US2816543A - Hypodermic injector - Google Patents

Description

Dec-17, 1957 A. vENDlTTY ET AL 2,816,543

HYPODERMIC INJECTOR 2 Sheets-Sheet 1 AH/log qnd Jo/m Sez/gerer rloeNEVs Y HYPODERMIC INJECTOR Anthony Venditty, Detroit, and John 0. Scherer, Grosse Pointe, Mich., assignors to R. P. Scherer Corporation, Detroit, Mich., a corporation of Michigan Application July 12, 1954, Serial No. 442,613

7 Claims. (Cl. 12S-173) This invention relates to av needleless hypodermic injector capable of injecting a fine stream or jet of liquid.

medicament at high velocity through the epidermis. More particularly, the invention constitutes an improvement over the injector described in the copending application of Robert P. Scherer, Serial No. 94,579, led September 28, 1953, now Patent No. 2,704,543. The instrument described in that application is adapted to discharge liquid medicament from an ampule at two diierent pressure stages, an initial high pressure stage for causing the jet stream to distend 'the skin and penetrate to a predetermined depth, followed by a reduced pressure stage'for completing transfer of the liquid from the ampule through the opening produced during the high pressure stage. The two pressure stages are producedby aspring-actuated dual plunger assembly comprising a primary plunger or small diameter slidably mounted within' a secondary plunger having a diameter equal to that of theilexible rubber-like follower or stopper withinthebore of the ampule. The follower is cup-shaped and is adapted to expel liquid through a minute orifice in thev end of the ampule as it advances down the bore. `As thepower spring expands, the primary plunger exerts a force against the central portion of the bottom of the follower to distend that portion a short distance and simultaneously eject a small amount of liquid from the oriice in the ampule under high pressure. The volume of liquidejectedduring the tirst or high-pressure stage determines the depth of penetration of the stream below the surface. After the primary plunger has traveled to the end of its stroke, which is relatively short, the secondary plunger engages the entire area of the bottom of the follower and moves the follower down the bore of the ampule to complete the injection at reduced pressure. The reduction in pressure, of course, is due to an increase in the area-engaged by the plunger. The pressure during the second stage is just enough to feed the liquid through the channel made during the irst pressure stage. Y Y

Since the primary plunger only distends the follower and does not move it, the follower does not travel down the bore of the ampule until engaged by the secondary plunger. Therefore, part of the energy supplied tothe plunger to generate pressure is momentarily diverted in overcoming starting friction in advancing the follower. The result is that the pressure of the liquidV jet does not drop directly from lirst stage to second stage and then level oil, but dips below the normal second stage pressure at the point where the starting friction must beovercome, and thereafter increases to the normal second stage pressure. This reduction in pressure and `subsequent sudden increase in pressure due to overcoming `the friction of the follower in the ampule is highly undesirable because in some patients'the resultingfswurgeY causes pain. It is one ofthe objects lof the present iiiveritionto provide an instrument for Vtwo-stage pressure injection in which the pressure is reduced to th'e second Vstage 'without l theunde'sirable momentary drop' just vdescribed.V` i

vAnother object is'to provide 'two pressure stages through nited States Patent O 2,816,543 Patented Dec. 17, 1957 a single plunger. These and other objects will become apparent from the following description and the accompanying drawing, in which:

Figure 1 is a longitudinal sectional view through an instrument illustrating the invention;

Figure 2 is an enlarged longitudinal sectional view of the lower portion of the instrument of Figure l showing the position of the parts of the plunger assembly at the beginning of the low pressure portion of the plunger stroke;

Figure 3 is a transverse section along the line 3-3 of Figure 1;

Figure 4 is a longitudinal sectional view of the lower portion of the instrument shown in Figure 1 illustrating a modification of the plunger assembly;

Figure 5 is a similar enlarged view of the lower portion of the instrument shown in Figure 1 illustrating another modification of the plunger assembly; and

Figure 6 is a transverse section along the line 6 6 of Figure 5.

