ONE HAND INJECTOR
United States Patent 3722512
A hypodermic syringe is provided by the combination of an elongated handle which longitudinally supports an elongated cylinder that is slidable along the handle, with the injector needle being connected to a piston that is fixed with respect to the handle and is located within the cylinder. An abutment flange is located on the handle to limit rearward movement of the elongated cylinder to prevent the cylinder from disengaging the piston and to limit the amount of liquid that can be injested into the cylinder. The handle has a split portion for releasable engagement with the mounting for the needle.
US Patent References:
SYRINGE GUIDE AND INDICATOR
LeMarie - October 1971 - 3610241
Hypodermic syringe
Lockhart - September 1946 - 2408323
DISPOSABLE INJECTOR AND HOLDER THEREFOR
Sly - October 1970 - 3534735
Cartridge holder
Sarnoff - August 1964 - 3144178
Device for hypodermic injections
Kollsman - December 1951 - 2578814
SYRINGE GUIDE AND INDICATOR
LeMarie - October 1971 - 3610241
Hypodermic syringe
Lockhart - September 1946 - 2408323
DISPOSABLE INJECTOR AND HOLDER THEREFOR
Sly - October 1970 - 3534735
Cartridge holder
Sarnoff - August 1964 - 3144178
Device for hypodermic injections
Kollsman - December 1951 - 2578814
Inventors:
Hein, Gary L. (Decatur, IL)
Larson, Roger R. (Decatur, IL)
Larson, Roger R. (Decatur, IL)
Application Number:
05/061121
Publication Date:
03/27/1973
Filing Date:
08/05/1970
View Patent Images:
Export Citation:
Assignee:
Lincoln Laboratories, Inc. (Decatur, IL)
Primary Class:
International Classes:
A61M5/24; A61M5/22; A61M5/32
Field of Search:
128/220,218R,218P,218N,218D,218DA,218PA,215,272,218C,218F,234,237 222/321-325,386,391
Primary Examiner:
Gaudet, Richard A.
Assistant Examiner:
Mcgowan J. C.
Claims:
What is claimed is
1. In a one-hand operated injector device of the type that includes elongated handle means for slidably supporting an elongated cylinder and for non-slidably supporting elongated piston means that is cooperatively arranged with the cylinder for effecting injections of material stored in the cylinder or ingestion of material into the cylinder, the improvement comprising the piston means having a bore therethrough, the cylinder being slidably mounted on the holder means and having an open end for receiving thereinto the piston means and a closed end, attachment means on one end of the holder means for attaching the piston means to the holder means and being in alignment with and in proximity to the cylinder's open end, a hollow needle attached to the piston means and in communication with the bore; and an abutment flange located on the handle means in alignment with the cylinder's path of travel to limit sliding movement of the elongated cylinder in one direction relative to the piston means, the flange being spaced rearwardly from the closest end of the piston means a predetermined distance that is less than the length of the cylinder to prevent the cylinder from inadvertently disengaging from the piston means.
2. An injector device as set forth in claim 1, wherein a forward portion of the handle means spaced distally of the abutment flange has attachment means thereon for releasable connection to the piston means, and the forward end section of the elongated handle means is longitudinally split to provide flexibility that accommodates attachment and release between the attachment means and the piston means.
3. An injector device as set forth in claim 1, wherein said piston means is a unitary body formed of a plastic material that provides an axial bore therethrough, the rearward end of said unitary body providing a cylindrical head for entry into the cylinder, and the forward end of the body providing means for attachment of an injection needle thereto.
4. An injector device in claim 1, wherein the sides of the handle are undulated to provide a comfortable hand gripping surface.
5. An injector device as set forth in claim 1, wherein the cylinder carries a thumb tab that is arcuately shaped to provide spaced lower edge surfaces which lie closely adjacent surfaces of the handle means to restrain rotation of the cylinder relative to the handle means.
6. An injector device as set forth in claim 1, wherein the elongated handle is numerically calibrated to measure the amount of injectible material in the cylinder, the calibration being located between the abutment flange and the closest end of the piston means.
