Scalpel with retractable blade

Abstract

Scalpel comprising a handle (1) with a longitudinally extending cavity (3), a blade carrier (2) arranged within the cavity (3) and movable longitudinally relative to the handle (1) between a use position in which a blade (5) carried by the blade carrier (2) is exposed for use at an open end (8) of the cavity (3) and a non-use position in which a blade (5) carried by the blade carrier (2) is retracted within the cavity (3) in the handle (1), and a manually operable slide (4) associated with the blade carrier (2) and which passes through a slot (6) in a wall of the handle (1) at its upper edge (7), wherein the blade carrier (2) is restricted to longitudinal movement within the cavity (3) by longitudinally extending cooperating guide surfaces (12, 13), wherein the scalpel is characterized in thatthat the blade carrier (2) or the slide (4) has a locking surface (21) directed rearward in the operating position, wherein the locking surface (21) in the operating position of the blade carrier (2) is in at least partially cooperating alignment with a cooperating stop surface (22) provided on the handle (1), such that a force exerted on the blade carrier (2) in a direction corresponding to the length of the handle (1) causes the locking surface (21) to engage with the stop surface (22) in order to prevent movement of the blade carrier (2) into the cavity (3) in the handle (1), and that the cooperating guide surfaces (12, 13) are configured to allow a limited transverse movement of the guide surfaces (12, 13) relative to each other and are biased to a position in which the stop surface (22) is at least partially cooperating with the cooperating locking surface (21) provided on the handle (1).wherein the preload is arranged to be overcome by a pressure exerted on the slide (4) corresponding to the pressure required to retract the blade carrier (2) into the handle (1), so that the locking surface (21) and the stop surface (22) can move past each other relative to each other when the blade (5) is retracted into the handle (1) as a result of a transverse movement of the guide surfaces (12, 13), characterized in that a preload of the blade carrier (2) towards the top of the handle (1) is achieved by a one-piece leaf spring formation (25) which is in a sliding relationship relative to a lower surface of the cavity (3), and wherein the one-piece leaf spring formation (25) is arranged in the form of a crouching closed loop on a side of the blade carrier (2) away from the locking surface (21).

Description

CROSS-REFERENCE TO RELATED REGISTRATION

[0001] This application claims priority over British patent application 1703887.8, filed on 10 March 2017, which is incorporated herein by reference. AREA OF INVENTION

[0002] The invention relates to a scalpel with a retractable blade, typically, but not necessarily, a disposable scalpel. In particular, the invention relates to a scalpel in which the movement of a blade relative to a supporting scalpel handle between an extended working position and a retracted non-working position is achieved by moving a blade carrier via a thumb-operated slider attached to the blade carrier, which is slidable within the handle, generally via a slot through a wall of the handle. BACKGROUND OF THE INVENTION

[0003] Disposable scalpels with retractable blades have been manufactured in many different forms, one of which features a slider protruding through a slot in the rim of a handle, which can be considered the upper rim of the scalpel handle and has a cavity into which a blade can be retracted from an exposed position. The embodiment of a scalpel type preferred by the applicant, as well as its background and the reasons for its development, are described in the published international patent application WO 2004 / 045428A1, the contents of which are incorporated herein by reference.

[0004] There are a number of factors considered desirable for scalpels with retractable blades, and which are present to some extent in existing scalpels, whereby these factors contribute to the scalpel blade being held firmly in its working position; to it being positively locked in its retracted non-working position; and also a preferred device intended to prevent the reuse of a scalpel by providing a final, non-retractable retracted position.

[0005] In one of the applicant's embodiments, the blade carrier, with its attached blade and the externally accessible slide that engages in the blade carrier via a slot in the top of the handle, can be moved into a fully forward-facing operating position by moving the slide into its fully forward-facing position. In this position, the slide contacts a closed front end of the slot, thus preventing further forward movement. When this position is reached, it is accompanied by an audible "click" indicating the completion of the travel. The "click" is produced by a trapezoidal tooth formation on one side of the slide, which pushes a cooperating tooth formation on the handle slot laterally outward, followed by a snap-back action of the cooperating tooth formation in conjunction with the formation on the slide, thus producing the audible "click".

