US2776659A - Respiratory apparatus - Google Patents

Description

Jan. 8, 1957 s. s. WILKS ET AL RESPIRATORY APPARATUS 5 snezs-sheet 2 Filed Jan. 26. 195,4

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Jan' .8, 1957 s. s. wlLKs ETAL RESPIRATORY APPARATUS Filed Jan. 26. 1954 5 Sheets-Sheet 5 www w fr ma www www Jan. 8, 1957 'Filed Jan. 26, 1954 S. S. WILKS ETAL RESPIRATORY APPARATUS 5 Sheets-Sheet 4 Jan. 8, 1957 Q s, W|LK$ ET Al. 2,776,659

RESPIRATORY APPARATUS Filed Jan. 26, 1954 5 sheets-sheet 5 /5 IIIIIIIIIIIIIII? t United States Patent() RESPIRATORY APPARATUS Syri-el S. Willis, San Marcos, and Frank V. Garbich, Sarl Antonio, Tex., assignors to the United States ot Ameri- Y ca as represented by the Secretary of the Air Force Application January 26, 1954, Serial No. 4%,369 8 Claims. (Cl. 12S- 30) (Granted under Title 35, U. S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without payment to us of any royalty thereon.

This invention relates to an improved light weight respirator particularly adapted for the transport of polio patients by aircraft. A respirator in accordance with the invention provides a light weight shell forming a respirator chamber enclosing the body of the patient and having an external head rest and a llexible plastic sealing collar of conventional construction. The respirator housing is provided with litter handles for carrying the patient into the aircraft and suitable supports. A self contained device for alternately creating positive and negative pressures in the respirator housing is provided which includes a direct current motor driven blower and power driven cam actuated valving which connects the inlet side of the blower to the chamber to create a negative pressure therein to cause inflation of the patients lungs and then to connect the outlet side of the blower to the respirator chamber to create a positive pressure therein to cause exhalation. The cams which control the valving are driven through reduction gearing by an adjustable speed direct current motor to thereby adjust the rate of the respiratory cycle. Air bleed controls are provided on the respirator housing to control the magnitude of the positive and negative pressures in the chamber and the blower capacity is such that a large volume of air is drawn in and expelled from the chamber ventilating and cooling the patients body and eliminating objectionable odors which would arise if a closed system were employed. The system also provides for creating a continuous suction which can be employed as an aspirator in conjunction with an intratrachial catheter to withdraw mucus and liuids from the throat of the patient. The self contained blower and valve mechanism may also be employed in conjunction with a conventional oxygen mask as an automatic resuscitator.

Other features of the invention will become apparent by reference to the detailed description hereinafter given and to the appended drawings in which:

Fig. i is a view showing a respirator constructed in accordance with the invention and energized from an external power supply and;

Fig. 2 is a side View, partly in section illustrating the valve and blower assembly.

Fig. 3 is a top view partly in section taken on line 3-3 of Fig. 2.

Fig. 4 is a top plan View of the valve mechanism and gear housing, partly in section.

Fig. 5 is a top plan View of the valve and blower assembly.

Fig. 6 is a fragmentary view illustrating details of a cam driving gear train;

Fig. 7 is a schematic wiring diagram of the power supply system.

Fig. 8 is a top plan view partly in section of the valve assembly with the resuscitator unit attached.

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Fig. 9 is a perspective view of cams employed in the invention.

Fig. 10 is a side elevation of the valve and blower assembly used with a mask as a resuscitator.

Fig. 11 is a front elevation of the resuscitator manifold.

Referring now to Fig. 1 the respirator generally indicated bythe reference numeral 1 comprises a light weight metal frame and bottom structure 2 which provides a bed support for the patient. The frame 2 is provided with vertical legs 3 for supporting the respirator on the lloor and with four handle extensions 5 which enable the entire assembly to be carried like a litter.

At one end of 4the frame 2 there is secured a fixed housing head 6 made of aluminum alloy sheet or other light weight material which is semi-circular in cross section and provided with a slanting end wall 7 provided with an aperture, not shown, for emergence of the patients head and neck. The end wall 7 is provided with a conventional ilexible neck seal 8 and a hinged plate 9 which supports a pillow 10 for the patients head.