Broadly, this invention consists in the provision of a single plunger advanced by forces of two different magnitudes to produce the two pressure stages desired. Since pressure equals force divided by area, it is apparent that pressure may be increased either by increasing the force or decreasing the area. In the construction of the present invention the force ou the ampule follower may be varied to produce the change in pressure. The change in force is accomplished by mechanically multiplying the force applied to the plunger during the first part of the stroke and then transmitting the force of the same magnitude directly to the plunger, without the aid of the multiplier, for the remainder of the stroke. By this means the pressure resulting from the multiplied force is high, whereas that resulting from direct transmission is relatively low. The ratio of the pressures may be controlled by changing the proportions of the force-multiplying device.

For a detailed description of the invention, reference is now made to the drawing in which the numeral 10 designates a body housing most of the mechanism of the injector. A dosage sleeve 12 is screwed onto the threaded lower or ampule-containing end of the injector, and a winding sleeve 14 is rotatable on the upper end thereof. The sleeve 14 has an inturned flange 16 coacting with an annular ridge or ring 18 on the body 10 to prevent longitudinal movement in one direction relative to the body. A latch housing 20 is screwed into the rear or upper end of the winding sleeve 14 with a thrust bearing assembly 22 interposed between the body and the latch housing.

A release button cap 24 is threaded on the latch housing 20 and the entire assembly of the winding sleeve 14, latch housing 20 and cap 24 is held in assembled relation by a set screw 26 engaging all three parts and sealed in place, as best shown in Figure 3.

The dosage sleeve 12 has threaded on its lower end an ampule holder 30 adapted to -receive an ampule 31 having medicament 32 therein and a flexible cup-like follower 33, preferably made from an oil-resistant rubber, such as polychloroprene, Buna N, or the like. The ampule is providedV with a reduced discharge nozzle 34 perforated by a minute discharge orice 35. The ampule holder is covered by a resilient nose36 which may also be made from polychloroprene rubber or the like.

The internal mechanism of the injector construction shown in Figure 1 includes the novel plunger assembly of the Ainvention, which multiplies vthe force transmitted to the plunger 40,* which is adapted to advance the ampule follower 33 within/the ampule 31. The assembly consists of a plunger 40 having an integral head 41, the head recess 42 provided within the disc-like bearing member or cam carrier 43, and a piston-like cam actuator 52. Cam carrier 43 is adapted to slide axially within the dosage sleeve 12. To permit assembly of the plunger 40 with the cam carrier 43, three flange-like ears 44 extending outwardly .from the head 41 and equally spaced about the circumference thereof serve to lock the head 41 beneath the llange 45 which extends radially into the recess 42 of the `cam carrier 43. Flange 45 has three circumferentially-spaced slots which cooperate with the ears 44 in the manner of a bayonet connection to permit the head 41 to be inserted in the recess 42 when the ears and slots are aligned. The head 41 is then turned about 60 so that the ears 44 are located beneath the ange l45 to prevent complete separation of the plunger 40 .from the calm carrier 43. Obviously, the number of ears and corresponding slots is not critical and any suitable number may be employed.

To facilitate movement of the plunger 40 with respect to the cam lcarrier 43, a cam actuator 52 is adapted to slide axially within a blind central opening 55 provided in the plunger. Shaft A53 comprising the lower end of actuator 52 is of reduced diameter for this purpose. To move the plunger 40 under multiplied force, three cams 47 of triangular wedge-shaped cross section are slidably seated within radial guide slots 48 cut in the top surface of the head 41 and equally spaced circumferentially. The right side of theisection shown in Figure l is taken through slot 48. The number of cams and corresponding slots,

