Selectively retractable, disposable surgical knife

A retractable, disposable surgical knife that includes a hollow sheath and a blade assembly received for sliding movement within the hollow sheath. The blade assembly includes a slide block and a knife blade held by the slide block. A mechanism including a cooperating resilient actuator and guide track allows the blade assembly to be selectively secured in a first, retracted position wherein the blade is withdrawn into the sheath and a second, extended position wherein the blade extends from the sheath for use. A separate mechanism is provided for permanently locking the blade assembly in a third, fully retracted position wherein blade is fully withdrawn within the sheath to prevent inadvertent sticks. The permanent locking mechanism is fully concealed within the sheath so as to prevent inadvertent engagement with an object and possible release from the permanently locked position.

TECHNICAL FIELD 
The present invention relates generally to the medical instrument field 
and, more particularly, to a retractable and disposal surgical knife 
specifically designed to prevent inadvertent puncture wounds from the 
knife blade after use and, therefore, the spread of infectious disease. 
BACKGROUND OF THE INVENTION 
Surgical knives or scalpels are utilized by surgeons in many instances to 
complete operative procedures. Of course, many such procedures are 
performed on patients with infectious diseases such as acquired immune 
deficiency syndrome (AIDS) and infectious hepatitis. Unfortunately, the 
attending surgeons, nurses and other health care workers are subjected to 
a significant risk of infection if they are inadvertently stuck, pricked 
or cut with a contaminated surgical knife that has been withdrawn from a 
patient inflicted with such a communicable disease. Accordingly, it should 
be appreciated that it is critically important to avoid accidents 
including inadvertent sticks and cuts of any individual with a used 
surgical knife. Further, the safe, long term disposal of surgical knives 
and particularly used surgical knives is a serious concern. 
These concerns have been addressed in the prior art. For example, in U.S. 
Pat. No. 3,906,626 to Riuli, a disposable surgical scalpel is disclosed 
including a protective outer sheath and retractable and extendable handle 
carrying a knife blade. The device also includes a "permanent" locking 
arrangement including a cooperating detent, spring, and resilient cam. It 
should be noted, however, that when locked the cam projects outwardly from 
the sheath. Accordingly, the cam may be engaged inadvertently by an object 
or individual and accidently manipulated to release the lock thereby 
allowing the knife blade to again be extended from the sheath. As a 
result, a significant risk of inadvertent or accidental sticks and cuts 
still remains in this prior art design. Accordingly, a need exists for an 
improved arrangement wherein the permanent lock is fully concealed and 
shielded from inadvertent contact and manipulation. 
SUMMARY OF THE INVENTION 
Accordingly, it is one object of the present invention to provide a 
retractable, disposal surgical knife of relatively simple construction 
that is inexpensive to produce. 
Another object of the invention is to provide a retractable, disposal 
surgical knife that is relatively easy to utilize. More specifically, the 
knife may be readily switched from position to position and is of a shape 
and weight that allows comfortable gripping and precise manipulation when 
making an incision. 
Still another object of the invention is to provide a retractable, 
disposable surgical knife that furnishes reliable, trouble free operation. 
Yet another object of the invention is to provide a retractable, disposal 
surgical knife including a permanent locking mechanism that is fully 
concealed. Advantageously, the mechanism virtually prevents any possible 
inadvertent release of the device from the permanent lock position thereby 
virtually eliminating the risk of an individual receiving an inadvertent 
puncture wound. 
Additional objects, advantages and other novel features of the invention 
will be set forth in part in the description that follows and in part will 
become apparent to those skilled in the art upon examination of the 
following or may be learned with the practice of the invention. The 
objects and advantages of the invention may be realized and obtained by 
means of the instrumentalities and combinations particularly pointed out 
in the appended claims. 
To achieve the foregoing and other objects, and in accordance with the 
purposes of the present invention as described herein, an improved 
retractable, disposable surgical knife is provided. The surgical knife 
includes a hollow sheath and a blade assembly received for sliding 
movement within the hollow sheath. The blade assembly includes a slide 
block and a knife blade that is held in the slide block. 