[0006] In the fully forward-facing position, the sliding tooth formation is located in front of the interacting handle tooth formation, and the handle elasticity thus provides a restraining force against backward movement of the blade carrier with blade and slider. During normal use of the scalpel unit, the slider can be held by the index finger or between the index finger and thumb, depending on user preference or the procedure's requirements. This holding technique provides additional restraining force against backward blade movement.

[0007] However, certain procedures can prevent the slider from holding, and in such cases, blade retention depends solely on the interplay of the interacting trapezoidal tooth formations and the handle's elasticity. When performing certain types of operations, such as a stabbing motion or the like, there is a possibility that the blade will be forced backward into the handle, causing the trapezoidal formations to disengage, and such an event could be detrimental.

[0008] The applicant sees a need for a scalpel with a retractable blade that at least largely avoids this possibility. However, it is important that a surgeon is not required to perform any additional or unusual actions to activate or deactivate an additional locking or restraint device.

[0009] EP 2 732 780 A1 discloses a scalpel with a blade supported by a blade carrier that can be extended from a handle by means of laterally mounted sliders. A locking element or spring-loaded pawl on the blade carrier engages an abutment on the handle when the blade is fully extended to prevent the blade from retracting under an axial backward force. To retract the blade carrier, the spring-loaded pawl must deflect downwards, away from the abutment. The left and right halves of the slider are fitted together on the blade carrier but are not rigidly attached to it. The slider halves can slide axially a short distance relative to the blade carrier. A tab element with an end-sloping ramp surface is integrally formed with each slider half.In the forward locking position, the angled ramp surface of the latch element is in close proximity to the normally positioned angled surface of the spring pawl. When either slide half is moved backward by a finger movement, the latch element moves backward and contacts the stationary spring pawl, causing it to fold downward and the free end of the spring pawl to release from the abutment surface. Once the spring pawl is released from the abutment, the slide halves are prevented from any further independent axial movement relative to the blade carrier. As the slide halves continue to move backward, the blade carrier slides backward together with the slide halves, retracting the blade into the handle.The positioning of the sliding halves on each side of the handle requires an unnatural movement from the user, as the user tends to grasp the sliding halves between the thumb and forefinger and then retract them while gripping the handle with the remaining fingers. Furthermore, the spring-loaded pawl is constantly under tension in the retracted position, which can lead to its weakening or deformation. Similarly, the action of the tab element on the spring-loaded pawl, which causes it to detach from the abutment surface, can also weaken or deform the spring-loaded pawl with repeated extension and retraction of the blade and blade holder.

[0010] Another potential problem with the scalpel disclosed in this document is that the forward locking mechanism could conceivably be deactivated by accidentally pulling back the slider during a stabbing motion. This outcome is predictable, as the slider is grasped between the index finger and thumb and simultaneously pushed forward against resistance with the remaining fingers and the palm of the hand.

[0011] WO 2015 / 134601A1 discloses a scalpel with a blade supported by a blade holder, which can be extended from a handle by a push button or slide located in a recess in the blade holder. A locking element or pawl on the blade holder engages a locking element or receptacle in the handle when the blade is fully extended to prevent the blade from retracting under an axial backward force. The pawl is biased into this position by a leaf spring beneath the slide. The locking element can be released by pushing the slide downward against the spring's bias. This requires an unnatural finger movement, as the slide must be pushed forward against the spring's bias while simultaneously pulling backward.

[0012] A scalpel with the features of the preamble of claim 1 is described in US 5,481,804 A. Further scalpels are disclosed in WO 2015 / 134,601 A1, US 2004 / 0158,269 A1 and GB 2,432,806 A.