7. An injector device as set forth in claim 1, wherein the handle means and piston means are each a unitary body molded of plastic and are each provided with interengaging elements of V-shape which cooperate to hold the piston means firmly assembled on the handle means.
8. An injector device as set forth in claim 7, wherein the portion of the handle means with said V-shape element thereon is rendered somewhat radially flexible by longitudinally segmenting the handle means, thereby accommodating interengagement and release of the interengaging elements on the handle means and piston means.
9. A device as in claim 1 wherein the piston means are non-metallic to increase separation of liquid within the cylinder from the metal needle.
10. A device as in claim 1 wherein the piston means are formed of a translucent plastic having a longitudinal bore therethrough which permits visual observation of liquid in the bore of the piston means.
11. An injector device as in claim 1 wherein the piston means is elongated and has a longitudinal bore therethrough, a metal injection needle secured to the end of the piston means distal from the end that cooperates with the cylinder, and the bore in the piston means being of greater cross-section than the size of the passage through the injection needle so as to provide for achieving ram effect in usage of the injector device.
1. In a one-hand operated injector device of the type that includes elongated handle means for slidably supporting an elongated cylinder and for non-slidably supporting elongated piston means that is cooperatively arranged with the cylinder for effecting injections of material stored in the cylinder or ingestion of material into the cylinder, the improvement comprising the piston means having a bore therethrough, the cylinder being slidably mounted on the holder means and having an open end for receiving thereinto the piston means and a closed end, attachment means on one end of the holder means for attaching the piston means to the holder means and being in alignment with and in proximity to the cylinder's open end, a hollow needle attached to the piston means and in communication with the bore; and an abutment flange located on the handle means in alignment with the cylinder's path of travel to limit sliding movement of the elongated cylinder in one direction relative to the piston means, the flange being spaced rearwardly from the closest end of the piston means a predetermined distance that is less than the length of the cylinder to prevent the cylinder from inadvertently disengaging from the piston means.
2. An injector device as set forth in claim 1, wherein a forward portion of the handle means spaced distally of the abutment flange has attachment means thereon for releasable connection to the piston means, and the forward end section of the elongated handle means is longitudinally split to provide flexibility that accommodates attachment and release between the attachment means and the piston means.
3. An injector device as set forth in claim 1, wherein said piston means is a unitary body formed of a plastic material that provides an axial bore therethrough, the rearward end of said unitary body providing a cylindrical head for entry into the cylinder, and the forward end of the body providing means for attachment of an injection needle thereto.
4. An injector device in claim 1, wherein the sides of the handle are undulated to provide a comfortable hand gripping surface.
5. An injector device as set forth in claim 1, wherein the cylinder carries a thumb tab that is arcuately shaped to provide spaced lower edge surfaces which lie closely adjacent surfaces of the handle means to restrain rotation of the cylinder relative to the handle means.
6. An injector device as set forth in claim 1, wherein the elongated handle is numerically calibrated to measure the amount of injectible material in the cylinder, the calibration being located between the abutment flange and the closest end of the piston means.
7. An injector device as set forth in claim 1, wherein the handle means and piston means are each a unitary body molded of plastic and are each provided with interengaging elements of V-shape which cooperate to hold the piston means firmly assembled on the handle means.
8. An injector device as set forth in claim 7, wherein the portion of the handle means with said V-shape element thereon is rendered somewhat radially flexible by longitudinally segmenting the handle means, thereby accommodating interengagement and release of the interengaging elements on the handle means and piston means.
9. A device as in claim 1 wherein the piston means are non-metallic to increase separation of liquid within the cylinder from the metal needle.
10. A device as in claim 1 wherein the piston means are formed of a translucent plastic having a longitudinal bore therethrough which permits visual observation of liquid in the bore of the piston means.
11. An injector device as in claim 1 wherein the piston means is elongated and has a longitudinal bore therethrough, a metal injection needle secured to the end of the piston means distal from the end that cooperates with the cylinder, and the bore in the piston means being of greater cross-section than the size of the passage through the injection needle so as to provide for achieving ram effect in usage of the injector device.
