US3056401A

US3056401A - Sphygmomanometer

Info

Publication number: US3056401A
Application number: US81871A
Authority: US
Inventors: Edward B Greenspan; Mosely John De Sola
Original assignee: Individual
Current assignee: GREENSPAN
Priority date: 1961-01-10
Filing date: 1961-01-10
Publication date: 1962-10-02
Anticipated expiration: 1979-10-02
Also published as: FR1310264A; GB923936A; CH392771A

Description

Oct. 2, 1962 Filed Jan. 10, 1961 E. B. GREENSPAN ETAL SPHYGMOMANOMETER 3 Sheets-Sheet 1 INVENTORS 0h/4f0 5. Gees s ay x/o m D6 50m 1170545 Oct. 2, 1962 E. B. GREENSPAN ETAL 3,056,401

SPHYGMOMANOMETER Filed Jan. 10, 1961 3 Sheets-Sheet 2 INVENTORS fowmga 15. 6 1950151 4 7 BY Jon/y 05 cm QSLE) Arr-019N675 3,656,4tl1 SPHYGMGMANQMETER Edward lb. Greenspan and Eohn tie Sela Mosely, New

York, N.Y.; said de Sela Moseiy assignor to said Greenspan Filed 3am. lltl, 1%1, Ser. No. 81,871 Claims. (61. 128-215) This invention relates to apparatus for measuring blood pressure, and more particularly to a self-recording sphygmomanometer for automatically determining and indicating systolic and diastolic blood pressures.

Generally, a sphygmomanometer is a clinical instrument for measuring the maximum (systolic) and minimum (diastolic) blood pressures indirectly, i.e., without insertion of a pressure reading device into an artery. It consists of an inflatable cuff which is wrapped about a patients arm, an aneroid manometer for indicating pressure in the cuff, and a sufllating bulb equipped with a manually operable bleeder valve. The cuff is inflated until it tightens sufficiently to occlude the artery in the arm, i.e., stop the blood flow therein. The air is then allowed to bleed off, so that pressure in the cuff falls, and the operator listens to the artery below the cuff with a stethoscope until he hears a pulsing rush of blood commence. The pressure at this point is the systolic pressure. As the air pressure in the cuff continues to fall, a point is reached where the rush of blood becomes inaudible. Pressure at this point is the diastolic blood pressure.

The ordinary method of taking blood pressure as set forth above has many disadvantages chief among which is the need for a trained and skilled person to properly use the method which involves interpretation of arterial sounds sensed through a separate instrument. This is particularly a problem where repeated rapid blood pressure readings are required, for example, during an operation, Where it is highly undesirable to distract the surgeon and other highly skilled personnel, and Where it is impractical to have present a technician solely for the purpose of taking blood pressure. Another major drawback is the fact that extraneous noises some of which may emanate from the subject himself (bone noises, etc.) can interfere with the taking of the blood pressure as can, of course, normal outside noises present in a room. Also, the patient must remain very still; and generally the conventional method of taking blood pressure is beset with various inconveniences.

As a result of the foregoing it has been recognized that a self-recording sphygmomanometer automatically responsive to pressure, not sound, would be of very great value to the medical profession. Various attempts to construct such an instrument have been made, but the results have not been satisfying since the instruments were cumbersome, unreliable, inaccurate, diflicult to use and expensive to produce.

It is a principal object of our present invention to provide an automatic sphygmomanometer sensitive to the presence and strength of pulses in an artery and capable of providing accurate readings of the systolic and diastolic blood pressures.

It is another object of our invention to provide a device of the character described which is direct indicating, i.e., has an output that is displayed and, if desired, can be automatically recorded.

It is a further object of our invention to provide a device of the character described the readings of which require no interpretation by the observer other than those which bear on the condition of the subject.

It is still another object of our invention to provide a device of the character described which is simple and uncomplicated in use.

3,955,4fi1 Patented Get. 2, 1962 It is an additional object of our invention to provide a device of the character described which displays only the most recent measurement and Will retain this until another measurement is to be made.

It is still a further object of our invention to provide a device of the character described which is insensitive to audible disturbances or to movements of the patient or manipulation of the patient by medical, technical or other personnel.

It is another object of our invention to provide a device of the character described which causes no discomfort to the patient, i.e., in which the cuff need remain inflated for only a minimum amount of time, no more, and usually far less, than with manual taking of blood pressure.

it is an additional object of our invention to provide a device of the character described which is rugged, long lasting and durable.

it is a further object of our invention to provide a device of the character described which can be produced relatively inexpensively and which lends itself to permanent installations, as in laboratories and operating room, desk installations, as in a physicians ofiice, and to portable forms as for house calls.

Other objects of our invention in part will be obvious and in part will be pointed out hereinafter.

Our invention accordingly consists in the features of construction, combinations of elements, and arrangements of parts which will be exemplified in the device hereinafter described and of which the scope of application will be indicated in the appended claims.

In the accompanying drawings in which is shown one of the possible embodiments of our invention.

FIG. 1 is a broken away front View of an automatic sphygrnornanometer constructed in accordance with our invention, the same being illustrated in use on an arm;

FIG. 2 is an electric circuit diagram for the sphygmomanometer;

FIG. 3 is an enlarged fragmentary sectional view of the means for converting systolic air pressure impulses into systolic electrical pulses;

FIG, 4 is an exploded view of the sphygmomanometer;

FIG. 5 is an end view of the sphygmomanometer with the casing removed;

FIG. 6 is a sectional view taken substantially along the line 6-6 of FIG. 5 and showng the aneroid manometer, i.e., the pressure sensitive means, of the sphygmomanomoter; and

FIG. 7 is a sectional view taken substantially along the line 77 of FIG. 5.