[0013] The preceding discussion of the background of the invention is intended only to facilitate understanding of the present invention. It should be noted that this discussion does not constitute an acknowledgment or admission that any of the documents mentioned were part of the general knowledge of the prior art at the time of priority of the application. SUMMARY OF THE INVENTION

[0014] According to the invention, a scalpel is provided comprising a handle with a longitudinally extending cavity, a blade carrier arranged within the cavity and movable longitudinally relative to the handle between a use position in which a blade carried by the blade carrier is exposed for use at an open end of the cavity, and a non-use position in which a blade carried by the blade carrier is retracted within the cavity in the handle, and a manually operable slide associated with the blade carrier and which passes through a slot in a wall of the handle at its upper edge, wherein the blade carrier is restricted to longitudinal movement within the cavity by longitudinally extending cooperating guide surfaces, wherein the scalpel is characterized in that the blade carrier or the slide has a locking surface directed rearward in the use position.wherein the locking surface, in the normal operating position of the blade carrier, is in at least partially cooperating alignment with a cooperating stop surface provided on the handle, such that a force exerted by the blade carrier in a direction corresponding to the length of the handle causes the locking surface to engage with the stop surface in order to prevent movement of the blade carrier into the cavity in the handle, and wherein the cooperating guide surfaces are configured to permit limited transverse movement of the guide surfaces relative to each other and are biased to a position in which the stop surface is at least partially cooperating with the cooperating locking surface provided on the handle, wherein the bias is configured to be overcome by a pressure exerted on the slide corresponding to a pressure required to retract the blade carrier into the handle,so that, when the blade is retracted into the handle, the locking surface and the stop surface can move past each other due to a transverse movement of the guide surfaces relative to each other.

[0015] Further features of the invention provide that the locking surface is defined by an end face of a one-piece, elastically flexible cantilever pawl formation located on a top surface of the blade carrier and extending transversely to the rear with the locking surface towards the handle and inclined upwards and rearwards to a trailing edge thereof, wherein in this case the stop surface is shaped complementarily and arranged such that it causes the cantilever pawl formation to bend upwards to promote complete engagement of the two surfaces in cases where partial alignment is present; that the stop surface is formed in a one-piece bridge at the front end of the upper edge where the handle has an endless open end to the cavity; that the longitudinally extending cooperating guide surfaces comprise at least one, preferably two, opposing,The blade carrier has longitudinally extending guide elements or grooves that interact with one or two longitudinally extending grooves or guide elements on one or both inner surfaces of the cavity, such that the guide elements and grooves guide the blade carrier for longitudinal movement along the handle, wherein in this case the grooves are slightly wider than the guide elements to ensure movement of the blade carrier away from the top of the handle.so that the locking surface can pass the stop surface when the blade is retracted into the handle by pressure on the slider. According to the invention, the preload of the blade carrier towards the top of the handle is achieved by a leaf spring formation integrally formed with the blade carrier and designed in the form of a closed, crouching loop on an edge of the blade carrier furthest from the locking surface. Preferably, the leaf spring formation has a slide supported by it, which slides on a surface of the cavity furthest from the stop surface.

[0016] The depth of the stop surface generally depends on the physical properties of the plastic used for the handle. Although the catch surface can be aligned longitudinally with the stop surface, a partially cooperating alignment is currently considered more suitable. The locking surface is laterally movable to achieve full engagement with the stop surface by forming a slightly flexible cantilever latch at one end. Typically, the depth of the stop surface in a direction transverse to the cooperating guide surfaces can advantageously be between 0.1 and 0.7 millimeters, and preferably between 0.5 and 0.6 millimeters.

[0017] The extent of a partially cooperating longitudinal alignment of the locking surface with the cooperating stop surface provided on the handle can generally be in the range of 0.1 to 0.6 millimeters and preferably 0.3 to 0.5 millimeters transversely to the length of the handle.

[0018] To ensure proper movement of the locking surface into full or partial alignment with the stop surface, the normal end position of the blade carrier is selected such that the stop surface and locking surface are separated by a gap of 0.1 to 0.6 millimeters, preferably between 0.2 and 0.5 millimeters. The arrangement is preferably chosen such that a surgeon using the scalpel cannot perceive the additional movement of the blade carrier relative to the handle when the blade carrier moves to bring the locking surface into engagement with the stop surface.