The surgical knife also includes means, mounted to the blade assembly and 
sheath, for selectively securing the blade assembly in a first, retracted 
position wherein the blade is withdrawn into the sheath and a second, 
extended position wherein the blade extends from the sheath for use. 
Additionally, the present surgical knife includes a separate means, also 
mounted to the blade and sheath, for permanently locking the blade 
assembly in a third, fully retracted position. In this position the blade 
is fully withdrawn within the protective sheath to prevent inadvertent 
sticks. Advantageously, the permanent locking mechanism is fully concealed 
within the sheath. This essentially prevents inadvertent engagement with 
an object or inadvertent manual manipulation and possible release from the 
permanently locked position. Accordingly, a more dependable and secure 
arrangement is provided than previously known in the art. 
Still more specifically, the sheath includes a substantially three sided 
main body and an integral cover flap, for forming a fourth side, that is 
connected to the main body by a living hinge. Preferably the sheath is 
formed from a durable plastic by means of an injection molding process. As 
molded, the cover flap includes a locking flange provided with an inwardly 
projecting shoulder opposite the living hinge. Additionally, the main body 
includes a cooperating lip on the side of the main body opposite the 
living hinge and cover flap. 
After positioning the blade assembly within the main body, the cover flap 
is folded over so as to overlap the main body with the projecting shoulder 
engaging under the lip. The shoulder and lip are then heat welded together 
to permanently seal the resulting four-sided sheath. 
In accordance with still another aspect of the present invention, the 
selective securing means includes a resilient actuator carried on the 
blade assembly. This actuator extends through a cooperating guide slot 
formed in the cover flap so as to allow manipulation by the fingers of the 
operator. Of course, it should further be appreciated that the actuator 
and guide slot cooperate to limit the extent of movement of the blade 
assembly within the sheath. 
More specifically, the resilient actuator includes a set of laterally 
protruding locking tabs and the guide slot includes at least two pair of 
matching notches for receiving the tabs when in the first retracted and 
second, extended positions. Additionally, it is preferred that a third 
pair of matching notches be provided for receiving the tabs when the blade 
assembly is positioned in a third, fully-retracted, permanent lock 
position. This is desirable as the positioning of the tabs in the third 
pair of matching notches provides the operator with a visual indication 
that the surgical knife is secured in the permanent lock position. 
The permanent locking mechanism preferably includes a projecting hook that 
is integrally formed or molded with the main body of the sheath and a 
cooperating hook receiving cutout formed in the rear end of the slide 
block opposite the knife blade. More specifically, the cutout includes a 
latching shoulder that is engaged by the hook when in the third, 
permanently locked position. In an alternative embodiment, a hook is 
integrally formed projecting from the rear end of the slide block and a 
cutout with cooperating latching shoulder is integrally formed with the 
main body of the sheath. Of course, it should be appreciated that the 
cover flap fully conceals either embodiment of the permanent locking 
mechanism from view as well as potential inadvertent engagement with an 
object that could possibly lead to the release of the permanent lock. As a 
result, the security of the permanent lock is significantly enhanced over 
prior art designs and any risk of release of the permanent lock and 
possible inadvertent stick or cut of an individual is substantially 
eliminated. 
Still other objects of the present invention will become apparent to those 
skilled in this art from the following description wherein there is shown 
and described a preferred embodiment of this invention, simply by way of 
illustration of one of the modes best suited to carry out the invention. 
As it will be realized, the invention is capable of other different 
embodiments and its several details are capable of modification in 
various, obvious aspects all without departing from the invention. 
Accordingly, the drawings and descriptions will be regarded as 
illustrative in nature and not as restrictive.

