US2762370A - Hypodermic injector - Google Patents

Description

A. vENDlT-ry v 2,762,370 HYPODERMIC INJEcToR 2 Shee'ts-Sheet 1 sept. 11, 1956 Filed Sept. 7, 1954 Sept 11, 195-6 A. vENDlTTY Y 2,762,370

HYPODERMIC INJECTOR Filed Sept. '7, 1954 2 Sheets-Sheet 2 INVENTOR.

@B2i/why Vendi/[y HYPODERMIC hameren Anthony Venditty, Detroit, Mich., assi'gnor to The R. P. 'Scherer Corporation, Detroit, Mich., a corporation of Michigan Application September 7, 1954, Serial No.74545`4'47 6 Claims. (Qi. 12e-F173) vThis invention relates to an improved needleless-hypcidermic injector of the type shown and described in the dpending application of R. P. Scherer, Serial-No. 170,101, .filed June 24, 1950. Instruments of this kind are adapted to discharge -liquid medicament from an orifced ample in the form of a minute stream or jet at two diiferen'tpressure stages sequentially. The initial high pressure discharge causes the jet stream to distend the skin and force 'the liquid to a predetermined depth beneath the su'rfaee, depending upon `the magnitude of the pressure. AAfter the minute opening in the epidermis has been produced the .pressure of the `stream is immediately reduced toa lower second stage for completing transfer of the remain'- ing-liquid from the ampule.

Y The instrument shown and described in the application above referred to employs five coil springs as' a soure of p ower for driving a dual plunger assembly comprising a .primary plunger 4of small diameter slidably mounted V'With'- inV a secondary plunger having a diameter equal "to lthat of the exible follower or stopper within' the bore of the ampule. The follower is cup-shaped and is adapted to expel-liquid through the minute orifice in the `end of the ampule as -it is vadvanced down the bore :by the plunger. As the power springs expand, the primary plunger exerts a force against the central portion o'f the bottom of the follower to distend that portion a short distance and simultaneously 'eject a small amount of liquid from the' orifice the ampuleunder high pressure. The magnitude of this pressure during the iirst stage determines the depth gaf-penetration -of the jet stream below. the surface. After the primary plunger-hastravelled to the fend of 'its stroke', which yis Yrelatively short, the secondary plunger IVengages the entire area of the bottom of the follower and moves the follower down the bore of the ampule to compiete theinjection at reduced pressure.' The reduction in pressure, ofcourse, -is due to the increase in the area engaged jby the plunger. The pressure during the second stage is ljust suiiicient to f e'ed the liquid through the channel formed during the first pressure stage.

`It has been found that the coil springs employed .inthe injector construction .just described cause the liquid to lbe expelled in surges rather than at substantially uniform pressures.Y Some patients find s uch surges to be a source of p ain. The amount of deviation from the desired .pressure i s not great, but the fluctuations occur very rapidly. Indications are that these undesirable rapid fluctuations pressureare tied in with the natural frequencies `of the springs.Y V Coil` springs made from braided wire and having alow natural frequency have beenfound to reduce the-surge to a minimum with substantially complete climi'- natien of pain to the patient due to rapidly vfluctuatii'ig pressure. However, springs of braided construction 'are expensive and increase substantially the cost of the instrument. I now have found that thev undesirable frequencies which apparently are responsible for the rapid surges in pressure may be sufficiently minimized vor dampened by employing pairs of coil springs having different natural frequencies. By matching dissimilar frequencies, thevibrations causing the pressure deviations may be dampened or canc`elled out. In the construction Iof the instrument in accordance with this invention, therefore, power springs are used in pairs; the total number may range from 6 to l2.