[0019] The preload of the blade carrier is designed to be overcome by normal pressure on the slide, which may correspond to that required to retract the blade carrier into the handle in a conventional and customary manner.

[0020] The movement of the blade carrier transversely to the guide surfaces is selected such that a free passage of the locking surface beyond the stop surface is ensured when the blade carrier is retracted by the intended use of the slide, and the extent of this movement can be in the range of 0.3 to 0.6 millimeters, preferably 0.5 millimeters, in cases where a partially cooperating longitudinal alignment of the locking surface with the cooperating stop surface is provided, and between 0.3 and 0.5 millimeters.

[0021] The handle is preferably formed as a one-piece molded part with a one-piece bridge defining an endless open end of the cavity through which the blade carrier can be inserted into the cavity. A separately molded slider in the blade carrier engages upon insertion through the open end of the cavity to form a blade carrier and slider assembly, with part of the slider extending through a slot along the top of the handle.

[0022] To better understand the aforementioned and other features of the invention, an embodiment will now be described with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE FIGURES

[0023] In the characters: Fig. Figure 1 is a three-dimensional view of the front area of ​​a scalpel according to the invention, but offset so that the upper edge of the handle with a scalpel blade in its outermost position of use is somewhat visible; Fig. 2 is a side view of the in Fig. 1 scalpel shown, with part of the front end of the handle shown removed; Fig. Figure 3 is a top view of the scalpel: Fig. Figure 4 is a greatly enlarged section of the front end of the [unclear text]. Fig. 1 and Fig. 2 illustrated handle and shows the distances of the relevant parts of the scalpel according to the invention; Fig. 5 is a three-dimensional view of the Fig. 4 and shows an existing pair of trapezoidal tooth formations in their mutual engagement positions; Fig. 6 is a cross-section along line VV of the Fig. 2; Fig. 7 is a cross-section along line VI-VI of the Fig. 3; Fig. Figure 8 is a greatly enlarged section showing the locking surface and the stop surface in their unlocked positions, in which insufficient force is exerted on the blade to cause movement of the blade carrier into the handle at a very small distance; and Fig. 9 is the same as Fig. Figure 8, but shows the locking surface moving in cooperative engagement with the stop surface and the slightly curved cantilever latch. DETAILED DESCRIPTION WITH REFERENCE TO THE FIGURES

[0024] In the embodiment of the invention shown in the drawings, a scalpel has a one-piece, injection-molded plastic handle (1) and a blade holder (2) which is slidable in a longitudinal cavity (3) within the plastic handle. A separately molded, manually operated slider (4), which is connected to the blade holder to which a scalpel blade (5) is attached for use, forms a blade holder assembly.

[0025] The handle has a longitudinally extending slot (6) that communicates with the cavity and extends along its functional upper edge (7) from a front end (8) of the handle to a rear end (9). A one-piece bridge (11) at the front end of the handle forms an upper edge to an endless open end of the cavity and provides dimensional stability at the front end to hold the blade holder in its extended working position.

[0026] The blade carrier is elongated and has on each side a longitudinally extending guide element (12) which engages in a cooperating groove (13) (see in particular Fig. 6) is accommodated in each side wall of the cavity, forming functional longitudinally extending, interacting guide surfaces. The blade holder is designed to slide longitudinally within the cavity and to accommodate and support a variety of different scalpel blade types. The blade holder is evidently shaped in cross-section so that it can be inserted through the open end of the cavity.

[0027] The blade carrier has a socket (14) designed to receive a one-piece tongue (15) extending from the slide, the tongue having a retaining device that irreversibly locks onto the blade carrier when the tongue is inserted through the slot into the socket with the blade carrier in the cavity. The blade carrier is thus held in the cavity and can be moved forwards and backwards by manually operating the slide, usually by a person using their thumb or forefinger while holding the scalpel handle.