DETAILED DESCRIPTION OF THE INVENTION 
Reference is now made to the drawing FIGS. 1-5 showing the improved 
surgical knife 10 of the present invention. As will be more fully 
understood after reviewing the entire description, the surgical knife 10 
advantageously includes a fully shielded or concealed permanent locking 
mechanism 12 that virtually prevents inadvertent engagement and release so 
as to ensure that the blade 14 is maintained in a retracted position 
thereby preventing inadvertent sticks and cuts. 
As shown best in FIGS. 3 and 5, the surgical knife 10 includes a sheath 16 
having a substantially three-sided main body 18 and a cover flap 20 of 
substantially L-shaped cross-section. Preferably, both the main body 18 
and cover flap 20 of the sheath 16 are molded from durable plastic 
utilizing an injection molding process. Advantageously, both the materials 
and the process itself are relatively inexpensive so as to allow economic 
production. Additionally, this process allows the formation of a living 
hinge 22 between the main body 18 and cover flap 20 whereby these two 
components are formed as a single, integral part. 
A blade assembly 24 is received for sliding movement within the sheath 16 
(note FIGS. 3 and 4). More specifically, the blade assembly 24 includes a 
slide block 25 that holds the blade 14. As best shown in FIG. 4, the slide 
block 25 includes a cooperating upper section 26 and lower section 28 that 
may be also molded from plastic. As particularly shown, the lower section 
28 includes a series of three flanges 30 that form a substantially 
U-shaped cavity 31 corresponding in profile to the rear or mounting 
portion 33 of the knife blade 14 but allowing clearance for receipt 
therein. Additionally, two upstanding pins 32 are provided. These pins 32 
are received in cooperating apertures 34 in the knife blade mounting 
portion 33. Together, the flanges 30 and pins 32 cooperate with the lower 
face of the upper section 26 to secure the knife blade 14 in position in 
the slide block 25 when the upper section 26 and the lower section 28 are 
heat welded together. As play between the knife blade 14 and slide block 
25 is essentially eliminated, a precise incision may be made when 
utilizing the surgical knife 10. 
In accordance with an important aspect of the present invention, the blade 
assembly 24 and, accordingly, the knife blade 14 may be fully retracted 
into and/or extended from the sheath 16 as desired. Further, the blade 
assembly 24 may be secured in the necessary position relative to the 
sheath 16 so as to allow easy, convenient and reliable operation. The 
securing mechanism for achieving this end is generally shown in FIGS. 
2a-2c and is designated reference numeral 36. 
More specifically, a resilient actuator 38 is integrally formed when 
molding the upper section 26 of the slide block 25. The actuator 38 
includes a relatively narrow leg portion 40 that supports on its distal 
end an upstanding knob 42 for finger actuation. When assembled, the 
upstanding knob 42 extends through a guide slot 44 formed in the cover 
flap 20 of sheath 16. As should be appreciated, the ends of the guide slot 
engage the upstanding knob 42 and function to limit the extent of the 
sliding action of the blade assembly 24 within the sheath 16. 
Additionally, it should be appreciated that laterally spaced locking tabs 
46 are provided adjacent the upstanding knob 42 on the resilient actuator 
38. These locking tabs 46 engage in a series of notches 48, 50, 52 
positioned at spaced intervals along the guide slot 44. More specifically, 
when the locking tabs 46 are positioned to engage in the first notch 48, 
the blade assembly 24 is secured in a first, retracted position wherein 
the blade 14 is fully contained within the sheath 16 (see FIG. 2a). This 
is the position in which the surgical knife 10 is packaged for shipment to 
the user. 
In contrast, when the locking tabs 46 are positioned to engage in the 
second notch 50, the blade assembly 24 is positioned so that the blade 14 
fully extends from the sheath 16 (see FIG. 2b). In this position, the user 
may surgically incise a patient as required. Of course, as the blade 14 is 
secured substantially free of play in the slide block 25 and the slide 
block 25 is securely held substantially free of play within the sheath 16 
(note converging cam surfaces 54 shown best in FIG. 5 that serve to pinch 
and tightly hold the slide block 25 when in the second, operative 
position), precision incising is possible. 