Description:
BACKGROUND OF THE INVENTION
This invention relates to a needle-type injector, and more particularly relates to a combination injector and manipulation handle therefor by means of which a technician obtains greater one-hand control in the insertion of the needle and in the injection of liquid through the needle.
Hypodermic, or needle-type, injectors have been known for many years. Single-use, or throw-away needle-type injectors have become very popular because of their assurance as to sterility and avoidance of transmission of infections, such as infectious hepatitis.
Some prior injector constructions utilize an extensible plunger for cooperative use with a barrel-like chamber for holding the liquid to be injected. In the use of such a device, the technician, such as a doctor or nurse, first holds the elongated syringe or barrel-like part with needle assembled thereon like a dart and seeks to introduce the needle where desired. Then the technician must either use one hand to hold the barrel and the other hand operates the plunger that extends rearwardly of the barrel, or if a technician attempts one hand manipulation, his hand is caused to crawl back to the end of the barrel where the plunger may be engaged by the thumb for manipulation. In such one hand operation the location of the hand on the plunger at any substantial distance remote from the needle point makes manipulation of the injector awkward and difficult. An additional disadvantage exists where the plunger is to be first manipulated rearwardly in a suction stroke to load the barrel with liquid because thereafter the plunger must be maintained stationary while removing the needle from the partly evacuated vial carrying the supply of liquid.
Other injector constructions do provide for convenient one hand manipulation, and the instant invention is an improvement over such constructions which are disclosed in pending applications of Roger R. Larson, Ser. No. 748,258, filed July 29, 1968, now U.S. Pat. No. 3,535,068, and of Thomas S. Sly, Ser. No. 797,411, filed Feb. 7, 1969, now U.S. Pat. No. 3,534,735, both assigned to the assignee of this application.
One object of this invention is to provide, in a hypodermic syringe, which gives greater control to the technician in inserting the needle where desired and in thereafter effecting injection of liquid through the needle, the improvement feature of means for limiting the amount of injectable material that can be drawn into the unit and for preventing the parts from inadvertently disengaging each other.
Another object of this invention is to provide a simplified construction for a hypodermic syringe which allows greater tolerances in construction so as to reduce costs of such construction.
Another object of this invention is to provide a hypodermic syringe that can use a preloaded cartridge while preventing the injectable material from inadvertently contacting the metal needle until the time of injection.
A further object of this invention is to provide a needle-like injector which is comfortable to use and which is calibrated in a manner that makes it more easily read by a technician.
A still further object of the present invention is to provide a needle like injector and support therefor having components which are restrained from rotating movement relative to one another.
Further objects and advantages of this invention will become apparent as the following description proceeds and the features of novelty which characterize this invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is top plan view of our invention;
FIG. 2 is an enlarged cross-sectional view taken substantially along the line 2--2 of FIG. 1 and showing the location of parts with the cylinder filled with liquid prior to an injection;
FIG. 3 is a view similar to FIG. 2 but showing the location of parts when the cylinder is empty, such as either after an injection or prior to manipulation of the cylinder before filling;
FIG. 4 is a cross-sectional view taken substantially along the line 4--4 of FIG. 1;
FIG. 5 is a cross-sectional view taken substantially along the line 5--5 of FIG. 1; and
FIG. 6 is a perspective view of the improved holder that has been shown in use with our invention.
DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENT
Referring to the drawing, a hypodermic syringe shown generally at 8 is intended to be held in the palm of one's hand by a technician, such as a doctor or nurse, and is adapted for one-hand operation by the technician. The injector device itself includes an elongated piston means 10 formed of a plastic material and having a number of longitudinally extending ribs 12 on a stem portion thereof, and a cylinder-entering cylindrical portion 14 that carries a pair of axially spaced O-ring seals 16 in its periphery. An axial passageway 18 extends through the length of piston means 10. The maximum diameter of ribs 12 and of cylinder portion 14 is the same. As seen in FIG. 2, the selected dimension accommodates the wall of a cylinder sliding between head portion 14 and the spaced wall of a holder.