At its other end the frame 2 has a vertical end wall 12 of semi-circular cross section. A lid generally indicated by the reference numeral 15 and made of thin aluminum alloy sheet material is formed with a semicircular cross-section and is hinged along one edge as indicated at 16 to frame 2, The lid 15 is adapted to be clamped along its other longitudinal edge by means not shown to the frame 2. The lid 15 is provided with suitable sponge rubber gaskets not shown which engage with the head 6 and end wall 12 when the lid 15 is clamped down to minimize air leakage.

The lid 15 is provided with conventional access doors 18 along each side and with transparent viewing windows 19 on its top for viewing the patient. The lid 15 when folded back on its hinge 16 permits a patient to be placed in the respirator after which the lid 15 is closed and clamped with the patients head and neck projecting through the sealing collar 8 and the head resting on the pillow 10.

A self contained valve and blower assembly generally indicated by the reference numeral 25 includes a blower housing 26 and a valve housing 60 secured thereto and having a valve actuating assembly secured on the front side thereof. A handle is provided lfor carrying the valve and blower assembly when disassembled from the respirator end wall 12.

As seen in Figs. 2 and 3 the blower housing 26 which is in the form of a rectangular box is provided on its upper side with a cover 27 which serves as a mounting for the valve assembly housing 60. The housing 26 is provided with a centrally disposed longitudinally extending partition wall 30 which divides the housing into two chambers 31 and 32. The chamber 31, called the vacuum chamber, communicates by means of a port 33 in the cover 27 with the interior of the valve housing 60 and similarly the chamber 32, known as the pressure chamber communicates by means of a port 34 in the cover 27 with the interior of the valve housing 60.

The wall 3l) of housing 26 is suitably apertured to receive the housing of a high speed series wound D. C. motor generally indicated by the reference numeral 35. The motor 35 has an armature shaft 36 journalled in the end bell of the housing which is provided with `a series of ports 37 which communicate with chamber 31 and allow air from the chamber to pass through cooling passages 38 (Fig. 3) in the stator of the motor 35, to cool and ventilate the motor. The cooling passages 38 also conduct air into the inlet of a two stage blower generally indicated by the reference numeral 40.

The blower 40 is provided, as seen in Fig. 3, with a casing portion 41 which is provided with a mounting ange 42 which is fastened by bolts 43 to the partition wall and also serves to mount the motor 35. The blower is also provided with a second casing portion 44 which provides a bearing for the outer end of the motor shaft 36 which drives the blower 40.

Also as seen in Fig. 3 the blower 40 is provided with a tirst stage centrifugal waved impeller 45 which is driven by the motor shaft 36 and receives air at .its inlet from the cooling passages 38 of motor 35. The output of air under pressure from impeller 45 passes through the inward flow stationary guide vanes 46 into the inlet of the second stage centrifugal impeller 47 which also is driven by the motor shaft 36. The blower output passes from the second stage impeller 47 through ports 48 in the casing element 44 directly into the pressure chamber 32 of the housing 26 and passes by way of port 34 into the interior of valve housing 60.

The motor 35 which is of the series wound direct current type operates on direct current of from 24 to 30 volts and rotates under load at speeds from 15,000 to 20,000 R. P. M. With the motor 35 and blower 40 in operation negative or suction pressure of 30 cm. or more of water will prevail in inlet chamber 31 and a similar positive pressure of 30 or more cm. of water will prevail in the pressure chamber 32. The continuous sub-atmospheric pressure existing in chamber' 31 is utilized for an aspirator which as seen in Fig. 2 comprises an aspirator line cock 50 mounted on the cover plate 27 and adapted to be connected to an external fluid trap not shown which in turn is connected by a exible tubing to an intratrachial catheter which can be used to withdraw liuids and mucus from the patient's throat. The cock 50 communicates by means of a passage 51 with the upper end of a cylindrical container 52 positioned within the chamber 31. The interior of container 52 communica-tes by means of ports 53 with the chamber 31 so as to normally create a suction in passage 51 and aspirator cock 50 when the cock is opened and connected to an aspirator tubing not shown. If the external Huid trap not shown, completely lls with fluid, the overflow will enter the container 52. A float 54 is provided in the container 52 which will rise and by means of a valve 55 mounted thereon will shut off passage 51 to prevent the uids from owing over through ports 53 into the chamber 31. A removable drain plug 56 is provided for draining any fluids collected in container 52.

