown in FIG. 10 the first chamber n-2 has no exhaust and it is supplied through a flow restricting device 38 as is the case in the preceding forms of this invention. Thus, in chamber n-2 the pressure may rise to supply level in a predetermined period of time roughly or substantially matched with the inflation time for the succeeding chambers. However, the pressure in chamber n-2 will not drop to exhaust level but rather will drop only as a result of flow of pressurized fluid from chamber n-2 into chamber n-1 during the period that the valve V1 between these chambers remains open.

The last chamber n+6 in FIG. 10 may be provided with the same exhaust valve element V4 as is provided in those preceding chambers interior of the series and chamber n+6 will operate in the same manner as those preceding chambers.

The valve means provided in FIG. 10 may be constructed in any suitable fashion and, if so desired, may be made into modular units insertable between chambers in series of any desired length in a manner similar to that disclosed in FIGS. 4 and 5. No modular counterpart of FIG. 10 is shown herein since it does not appear that such showing need be made for a complete understanding of the present invention.

The embodiments shown in FIGS. 4 and 5, 7 and 8 and described in connection with FIG. 9 are definitely preferable to those described in FIG. 10 because the valve means of the earlier embodiments are completely controlled by the differential in pressure between adjacent chambers. In FIG. 10 the inflation of a chamber is initiated in response to such differential but the initiation of exhaust is a function of time rather than of the differential.

The modular therapeutic apparatus shown in FIG. 1 may be modified in many ways by those skilled in the art. For example instead of the complete toroidal chambers n-2 et seq. shown in FIG. 1 the chambers may be made adjustable in effective diameter as shown in FIG. 11. In that Figure a single chamber 170 is shown comprising a tube of semi-circular form having closed ends 172. Adjustable fastening elements 174, 176, such as a flexible hook and loop fastener sold under the registered trademark "Velcro" may be secured to the closed-end regions of the tube so that it may be secured upon human body portions of varying sizes. Such chambers 170 may have inlet and outlet openings 178, 180 in any convenient location for cooperation with modular valve means such as the means 14 or 144 shown in FIGS. 1 through 8.

FIG. 12 is a cross sectional view of a preferred construction for the chamber 170 of FIG. 11. The semi-circular portion 182 thereof may be made of a relatively non-stretchable material such as a woven fabric impregnated or coated with a fluid tight elastomeric material such as rubber or synthetic rubber-like material. The wall 184 which defines the inner diameter of the chamber 170 may be made of a stretchable flexible elastomeric material such as sheet rubber or synthetic rubber-like material. When the chamber 170 is inflated, as by compressed air, the wall 184 will stretch and exert radially inward pressure upon the tissues of the patient on which it is being used. Obviously, this same semi-circular cross section may be adapted to the nonadjustable form of chambers shown in FIG. 1.

The present invention also may be embodied in non-modular form for example a form such as that shown in FIG. 13. In this figure the series of chambers is built into a legging-like structure which may be sized to fit the upper or lower arms a or legs or persons requiring therapy of the type afforded by the present invention. In FIG. 13 outer legging 186 may be made of relatively non-stretchable fabric, plastic sheet or the like provided with a conventional slide fastener comprising two toothed parts 188, 190 and a slide 192. The interior wall of legging 186 is made up of a series of chambers comprising closed end tubes 194 of stretchable material such as rubber or rubber-like plastic material each secured to the legging, for example as shown in the sectional view in FIG. 14. The chambers 194 thus may be made from a single sheet of stretchable material, heat-sealed or otherwise adhesively secured along line 196 to provide the separate chambers 195. valve means 198 may be fixed to the exterior of the legging 186, communicating through legging 186 with each chamber 194 and the valve means each may be connected with a supply manifold 200 and exhaust manifold 202, all as shown in FIG. 13. As will be apparent the valve means 198 may be similar to or identical with the valve means 14 or 144 shown in FIGS. 1 through 8.