The piston means includes a connection head 20 having a circumferential groove 21 of V-shaped cross-section adapted for a snapfitting engagement with a complementary V-ridge means provided on a handle means 22. The front portion of the connection head is shaped by tapering or the like to receive and frictionally retain thereon a plastic connection cup 24 that attaches to the rear end of a metal injection needle 26 distally of the needle's sharpened tip 28.
The piston means 10 rides within a plastic barrel or cylinder 30. A thumb tab 32 is integrally formed with the forward end of the cylinder to enable the technician to easily move the cylinder with respect to both handle 22 and piston means 10.
Handle 22 comprises a molded plastic member having a plurality of undulations or finger-seats 34 on both sides thereof for providing a comfortable holding surface. As shown most clearly in FIG. 6, handle 22 defines an elongated arcuate grooved portion or slideway 36 for slidably receiving the cylinder 30 therein.
The forward end 40 of handle 22 is split to define an elongated slot 38 which extends rearwardly a distance of about half the entire handle length. Inturned arcuate flanges 42 and 42' having V-ridge portions are provided adjacent forward end 40 of the handle for entry into a groove 21 defined on head 20 and for effecting a precise, yet yieldable and releasable interconnection. The split handle provides the necessary yielding or resilience to enable the parts to snap fit together or to be released.
Handle 22 defines a flange 46 thereon which is adapted to be abutted by end 48 of cylinder 30 to limit rearward movement of the cylinder. As shown most clearly in FIGS. 1 and 2, the members are dimensioned so that flange 46 is spaced from end 50 of piston 10 a predetermined distance that is less than the length of cylinder 30 in order to prevent the cylinder from inadvertently disengaging the portion of piston 10 that includes the seals 16. Further, the dimensions are such that the amount of injectable material that can be drawn into, or ingested to, the cylinder is limited by the open volume of the cylinder available to be filled by the time that end 48 of the cylinder engages with stop flange 46.
Referring to FIG. 1, it is seen that handle 22 is provided with graduations 52, with the lowest number having the closest position to the forward end 40 of the handle. Graduations 52 are used to measure the amount of injectable material in the cylinder and it has been found that by locating the calibrations on the handle adjacent the cylinder, as indicated, reading is more easily made by using end 48 of the cylinder as the "pointer" with respect to the calibrations 52.
The upright thumb tab 32 carried by cylinder 30 is generally arcuately shaped and is provided with lower surfaces 54, 56 which are arranged to lie closely adjacent to the upper surface 58 of handle 22 to substantially restrain the cylinder 30 from rotation from the position shown.
The use of the device will be readily understood from the foregoing description of the structure. Thus, the technician grasps handle 22 comfortably and securely in the palm of his hand and is thereby able to use handle 22 to manipulate the needle 26 to effect a proper piercing of the body to lodge the needle in a vein or other body portion, as desired. The handle 22 is quite close to the body region being pierced and this results in more accurate manipulation. Once the needle 26 is properly lodged where desired, the technician need do no further shifting of his hand but by manipulating control flange 32 forward with his thumb, the cylinder 30 is caused to slide forwardly in slideway 36 toward the position in FIG. 3. This pressurizes the liquid in the cylinder which moves through bore 18 and through the needle during the injection process.
In order to ingest the injectable material into the cylinder, the technician inserts needle 26 into a vial of injectable material and manipulates control tab 32 rearwardly with his thumb so that the cylinder 30 is caused to slide rearwardly in slideaway 36 toward the position in FIG. 2. The technician may control the amount of liquid being ingested into the cylinder by observing the graduated markings 52 on the handle 22. By moving control tab 32 rearwardly, the suction in cylinder 35 created by movement of the cylinder wall relative to sealing piston portion 14 will draw liquid through bore 18 so as to load the cylinder 30. There is no possibility of the cylinder inadvertently disengaging the piston during rearward movement of the cylinder because end 48 of the cylinder will abut flange 46 of the handle while the sealing rings 16 and the cylinder are still in engagement.
