Spring-actuated, retractable-bladed surgical scalpelAbstract Claims 1. A surgical scalpel having a spring-actuated retractable blade, comprising in combination: (a) an elongated handle having a first side and a second side, a first elongated cavity within said handle extending over the long dimension thereof and opening to the outside at both a forward end and a rearward end, and a tab extending into the first cavity perpendicular to the long dimension thereof and located toward the rearward end of said handle, the first side having an elongated window therethrough along the long dimension of said handle and located toward the forward end thereof and a second window therethrough disposed toward the rearward end of said handle, the first side further having a first tab extending into the first cavity and located in the vicinity of the edge of the elongated window closest to the rearward end of said handle and a second tab extending into the first cavity between the second window and the rearward end of said handle; the second side having an interior elongated slot therein which terminates before reaching the forward end of said handle and which opens to the outside of said handle at the rearward end thereof; (b) a cutting blade; (c) an elongated slide having a first end and a second end adapted to slidably move longitudinally through the first cavity in said handle and to receive said cutting blade in the region of the first end thereof; a portion adapted to be engaged by and actuated by a digit through the elongated window; a raised, deformable latch in the region of the second end on the side thereof of the digit-engaging portion for engaging either of the first or second tabs in said handle; and a tab adapted to move within the slot in the second side of said handle, said slide engaging and being reversibly immobilized by the tab extending into the first cavity of said handle when located in its rearwardmost position in said handle; and (d) a coil spring disposed within the interior slot in the second side of said handle and adapted to continuously contact the tab of said slide, thereby providing a force on said slide directed toward the rearward end of said handle. 2. The surgical scalpel having a spring-actuated retractable blade as described in claim 1, wherein the first side further has at least one third window therethrough between the second window and the rearward end of said handle and at least one third tab extending into the first cavity and disposed between the at least one third window and the rearward end of said handle, such that the deformable latch portion of said slide can engage the at least one third tab in said handle, whereby said handle can receive a longer slide. 3. The surgical scalpel having a spring-actuated retractable blade as described in claim 1, further comprising means for reducing contact between said slide and the first side and the second side of said handle when said slide is moved through said handle. 4. The surgical scalpel having a spring-actuated retractable blade as described in claim 3, wherein said means for reducing contact between said slide and the first side and the second side of said handle includes a second cavity coextensive with the first cavity and disposed on a side of the first cavity perpendicular to the long dimension thereof and adapted to receive a portion of said slide and guide said slide within the first cavity when said slide is moved therethrough. 5. The surgical scalpel having a spring-actuated retractable blade as described in claim 1, wherein said cutting blade can be replaced on said slide. 6. The surgical scalpel having a spring-actuated retractable blade as described in claim 1, wherein the thickness of the first side in the region of the elongated window is chosen such that a user of said surgical scalpel cannot accidentally depress the raised, deformable latch member of said slide through the elongated window when said cutting blade is in its extended and locked position. 7. A surgical scalpel having a spring-actuated retractable blade, comprising in combination: (a) an elongated handle having a first side having a first interior recessed surface and a second side having a second interior recessed surface, the first interior surface and the second interior surface together forming an elongated cavity within said handle extending over the long dimension thereof and opening to the outside at both a forward end and a rearward end of said handle member, the first side further having a first window, a second window and at least one third window therethrough disposed along the first side, the first window being elongated along the long dimension of said handle and being closest to the forward end thereof and the at least one third window being closest to the rearward end of said handle, and a tab which extends into the cavity, the second side having an interior elongated slot therein which terminates before reaching the forward end of said handle and which opens at the rearward end thereof, the second side further comprising a first tab extending into the cavity between the first window and the second window, a second tab extending into the cavity between the second window and the third window, and at least one third tab extending into the cavity between the at least one third window and the rearward end of said handle; (b) a cutting blade; (c) an elongated slide having a first end and a second end and adapted to slidably move longitudinally through the cavity in said handle and to receive said cutting blade in the region of the first end thereof, having a portion adapted to be engaged by and actuated by a digit through the first window, having a raised, deformable latch in the region of the second end on the side thereof of the digit-engaging portion for engaging any of the first, second or third tabs in said handle, and having a tab adapted to move within the slot in the second side of said handle; and (d) a coil spring located within the interior slot in the second side of said handle and adapted to continuously contact the tab of said slide, thereby providing a force on said slide directed toward the rearward end of said handle. 