[0028] The blade carrier, with an attached blade and an externally accessible slide, can be moved from a non-use state, in which the blade and blade carrier are retracted within the cavity of the handle, to a fully forward operating position by moving the slide to its fully forward position. In this position, the slide contacts a closed front end (17) of the slot, thus preventing further forward movement. When this position is reached, it is accompanied by an audible "click" indicating the full range of motion. The "click" is generated by a trapezoidal tooth formation (18) on one side of the slide, which forces a cooperating tooth formation (19) on the handle slot laterally outward, followed by a snap-back action of the cooperating tooth formation in conjunction with the formation on the slide, thereby producing the audible "click".These features are in . Fig. depicted.

[0029] In the fully forward-facing position, the sliding tooth formation lies in front of the interacting handle tooth formation, and the handle elasticity thus provides a restraining force against the backward movement of the blade holder, blade, and sliding assembly. During normal use of the scalpel, the sliding mechanism can be held by the index finger or between the index finger and thumb, depending on user preference or the procedure's requirements. This holding technique, if available, provides additional restraining force for the blade against backward movement.

[0030] Nevertheless, an additional forward locking or retaining function would be advantageous in processes requiring a high blade retention force, particularly when the slide cannot be manually held back. The forward locking or retaining function provided by this invention is automatically activated as soon as a backward bias is applied to the fully extended blade, as is typically caused by a thrusting or forward movement.

[0031] As provided by this invention, the blade carrier has a locking surface (21) directed rearward in the use position, wherein the locking surface is aligned in at least partial cooperating longitudinal direction with a cooperating stop surface (22) provided on the bridge of the handle such that the force exerted on a blade carried by the blade carrier in a direction corresponding to the length of the handle (as indicated by arrow “A” in Fig. 2 shown) causes the locking surface to engage with the stop surface in order to prevent further movement of the blade carrier into the cavity in the handle.

[0032] The locking surface is formed by an end face of a one-piece, elastically flexible cantilever pawl formation (23) located on the top of the blade carrier and extending rearward, the locking surface being perpendicular to the length of the handle. The locking surface is inclined upward and rearward to a top rear edge, such that the edge has an acute angle. The stop surface is complementary in shape. The cantilever pawl formation has limited flexibility and is arranged such that the cantilever bends upward to promote complete engagement of the locking surface and the stop surface, as shown in the Fig. This is what happens when these two surfaces meet.

[0033] The depth of the stop surface generally depends on the physical properties of the plastic used for the handle. Although the locking surface can be aligned longitudinally with the stop surface, a partially cooperating longitudinal alignment is currently considered more suitable. In this configuration, the locking surface is laterally movable to achieve full engagement with the stop surface, as it is formed at one end of a somewhat flexible cantilever latch. Typically, the depth of the stop surface in a direction transverse to the cooperating guide surfaces can range from 0.2 to 0.4 millimeters, and the corresponding size of the locking surface is at least equal to, and generally considerably larger than, the depth of the stop surface, as shown in the drawings.

[0034] The extent of a partially cooperating longitudinal alignment of the locking surface with the cooperating stop surface provided on the handle can generally be in the range of 0.1 to 0.6 millimeters, and preferably from 0.3 to 0.5 millimeters, particularly preferably about 0.45 millimeters. The extent of the partial alignment is in Fig. 8 is represented as "Z" and is measured in a transverse direction to the length of the handle.

[0035] The interacting guide surfaces of the guide elements (12) on each side of the blade carrier, which are received in the interacting grooves (13) in each side wall of the handle, are slightly undersized to allow very limited movement in one direction transverse to the length of the grooves in the handle. The blade carrier is pre-tensioned to a position closer to the top of the handle, in which the locking surface (21) is in a partially interacting longitudinal orientation along the length of the handle with the interacting stop surface (22) provided on the bridge of the handle, as shown in Fig. Figure 8 clearly illustrates the preload. The preload is designed so that it is overcome by pressure on the slide, which corresponds to the force required to retract the blade carrier into the handle, so that the locking surface and the stop surface can move past each other when the blade is retracted into the handle, when the usual movements that effect such retraction are performed.

