Syringe

Jan. 26, 1943.

2,309,502

B. DOUGLAS

SYRINGE

Filed Dec. 16, 1940

Sheets-Sheet 1

<img file="US2309502A_D0001.tif" />

Jan. 26, 1943.

2,309,502

B. DOUGLAS

SYRINGE

Filed Dec. 16, 1940

Sheets-Sheet 2

<img file="US2309502A_D0002.tif" />

<img file="US2309502A_D0003.tif" />

<img file="US2309502A_D0004.tif" />

Jan. 26, 1943.

B. DOUGLAS

SYRINGE

Filed Deo. 16, 1940

2,309,502

Sheets-Sheet 3

<img file="US2309502A_D0005.tif" />

Patented Jan. 26, 1943

2,309,502

UNITED STATES PATENT OFFICE

2,300,502

SYRINGE

Beverly Douglas, Nashville, Tenn.

Application December 16,1940, Serial No. 370,399

Claims.

This invention relates to syringes and more particularly to syringes of the type which may be used for injecting under pressure or aspirating fluids of all kinds.

It is an important object of this invention to provide an improved syringe construction having means for automatically injecting or aspirating fluids, and additional means for manually controlling or braking the injecting or aspirating means whereby extremely accurate results may be obtained.

A further object is to provide, in a syringe of novel structure, brake controlling means so arranged that operation thereof will have no tendency to dislodge the needle of the syringe.

A further object of this invention is to provide a hypodermic syringe adapted for automatically delivering local anaesthetics such as novacaine or other drugs with sufficient force through a needle so as to result in an extremely efficient injection and to provide means controlling the force and amount of the fluid injected.

A further object is to provide a hypodermic syringe adapted to automatically aspirate fluids through a needle or nozzle and to provide means controlling the speed and amount of the fluid aspirated.

A further object is to provide an automatically operated hypodermic syringe having interchangeable spring seating means in order that either tension or compression spring means, or a combination thereof, may be used.

A further object is to provide a hypodermic syringe constructed and arranged to inject or aspirate predetermined amounts of fluid successively wherein the predetermined amounts may be varied.

A further object is to provide a hypodermic syringe of novel construction including means for injecting or aspirating predetermined 40 amounts of fluid successively and additional means for accurately controlling the speed with which such fluid is injected or aspirated.

A further object is to provide a hypodermic syringe of novel construction including means for injecting or aspirating predetermined amounts of fluid successively and means for arresting the delivery of such predetermined amounts either before or after such delivery has begun.

Other objects and advantages of the invention will become apparent during the course of the following description.

In the drawings I have shown several embodiments of the invention. In this showing:

(CI. 128—218.2)

Figure 1 is a perspective view of the syringe,

Figure 2 is a central longitudinal sectional view thereof, parts being shown in elevation,

Figure 3 is an elevation of the piston rod as5 sembly in partially assembled relationship,

Figure 4 is a left end elevation of the cap of the syringe,

Figure 5 is a section taken on line 5—5 of Figure 2,

Figure 6 is a similar view taken on line 6—G of Figure 2,

Figure 7 is an elevation of a spring and its seating means, the parts being shown separated,

Figure 7a is a fragmentary sectional view of 15 a tension spring and its seating means, parts being shown in elevation,

Figure 8 is a side elevation of a modification of the invention,

Figure 9 is a section taken on line 9—9 of Fig20 ure 8,

Figure 10 is an enlarged fragmentary side elevation of another modification of the invention,

Figure 11 is an end view thereof, a portion 25 being shown in section,

Figure 12 is a fragmentary section taken on line 12—12 of Figure 11,

Figure 13 is a fragmentary sectional view of another modification of my invention, ³⁰ Figure 14 is a view partly in elevation and partly in section of another modification of the invention,

Figure 15 is an end view thereof in elevation,

Figure 16 is a section taken on line 16—16 of 35 Figure 14,

Figure 17 is a fragmentary side elevation of another modification of my invention,

Figure 18 is a section taken on the line 18—i8 of Figure 17,

Figure 19 is a fragmentary side elevation of another modification of my invention,

Figure 20 is a section taken on the line 20—20 of Figure 19,

Figure 21 is an enlarged fragmentary perspec45 tive view of the invention in partially assembled relationship taken on the line 21—21 of Figure 19,

Figure 22 is an enlarged fragmentary section taken on the line 22—22 of Figure 19, parts being 50 shown in plan, and,

Figure 23 is an enlarged section taken on the line 23—23 of Figure 19.

