Abstract:
A double-ended dual mechanism retractable blade utility knife. The knife includes two separately actuable mechanisms which allow extension and retraction of one or both blades independently of one another. The cutting surfaces of the respective blades are oriented towards opposite sides of the knife, thereby facilitating rotation of the knife within the user&#39;s hand in order to change which blade is currently being used. The independent nature of the dual mechanisms allows both of the blades to be held in the extended position. A storage area is further provided behind each of the mechanisms for the storage of spare blades.

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention generally relates to utility knives and, more particularly, to a double-ended dual-mechanism retractable blade utility knife. 
     BACKGROUND OF THE INVENTION 
     Utility knives which incorporate a retractable, replaceable razor blade have been popular in many applications for years. There are deficiencies, however, in the prior art designs which limit their usefulness in certain applications. For example, in the roofing trade it is generally necessary for the roofer to carry two such utility knives. One knife is equipped with a straight razor blade for cutting felt paper and the like, while the other knife is equipped with a hooked blade for cutting shingles and the like which have a granulated surface. Neither of these knives are well adapted for cutting the other type of material, therefore it is necessary for the roofer to carry both types of knives. 
     Carrying two knives, however, is inconvenient, especially when working on a roof. Whenever it is necessary to switch knives, the user must retract the first blade and stow the first knife, take out the second knife and extend the second blade. This is extremely inconvenient during applications where use of both knives in alternating succession is routinely required. 
     There have been attempts in the prior art to solve this problem. For example, U.S. Pat. No. 5,093,994 to Karas discloses a double-ended utility knife. This knife, however, still exhibits most of the problems encountered with using two separate knives. To switch blades, the knife must be turned around, the first blade must be retracted and the second blade must be extended. Turning the knife around is generally a two-handed operation. 
     There is therefore a need in the prior art for a utility knife that allows use of two different blades without requiring the cumbersome manipulations required by prior art knives during blade changes. The present invention is directed toward meeting this need. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a double-ended dual-mechanism retractable blade utility knife. The knife includes two separately actuable mechanisms which allow extension and retraction of one or both blades independently of one another. The cutting surfaces of the respective blades are oriented towards opposite sides of the knife, thereby facilitating rotation of the knife within the user&#39;s hand in order to change which blade is currently being used. The independent nature of the dual mechanisms allows both of the blades to be held in the extended position. A storage area is further provided behind each of the mechanisms for the storage of spare blades. 
     In one form of the invention, a double-ended dual-mechanism retractable blade utility knife is disclosed, comprising a housing; a first blade carrier operative to carry a first blade and to slide along a longitudinal axis of the housing; and a second blade carrier operative to carry a second blade and to slide along the longitudinal axis of the housing; wherein the first and second blade carriers may be slid along the longitudinal axis of the housing independently of one another. 
     In another form of the invention, a double-sided dual-mechanism retractable blade utility knife is disclosed, comprising a housing; a first blade carrier operative to carry a first blade and to slide along a longitudinal axis of the housing; a first space formed in the housing adjacent the first blade carrier, the first space sized to allow storage of first spare blades; a second blade carrier operative to carry a second blade and to slide along the longitudinal axis of the housing; and a second space formed in the housing adjacent the second blade carrier, the second space sized to allow storage of second spare blades; wherein the first and second blade carriers may be slid along the longitudinal axis of the housing independently of one another; and wherein a first cutting surface of the first blade is positioned on a first side of the longitudinal axis; and wherein a second cutting surface of the second blade is positioned on a second side of the longitudinal axis. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of an exterior of the utility knife of the present invention. 
     FIG. 2A is a side elevational view of an interior of one half of the knife of FIG. 1. 
     FIG. 2B is a side elevational view of an interior of a second half of the knife of FIG. 1, illustrating the actuation mechanisms. 
     FIG. 3 is a side elevational view of a blade carrier of the present invention. 
     FIG. 4 is a side elevational view of the blade carrier of FIG. 3 with a straight razor blade mounted thereon. 
     FIG. 5 is a cross-sectional view of the utility knife of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. 