As seen in Fig. 2 the valve assembly includes a valve housing 60 of rectangular shape, the rear vertical wall 26a of which is formed by an extension of the corresponding end wall of the blower housing 26. The valve housing 60 `is open on its bottom and is secured to the cover plate 27 of housing 26. The valve housing 60 is provided with a cover plate 62.

As seen in Fig. 4, the valve housing is provided on its interior with a longitudinally extending partition wall 64 and transverse partition walls 65 and 66 which divide the valve housing 60 into four chambers respectively indicated by reference numerals 68, 69, and 71. A circular passage 72 affords communication between chambers 68 and 69 and a similar passage 73 connects chambers 70 and 71, Chamber 69 is normally open to the atmosphere by means of a port 74 formed inthe valve housing cover plate 62 and a similar port 75 connects chamber '71 to the atmosphere. The chamber 68 communicates by means of port 33 in the cover plate 27 with the suction chamber 31 of the blower housing 26 and similarly the chamber 70 of the valve housing communicates by means of the port 34 in cover plate 27 with the pressure chamber 32 of the blower housing 26.

The passage 72 s encircled by an annular valve seat 78 providing a passage 79 for flow from chamber 69 through passage 72 into chamber 68. A similar annular valve seat 80 formed on the partition wall 66 encircles the passage 73 and provides a passage 82 for llow from chamber 71 through passage 73 into the chamber 70.

An annular valve seat 84 provides a flow passage 86 interconnecting the chamber 68 by means of an aperture 4 88 in a sealing gasket 90 and a registering aperture 12b in the end Wall 12 of the respirator 1 of Fig. 1 to the interior of the respirator. Similarly an annular valve seat 94 provides a ow passage from chamber 70 to the interior of the respirator by way of gasket aperture 88 and the aperture 12b in the respirator end wall 12.

The annular valve seats 78 and 84 are axially aligned and spaced apart at their inner ends to cooperate with a circular double seating poppet valve 100. Similarly the annular valve seats and 94 are axially aligned and spaced apart at their inner ends to cooperate with a similar double seat poppet valve 102.

Since the means for actuating the valves and 102 are identical only one means will be described and corresponding parts of the other actuating means are indicated by the same reference numerals primed. The valve 100 is slidably mounted on a valve rod 104 which in turn is slidable in a valve guide bushing secured to thc front wall of the valve housing 60. The bushing 105 is slotted at 106 and cooperates by means of a pin 107 to prevent the valve rod from turning in the valve guide bushing 105. At its outer end the valve rod is provided with a cam follower roller 108.

At its outer end the valve rod 104 is provided with a washer 110 which engages a slidable spacer bushing 112 which engages the rear side of the valve 100 to move the valve in one direction. On the opposite side of the valve 100 a compression spring 114 encirclcs the Valve rod 104 and at one end contacts the valve face and at its opposite end engages a collar pinned to the valve rod 104. The collar 115 is provided with lateral extensions 116 which serve as anchorages for one end of a pair of retraction springs 118 which are anchored at their outer ends to the front wall of valve housing 60.

When valve 100 is moved by the actuating rod or valve stem 104 to the position shown in Fig. 4, the valve will move with the rod 104 until the face of the valve seats on the annular valve seat 84. Any further movement or over travel of the valve rod 104 merely causes the collar 115 to further compress the spring 114. When the actuating force is removed from valve rod 104, the retrac- -tion springs 118 pulls the collar 115 and valve ro-d 104 in the upward direction as seen in Fig. 4. The spring 114 then elongates and when the washer 110 engages the bushing 112 the valve 100 will be lifted from the valve seat 84 and will continue in motion until it engages the valve seat 78.

