Abstract:
A needle stick protecting device slideably mounted over medical needles having pointed tips, comprising at least two clamping members sliding over the needle shaft and joined together at their proximal end, automatically arresting in proximity of the needle tip upon passage of triggerng means beyond the needle tip, said triggering means projecting toward the needle from said clamping members. Said clamping of said clamping member on the needle shaft is bi-directional, as it occurring both in response to application of a force for forward sliding of the guard toward the needle tip and in response to a force applied to withdraw said guard from the needle tip. Another relevant feature of the device is the negligible friction opposed by said guard to forward sliding motion, said friction being variable and proportionally dependent to the force applied for forward sliding motion.

Description:
RELATED CASES 
     This application is a continuation-in-part of our prior patent application, Ser. No. 08/219,373, filed Mar. 29, 1994 and now abandoned. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to protective devices for health care workers. More specifically the present invention relates to devices which protect health care workers from accidental punctures due to pointed needles of medical devices. 
     BACKGROUND-DESCRIPTION OF PRIOR ART 
     Pointed needles of medical devices, either hollow or solid represent a real hazard to health care workers. Besides causing puncture wounds which carry the risk of infection of skin and deeper structures such as the subcutaneous tissue, the fascia, the muscle and bone, they can transmit multisystem diseases to the health care workers victim of accidental exposure. Numerous are the diseases that have the potential to be transmitted via accidental sticks: hepatitis, malaria, syphilis and, the most frightening of all, AIDS. Risks of transmission are inherent to the medical profession and strict prevention guidelines cannot eliminate the hazards completely. The only successful way to avoid accidental exposure is to provide all the medical devices having pointed needles with protective mechanisms which safely shield the pointed needles from accidental exposures. 
     A search in the patent office has revealed numerous protective devices for the exposed needle tip of medical devices. Two are the basic mechanisms of protection applied to medical needles. 
     In one type of devices the needle is retracted and enclosed within a protective shield either manually or by resilient means. 
     In the other type of devices a protective sleeve or guard is advanced manually or by resilient means over the needle enclosing the needle as a whole or enclosing just the pointed tip. Various are the mechanisms described for achieving the locking of the sleeve or guard in respect to the needle and various are the needle tip shielding mechanisms in either group of devices. 
     While our search revealed many protecting mechanisms in which the needle guard is a part of the housing of the medical device to which the needle is applied to, or is simply connected to, we found only two patents, U.S. Pat. No.4,929,241 issued to John Kully and Patent Cooperation Treaty application No. PCT/CA 90/00031, published on Aug. 9, 1990 under International Publication No. WO 90/08564 issued to Inventor Robert Sircom, in which the protecting mechanism is a separated unit, i.e. with no attachment of any sort, from the medical device to which the needle is applied. In U.S. Pat. No.4,929,241 issued to Kully, a medical needle puncture guard is described in which a small protective guard slides over a medical needle. The front portion of the device comprises two jaws which collapse in front of the needle tip, once the needle tip is passed, to form a barrier in front of the needle tip. Arrest of the jaws in front of the needle tip is accomplished by two distinct mechanisms: anterograde arrest is accomplished by two opposing sharp blades projecting inward toward the needle shaft from the jaws, both obliquely and anteriorly oriented, exerting pressure on the needle shaft to the point of arresting its forward sliding motion impeding further advancement, once the transverse shields of the jaws have passed the needle tip. 
     Retrograde arrest is accomplished by the transverse barrier resulting from the collapsing of the transverse shields, as shown in FIG. 1, of the above cited U.S. Pat. No. 4,929,241 of the opposing jaws in front of the needle tip. The two jaws which collapse in front of the needle tip are each secured to mounting means. Collapse of the opposing jaws in front of the needle tip and arrest of the guard to forward motion by the opposing blades exerting arrest pressure over the needle shaft is necessarily accomplished by the resiliency of the jaws, said jaws urging opposed transverse shields  24  and  26  and opposed arresting blades to close on the needle shaft. 
