Syringes are used in various industries, including manufacturing, medicine, and biology, for dispensing and aspirating fluid materials. A syringe is essentially a hollow barrel with an open end serving as the entrance for a plunger or piston and a terminal end containing a shoulder with a specialized tip used to dispense the substance contained within the syringe barrel or aspirate fluid materials into said barrel. Because of the numerous uses for syringes, there are a myriad of tip designs and each tip is specialized for a particular application. The basic syringe tip consists of a frustoconical nose that is elongated and/or shaped for the intended use.
A syringe is often fitted with a detachably retained aspiration or irrigation device configured to perform the intended task. Examples of such devices include suction tubes, irrigation hoses, dispensing nozzles, catheters, cannulas and needles. A specialized connector or adaptor is often required to attach the various devices to the number of syringe tips. Several designs for adaptors have been popularized, a number of which are discussed herein.
The Luer slip is the most widely used syringe adaptor design. The male Luer tip of the syringe is a small diameter frustoconical shape with a small lumenal opening communicating with the inside of the syringe. The female Luer slip adaptor is a frustoconical tip of substantially the same dimensions as the male Luer tip. A female Luer slip is fitted at one end of an irrigation and/or aspiration device to allow the device to be attached to the syringe in such a way as to allow fluid communication between the device and the syringe. The female Luer slip is inserted over the male Luer tip of the syringe to form a combination device. As the parts are pressed together, the female Luer slip is deformed azimuthally and radially. The elasticity of the female Luer material compresses the male Luer tip, forming a friction fit and an effective fluid seal. The Luer slip adaptor is simple and efficient; however, it allows for motion and loosening between the syringe and the device. Torsional, longitudinal, and moment loading of the Luer slip adaptor results in separation of the adaptor from the syringe. Also, the maximum diameter of fluid communications between the syringe and the adaptor is limited to a channel of approximately 1 millimeter in diameter. Due to these drawbacks, other syringe tip designs have been popularized.
A Luer-Lok type syringe adaptor is described by Senkowski et al., in U.S. Pat. No. 3,402,713, incorporated by reference herein. The Luer-Lok is perhaps the second most widely used syringe adaptor design. The Luer-Lok adaptor allows a device to be attached to the tip of a syringe using the Luer slip design in combination with a screw mechanism. The Luer-Lok system includes a coaxial internally threaded barrel disposed about the periphery of the male Luer tip on the syringe and two flanges located at the lumenal end of the female Luer slip of the connecting device. The threads of the syringe's Luer tip accommodate the flanges of the female Luer slip. Rotating the female Luer slip with respect to the syringe mates the two devices. Because the threads and flange hold the Luer slip onto the male Luer tip in a rigid manner, there is less motion and instability between the syringe and the attached device than with the previous by described Luer slip adaptor.
The Luer-Lok adaptor mechanism forms a rigid combination device with a fluid-tight seal. Despite the improvement over the Luer slip adaptor, the Luer-Lok adaptor shares the drawback of allowing only a small-diameter communication between the syringe and the attached device. Moreover, torsional loads will still cause rotation and separation of the adaptor from the syringe. Likewise, sufficient longitudinal and mechanical moment loading will cause the Luer-Lok to pull out of the threaded barrel, thereby separating the devices.
The Luer slip adaptor is relatively weak and routinely fails to maintain a seal during many applications due to mechanical moments, torque, high pressures, or significant temperature changes from room temperature. Also, the Luer design restricts the maximum diameter of fluid communication with the syringe barrel to less than 1 mm. This restricted diameter increases resistance to flow to the fourth power in the reduction of the diameter (Hagen-Poiseuille flow). The small diameter restriction also makes the communication of fluid slurry with semi-solid aggregates with diameters greater than 1.0 mm or a high-density of semi-solids virtually impossible. Finally, an improperly seated Luer will leak fluid and is hazardous to the user due to biocontamination in a medical environment.
Another adaptor is described by Johnson et al, in U.S. Pat. No. 5,002,538, incorporated by reference herein. The Johnson adaptor is designed to duplicate the contours of the syringe tip, shoulder, and barrel. When the Johnson adaptor is inserted over the syringe, the adaptor forms a friction fit with the syringe's tip and barrel. One benefit to Johnson's design is the dual friction fits at the syringe tip and barrel, which create two fluid-tight seals that retard leakage from the assembly. The external friction fit is also an improved mechanism to resist the mechanical moments, axial torques, and longitudinal and shear loading applied during use.
A drawback to the Johnson adaptor is the propensity to lose the friction fit about the syringe barrel, thereby causing fluid leaks, separation of the devices, or creation of a projectile of the adaptor when pressure is applied from within the syringe. Another drawback is the potential for a mechanical misfit between the syringe and the adaptor (e.g., the syringe barrel is too large to fit into the collar of the adaptor or the adaptor is too large to form a friction fit with the syringe), thus rendering the adaptor ineffective. Yet another drawback is the inability to visualize material within the syringe because the adaptor mechanism covers the syringe tip and barrel.
