Tip protection device

Abstract: A safety cover (60), which securably and reliably prevents the readvancement of the tip of a cannula once it has been retracted thereinto, is designed having an elongate body which includes an axial channel having elements which displace and block linear passage of the cannula once it has been retracted. The displacing element is a spring plate (66) which, when compressed permits the cannula (18) to pass through, but once the cannula has been retracted, expands to prevent the tip from being readvanced.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to stick prevention apparatus for protecting medical personnel from injury. More particularly, the present invention relates to tip covering elements having internal conformations which prevent a retracted needle from reemerging therethrough. 2. Description of Prior Art Medical care of individuals in hospitals, clinics, and other health care facilities often includes the taking of blood samples, intravenous supplying of medication, and the introduction or removal of other fluids via cannulae, needles, or syringes. The present medical environment, in which there exist diseases, for example Acquired Immune Deficiency Syndrome, AIDS, for which there are no cures, and which are transmitted via blood to blood contact, has raised concerns relating to the potential for contaminated "needle sticks". A wide variety of devices have been provided in the prior art for prevention against accidental contaminated "needle sticks". For example, U.S. Patent No. 5,215,528 to Purdy et al. (hereinafter Purdy) teaches an assembly for introducing a catheter into a blood vessel, wherein there is provided a tip cover which includes an elastically deforming L-shaped. In an initial disposition, the L-shaped member is positioned in a deformed state with the cannula inserted fully through the cover. Once the cannula is retracted, however, the L-shaped member springs into a position to prevent reemergence of the needle. Manual repositioning of the L-shaped member is necessary to permit the cannula reemerge from the cover. U.S. Patent 5,127,905 to Lemieux teaches a protection cap, which is similar to the device disclosed by Purdy, as described above. In the Lemieux device an externally mounted rotating L-shaped lever is disposed along the axis of the cover, manual actuation of which by a user once the cannula is retracted prevents the cannula from re-emerging from the cover. Manual retraction of the external L-shaped lever from the path of the cannula permits the cannula to reemerge. U.S. Patent 4,826,490 to Byrne et al. (hereinafter Byrne) teaches a safety cover and syringe assembly wherein an external cylindrical sleeve, through which the cannula extends, is slidably mounted to a track on the external surface of the syringe. Sliding the external cylindrical sleeve relative to the cannula and the syringe, such that the cannula is fully retracted into the sleeve, causes a locking mechanism to engage between the syringe and the sleeve so that the cannula may not be advanced out of the sleeve without disengagement of the locking elements by a user. A device, which is similar to the one disclosed in the Byrne reference, is U.S. Patent 4,952,207 which is also to Lemieux. This reference teaches a safety cover for use with a cannula which has a radial notch along the shaft, near the tip. The internal structure of the cover includes a tab which engages the cannula in the notch once the cannula has been retracted. Rotation of the cannula, or the safety cover locks the cannula in position and prevents its reemergence. As above, however, the Lemieux prevention means may be compromised by intentional, or random, manipulation of the device. While each device includes functional means for preventing "needle sticks" by interfering with the exposure of a cannula once it is retracted into a cover, it is of considerable concern for users of such devices that, if a means for disengaging the retaining element is provided, random forces may expose the contaminated cannula, thus presenting a danger to medical personnel. This concern is especially applicable to the variety of "needle stick" prevention devices which include externally mounted prevention means. WO 96/22800 discloses a safety catheter. A number of embodiments are described in which a cover for locking within it the tip of a cannula includes a body having an interior chamber slidably mountable on the cannula. An axial channel extends through the body and the cannula is slidable in the axial channel. A locking arm is provided in which at least one through hole exists. The cannula extends through the through hole when in a position for use. US 5,053,017 discloses a needle safety device. The device consists of a unitary or multiple piece clip, which is slidable from a first position wherein a hypodermic needle is usable for injection purposes to a second position wherein the sharp end of the hypodermic needle is covered. The clip comprises a front end that is engaged by the cannula to hold it in a compressed position when disposed for use. US 5,344,408 discloses a break-away safety shield for a needle cannula. The shield includes an elongate body having an interior chamber which is slidably mounted on a cannula. An axial channel extends through the elongate body and the cannula is slidable through the axial channel. A spring biased plate is provided which has a forward engaging edge that is engaged by the cannula to hold a spring in a compressed position. Retraction of the