     An unavoidable consequence of such concept is that the arrest to forward motion of the needle guard relies exclusively upon the degree of the pressure exerted by the opposing arresting blades upon the needle shaft, such degree of pressure on the needle shaft being dependent upon the degree of resiliency of the jaws to which said blades are secured. If such degree of resiliency is insufficient, then the needle guard will not arrest in proximity of the needle tip and the needle guard will inevitable fall off the needle defeating the purpose of the device, unless of course, modifications to the surface of the needles currently in the market are made, as for instance an arresting step, modifications which besides not being disclosed in such patent publication, do not appear to be reasonably practical. 
     The requirement for a resiliency of a sufficient degree to enable arrest to forward motion by the opposing arrest blades exerting pressure upon the needle shaft results in the drawback, inherent to the concept of the art disclosed by Kully, that also the transverse shields will inevitably be subjected to the same degree of resiliency which urges the opposing arresting blades to close together on the needle shaft because, alike arresting blades, transverse shields are secured to the same resilient jaws. As a result of the significant resiliency which transverse shields are subjected to while sliding forward along the needle shaft, the dynamic resistance and friction of the guard to forward sliding motion is also significant. In certain applications, such degree of friction is undesirable and in others it limits the usefulness of the device. More important than that, it appears that the needle guard disclosed by Kully does not guarantee an arrest to forward sliding motion of the guard, in fact, if the operator of the device advances the guard rapidly and forcefully, the guard may exit from the tip of the needle without arresting in proximity of the needle tip, unless the centripetal forces of the blades on the needle shaft is so impractically relevant to interfere with smooth and unopposed sliding of the guard over the needle. As a matter of fact, the arrest of the guard in the cited patent by Kully occurs as a probable event dependent upon the degree of centripetal force continuously exerted by the opposing blades during the slide motion of the guard on the needle shaft by resilient jaws. 
     Patent Cooperation Treaty application No. PCT/CA 90/00031, published on Aug. 9, 1990 under International Publication No. WO 90/08564 issued to Inventor Robert Sircom discloses a needle guard in which arrest to forward motion of the needle guard is accomplished by a locking plate having an orthogonally formed passageway for the needle shaft, said plate being orthogonally angled in respect to the longitudinal axis of the needle when being advanced along the needle, said orthogonally angled position being maintained by a sensing plate connected to the locking plate through an arm named canting lever. Contact of the sensing plate on the needle shaft is maintained by a spring arranged to secure such contact. Upon passage of the needle tip, the arm named canting lever, no longer retained in its position by the sensing plate sliding over the needle shaft, is driven further toward the needle by the spring causing canting of the locking plate in respect to the needle shaft. Said canting of the locking plate causes arrest of the plate by gripping exerted on the needle shaft by the sharp edges of the passageway formed in the locking plate in two points along the needle shaft in proximity of the tip opposite although not equidistant from the needle tip. 
     The locking mechanism of gripping type disclosed above provides a type of arrest of the needle guard on the needle shaft in proximity of the tip only in response to forward sliding motion of the guard over the needle. Backward sliding motion of the needle guard, i.e. withdrawal of the needle guard along the needle and exposure of the needle tip, is prevented, as in the case of Kully&#39;s patent, by the presence of a front plate, named sensing plate, collapsed just in front of the needle tip as in the Kully patent. 
     The presence of the spring disclosed by Sircom constitutes a significant drawback due to the friction caused by said spring urging the sensing plate against the needle shaft. As in the case of Kully&#39;s patent, such friction is constant regardless of the degree of force applied for forward sliding motion of the guard on the needle. Faster forward sliding motion will not increase the contact force and friction upon the needle shaft by the sensing means in either patent with resulting diminished reliability of the device in timely responding with self-arrest in proximity of the needle tip. 