of course, may vary, but we have found 'three to be suitable for the purpose. The sides of the triangular cams 47 are flat, with the edges rounded where the sides meet each other. The cam carrier 43 has a central opening t) and three radial slots 49 cut in the bottom of the recess 42. Slots 49 are aligned radially with slots 48 and cooperate therewith to guide cams 47. The slots 49 slope centrally toward the top surface 51 of the cam carrier 43 and join with the opening 50. The slope of each slot 49 is equal to the angle 59 between the top and bottom sides of the cams 47 so that the bottom .sides of each cam will lie flat against the bottom of the corresponding slot 48 in the head 41 while the top sides of each cam lie Hat against the .sloping surface 49 in the cam carrier 43. When the head 41 is in the position shown in Figure l with its top surface in contact with the bottom of the recess 42, the short sides or ends of the cams 47 project into the opening 50 a slight distance. These ends are adapted to lie against corresponding wedge slots 54 provided therefore in the vcam actuator 52. The flat ends of cams '47 lie .insubstantially complete contact with the wedge slots 54, as .shown in .Figure 1. As indicated, the cam actuator has a lower end 53 o'f reduced diameter which slides within the blind .axial bore 55 of the plunger 40. A -coil spring 58 is .provided in the bottom of the bore 55 to return the cam actuator 52 to its original position when the injector is reset. The upper end of the actuator slides within the opening 50 provided therefor in the cam carrier. When 'the actuator 52 moves downwardly, the wedges or cams 47 are forced outwardly by the wedge slots S4, to Aforce the piston downwardly'.

By changing the angle 59 which makes the wedge steeper or shallower, the ratio of the force applied by the cam actuator 52 to the force applied by the plunger 40 may be varied. The smaller the angle, the larger the mechanical advantage or force transmitted to plunger 40.

Force applied to the end of the cam actuator -52 by the screw 62, as explained herenbelow, serves to 'slide cams 47 radially within guide slots 48 and 49 as'the wedge slots 54 of the cam actuator bring 'pressure 'to bear against the cams 47, thus causing the head 41 to move away from the cam carrier 43.

The flanged Vend 37 of the plunger 40 slides within the bore of the ampule 31 to engage the follower '33 for ejecting liquid from the ampule. A rubber washer 38 is provided in the bottom rof the cavity of the sleeve 12 to pro- 4 vide a resilient cushion for the plunger assembly when it is operated without an ampule in place. When discharged with an ampule in place the plunger will not descend this far.

The mechanism for propelling the assembly comprises a nut 60, a screw 62 and a plurality of power springs 64 disposed around the screw 62 within the body 10. The nut is sleeve-like in character and has a clover leaf shaped head 66 provided with spring seats for the springs 64, which springs at their opposite ends seat against a partition 68 of the body 10. The nut 60 has threads 61 at its upper end which cooperate with the threads of the screw 62. The nut 60 will not rotate with respect to the body 10, but is adapted to move longitudinally therein. The upper end of the screw as shown in Figure 1 is provided with a head 70 providing a latching shoulder 71. The screw head 70 terminates in a bifurcated portion which results in a pair of spaced blades 72, the head with 'its ,blades being slidable in a square opening 21 in the latch housing 20. As shown in Figure 3, the latch housing is provided with a cross slot 23 in which the latch 25 is lpivotally mounted. For this purpose a pivot pin 27 is press-tted in the latch and has its ends rotatable in the latch housing. The latch 25 substantially spans the width of the slot 23 and the space between the blades 72 of the screw and is of the shape shown in Figure 1, having a latching shoulder and a spring socket 76. A latching spring 77 has one end seated in the socket and its other end seated in an opposing socket 78 in the latch housing for tending to :rotate the latch counterclockwise.

Slildably mounted in the release button cap 24 is a release button 80 having a cross bar 82 attached thereto and slidable in the slot 23 of the latch housing 20 and the space between the blades 72 of the screw 62 back of the latch 25. When the button 80 is depressed, the latch v25 is rocked against the bias of the spring 77. A latch roll 83, rotatably mounted in the latch housing, prevents the screw 62 which is biased upwardly from moving until the latch 25 is released, thus permitting the latch roll 83 .to'rotate out from under the shoulder 71.

In operation, the winding sleeve 14 is rotated causing the 'screw -62 (latched against axial movement) to turn and lift the nut 60 to compress the springs 64 seated in 'the head '66. Then, the ampule 31 is placed within the holder 30 and secrewed onto the end of the injector. The parts are then in the position shown in Figure 1, the ampule follower 33 being yin contact with end 37 of plunger-40..