Referring to the drawings, the numeral 10 designates the glass barrel of the syringe which is provided at one end with an externally threaded

2,309, boss 11 having an axial opening therethrough, the other end of the barrel being open and having an annular flange 12 for a purpose which will become apparent. An internally threaded member (3 having a centrally located opening 5 14 extending axially therein is secured to the boss ! i at one end and a hypodermic needle 15 is screwthreadedly or otherwise connected to the other end of the member 13. It will be seen that the openings through the needle 15, mem- 10 ber 13, and boss II form a continuous passage for the flow of fluid therethrough. It is apparent that any type of needle or nozzle may be substituted for needle 15.

The syringe is provided with an internally 15 threaded metallic cap member IS of substantial thickness (as clearly shown in Figure 2) in which is bored an axially extending opening 17 to provide a bearing for a piston rod 18. The metallic cap member 16 is also bored to provide a trans- 20 verse opening 19 for a brake rod 20 mounted to rock therein. As will be clearly seen in Figures 2 and 5, opening 19 extends partially into and transversely across opening 17 for a purpose to be described. Centrally of its length the 25 brake rod 20 is cut transversely to form an arcuate notch 21 to receive a portion of the piston rod 18 when the notch 21 is turned in a position parallel to the piston rod 18. It will be obvious that if brake rod 20 is rotated slightly in the 30 opening 19 the sides of the notch 21 will bind against the piston rod 18 in such manner as to prevent free sliding of the piston rod 18 through the opening 17. If desired the brake rod 20 may be eccentric in cross-section to secure an equiv- 35 alent braking action when it is rotated or a brake lever may be mounted to rotate on a pin in a vertical slot (Figure 19) in the top of the cap member 16 so that one extremity thereof bears directly on shaft 13 under the action of suitable ⁴⁰spring means.

Rigidly secured or keyed to the extremities of the brake rod 20 by means of screws 20' is a brake control handle 22 which is adapted by means of thumb pressure at 23 to cause brake ⁴⁵rod 20 to rock in the supporting opening 19. When the parts are in the position shown in Figure 2 the control handle 22 is in its full braking position, that is the sides of the notch 21 on brake rod 20 are exerting the maximum pressure against the piston rod 18. The control handle 22 is retained in its full braking position by suitable spring means such as a leaf spring 24 suitable mounted on the annular surface of the cap member 16 and strongly engaging the ^5r>under portion of member 23 to urge the same in a counterclockwise direction together with the brake rod 20 in the opening 19. It will thus become apparent that downward pressure by the thumb upon member 23 acts to rotate brake rod GO 20 in a clockwise direction so as to permit piston rod 18 to slide freely through the opening 17 as the sides of the notch 21 are no longer urged as a brake against the piston rod (8.

The various elements of the piston rod 18 are clearly shown in Figure 3. A metallic ring 01· handle 26 is screwthreadedly connected to piston rod 18 and may be secured thereto by a lock nut 27. A member 29 is screwthreadedly connected to the other end of the piston rod 18 and to a piston 31 and includes a swivel joint 30 in order to prevent any side stress developing between the piston 31 and the glass barrel 19 of the syringe during operation thereof. A washer 33 is also loosely mounted on member ⁷

502 to the right (Figure 3) of a pin 34. The piston 31 fits very snugly within the glass barrel 19 so as to prevent any leakage past the piston under any normal conditions of pressure or suction.

A spring seat 37 (Figures 2, 3 and 7) having an axial opening therethrough is adapted to be placed over piston rod 18 and abuts the internal surface of cap member IS. Two eyelets 35 are screwed into the cap 16 adjacent the opening 17, for a purpose to be described, and project through diametrically opposite notches 36 which are provided in the periphery of spring seat 37 (Figure 6). A compression spring seat 38 also having an axial opening therethrough is mounted on the member 29 of the piston rod 18 and abuts the pin 34. A compression spring 39 or compressible rubber tubing is slipped over piston rod 18 and securely confined between its seats 37 and 38 by screwing member 29 to piston rod (3. As an alternate form of construction, the screwthread connection between piston rod 18 and member 29 may be omitted and the rod and member made as an integral unit.

