Abstract:
A surgical safety scalpel having a handle, a blade fixed at one end of the handle, and a sheath slidably and inseparably attached to the handle. The sheath slides lengthways along the handle alternating between a blocking position in which the sheath covers the blade, and a ready position in which the blade is exposed and the sheath forms part of the grip. An aperture in the sheath and two stoppers on the handle form an interlocking mechanism for maintaining the sheath in the blocking position, and a third stopper on the handle prevents the sheath from sliding off the handle in the ready position.

Description:
FIELD OF INVENTION 
     This invention relates generally to surgical scalpels and, more particularly, to surgical scalpels having sheaths or guards to cover the scalpel blade when not in use. 
     BACKGROUND OF THE INVENTION 
     In a world prevalent with AIDS epidemic and Hepatitis B and C epidemics, accidental needle sticks and scalpel cuts have become a major concern to health-care workers. According to a study, the conversion rate for HIV positive needle sticks is 1 in 250 sticks. The conversion rate for scalpel cuts is unknown but according to a study of 10,000 health care workers, it is believed that the conversion rate is higher (as per U.S. Pat. No. 5,342,379). It is well known and understood by healthcare workers that sharp surgical instruments, such as scalpels, have a significant potential for harm to healthcare workers. The rapid handling of these sharp instruments can lead to accidental cuts or puncture wounds during surgery. 
     Thus, there is an inherent incentive for improvement in scalpel technology that can reduce and more ideally eradicate scalpel cuts to the health care worker. The chance of a healthcare worker contracting a fatal infection or disease because of an accidental scalpel cut comes with a heavy price on society and healthcare. The scalpel has not had many basic changes made in the past 100 years other than disposable blades and micro-surgical sizes. 
     Typically, most scalpel cuts or stabs occur in specific situations, such as a surgery. One occasion is at the time of passing a used scalpel to a scrub nurse. Another is when a surgeon swabs a bleeder and accidentally stabs himself (when he forgets that the scalpel is in his other hand). Trauma cases are another high risk situation in which an accidental laceration can occur because there many people simultaneously working on these cases and people are rushing to perform their tasks. Yet another case of accidental stabs is that if the blade sheath is lost or misplaced, the scalpel becomes dangerous for practically anyone and everyone in the proximity of the exposed scalpel blade. Another instance is during the disposal of medical waste, stabbing may occur because of accidental removal of the blade sheath. During the course of a surgery, the healthcare worker will usually remove the sheath and give the exposed scalpel blade to the doctor. Similarly after completion of the use of the scalpel, the surgeon may hand the exposed scalpel blade to the healthcare worker for covering. This process results in loss of time and may cause accidental stabbing of the healthcare worker or the surgeon. During waste disposal, the disposer is not always careful in handling the waste and may handle the waste roughly, which may result in removal of the sheath (if not already detached) and cause stabbing. This could also lead to spread of infection in the general public. Thus, there is a need to protect the healthcare workers from accidental scalpel stabs 
     To address this issue, in recent years, scalpels with disposable blade portions have been made. In this type of scalpel, the blade component is detachable from the handle component and disposed of by deposit in a special container. It will be appreciated, however, that such disposal of blades still presents a hazard to the individual who must detach and transfer the blade component. 
     Similarly, blade sheaths have been developed to cover the scalpel blade when the scalpel is not in use. While early blade sheaths did help reduce the potential for accidental cuts or puncture wounds, there were some problem areas. For example, safety scalpels are known that have a retractable external sheath, but they require two hands to operate. Some of the blade sheaths are awkward to operate. Others include complex mechanical mechanisms to move the sheath, which mechanisms could be prone to mechanical failure. 
     Attempts have been made to sheath the blade in the knife itself by providing a hollow handle component with a slidable blade therein. Basically, these instruments employ the handle component as a sheath for the blade component when not in use. Typically, such sheathable blade assemblies are not contemplated for disposal after a single use. Furthermore, such cutting instruments do not provide a positive means for preventing the unsheathing of the blade portion by a careless handler when disposal of the blade is desired. 
     Therefore, it is an object of the invention to provide a surgical scalpel assembly that reduces the complexity of prior known scalpel devices and which also provides additional safety and manufacturing benefits over known scalpel systems. 
