Abstract:
A utility knife system comprises a handle assembly, a blade assembly, and a protective blade cover. The handle assembly and the blade assembly have complementary latching mechanisms for easy exchange of blades without opening the handle. The protective blade cover functions cooperatively with the handle assembly and blade assembly to ensure that a user does not touch the cutting edges of blades while exchanging them.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 08/868,438, filed on Jun. 4, 1997, now abandoned. 
    
    
     BACKGROUND OF INVENTION 
     This invention relates to a utility knife system, which comprises a knife handle, exchangeable blades, and protective covers for the blades. 
     Utility knives are versatile cutting tools that feature a blade slidable in and out of a knife handle. Typically, to replace the blade of a utility knife when the blade becomes dull, a user must unscrew and open the utility knife handle to gain access to the blade. 
     To make the replacement of blades more convenient, various configurations for utility knives for which the blades may be replaced without opening the knife handle are known. For example, in U.S. Pat. No. 3,577,637, filed by Braginetz on Sep. 24, 1968 and issued on May 4, 1971, a utility knife is disclosed containing a blade carrier with a resilient portion that can be moved laterally by a tab. The resilient portion contains a lug that engages certain notches on the blade. 
     As another example, U.S. Pat. No. 3,025,598, filed by Nissen on Oct. 13, 1958 and issued on Mar. 30, 1962, discloses a utility knife having a blade with a rounded, knob-like end. The utility knife handle contains a blade carrier having a resilient upper portion. The upper portion of the blade carrier contains a shoulder. When the blade is inserted into the handle, the rounded end of the blade exerts a downward force on the shoulder, causing the upper portion to depress. When the rounded end passes the shoulder, the upper portion springs back to its normal position, causing the shoulder to engage the rear of the rounded end. To disengage the blade, the upper portion is depressed using a tab coupled to the upper portion. 
     In each of the above-described known configurations for replacing blades within a utility knife handle, a risk exists that a user may cut himself or herself while replacing a blade because the cutting edge of the blade is left exposed. To date, therefore, each configuration for replacing blades within a utility knife involves a safety risk to the user. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a utility knife system that is simple and inexpensive to manufacture and provides a convenient and safe configuration for quickly exchanging blades without opening the handle. According to the present invention, a utility knife system comprises a handle assembly, a blade assembly, and a protective blade cover. 
     The handle assembly comprises an elongated housing, a guide, and a tab. The elongated housing has an internal chamber, a blade opening at an end of the housing for receiving a blade, and a slot disposed parallel to the longitudinal axis of the housing for access to the internal chamber. The guide is located within the housing and is slidable along the longitudinal axis of the housing. The guide comprises a first latching mechanism disposed on the side facing the blade opening. The tab is attached to the guide and extends out of the slot in the housing. The tab is used for controlling the movement of the guide. 
     The blade assembly comprises a blade and an endpiece. The blade has a cutting edge and two ends disposed on opposite sides of the cutting edge. The endpiece is attached to one of the two ends of the blade and has second and third latching mechanisms, the second latching mechanism being complementary to the first latching mechanism of the handle assembly guide. 
     The protective blade cover comprises an enclosed hollow structure with an opening for receiving the blade assembly. The hollow structure has inner dimensions such that the protective blade cover fits securely over the blade assembly and outer dimensions such that the protective blade cover completely covers the cutting edge of the blade assembly while leaving exposed the second latching mechanism of the endpiece. The protective blade cover also has a fourth latching mechanism complementary to the third latching mechanism of the endpiece. 
     To store a blade assembly, the protective blade cover is inserted over the blade assembly and the fourth latching mechanism of the protective blade cover is engaged with the third latching mechanism of the endpiece. 
     To load a blade assembly into the handle assembly, after the blade assembly has been stored in the protective blade cover, the endpiece of the blade assembly is inserted into the blade opening of the handle assembly housing, the second latching mechanism of the endpiece is engaged with the first latching mechanism of the handle assembly guide, and the fourth latching mechanism of the protective blade cover is disengaged from the third latching mechanism of the endpiece. 