     Our patent search has revealed that no known patent describes the mechanism of needle stick protection that we describe here in the present application. 
     BRIEF SUMMARY AND OBJECTIVES OF THE INVENTION 
     It is an objective of our invention to provide medical needles, either solid or hollow, with a simple, safe, effective mechanism of shielding. 
     Is is another object of our invention to provide medical needles with a type of protective mechanism capable of performing equally in needles of various type regardless of size, length, shape or structure of the needle. 
     It is an object of our invention to provide the operator with a compact easily to assemble and easy to operate needle stick protector. 
     Our invention describes a needle protective mechanism consisting of a protecting guard slideable over a medical needle, said needle guard being capable of self arrest and irreversible locking once the needle tip is passed beyond the front portion of the device, shielding so irreversibly the needle tip from accidental exposures. The locking mechanisms are automatically actuated once the device reaches the tip of the medical needle. 
     Both anterograde and retrograde sliding motion of the guard over the needle is accomplished by a clamping action upon the needle shaft. Attempts to dislodge the guard from the tip of the needle by a forwardly directed sliding force as well as by a backwardly directed sliding force will result in a further increase of said clamping action on the needle shaft. Therefore the higher the degree of force applied to dislodge the guard from the needle tip, the more firmly the needle guard will clamp to the needle tip, rendering attempts of dislodging the guard virtually impossible and the needle tip protection very reliable, as it should be. 
     Our application describes a device composed of a housing generally of cylindrical shape in which clamping members are enclosed. The triggering of the arrest and locking of the clamping members over the needle upon sliding of a portion of the device along the needle tip is achieved automatically, and is actuated by one or two triggering means. 
     In our application, the arrest occurs inevitably and irreversibly as a result of application of external forces specifically applied by the operator upon the housing of the device, said forces being exerted by the operator in parallel direction to the needle shaft. Such forces, parallel to the longitudinal axis of the needle, will suddenly change direction from parallel to centripetal toward the needle once the front portion of the device is advanced beyond the needle tip, causing an irreversible arrest and locking of the device on the needle. 
     Furthermore increasing the force driving the guard beyond the needle tip will further strengthen the arrest and locking mechanism, the opposite in respect of the patents cited in which pushing further and stronger will increase the probability of exit of the guard beyond the needle tip with resulting failure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a longitudinal cross section of the device mounted over the medical needle in position of rest with the clamping mechanisms prior to actuation. 
     FIG. 2 is a view of the device of FIG. 1 shown in an advanced position in respect to the needle with the clamping mechanisms at an early stage of actuation. 
     FIG. 3 is a view of the device of FIG. 1 with the clamping mechanisms in a further stage of actuation. 
     FIG. 4 is a view of the device of FIG. 1 with the clamping mechanisms fully actuated. 
     FIG. 5 is a view of an alternative version of the device of FIG. 1 in a stage prior to actuation of the clamping mechanism. 
     FIG. 6 is a view of the device of FIG. 5 with the clamping mechanism fully actuated. 
     FIG. 7 is a view of an alternative version of the device of FIG. 1 in a stage prior to actuation of the clamping mechanism. 
     FIG. 8 is a view of the device of FIG. 7 with the clamping mechanism fully actuated. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In that form of the present invention chosen for the purpose of illustration in FIG. 1 a needle stick protecting device generally indicated at  1 , is shown comprising housing means  2  generally of hollow cylindrical shape concentric to and slideable over a medical needle  4  and clamping members  35  encircling needle  4 . Housing means  2  is composed of body  3  and of a front portion  16  assembled together via mating thread  40  and  41 . Body  3  of housing means  2  has base  10 , with at its center opening  12  for passage of medical needle  4 , cylindrical side walls  14 , generally parallel to needle shaft  6 , and slanted wall  20 , starting at housing interface means or flange  11  for engagement with corresponding flange or clamping interface means  23  of clamping member  35  as it will be described below. Front portion  16  of housing means  2 , with at its center passageway  18  for needle  4 , has slanted wall  22  and circular latches  5  or latch means or locking means backwardly projecting from anterior wall  17  of said front portion  16 . Said latches  5  have a slanted surface  13  for engagement to tip  37  of clamping members  35  as it will be described below. 