Movement of the valve 100 in the direction to seat the valve on valve seat 84 is effected by means of a cam 120 which engages the follower roller 108 and it is returned to seat on valve seat 78 by the force of retraction springs 118. The provision for overtravel of the valve rod 104 after the valve is seated ensures proper valve seating and simplies the tolerances which would otherwise be necessary. The cam 120 controls the positive pressure part of the respiratory cycle and is mounted on one end of a cam shaft 121, a corresponding cam 122 being mounted on the opposite end of the cam shaft 121 and actuating cam follower roller 1081 and valve rod 1041 to move valve 1021 to control the negative pressure part of the respiratory cyc e.

The cam shaft 21 is provided with a squared end portion 121a on which may be fitted a hand crank 124 (shown in phantom) for rotating the cam shaft manually in case of power failure of the cam driving motor.

As further seen in Fig. 4, the cam shaft 121 is journalled for rotation by means of bearings 126 and 127 in a gear case 130 mounted on the front of the valve housing 60. The cam shaft 121 is adapted to be driven by a gear 132 which meshes with a pinion gear 134 which together with a larger gear 135 form a gear cluster mounted for free rotation on a stud 136 carried in a block 138 which is journalled for rotation in the wall of gear case 130 and adapted to be rocked by an external slotted lever 140 (note Figs. 2 and 6) and locked by a wing nut 141.

The gear 135 (Fig. 4) meshes with a pinion 139 fast on a shaft 142 journalled at one end in the gear housing 130 and at its other end in the block 138 concentric with the rocking axis of the latter (see Fig. 6). A worm gear 143 is also xed on shaft 142 and meshes with a worm 144 iixed on the lower end of an armature shaft 145 which forms part of an adjustable speed direct current motor 146 mounted on the top of the gear casing 130, see Fig. 2. The speed of motor 146 can be adjusted to vary the speed of the cam shaft 121 to adjust the respiratory cycle rate from 6 to 30 cycles per minute by means of a rheostat 150 having an indicating and adjusting knob 151, see Figs. 2 and 7.

When the lever 140 is unlocked and rotated counterclockwise as seen in Figs. 2 and 6 the block 138 is rocked and gear 135 walks around pinion 139 and pinion 134 is unmeshed from driving engagement with gear 132 permitting the cam shaft 121 to be manually rotated by hand crank 124 in case the motor 146 `should fail. Rotation of lever 140 in the opposite sense and locking the same permits driving the cam shaft 121 by motor 146 through the gear train, worm 144, worm gear 143, shaft 142, pinion 139, gear 135, pinion 134 and gear 132 xed on shaft 121.

As seen in Fig. 5, plastic strips 160 are removably secured to the top plate 62 of the valve housing 60 and have lilter screens 162 adapted to register with the ports 'I4 and 75 in the plate 62 and these strips may be reversed in position to block these ports when a manually actuated emergency pulsator pump not shown is employed. A handle 165 is provided for carrying the valve and blower assembly when disassembled from the respirator 1.

Again referring to Fig. 7 the plug in conductor 170 which connects to both motors 35 and 146 may be connected to an external power supply such as indicated at 172 which may contain a step down transformer and rectifier unit (not shown) adapted to be connected to any convenient source of 110 v. A. C. The plug in conductor 170 may be connected directly to a 25 volt battery or to the similar direct current source on an aircraft.

Operation After a patient is placed in the respirator 1 (Fig. 1) and conductor 170 plugged in to a source of 24 volts D. C., motors 35 and 146 will be energized and the respirator will begin functioning.

As previously described above when motor 35 is operating air will be drawn in from chamber 31 and passing through motor inlet ports 37 Fig. 2, and motor cooling passages 38 Fig. 3, will pass into the two stage blower 40 and be delivered under pressure to the chamber 32 Fig. 3.