     To unload a blade assembly from the handle assembly, the protective blade cover is inserted over the blade assembly, the fourth latching mechanism of the protective blade cover is engaged with the third latching mechanism of the endpiece, and the first latching mechanism of the handle assembly guide is disengaged from the second latching mechanism of the endpiece. 
     Preferably, the handle assembly further comprises a blade release button coupled to the guide for enabling the disengagement of the first latching mechanism of the guide from the second latching mechanism of the blade assembly endpiece. 
     Preferably, the slot in the handle assembly housing comprises a plurality of notches along its sides. Preferably, the tab comprises two resiliently yieldable prongs parallel to the longitudinal axis of the slot, each prong having a bulge portion that is engageable with at least one of the notches. Preferably, the handle assembly further comprises a lock arranged in a slidable relationship with the tab, the lock having a post that slides between the bulge portions of the tab prongs and prevents the bulge portions from yielding inwardly towards each other. 
     Preferably, the handle assembly guide comprises a first portion and a second portion, the first portion being resiliently yieldable with respect to the second portion. Preferably, the first latching mechanism comprises a hook on the first portion facing the blade opening of the handle assembly housing, and the second latching mechanism comprises a hook complementary to that of the first latching mechanism. 
     Preferably, the third latching mechanism of the blade assembly endpiece comprises an indentation in an outer surface of the endpiece and the fourth latching mechanism of the protective blade cover comprises a protrusion complementary to the indentation, the protrusion mounted on a resiliently yieldable member of the protective blade cover. 
     Preferably, the outer dimensions of the protective blade cover are larger than those of the blade opening in the handle assembly housing. 
     Preferably, the protective blade cover further comprises a first side wall and a second side wall parallel to each other, an elongated projection on an outer surface of the first side wall having a substantially constant cross-section throughout its length, and one or more projections on an outer surface of the second side wall defining a slot for slidably receiving an element having the same shape as the elongated projection on the first side wall. 
     These and other features, aspects, and advantages of the present invention will become better understood with regard to the following detailed description, appended claims, and accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a utility knife system according to a preferred embodiment of the present invention; 
     FIG. 2 is a three-dimensional perspective view of a blade assembly and a protective blade cover, both according to a preferred embodiment of the present invention, which are disengaged from each other; 
     FIGS. 3 and 4 are three-dimensional perspective views of a blade assembly and a protective blade cover, both according to a preferred embodiment of the present invention, which are engaged with each other; 
     FIG. 5 is a three-dimensional perspective view of a utility knife system according to a preferred embodiment of the present invention with a plurality of protective blade covers interconnected with each other; 
     FIG. 6 is a top view of a utility knife system according to a preferred embodiment of the present invention with a plurality of protective blade covers interconnected with each other; 
     FIG. 7 is a three-dimensional perspective view of a housing half of a utility knife system according to a preferred embodiment of the present invention; 
     FIG. 8 is a three-dimensional perspective view of another housing half of a utility knife system according to a preferred embodiment of the present invention; 
     FIG. 9A is a three-dimensional perspective view of a tab of a utility knife system according to a preferred embodiment of the present invention; 
     FIG. 9B is a top view of a tab of a utility knife system according to a preferred embodiment of the present invention; 
     FIG. 10A is a three-dimensional, top perspective view of a lock of a utility knife system according to a preferred embodiment of the present invention; 
     FIG. 10B is a three-dimensional, bottom perspective view of a lock of a utility knife system according to a preferred embodiment of the present invention; 
     FIG. 11A is a three-dimensional, top perspective view of a tab, lock, and guide of a utility knife system according to a preferred embodiment of the present invention; 
     FIG. 11B is a three-dimensional, bottom perspective view of a tab, lock, and guide of a utility knife system according to a preferred embodiment of the present invention; 
     FIG. 12A is a three-dimensional perspective view of a first endpiece half of a utility knife system according to a preferred embodiment of the present invention; 
     FIG. 12B is a three-dimensional perspective view of a blade of a utility knife system according to a preferred embodiment of the present invention; 
     FIG. 12C is a three-dimensional perspective view of a second endpiece half of a utility knife system according to a preferred embodiment of the present invention; and 
     FIG. 13 is a three-dimensional perspective view of a plurality of protective covers integrally formed in a side-by-side relationship according to a preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     As shown in the drawings, and in particular FIGS. 1 and 2, a utility knife system according to a preferred embodiment of the present invention comprises a handle assembly 10, a blade assembly 20, and a protective blade cover 30. 