cannula causes the forward engaging edge to displace and block the forward movement of the cannula. It is, therefore, a principal object of the present invention to provide a needle cover which includes an element or elements which prevent exposure of a contaminated cannula. It is further an object of the present invention to provide a needle cover which cannot be compromised, whereby the cannula may reemerge therethrough, by application of random environmental forces, or by unintentional manipulation of the device. It is further an object of the present invention to provide a needle cover which is more reliable in its safety aspects. Other objects and advantages of the invention will be more fully apparent from the ensuing disclosure and appended claims. SUMMARY OF THE INVENTION The present invention is directed to a needle cover which includes an axial channel and an interior chamber, through which a cannula may extend as claimed hereinafter. Along this axial channel and/or in the interior chamber, there is provided means for permitting unidirectional translation of a cannula. In an initial disposition, the cannula is fully inserted through the safety cover, with the cannula extending through the axial channel. After the cannula has been used and has become contaminated, the cannula is retracted (or the cover is advanced along the shaft of the cannula) such that the tip is fully within the cover. Once freed from the influence of the cannula, the means for permitting only unidirectional movement are engaged to prevent the cannula from reemerging from the cover. Specifically, a cover element is provided, having an axial channel therethrough, and including an interior chamber. A spring plate, having a forward engaging edge and pair of through holes therein, is mounted to the rear wall of the interior chamber. In an initial disposition, the forward engaging edge is forcibly held against the shaft of the cannula such that the through holes are aligned with the axial channel. The cannula is therefore provided a linear path along which to translate. After use, however, once the cannula is retracted through the axial channel, and backed into the interior chamber, the forward engaging edge of the spring is released. The expansion of the spring forward causes the through holes therein to become partially misaligned, therein gripping the shaft of the cannula. The cannula is thereby prevented from advancing by the grip of the holes in the spring plate as well as the forward engaging edge which is positioned in front of the axial channel, thus preventing the advance of the cannula. BRIEF DESCRIPTION OF DRAWINGS Figure 1 is a side view of a medical assembly including a catheter, a cannula, a syringe, and the safety cover of the present invention. Figure 2 is a side cross-section view of an aspect of the present invention including a spring plate, disposed in its initial compressed position with the cannula positioned therethrough. Figure 3 is a side cross-section view of the aspect of the present invention shown in Figure 2, wherein the cannula has been retracted and spring plate has advanced, thereby preventing the cannula from advancing. DETAILED DESCRIPTION OF PREFERRED EMBODIMENT This invention relates to the field of hypodermic needles and most particularly to devices for inserting catheters into blood vessels. Referring now to the drawings, Figure 1 shows a catheter insertion apparatus 10 having a safety cover 20. The apparatus 10, which is shown in a side view, includes a syringe body 12, with an annular ring 14 at the base thereof, and a standard slidable plunger element 16 which translates within the syringe body 12. A cannula 18 extends axially outward from the annular ring 14; the narrow hollow internal passage within the cannula 18 providing a connection from the internal volume of the syringe body 12 to the exterior, through which fluids may flow. The cannula 18 extends outward from the annular ring 14, through a safety cover 20. The safety cover 20, is constructed so that the cannula 18 may be inserted axially therethrough and so that the cannula 18 and the safety cover 20 may be translated relative to each other. In the embodiment shown in Figure 1, the apparatus 10 further includes a catheter 25. The catheter 25 includes an elongate narrow, flexible, tube section 24, through which the cannula 18 is disposed prior to the catheter being inserted into the patient. The catheter 25 further includes a hub 22 having a widened receiving port 26, in which a portion of the safety cover 20 is initially nested. The nested portion 21 of the safety cover 20 is shown in phantom. The cannula 18 therefore extends outward from the annular ring 14 of the syringe body 12, sequentially through the safety in which the safety cover 20 is initially nested, the widened receiving port 26 of the catheter hub 22, and ultimately through the elongate narrow flexible tube section 24. In use the cannula 18 is disposed through the narrow flexible tube section 24, to enable puncturing and insertion of the flexible tube 24 through the skin of a patient, and positioning of the tube 24 into the desired blood vessel. If properly positioned in the blood vessel, the user withdraws the cannula 18 from the patient without removing the catheter element 22, therein providing an open conduit through which the medical care provider may draw blood, or input appropriate medication directly to the vasculature. The process of removing cannulae from patients and decoupling syringes and cannulae from their corresponding