In general we achieve the several objects of our invention by providing a means such as an inflatable cuff which furnishes a source of air pressure and of air pressure impulses that commence at substantially a subjects systolic pressure and terminate substantially at a subjects diastolic pressure. Suitable means is included to sense these pressure impulses and to transduce them into a train of electric pulses. Furthermore, we include a pressure sensitivity means, such as an aneroid manometer, which is continually responsive to the air pressure in the cuff and which drives two indicating markers, one for systolic and one for diastolic pressure. The drive between the pressure sensitive means and the two indicating markers is elastic, so that if the indicating markers are unrestricted, i.e. unblocked or unrestrained, they will continuously indicate the mean prevailing pressure within the cuff. To denote the systolic and diastolic pressures for any given subject two suitable blocking means are included one of which is responsive to the initiation of the train of electric pulses and the other of which is responsive to the termination of the train of electric pulses. The first of the blocking means is operative upon actuation thereof to lock the systolic marker, and the second of the blocking means is operative upon actuation thereof to lock the diastolic marker, so that upon initiation of the train of electric pulses the systolic marker will be resettably fixed to indicate systolic pressure and upon the cessation of the train of electrical impulses the diastolic marker will be resettably fixed to indicate diastolic pressure.

In the preferred form of our invention the diastolic marker is continuously resettably fixed and freed as the electric pulses repeat, the freeing taking place upon the occurrence of an electric pulse, and the fixing taking place upon the termination of a pulse, whereby after occurrence of the last electric pulse the diastolic marker will remain fixed, subject, of course, to resetting upon reuse of the sphygmomanometer.

Referring now in detail to the drawings, the reference numeral denotes a sphygmomanometer constructed in accordance with and embodying our instant invention.

One of the elements of the sphygmomanometer is an inflatable cuff 12 of conventional construction. As is usual, said cuff includes an inflatable elongated hermetically sealed internal casing of an impermeable sheet-like material, such, for instance, as rubber, desirably encased in an external fabric sleeve. The ends of the sleeve include cooperating rapidly attachable detachable elements such as a hook and eyes (not shown) for enabling the cuff to be circumscribed around and attached to a patients arm in a snug fit thereon when the internal casing is uninflated.

As is customary in inflatable cuffs for sphygmomanometers, the internal casing has two

conduits

14, 16 in communication with the hollow space contained therewithin. One of the conduits 14 is secured to a sufflating squeeze bulb 18 having an egress check valve (not shown) at the front end thereof connected with the conduit 14 through a fitting 20. The sufflating bulb includes an ingress check valve (not shown) at its rear end 22. Hence, when the bulb is deflated, air will be forced therefrom through the fitting 20 and conduit 14 into the cuff to raise the pressure of the air contained therewithin and, when the bulb is released, communication between it and the cuff will be cut off by the egress check valve, and air will flow into the same through the ingress check valve. The fitting 20 also is conventional. It includes a bleeder valve. When the handle 24 thereof is in one position the bleeder valve is closed and when the handle 24 is rotated away from closed position the bleeder valve will be progressively opened to permit air from the cuff 12 to leak out through it. As is well known, the bleeder valve is manipulated for reading of blood pressure so as to cause a slow reduction of the pressure of the air in the cuff.

The other conduit 16 transmits the pressure of the air in the cuff to the reading portion of the sphygmomanometer 10.

Said reading portion is housed in a casing 26 which contains all of the working parts of the sphygmomanometer with the exception of the cuff, conduits and sufflating bulb.

One of the elements provided within the casing is a means 28 for sensing the air impulses and transducing them into electrical pulses, i.e. a means for generating a train of electric pulses in response to a train of air pressure impulses. Said pulse generating means constitutes a hollow vessel 29 (see FIGS. 1 and 2) which conveniently is composed of two

halves

30, 32 secured to one another in any suitable manner, as for example, by a threaded connection. The space within the vessel 29 is subdivided into two chambers 34, 36 by a flexible transverse diaphragm 38. It will be apparent that if the pressure within the cuff is introduced into a first one of these chambers, a momentary fluctuation in such pressure will cause movement of the diaphragm. De-

A sirably, to enhance flexibility of the diaphragm, the same is concentrically corrugated.

Moreover, to increase the sensitivity of the means 28 for sensing the air pressure impulses it is desirable to introduce into the second of the chambers (the balance, i.e. reference, chamber) a mean air pressure which is approximately the same as the fluctuating pressure in the first air chamber, so that the diaphragm only has to be responsive to a change in pressure occasioned by the air pressure impulses, i.e. to a change in differential pressure. To this end the conduit 16 is connected through a Y-fitting 40 to the opposite ends of the vessel 29, and more specifically, to the two chambers 34, 36. One branch of the Y-fitting 40 is connected by a conduit 42 to a nipple 44 communicating with the reference chamber 34, and the other branch of the Y-fitting is connected by a conduit 46 to a nipple 48 communicating with the pulsing chamber 36. The bore extending through the nipple 44 is constricted as at 50', so that changes in air pressure within the conduit 42 will not be immediately transmitted to the reference chamber 34. Accordingly, the pressure of the air within said reference chamber is, at any time, equal to the mean pressure within the cuff 12. However, the pressure of the air within the pulsing chamber 36 is substantially instantaneously responsive to fluctuations of pressure within the cuff 12, so that if any air pressure impulses occur within said cuff, they immediately 'will deflect the diaphragm 38 either toward or away from the reference chamber 34 depending upon whether the momentary change in such air pressure is positive or negative. Thus, if there is a continuous series (train) of air pressure pulses within the cuff 12, the diaphragm 38 will fluctuate in position and in direct response to such air pressure impulses With no noticeable lag.

At this point we will interrupt the description of the sphygmomanometer to mention certain physical factors which are inherent in the use of the inflatable cuff 12 and of which we take advantage in the construction and operation of our sphygmomanometer.