[0036] In this embodiment of the invention, the preload of the blade carrier towards the top of the handle is achieved by a one-piece leaf spring formation (25) in the form of a crouching closed loop at an edge of the blade carrier located away from the slot. The section of the leaf spring furthest from the locking surface has a slide formation (26) that slides on a bottom surface (27) of the cavity.

[0037] To better understand the functioning of the arrangement of this embodiment of the invention, particular reference can be made to the following: Fig. 4 and Fig. 8 is referred to. When the blade carrier and the slide are in the fully forward-facing position, the spring-loaded cantilever pawl is positioned opposite the stop surface within the handle stop recess, with its locking surface at a minimal distance from the handle stop surface. This distance is in Fig. 4 is represented as gap “X” and is maintained under normal circumstances by the elasticity of the handle, which maintains contact between the interacting inclined surfaces of the trapezoidal tooth formation (18) on one side of the slide, which is forced into its end position by the interacting tooth formation (19). Typical dimensions of the gap “X” are between 0.2 and about 0.5 millimeters, with about 0.3 millimeters being preferred.

[0038] As mentioned above, the depth of the stop surface in one direction transverse to the interacting guide surfaces is indicated by the letter "W" in Fig. The depth is marked 8 and typically ranges between 0.1 and 0.7 millimeters, with a value between 0.5 and 0.6 millimeters being preferred. It should be noted that excessive depth “W” can lead to excessive bending of the cantilever latch and thus to permanent jamming in the latch. Any permanent deformation of the cantilever latch can prevent it from disengaging from the stop surface when the slide is manually pulled back.

[0039] The movement of the blade carrier transversely to the guide surfaces should be sufficient to ensure free passage of the locking surface beyond the stop surface when the blade carrier is retracted by the ordinary use of the slide, and can typically be between 0.3 and 0.6 millimeters, preferably about 0.5 mm.

[0040] To ensure proper movement of the locking surface into full or partial alignment with the stop surface, the normal end position of the blade carrier is selected such that the stop surface and the locking surface are separated by a distance in the direction of the handle length of between 0.1 and 0.6 millimeters and preferably between 0.2 and 0.5 millimeters, as indicated by the letter “X” in Fig. 4 indicated.

[0041] The movement of the blade carrier under the influence of the spring is limited by the contact between the upper blade carrier guide surface and the upper guide groove surface of the handle. The reduced width of the blade carrier guide element creates a gap between the underside of the blade carrier guide element and the underside of the handle's guide groove, the extent of which is Fig. 4 is specified as gap “Y” and in the present embodiment of the invention lies between 0.3 and 0.6 millimeters, preferably about 0.5 mm.

[0042] When a backward force is applied to the blade, blade carrier, and slider, the spring-loaded pawl locking surface contacts the inclined stop surface of the handle end stop. The resulting force vector causes the pawl to bend upward, increasing the contact area between the locking surface and the stop surface to a maximum. This maximum is achieved when the upper edge of the locking surface is fully engaged in the stop recess, thus ensuring a positive locking of the blade carrier assembly.

[0043] When the force exerted backward on the blade carrier assembly is released, the forward spring force caused by the interaction of the inclined surfaces of the trapezoidal teeth restores the gap "X". During this movement, the end of the spring-loaded latch releases from the handle stop surface, thus disengaging the forward locking mechanism.

[0044] Due to the natural effect of the slide retracting backwards and the slide's profile geometry, a downward force vector is applied to the slide during this process. This force vector causes a transverse movement of the blade carrier assembly against the resistance of the blade carrier leaf spring.

[0045] The gap between the distant edges of the grooves (gap "Y") is thereby reduced to zero, allowing the blade carrier spring latch to pass the handle stop surface unimpeded. The gap "Y" must obviously be greater than or equal to, preferably greater than, the alignment "Z" of the locking surface with the stop surface to ensure retraction of the blade carrier assembly. Activation and deactivation are repeatable.