A "preloaded cartridge" can be used with the present invention by filling cylinder 22 with injectable material for storage until subsequent injection. The "preloaded cartridge" assembly would include the preloaded cylinder 22 with piston means 10 connected thereto substantially in the position illustrated in FIG. 2, with or without a needle assembly attached. Since the injectable material is behind the piston and will not be contacting the needle or any metal, any problem of metal contamination is avoided.
Another advantage in the construction herein disclosed is that piston means 10, by being formed of a transparent or translucent plastic, provides a visual check of the condition of contents within bore 18 so that if a small amount of blood has been drawn into bore 18, it will be seen when aspirating the syringe prior to injection and before the blood mixes with the solution in the cylinder 30.
The bore 18 in piston means 10 is preferably of greater dimension than the passage through needle 26, so as to obtain the benefit of ram effect, that is application of plunger force over a large area compared to the area of the needle through which fluid is discharged, in driving injectable material through needle 26 into muscle tissue. Such ram effect normally is obtained in a conventional hypodermic where the large storage barrel connects to the restricted passage through the elongated needle. In the instant embodiment, the construction provides a greater ram effect than would be obtained with use of a needle whose overall length was equivalent to the length of piston and needle combined, because the cross-section of bore 18 in piston 10 is provided of a size greater than the cross-section of the passage through needle 26 and the long bore 18 of greater cross-section contributes advantageously to the ram effect.
The use of plastic piston means 10 separate from the metal needle 24-26-28 provides additional advantages in that the combination of handle means 22, cylinder 30 and piston means 10 may be packaged and handled as a sub-assembly. The needle may be separately packaged and attached when needed. Also, the presence of plastic piston 10 insures the greatest possible separation of fluid within cylinder 30 from the metal needle to avoid contamination or chemical reaction resulting from contact. Finally the plastic piston 10 is transparent or translucent which permits some observation of fluid within bore 18 which is desirable when aspirating the syringe prior to injection.
Although an illustrative embodiment of the invention has been shown and described, it is to be understood that various substitutions and modifications may be made by those skilled in the art without departing from the spirit and scope of the present invention.
This invention relates to a needle-type injector, and more particularly relates to a combination injector and manipulation handle therefor by means of which a technician obtains greater one-hand control in the insertion of the needle and in the injection of liquid through the needle.
Hypodermic, or needle-type, injectors have been known for many years. Single-use, or throw-away needle-type injectors have become very popular because of their assurance as to sterility and avoidance of transmission of infections, such as infectious hepatitis.
Some prior injector constructions utilize an extensible plunger for cooperative use with a barrel-like chamber for holding the liquid to be injected. In the use of such a device, the technician, such as a doctor or nurse, first holds the elongated syringe or barrel-like part with needle assembled thereon like a dart and seeks to introduce the needle where desired. Then the technician must either use one hand to hold the barrel and the other hand operates the plunger that extends rearwardly of the barrel, or if a technician attempts one hand manipulation, his hand is caused to crawl back to the end of the barrel where the plunger may be engaged by the thumb for manipulation. In such one hand operation the location of the hand on the plunger at any substantial distance remote from the needle point makes manipulation of the injector awkward and difficult. An additional disadvantage exists where the plunger is to be first manipulated rearwardly in a suction stroke to load the barrel with liquid because thereafter the plunger must be maintained stationary while removing the needle from the partly evacuated vial carrying the supply of liquid.
Other injector constructions do provide for convenient one hand manipulation, and the instant invention is an improvement over such constructions which are disclosed in pending applications of Roger R. Larson, Ser. No. 748,258, filed July 29, 1968, now U.S. Pat. No. 3,535,068, and of Thomas S. Sly, Ser. No. 797,411, filed Feb. 7, 1969, now U.S. Pat. No. 3,534,735, both assigned to the assignee of this application.
One object of this invention is to provide, in a hypodermic syringe, which gives greater control to the technician in inserting the needle where desired and in thereafter effecting injection of liquid through the needle, the improvement feature of means for limiting the amount of injectable material that can be drawn into the unit and for preventing the parts from inadvertently disengaging each other.
