In many personal and industrial applications, safety knives are desirable to prevent user laceration both before a cut is made and immediately subsequent to a cut. These safety knives may be disposable or designed for extended use. The knives that are used for extended periods may have replaceable blades or blade cartridges so that the handle and related safety apparatus may be reused while still maintaining a sharp cutting edge. The disposable knives may have the blade permanently attached to within the safety knife, so that the knife is discarded once the blade becomes dull. For example, the disposable knife is desirable in the food services industry, where loose blades from replaceable blade knives may find their way into the food product. A permanently attached blade forces the user to discard the entire knife rather than just change the blade. To reduce replacement costs incurred by the customer, these disposable knives are often made of inexpensive plastic materials with the least possible number of injection molded parts and moving parts.
Some safety knives have blade covers that may be retracted upon actuation of a trigger or similar actuation means. When locked, these blade covers are prevented from retracting due to the blade cover movement being blocked by a pawl-like mechanism that engages a stop. Only after being disengaged from the stop, can the blade cover be retracted to expose the blade. Some of these newer safety knives further include features that permit just one blade cover retraction for each trigger pull. If the trigger is continuously pressed after the blade cover has been retracted rather than released, the blade cover will still become locked in the extended position. Only after releasing the trigger and depressing the trigger a second time will the blade cover be permitted to retract once again.
The single-use per press feature has been achieved at this point through use of complex mechanisms that require tight tolerances and close fits between parts. For example, much of the art has required the use of one-way ramp features, such that a moving part must ride up the ramp feature, thereafter falling off a ledge so that the part may not return to the previous position until a second actuation has occurred. This ramped design requires the moving part to be closely and exactly situated relative to the ramp feature. The ramped feature must be small, however, so that movement of the moving part up the ramp is not unduly hindered. Further, many current designs require flexible plastic parts, which tend to fatigue and slightly change shape, causing parts to eventually lose contact or move out of optimal alignment. Small features combined with close tolerances between moving parts create a safety mechanism that is relatively expensive to manufacture, and potentially unreliable due to part fatigue.
Since many of the safety knives are disposable or otherwise have short lives, any added expense greatly detracts from the competiveness of the knife. It is desirable to eliminate tight tolerances when the product is disposable to ultimately reduce costs and encourage timely disposal of the knife to prevent usage when dull. It is desirable to have a safety knife that is inexpensive to manufacture and more reliable due to the loosening of tolerances, reduction in parts and overall simplification of the mechanism.
The present utility knife is an entirely new and creative design, offering significant advantages over the prior art. The safety mechanism operates within the utility knife that has a blade extending from the knife. A retractable shield protects the user from the cutting edge of the blade. When a strut is in a safety position, it is engaged between the shield and a bracket so that the shield is prevented from retracting to expose the cutting edge. A separable linkage extends between an actuator and the strut. The separable linkage comprises a seat member and a corresponding deflecting member that are linked together when the actuator is not depressed and the strut is in the safety position. The separable linkage is configured to transmit the pressing action of the actuator to the strut to disengage it from the bracket. Once the strut is displaced from the bracket, retracting the shield causes the strut to move relative to the bracket substantially in the longitudinal direction, causing a delinking of the seat member and the deflecting member. If the actuator continues to be pressed in after the shield returns from being retracted, the safety mechanism prevents relinking of the seat member and the deflecting member due to the deflecting member being deflected away from the seat member in a substantially longitudinal direction.
Alternately, the safety mechanism operates within a utility knife that has a blade extending from the knife. A retractable shield protects the user from the cutting edge of the blade. When a strut is in a normal position, it is braced between the shield and a stop so that the shield is prevented from retracting to expose the cutting edge. A separable linkage has a first member and a second member which have a linked mode where they are in compressive alignment. When in compressive alignment, the first member and the second member are aligned so that actuation of the trigger disengages the strut form the stop. The separable linkage additionally has a delinked mode where the first member is moved out of compressive alignment with the second member.
Often, the user (300) will draw the knife (100) towards himself during the cutting process. Upon reaching the edge of the workpeice (400) the blade (104) exits the workpeice (400) and the resistive drag of the workpeice (400) on the blade (104) is eliminated, often causing the knife (100) within the user's hand to leave the workpeice (400) with great velocity towards the user's body. The shield (106) is biased to immediately extend to cover the blade (104) upon losing contact with the workpeice (400).