[0046] The scalpel offers several improvements and advantages over the state of the art. During normal use of the blade holder, the spring-loaded pawl does not engage the handle stop, regardless of whether the blade is extended or retracted. This is because the pressure applied to the blade holder's operating slide ensures that the spring-loaded pawl always passes under the handle stop without engaging it. The spring-loaded pawl can be considered inactive regardless of whether the blade holder is in the unused or used position, as it is only actuated or spring-loaded when a backward force is applied to the blade holder. Thus, no unnecessary tension is exerted on the spring-loaded pawl, providing the user with a very smooth and natural feel.

[0047] Similarly, the spring-loaded pawl does not engage the handle's stop surface unless axial pressure is applied to the blade. This further ensures that the spring-loaded pawl is not weakened or damaged, for example, by repeated use of the blade holder. Furthermore, no direct pressure is applied to the spring-loaded pawl to allow the blade holder and blade to retract into the handle. Instead, the spring-loaded pawl is moved by pressure on the blade holder. This not only ensures very smooth operation but also prevents the spring-loaded pawl from being subjected to forces, particularly bending forces, that could weaken or break it.

[0048] Furthermore, the leaf spring is not under tension or preload when the blade carrier is in the upward-preloaded position, regardless of whether the blade carrier is retracted or extended. Rather, the leaf spring ensures that the blade carrier returns to its upward or resting position after a transverse movement, under the pressure exerted on the slide. The leaf spring is therefore only tensioned for the duration of the blade carrier's forward or backward movement. This ensures that the leaf spring is not weakened or permanently deformed by continuous stress.

[0049] Another advantage of the scalpel is that the forward locking mechanism cannot be accidentally disengaged by pulling back the slider during a stitching operation. Any backward support provided by the slider during a stitching operation with the forward locking mechanism engaged would only reinforce the blade retention. Once the blade encounters axial resistance, it moves the blade holder backward, causing the locking surface of the spring-loaded pawl to engage with the stop surface and preventing it from being released by downward and backward movement. Only by releasing the axial backward force on the blade and allowing the locking surface of the spring-loaded pawl to move forward and disengage from, and away from, the stop surface, is the forward lock or retainer allowed to be released, thus enabling the blade and blade holder to retract into the handle.

[0050] It is understood that numerous modifications can be made to the embodiment of the invention described above without altering its scope. For example, the locking surface could be provided on the slider instead of on the blade carrier. Furthermore, it should be noted that the application of the invention is not limited to the type of retractable scalpel described above and can be applied to numerous other embodiments, shapes, and configurations of scalpels. Likewise, the dimensions given above for the various gaps and spaces are purely indicative of the size relationships and should not be interpreted as limiting the scope of the invention.

[0051] Throughout this description and these claims, unless the content requires otherwise, the word "comprehensive" or variations such as "encompassing" or "encompassing" shall be understood to imply the inclusion of a particular number or group of numbers, but not the exclusion of any other number or group of numbers.