     SUMMARY OF THE INVENTION 
     One embodiment of this invention is a surgical safety scalpel comprising a scalpel handle with a provision to removably attach a disposable scalpel blade at one end, and a longitudinally moveable blade sheath on the handle. The sheath is securely attached to the scalpel handle and entirely covers the scalpel blade in a closed and protective state or blocking position. The sheath can be made to slide towards the tail of the scalpel handle and lock on the central part of the scalpel handle when the scalpel blade is in its exposed state or ready position. The sheath is a hollow body that locks on the scalpel handle by apertures provided on the distal end of the sheath, which apertures interlock with the stoppers at the proximal end of the scalpel handle near the stem of scalpel blade when the sheath is in the blocking position. The first stopper prevents the sheath from sliding beyond the blocking position and detaching from the handle. When the sheath is in this blocking position, the second stopper prevents the sheath from sliding down over the handle by radially exerting force on to a distal end of the sheath. The second stopper is placed inside a recess on the handle and projects outwards. The second stopper has a flexible nature and exerts outward force. When the sheath is in blocking position the outward exerted force keeps the sheath in such blocking position. When the sheath is in the ready position the tail stopper prevents the sheath from sliding off the distal end of the handle. The aperture may have a small projection inside the aperture extending parallel or substantially parallel to the handle, which projection interlocks with the first stopper in the blocking position. The sheath has a grip on the sheath surface to assist in transitioning the sheath from ready position to blocking position over the blade and provide traction for the user. 
     The scalpel blade can be simply covered with the sheath by using one hand and more particularly one digit of the hand holding the scalpel to slide the sheath over the blade. The scalpel blade is covered by the sheath with a shift of the thumb. This covering can be affected after each cut has been made. The sheathing is a smooth single hand operation without any risk of cutting oneself. 
     An object and advantage of the invention is to provide a safety sheath for the scalpel blade wherein the sheath forms an integral and inseparable part of the body of the scalpel. 
     Another object and advantage of this invention is that the sheath does not need to be removed from the scalpel blade during surgery, 
     Yet another object and advantage of this invention is the locking of the sheath on the body of the scalpel so that the sheath cannot be removed from the scalpel body easily or accidentally. A deliberate attempt and a lot of force will be required to remove the sheath from the body of the scalpel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view of one embodiment of the blade and sheath of the present invention together with a scalpel handle. 
         FIG. 2  is a view of one embodiment of the present invention with the sheath in the blocking position. 
         FIG. 3  is a cross-sectional view of one embodiment of the present invention with the sheath in the blocking position. 
         FIG. 4  is a detail view of the interlocking mechanism with the sheath in the blocking position. 
         FIG. 5  is a view of one embodiment of the present invention, with the sheath in the ready position and the blade exposed. 
         FIG. 6  is a cross-sectional view of one embodiment of the present invention in ready position. 
         FIG. 7  is a detail view of an embodiment of the present invention when the sheath is in the ready position. 
         FIG. 8  is a detail view of an embodiment of the present invention when the sheath is in the ready position. 
         FIG. 9  is a detail view of an embodiment of the present invention when the sheath is in the ready position. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , there is shown an exploded view of one embodiment of the scalpel handle, blade, and sheath of the instant invention. 
     In this embodiment, the scalpel handle  1  is of conventional shape and configuration having a distal end  14  and a proximal end  12 . This handle is made of plastic, stainless steel or other suitable material and of such nature that can withstand all types of sterilization ranging from chemical to heat (both dry or wet) or any other sterilization. Typically, the distal end  14  on the tail  9  is relatively thin while the middle portion  11  is somewhat thicker. The proximal end  12  of the scalpel handle generally takes the configuration of an extended nose which is relatively narrow and includes a projection  13  on at least one surface thereof. The projection  13  incorporates a groove  17  for receiving a blade  2 . 
     The scalpel handle  1  can taper in width towards the distal end  14  near the tail  9 . On at least one of the surfaces of the handle  1 , the scalpel handle includes a plurality of surface features including stoppers in the nature of ridges, protrusions, buttons, and combinations thereof; and cavities in the nature of slots, recesses, grooves and combinations thereof, certain protrusions and cavities configured to engage complementary elements on a sheath. In one exemplary embodiment shown in  FIGS. 1-8 , the protrusions include a first stopper  5  in the form of a protrusion, a second stopper  6  in the form of a flexible button, and a tail stopper  8  in the form of a ridge extending across the width of the handle  1 . The cavities on this embodiment include a recess  7  undercutting second stopper  6  to provide means for the second stopper  6  to flex. In other embodiments, the structures of the first, second, and third stoppers may be independently selected from ridges, protrusions, or buttons. 
     Typically, the distal end  14  of the handle  1  is somewhat rounded for convenience. In addition, a shoulder  15  can be provided at the end of the scalpel adjacent to the proximal end  12 . 
     The sheath  3  is also disclosed, having a distal portion which slides along the handle  1  and a proximal portion which extends beyond the proximal end  12  of the handle  1  to cover the blade  2 . While not necessarily limited thereto, the sheath  3  is typically formed of a plastic material such as a conventional polymer material including but not limited to polystyrene, polycarbonate, polyurethane, polyethylene, phenol-formaldehyde resins, polybutylene and the like. The sheath further comprises a base surface  18  configured to engage the second stopper  6  when the sheath is in the blocking position, and to engage the tail stopper  8  when the sheath is in the ready position. 