Following completion of the operative procedure, the upstanding knob 42 is 
manipulated to fully retract the blade assembly 24 to a third, retracted 
position (see FIG. 2c). In this fully retracted position, the blade 
assembly 24 is permanently locked in position in the manner described 
below with the blade 14 fully received within the protective sheath 16. 
This allows safe disposal of the surgical knife 10 while minimizing the 
risk of the inadvertent release of the locking mechanism 12 and, 
therefore, the potential for inadvertent sticks and cuts that could lead 
to the communication of infectious disease. 
The permanent locking mechanism 12 is best shown with reference to FIGS. 2a 
and 2c. Particularly, a hook 56 is integrally formed on and molded with 
the main body 18 of the sheath 16 (see also FIG. 5). Similarly, a 
cooperating cutout 58 is integrally formed in the upper section 26 of the 
slide block 25 (see also FIG. 4). More particularly, the cutout 58 
communicates with the rear face 60 of the slide block 25 opposite the 
projecting knife blade 14. 
When the blade assembly 24 is in the first, retracted position, the hook 56 
is not engaged in the cutout 58 and, accordingly, the permanent lock is 
not engaged (note FIG. 2a). Accordingly, an individual is able to 
manipulate the blade assembly 24 to the second, operative position as 
required to complete the surgical procedure. In contrast, when the 
upstanding knob 42 is manipulated to the rearmost position so as to bring 
the locking tabs 46 into engagement with the third notch 52, the cam 
surface 62 engages the rear face 60 of the slide block 25 and the hook 56 
pivots away and passes into the cutout 58. As soon as the hook 56 reaches 
the wide portion of the cutout 58 the resilient nature of the material 
causes the hook to pivot into engagement with the shoulder 66 thereby 
securing the slide block 25 into position. As the hook 56 and cutout 58 
are fully concealed and shielded by the overlying cover flap 20, no 
objects or fingers may inadvertently engage the locking mechanism 12 and, 
accordingly, a virtual permanent lock results. Thus, inadvertent release 
of the permanent lock is substantially avoided. 
First the assembly procedure and then the utilization of the surgical knife 
10 of the present invention will now be described. 
After molding the upper and lower sections 26, 28 of the slide block 25, 
the blade 14 is carefully positioned in the cavity 31 of the lower section 
defined by the three cooperating flanges 30. As this is done, the pins 32 
project through the corresponding apertures 34 in the blade 14. Next, the 
upper section 26 of the slide block 25 is placed in position over the 
lower section 28 where it is heat welded to secure in position. 
The completed blade assembly 24 is then positioned within the three walls 
of the main body 18 by placing in the open face 72 (see FIG. 5). The cover 
flap 20 is then folded over about the living hinge 22 so as to close the 
main body 18 and form the fourth wall of the sheath 16. As this is done, 
the upstanding knob 42 is threaded into the guide slot 44 and the locking 
flange 76 on the cover flap 20 is snapped over the lip 78 on the main body 
18. The shoulder 80 on the locking flange 76 engages the lower side of the 
lip 78 to secure the cover flap 20 in the closed position. When closed, 
closed end 79 of the sheath 16 and the cover flap 20 fully conceal and 
shield the locking mechanism 12 from view and inadvertent manipulation and 
release. As a further precaution to ensure that the cover flap 20 remains 
closed, the locking flange 76 and lip 78 may be heat welded together for 
permanency. 
If not already so positioned, the upstanding knob 42 is now manipulated to 
position the blade assembly 24 in the first retracted position with the 
locking tabs 46 received in the first notch 48. In this way, the blade 14 
is fully retracted within the sheath 16 so that inadvertent sticks and 
cuts are avoided but selective movement to the second, extended position 
is still possible. The surgical knife 10 is then sterilized and packaged 
in a manner known in the art. 