The syringe of the invention is simply and easily assembled as will now be prescribed. The piston rod 18 with the ring 26 connected thereto is inserted through the opening 17 of the metallic cap IS, thumb pressure being exerted at 23 on the lever 22 to permit the piston rod to freely slide over brake rod 29. Spring seat 37 is now placed over piston rod 18 and moved to a position abutting the cap member 16 as shown in Figure 2. The spring seat 38 is now placed over member 29 so as to abut the pin 34. A compression spring is now placed over the piston rod 18, its left end abutting spring seat 37 and its right end abutting spring seat 38. Member 29 is secured to the piston rod 18 and places the spring 39 under a slight initial compression. The piston 31 is now screwed on to the member 29 and the complete assembly is inserted into the glass barrel of the syringe. The assembly is completed by means of a threaded barrel 40 connecting cap 16 to a threaded sleeve 41 which bears against a resilient washer 41' about the annular flange ¢2 of the glass barrel 10. The threaded sleeve 41 is provided with a projecting lug 42 to act as a finger piece to facilitate the connection referred to.

Where piston rod 18 and member 29 are provided as an integral unit, assembly of the parts is accomplished by first removing the metallic ring 26 from the end of rod 18 after loosening lock nut 27 and removing same. Rod 18 is now threaded through the right end of the spring assembly shown in Figure 7 and through opening 17 in cap 16. With spring 39 in compression, thumb pressure on 23, which is employed during the introduction of rod 18 through opening 17, is released and ring 25 is screwed to the left end of rod IS and held there by lock nut 27.

In Figure 7α, I have disclosed the manner in which the tension spring is secured to the piston rod 18 and to the metallic cap IS. As viewed in this figure the left end of the tension spring 39', which is considerably shorter than the compression spring 39, is secured to the cap 16 by being passed through the eyelets 35. As the ends of tension springs are smaller in diameter than the balance of their length, the right end of the tension spring 39' will hook over and be retained by washer 33 which bears against the pin 34.

A further embodiment of the invention making ⁰ use of the identical spring seating means dis2,309,602 closed in Figure 7α contemplates the provision of a single spring actuating means which may have a combined tension and compression effect, thus obviating the necessity for changing springs from one type to another. The use of such a combination spring will reduce the capacity of the syringe by one-half but as this invention may be manufactured in any desired size this is a highly desirable feature of the invention. In using a spring means of this combination type, piston 3 ί will have a position exactly intermediate the length of the glass barrel 10 when the spring is at rest, that is, when in the intermediate position neither compression nor tension forces will be exerted upon the spring seats. It is obvious that when the syringe is used for injecting or aspirating fluids, it will be cocked for operation against the action of the combination spring in the manner described in connection with the use in the syringe of a compression or a tension spring respectively.

The operation of the apparatus shown in Figures 1 to 7 inclusive, is as follows:

When it is desired to use the hypodermic syringe for supplying fluids under pressure for injections, a compression type spring is used and the syringe is assembled as hereinbefore described. The syringe is now cocked by depressing brake control lever 22 by thumb pressure at 23 thus releasing the pressure of brake rod 20 against the piston rod ί S and, as viewed in Figure 2, the piston rod is drawn to the left by means of ring 26 against the tension of the spring 39 while the needle of the syringe is held immersed in the fluid which is to be injected. The thumb pressure is then released and the brake rod 20 holds the piston rod 18 cocked and ready for use. A subsequent depression of thumb piece 23 will of course rotate brake rod 20 permitting piston rod 18 to move to the right under the action of compression spring 39 thus injecting the fluid as desired. Due to the length of the lever arm 22 very sensitive control is provided thus permitting the rate of injection or the amount thereof to be extremely accurately controlled as a slight depression of the lever arm effects a slight decrease in pressure of brake rod 20 against piston rod 18. It is obvious that the injection may be stopped at any time desired and resumed at any subsequent time, and as the tight fit of the piston 31 will prevent any leakage of the fluid no valves are required. Further, since rod 18 is held motionless by the brake, spring pressure is removed from the piston and thus, between injections, no pressure exists within the barrel of the syringe which might cause leakage past the piston.