For the user's convenience, a tape splitter (128) may be formed on the aft end of the knife (100). The tape splitter (128) extends from the body (132), has a tip (190) for piercing the tape, and has an edge (192) generally sharp enough to split the tape but not sharp enough to cut the user. The tape splitter (128) is preferably integrally molded on the aft end of one of the shells (134, 136). For example,
An exploded perspective view of the present utility knife (100) is illustrated in
A blade holder (108) is provided for securely holding the blade (104) which extends from the body (132). On each side of the blade holder (108) is a tubular post (162) with an internal diameter sized to fit over a post (158) and post (159) formed on the respective interiors of each of the shells (134, 136). To create four points of attachment to the body (132), the blade holder (108) is provided with tubular posts (163) on each side. The tubular post (163) internal diameter is sized to fit over post (168) and an external diameter sized to be inserted within hollow boss (166), corresponding to opposing post (169) and hollow boss (167). The four attachment points provided by the two sets of tubular posts (162, 163) insure secure mounting of the blade holder (108) within the body (132). The blade holder (108) is preferably injection molded about the metal blade (104), forming an integral blade assembly. The blade (104) may have various holes formed though it that correspond to the tubular posts (162) of the blade holder (108) or for permitting the injected plastic to flow through to further secure the blade (104) to the blade holder (108). The blade holder (108) may be molded from any suitable material, such as nylon, acetal, ABS, or other durable and, optionally, resilient polymers. The blade holder (108) may either be permanently secured within the body (132) as illustrated in the shown embodiment or may configured to be replaceable, where the blade holder (108) and blade (104) are temporarily secured by a latch mechanism or the like.
Extending from the rear of the blade holder (108) is a flexible arm (154) designed to contact and press down upon a lip (138) formed on the trigger (110) to bias the trigger (110) so that it normally extends through opening (174) on the first shell (134) and corresponding opening (175) on the second shell (136). The flexible arm (154) is a spring element designed to keep the trigger (110) fully extended when not actuated. As the trigger (110) is depressed, the lip (138) bends the flexible arm (154) to provide slight resistance to the user's input. Upon releasing the trigger (110), the flexible arm (154) rebounds and returns the trigger (110) to fully extended state. The trigger (110) may be alternatively biased in numerous ways, as is known in the art, such as using metal or plastic leaf springs, torsion springs, or the like. The trigger (110) hinges on the body (132) on a post (170) formed on the first shell (134) and corresponding post (171) formed on a second shell (136).
The shield (106) is shown as generally being wedge-shaped with a slot formed through it to accommodate the blade (104) and blade holder (108). A bearing (194) or through hole is formed through each side of the shield (106) and correspond to the external diameters of tubular posts (162) to form a plain bearing, permitting rotation of the shield (106) about the hollow posts (162). The backs (164) of the shield (106) are configured to contact the knob (156) and knob (157) formed on the forward end (116) of the strut (114) so that the knobs (156, 157) follow and ride the backs (164) as the shield (106) retracts and extends. Although not required, the shield (106) is preferably injection molded using a transparent material so that the user may see location of the blade (104) through the extended shield (106). The clear shield (106) also aids in detecting and clearing contamination of the blade (104). The ability to maintain a clean blade (104) and shield (106) is a desirable feature in the food service industry.
The strut (114) has a forward end (116) and an aft end (118), and is generally elongate in shape. At the forward end (116), a knob (156) extends from each side of the strut (114) in a direction generally horizontally transverse to the longitudinal or lengthwise axis of the strut (114). Each knob (156) is sized to fit within a corresponding arced groove (148) formed on each of the interiors of the shells (134, 136). The arced grooves (148) may be formed on the interior surface by forming a wall to enclose a kidney-shaped area. A coil spring (112) is attached between the strut (114) and the blade holder (108) to generally bias the strut (114) to the forward direction and the downward direction towards the trigger (110). However, one or more springs may be attached to the strut (114) by one end and numerous other suitable points by the other end for biasing the strut (114) and shield (106). Under the bias of the spring (112), the knobs (156) normally push upon the backs (164) of the shield (106) to bias the shield to extend over the blade (104), where the knobs (156) are located at the forward end of the arced grooves (148). As the shield (106) is retracted, the backs (164) contact and push the knobs (156) and strut (114) longitudinally in the aft direction against the bias of the spring (112).