     Needle  4  is composed of a shaft  6  and a tip  7 . 
     Clamping means  9  is composed of two symmetrically opposed identical clamping members  35  at opposite site of needle shaft  6 . Each clamping member  35  of clamping means  9  is composed of proximal or posterior arm  26  and of anterior or distal arm  28  connected at obtuse angle in respect of each other. Each posterior arm  26  of clamping member  35  has, proximally, a posterior segment  33  with posterior end  31  and with clamping surface  30  for engagement with needle shaft  6 , a semiannular indentation or groove  29  for O ring  8 , and has flange  23  on its outer surface  24  for engagement to corresponding interface means  11  of body  3  of housing  2 . Such flange  23  projects from proximal arm  26  at suitable angle from said proximal arm to convert the majority of the force applied by interface means  11  into forward sliding motion and a small fraction of said force into a force inducing contact of triggering means  32  upon needle shaft  6 , as it will described below. 
     Anterior or distal arm  28  of clamping members  35  has a portion of its length  32  in slideable contact with needle shaft  6 , said portion being adapted as triggering means  32  of mammillary shape or triggering means or mammilary bodies, projecting from inner surface  36  of clamping members  35  and tip  37  for wedged engagement with latches  5 . 
     With the device in a position of rest, triggering members  32  are in sliding contact with needle shaft  6 . 
     Description of Operations 
     In FIG. 2, the needle guard  1  is shown while being slided forwardly. Needle guard  1  may be either advanced manually by the operator or by resilient means. Advancement is extremely smooth and requires minimal thrust as friction is negligible as housing means  2  forwardly thrusted by the operator is acting upon the very proximal segment of each proximal arm  26  of clamping members  35  via interface means  11 . In fact, as housing means  2  exerts its force via interface means  11  acting upon flange  23  on the very proximal segment of proximal arm  26  of clamping members  35 , the centripetal component of the forward thrusting force is greatly reduced to almost a negligible factor. 
     The described system is the equivalent of a lever system in which the acting force is applied close to the fulcrum of a lever. In FIG. 2 the lever is represented by proximal arm  26  of clamping members  35 , the fulcrum is represented by the proximal end  31  of proximal arm  26  and the point of applied force is the flange  23 . 
     Friction of triggering means on needle shaft is even further lightened by the angle of flange  23  on proximal arm  26  of clamping member  35 , said angle resulting in a surface of suitable inclination being opposed to the corresponding interface means  11  of housing  2  to convert the majority of the force applied by interface means  11  into forward sliding motion and only a small fraction of said force into a force inducing friction by sliding contact of said triggering means  32  upon needle shaft  6 . 
     Triggering means or members  32  of clamping members  35  will exert only a negligible force resulting in a negligible friction over needle shaft  6  during the advancement by sliding motion of device  1  over needle  4 . Remarkably, no additional active forces, in particular no resilient means need to assist triggering means  32  in maintaining their sliding contact with needle shaft  6 . In Applicants invention, the force resulting into friction will only increase when a fast sliding motion of the guard along the needle shaft is exerted upon the guard: such a correlation of contact force of triggering means  32  upon needle shaft  6  with the applied force for forward sliding motion is an appropriate and a desired correlation which enhances the reliability of the device in clamping rapidly in response to triggering, adapting to different forward sliding speeds. 