Ahothe'robjectof this invention is to provide aninstrument of the type Vdescribed which is more economical to l.produce vthan those made previously, this object being accomplished by greatly simplifying the construction of the power release mechanism, and thrust bearing between the latch housing and the body. l

A further object is the provision of av novel dual plunger assembly in which the primary plunger is iii'ted to (the power :means land is adjustable with respet to A the fol- 7lower in the ampule. By'adjust'in'g the distance between the primary plunger 'and the follower, the impact force with whichithe plunger strikes the follower mayibevaried, and vthis "in turn results in variation 'in the pressureat which the lliquid is "ejected from' the oric'e inthe ampule. in 'prioriinstrumen'ts capable of injeoting at two 'pressure `stages Ano :p'ryision was-made for 'varying the impact of `primary plunger. l y

Another object is the' provision of a primary plunger which is axially adjustable with respect to the ampulenf'ollower by rotating the fast-lead lifting Esciew in thepower mechanism, r`but which is 'ot in gaitialengag'ment with Said screw. Bi li'finatiagaxial engagement bei 'plunger andthe fast-lead lifting screw; their u1 on' the threads ofthe screw, due to liquid`res1str n the ampule, and the 'friction attendant thereto, Ais e yininatlefd. These and other objects of the invention will appear as' the follo'xving description proceeds.

In the'drawing: l n A Figure l is a longitudinal oross-seetional .through the inst-rumentconstructed in acordanee with the invention; l Y

Figure 2 is a sectional Vview taken along the line 2-'Z `ofliigurel; v l y y. Figure 3 is an elevational view of the mating heads employed for rotationally engaging the screw and the .privmary plunger for adjustment of the latter with respect to the` ampule follower; Y A l l l l Figure '4 is a sectional view `of Vthe upper end ofI the instrument Vshowing the latch wedges in Vretracted position; Figure 5 is a sectional View along the line 5'-5 of Fig'- urel;and I Figure 6 is a longitudinal cross-sectional View of the lower end of the instrument after the nut has engaged the secondary plunger. H

The invention lies in the construction and arrangement of the various elements comprising the injector, particularly the novel latch mechanism and the duel plunger assembly. l Y, ,l y Reference is now made to Figure l of the 'drawings in which vthe numeral 10 designates an elongated body housing most of the mechanism of theinjector. Ay dosage sleeve 12 is screwed onto the threaded lower lor 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 ring or ridge 18 on the body 1,0 to prevent longi tudinal movement in one directionrelative to the body. A combination latch housing and upper bearing sup"n port 2d is screwed into the upper end of the `*winding sleeve i4 with a thrust bearing 22 interposed between the body and the latch housing. Arelease button cap 24, which may be molded from a 'suitable thermoplastic resin', is assembled with the latch housing 20, being held in place by a conventional non-reversible bayonet con# nection. The entire assembly of the winding sleeve 14, latch housing 20 and the cap 24, is adapted. to rotate as a unit since the sleeve 14 and the housing 2l)v vare locked together by a key 25 which lits into matching slots 19, as best shown in Figure l.

The dosage sleeve 12 has threaded on its lower end an ampule holder 4d adapted to receive an ampule 42 containing medicament 44 and having a exible cup-like follower 46 in the upper end thereof. The ampule is pierced with a minute orifice 4S in the lower end thereof. The ampule follower 46 may be made from a resilient plastic material or rubber, preferably an oil resistant rubber such as polychloroprene, Buna N, or the like. Other rubber parts employed in the construction of this instrument should likewise preferably be made from similar oil-resistant stocks.

The dosage sleeve 12 is locked against rotation by means of a latch 15 which tits into grooves 17`spaced circumferentially about the inside surface of the sleeve. By rotating the sleeve 12 liquid medicament 44 may be predischarged The sleeve may be marked externally to indicate the exact volume predischarged when the sleeve is rotated through the arc dened by the successive. grooves 17. This feature is conventional.

The internal mechanism of the instrument includes a Vnovel plunger assembly consisting of a primary plunger 50 having an externally threaded upper end 51 screwed into the nut 70, and a secondary plunger 60 in which the primary plunger 50 is slidably mounted. The threads 57 on the upper end 51 of the plunger 50 are single ,threads as distinguished from double threads which are .employed within the sleeve-like portion of the nut 70 for purposes to be explained presently. The lower end 62 of the secondary plunger 64) is adapted to slide within the ampule 42 to advance the follower 46, while the lower end of the primary plunger 50 is adapted t0 bear against the central portion only of the top of the follower 46. The upper portion of the secondary plunger 60 terminates in an integral circular head 64 adapted to slide axially within the sleeve 12, its upward stroke being limited by the lower end 11 of the body 1t). A washer 66 made from rubbery material is seated in a counterbore in the top surface of the head 6l) to dampen vibrations that might be transmitted through the secondary plunger 60 from the nut 70. A similar rubber-like washer 68 is adhered to the bottom of the sleeve 12 to cushion the ,blow of the head 64 when the instrument is operated without the ampule in place. Washer 66 further serves this purpose.