Assuming the valves in the position shown in Fig. 4, air from the ambient atmosphere will enter the port 74, enter the chamber 69 and pass through passages 72 and 79, the valve 100 being open and pass into chamber 68. From chamber 68 the air will flow downward through the port 33 into the chamber 31 Fig. 3, from whence it passes through motor 35 into blower 40 and out ports 48 into chamber 32. Air under pressure will flow upward from chamber 32 Fig. 3, through port 34 Fig. 4, into the charnber 70. The valve 102 will be seated as seen in Fig. 4 on Valve seat 80 and the air under pressure will flow from chamber 70 through the passage 96 in valve seat 94 and into the apertures 88 and 12b and thence into the interior of the respirator and will build up pressure therein. The delivery pressure of the blower 40 is considerably in excess of the desired positive pressure in the respirator 1 and a flap valve 180 is provided in the iid 15 of the respirator 1 see Fig. l which allows suicient flow through the respirator to limit the positive pressure to the order of 30 centimeters of water. The excess ilow flushes out stagnant air and odors out of the respirator and ventilates the patient.

When the cam 120 has rotated to the position yshown in Fig. 2, the retraction springs 118 will move the valve rod 104 and valve 100 until the latter is seated on valve seat 78, sealing off the chamber 68 from communication with the atmosphere. Air will then flow through a bleed valve 182 Fig. l, into the respirator and then through passages 12b and 88 from the interior of the respirator and through passage 86 of valve seat 84 into chamber 68. From chamber 68 it will ow down through port 33 into chamber 31 of Fig. 3. The ow is from chamber 31, Fig. 3 through motor 35 into blower 40 as previously described. Since the volume of the respirator is fixed, removal of air therefrom reduces the pressure therein below atmospheric pressure and bleed valve 182 is adjusted to allow suicient inow from the atmosphere into the respirator, so that the negative pressure is limited to about 30 centimeters of water. Fresh air entering the respirator through the bleed valve 182 is further useful in Ventilating the interior of the respirator and cooling the patient.

The valve 102 in the meantime will have moved by actuation of valve rod 1041 by cam 122 (Fig. 4) until it seats on annular valve seat 94 blocking communication between the interior of the respirator and chamber 70.

Chamber 70, however will then be in free communication with chamber 71 and the atmosphere through port 75. The air under pressure delivered by the blower 40, Fig. 3 through ports 48 will flow up from chamber 32 through port 34 into chamber 70 of the valve housing and then escape to atmosphere by passing through passages 82, 73 chamber 71 and port 75 as described above.

It will be noted that the motor 146 is continuously driving the cam shaft 121 at a slow rate of from 6 to 30 R. P. M. giving a corresponding number of complete respiratory cycles. The proper cycling rate is determined by a physician and depends on the age and condition of the patient, children requiring .a higher rate than old people. It will be further noted that when cam 120 Fig. 4 engages the roller 108 and moves the valve rod 104 inward valve will seat on valve seat 84 to block communication between the suction side of the blower and the interior of the respirator 1. Simultaneously the cam 122 allows the retracting springs 118l to move the valve 102 in the opposite direction so as to deliver air from the positive pressure side of the blower 40 to the respirator. The valves are approximately oppositely phased so that when the suction side of the blower is connected to the respirator the positive pressure side is vented to the atmosphere and when the positive pressure side of the blower is connected to the interior of the respirator the negative pressure or inlet is connected to the atmosphere. The fact that the valves are yieldingly mounted on the actuating rods which can overtravel the valve movement in either direction permits a variation in the valve phasing during parts of the cycle. This fact permits the cams to be shaped such as to give the desired rates of positive and negative pressure build up and decay and the duration of the positive and negative pressure portions of the cycle.

The approximate shape of the cams 120 and 122 is shown in Fig. 9, which also shows the phase relation of the cams. The shapes of the cams were determined experimentally to give a cyclic pressure variation in the re..- pirator corresponding to experimentally determined res piration pressures deemed by physiologists as desirable. These cam shapes also provide for valve rod overtravel.

Resusctator In order to use the blower and valve assembly for example as shown in Fig. 2 as a resuscitator the entire assembly is unclarnped from the respirator 1 and a resuscitator manifold generally indicated by the reference numeral 200 is clamped to the back plate 26a of the housing 26 with the sealing gasket 90 interposed as seen in Fig. 8. As seen in this figure the manifold housing is in the form of a. rectangular box 201 which is open on its rear side and provided at each end with a rod 202 threaded to receive clamping wing nuts 203 so that the manifold assembly may be clamped to the valve and blower assembly with the chamber 204 in the manifold 7 communicating with the ports 86 and 96 Fig. 4, of the valve. mechanism. The chamber 204 replaces the respirator.