When, in ordinary use, a cuff such as the inflatable cuff 12 is wrapped around a patients limb, usually an upper arm, and the pressure therein is increased to a pressure greater than the systolic pressure of the patient, the cuff acts as a constricting tourniquet to occlude arterial flow of blood in the limb. However, because the pressure exerted by the cuff is elastic, each time that a pulse of blood encounters the obstruction of the constriction in the artery occluded by the tourniquet there will be an ensuing slight rise of air pressure Within the cuff which We shall refer to as a supersystolic air impulse. This pressure rise is comparatively small and in an ordinary sphygmomanometer with a needle indicator manifests itself as a barely noticeable vibration of the needle in the range of about /2 mm. and seldom exceeding 2 or 3 mm.

If now the handle 24 of the bleeder valve is manipulated to permit slow leakage of air from the cuff, the constricting pressure will gradually reduce until it reaches a point where it will permit momentary opening of the artery each time a systolic pulse of blood approaches the cuff. In other words, as soon as the air pressure in the cuff substantially matches the systolic blood pressure of the subject a systolic pulse of blood will flow through the artery beneath the cuff. This flow will slightly reduce the volume of the inflated cuff and thereby temporarily raise the pressure of the air within the same so as to create a momentary air impulse which air impulse will be transmitted through the conduit 16 to the reading portion of the sphygmomanometer.

Obviously, as the subjects pulse continues to beat, fresh systolic air impulses will be generated at succes sively lower mean air pressures, so that there will be a train of air impulses transmitted from the cuff to the impulse sensing means 28. These impulses are of continuously decreasing mean air pressure because the bleeder valve still is permitting air to leak out of the end.

The amplitude of said pressure impulses, which we shall refer to as systolic air impulses is in the order of 2 mm. and sometimes substantially higher, e.g., up to 4 mm. However, the systolic air impulses are of an appreciably greater magnitude than the supersystolic air impulses generated within the cuff at a cuff pressure above the subjects systolic pressure and therefore may be readily distinquished from the same by the marked difference in degree of movement of the flexible diaphragm 33. Ordinarily, said diaphragm will move at least twice as far for a systolic air impulse as for a supersystolic air impulse.

As the air pressure within the cuff continues to decrease through the bleeder valve a point ultimately will be reached where such pressure is below the subjects diastolic pressure. At this time there is a substantially free flow of blood into the limb and the systolic air impulses no longer will be generated in the cuff.

To recapitulate, when the air pressure in the cuff is supersystolic, there will be no systolic air impulses generated. When the pressure in the cuff reaches the patients systolic pressure, a train of systolic air impulses will be initiated and will continue to be maintained so long as the pressure Within the cuff is above the patients diastolic pressure. Finally, when the pressure within the cuff reaches the patients diastolic pressure the train of systolic air impulses will be terminated. Thus, the diaphragm 38 will vibrate in a systolic magnitude so long as the pressure within the cuff is between the patients systolic and diastolic pressures.

As thus far described, we have only indicated the physical arrangement within the sensing means 28 for procuring mechanical movement responsive to the train of systolic air impulses, to wit, the diaphragm 38. Said means further includes an arrangement for generating a train of electrical pulses in response to such mechanical movement. The latter arrangement includes an electric contact 52 mounted on that side of the diaphragm 38 which faces the reference pressure chamber 34. Desirably, the contact 52 is mounted near the center of the diaphragm where maximum movement prevails. Said contact 52 forms the movable contact of a pulsing switch the stationary contact of which is indicated by the reference numeral 54.

In order to utilize the

contacts

52, 54 as a repeating electric switch, we either insulate the contact 54 from the upper half "30 which carries the same, or insulate the

halves

30, 32 from one another, or, as shown, make said upper half 30 of an electrically non-conductive material, e.g., a phenolformaldehyde condensation resin (Bakelite). The other half 32 of the vessel 29* is made of an electrically conductive material, e.g., brass.

The stationary contact 54 is mounted within the reference chamber 3 in juxtaposition to the movable contact 52, but spaced therefrom when the diaphragm 38 is unflexed. However, it should be close enough to the movable contact to be engaged thereby upon the occurrence of a systolic air impulse within the pulsing chamber 35.

Conveniently, in order to enable the sensing means 28 better to distinguish between systolic air impulses and supersystolic air impulses, means is included to vary the spacing between the two

contacts

52, 54 when the diaphragm 33 is idle. To this end the stationary contact 54 is mounted on a toe 56 extending transversely from a leg 58 that is longitudinally slidable in an opening 60 in the upper wall of the casing half 38'. The leg 58 is non-circular, i.e., square, and the opening 69 is of matching configuration so as to accurately locate the stationary contact 54 above the movable contact 52. The upper end of the leg do is enlarged, as at a head 62, which is captively but rotatably secured within the lower end of an adjusting screw 64 that is threaded into a tapped bore 66 in the upper wall of the casing. With this arrangement it merely is necessary to turn the screw 64 so as to secure any desired spacing between the two contacts of the pulsing switch. A lead 68 extends away from the adiusting screw and a lead 70 extends away from the conductive casing half 32. Accordingly, said lead wires will be electrically connected when the

contacts

52, 54 are engaged and will be disconnected upon the opening of said contacts.

The sphygmomanometer it) further includes, as mentioned earlier, a pressure sensitive means continually responsive to the air pressure within the cuff and controlling the mechanical positioning of an element as a function of said pressure.

Said pressure sensitive means comprises an aneroid manometer constituting a closed chamber 72 having a flexible front wall 74- which is concentrically corrugated to enhance flexibility. The chamber is in the form of a pancake so as to obtain a large surface for said flexible wall and thus make it quite sensitive to internal air pressure.

Access to the chamber is provided by a nipple 76 that is connected by a conduit 78 to one branch of a Y-fitting 8%) the other branch of which is connected to the Y-fitting 46. The conduit in leads to the Y-fitting 80.

It will be obvious that when air pressure within the cuff 12 increases, the flexible wall 74 of the chamber 72 will bulge outwardly as indicated by the arrow A, the extent of such movement desirably being an approximately linear function of said air pressure so that it is convenient to read the air pressure on a dial having approximately uniform graduations.