When the syringe is used for aspirating fluid, a short tension spring (Figure 7a) is provided and in its initial released position the piston rod 18 and handle 26 (as viewed in Figure 2) will be positioned to the left as previously described, with the piston 31 also at the left portion of the barrel. The syringe is now cocked by depressing thumb portion 23 so as to release brake rod 20 and permit piston rod 18 to be moved freely toward the right against the tension of the spring, and when the piston 31 reaches a position corresponding to the position shown in Figure 2, thumb pressure on member 23 is released and the brake rod 28 will lock the piston rod in this position. The needle is now inserted in a vein, etc., from which fluid is to be aspirated and upon the release, or partial release, of the brake by thumb pressure upon the member 23, the piston 31 due to the tension of the spring, will move to the left to aspirate or draw in by suction the desired fluid.

It is now apparent that I have provided a hypodermic syringe in which the piston is spring actuated to discharge or aspirate any desired fluid and which has a novel control means which will regulate with great accuracy the speed, or pressure with which the automatic injecting or aspirating action takes place. This novel control means or braking mechanism is simple, rugged and fool-proof in its construction and permits, due to the length of its control arm 22, minute graduations of pressure by brake rod 20 upon the piston rod 18 which is invaluable in the type of work for which syringes of this nature are used.

It is well known that movement of the syringe axially in either direction during an injection, etc., generally results in the displacement of the needle thereof or in pain and discomfort to the patient being treated. An important feature of this invention resides in the fact that the sensitive braking mechanism provided can have no tendency to move the syringe in an axial direction as a result of the operation thereof. This important advantage is obtained by providing that pressure on the member 23 must be exerted in a direction transverse to the axis of the syringe, thus obviating any possibility that displacement of the needle can occur thru any fault but that of the operator of the syringe.

In Figures 8 and 9, I have shown a modification of the braking mechanism previously described. In this showing I have provided the metallic cap 16 with two brake rods 44 and 45 which are adapted to have a braking action against piston rod &lt;3. These brake reds 44 and are identical with either structure of brake rod 23 as described and result in a greater braking action on the piston rod 18 and serve to increase the life of the brake rods 44 and 45. The control lever 22 is provided at its rigid connection with brake rod 44 with a gear segment which is integral with lever 22, and the teeth of gear segment 46 mesh with the teeth of a similar gear segment 47 rigidly mounted on the brake rod 45. It will be apparent that pressure on the member 23 of control lever 22 against the action of a spring 48 mounted on cap 16, will cause the brake rod 44 and accordingly brake rod 45 to pivot in cap member 16 to release the brake pressure exerted by both brake rods on piston red 18. It is obvious that the advantages secured by the braking mechanism previously described apply doubly so in connection with this modification,, the braking action being equally and oppositely applied against opposite sides of the rod 29.

In Figures 10, 11 and 12, I have shown an additional modification of the invention. The threaded barrel 40 has formed integral therewith a hollow spindle or chuck 43 having a split tapered end so as to form a plurality of resilient jaws 5S. The cap member 16, as clearly shown in Figure 12, has formed therein a flared opening 5! adapted to cooperate with the jaws 56 of the chuck 4S. When the cap 16 is rotated in a clockwise direction with respect to sleeve 46, the jaws 58 will move into the opening 5! and will be urged by the sides of opening 51 against the piston rod 18 to grip the same and accordingly furnish a. very positive braking action, thereon. In order that relative rotation of cap 16 with respect to threaded sleeve 46 may be more easily

2,309,502 effected to result in a braking action on the piston rod IS, an arm 53 is suitably secured to cap 16 and a second aim 54 is suitably secured to sleeve member S3. A compression spring 55 is suitably secured to and mounted between the arms 53 and 54. It will at once become obvious that while the syringe including cylindrical sleeve 40 is being held by one hand and thus prevented from rotation, thumb pressure on the lever 53 against the action of compression spring 55 will effect relative rotation of the cap 16 and sleeve 40 thus backing off cap member 16 with respect to sleeve 40 to diminish the pressure of the sides of the opening 51 on the jaws 50, thereby diminishing the braking grip of the jaws and permitting brake rod 13 to slide therethrough under the action of spring 39. It will be noted that this modification also includes the advantages hereinbefore described and especially the feature mentioned of a control lever having a long moment arm and upon which a pressure which is transverse to the axis Gf the syringe is exerted to effect the release of the chuck or brake means.