catheter elements, in apparatus of the prior art, exposed the medical care providers to the sharp tip of the cannula which had been contaminated by the patient's blood. In the present invention, the receiving port 26 of the catheter element 22 and the external surface of the safety cover 20 are releasably mated in the initial disposition of the apparatus 10. During extraction of the syringe 10 and cannula 18, the safety cover 20 and the receiving port 26 remain coupled until the tip of the cannula 18 is fully retracted into the safety cover 20. Once the tip of the cannula 18 is fully retracted, the safety cover 20 is released from the catheter element 22. A variety of mechanisms for releasably holding the safety cover 20 to the receiving port 26 of the catheter hub 22 are shown in the art, any one of which may be employed in the present assembly. Such releasable couplings may be manually actuatable or automatically actuated by the retraction of the tip of the cannula 18. Referring now to Figures 2 and 3, a side cross-section view of the present invention is provided, wherein the safety cover 60 is shown having the cannula 18 in its initial, fully inserted position through the axial channel 62. With respect to Figure 2, a cover element 60 is provided, having a linear axial channel 62 therethrough which includes an interior chamber 64. A spring plate 66, having a forward engaging edge 68 and pair of through holes 70a,70b therein, is mounted to the rear wall 72 of the interior chamber 64. In an initial disposition, the spring 66 is compressed by virtue of the fact that the forward engaging edge 68 is forced upward to rest against the shaft of the cannula 18. The through holes 70a,70b of the spring plate 66 are aligned under the compression described above. The cannula 18 is therefore provided a linear path along which to translate. Referring now to Figure 3, after the cannula 18 has been used, it is retracted through the axial channel, and the tip 116 is drawn back beyond the forward engaging edge 68 of the spring 66. Once the positioning influence of the cannula 18 is removed, the edge 68 and spring 66, are permitted to advance downward and forward. The expansion of the spring 66 causes the through holes to move relative to the axial channel 62 of the safety cover, therein becoming partially misaligned. In this partially misaligned position, the rims 71a,71b of the through holes 70a,70b, respectively, grip the shaft of the cannula 18, locking the cannula in position. In addition, the forward edge 68 moves into a blocking position in front of the forward portion of the axial channel 62 of the safety cover. The cannula 18 is thereby prevented from advancing by the grip of the holes 70a,70b in the spring plate 66 as well as the forward engaging edge 68 which is positioned in front of the axial channel 62, thus preventing the advance of the cannula. While there has been described and illustrated specific safety covers for preventing accidental "needle sticks" with contaminated needles, it will be apparent to those skilled in the art that variations and modifications are possible without deviating from the broad spirit and principle of the present invention which shall be limited solely by the scope of the claims appended hereto.

Claims: A safety cover (20,60) for locking the tip of a cannula (18) therein, comprising: an elongate body having an interior chamber (64), slidably mountable on said cannula (18); an axial channel (62) extending along the entire axial length of the elongate body, from a forward portion of the body, through said interior chamber (64) and through a rearward portion, said cannula (18) being slidable therethrough; and a spring plate (66) having a forward engaging edge (68) which is engaged by said cannula (18) to hold the spring in a compressed position, such that the retraction of the tip (116) of said cannula (18) causes the forward engaging edge (68) to displace; characterised in that : the spring plate (66) is mounted to and extends from a rear surface (72) of said interior chamber; extends the spring plate (66) has a pair of through holes (70a,70b) for receiving said cannula (18) therethrough when said spring is compressed; the retraction of the tip (116) of said cannula (18) causes the forward engaging edge (68) to displace while said cannula (18) is still displaced through both through holes (70a,70b), and the retraction of the tip (116) of the cannula also causes the through holes (70a,70b) to displace; and the displacement of the forward engaging edge (68) prevents subsequent advance of said cannula (18) fully through said safety cover. The safety cover (20,60) of claim 1, wherein the spring plate (66) is fixably mounted to a rear surface (72) of said interior chamber (64). The safety cover (20,60) of claim 1 or claim 2, wherein the displacement of the through holes (70a,70b) is from a first position in which the through holes are aligned to a second position in which they are partially misaligned and thus grip the cannula (18) disposed therethrough, to prevent subsequent advance of the cannula. The safety cover (20,60) of any preceding claim, wherein the displacement of the through holes (70a,70b) causes rims (71a,71b) of the through holes to frictionally engage the cannula (18).

Inventors: BOGERT DAVID L, BROWN HERBERT, SUTTON THOMAS K, BOGERT, DAVID L., BROWN, HERBERT, SUTTON, THOMAS K.
Applicants: JOHNSON & JOHNSON MEDICAL, JOHNSON & JOHNSON MEDICAL, INC.
Application year: 1996
Main classification: A61M5
IPC codes: A61M5, A61M25