The Johnson adaptor must be manufactured using severe dimensional tolerances; thus its design is ill adapted for mass production. Moreover, when a pressure is applied from within the syringe, the Johnson adaptor is prone to detachment from the syringe barrel and become a projectile. Also, because most syringes are manufactured from plastic and are not entirely uniform in dimension, the Johnson adaptor tends to fit some syringes well while other syringes from the same manufacturer (and even the same production lot) will be too loose or too tight to use. Also, surface debris or liquids can prevent this adaptor from creating a reliable fluid seal. Finally, this adaptor covers one end of the syringe barrel and tip such that visualization the syringe contents is restricted.
Another adaptor design is described by Wells et al., in U.S. Pat. No. 5,759,178, incorporated by reference herein. The Wells adaptor forms an internal and/or external threaded fit and/or groove-fit with the syringe tip. This adaptor claims to use the syringe's shoulder to support “a large amount of torque”. In one embodiment, the Wells device has an external thread that is used to groove the outside of the syringe's tip. In another embodiment, the device has an internal thread for an inside/outside connection.
A drawback to the Wells adaptor is the manufacturing problem of forming inside and outside grooving mechanisms and/or screw threads in close proximity. Another drawback is the inability to adequately clean internal threads on medical devices, leading to an unsterile device. Yet another drawback to the Wells adaptor is the fact that the syringe has been permanently grooved, deformed, or otherwise damaged by the adaptor fixation mechanism (cutting threads or grooving mechanism). Another drawback to the Wells adaptor is that an air pocket can develop between the threads of the adaptor and the material of the syringe tip. This air pocket inside the lumen of the syringe tip can reduce the level of suction or induce total loss of suction during use. Another problem with the Wells adaptor is that it does not allow visualization of the contents of the syringe within the syringe tip.
Despite suggestions to the contrary, the Wells adaptor is subject to detach when a torque-load is applied. Also, the adaptor is difficult to clean and maintain because of its internal and/or external grooving mechanisms. Maintenance issues are critical in the medical industry because unclean instruments are unsterile and can cause or spread infection. Finally, because this adaptor attaches to the syringe tip, it, too, obscures the last couple of milliliters of syringe contents.
Another adaptor is described by Grams, et al., in U.S. Pat. No. 5,919,169, incorporated by reference herein. The Grams' adaptor consists of two pieces: a plug with a proximal internal frustoconical receptacle to receive a syringe tip, a distal threaded receptacle to receive a cannula nose, and a cannula nose having a proximal end that inserts into the distal collar and the lumen of the syringe tip. The plug and cannula nose have mating threads so that once the two are screwed together, the nose presses into the syringe tip and forms a gas-tight and liquid-tight seal. The Grams adaptor forms a friction/compression fit with the syringe's tip.
Significant drawbacks to the Grams adaptor are found in the mechanisms used to fix the plug to the syringe; specifically, an unreliable friction fit or an inconvenient adhesive or “welding” seating and sealing mechanism. If an adhesive or welding technique is used, the syringe becomes permanently changed and cannot be used with other devices. Moreover, in a surgical environment, the Grams adaptor is likely to fall off the syringe due to inadequate friction. An inadequate friction fit can also result in a loss of continuity between the nose and plug or the plug and the syringe or the nose and the syringe. Finally, the Grams adaptor like others described above, also impairs visualization of material within the syringe tip.
The Grams adaptor requires an awkward mounting procedure. Specifically, one must fix the plug to the syringe tip using “welding or other mounting methods”, insert the nose into the syringe tip, and screw the plug/syringe/nose assembly until the threads are mated and the adaptor pinches the syringe tip between the nose and the plug. Also, the Grams adaptor significantly adds to the length of the assembly, thus forming an awkward combination device. Furthermore, the gas and liquid pinch seal can be broken when either a mechanical moment or a torsional load is applied. Both types of loading occur repeatedly in many procedures. The Grams adaptor is also difficult to clean and maintain because of its screw threads. This raises concerns about maintenance, sterility, and product safety. Finally, the Grams adaptor obscures the last couple of milliliters of syringe contents due to its mounting on the syringe tip.
Other adaptor assemblies for connecting syringes to needles, catheters, atomizer nozzles and the like are described in U.S. Pat. No. 3,366,286 (Kloehn), U.S. Pat. No. 4,187,848 (Taylor), and U.S. Pat. No. 6,112,743 (Denton), incorporated by reference herein.
A common problem to all these designs is that each adaptor is particularly configured to fit only one type of syringe, from a particular manufacturer, and thus is incapable of fitting any other brand or size of syringe unless it is specifically redesigned to do so.
As noted, each of these syringe adaptors has significant problems.
None of these adaptors provide for full visualization of the syringe contents or can be applied to more than one type of syringe. Several adaptors are difficult to clean and the fluid-seal for each design is often compromised during normal use. Moreover, none of the related art contains a design that adequately tolerates the mechanical loading expected during use, including torsion, mechanical moment, shear, and longitudinal loads.