The means for propelling the primary plunger S comprises coil springs 86, 81 inserted in 'blind axially-extending openings 13 spaced circumferentially within the body 10. Single springs may be employed in each opening 13, but preferably, l use springs in pairs as shown in Figures l and 5, internal spring 81 being of smaller diameter and of opposite helix to external spring 80. Each pair of springs in diametrically opposite openings 13 must generate equal total force to prevent the tend- .ency to cock. It is preferred that the springs in the same opening and in adjacent openings be of different natural frequencies, which tends to cancel out vibrations that result in rapid fluctuations in the pressure of liquid 44 expelled from the ampule. Springs 80 (or springs 81) in diametrically opposite openings need not be of the same natural frequency.

The bottom surfaces of the springs seat in recesses 71 in the surface of the nut 70, and concentric with the openings 13. The tops of the springs seat against the body 10. Pins 71a, fixed at their lower ends to the nut 70, extend upwardly within the openings 13 along the axes thereof and serve to prevent the springs from buckling.

The nut 70 has a long sleeve-like extension 72 projecting upwardly into a central bore 73 in the body 10, and is keyed thereto as indicated at 72a (Figure 5) to prevent rotation. The sleeve 72 is internally threaded with two styles of threads. Approximately the lower onequarter has single threads and the remaining upper portion has double threads. A lifting screw 74 is adapted to. turn within the sleeve 72 for lifting the nut 70 to compress the springs 80, 81 seated therein. The screw 74 has double threads 75 to match those in the upper portion of the sleeve 72. Thus, one revolution of ro tation within the sleeve 72 will cause the screw 74 to travel twice the distance of the single threaded primary plunger 50 when the latter is rotated one revolution within the lower end of thev sleeve 72. The screw 74 serves the dual purpose of lifting the nut 70 to compress the springs and of adjusting the primary plunger Si) to a certain predetermined position with respect to the follower 46 by rotating the plunger to move it along its threads 57. Y

To prevent a tendency of the screw '74 to spin back due to the reactive force of the follower 46, and thus eliminate friction or torque load between the threads of the screw and the sleeve 72, axial engagement of the end of the screw vand the primary plunger is avoided in the present construction. Adjustment of the primary plunger 50 by rotation of the screw without axial engagement is possible because of a special coupling arrangement best shown in Figure 3. Screw 74 carries a head 53 integral therewith and primary plunger 50 carries a complementary head 52 on the end of shaft 54 which is swaged into opening 55 in the end of the plunger 50 and held therein by serrations 56. Vertical faces 52a and 53a are adapted to engage so that primary plunger 50 rotates with the screw 74. Since the threads 75 are double and the threads 57 are single the screw travels twice the distance of the plunger and the coupling heads 52 and 53 will separate and disengage within two revolutions. The end faces 521: and 53h of the heads may -abut when the screw is moving toward the plunger due to the fast lead of the screw threads 75. To avoid jamming, the faces 52h and 53b are bevelled at an angle equal to or greater than the pitch of the screw threads 75.. By this arrangement the heads 52 and 53 engage so that the primary plunger may be adjusted with respect to the follower without moving the secondary plunger 60. The latch mechanism for locking the screw 74 against axial movement by the springs until such time as it is released by pressing button is best shown in Figures l, 2 and 4. A pin 76 extending through the upper end of the screw 74 is adapted to slide axially within slots 77 provided therefor within the latch housing 20. Latch wedges 82 project through the openings 83 provided thereforwithin the latch housing 20. The outer ends of the wedges 82 are cut out to embrace thesurface of the screw 74 while the upper surfaces contain grooves 86, which embrace the ends of the pin 76 when the screw is in locked position, as shown in Figure 1. The latch wedges 82 are tapered toward the inner ends, the slope of the taper preferably being about 20 from horizontal. The cupshaped button 90 is provided with an inwardly turned flange 93 adapted to bear against the outer ends of the latch wedges 82 normally to prevent them from retracting into the grooves 84 in the latch housing. Button 90 may be depressed, causing the side walls thereof to move downwardly into the grooves 84 against the compression of the spring 85, whereupon grooves 92 in the side wall of the button become aligned with the latch wedges 82. Because Vof the slope on the bottom of the wedges 82, they move outwardly into the groove 92 under the inuence of the springs. 80, 81, which are tending to thrust the screw 74 downwardly, whereupon the screw 74 is released.