Extending from the underside (196) of the strut (114) is a deflecting member (122). The deflecting member (122) is preferably molded integrally with the strut (114) and is cantilevered therefrom. The structure of the strut (114) can be seen in more detail when looking at
The strut (114) may be constructed with various designs. One of the primary purposes of the strut (114) is to provide a substantially rigid linkage between the shield (106) and the shelf or bracket (144) to prevent the shield (106) from retracting to expose the blade (104), unless the user (300) has actuated the trigger (110). The forward end (116) of the strut (114) is linked with the shield (106) through sliding contact as shown, or may be hinged on the shield (106) with a clevis joint arrangement or similar connection. Additionally, the shield (106) and strut (114) may be molded integrally with a joint or thinned section to permit rotation of the shield (106) and strut (114) relative to one another. A hump (178) or arced section of the strut (114) may be included to provide clearance for lengthening the deflecting member (122) design to change bending characteristics.
A stop, shelf or bracket (144) is molded integrally on the interior wall of at least one of the first shell (134) or the second shell (136). Here, in
The trigger or actuator (110) can be seen with greater detail in
A seat member (124) is formed on the trigger and is optionally shown as being generally stepped-shaped. A generally horizontal surface forms a seat portion (184) with an adjacent vertical wall forming a deflecting portion (186). A vertical section rising above the seat portion (184) forms a limiter (188). The limiter (188) is configured to prevent the tip (182) of the deflecting member (122) from moving in an undesired direction. The limiting function can be provided by the limiter (188) on the seat member (124) or on the deflecting member (122), where a mechanical interference is created between the seat member (124) and deflecting member (124) to control the flexing or movement of the deflecting member (124) tip (182). The exact function of the seat member (124) relative to the deflecting member (122) will be discussed in greater detail below, in reference to
A channel (126) may be formed along the length of the trigger (110) for receiving the deflecting member (122) there within and accommodating the forward and aft travel of the deflecting member (122). The deflecting member (122) may move substantially linearly in the forward and aft directions relative to the seat member (124). Extending upwards from the trigger (110) are optional flexible arms (140), designed to deflect in a direction perpendicular to the plane through which the trigger (110) rotates. The flexible arms (140) are tab-like in construction and are molded integrally with the trigger (110).
Looking at
When the knife (100) is locked, the aft end (118) of the strut (114) is engaged or adjacent to the bracket (144) to prevent the retraction of the shield (106), as seen in
With the trigger (110) depressed, the strut (114) is lifted or slightly rotated about knobs (156), where the aft end (118) is lifted above the wall (176) portion of the bracket (144), and corresponding wall portion (177) on second shell (136), so that the bracket (144) no longer obstructs the aft movement of the strut (114). In this unlocked configuration, the user (300) is permitted to begin cutting the workpeice (400) by applying the shield (106) to the workpeice surface to cause retraction of the shield (106).
As the strut (114) travels in the aft direction, the tip (182) likewise slides aft on the seat portion (184) until reaching the rightmost edge (as viewed in the figure) of the seat portion (184), where the tip (182) drops off the seat portion (184), so that the seat member (124) is no longer supporting the defecting member (122) and the two are therefore disengaged or in the delinked mode. Since the deflecting member (122) no longer can provide a lifting force to the strut (114), the strut (114) drops downward and the aft end (118) of the strut (114) is thereafter supported atop the bracket (144) on slide (146), and corresponding slide (147) on the second shell (136). At this point, the strut (114) may be further pushed in the aft direction by the further retraction of the shield (106), where the aft end (118) slides along the slide (146), as seen in
Once a cut has been completed and the shield (106) removed from the workpeice (400), the shield (106) is biased to immediately extend back over the blade (104), as illustrated in
Observing
Because the deflecting member (122) bends in the aft direction, opposite of the direction of the strut's (114) longitudinal travel or path, the strut (114) is permitted to return to engagement with the bracket (144). So, the deflecting member (122) preferably should have structural characteristics that permit axial loads to be transmitted axially through it without significant buckling and permit bending when a lateral load is applied near the free end or tip (182). In this case, the lateral load or force is provided by the spring (112) pulling forward to cause an aft deflection (D). The deflection (D) is sufficient to enable the forward transition of the strut (114) shown from
The knife (100) will remain locked until the user (300) releases the trigger (110) and depresses the trigger (110) a second time. For example, when the user releases the trigger (110), the knife (100) will return to the configuration shown in
A unique and advantageous interaction is created between the deflecting member (122) and the seat member (124); when linked the deflecting member (122) transmits an axially-directed force from the seat member to the strut (114) during unlocking and when unlinked a lateral force deflects the deflecting member (122) to prevent the relinking of the deflecting member (122) and seat member (124). Because the deflection (D) in this example is opposite of the strut's (114) forward movement and no precise mating of deflecting parts in required, the looser tolerances are possible while maintaining reliable operation. This overall, among other important advantages, reduces complexity and cost of manufacturing, while maintaining performance, which is paramount in the disposable knife industry.
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