Release is accomplished by depressing the button 80. 'The latch 25 is rocked against bias of spring 77 which permits the latch roll 83 to rotate out from under the shoulder 71. Upon releasing the latch, the springs 64 immediately expand and screw 62 is carried downwardly bythe nut 60. The lower end of the screw 62 is pointed and seats in a conical depression in the end of the cam actuator 52. As it moves downwardly the cam actuator forces lthe cams 47 outwardly within the radial guide slots 48 and 49. Since the cam carrier 43 is supported by the posts r and cannot n'se within the instrument, the head 41 moves away from the cam carrier 43 as the cams move outwardly to cause the piston 40 to move downwardly and transmit the force from the screw 62, multiplied through the cams 47, to the follower 33. The multiplied forces imparted to the piston 40 causes liquid 32 to be `ejectedfrom the ampule at high pressure. The magnitude of the force exerted by the plunger 40 may be increased or decreased 'as indicated previously by changing the angle 59 lof the cams 47 to vary the mechanical advantage provided thereby.

The plunger 40 advances under this multiplied force a distance determined by the mechanical advantage provided by the Wedges. For example if the mechanical advantage is 3 to l this distance will be equal to l/a the distance travelled by the actuator 52. When `the wedges have been `fully extended into the slots 48 and 49 in which they slide, the liangev 66 of nut'60 engages thiesurfacesl -of the cam carrier 43, and the plunger 'assembly then moves as a unit to expel the remaining liquid 32 from the ampule 31 under reduced pressure. At the instant the nut makes contact with surface S1 the parts are in the relative positions substantially as shown in Figure 2. Resetting is accomplished as with the conventional 'insrtument The screw is turned counterclockwise to latch it and then in a clockwise direction to compress the springs. The ampule is then replaced and the instrument is ready for another injection.

A modification of the force-multiplying means shown in Figures 1 and 2 is illustrated in Figure 4. The three triangular liat-sided cams or wedges 47 have been replaced with three balls or spheres 69 with mating slots 48a and 49a. Apart from this replacement, the construction of the plunger assemblies are exactly the same. The balls are large enough so that they project into the central opening 50 in the cam carrier 43 and bear against the' wedge surfaces 54a of the cam actuator 52. The balls 69 will roll and/ or slide up the slots 49a and 48a in the cam carrier 43 and the plunger head 41, respectively, as the actuator 52 moves downwardly. The operation of this unit is the same as that described in connection with Figures l and 2.

A further modification of the invention is illustrated in Figures and 6. The force-multiplying means illustrated here employs a series of pie-shaped levers in place of wedges or cams. The force is transmitted from the screw 62 to the plunger 100 through ve pie-shaped levers 104 which in assembled relation comprise a disc. The plunger 100, shown in Figure 5, has an integral disc-like head 102 which slides axially within the dosage sleeve 12 of the instrument. The levers 104 which are pie-shaped in plan View, are arcuate in cross section, as shown in Figure 5. The levers are arranged so that the outer arcuate portions 105 are contiguous and lit inside the circular dosage sleeve 12. The bottom arcuate surface 109 of each lever is adapted to bear on the at upper surface 101 of the plunger head 102. The outer extremities 110 of each lever 104 bear against the lower ends of body posts 90a, which serve as stops. The pointed inner extremities 108 of the levers 104 bear against the end of the screw 62a. As shown in Figures 5 and 6, when the inner extremities 108 are in raised position (plunger 100 being retracted), the sides 107 of the levers separate slightly, the separating distance decreasing toward the circumference or peripheral arcuate edges 105. The number of levers 104 is not critical, any convenient number being satisfactory.

vIn operation, the descending screw 62 strikes the inner extremities 108 of the levers causing the levers to rock radially toward the center of the plunger head to push the plunger 100 downwardly with multiplied force by reason of the mechanical advantage provided through the levers. Because the bottom bearing surface 109 of each lever is arcuate in shape, the fulcrum of the lever advances progressively radially inwardly from the extremities 110, which are prevented from moving upwardly by the posts 90a. When the inner extremities 108 of the levers are depressed against the surface 101 to the point where the projection on flange 66 of the nut 60 engages the levers, the plunger and the levers advance together as a unit. While the force from the screw 62 is applied to the plunger 100 through the levers, the pressure at which the uid is expelled from the ampule is relatively high. When the levers have collapsed to the point where nut 60 makes contact with the top surface of levers 104, the force is then applied to the plunger without the mechanical advantage and the pressure is consequently reduced.