     The handle assembly 10 comprises an elongated housing 12, a guide 14, a tab 16, a lock 17, and a blade release button 18. The elongated housing 12 is a hollow structure composed of two substantially identical halves 12a and 12b (as shown in FIGS. 7 and 8). Preferably, the housing halves 12a and 12b are joined together by a screw, and the halves include bores 125a and 125b through their centers through which the screw is passed. The bores may be unthreaded and a nut may be used in combination with the screw to hold the two halves together, or the bores may be threaded to hold the two halves together without the need for a nut. To assist in aligning the two halves, housing half 12a has flanges 121 and housing half 12b has flange receptacles 127. As an alternative to a screw, any suitable means of attaching the two halves together may be used. Preferably, the housing halves 12a and 12b are made by the die casting of a metallic material, such as ZAMAK. 
     The elongated housing 12 contains a blade opening 122 at one end. In addition, along its top edge, the elongated housing 12 includes a button opening 124 and a slot opening 126. The button opening 124 accommodates the blade release button 18, and the slot opening 126 is a lengthwise slot in which the tab 16 and lock 17 slide back and forth. Preferably, the slot opening 126 contains a series of notches 19 along its sides (as best shown in FIG. 6). 
     The tab 16 is attached, through the slot opening 126, to the guide 14 and is integral therewith. Alternatively, the tab 16 may be fixedly attached to the guide 14 using any suitable attachment means. As shown in FIG. 9A, the tab 16 preferably comprises an upper base 165, which is attached to the guide 14 through a column 164. Between the base 165 and the guide 14, two parallel prongs 161a and 161b extend rearwardly from the column 164. The prongs 161a and 161b are resiliently yieldable with respect to each other. 
     As shown in FIGS. 9A and 9B, the prongs 161a and 161b have outwardly bulging portions 162a and 162b, respectively, near their ends. In addition, prong 161a has an inwardly bulging portion 163 at its end. The outwardly bulging portions 162a and 162b fit within the notches 19 along the sides of slot 126. 
     As shown in FIGS. 10A and 10B, the lock 17 comprises a base 175 having two forwardly extending prongs 171a and 171b. A post 173 is attached underneath and at the forward end of the base 175. The width of the post 173 is approximately the space between the prongs 161a and 161b. 
     FIGS. 11A and 11B show the engagement of the tab 16 with the lock 17. The lock prongs 171a and 171b slide between the tab base 165 and the tab prongs 161a and 161b. The post 173 is inserted between the tab prongs 161a and 161b. In this arrangement, the lock 17 is capable of a limited sliding movement with respect to the tab 16. At the lock&#39;s forward-most position, the lock base 175 abuts the tab base 165. At the lock&#39;s rear-most position, as shown in FIG. 11B, the lock post 173 abuts the tab&#39;s inwardly bulging portion 163. 
     In operation, when the lock 17 is in its forward-most position, the lock post 173 abuts the column 164 and does not block the outwardly bulging portions 162a and 162b from yielding inwardly, as a result of passing over the ridges formed by the notches 19, when the tab 16 is moved in the slot opening 126. Thus, when the lock 17 is in its forward-most position, the tab 16 is unlocked and is capable of movement within the slot opening 126. 