The manifold housing 201 is provided on its upper side with three outlet conduits 205, 206 and 207 to each of which an oxygen mask inlet tube may be connected and the ones not in use may be plugged with a rubber stopper.

On its front face the manifold housing 201 is drilled with a plurality of ports arranged in a rectangular pattern in two sets one indicated by reference numeral 203 and the other by the numeral 210. A flap valve 212 is positioned in the chamber 204 and adapted to cooperate with the ports 208 to admit air from the atmosphere to the chamber 204. An adjusting screw 214 limits the amount of opening of the valve 212 and hence controls the sub-atmospheric pressure in the chamber 204. A similar ap valve 215 is mounted on the front of the manifold housing 201 to cooperate with the ports 210 to control the discharge of air under pressure from the chamber 204 and thus limit the positive pressure in the chamber. The extent of movement of the valve 215 is determined by an adjusting screw 216.

The manifold 201 is further provided with a dual range gauge 220 (Fig. ll) for measuring the magnitude of the positive and negative pressures in the chamber 204 for the purpose of adjusting the valves 212 and 215.

When an oxygen mask 22S Fig. l0 is connected by means of its inlet tube 228 to one of the outlet conduits such as 205 the resuscitator can be placed into operation, The valve and blower assembly is energized from a 24 volt direct current source and the cycling rate of the valve mechanism adjusted by operation of the speed control rheostat knob 151 (Fig. 2) positive and negative pressure cycles will be produced in the resuscitator chamber 204 in exactly the same manner as previously described with respect to the operation of the respirator.

When the manifold chamber 204 is filled with air under perssure this pressure is transferred to the mask 225 and inates the lungs of the patient Wearing the mask. When the cycle changes to produce a negative pressure in the manifold chamber 204 the reduction is transferred to the mask and air is exhaled from the patients lungs. The maximum pressures during inhalation and exhalation can be adjusted to suit the medical needs of the patient and may range from 35 centimeters to water positive to 20 centimeters of water negative pressure.

To prevent rebreathing some of the exhaled air a vent tube 230 is provided on the mask, see Fig. which allows fresh air to enter the mask 225 and inlet tube 228 during the exhalation part of the cycle.

We claim:

l. Respirator apparatus comprising a respirator chamber adapted to enclose at least the thoracic regions of the human body, means providing a restricted passage for the flow of air into and out of said chamber, an air pump having an inlet and an outlet, power means for continuously driving the pump, tirst valve means operative to connect the inlet of the pump to the respirator chamber to produce a flow therethrough from said restricted passage and a subatmospheric pressure therein, a second valve means operative to simultaneously connect the outlet of the pump to atmosphere, said lirst and second valve means being alternately operable respectively to connect the inlet of the pump to atmosphere and the outlet of the pump to the respirator chamber to cause a ilow therethrough at superatmospheric pressure, a cam shaft, a pair of cams mounted on said shaft each operable to cyclically actuate a respective one of said valve means and an adjustable speed motor for continuously driving said cam shaft.

2. Respirator apparatus comprising a respirator chamber adapted to enclose at least the thoracic regions of the human body, means providing a restricted passage for the tiow of air into and out of the chamber, an air pump having an inlet and an outlet, power means for continuously driving the pump, a pair of alternately operable two position valves, each valve having a tiow connection to the respirator chamber and to the ambient atmosphere, the rst of said valves having a further iow connection to the inlet side of said pump and the second of said valves having a further flow connection to the outlet side of the pump, the first of said valves in one position connecting the respirator chamber to the inlet of the pump and connecting in its other position the inlet of the pump to the atmosphere, the second valve in one position connecting the respirator chamber to the outlet of the pump and in the second position connecting the outlet of the pump to the atmosphere, cam means for moving said valves alternately, one valve being in its first position when thc other valve is in its second position and vicc versa, power means for continuously driving said cam means and means for adjusting the cyclic rate of operation of said cam means.