Claims

[1] Scalpel comprising a handle (1) with a longitudinally extending cavity (3), a blade carrier (2) arranged within the cavity (3) and movable longitudinally relative to the handle (1) between a use position in which a blade (5) carried by the blade carrier (2) is exposed for use at an open end (8) of the cavity (3) and a non-use position in which a blade (5) carried by the blade carrier (2) is retracted within the cavity (3) in the handle (1), and a manually operable slide (4) associated with the blade carrier (2) and which passes through a slot (6) in a wall of the handle (1) at its upper edge (7), wherein the blade carrier (2) is restricted to longitudinal movement within the cavity (3) by longitudinally extending cooperating guide surfaces (12, 13), wherein the scalpel characterized byis that the blade carrier (2) or the slide (4) has a locking surface (21) directed rearward in the operating position, wherein the locking surface (21) in the operating position of the blade carrier (2) is in at least partially cooperating alignment with a cooperating stop surface (22) provided on the handle (1), such that a force exerted on the blade carrier (2) in a direction corresponding to the length of the handle (1) causes the locking surface (21) to engage with the stop surface (22) in order to prevent movement of the blade carrier (2) into the cavity (3) in the handle (1), and that the cooperating guide surfaces (12, 13) are configured to allow a limited transverse movement of the guide surfaces (12, 13) relative to each other and are biased to a position in which the stop surface (22) is at least partially cooperating with the cooperating locking surface (21) provided on the handle (1).wherein the preload is designed to be overcome by a pressure exerted on the slide (4) corresponding to the pressure required to retract the blade carrier (2) into the handle (1), so that the locking surface (21) and the stop surface (22) can move past each other when the blade (5) is retracted into the handle (1) as a result of a transverse movement of the guide surfaces (12, 13) relative to each other, characterized by , that a pre-tensioning of the blade carrier (2) towards the top of the handle (1) is achieved by a one-piece leaf spring formation (25) which is in a sliding relationship relative to a lower surface of the cavity (3), and wherein the one-piece leaf spring formation (25) is arranged in the form of a crouching closed loop on a side of the blade carrier (2) away from the locking surface (21). [2] The scalpel according to claim 1, wherein the locking surface (21) is defined by an end face of a one-piece, elastically flexible cantilever pawl formation (23) located on a top side of the blade carrier (2) and extending transversely to the rear with the locking surface (21) towards the handle (1). [3] The scalpel according to claim 2, wherein the locking surface (21) is inclined upwards and backwards towards a rear edge of the cantilever pawl formation (23) and the stop surface (22) is shaped complementarily and arranged such that it causes the cantilever pawl formation (23) to bend upwards to promote complete engagement of the two surfaces. [4] The scalpel according to one of the preceding claims, wherein the stop surface (22) is formed in a one-piece bridge (11) at the front end of the upper edge (7) of the handle (1), where the handle has an endless open end (8) to the cavity (3). [5] The scalpel according to one of the preceding claims, wherein the longitudinally extending cooperating guide surfaces (12, 13) have at least one longitudinally extending guide element (12) or groove (13) on the blade carrier (2) which cooperate with a longitudinally extending groove (13) or guide element (12) on an inner surface of the cavity (3), such that the guide elements (12) and grooves (13) guide the blade carrier (2) for a longitudinal movement along the handle (1), wherein in this case the groove (13) is slightly wider than the guide element (12) to ensure movement of the blade carrier (2) away from the top of the handle (1) so that the locking surface (21) can pass the stop surface (22) when the blade (5) is retracted into the handle (1) by pressure on the slider (4). [6] The scalpel according to claim 5, wherein a guide element (12) or a groove (13) is provided on each of the two opposite sides of the blade carrier (2) with a cooperating groove (13) or guide element (12) in each of the two opposite sides of the cavity (3). [7] The scalpel according to claim 1, wherein the leaf spring formation (25) has a slide formation (26) carried by it to contact a cooperating surface (27) of the cavity (3). [8] The scalpel according to one of the preceding claims, wherein the extent of the at least partially cooperating alignment (“Z”) of the locking surface (21) with the cooperating stop surface (22) provided on the handle (1) is in the range of 0.1 to 0.6 millimeters. [9] The scalpel according to any of the preceding claims, wherein the depth (W) of the stop surface (22) in a direction transverse to the interacting guide surfaces (12, 13) is in a range between 0.1 and 0.7 millimeters. [10] The scalpel according to any of the preceding claims, wherein the handle (1) is formed as a one-piece molded part with a one-piece bridge (11) defining an endless open end (8) of the cavity (3) through which the blade carrier (2) can be inserted into the cavity (3) and a separately formed slider (4) is engaged with the blade carrier (2) after its insertion through the open end (8) of the cavity (3) to form a blade carrier (2) and a slider assembly, wherein a part of the slider (4) extends through the slot (6) along the top of the handle (1).

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