Another object of this invention is to provide a simplified construction for a hypodermic syringe which allows greater tolerances in construction so as to reduce costs of such construction.
Another object of this invention is to provide a hypodermic syringe that can use a preloaded cartridge while preventing the injectable material from inadvertently contacting the metal needle until the time of injection.
A further object of this invention is to provide a needle-like injector which is comfortable to use and which is calibrated in a manner that makes it more easily read by a technician.
A still further object of the present invention is to provide a needle like injector and support therefor having components which are restrained from rotating movement relative to one another.
Further objects and advantages of this invention will become apparent as the following description proceeds and the features of novelty which characterize this invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is top plan view of our invention;
FIG. 2 is an enlarged cross-sectional view taken substantially along the line 2--2 of FIG. 1 and showing the location of parts with the cylinder filled with liquid prior to an injection;
FIG. 3 is a view similar to FIG. 2 but showing the location of parts when the cylinder is empty, such as either after an injection or prior to manipulation of the cylinder before filling;
FIG. 4 is a cross-sectional view taken substantially along the line 4--4 of FIG. 1;
FIG. 5 is a cross-sectional view taken substantially along the line 5--5 of FIG. 1; and
FIG. 6 is a perspective view of the improved holder that has been shown in use with our invention.
DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENT
Referring to the drawing, a hypodermic syringe shown generally at 8 is intended to be held in the palm of one's hand by a technician, such as a doctor or nurse, and is adapted for one-hand operation by the technician. The injector device itself includes an elongated piston means 10 formed of a plastic material and having a number of longitudinally extending ribs 12 on a stem portion thereof, and a cylinder-entering cylindrical portion 14 that carries a pair of axially spaced O-ring seals 16 in its periphery. An axial passageway 18 extends through the length of piston means 10. The maximum diameter of ribs 12 and of cylinder portion 14 is the same. As seen in FIG. 2, the selected dimension accommodates the wall of a cylinder sliding between head portion 14 and the spaced wall of a holder.
The piston means includes a connection head 20 having a circumferential groove 21 of V-shaped cross-section adapted for a snapfitting engagement with a complementary V-ridge means provided on a handle means 22. The front portion of the connection head is shaped by tapering or the like to receive and frictionally retain thereon a plastic connection cup 24 that attaches to the rear end of a metal injection needle 26 distally of the needle's sharpened tip 28.
The piston means 10 rides within a plastic barrel or cylinder 30. A thumb tab 32 is integrally formed with the forward end of the cylinder to enable the technician to easily move the cylinder with respect to both handle 22 and piston means 10.
Handle 22 comprises a molded plastic member having a plurality of undulations or finger-seats 34 on both sides thereof for providing a comfortable holding surface. As shown most clearly in FIG. 6, handle 22 defines an elongated arcuate grooved portion or slideway 36 for slidably receiving the cylinder 30 therein.
The forward end 40 of handle 22 is split to define an elongated slot 38 which extends rearwardly a distance of about half the entire handle length. Inturned arcuate flanges 42 and 42' having V-ridge portions are provided adjacent forward end 40 of the handle for entry into a groove 21 defined on head 20 and for effecting a precise, yet yieldable and releasable interconnection. The split handle provides the necessary yielding or resilience to enable the parts to snap fit together or to be released.
Handle 22 defines a flange 46 thereon which is adapted to be abutted by end 48 of cylinder 30 to limit rearward movement of the cylinder. As shown most clearly in FIGS. 1 and 2, the members are dimensioned so that flange 46 is spaced from end 50 of piston 10 a predetermined distance that is less than the length of cylinder 30 in order to prevent the cylinder from inadvertently disengaging the portion of piston 10 that includes the seals 16. Further, the dimensions are such that the amount of injectable material that can be drawn into, or ingested to, the cylinder is limited by the open volume of the cylinder available to be filled by the time that end 48 of the cylinder engages with stop flange 46.