It is convenient, in order to simplify the operation of our sphygmomanometer 19, to convert the translatory movement of the flexible wall 74 into a rotary movement which can drive a needle marker. Any suitabie conversion mechanism can be used for this purpose, one such mechanism 82 being illustrated herein.

Said conversion mechanism 82 includes an axially rotatable torque bar 34 extending diametrically across and in front of the flexible wall 74. The ends of the torque bar are journalled, as at 85, in brackets 86 that are connected to a stationary vertical frame plate 88. Fixed to and extending rearwardly from the torque bar 3 toward the flexible wall 74 is a feeler finger 90 the tip 92 of which is curved horizontally to lie approximately parallel to the plane of the flexible wall 74. Said tip is adapted to abut, i.e., to touch or follow, the wall 74- and, in the preferred form of our invention, is slightly offset from the center of this wall. It will be appreciated that, with this arrangement, as long as the tip of the finger contacts the wall, in and out movement of the wall will cause a corresponding oscillation of the torque bar 84 about a vertical axis.

An actuating rod 94 extends forwardly from the torque bar 84 and is operationally integral therewith so as to swing with said torque bar upon oscillatory movement thereof occasioned by flexion of the wall 74. The stationary plate 88 is provided with an opening 96 to pass said actuating rod 94. The forward tip of the actuating rod bears against a leg 98 of a gear sector 1% having gear teeth M2. The sector 100 turns about a horizontal shaft 164 fixed to and extending forwardly from the stationary plate 88. It will be quite clear that, with the foregoing arrangement, as the wall 74 flexes it will cause a corresponding rotation of the gear sector 100.

The gear teeth 192 mesh with a motion amplifying pinion 106 fast on a horizontal forwardly extending shaft 198 the rear end of which is journalled in the stationary plate 88. Thereby, the comparatively small angular movement of the gear sector 100 occasioned by flexion of the wall 74 will be amplified into a considerable angular movement which is desirable for easy reading of the sphygmomanometer.

As thus far described the only motion of the flexible Wall '74 that will rotate the pinion 106 and shaft 108 is an outward movement. A retrograde movement of the wall 74 will not pull back with it the tip 92 of the feeler finger 91 Moreover, the connection between the actuating rod 94 and leg 98 similarly is a simple abutment. To maintain these two pairs of abutting elements in contact with one another we provide a spiral torsion spring 116 having one end thereof anchored in a post 112 on the stationary plate 88, and the other end thereof anchored to the pinion shaft 1118. Said spring urges the pinion 1115 in a counter-clockwise direction, as viewed in FIG. 6, so as to bias the leg 98 against the rod 94 and also to bias the tip 92 of the feeler finger against the flexible Wall 74. Said spring additionally prevents backlash in the meshing pinion and gear sector. The spring 110 is a comparatively light spring, i.e., a hair spring, and the restraint imposed thereby on the flexion of the wall 74 is so slight as to be unnoticeable.

On the front end of the shaft 1138 we mount an indicating needle 114 which is readable against a graduated scale 116 on a stationary dial 118. This needle 114 will, therefore, when the sphygmomanometer is in use, furnish to the observer an instantaneous reading of the air pressure within the cuff 12. The needle will show a high pressure when the sufi'lating bulb initially is actuated to constrict the cuff on the subjects arm and will show the progressive decrease in pressure after opening of the bleeder valve and passage of the cuff pressure first through the systolic and then through the diastolic pressure points of the subject.

The sphygmomanometer also includes a systolic pressure needle 121 and a diastolic pressure needle 122 mounted to turn about axes concentric with that of the shaft 1118 and to be read against the same scale 116 as that of the cuff air pressure needle 114, although, as will be appreciated, this is a convenience rather than a necessity.

The systolic needle 120 is fast on a sleeve 124 and the diastolic needle 122 is fast on a. sleeve 126. The outer sleeve 126 is journalled in a front stationary vertical plate 128 and the inner sleeve 124 is telescopically received and journalled within the outer sleeve 126. Furthermore, the inner sleeve 124 is journalled on the shaft 108 which extends through the same. The front end of the shaft 108 is journalled in a stationary bracket 130, and the rear end of the shaft 108 is journalled in a rear stationary plate 132 as well as in the plate 88. Thus, the shaft 1118, the inner sleeve 124 and the outer sleeve 126 are telescopic and concentric and turn about a mutual, i.e., common, axis of rotation.

A ratchet, which conveniently is in the form of a gear 134, is fixed to the inner sleeve 124 where it extends rearwardly beyond the outer sleeve and another ratchet, conveniently in the form of a second gear 136, is fixed to the outer sleeve 126. To maintain the two ratchets in proper relative position we include a spacer sleeve 138.

Suitable elastic means are included independently to bias the systolic needle 1241 and the diastolic needle 122 to angular orientations matching that of the cuff air pressure needle 114. Said means should be light in action so that they can be readily overridden. However, they should be positive and sensitive so that they will be reliable and eflicient. For example, said means may comprise biasing springs.

In the case of the systolic needle 120 we have shown the elastic (overridable) means as constituting alight hairpin torsion centering spring 1411 having a pair of radial legs connected by a helical section wrapped about the portion of the shaft 108 protruding forwardly from the inner sleeve 124. One radial leg terminates in a rearwardly extending branch 142 that engages the systolic needle 120. The other radial leg has a forwardly extending branch 144 that engages the cuff air pressure needle 114. For the diastolic needle 122 the elastic (overridable) means comprises a light hairpin torsion centering spring 146 having a pair of radial legs connected by a helical section likewise wrapped about the forwardly protruding portion of the shaft 108. One of the radial legs terminates in a rearward- 1y extending branch 148 that engages the diastolic needle 122 and the other radial leg terminates in a forwardly extending branch 1511 that engages the cuff air pressure needle 144.

The radial legs of both hairpin centering springs are so mutually positioned when said springs are relaxed that the systolic and

diastolic needles

120, 122 will be in alignment with the cuff air pressure needle 114 at such time. Hence, as the cuff air pressure needle turns in either direction it will be followed by the systolic needle and the diastolic needle, unless, of course, movement of either of said

needles

120, 122 is restrained in a manner which soon will be described.