     In contrast, when the lock 17 is in its rear-most position, the lock post 173 is positioned in between the outwardly bulging portions 162a and 162b. In this position, the lock post 173 prevents the outwardly bulging portions 162a and 162b from yielding inwardly. Thus, the bulging portions cannot pass over the ridges formed by the notches 19, and the tab 16 is locked and cannot move within the slot opening 126. 
     The guide 14 consists of two portions, a base lower portion 142 and an upper portion 146. The upper portion 146 is resiliently yieldable with respect to the lower portion 142. On the side facing the blade opening 122, the lower portion 142 contains a horizontally projecting member 144 and the upper portion 146 contains an upwardly pointing hook 148. The upper portion 146 also contains a vertical post 149 near its center. When the tab, and correspondingly, the guide are moved to their forward-most position (defined by the side on which the blade opening 122 is located), the vertical post 149 sits beneath the blade release button 18. In this position, the blade release button may be operated to depress the resiliently yieldable upper portion 146. 
     Preferably, the guide 14, the tab 16, and the lock 17 are made by the injection molding of a plastic material, such as glass-fiber-coupled polypropylene sold by Hoechst UK, Ltd., Wolton, UK, under the trade name HOSTACOM. Preferably, the blade release button 18 is made by the injection molding of a plastic material, such as polypropylene sold by BASF, UK, Cheadle, UK, under the trade name NOVALIN. 
     Referring to FIGS. 2, 12A, 12B, and 12C, the blade assembly 20 comprises a blade 22 and an endpiece 24. The blade 22 may be any standard stainless steel or carbon steel blade. As shown in FIG. 12B, the blade 22 has three holes, 221a, 221b, and 221c, for attachment of the blade 22 to the endpiece 24. Again referring to FIGS. 12A and 12C the endpiece 24 preferably comprises two pieces, an endpiece base 24a and an endpiece cover 24b. The endpiece base 24a contains three projections 25a, 25b, and 25c, which fit through the blade holes 221a, 221b, and 221c, respectively. The endpiece cover 24b contains three recesses 26a, 26b, and 26c, which receive the projections 25a, 25b, and 25c. As shown, the configuration of the endpiece 24 is such that, when the endpiece 24 is permanently attached to the blade, the cutting edge 222 of the blade is left exposed. 
     Preferably, the endpiece 24 is made by the injection molding of a plastic material, such as polycarbonate sold by GE Plastics, Pittsfield, Mass., USA, under the trade name LEXAN. The attachment of the endpiece 24 to the blade may be accomplished by, for example, radio frequency induction heating, ultrasonic welding, or integral rivets. 
     As shown in FIG. 2, the upper and lower surfaces of the endpiece contain two indentations, 242a and 242b, respectively. In the preferred embodiment shown in FIG. 2, the indentations are grooves that run transverse to the cutting edge 222 of the blade. 
     The rear of the endpiece 24 contains a horizontally projecting lower member 246 and a downwardly pointing hook 244. The area where the horizontally projecting lower member 246 joins the endpiece 24 defines a recessed area 248. The hook 244 of the endpiece is complementary to the hook 148 of the handle assembly guide. 
     Referring still to FIG. 2, the protective blade cover 30 is a hollow structure defined by two sets of parallel walls and an end wall 38 (shown in FIG. 1) connecting the parallel walls. The two sets of parallel walls consist of a set of side walls, 32a and 32b, and a top wall 34 and bottom wall 36 (shown in FIG. 1). The walls are dimensioned to fit over the blade assembly 20 securely and to cover completely the cutting edge 222 of the blade when the blade assembly 20 is inserted into the protective blade cover 30. At the same time, the walls are dimensioned to leave exposed the hook 244 and the horizontally projecting member 246 when the blade assembly 20 is inserted into the protective blade cover 30. Preferably, the protective blade cover 30 is made by the injection molding of a plastic material, such as polystyrene sold by BASF UK, Cheadle, UK, under the trade name POLYSTYROL. 
