This invention relates fluid-flow control apparatus of the kind for controlling flow along at least two flow paths.

There are many applications where it is necessary to control the flow of gases or liquids. In some of these applications, it is desirable to control the flow of several different fluids simultaneously. One example of such an application is in patient resuscitators such as of the kind described in PCT/GB05/003304, PCT/GB04/003758 and PCT/GB04/003788. In this resuscitator a single restrictor device is operable to control the flow along three different gas paths.

It is an object of the present invention to provide an alternative form of restrictor or fluid flow control apparatus that can restrict or control multiple flows in an interdependent manner.

According to the present invention there is provided fluid-flow control apparatus of the above-specified kind, characterised in that the apparatus includes a base having a first surface formed with at least two channels opening along the surface, first and second fluid openings on the base communicating with respective ones of the channels, a second member having a second surface mounted facing and adjacent the first surface, and third and fourth fluid openings opening on the second surface and arranged to be in fluid communication with the first and second openings via respective channels, that the first and second fluid openings and the third and fourth fluid openings are in communication with respective flow paths, and that the second member is movable relative to the base such as to alter the distance along respective channels between the first and third openings and between the second and fourth openings, such as thereby simultaneously to alter the fluid flow along the two flow paths.

The base and second member are preferably movable relative to one another by relative rotation about an axis. The two channels may be at the same radial distance from the rotational axis. The apparatus preferably includes a resilient O-ring arranged to reduce leakage from a channel. The O-ring may be located in grooves in both the first and second

surfaces. The O-ring and grooves may be shaped such that the ring is compressed between opposite edges of the grooves. The apparatus preferably includes two O-rings arranged concentrically of one another, the channel extending concentrically between the O-rings. The cross-sectional area of at least one of the channels may be different at different locations along its length. The base may include a plastics support and a metal plate mounted on the support, the metal plate providing the first surface. The apparatus preferably includes a clamp operable to hold the base and second member with one another, the clamp being arranged to apply the majority of clamping pressure to the region of the channels.

Rotary gas flow restrictor apparatus for use in a patient resuscitator, in accordance with the present invention, will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a simplified, schematic side elevation view of the restrictor;

Figure 2 is a plan view of the restrictor disc;

Figure 3 is a cross-sectional side elevation view of a part of the restrictor apparatus showing the O-rings between facing surfaces.

Figure 4 is view of the underside of the selector disc;

Figure 5 is a cross-sectional side elevation of the selector disc;

Figures 6 A to 6D illustrate different configurations of the restrictor plate; and

Figure 7 is a perspective view of a modified form of the apparatus.

With reference first to Figure 1, the apparatus includes a gas inlet 1 and three gas outlets 4 to 6. The inlet 1 opens into a base or manifold assembly 10 and communicates with two flow paths 1 ' and 2'. Two of the outlets 4 and 5 open from a second member or selector disc 11 and the other outlet 6 opens from the manifold assembly 10. The selector disc 11 is

rotatable through a limited angle relative to the manifold 10 to alter the flow to all three outlets 4, 5 and 6 simultaneously in a defined manner.

The manifold assembly 10 is formed of two main parts, namely a lower support plate 12 and an upper restrictor disc 14. The plate 12 is of cylindrical shape and circular section made of acetal plastics. The plate 12 has two gas ports providing the gas inlet 1 and the outlet 6; these communicate with bores 1 ', 2' and 6' extending through the thickness of the plate. The ports 1 and 6 are shown as being located on the lower surface of the plate 12 but could be at any other location, such as on the side, more convenient for mounting the apparatus. The bores 1 ', 2' and 6' open on the upper surface 13 of the plate 12 through three respective holes (not shown).

The other main component of the manifold assembly 10, namely the restrictor disc 14 (shown most clearly in Figure 2) is of metal and is of circular shape having the same diameter as the support plate 12. The disc 14 sits flat on the upper surface 13 of the plate 12. To ensure correct seating of the disc 14 on the plate 12, the upper surface 13 of the plate is formed with three small, shallow circular recesses 15 (only one of which is shown in Figure 1) each containing a resilient O-ring 16. The dimensions of the O-ring 16 are such that it projects slightly above the upper surface 13, when uncompressed, but is flattened level with the upper surface by the lower surface of the disc 14. The three O-rings 16 are located at the same radial distance and are equally spaced from one another around the plate. The O-rings 16 each serve a dual purpose, that is, both to foπn a gas seal and to act as a cushion to support the disc 14 when it is assembled on the plate 12 and thereby ensure that it remains parallel to the surface 13 of the plate when it is compressed into position. Additional O-rings (not shown) may be included for mounting purposes only.