The inside edge 95 of the inturned flange 93 on the button is tapered to control button pressure. An'angle Aof' about 4 or 5 is enough to prevent the button from freezing due to thrust on wedges 82 from the screw pressure'. The button pressure may be controlled by changing this angle.

To keep the button 90 depressed While the wedges 82 are in the slot 92, a pair of small opposed bosses 91 are provided on the inner surface of the button cap' 24. By

essaiera .igrevenangfthe hun@ aanmaning' up @tannin-straatnaation .due toithe friction of the bosses' thewedgeszrejn In operation, the winding sleeve1`4is rotat'ed'counter clockwise to turn the screw 74`out'of-the sleeve'72'pe'p`ara'- tory to compressing the springs 8 0 and 8 1. .(It is assumed that the Vinstrument at this point has just been discharged and the plunger assembly-fis in the lower position within the dosage sleeve 12.) As the pointed-end .74a of the screw 74 contacts and compresses 'therspring 85,'the button moves upwardly and forces the wedges out of the slot 92 and underneath the pin 76 to latch the screw 74. The spring 85 then snaps the button to its normally raised position. The winding sleeve 14 is then rotated in a clockwise direction to turn the screw 74 within the sleeve 72 and lift the nut 70 to compress the springs 80, 81.

As the nut 70 moves up the threads of the screw 74 the head 52 fixed to the plunger 50 engages the head 53 on the lower end of the screw and the mating faces 52a and 53a slide into rotational engagement. If the button 90 is depressed when the springs are fully compressed, the maximum depth of penetration of the jet .stream discharged from the ampule 42 will result because the impact of the primary plunger 59 on the follower 46 is greatest. The magnitude and duration of the rst stage pressure is determined by two factors: (l) the distance between the end of the plunger 50 and the follower 46, which determines the amount of impact, and (2) the distance the primary plunger 50 moves into the ampule beyond the end of the secondary plunger 60. In the present construction distance (l) is variable and distance (2) is constant. To reduce the pressure of the first stage of the injection the winding sleeve 14 may be backed off, that is, rotated in a counterclockwise direction, to decrease the distance betwen the end of the plunger 50 and the follower. This causes the nut 70 to be lowered, but due to the style of screw threads 75 and 57, the plunger 50 descends at half the rate of the nut 70. Therefore, if the nut 70 descends .10 inch, the plunger 50 descends only .05 inch. By adjusting the rotation of the winding sleeve in a counterclockwise direction the distance between the primary plunger 50 and the follower 46 may be reduced from the maximum to any distance down to zero, at which point the plunger and the follower are engaged and there is no impact at all. This arrangement makes possible very accurate control of the pressure during the first stage of the injection, since the plunger 50 moves only a small distance per unit rotation of the winding sleeve 14. Complementary graduations on the winding sleeve and the body may be provided to designate to the physician using the instrument the magnitude of the initial stage pressure, just as in prior instruments.

A new ampule is then fitted into the nose of the instrument and secured in place by means of the screw cap 40. To discharge the medicament the button 90 .is depressed, causing the wedges 82 to slide into the slot 92 provided therefor, which releases the screw 74, permitting the springs the propel the nut downwardly at a rapid rate. Primary plunger 50 strikes the follower 46 with a force determined by the impact distance, turns the follower inside out and pushes it down into the bore of the ampule to the point indicated in Figure 6. At this point the nut 70 engages the secondary plunger 60 as it travels downwardly causing the remaining liquid in the ampule to be expelled at reduced pressure.