The

hairpin centering springs

140, 146 are very light, so that if either or both of the

needles

120, 122 is restrained, the needle 114 still is able to move under the influence of the spring or the flexible wall 74. Moreover, if desired, to insure joint movement of all three needles when the air pressure in the cuff initially is raised to its high point, we may provide the cuff air pressure needle 114 with an abutment 151 that extends rearwardly thereof into the path of travel of both the systolic and diastolic needles. Thereby, as the cuff air pressure needle 114 moves to a high reading the abutment 151 will engage the systolic and diastolic needles to move them along and in alignment with said cuff air pressure needle. Said abutment also serves to prevent oscillation of the systolic and diastolic needles under the influence of the centering springs.

It will be apparent that when the air pressure in the cuff decreases, the systolic and diastolic needles will follow the needle 114 in its movement downward around the scale 116. However, as mentioned previously, pursuant to our invention suitable means is included firstly, to block downward movement of the systolic needle 1211 upon the detection of the first systolic air impulse by the sensing means 28, and secondly, to block downward movement of the diastolic needle 122 upon cessation of the train of systolic air impulses. More specifically, as soon will be appreciated, the diastolic needle is locked after each systolic air impulse and is released upon the occurrence of each fresh systolic air impulse, so that the needle will be finally locked for any given cycle of operations, i.e., for any given subject, upon the occurrence of the last systolic air impulse sensed.

Adverting now to the means for locking the systolic needle upon the sensing of the first systolic air impulse and the corresponding first systolic electrical pulse, for this purpose we provide a stop pawl 152 in the shape of an angled lever having a radial portion 154 and an offset portion 156. The offset portion terminates in a tooth which is the functioning element of the pawl and is adapted to engage the systolic ratchet 134. The systolic stop pawl 152 is journalled on a shaft 157 that extends between the

parallel plates

128, 132. Said systolic pawl is urged into operative engagement with the ratchet 134 by an elongated helical spring 153 having its lower end anchored to the radial portion 154 and its upper end anchored to the stationary plate 132 (see FIG. 5).

An unlocking slat 160 mounted on an unlocking shaft 162 is disposed directly above the radial portion 154 of the systolic pawl 152. Thereby, if the unlocking shaft 162 is depressed, it will lower the systolic pawl out of engagement with the systolic ratchet and thus leave the systolic needle free to follow movement of the cuff air pressure needle 114.

Means is included to maintain the unlocking shaft 162 in its depressed (unlocking) position which permits free movement of the systolic ratchet 134. Such means comprises an annular buttress groove 164 on the shaft 162 which is adapted to cooperate with a detent 166. As long as the detent 166 engages the flat side of the buttress groove the shaft 162 is prevented from moving upwardly under the biasing influence of the spring 158 and of another like spring soon to be described.

The detent 166 is under the control of a solenoid 168. When the actuating coil 170 of said solenoid is energized, it will pull the detent 166 out of the groove 164 and thereby allow the systolic spring 158 to raise the systolic pawl 152 into engagement with the systolic ratchet 132.

The shaft 162 includes an unlocking (reset) button 172 protruding above the top wall of the casing 26 in order to enable said shaft to be depressed when the sphygmomanometer is set up for operation.

The means for locking the diastolic needle upon the cessation of successive systolic air impulses and the corresponding systolic electrical pulses constitutes a second stop pawl 174 in the shape of an angled lever having a radial portion 176 and an otfset portion 178. The offset portion terminates in a tooth which is the functioning element of the pawl and is adapted to engage the diastolic ratchet 136. The diastolic stop pawl 174 is journalled on the same shaft 157 as that on which the systolic stop pawl 152 is journalled. Said diastolic stop pawl is urged into operative engagement with the diastolic ratchet 136 by an elongated helical spring 180 having its lower end anchored to the radial portion 176 and its upper end anchored to the stationary plate 128 (see FIG.

The unlocking slat 160 includes a portion disposed directly above the radial portion 176 of said diastolic pawl 174. Thereby, when the reset button 172 is depressed it will lower the diastolic pawl out of engagement with the diastolic ratchet and thus leave the diastolic needle 122 free to follow movement of the cuff air pressure needle 114 under influence of the centering spring 146. As in the case of the systolic ratchet, the diastolic ratchet will be maintained free (unlocked) by the detent 166.

A solenoid 182 is included for electrical unlocking (freeing) of the diastolic pawl 174. The armature 184 of the solenoid is connected by a link 186 to the diastolic pawl 174 so that when the actuating coil 188 of said solenoid 182 is energized it will depress the tooth of the diastolic pawl to free the diastolic ratchet 136.

For a reason which later will be apparent our sphy momanometer is provided with a momentary snap switch 190 the actuating element 192 of which is disposed in the path of travel of the radial portion 154 of the systolic pawl 152. The momentary switch 190 is a single-pole double-throw switch.

The electric circuit for our sphygmomanometer is illustrated in FIG. 2. The same is comparatively simple and will be seen to include a battery 194 (not physically shown) one terminal of which is connected by a lead 196 to ground, e.g., to the chassis (the metallic stationary plates and base of our sphygmomanometer). The battery is sufficiently powerful to energize the actuating coils of the

solenoids

168, 182. The other terminal of the battery is connected by a lead 198 to one of the normally open contacts 200 of an ofi-on switch 202 physically mounted in a convenient place, for example, at the top of the casing 26 (see FIG. 1). The other contact of the ofi-on switch is connected by the lead 70 to the movable contact 52 of the sensing means 28. The stationary contact 54 of said means is connected by the lead 68 to the blade 204 of the momentary switch 190. The normally open contact 206 of the switch 190 is connected by a lead 208 to one terminal of the actuating coil 170 of the solenoid 168 the other terminal of which is connected by a lead 210 to ground. The normally closed contact 212 of the switch 190 is connected by a lead 214 to one terminal of the actuating coil 188 of the solenoid 182 the other terminal of which is connected by a lead 216 to ground. It thus will be apparent that the solenoids are connected for energization in parallel with a series circuit including the battery 194, the ofi-on switch 202, the

contacts

52, 54 and the switch 190, the switch 190 operating to selectively 10 determine which of the two solenoids is actuated at any given time.