     Upon passage of the triggering means  32  beyond needle tip  7 , triggering means  32 , no longer maintained far apart or open by the presence of the needle shaft, will be permitted to close, i.e. to slightly converge one toward the other by the slight force applied to flange  23  of clamping members  35  by interface means  11 . The slight converging of the triggering means will result in tilting of the clamping members  35  from which the triggering means  32  are projecting. As shown in FIG. 2, such tilting of clamping members  35  will allow disengagement of the flange  23  from interface means  11 . As a result of such disengagement, as shown in FIG. 3, interface means  11  will act upon outer surface of clamping members  35  causing conversion of the whole applied force into a force resulting into a clamping of said clamping members  35  upon said needle  4  via clamping surface  30 . 
     Tip  37  of clamping members  35 , as shown in FIG. 3, are shown in an early stage of wedging engagement with circular latches  5  of front portion  16  of housing  2 . In FIG. 4 such wedging engagement of tip  37  of clamping members  35  is completed and any attempt to backwardly dislodge the guard from the needle tip will result into a further strengthening of the clamping action of clamping members  35  upon needle shaft  6 . Such wedged engagement of tip  37  of clamping members  35  with latches  5  will result, therefore, in an irreversible locking of the needle guard over the needle tip, effectively shielding so the needle tip from accidental exposures, not allowing the exit of needle tip  7  from passageway  18  of housing  2 . FIG. 2 illustrates tips  37  at the beginning of their movement away from latch  5 , while FIG. 3 illustrates tips  37  at the end of such movement. When moving distally to latch  5 , tips  37  gradually approximate to each other as a result of the action of flange or interface means  11  of housing means  2  upon outer surface  24  of proximal arm  26  of clamping members  35 . In fact, body  3  of housing means  2  is moved relatively to needle  4  in direction of arrow  90  represented above device  1 , moved either by the hands of the operator of the device or by a resilient means. As a consequence of that movement of body  3  of housing means  2 , flange  11 , which belongs to body  3  of housing  2 , will also move relatively to needle  4  in direction of arrow  90 . As represented in FIG. 3, flange  11  has also moved in direction of arrow  90  relatively to clamping members  35  which conversely, by clamping upon needle  4  with their surface  30 , will not be allowed to move relatively to needle  4 . 
     Once tips  37  of clamping members  35  are fully approximated to each other as shown in FIG. 3, tips  37  will not be allowed to open or diverge from their fully approximated position when moving proximally to latch  5  for the reason described below. 
     When housing means  2  are moved in the direction represented by arrow  91  above device  1  of FIG. 4, latch  5 , which belongs to housing means  2 , will move proximally to tips  37 , i.e. tips  37  move proximally to latch  5 . When tips  37  move proximally to latch  5 , clamping members  35 , and therefore their tips  37 , will remain in their reciprocal position, i.e. they will not be allowed to diverge, because, as shown in FIG. 4, O-ring  8 , which seats in groove  29  of clamping members  35 , will be forced to slide distally within groove  29 , toward the tip of the needle, as best shown in FIG. 4, due to radial expansion of posterior segments  27  of groove  29  resulting from the posterior diverging of posterior segments  33  of proximal arms  26  of clamping members  35 , said diverging resulting in turn from the tilting of clamping members  35  produced when housing means  2  are moved in direction of arrow  90  represented above device  1  of FIG. 3, after clamping members  35  have reached needle tip  7 . Radial expansion of posterior segment  27  of groove  29  occurring when clamping members  35  are being closed, necessarily results, as shown in FIGS. 3 and 4, in some constriction of the needle shaft, because, in a stage when clamping members  35  are sliding along the needle, clamping surface  30 , which, as shown in FIG. 1 is generally flat and parallel to needle shaft  6 , is kept in close contact with the needle by O-ring  8 , again as shown in FIG.  1 . Said radially expanded posterior segment  27  of groove  29  prevents O-ring  8  from being displaced backward within groove  29  because said expanded posterior segment of groove  29  would no longer fit within O-ring  8  internal diameter. As a result of that, clamping members  35  will remain closed, and their tips  37  will remain approximated even after flange  11  is removed from clamping members  35 . Therefore, when moving proximally to latch  5 , tips  37  will have no other alternative than following the path of entering inside latch  5 . 