The upper surface 18 of the disc 14 is shown in Figures 2 and 3 and is cut with a number of channels and holes as will now be explained in detail, from the centre outwardly. Figure 3 is schematic, is not to scale and does not show the true relative positions of the different channels. A relatively large circular hole 19 opens through the centre of the disc 14, the diameter of the hole being about one third the diameter of the disc. The circumference of the hole 19 is interrupted by a small semicircular notch 20 adapted to receive a locating pin

(not shown) mounted with and projecting upwardly from the support plate 12. The pin locates in the notch 20 to ensure correct angular alignment of the disc 14 relative to the plate 12 and to prevent relative angular movement between the disc and the plate. The pin projects upwardly through the restrictor disc 14 and into the selector disc 11 for a purpose that will be explained later.

A circular groove 22 extends concentrically around the central hole 19, forming a complete circle around the disc 14. In section, as shown in Figure 3, the groove 22 has an oval or elliptical shape such that its width is less than its depth. The groove 22 retains an inner, compliant O-ring 23. The O-ring 23 is circular and has a natural circular section with a diameter slightly less than the width of the groove 22 at the upper surface 18 so that the O- ring is squeezed laterally slightly in the groove into sealing engagement with the inner and outer edges 24 and 25 of the groove. From Figure 3 it can be seen that the upper surface 18 of the restrictor disc 14 steps upwardly slightly on the radially outer side of the groove 22 to provide a first annular sealing land 26 between the inner O-ring 23 and a radially outer, second O-ring 27, which extends concentrically of the inner O-ring. The inner region 18' provides a reduced height annular ledge around the central hole 19 and a gap with the selector disc 11. A first flow-control channel 30 is located midway across the first sealing land 26 and extends concentrically of and between the two O-rings 23 and 27 a part way around the land, by about 90°. In section, the channel 30 has inwardly sloping sides 31 and 32 and a flat floor 33. This channel 30 is used to control flow of gas to the timing valve of a patient resuscitator, the rate of operation of the valve being determined by the rate of flow of gas through the channel. The inlet end 34 of the channel 30 is located in the 8 o'clock position in Figure 2, the channel extending clockwise to approximately an 11 o'clock position. The inlet end 34 has a slightly enlarged circular entry point provided by a hole 35 through the thickness of the disc 14, which aligns with one of the three holes in the upper surface 13 of the support plate 12 so that gas flows from one of the ports 1 and 2 into the channel 30. The hole in the support plate 12 that supplies gas to the channel 30 preferably has a filter to prevent any debris entering the channel. The inlet end 34 of the channel 30 extends from the hole 35 and is relatively narrow, giving the channel a relatively small cross-section. The width of the channel 30 tapers to a slightly increased diameter along the first part of its length and then continues to its far end 36 at a relatively constant width and cross-section.

The second O-ring 27 is located in a second, outer groove 38, which has the same shape as the inner groove 22. Extending externally around the outer groove 38 is a second, outer sealing land 40, which is cut with two flow control channels 41 and 42 located at the same radial distance but spaced from one another around the land 40. The channel 41 has an inlet end 43 located at approximately 7 o'clock and extends anticlockwise (that is, in the opposite sense to the timing control channel 30) to its closed end 44 at approximately 5 o'clock. The inlet end 43 communicates with a hole 46 extending through the thickness of the disc 14, which aligns with a corresponding hole in the upper surface 13 of the support plate 12. The channel 41 is wider and deeper than the channel 30 and tapers slightly in width along its length from its inlet end 43 to a smaller cross section at its closed end 44. This channel 41 is used to control the flow rate of oxygen to the patient in a patient resuscitator.