The present invention may be readily adapted to use as a peristaltic pump of substantially any of the well known configurations of such devices. A single adaptation is shown diagrammatically in FIG. 15. In this figure an outer rigid tube or conduit 210 has positioned therein a series of inflatable toroidal chambers 212 which surround a flexible tube 214 in which the material to be pumped is confined. Outside the rigid tube there is provided a series of valve means 216 of any of the types hereinabove described, one valve means 216 being connected between adjacent toroidal chambers 212 within the series. Each of the several valve means 216 is connected with a supply manifold 218 and an exhaust manifold 220. The operation of the toroidal chambers in expanding and contracting in a plurality of successively propagated waves is the same here as has been described above and the peristaltic squeezing action upon the flexible tube 214 will be effective to advance material along the tube as is well known. The materials thus advanced usually are of pasty, semi liquid form, such as concrete, or flowable dry materials such as small spheres of plastic material being advanced to an extruder or molding device or the like. Also, such devices are frequently used for pumping highly corrosive or abrasive liquids or suspensions or slurries or the like which present problems in pumping by more conventional apparatus.

In FIG. 15, the valve means 216 and manifolds 218, 220 are shown outside the rigid tube 210 merely for illustrative purposes. It will be apparent that these elements may be arranged within the rigid tube 210 by notching the toroidal chambers 212 as suggested above in FIGS. 1 and 2 or by providing a separate rigid conduit within the portions of the tube 210 which are occupied by the chambers 212.

The adaptibility of the present invention to other forms of peristaltic pump arrangements will be apparent. Thus the chambers each may comprise a spherical body adapted to expand to close the pipe or conduit within which the pumpable material is flowing and to contract to open the same upon inflation and deflation, respectively. The self starting and self regulating action provided by the present invention may be relied upon in such adaptations to reliably produce the pulsating and wave propagating action required for such pumping.

Mention has been made above to the fact that adjustable throttle valves could be used instead of the flow restrictors 38 and 50 in FIGS. 1, 9 and 10. Flow restrictors of fixed characteristics are preferred because except for an initial adjustment to approximately match the operational characteristics of the chambers n-2 et seq. there would be no further need for adjustment if adjustable throttle valves were to be provided. Indeed, unskilled or unauthorized persons could cause some difficulty in operation of the first and last chambers, at least by tampering with the adjustable valves. Accordingly the fixed flow rates of the flow restrictors 38 and 50 preferably are established by original design so as to operate as described above.

It should be noted that the valve means 14 are self starting irrespective of random modes in which they may fall when the devices such as that shown in FIG. 1 is first assembled or even when the device is restarted after a period of rest. The manner in which this is accomplished has been described in connection with the diagrammatic showing in FIG. 9 and it is referred to at this point only to emphasize that the valve means 14 operate in the manner thus described. This feature as well as the use of flow restrictors 38 and 50 instead of special or adjustable valves for the first and last chambers contribute substantially to the practicality of the preferred modular construction. When a device is to be assembled for a particular patient a selection of modular chambers n-2 et seq. is made and the assembly operation thereafter may be made by unskilled persons since there is nothing to adjust and the chambers are plugged together by identical valve means which do not require setting into any specific mode. These features are of almost equal value in connection with a non-modular embodiment such as shown in FIG. 13 and in a peristaltic pumping device of any type inasmuch as the initial assembly is simplified and no resetting is required after packing and shipping or after intermittent periods of use and non-use.

In those embodiments of this invention which are intended for therapeutic use the fact that a mechanically driven distributor is not required is of substantial importance. the total bulk of the device is reduced because it is not necessary to have an individual conduit or tube running from the distributor to each of the inflatable chambers. Since only a single supply line is required from the compressor to the device applied to a patient the compressor may be located outside the patient's room or the pressurized air or other fluid may be drawn from a central plant. In either event no electrical equipment need be near the patient. Therefore, the present device may be used in operating rooms to prevent stasis in the deep veins of the limbs of patients on which operation is being performed. In contrast, the electric motors used in the mechanically driven distributors of the prior art would be dangerous and probably not acceptable in an operating room and the multitudinous tubes required would make impractical the locating of the distributor outside the operating room.

In those embodiments of this invention intended for therapeutic use it is suggested, without limiting such use to that suggestion, that the apparatus be so designed as to provide a complete cycle of inflation and deflation of each of the chambers, such as n-2 et seq. as shown in FIG. 1, every two seconds. The frequency or rate of propagation of waves of pressure along the series will thus be about one-half chamber per second, a frequency which will result in a pleasant stroking sensation insofar as the patient is concerned. As noted above, the time required for inflation and deflation of any chamber of the series is a function of many variables including supply pressure, size of manifolds and tabing, size of passageways within and into and out of the valve means and chambers, the relative areas and spacing radially, from the axis of a valve such as shown in FIGS. 5 and 7 and 8, of the valve control surfaces against which fluid pressures are exerted, as well as the volume and stretch characteristics of the chambers and the materials from which the chambers are made. Any desired combination of these and other variables may be established by those skilled in the art.