In describing the operation of our sphygmomanometer, let it be assumed that the instrument is in the condition which exists after it has read a subjects systolic and diastolic blood pressures. At this time the cuff 12 will be deflated and off the subjects arm. The cufi air pressure needle 114 will be at the lower end of the scale 116 and the systolic and diastolic needles 120', 122 will be at the former subjects systolic and diastolic blood pressures, respectively. The toggle arm of the ofi-on switch 202 will be in off position so that the contacts of said switch are open. The unlocking shaft 162 and reset button 172 will be in their uppermost positions.

To prepare our sphygmomanometer for operation, we first depress the reset button 172. 'It will be noted that prior to depression of said button both pawls are held in looking engagement with their associated ratchets by the

springs

158, 180 and the switch 190 is not actuated, so that the blade 204 thereof engages the normally closed contact 212.

When the reset button 172 is depressed the unlocking slat will engage the

radial portions

154, 176 of the systolic and

diastolic pawls

152, 174 to unlock (free) the two ratchets. The button will be held in depressed condition by engagement between the detent 166 and the buttress groove 164, the solenoid 168 being idle because the

contacts

52, 54 are open (said solenoid is biased idle by a spring 169). Immediately upon disengagement of the ratchets the systolic and

diastolic needles

120, 122 will swing into alignment with the cuff air pressure needle 114 at the lower end of the scale 116, being turned to this position by the centering hair springs 140, 146 and being prevented from oscillating by the abutment 151. Moreover, when the radial portion 154 of the systolic pawl 152 is depressed to its unlocking position it will engage the actuating element 192 of the switch 190 to move the switch blade 204 against the normally open contact 206 and thereby prepare the actuating coil 170 of the solenoid 168 for energization. However, this solenoid will not be energized as yet because the

contacts

52, 54, as well as the off-on switch 202, are open.

The sphygmomanometer now is ready for operation,

, the cuff 12 is wrapped about a subjects limb and the sufflating bulb 18 manipulated to raise the pressure of the air within the cuff. As this pressure is raised the cult air pressure needle 114, followed by the systolic and diastolic needles, will quickly swing to a high reading on thescale 116, the reading being higher than the patients systolic blood pressure.

Next the toggle of the oil-on switch is manipulated to close the contacts 200 thereof. Closure of said contacts connects the battery 194 to the contact 52. However, at the time, the

contacts

52, 54 are spaced apart since the pressures in the two chambers 34, 36 are substantially equal (the supersystolic air impulses are not strong enough to close said contacts) and, accordingly, no voltage will be applied to the contacts of the switch and to the actuating coil of the solenoid 168.

At this time the air pressure in the cuff is high enough to occlude flow of arterial blood and all three

needles

114, 120, 122 are in alignment. Next the doctor turns the handle 24 to open the bleeder valve, thus permitting a slow steady leakage of air to occur with a corresponding slow steady reduction of air pressure in the cuff 12. Accordingly, the air pressure within the chambers 34, 36 gradually drops in pace with the change of mean air pressure in the cult. There will be a slight vibration of the diaphragm 38 upon the occurrence of each systolic heat, but, because of the occlusion, the ensuing supersystolic air impulse is comparatively slight and, in any event, smaller than the amount required to flex the diaphragm sufiiciently to engage the contact 52 with the 75 contact 54.

When the pressure within the cuff drops to the subjects systolic pressure a systolic pulse of blood will flow under the cuff and this will create a systolic air impulse in the cuff which will be transmitted to the pressure chamber 36 where it will raise the diaphragm to an extent suflicient to engage the contact 52 with the contact 54. Closure of these contacts will complete the energization circuit from the battery 194 to the switch 1% the blade of which at the time engages the normally open contact 206- that has been closed by depression of the unlocking button 172 through the slat 160. Hence, the first systolic electric pulse will be fed through the actuating coil 170 of the solenoid 168. This pulse will pull the detent 166 out of engagement with the buttress groove 164 so as to release the shaft 162. As sOon as the restraining pressure of the shaft is released the biasing spring 158 will pull the systolic pawl 152 into engagement with the systolic ratchet 134, thereby locking the systolic ratchet and the systolic needle 120. Accordingly, said needle will register the subjects systolic blood pressure.

The movement of the systolic pawl 152 into locking engagement will release the switch 190, so that the blade 204 thereof will engage the normally closed contact 212 to place the actuating coil 188 of the solenoid 182 in circuit with the battery 194. It will be appreciated that when the detent 166 releases the shaft 162 the biasing spring 180 also pulls the diastolic pawl into locking engagement with the diastolic ratchet 136, so that the diastolic needle 122 likewise will be locked. However, the systolic air impulse is a momentary one and the contacts 50', 52 only are closed momentarily. When they reopen both the systolic and diastolic needles will remain locked, but when said contacts are next reclosed they thereupon will energize the actuating coil 188 of the solenoid 182 to pull the armature 184 thereof closed against the idling spring 183. This shifts the link 186 and pulls down the diastolic pawl 172 to momentarily free the diastolic ratchet 136.

In the interim between the two systolic electrical pulses the mean air pressure within the cuff 12 will have dropped and the cuff air pressure needle 114 will be at a lower point on the scale 116. Hence, when the diastolic ratchet is released, the centering hair spring 146 will swing the diastolic needle into registry with the cuff air pressure needle 114 at its lower position. Then, as the momentary systolic electrical pulse is terminated, the diastolic needle will again be relocked. This action is repeated continuously, i.e., the diastolic needle is locked, the cuff air pressure needle 114 drops, the diastolic needle is unlocked and realigned with the cuff air pressure needle, and then it is locked again. Eventually, when the cuff air pressure reaches the subjects diastolic blood pressure, the systolic air impulses stop and the systolic electrical pulses terminate, so that the solenoid 182 is not again actuated and the diastolic needle remains locked at a pressure which is substantially equal to the subjects diastolic blood pressure. Further downward movement of the cuff air pressure needle 114 will not be followed by the diastolic needle.