The third channel 42 extends in the same direction as the oxygen control channel 41, that is, in an anticlockwise direction from an outlet end 48 at substantially 4 o'clock to a closed end 49 at substantially 1 o'clock. The outlet end 48 opens from a hole 50 through the thickness of the disc 14, which aligns with the third hole in the upper surface 13 of the support plate 12. The cross-section of the third channel 42 is less than that of the second channel 41 but greater than that of the first channel and tapers slightly in width along its length. The three channels 30, 41 and 42 are all of the same length, extending around about 90°.

The second, outer sealing land 40 also includes a shallow, circular recess 52 formed in the upper surface 18 of the disc 14 at approximately the 10 o'clock position. The recess 52 receives a detent mounted with the selector plate 11, in a manner that will be described later, when the selector plate and restrictor disc 14 are in a defined angular orientation with respect to one another.

The upper surface 18 of the restrictor disc 14 is stepped down slightly radially outwardly of the outer sealing land 40 to provide an annular, peripheral ledge 54. By cutting away the inner region 18' and outer region 54, the two sealing lands 26 and 40 are raised above these regions so that, when a clamping force is applied between the restrictor disc 14

and the selector plate 11, the force is applied primarily in the region of the channels 30, 41 and 42.

The selector plate 11 will now be described, by way of example, with reference to Figures 4 and 5 of the drawings. The selector plate 11 is moulded from an acetal plastics and is cut and drilled with various formations. The plate 11 has a central hole 60 extending through its thickness, with an enlarged upper end 61 providing a recess for a spring 103 of a clamping bolt 7 (Figure 1), which extends through the selector plate 11, the restrictor plate 14 and the support plate 12 to clamp the components securely with one another. The lower surface 62 of the plate 11 has a circular, annular region 63 surrounding the hole 60, which is recessed slightly. A curved, crescent-shape slot 64 is formed towards an outer edge of this region 63 and extending around the region by about 90°. The locating pin that projects from the support plate 12 through the notch 20 in the restrictor plate 14, projects within the slot 64 and thereby limits the extent of angular rotation of the selector plate 11 relative to the base or manifold assembly 10. The recessed region 63 steps to an external annular region 65, which, in use, abuts against the upper surface 18 of the restrictor plate 14. A first, inner annular groove 66 extends concentrically of the hole 60, the groove having the same diameter and shape as the inner groove 22 in the restrictor plate 14 so that the upper half of the O-ring 23 is received in this groove. An inner, annular sealing land 67 is formed externally of the inner groove 66, between the groove and an outer groove 68. The inner sealing land 67 is uninterrupted except for a small hole 69 through the surface, which communicates with a gas passage 70 extending outwardly at an angle to the lower surface of the selector plate 11 and providing, at the edge of the plate, the gas outlet 4 to the timing valve. The hole 69 is positioned so that it aligns above the timing channel 30.

The outer groove 68 extends concentrically, externally of the inner groove 66 and aligns with the outer groove 38 in the restrictor plate 14 to receive the upper half of the outer O-ring 27. The annular region surrounding the outer groove 68 provides an outer sealing land 71, which overlies the sealing land 40 on the restrictor plate 14. The outer sealing land 71 is interrupted by two holes 72 and 73 located to align with the channels 41 and 42 respectively. The two holes 72 and 73 are connected with one another by a drilled bore 74 extending between them through the plate 11 parallel to its lower surface 62. One end of the bore 74

projects beyond the hole 73 to the edge of the plate 11, where it is blocked. The opposite end of the bore 74 communicates with a second bore 75 extending above and at an angle to the first bore to the edge of the plate 11 where it opens to provide the pure oxygen outlet 5. The outlet 5 is connected to a patient outlet 80 via a valve 81 (Figure 1). When the valve 81 is open the oxygen takes the easiest route to the patient outlet 80; when the valve is closed, the oxygen flows instead out of the hole 72 to communicate with the channel 42. The hole 50 at the outlet end 48 of the channel 42 connects through the support plate 12 with the outlet 6, which connects to an air entrainment mixer in the patient resuscitator where oxygen is mixed with ambient air.

The sealing land 71 further includes a short vertical bore 82 in which is retained a spring-loaded ball (not shown) arranged to engage in the recess 52 in the restrictor disc 14. This acts as a detent to retain the selector plate 11 in an angular position about midway along its range of movement equivalent to a timing rate of about 12 breaths/minute. The lower surface of the selector plate 11 is cut away slightly around its edge to form a raised ledge 83.