8. The surgical scalpel having a spring-actuated retractable blade as described in claim 7, further comprising a tab extending into the first cavity of said handle perpendicular to the long dimension thereof and located toward the rearward end of said handle, said slide engaging and being reversibly immobilized by the tab when said slide is located in its rearwardmost position in said handle. 9. The surgical scalpel having a spring-actuated retractable blade as described in claim 7, further comprising means for reducing contact between said slide and the first side and the second side of said handle when said slide is moved through said handle. 10. The surgical scalpel having a spring-actuated retractable blade as described in claim 9 wherein said means for reducing contact between said slide and the first side and the second side of said handle includes a second cavity coextensive with the first cavity and disposed on a side of the first cavity perpendicular to the long dimension thereof and adapted to receive a portion of said slide and guide said slide within the first cavity when said slide is moved therethrough. 11. The surgical scalpel having a spring-actuated retractable blade as described in claim 7, wherein said cutting blade can be replaced on said slide. 12. A surgical scalpel having a spring-actuated retractable blade, comprising in combination: (a) an elongated handle having a first side and a second side, a first elongated cavity within said handle extending over the long dimension thereof and opening to the outside at both a forward end and a rearward end, the first side having an elongated window therethrough along the long dimension of said handle and located toward the forward end thereof and a second window therethrough disposed toward the rearward end of said handle, the first side further having a first tab extending into the first cavity and located in the vicinity of the edge of the elongated window closest to the rearward end of said handle and a second tab extending into the first cavity between the second window and the rearward end of said handle; the second side having an interior elongated slot therein which terminates before reaching the forward end of said handle and which opens to the outside of said handle at the rearward end thereof; (b) a cutting blade; (c) an elongated slide having a first end and a second end adapted to slidably move longitudinally through the first cavity in said handle and to receive said cutting blade in the region of the first end thereof; a portion adapted to be engaged by and actuated by a digit through the elongated window; a raised, deformable latch in the region of the second end on the side thereof of the digit-engaging portion for engaging either of the first or second tabs in said handle; and a tab adapted to move within the slot in the second side of said handle; (d) means for engaging and reversibly immobilizing said slide when said slide is located in its rearwardmost position in said handle; and (e) means for providing a force on said slide directed toward the rearward end of said handle. 13. The surgical scalpel having a spring-actuated retractable blade as described in claim 12 wherein said means for providing a force on said slide directed toward the rearward end of said handle comprises a coil spring disposed within the interior slot in the second side of said handle and adapted to continuously contact the tab of said slide. 14. The surgical scalpel having a spring-actuated retractable blade as described in claim 12, wherein said means for engaging and reversibly immobilizing said slide when said slide is located in its rearwardmost position in said handle includes a tab extending into the first cavity perpendicular to the long dimension thereof and located toward the rearward end of said handle such that said slide engages and is reversibly immobilized by the tab when said slide is located in its rearwardmost position in said handle. 15. The surgical scalpel having a spring-actuated retractable blade as described in claim 12 wherein the first side further has at least one third window therethrough between the second window and the rearward end of said handle and at least one third tab extending into the first cavity and disposed between the at least one third window and the rearward end of said handle, such that the deformable latch portion of said slide can engage the at least one third tab in said handle, whereby said handle can receive a longer slide. 16. The surgical scalpel having a spring-actuated retractable blade as described in claim 12 further comprising means for reducing contact between said slide and the first side and the second side of said handle when said slide is moved through said handle. 17. The surgical scalpel having a spring-actuated retractable blade as described in claim 16 wherein said means for reducing contact between said slide and the first side and the second side of said handle includes a second cavity coextensive with the first cavity and disposed on a side of the first cavity perpendicular to the long dimension thereof and adapted to receive a portion of said slide and guide said slide within the first cavity when said slide is moved therethrough. 