     As shown in  FIG. 1 , a plurality of substantially parallel, transverse strips  21  are provided across the outer surface of the sheath  3 . These strips (or ridges) can be raised or depressed areas in the body of the sheath  3 . The strips  21  provide additional traction or gripping surfaces for the user of the sheath  3 . 
     An aperture  4  having a square shape is provided through the proximal portion of the sheath  3 . The aperture  4  and the base surface of the sheath are shaped to correspond, cooperate and lock with first stopper  5  and second stopper  6  while the sheath is enclosing the scalpel blade  2 . The second stopper  6  is provided a short distance from the first stopper  5  in a direction along handle  1  towards the distal end  14 . The second stopper  6  limits the movement of the sheath  3  relative to the scalpel handle  1  when in blocking position. 
     A representative blade  2  is shown. The shape of the cutting edge of the blade and so forth are representative only. It is well known that there are many sizes, shapes and styles of scalpel blades. The invention described herein is intended to cooperate with virtually any blade shape. 
     Typically, the blade  2  includes an opening  16  which is configured to cooperate with and engage the projection  13  of the handle  1 . Typically, the projection  13  is inserted into the larger portion of the opening  16  and slid forward to engage the smaller end of the opening  16  in a groove  17  in the projection  13 . When the blade  2  is to be attached to handle  1 , the proximal end  12  of the handle is exposed by sliding the sheath  3  down on to the middle portion  11  of the handle. The projection  13  of the handle  1  is inserted into and mates with the opening  16  in the blade in conventional fashion. The scalpel is now in armed and ready position. 
     To disarm the scalpel without touching the exposed blade  2 , the sheath  3  that is resting on the middle portion  11  of the handle  1  is pushed smoothly from the middle portion  11  over the blade  2  until the sheath  3  completely covers the blade  2 . The forward motion of the sheath  3  is stopped by the engagement of the aperture  4  with first stopper  5  and the base of the sheath  3  with second stopper  6 . The sheath  3  is now locked over the blade  2  in the blocking position, and the blocked scalpel can be kept safely for future use by the healthcare worker. 
     In  FIG. 2 , the middle portion  11  is shown along with the position thereof relative to the sheath  3  when the sheath  3  is in the blocking position. The blade is stored within the sheath  3  for safe and secure handling thereof without a danger of harm to the handler of the blade. 
     Referring now to  FIG. 3 , there is shown by cross section the condition wherein the blade  2  is fully mounted onto the proximal end  12  of the handle  1 . The sheath  3  covers the blade  2  and a portion of the scalpel handle  1 . 
     When it is desired to use the blade, the sheath  3  is withdrawn from the blade  2  by sliding it along the handle  1  to the ready position shown in  FIG. 5 . When the cutting procedure is concluded, the sheath  3  is repositioned over the blade  2  by sliding the sheath  3  back over the blade  2  into the blocking position shown in  FIG. 2 . When the sheath  3  is returned to the position shown in  FIG. 2 , the blade  2  is covered and the scalpel device can be handled in any appropriate fashion without fear of an accidental cut therefrom. 
       FIG. 4  shows a detail view of the locking mechanism of the sheath  3  with the scalpel handle  1 . First stopper  5  engages with the distal portion  19  of the aperture  4 , thereby stopping the sheath  3  from slipping past the scalpel blade  2  after the sheath has completely enclosed and secured the scalpel blade  2 . So that the sheath does not slide down the handle  1  and continues to remain in blocking position, the second stopper  6  prevents the sheath  3  from sliding down by engaging with the base  18  of the sheath  3 . Therefore, the aperture  4 , the first stopper  5 , second stopper  6  and the base  18  of the sheath  3  form an interlocking mechanism to retain the sheath  3  in the blocking position. As can be seen in  FIG. 4 , when the button forming the second stopper  6  is depressed, the base of the sheath can slide over the second stopper while the back edge of the aperture  4  slides over the sloped back surface of first stopper  5 . 
     The second stopper  6  is made of a flexible material. The second stopper  6  can obviously be made of any material that has flexible properties. This second stopper  6  acts as a spring. During ready position of the sheath  3 , the second stopper  6  has radial tension typical of a spring that exerts pressure against the opposing inner walls  20  of the sheath. When the sheath  3  is activated and eventually comes to rest in the blocking position, the second stopper  6  is freed from the inner wall  20  of the sheath  3  and the spring action or the radial tension causes the second stopper  6  to spring outwards. This outward spring movement of second stopper  6  results in providing a retaining means for the sheath  3  to remain in the blocking position. The detail section view in  FIG. 4  best explains the working of this second stopper  6 . In the embodiment depicted, it can be seen that first stopper  5  has an inner face  25  and an outer face  27 , and second stopper  6  has an inner face  26  and an outer face  28 . In this embodiment, the first stopper inner face  25  and the second stopper inner face  26  are opposite each other and substantially perpendicular to a longitudinal axis of handle  1  to positively engage the distal portion  19  of the aperture  4  and the base surface  18  of the sheath  3  respectively, as shown in  FIG. 4 . It can also be seen that the first stopper outer face  27  and the second stopper outer face  28  each slope down to the handle  1 , permitting the sheath to slide when the interlocking mechanism is disengaged, but exert radial outward pressure against the inner walls  20  of the sheath  3  as shown in  FIG. 7 . It can also be seen from  FIG. 4  and  FIG. 7  that stopper  6  is given flexibility by undercutting with recess  7 . 