The selector plate 11, manifold plate 12 and restrictor plate 14 are clamped securely together to an appropriate torque by means of the clamping bolt 7 extending through the central holes 60 and 19 through the components and through an upper clamping plate 90. The torque is selected to minimize leakage whilst enabling relative frictional rotational between the selector plate 11 and the restrictor plate 14. The underside of the clamping plate 90 is cut away in its central region 91 so that it engages the selector plate 11 around an edge region 92 positioned above the channels 30, 41 and 42. In this way, the maximum part of the clamping force is applied in the region of the three channels 30, 41 and 42. Also, the central region 63 and outer ledge 83 of the lower surface of the selector plate 11 is recessed slightly, as are the corresponding regions 18' and 54 of the upper surface 18 of the restrictor plate 14 so that maximum force is applied in the region of the three channels 30, 41 and 42. The spring 93 is compressed between the upper surface of the selector plate 11 and the lower surface of the clamping plate 90 so as to ensure that pressure continues to be applied to the plate even if the components should wear. Leakage from the timing channel 30 is further reduced by the two O-rings between which it is located. Because it is critical that the timing output is accurately controlled it is important that leakage from this channel is minimized. Additional O-rings

could be provided to reduce leakage from the other channels 41 and 42 but, because these are less critical, it has been found that further O-rings are not needed. By arranging the O-rings so that they are compressed laterally, an effective seal is provided whilst providing only a minimal resistance to relative rotation and little need for lubrication.

The arrangement of the three channels 30, 41 and 42 is such that, when the user desires the maximum flow rate, the selector plate 11 is in its furthest clockwise position when viewed from above, with the holes 72 and 73 located at the widest ends of the channels 41 and 42 adjacent the inlet hole 46 and the outlet hole 50 respectively. In this position, it can be seen that the hole 69 is located at the end 36 of the timing channel 30 farthest from the inlet 34 so that the flow from the outlet 4 to the timing valve is a minimum, thereby ensuring a slow timing rate. When the selector plate 11 is rotated anticlockwise, the rate of flow of oxygen supplied to the patient is reduced but with a corresponding increase in the frequency of breathing pulses. This arrangement helps ensure that, for example, when used on children, the frequency is automatically increased when the set flow rate is reduced.

The manner in which the cross-sectional area of a channel varies along its length determines how the rate of flow of gas output from the channel varies as the selector plate is rotated. There will be some reduction in flow as the effective length of a channel is varied even if there is no change in its cross section because of the skin frictional effect of the gas flowing over the surfaces of the channel in a relatively confined space. The cross-section need not taper gradually but could be stepped and it need not vary in the same sense along the length of the channel since it could, for example, reduce in cross-section and then increase in cross-section.

Many different arrangements and numbers of channels are possible. The channels could all be located at the same radial distance or they could all be located at different distances, or in any combination of these locations. In addition to the channels, the restrictor could include simple apertures to provide an on/off function with different fluid paths. Examples of different arrangements of channels are shown in Figures 6A to 6D

The invention is not confined to use with gas but could be used with liquids.

There are manufacturing advantages in having a restrictor plate separate from the support plate but, since both are fixed with one another against relative rotation, it would be possible for the manifold assembly to be a single component.

The arrangement described above requires flexible pipes to make connection to the selector plate, because this part needs to rotate relative to the manifold. However, it would be possible to avoid the need for flexible pipes, such as by the arrangement shown in Figure 7 where holes 100 movable along channels 101 are provided on the end face of a drum 102. The drum 102 is rotatable about its axis in a casing 103 and has passages 104 extending through it connecting the holes with annular grooves 105 spaced along the drum. Connection is made to the annular grooves 105 and hence to the holes 100 above the channels, via openings 106 spaced along the casing.

The continuous channels used in the present invention have advantages over previous arrangements where a series of aperture of different sizes is movable relative to a flow path to effect control of fluid flow. With this prior arrangement there can be a risk of the flow path being located between aperture, thereby preventing any flow. This could be dangerous in a patient resuscitator and some other applications.

There are advantages in providing for relative rotational movement between the manifold and the selector plate but it would be possible to provide for other forms of relative movement between the components, such as, for example linear movement, in which case the channels would be linear or straight.