From the foregoing description it will become clear that various modifications in the force-multiplying plunger assembly can be made without departing from the spirit of this invention. The invention is not intended to be' 6 limited to the specific constructions illustrated other than as necessitated by the scope of the appended claims.

We claim as our invention:

1. In a hypodermic injector, an assembly comprising an elongated body, an ampule holder detachably connected to the end thereof and adapted to hold an oriced ampule, a single plunger slidably mounted within said body and adapted for engaging and propelling a follower within said ampule to discharge liquid contents through the orifice, said plunger having a head integral therewith and a blind axial bore, a disc-like cam carrier slidably mounted within said body and having a recess in `one face thereof terminating in a central opening aligned with said axial bore, said head being reciprocatively mounted within said recess, force-multiplying cams interposed between the bottom of said recess and said head and adapted to move radially to force said head away from said cam carrier, a cam actuator slidably mounted within said central opening and said bore of the plunger, and power means within said body adapted to engage said cam actuator and said cam carrier sequentially to move said plunger through the action of said cams with multiplied force, and to advance the plunger and cam carrier as a unit with a force of normal magnitude, said power means including means for storing energy therein and means for suddenly releasing the energy thus stored.

2. The hypodermic injector of claim 1 in which the force-multiplying cams are wedge shaped.

3. The hypodermic injector of claim 1 in which the force-multiplying cams are spherical.

4. ln a hypodermic injector, an assembly comprising an elongated body, an ampule holder detachably connected to the end thereof and adapted to hold an oriced arnpule, a single plunger slidably mounted within said body and adapted for engaging and propelling a follower within said ampule to discharge liquid contents through the orifice, said plunger having a head integral therewith, force-multiplying levers of arcuate cross section supported by said head, the outer extremities of said levers bearing against stops to prevent movement away from said head, said arcuate levers being adapted to rock radially against said head, and power means within said body adapted to engage the inner extremities of said arcuate levers to move said plunger through the rocking action of said levers with multiplied force, and then to engage the depressed levers in an area outside said inner extremities to advance directly the plunger and the levers as a unit with a force of normal magnitude, said power means including means for storing energy therein and means for suddenly releasing the energy thus stored.

5. In a hypodermic injector, an assembly comprising an elongated body, an ampule holder detachably connected to one end thereof and adapted to hold an oriced ampule, a single plunger slidably mounted within said body and adapted for engaging and propelling a follower within the bore of said ampule to discharge liquid con tents through the orifice, power means for propelling said plunger including means for storing the driving energy therein, means for suddenly releasing the energy thus stored to perform propulsion of the plunger and follower, and force-multiplying means between said power means and said plunger and adapted to increase the force applied to the plunger during the first part of its stroke.

6. In a hypodermic injector, an assembly comprising an elongated body, a cylindrical chamber in one end thereof having a bore terminating in a minute orifice and adapted to hold liquid to be discharged from the injector, a follower within the bore of said chamber, a single plunger slidably mounted within said body and adapted for engaging and propelling a follower within the bore of said chamber to discharge the liquid through the orifice, power means for propelling said plunger including means for storing the driving energy therein,

means for suddenly releasing the energy thus stored vto perform propulsion of the plunger and follower, and force-multiplying means between said power means and said plunger and adapted to increase lthe force applied to the plunger during the rst part of its stroke.

7. In a hypodermic injector, an assembly comprising an elongated body, an ampule holder detachably connected to the end thereof and adapted to hold an oriced ampule, a single plunger slidably mounted within said body and adapted for engaging and propelling a follower l within said ampule to discharge liquid contents through the orifice, said plunger having a head integral therewith, a disc-like cam carrier slidably mounted within said body adjacent said head, force-multiplying cams interposed hetweensad cam ycarrier and said head adapted 'to move radiallyto lforce said head away from said cam carrier, a cam actuator for moving said cams and power means within said body adapted 'to engage said cam actuator and said cam earrier sequentially to move said plunger through the actionof said cams with multiplied force, and to advance fthe plunger and cam carrier as a unit with aforce o'f normal magnitude, said power means including means for storing energy therein and means for sud denly releasing the energy thus stored.

No references cited.

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