As indicated above, the surgical knife 10 of the present invention is 
particularly easy to utilize. The surgical knife is first removed from 
packaging and the blade assembly 24 is maintained in the first, retracted 
position until ready to complete the surgical procedure. At that point in 
time, the surgeon presses downwardly on the upstanding knob 42; the 
resilient leg portion 40 allowing sufficient limited downward movement to 
allow the locking tabs 46 to pass under the cover flap 20. 
Once the clearance is provided, the upstanding knob 42 is pushed in the 
direction of action arrow A (see FIG. 2a) while maintaining downward 
pressure. As a result, the blade assembly 24 slides forward in the sheath 
16 and the blade 14 is extended from the open end 81. Upon the upstanding 
knob 42 reaching the forward end of the guide slot 44, the knob is 
released. As a result, the resilient leg portion 40 springs back to its 
natural position thereby bringing the locking tabs 46 into engagement in 
the second notch 50. This serves to secure the blade assembly 24 in the 
second, extended position shown in FIG. 2b. In this position, the slide 
block 25 is securely held by the squeezing engagement of the converging 
cam surfaces 54 and extended from the sheath 16 to allow precise incising 
in the manner desired. 
Following utilization, the upstanding knob 42 is again depressed to allow 
passage of the cams 46 under the cover flap 20 and simultaneously moved in 
the direction of action arrow B (see FIG. 2b). Typically, the rearward 
movement will continue until the blade assembly 24 is fully retracted to 
the third, retracted position wherein the locking tabs 46 are received in 
the third notch 52 and the permanent locking mechanism 12 is engaged (that 
is, the hook 56 is engaged in the cutout 58 as shown in FIG. 2c). 
Advantageously, the receipt of the locking tabs 46 in the third notch 52 
provides visual confirmation of the engagement of the permanent lock 
indicating to the user that the surgical knife 10 is ready for safe 
disposal. A slot extension 82 positively insures that full engagement. Of 
course, it should be recognized that in certain situations, retraction to 
only the first, retracted position is all that is desired so that the 
blade assembly 24 may again be extended for additional, subsequent 
incising. 
An alternative embodiment for the permanent locking mechanism 12 is shown 
in FIG. 6. More specifically, a hook 100 is integrally molded with the 
slide block 102 so as to project rearwardly from the rear wall 104 of the 
slide block. The hook 100 opens downwardly and cooperates with the 
latching shoulder 106 integrally molded in the main body 108 of the sheath 
110. Accordingly, as the slide block 102 is moved into the rearmost, 
permanent locking position, the leading cam surface 112 engages the 
latching shoulder 106. This pivots the hook 100 upwardly over the latching 
shoulder 106 until the hook clears the shoulder. The resilient hook 100 
then snaps downwardly with the hook in full, virtually permanent and 
nondefeatable engagement with the shoulder 106 (note phantom line 
position). Of course, the main body 108 and cover flap 114 of the sheath 
110 fully conceal and protect the locking mechanism 12 as already 
described with respect to the original embodiment. 
In summary, numerous benefits have been described which result from 
employing the concepts of the present invention. Advantageously, the 
surgical knife 10 incorporates a relatively simple structure that may be 
quickly, efficiently and economically produced and assembled. 
Additionally, the surgical knife 10 allows very simple, straight-forward 
operation. Further, the permanent locking mechanism 12 provided for the 
purposes of disposal is fully concealed by the cover flap 20 that is heat 
welded in position. Accordingly, manipulation of the permanent locking 
mechanism 12 and release thereof is substantially prevented. 
The foregoing description of a preferred embodiment of the invention has 
been presented for purposes of illustration and description. It is not 
intended to be exhaustive or to limit the invention to the precise form 
disclosed. Obvious modifications or variations are possible in light of 
the above teachings. The embodiment was chosen and described to provide 
the best illustration of the principles of the invention and its practical 
application to thereby enable one of ordinary skill in the art to utilize 
the invention in various embodiments and with various modifications as are 
suited to the particular use contemplated. All such modifications and 
variations are within the scope of the invention as determined by the 
appended claims when interpreted in accordance with breadth to which they 
are fairly, legally and equitably entitled.