It will be appreciated that the physical appearance and design of our sphygmomanometer 1!) will depend upon the particular use of any specific instrument. For eX- ample, said sphygmomanometer may be quite large if it is intended to be mounted on a wall for use, for instance, in hospitals, or the sphygmomanometer may be of medium size and suitably housed for placement on a doctors desk. Still further, our sphygmomanometer may be made quite smallfismall enough to be packed in a physicians bag, so that it can be carried about with him.

It thus will be seen that we have provided a device which achieves the various objects of our invention and is well adapted to meet the conditions of practical use.

As various possible embodiments might be made of our above invention, and as various changes might be made in the embodiment above set forth, it is to be understood that all matter herein described or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

Having thus described our inventoin we claim as new and desire to secure by Letters Patent:

1. A self-recording sphygmomanometer comprising an inflatable cuff having bleeder means, pulsing means responsive to the gas pressure within the cuff for creating a train of systolic impulses initiating at a Subjects systolic blood pressure and terminating at the subjects diastolic blood pressure, a systolic pressure indicator controlled by the gas pressure within the cuff, a diastolic pressure indicator controlled by the gas pressure within the cuff, means actuated by the pulsing means on the initial systolic impulse of the train to set the systolic indicator, and means actuated by the pulsing means on the last systolic impulse of the train to set the diastolic pressure indicator.

2. A self-recording sphygmomanometer comprising an inflatable cuff having bleeder means, a pressure sensitive means continually responsive to gas pressure in the cuff, pulsing means sensing systolic pressure impulses in the cuff and creating a train of systolic impulses initiating at a subjects systolic blood pressure and terminating at the subjects diastolic blood pressure, a systolic pressure indicator, overridable means connecting the systolic pressure indicator to the pressure sensitive means so that the systolic pressure indicator will, when unrestrained, indicate the gas pressure in the cuff, a diastolic pressure indicator, overridable means connecting the diastolic pressure indicator to the pressure sensitive means so that the diastolic pressure indicator will, when unrestrained, indicate the gas pressure in the cuff, means actuated by the pulsing means on the initial systolic impulse of the train to lock the systolic indicator, and means actuated by the pulsing means on the last systolic impulse of the train to lock the diastolic pressure indicator.

3. A self-recording sphygmomanometer comprising an inflatable cuff having bleeder means, a pressure sensitive means continually responsive to gas pressure in the cufi, pulsing means sensing systolic pressure impulses in the cuff and creating a train of systolic impulses initiating at a subjects systolic blood pressure and terminating at the subjects diastolic blood pressure, a systolic pressure indicator, elastic means connecting the systolic pressure indicator to the pressure sensitive means so that the systolic pressure indicator will, when unrestrained, indicate the gas pressure in the cuff, a diastolic pressure indicator, overridable means connecting the diastolic pressure indicator to the pressure sensitive means so that the diastolic pressure indicator will, when unrestrained, indicate the gas pressure in the cuff, means actuated by the pulsing means on the initial systolic impulse of the train to lock both indicators, and means momentarily actuated by the pulsing means on subsequent systolic impulses of the train to momentarily unlock the diastolic pressure indicator, whereby the diastolic pressure indicator will remain locked at the gas pressure in the cuff at the time of occurrence of the last systolic impulse of the train.

4. A self-recording sphygmomanometer comprising an inflatable cuff having bleeder means, a pressure sensitive means continually responsive to gas pressure in the cuff, pulsing means sensing systolic pressure impulses in the cuff and creating a train of systolic impulses initiating at a subjects systolic blood pressure and terminating at the subjects diastolic blood pressure, a systolic pressure indicator, overridable means connecting the systolic pressure indicator to the pressure sensitive means so that the systolic pressure indicator will, when unrestrained, indicate the gas pressure in the cuff, a diastolic pressure indicator, overridable means connecting the diastolic pressure indicator to the pressure sensitive means so that the diastolic pressure indicator will, when unrestrained, indicate the gas pressure in the cuff, means actuated by the pulsing 13 means on the initial systolic impulse of the train to lock both indicators, and means momentarily actuated by the pulsing means on each subsequent systolic impulse of the train to momentarily unlock the diastolic pressure indicator, whereby the diastolic pressure indicator will remain locked at the gas pressure in the cuff at the time of occurrence of the last systolic impulse of the train.

5. A self-recording sphygmomanometer comprising an inflatable cufi having bleeder means, pulsing means responsive to the gas pressure within the cuff for creating a train of systolic impulses initiating at a Subjects systolic blood pressure and terminating at the subjects diastolic blood pressure, means transducing the systolic impulses into a train of systolic electric pulses, a systolic pressure indicator controlled by the gas pressure within the cuff, a diastolic pressure indicator controlled by the gas pressure within the cuff, means actuated by the transducing means on the initial systolic electric pulse of the train to set the systolic indicator, and means actuated by the transducing means on the last systolic electric pulse of the train to set the diastolic pressure indicator.

6. A self-recording sphygmomanometer comprising an inflatable cuff having bleeder means, a pressure sensitive means continually responsive to gas pressure in the cuff, pulsing means responsive to the gas pressure in the cuff for creating a train of systolic impulses initiating at a subjects systolic blood pressure and terminating at the subjects diastolic blood pressure, means transducing the systolic impulses into a train of systolic electric pulses, a systolic pressure indicator, overridable means connecting the systolic pressure indicator to the pressure sensitive means so that the systolic pressure indicator Will, when unrestrained, indicate the gas pressure in the cuff, a diastolic pressure indicator, overridable means connecting the diastolic pressure indicator to the pressure sensitive means so that the diastolic pressure indicator will, when unrestrained, indicate the gas pressure in the cuff, means actuated by the transducing means on the initial systolic electric pulse of the train to lock the systolic indicator, and means actuated by the sensing means on the last systolic electric pulse of the train to lock the diastolic pressure in dicator.