3. Respirator apparatus comprising a respirator chamber adapted to at least enclose the thoracic regions of the human body, means providing an adjustable restricted passage for the ow of air into and out of said chamber, an air pump having an inlet and an outlet, a first passage means connected to Ithe pump inlet, a second passage means connected to the pump outlet, a pair of lateral conduits operatively associated with said first passage means, one of the conduits being connected to t'ne atmosphere and the other conduit being connected to the respirator chamber, a valve movable alternately to open one of said conduits and to close the other and vice versa, a pair of lateral conduits operatively associated with said second passage means one of the conduits being connected Ito the atmosphere and the other conduit being connected to the respirator chamber, a valve movable alternately to open one of said conduits and to close the other and vice versa, a valve rod yieldingly coupled to one of said valves, a second valve rod yieldingly connected to the other of said Valves, a cam having a predetermined shape for actuating one of said valve rods, a second cam having a predetermined shape different than the first named cam for actuating the other of said valve rods and power actuated driving means for continuously driving said cams with a fixed phase relation to each other, the yielding connection between each of said valve rods and its associated valve permitting the phase relation of the valves to be controlled by the cam shapes irrespective of the fixed phase relation of the cams to each other.

4. For use with respiratory apparatus of the character described a pump and valve assembly comprising a housing, a pump in said housing and having an inlet and an outlet, a partition in said housing dividing the housing into two chambers one an inlet chamber connected to the pump inlet and the other a discharge chamber connected to the pump outlet, a valve housing mounted on said lirst named housing and having a first valve chamber connected to the said inlet chamber and a second valve chamber connected to the said discharge chamber, a separate conduit in each of said valve chambers adapted to be connected to external respiratory apparatus to produce pressure changes therein, a separate conduit in each of said valve chambers connected to the atmosphere, a double acting valve in each valve chamber adapted to cooperate With the conduits therein to alternately connect the valve chamber to the utilizing apparatus and to the atmosphere, and actuating means connected to each of said valves to continuously actuate the valves in opposite phase relation said actuating means being yieldingly connected to each of the valves whereby the actuating means may overtravel relative to the valves in each direction of movement thereof.

5. The structure as claimed in claim 4, in which the actuating means for the valves comprise valve rods yieldingly connected to the valves, cam followers on each valve rod, a rotatable cam associated with each cam follower, a cam shaft for driving said cams in a xed relation to each other, adjustable speed power meansv v ly moving the valves in one direction and spring means associated with each valve actuating rod for moving the rod and associated valve in the opposite direction of movement.

` 6. In a resuscitator system, a face mask adapted to be worn by the patient, a manifold chamber connected to said face mask, an air pump having an inlet and an outlet, power means for continuously driving said air pump, a rst valve adapted when moved in one position to connect the inlet of the pump to atmosphere and in a second position to connect the inlet of ythe pump to the manifold chamber, a second valve adapted when in one position to connect the pump outlet to the atmosphere and in a second position to connect the pump outlet to the manifold chamber, means for continuously and cylically actuating said valves in opposite directions of movement to cyclically and alternately connect said manifold chamber to the pump inlet to create a negative pressure in the manifold chamber then to the pump outlet to create a. positive pressure in the manifold chamber and means for adjustably regulating the maximum negative and positive pressures in the manifold chamber.

7. The structure as claimed in claim 6, in which the means for actuating the valves include a pair of continuously rotating cams each cam associated with a respective valve, and the cams being respectively shaped to give a predetermined rise, decay and duration of the positive and negative pressure portions of the cycle.

8. The structure as claimed in claim 6, in which the face mask is provided with an air bleed opening adapted to lush the mask and connecting conduit with fresh air during the exhalation portion of the resuscitator cycle to reduce rebreathng exhaled air.

References Cited in the le of this patent UNITED STATES PATENTS Re. 20,226 Drinker et a1 Jan. 5, 1937 1,087,942 Hammond Feb. 24, 1914 1,136,517 Drager Apr. 20, 1915 2,427,665 Emerson Sept. 23, 1947 2,456,724 Mullikin Dec. 21, 1948

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