An additional modification of the invention is disclosed in Figure 13 which is similar in most respects to the modification shown in Figures 10 to 12 with the exception that a double chuck 57 is provided within the chamber formed by the sides of flared opening 51 in the cap 16 and by the sides of a similar opening 53 in sleeve 43, and the chuck cooperates therewith so that upon relative rotation of the cap 16 and the sleeve 43 in a clockwise direction (if cap 16 is provided with right hand screw-threads) a double gripping or braking effect on the piston rod 18 is effected by jaws 50 of the chuck 57 due to the pressure thereon by cap 16 and sleeve ¢0.

A further modification of the invention is disclosed in Figures 14, 15 and 16. In this showing, the cap IG has provided therein, in addition to its centrally located opening 17, an opening through which a small shaft 61 projects for a purpose to be described. Cylindrical sleeve member 40 has an irregularly shaped opening 02 provided in its end (Figure 16/ this opening being closed by the cap 16 (Figure 14). Two brake members 63 and 64 are pivotally connected to each other and to the cap 16 as at 65 and are so shaped as to fit snugly about piston rod 18. The upper ends of the members 63 and 64 are resiliency urged togethei^- by means of a tension spring 65. Mounted on shaft 61 is an eccentric 67 which, in the position shown in Figure 16, is in its brake releasing position, that is, is forcing the members 63 and 64 apart against the action of spring 66 and away from piston rod 18. A brake controlling lever 68 having a thumb portion 63 is rigidly secured to the other end of shaft 61 and is strongly urged to a full braking position by a leaf spring 70 mounted on the sleeve 49.

It is apparent that thumb pressure at 69 on the control lever 63 against the action of spring 78 will cause clockwise rotation of the shaft 61 and the eccentric 61 to force brake members 63 and away from piston rod 13 against the action of spring 53 as shown in Figure 16. It will again be noted that all the advantages hereinbefore described and relating to the control means will also apply to the present modification, the pressure exerted on 69 to effect release of the brake members 63 and 64 also being in a direction transverse to the axis of the syringe.

Another modification of the invention is disclosed in Figures 17 and 18. In this showing the

F-c.

GO opening 17 through the cap 16 is flattened on one side as at 71, the cap 16 being screw-threaded on sleeve 40 and having its opening 17 aligned with the opening through the sleeve. Piston rod 18 is provided with a flat side as at 72 and at spaced intervals throughout its length with annular notches 73 extending thereabout except on the flattened portion 72. The usual spring 39 is connected. to the piston rod 18 as at 74 and to the inner face of sleeve 40 as at 75.

It is obvious that if the piston rod 18 is to move axially through cap 16 and sleeve 48 its fiat side must be turned so as to be aligned with the flat side 71 of the cap plate 16. Thus if the Dshaped piston rod 18 is turned so as to be aligned with the D-shaped opening 17 of cap 16 the piston rod 18 may then be drawn to the left as seen in Figure 17 against the action of spring 39 so as to cock the springs, the cocked position being retained by rotating rod 18 out of alignment with the D-shaper opening of cap 16 so that the sides of any notch 73 will abut the fiat side 71 of opening 17. The position in which the Dshaped piston rod is out of alignment with the D-shaped opening 17 of cap 16 is the at rest” position of the spring with respect to rotary motion between the piston rod 18 and the sleeve 40. It will thus be obvious that rotation of the rod 13 to alignment with opening 17 will place the spring 38 under torsion so that upon the sliding of the piston rod 13 through cap IS and sleeve 40 and the arrival of the next succeeding notch at the opening 17 of cap 1S, tiffs torsional force will act to rotate the piston rod (8 back to its “at rest” position at which time the sides of the notches 73 will abut the flat side . 71 of cap plate 16 to prevent further axial movement of the piston rod.

It will be obvious that in the modification just described an extremely simple and efficient automatic syringe is provided for injecting or aspirating fluid in predetermined amounts, the amount of fluid to be injected or aspirated being determined by the spacing of the annular notches formed in the piston rod 18 and by the size of the syringe barrel used. If desired the cap 16 may be arranged to rotate against suitable spring pressure with respect to sleeve 40 thus eliminating the need for rotating piston rod 18, the action of the several parts with respect to each other effecting the same braking action as just described.

Anothei’ modification of the invention is disclosed in Figures 19, 20, 21, 22 and 23. In this modification the piston rod 18 is provided on its lower surface with teeth 77 and 78 of different lengths for a purpose to be described, these teeth being formed by notches or serrations to a predetermined depth. In milling or machining the projecting teeth are cut to specific heights with the exception of every fourth tooth which is left of greater height for a purpose to be described.