Claims

What is claimed is:

1. In combination, supply means for supply fluid pressurized to a predetermined pressure, supply manifold means connected with said supply means, a plurality of inflatable chambers made of elastomeric material expansible and contractable under changing fluid pressure, said chambers being arranged in a series comprising a first chamber, a plurality of intermediate chambers extending in series downstream of said first chamber and a last chamber downstream of said intermediate chambers, means for producing a continuous series of pressure pulses sequentially along said series of chambers comprising: means providing a supply passageway for connecting each of said chambers individually with said supply manifold means, bistable open and closed supply valve means associated with each of said supply passageways except that for said first chamber to afford flow at a predetermined rate or no flow of said fluid from said manifold through said supply passageway to the interior of the chamber with which said supply passageway is connected, means providing an exhaust passageway connecting the interior of each of said chambers with an exhaust region at fluid pressure lower than said predetermined pressure, bistable open and closed exhaust valve means associated with each of said exhaust passageways except that for said last chamber to afford flow at a predetermined rate or no flow of said fluid from the chamber with which said exhaust passageway is connected to said region, a plurality of fluid pressure responsive valve control means each connected between each chamber and the chamber immediately downstream thereof in said series by means of passageways communicating respectively with the interior of the upstream and downstream chambers thus connected, each of said valve control means being movable in opposite directions into either of two stable positions in response to the differential in fluid pressure between the two chambers which each of said valve control means connect, each of said valve control means being thus movable in one direction to one stable position by movement initiated only when the fluid pressure in the connected upstream chamber is substantially equal to said predetermined pressure and the fluid pressure in the connected downstream chamber is substantially equal to that in said exhaust region, means responsive to the movement of each of said valve control means in said one direction for opening the exhaust valve means for the connected upstream chamber and for opening the supply valve means for the connected downstream chamber to progressively lower the pressure in the connected upstream chamber and to progressively raise the fluid pressure in said downstream chamber substantially to said predetermined pressure, and each of said valve control means being thus movable in another direction to another stable position by movement initiated only when the progressively rising fluid pressure in said connected downstream chamber rises to substantially equal the progressively lowering fluid pressure in said connected upstream chamber, means responsive to the movement of each of said valve control means in said another direction for initiating the closing of the supply valve means for said connected downstream chamber and for initiating the closing of the exhaust valve means for said connected upstream chamber, each of said valve control means including means for delaying completion of the initiated closing of said supply valve means for said connected downstream chamber and of said exhaust valve means for said connected upstream chamber for a predetermined period of time sufficient to insure that the pressure in said connected downstream chamber rises substantially to equal said predetermined supply pressure and to insure that the pressure in said connected upstream chamber lowers substantially to equal the pressure in said exhaust region, said valve control means when in said another stable position holding closed the exhaust valve means for said connected upstream chamber and also holding closed the supply valve means for said connected downstream chamber whereby to place the next cycle of inflation of said connected upstream chamber under control of the chamber immediately upstream thereof and to place the next cycle of exhaust of said connected downstream chamber under control of the chamber immediately downstream thereof.

2. A combination in accordance with claim 1 in which said means for delaying the closing of said exhaust and supply valve means comprises bleed passageways affording flow at a restricted volumetric rate of pressurized fluid from said connected upstream and said connected downstream chambers to move said valve control means slowly towards said another position.

3. A combination in accordance with claim 2 in which each of said valve control means also comprises a connecting passageway which provides direct communication from said upstream connected chamber to said downstream connected chamber when said valve control means is in said one stable position and a check valve in said connecting passageway to permit flow of pressurized fluid therethrough only in a downstream direction.

4. A combination in accordance with claim 2 in which said valve control means includes a port which is opened when said slowly moving valve control means closely approaches said another position for directing pressurized fluid under rising pressure from said connected downstream chamber to a pressure responsive element in said valve control means to rapidly complete movement of said valve control means into said another stable position and to hold said valve means in said stable position until movement of said valve control means in said one direction is again initiated.