18. The surgical scalpel having a spring-actuated retractable blade as described in claim 12 wherein said cutting blade can be replaced on said slide. Description [0026] FIGS. 4a-4d show the same views as FIGS. 3a-3d, respectively, except that the knife is in its extended or deployed condition. Of note is that FIG. 4c illustrates the latching action of deformable latch 46 in slide half 14a in contact with tab 50a which secures stop 28 of slide 16 against tab 26 in handle 12 when slide 16 is in its fully forward position. Although handle 12 and slide 16 are fabricated as handle halves 10a and 10b and slide halves 14a and 14b, respectively, the halves are glued or welded together by any of several well-known joining processes as part of the assembly process for the knife. [0027] The retractable knife of the present invention is packaged for shipment with slide 16 is in its rearward or undeployed position, whereby tab 42 wedges slide 16 firmly within handle cavity 82 (FIG. 3e). This prevents slide 16 from readily moving forward such that blade 20 can puncture a sterilization envelope if the knife is accidentally dropped. In actual operation, latch 46 is may engage any of tabs 50a, 50b or 50c, while being deformable such that slide 16 can slide through handle cavity 82 under the action of either coil spring 18 or a digit, generally a thumb, in contact with digit-engaging portion 44. Spring 18 forces latch 46 against whichever of the tabs the latch member is located in forward of it when no external force is applied to digit-engaging portion 44 of slide 16. [0028] As stated hereinabove, handle 12 is relieved 76 in the region of window 22 to provide better access to digit-engaging portion 44 and latch 46. The shape of relieved portion 76 is chosen such that an operator may readily engage digit-engaging portion 44 of slide 16 in order to deploy blade 20, while making it more difficult to depress latch 46 until it is desired to retract the blade. Therefore, latch 46 cannot easily be accidentally released by the operator during use of the instrument. Additionally, latch 46 may slightly extend through the rear portion of window 22 when slide 16 is fully deployed to more positively secure slide 16 in its forwardmost position, without affecting the scalpel's resistance to accidental retraction of slide 16. [0029] FIG. 3c illustrates latch 44 engaging tab 50b under the action of spring 18 such that the knife is in its closed or retracted position. Given the length of slide 16, this position would be attained by a user first overcoming the wedging action of tab 42 and moving slide 16 sufficiently far forward using digit-engaging portion 44 of slide 16 such that latch 46 is moved forward of tab 50b and allowed to be returned thereto under the action of spring 18. Depressing deformable latch 46 by inserting a solid object through window 24a will allow slide 16 to move rearward and engage tab 50c, again under the action of spring 18. By depressing latch 46 once more, but through window 24b, slide 16 will move rearward and out of cavity 82 under the action of spring 18, at which time slide 16 can be removed from handle 12 in order to exchange slides. Tab 50c and window 24b together permit longer slides accommodating blades 20 having different sizes and shapes to be used. [0030] As described hereinabove, FIG. 4c illustrates the latching action of deformable latch 46 in slide half 14a in contact with tab 50a which secures stop 28 of slide 16 against tab 26 in handle 12 when slide 16 is in its fully forward position. [0031] To improve the slidability of slide 16 within handle cavity 82, slide 16 is kept from contacting inner walls 48 and 58 of handle 12 when the slide is moved by an operator of the scalpel. Tab 40 and the top edge, 52, of slide half 14b form slot, 54, which is adapted to slidably engage the lower defining portion, 56, (FIG. 1) of channel 34 on the inside, 58, of side 10b. Further, notch, 70, in end piece, 72, of slide half 14b of slide 16 is adapted to slidably engage flange, 74, in side 10a of handle 12, thereby guiding tab 40 which is also formed in end piece 72, in channel 34. The upper portion of slide 16 is thereby guided along the inside of handle 12. Additionally, raised portion, 60, (FIG. 1) and flange, 62, of side 10a of handle 12 cooperate to form channel 80 (FIG. 3e) which slidably engages tabs, 64a and 64b, of lower portion, 66, of slide half 14b of slide 16, thereby guiding the lower portion of slide 16 along the inside of handle 12. [0032] Tolerances and materials are selected such that the scalpel is stable in its operating or deployed mode yet is easily retracted. For surgical or other medical uses, materials must conform to Food and Drug Administration standards. For example, scalpels must be ethylene oxide or gamma-ray sterilizable, or autoclavable. It is anticipated that the slide and handle portions of the present scalpel will chosen for their moldability and for their relative coefficients of expansion and friction such that accurate tolerances can be maintained for operating stability, while maintaining ready relative motion and freedom from binding. [0033] The foregoing description of the invention has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. For example, it would be apparent to one having ordinary skill in the surgical arts after carefully studying the present disclosure that the retractable knife of the present may be fabricated to accommodate either right- or left-handed operators. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.
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