The sleeve 40 (Figure 21) is provided with an axially extending vertical slot 70 in its upper surface in which a brake lever 80 is mounted for oscillation by means of pin 81. The lower end of brake lever 80 is provided with an opening 83 extending therethrough and with an arcuate brake surface 82 adapted to bear on piston rod 18. Suitable resilient means such as a leaf spring 84 is secured to sleeve 40 and has one end arranged to urge brake lever 80 upwardly thus forcing brake surface 82 downwardly against piston rod 18 to effect a braking action thereon. It will be noted that the brake lever as constructed and

5,309,503 arranged has a long moment arm and consequently provides highly sensitive operation when releasing the pressure of brake surface 82 from piston rod 18 by manually exerting pressure on the upper end of the brake lever 81 in a direction , transverse to the axis of the syringe.

In order to provide an even more sensitive brake controlling means, the upper end of brake lever 89 may have suitably mounted therein a screw adjustment consisting of a screw 8S mount- ₁ed in a screw threaded opening SS in the upper side of sleeve 48. Screw 85 is provided with an enlarged and knurled head 81 and it is apparent that by rotating knurled head 87 in either direction minute graduations of the braking effect by _χbraking- surface 82 on piston rod 18 may be obtained. The provision of the screw adjustment in brake lever 81 prevents normal manual depression thereof to effect a release of the brake.

The sleeve 40 is provided with a transverse slot _Qor opening 87' extending therethrough (Figures “ 19, 21 and 22) in which is mounted a D-shaped plate 88 having lugs 89 and 98 for a purpose to be described. This plate 88 is pivotally connected at S ί to sleeve 40 and is provided with a rectangular opening 92 in order that piston rod 18 may pass freely therethrough. As seen in Figure 19 the other end of leaf spring 84 projects through the opening 83 in the lower end of brake lever 89 and bears upwardly against the lower edge of upper cross member 93 of D-shaped plate 88. It is apparent that the lower cross arm is urged upwardly against or between the teeth 77 and 78 by the pressure of leaf spring 84 against cross member 93 to thus prevent axial movement of piston rod 18, In order that the piston rod 18 may be prevented from rotating under the influence of the compression spring 39, a spline groove is provided in a side face of the rod. A screw 9S extends diametrically through the sleeve 40 and into the spline groove S5, permitting axial movement but not rotation of piston rod 18.

A longitudinal opening 1'9-8 (Figure 22) extending into the slot or opening 8 7' is drilled in the sleeve 40, terminating at its other end in a radial opening 131 in the side of the sleeve &lt;18. Mounted for sliding movement in this opening ί 88 is a pin 102 having an operating lug or handle i 03. Suitable resilient means may be connected to the lug 193 of pin 102 to urge it into the opening 87' adjacent the lugs 89 and 98 on plate 88.

The pin 182 acts as a stop for the lugs §9, 23 and 94' on plate 88 in its motion about its pivot 91 and may be retracted by means of lug 183 (Figure 22) so as to permit the lugs on plate 88 to move freely. Referring to Figure 21, it will be seen that pin 182 abuts the top surface of lug 90 on plate 88 to hold lower cross arm 94 locked in a position below the short teeth 77 but not below the long teeth 78 so that the piston rod 18 is free to move axially until anyone of the long teeth 73 abuts the lower cross arm 94. By depressing the lug 185, plate 88 will be pivoted downwardly until pin 102 abuts the lower surface of lug 89 thus moving lower cross arm 94 beneath or out of the way of the long teeth 78 so as to again permit axial movement of the piston rod 18. As plate 88 is urged upwardly by leaf spring 84 upon release of pressure on lug 185 it will be seen that pin 182 will resume its former position abutting the upper surface of the lug 99 on plate 88 so that cross arm 94 will again be in the line of and act as a stop for the next succeeding long tooth 78.

If desired, the pin 162- can be retracted and after fully depressing lug 155, the pin 162 may be released to now be in a position abutting the upper side of lug 89 on plate 88. This position will retain the lower cross arm @4 of D-shaped . plate 88 below the line of the long teeth 78 and ^J thus permit the operator to entirely control the injection or aspiration of fluid by means of the brake lever 88 alone.