     The top wall 34 and the bottom wall 36 (shown in FIG. 1) contain two resiliently yieldable members 342 and 362, respectively, As shown in FIGS. 1 and 2, these members may be, for example, two thin planks of plastic that are joined to the top and bottom walls at one end only. The resiliently yieldable members 342 and 362 have protrusions 344 and 364, respectively (as shown in FIG. 1). The protrusion 344 on member 342 extends downward toward the bottom wall 36, and the protrusion 364 on member 362 extends upward toward the top wall 34. The protrusions 344 and 364 are complementary to the grooves 242a and 242b, respectively. Therefore, when the blade assembly 20 is inserted into the protective blade cover 30, the protrusions 344 and 364 will snap into the grooves 242a and 242b. The engagement of the blade assembly 20 and the protective blade cover 30 is shown in FIGS. 3 and 4. 
     Preferably, the side walls 32a and 32b contain interlocking connectors on them. In a preferred embodiment, the side wall 32a contains an elongated projection 322 that is shaped like a &#34;T&#34; in cross-section. The side wall 32b contains elongated projections 324a and 324b. Together, projections 324a and 324b define a slot into which projection 322 may slide. As shown in FIG. 5, these projections permit any number of protective blade covers to be interconnected together. 
     Alternatively, as shown in FIG. 13, a plurality of protective blade covers 30 may be integrally formed in a side-by-side relationship to form an integral five-piece dispenser for blade assemblies. 
     In use, the blade assemblies are preferably sold by the manufacturer pre-stored in protective blade covers. To load a pre-stored blade assembly 20 into a handle assembly 10, a user first moves the tab 16 of the handle to its forward-most position. (The guide 14 will correspondingly be moved to its forward-most position as well.) The user then inserts the endpiece 24 of the blade assembly into the blade opening 122 until the downwardly pointing hook 244 of the endpiece makes contact with the upwardly pointing hook 148 of the guide. Applying forward pressure to the tab 16, the user continues to push the blade assembly into the opening 122. Since the hook 148 is mounted on the resiliently yieldable upper portion 146 of the guide, the hook 148 and the upper portion 146 will be depressed downward by the camming action of the downwardly pointing hook 244. When the blade assembly is inserted far enough into the opening 122, the upwardly pointing hook 148 will spring back up and under the downwardly pointing hook 244, thereby engaging the endpiece. For improved stability of operation of the utility knife, the horizontally projecting member 144 of the lower guide portion 146 is designed to fit into the recessed area 248 of the endpiece. 
     To remove the protective blade cover 30 after the endpiece 24 and the guide 14 have been engaged, the user simply moves the tab 16 backward (away from the opening 122). Since the outer dimensions of the protective blade cover 30 are larger than the opening 122, the user will reach a position where the protective blade 30 cover abuts the end of the handle. At that point, further backward movement of the tab 16 will force the protrusions 344 and 364 to disengage from the grooves 242a and 242b, respectively. 
     To change a blade, the user simply moves the tab 16 to its forward-most position, allowing the blade to protrude from the handle. The user than inserts a protective blade cover 30 over the blade until the protrusions 342 and 362 engage the grooves 242a and 242b of the endpiece. The user then presses the blade release button 18 to depress, via the post 149, the resiliently yieldable upper portion 146 of the guide, thereby unhooking the two hooks 148 and 244. The blade assembly 20, in its protective blade cover 30, is then removed from the handle. 
     As can be readily seen, the present invention allows a simple and quick exchange of blades without opening up the handle. Moreover, as a result of the cooperation between the protective blade cover 30, the blade assembly 20, and the handle 10, the cutting edges of the blades are covered at all times during the change of the blades. Thus, the present invention provides safety to the user during the exchange of blades. 
     Although the present invention has been described with reference to a certain preferred embodiment, various modifications, alterations, and substitutions will be known or obvious to those skilled in the art without departing from the spirit and scope of the invention, as defined by the appended claims.