     Referring now collectively to  FIG. 5  and  FIG. 6  there is shown a view of the sheath  3  and blade  2  mounted on the proximal end  12  of the handle  1 . This view is to explain the construction and working of the scalpel when sheath  3  is in ready position. 
     To attain the ready position shown in  FIG. 5  with the sheath  3  retracted to expose the blade  2  for any suitable cutting purposes or when it is desired to remove the blade  2  from the handle  1 , the sheath  3  is moved away from the blade  2  and onto the middle portion  11  of the handle  1 . It is understood that the blade  2  is securely fastened to the scalpel handle  1  as described above. The sheath  3  is withdrawn along the handle  1  by exerting pressure on the gripping surface comprising strips  21 . Typically, the sheath  3  is operated by depressing second stopper  6 , pulling on the gripping surface using the thumb and index finger or any other finger, and pushing the handle  1  through the sheath  3 , exposing the blade  2 . 
     It can be seen that in the ready position shown in  FIG. 5 , the blade  2  is attached to the handle  1  but is completely exposed and ready for use or already used, as the situation may be. The sheath  3  is in the ready position and is resting on the middle portion  11  of the scalpel handle  1 . The sheath  3  is comfortably mounted on the middle portion  11  of the handle  1  in such a position that the sheath  3  covers a part of the middle portion  11  of the handle  1 , providing a gripping or traction surface for the user. So that the sheath  3  does not slide off the distal end  14  of the handle  1 , the handle is provided with tail stopper  8  on the end proximal to the rounded distal end  14  of the handle. In the exemplary embodiment shown in  FIGS. 5 and 6 , the tail stopper  8  is in the form of a ridge projecting from the surface of the handle  1  which engages the base of sheath  3 .  FIG. 8  shows a detail view of the sheath  3  in the ready position engaged with the tail stopper  8 . In a second embodiment, as shown in  FIG. 9 , the tail stopper  8  is in the form of a recess  23  in the surface of the handle  1  which interacts and mates with projections  22  from inside the inner walls  20  of the sheath  3 . 
     The ready position of the sheath  3  enables the scalpel with blade  2  to be used easily and effectively without any requirement to remove the sheath  3  from the handle  1 . From this position, sheath  3  can be slid into blocking position quite easily at the end of the cutting procedure. 
     To unsheathe the blade  2 , the second stopper  6  is depressed and sheath  3  can be pushed back and downwards over the body of the handle  1 . In this case, the force exerted on the sheath is sufficient to override the restraint caused by the second stopper  6 , the flexibility of the sheath allowing it to ride over the first stopper  5 . It can be seen from  FIGS. 6 and 7  that the first stopper  5  extends slightly beyond the space allowed by the inner wall of the sheath; it can easily be understood, however, that very slightly flexibility in the sheath  3  allows it to ride over first stopper  5 , giving a more positive interlock when first stopper  5  engages aperture  4 . In the preferred embodiment, the second stopper  6  is made of flexible material and has radial tension directed outwardly against the inner walls  20  of sheath  3  (see  FIG. 7 ). This arrangement provides additional security to prevent the sheath  3  from inadvertently sliding back over and covering the blade during a cutting procedure. 
     The length of the sheath  3  is such that it just covers the first stopper  5  while resting on tail stopper  8  in the ready position. Furthermore, the length of the sheath  3  is such that it completely covers the blade  2  when extended into the blocking position. Such a construction assists in the preferred working of the sheath  3  but does not necessarily mean that other combinations are not possible. 
       FIG. 7  shows the detailed cross-sectional view of the proximal end of sheath  3  in ready position. This figure shows the detail of second stopper  6  and the radial tension extending outwards into the inner wall  20  of the sheath  3 . 
     Thus, there is shown and described a unique design and concept of a scalpel blade cover. While this description is directed to a particular embodiment, it is understood that those skilled in the art may conceive modifications and/or variations to the specific embodiments shown and described herein. Any such modifications or variations which fall within the purview of this description are intended to be included therein as well. It is understood that the description herein is intended to be illustrative only and is not intended to be limitative. Rather, the scope of the invention described herein is limited only by the claims appended hereto.