When it is desired to inject or aspirate fluids in θ an amount represented by the distance between the short teeth 77 or between a short tooth 77 and the next adjacent long tooth 78, the pin 192 will be placed in a position to abut the upper surface of the lug 94' formed by the continuation _r of the lower cross arm 94. In this position, the ⁰ lower cross arm 94 abuts the lower surface of the piston rod 18, preventing motion thereof, but when lug 185 is depressed until pin 102 abuts the lower surface of lug 90, the piston rod i 8 is free to move a distance of one small tooth 77 as the ⁰ lower cross arm 94 also moves downwardly with lug 155 to clear a lower tooth 77, but is urged upwardly again in the next space adjoining that tooth by action of the leaf spring 84 on the lower surface of upper cross arm 93 when lug 105 is ⁵ released.

It is obvious that any desired graduations or variations of amounts of fluid represented by the spacing of the teeth 77 and 78 could be arranged as desired. In the drawings, for purposes of ⁰ illustration, every fourth tooth is shown as a long tooth 78 so that as desired, a cubic centimeter of fluid could be injected or aspirated by permitting the piston rod to move the distance „ between two long teeth 78, or only a quarter cubic ³ centimeter could be delivered by permitting the piston rod to move only the distance between two small teeth 77.

When it is desired to operate the modification 0 just described, the syringe is cocked and filled with fluid as described. If it is desired to deliver, for example, a cubic centimeter of fluid the pin 182 is placed between the notches 89 and 98 as shown in Figure 21. The operator now de_ presses lug 105 permitting the large tooth 78 ^J which is abutting lower cross arm 94 to pass thereover as the piston rod moves axially under the influence of the spring 39, the brake lever 30 having been depressed manually or released by ₀ rotation of the knurled screwhead 85. Lug iOS is now released and leaf spring 84 urges the plate 88 upwardly so that the upper surface of lug 90 now abuts the pin 102 thus placing the lower cross arm 94 in the path of the next large tooth _g 78 to act as a stop therefor.

When it is desired to deliver only one-quarter of a cubic centimeter of fluid the pin 102 is inserted between lugs 90 and 94' and operation is effected in the manner described above. As hereinbefore mentioned, it is possible to entirely elim^u inate -the automatic stop action of plate 88 by placing the pin 182 so as to abut the upper surface of lug 39 which will hold the lower cross arm 94 of the stop plate 88 completely out of ₅ engagement with any of the teeth on the lower surface of the piston rod 18. It is obvious that the delivery of the predetermined amounts of fluid may be continued until the supply of fluid contained in the syringe is exhausted. Further the 0 advantages of a long moment arm resulting in an extremely sensitive brake control is embodied in the present modification as well as in those modifications previously described.

The provision of the adjusting screw 85 on brake lever 80 makes possible a very accurate con2,309,502 trol of fluid delivery so that, it is possible to deliver definite amounts of fluid per unit of time successively until the fluid capacity of the barrel is exhausted, the piston stopping automatically upon delivery of each predetermined amount.

It will now be seen that in the description of the invention and its several modifications I have disclosed a novel and efficient brake controlled automatic hypodermic syringe for use in the injection or aspiration of fluids. The provision in this brake control means of a control lever having a substantial moment arm which is adapted to be actuated by manual pressure in a direction transverse to the axis of the syringe, results in a control means unexcelled with respect to its accuracy in use.

Further, the control means provided assures the definite delivery of any desired amount of fluid under the action of the spring due to the sensitivity of the control lever as combined with the positive braking elements of the invention. The provision of the syringe having a brake release means effected by transverse pressure which has no tendency to displace the needle of the hypodermic syringe during actuation thereof is of extreme importance in the medical and allied professions.

The combination of the control means described with the automatic stop means provided to arrest the motion of the piston upon the delivery of predetermined amounts of fluid is an important contribution to the art. The operator of a syringe constructed in accordance with the principles set forth, may inject or aspirate fluids in predetermined amounts or at will successively or continuously, and with extreme accuracy and great facility.

Where the term “barrel assembly” is employed in the claims it is understood that this expression is not limited to the barrel per se but is intended to define those structural elements necessary to the completion of the assembly for holding fluid. For example, the expression “barrel assembly,” as applied to the form of the invention in Figures 1 and 2, would include the barrel 10, sleeve 41, tube 40, and cap (6.

It is to be understood that the forms of my invention herewith shown and described are to be taken as preferred examples of the same and that various changes in the shape, size and arrangement of parts may be resorted to without departing from the spirit of the invention or the scope of the subjoined claims.