     FIGS. 5 and 6 show an alternative form of the device of FIGS. 1 to  4 . Said alternative form  1 ′ of the device is essentially identical to device  1  of FIGS. 1 to  4 , except for the type of interface means or latch  56  or latch means or locking means of housing  60  on side wall  14  of housing means  60  and for corresponding interface means or latch  58  or latch means or locking means of clamping members  50 . Indeed in this version of the device, a single structure has the dual function of interface means and locking means. Clamping members  50  are composed of proximal or posterior arm  52  and of distal or anterior arm  54  connected at obtuse angle in respect of each other. Triggering means  32  are projecting from inner surface  53  of distal arm  54  of clamping member  50 . Housing means  60  has anterior segment  62  with opening  64  for passage of needle  6 . In such alternative form, latch  58  is formed in the outer surface of the clamping members  50 . 
     Description of Operation 
     In use, the device is operated as the device of FIGS. 1 to  4 , however, engagement of interface means  56  with flange  58  in this alternative form prevents release of the clamping of the clamping members  50 . 
     FIGS. 7 and 8 show an alternative form of device  1  of FIGS. 1 to  4 . This alternative form  1 ″ of the device is similar to device  1  of FIGS. 1 to  4  except for a few differences which are outlined below. 
     Anterior or distal arms  28 ′ of clamping members  35 ′ of clamping means  9 ′ have distal segments  50 ′ projecting inwardly at an angle from anterior or distal arms  28 ′. Distal segments  50 ′ are formed with resilient interlocking latches or hooks or means  52 ′ and triggering means  54 ′. Mammillary bodies  32  are no longer present in anterior arms  28  of clamping members  35 . Distal segments  50 ′ of anterior arms  28 ′ are with the device in position of rest in slideable contact with needle shaft  6  via triggering means  54 ′. Front portion  16  of housing means  2  is no longer formed with circular latches  5 . 
     Description of Operation 
     The device  1 ″ is operated as device  1  of FIGS. 1 to  4 . Needle guard  1 ″ is slided along needle shaft  6  of needle  4  from a position distal to tip  7  toward tip  7  either manually by the operator or by resilient means. During the advancement by sliding motion of device  1 ″ over needle  4 , triggering means  54 ′ of clamping member  35 ′ will exert only a negligible pressure upon needle shaft  6 , resulting in a negligible friction on needle shaft  6 . The operational steps for device  1 ″ are the same as for device  1  of FIGS. 1 to  4 . Upon passage of triggering means  54 ′ beyond needle tip  7 , clamping members  35 ′, no longer maintained open by triggering means  54 ′ in slideable contact, and at opposite sites, of needle shaft  6 , will be permitted to close. 
     Closing of clamping members  35 ′ upon needle shaft  6  will result with clamping action on needle shaft  6  through clamping surface  29  of clamping members  35 ′. The clamping action of clamping members  35 ′ will not only prevent exiting of the needle guard from the needle by preventing further sliding of the clamping members in the direction the needle guard was being moved, but it will also prevent sliding in the opposite direction of the clamping members. 
     Upon closure of clamping members  35 ′, hooks  52 ′ will reciprocally by first coming to reciprocal sliding contact and reciprocally displacing each other as a result of said sliding contact, then returning to resting position as a result of their resiliency when clamping members  35 ′ are fully closed. The return to resting position of hooks  52 ′ upon closure of clamping members  35 ′ will result with an irreversible interlocking of clamping members  35 ′ in closed position. 
     The irreversible interlocking of clamping members  35 ′ in closed position thereforel results in a bidirectional self-arrest of needle guard  1 ″ on the needle, i.e.the needle guard will be automatically prevented from sliding in either direction along the needle and will provided an effective needle shield for accidental needle stick injury.