It has been found that the combination of springs 80 ,naar uses-nana 'in-aanstaan 'tss-passera@ led `vto lo'neen'f'l thereof and `adapted toy hold anori through thejoriil'ce, powerfrnfefah Jplunger includingcoil springs moutitedcficentric'ally in uenc'ies, or at least minimizes than te Itnt: -exteatwhat injection is virtually painless;

Various modifications vinthe structuref theginsftrufnitt will occur to those vskilled inthe art without departing inl-the body cancels out *the objectionable high fed `fromfthe spirit and scope of the invention. -It =s, VVforeynot my intention to limit the inventiontotheiformls illustrated 'other 'than as necessitated v"by -the scope "of the appended claims.

l claim as my invntio'n 1. In a hypodermic injector, an 4assetrtbly c otri"` an elongatedbody, ah ampule'holde'r detachablylco ampule, a plunger Vslidablyl 4mountedwithin sa'ud and adapted for 'engaging andpropclling'affollowr1` inthe bore of said ampule to "discharge liquidl sfr prope in 1d pairs within the body, each of said springs comprising a pair having different natural-frequencies, means for compressing said springs, and means for suddenly releas ing the compressed springs to perform propulsion Vof the plunger and follower.

2. In a hypodermic injector, an asembly comprising an elongated body, an ampule holder detachably connected to one end thereof and adapted to hold an oriced ampule, a plunger assembly mounted within said body comprising a primary plunger and a sleeve-like secondary plunger slidably mounted on said primary plunger, the end of said primary plunger being adapted to engage the central area of a llexible follower within the bore of said ampule and the end of said secondary plunger being adapted to engage the area surrounding said central area, power means including a tlanged sleevelike nut, a screw threadedly engaged in the upper portion of said nut, and pairs of coil springs seated on said nut, said primary plunger being threaded into the lower portion of said nut and rotationally engageable with said screw to permit varying the distance between the lower end of the primary plunger and said follower, and means for latching said screw against the compressive force of the springs and for suddenly releasing the latch to propel said nut and plunger assembly.

3. The injector of claim 2 in which the latching means for the screw comprises a pair of wedges adapted to support projections extending from the screw near the top end thereof, said wedges being radially slidably mounted in slots provided therefor in the body, and an axially movable release button of inverted cup shape mounted in the top of the body having an inwardly extending flange and a circumferential groove above the flange, said groove being adapted to receive said wedges when the button is depressed and said flange being adapted to force the wedges from the groove and beneath said projections and prevent them from moving outwardly when the button is in raised position.

4. In a hypodermic injector, an assembly comprising an elongated body, an ampule holder detachably connected to one end thereof and adapted to hold an orifced ampule, a plunger assembly mounted within said body comprising a primary plunger and a sleeve-like secondary plunger slidably mounted on said primary plunger, the end of said primary plunger being adapted to engage the central area of a flexible follower within the bore of said ampule and the end of said secondary plunger being adapted to engage the area surrounding said central area, power means including a flanged sleeve-like nut, a screw threadedly engaged in the upper portion of said nut, and pairs of coil springs seated on said nu't, said primary plunger being threaded into the lower portion of said nut and rotationally engageable with said screw to permit varying the distance between the lower end of the primary plunger and said follower, the cooperating threads of said screw and said upper nut por- `tion having a faster lead than the cooperating threads of said primary plunger and said lower nut portion, and

`means for latching said screw against the compressive cluding coil springs disposed within diametrically opposed bores circumferentially spaced within the body, each bore containing two concentric springs having the same natural frequencies as the corresponding springs in the bore diametrically opposed thereto, but different natural frequencies from corresponding springs in adjacent bores. 6. In a hypodermic injector, an assembly comprising Van elongated body, a cylindrical chamber in 'oneend thereof havinga bore terminating in 'a minute orifice and adapted to hold liquid' to be discharged from the injector,

.afollower within thevbore of said chamber, a plunger slidably mounted within said' body and adapted for engaging and propelling said follower to discharge liquid contents through said orifice, power means vfor propelling said plunger including coil springs mounted concentrically in pairs within the body, each of saidfsprings comprising a pair having different natural frequencies, means for compressing said springs, and means for suddenly releasing the compressed springs to perform propulsion ofthe plunger and follower;

Y References Cited inthe tile of this patent A UNITED S'I`A'TES1:A'I`l1i`l'l`S Y smeer sept. 29, 1953 2,671,347 Scherer Mar. 9, 1954

Images