Referring to FIG. 1, it is seen that handle 22 is provided with graduations 52, with the lowest number having the closest position to the forward end 40 of the handle. Graduations 52 are used to measure the amount of injectable material in the cylinder and it has been found that by locating the calibrations on the handle adjacent the cylinder, as indicated, reading is more easily made by using end 48 of the cylinder as the "pointer" with respect to the calibrations 52.
The upright thumb tab 32 carried by cylinder 30 is generally arcuately shaped and is provided with lower surfaces 54, 56 which are arranged to lie closely adjacent to the upper surface 58 of handle 22 to substantially restrain the cylinder 30 from rotation from the position shown.
The use of the device will be readily understood from the foregoing description of the structure. Thus, the technician grasps handle 22 comfortably and securely in the palm of his hand and is thereby able to use handle 22 to manipulate the needle 26 to effect a proper piercing of the body to lodge the needle in a vein or other body portion, as desired. The handle 22 is quite close to the body region being pierced and this results in more accurate manipulation. Once the needle 26 is properly lodged where desired, the technician need do no further shifting of his hand but by manipulating control flange 32 forward with his thumb, the cylinder 30 is caused to slide forwardly in slideway 36 toward the position in FIG. 3. This pressurizes the liquid in the cylinder which moves through bore 18 and through the needle during the injection process.
In order to ingest the injectable material into the cylinder, the technician inserts needle 26 into a vial of injectable material and manipulates control tab 32 rearwardly with his thumb so that the cylinder 30 is caused to slide rearwardly in slideaway 36 toward the position in FIG. 2. The technician may control the amount of liquid being ingested into the cylinder by observing the graduated markings 52 on the handle 22. By moving control tab 32 rearwardly, the suction in cylinder 35 created by movement of the cylinder wall relative to sealing piston portion 14 will draw liquid through bore 18 so as to load the cylinder 30. There is no possibility of the cylinder inadvertently disengaging the piston during rearward movement of the cylinder because end 48 of the cylinder will abut flange 46 of the handle while the sealing rings 16 and the cylinder are still in engagement.
A "preloaded cartridge" can be used with the present invention by filling cylinder 22 with injectable material for storage until subsequent injection. The "preloaded cartridge" assembly would include the preloaded cylinder 22 with piston means 10 connected thereto substantially in the position illustrated in FIG. 2, with or without a needle assembly attached. Since the injectable material is behind the piston and will not be contacting the needle or any metal, any problem of metal contamination is avoided.
Another advantage in the construction herein disclosed is that piston means 10, by being formed of a transparent or translucent plastic, provides a visual check of the condition of contents within bore 18 so that if a small amount of blood has been drawn into bore 18, it will be seen when aspirating the syringe prior to injection and before the blood mixes with the solution in the cylinder 30.
The bore 18 in piston means 10 is preferably of greater dimension than the passage through needle 26, so as to obtain the benefit of ram effect, that is application of plunger force over a large area compared to the area of the needle through which fluid is discharged, in driving injectable material through needle 26 into muscle tissue. Such ram effect normally is obtained in a conventional hypodermic where the large storage barrel connects to the restricted passage through the elongated needle. In the instant embodiment, the construction provides a greater ram effect than would be obtained with use of a needle whose overall length was equivalent to the length of piston and needle combined, because the cross-section of bore 18 in piston 10 is provided of a size greater than the cross-section of the passage through needle 26 and the long bore 18 of greater cross-section contributes advantageously to the ram effect.
The use of plastic piston means 10 separate from the metal needle 24-26-28 provides additional advantages in that the combination of handle means 22, cylinder 30 and piston means 10 may be packaged and handled as a sub-assembly. The needle may be separately packaged and attached when needed. Also, the presence of plastic piston 10 insures the greatest possible separation of fluid within cylinder 30 from the metal needle to avoid contamination or chemical reaction resulting from contact. Finally the plastic piston 10 is transparent or translucent which permits some observation of fluid within bore 18 which is desirable when aspirating the syringe prior to injection.
Although an illustrative embodiment of the invention has been shown and described, it is to be understood that various substitutions and modifications may be made by those skilled in the art without departing from the spirit and scope of the present invention.