7. A self-recording sphygmomanometer comprising an inflatable cuff having bleeder means, a pressure sensitive means continually responsive to gas pressure in the cuff, pulsing means responsive to the gas pressure in the cuff for creating a train of systolic impulses initiating at a subjects systolic blood pressure and terminating at the subjects diastolic blood pressure, means transducing the systolic impulses into a train of systolic electric pulses, a cuff gas pressure indicator controlled by the pressure sensitive means, a systolic pressure indicator, overridable means connecting the systolic pressure indicator to the pressure sensitive means so that the systolic pressure indicator will when unrestrained, indicate the gas pressure in the cuff, a diastolic pressure indicator, overridable means connecting the diastolic pressure indicator to the pressure sensitive means so that the diastolic pressure indicator will, when unrestrained, indicate the gas pressure in the cuff, means actuated by the transducing means on the initial systolic electric pulse of the train to lock the systolic indicator, and means actuated by the sensing means on the last systolic electric pulse of the train to lock the diastolic pressure indicator.

8. A self-recording sphygmomanometer comprising an inflatable cuff having bleeder means, pulsing means responsive to the gas pressure within the cuff for creating a train of systolic impulses initiating at a subjects systolic blood pressure and terminating at the subjects diastolic blood pressure, means transducing the systolic impulses into a train of systolic electric pulses, a systolic pressure indicator controlled by the gas pressure within the cuff, a diastolic pressure indicator controlled by the gas pressure Within the cuff, a solenoid actuated by the transducing means an the initial systolic electric pulse of the train to set the systolic indicator, and a solenoid actuated by the transducing means on the last systolic electric pulse of the train to set the diastolic pressure indicator.

9. A self-recording sphygmomanometer comprising an inflatable cuff having bleeder means, a pressure sensitive means continually responsive to gas pressure in the cuff, pulsing means responsive to the gas pressure in the cuff for creating a train of systolic impulses initiating at a subjects systolic blood pressure and terminating at the subjects diastolic blood pressure, means transducing the systolic impulses into a train of systolic electric pulses, a systolic pressure indicator, overridable means connecting the systolic pressure indicator to the pressure sensitive means so that the systolic pressure indicator will, when unrestrained, indicate the gas pressure in the cuff, -a diastolic pressure indicator, overridable means connecting the diastolic pressure indicator to the pressure sensitive means so that the diastolic pressure indicator will, when unrestrained, indicate the gas pressure in the cuff, a locking means for the systolic pressure indicator, a locking means for the diastolic pressure indicator, means biasing both said locking means to locking position, a manually controllable unlocking means for rendering the biasing means inoperable, detent means for holding the unlocking means in inoperable position, first actuating means operable by the first systolic electric pulse of the train to render said detent means inoperable so that both locking means become operable, and second actuating means operable by subsequent systolic electric impulses of the train to momentarily unlock the diastolic locking means, whereby the diastolic pressure indicator Will remain locked at the gas pressure in the cuff at the time of occurrence of the last systolic electric pulse of the train.

10. A self-recording sphygmomanometer as set forth in claim 9 wherein circuit means is included to render the first actuating means operable upon the first systolic electric pulse and the second actuating means operable upon the occurrence of subsequent systolic electric pulses.

11. A self-recording sphygmomanometer comprising an inflatable cuff having bleeder means, a pressure sensitive means continually responsive to gas pressure in the cuff, a pressure chamber having a flexible wall, a conduit connecting the interior of the pressure chamber to the cuff, whereby systolic pressure pulses generated in the cuff will pulsate the flexible wall in response to said pressure pulses to produce a train of systolic mechanical impulses that initiate at a subjects systolic blood pressure and terminate at the subjects diastolic blood pressure, a systolic pressure indicator, overridable means connecting the systolic pressure indicator to the pressure sensitive means so that the systolic pressure indicator will, when unrestrained, indicate the gas pressure in the cuff, a diastolic pressure indicator, overridable means connecting the diastolic pressure indicator to the pressure sensitive means so that the diastolic pressure indicator will, when unrestrained, indicate the gas pressure in the cuff, means actuated by the sensing means on the initial systolic mechanical impulse of the train to lock the systolic indicator, and means actuated by the sensing means on the last systolic mechanical impulse of the train to lock the diastolic pressure indicator.

12. A self-recording sphygmomanometer as set forth in claim 11 wherein a reference pressure chamber is provided on the opposite side of the flexible wall and wherein a conduit connects the reference chamber to the cuff to provide an average cuff pressure in said reference chamber.

13. A self-recording sphygmomanometer as set forth in claim 12 wherein a restricted passageway is provided between the reference chamber and the cuff to minimize gas pressure pulsations in the reference chamber.

14. A self-recording sphygmomanometer as set forth in claim 13 wherein the flexible wall has an electric contact operationally integral therewith, wherein a stationary electric contact is provided near and spaced from the wall contact, wherein circuit means is provided including said 75 contacts to transduce the systolic mechanical impulses into 1 5 systolic electric pulses, and wherein both actuating means are responsive to said systolic electric pulses.

15. A self-recording sphygrnornanometer as set forth in claim 14 wherein means is provided to vary the position of the stationary contact so as to adjust the spacing between the two contacts.

References Cited in the file of this patent UNITED STATES PATENTS 1,594,581 Uchling Aug. 3, 1926 1% Bradford J an. 9, 1940 Williams Apr. 4, 1944 Lippitt Aug. 1, 1944 Gilford Mar. 18, 1958 Boucke Mar. 3, 1959 Goolkasian Dec. 22, 1959 FOREIGN PATENTS Great Britain Dec. 9, 1929 France Aug. 13, 1934