     Referring now to FIG. 1, there is illustrated a first embodiment of the present invention, indicated generally at 10. 
     The two ends of the utility knife 10 are identical, with one end being inverted about the longitudinal knife axis with respect to the other end. Therefore, identical reference numbers are used herein to denote identical parts, with the suffix &#34;a&#34; or &#34;b&#34; added to denote on which end of the knife 10 the part is located. 
     With reference to FIGS. 2A-B, the utility knife 10 includes two mating housing halves 12 and 14 which are held together by a transverse threaded fastener 16 which passes through the hole 18 and threadably engages the hole 20 which is formed as a portion of the housing half 14. The two housing halves 12, 14 form a first open channel 22a in which is located a first actuating lever 24a. Movement of the first actuating lever 24a to the left in FIG. 2B causes a first blade (illustrated in phantom at 28) to be extended from a slot formed in the first end 26 of the utility knife 10. The first blade 28 includes a first cutting surface 30 facing downward in FIG. 2b. Conversely, movement of the first actuating lever 24a to the right in FIG. 2B causes the first blade 28 to be retracted completely within the housing 10. Similarly, a second open channel 22b is formed by the mating housing halves 12, 14 transversely and longitudinally opposite from the open channel 22a. A second actuating lever 24b is disposed within the second open channel 22b and is operative to extend a second blade (illustrated in phantom at 34) from an open slot in a second end 36 of the utility knife 10 when the second actuating lever 24b is moved to the right in FIG. 2B. The second blade 34 includes a second cutting surface 31 facing upward in FIG. 2b. Movement of the second actuating lever 24b to the left in FIG. 2B operates to retract the second blade 34 completely within the utility knife 10. 
     Each of the actuating levers 24a and 24b is attached to respective first and second blade carriers 38a and 38b, as illustrated in FIG. 28. Because the configuration of first blade carrier 38a is identical to the configuration of second blade carrier 38b, such configuration is illustrated in FIGS. 3 and 4 without the use of &#34;a&#34; and &#34;b&#34; suffixes. For example, reference to blade carrier 38 in FIGS. 3 and 4 should be understood to apply to both first blade carrier 38a and second blade carrier 38b. An analogous numbering scheme is used to refer to the elements in FIG. 5 that are common to both the first and second sides of the knife 10. Referring now to FIGS. 3 and 4, the blade carrier 38 is preferably formed from metal and includes raised transverse surfaces 40, 42 and 44 which operate to limit movement in three directions of a blade 28 mounted thereon (see FIG. 4). Movement of the blade 28 is further prevented by a tab 46 which fits into a notch 48 formed into the blade 28. The blade 28 has two such notches 48 which allow for reversing of the blade 28 within the blade carrier 38 for extended blade life. The blade 28 is of the type standardly used in this art. 
     Referring once again to FIGS. 2A-B, the first blade carrier 38a is maintained in a retracted position by engagement of a first tab formed on the first end 50a of the first blade carrier 38a with a first indentation 52a formed in the housing halves 12, 14. Similarly, the first blade carrier 38a is maintained in an extended position by interaction between the first tab formed on the first end 50a and a second indentation 54a notch 54 formed in the housing halves 12, 14. The first tab formed on the first end 50a of the first blade carrier 38a is moved from first indentation 52a to second indentation 54a (and vice versa) by depressing the first actuating lever 24a, which causes the first arm 51a to flex, thereby disengaging the first tab formed on the first end 50a from the first and second indentations 52a, 54a. Engagement of the first tab formed on the first end 50a with the first and second indentations 52a and 54a therefore operates to securely maintain the first blade carrier 38a (and hence the first blade 28) in either the retracted or extended position. 
     The second blade carrier 38b is maintained in a retracted position by engagement of a second tab formed on the second end 50b of the second blade carrier 38b with a third indentation 52b formed in the housing halves 12, 14. Similarly, the second blade carrier 38b is maintained in an extended position by interaction between the second tab formed on the second end 50b and a fourth indentation 54b formed in the housing halves 12, 14. The second tab formed on the second end 50b of the second blade carrier 38b is moved from third indentation 52b to fourth indentation 54b (and vice versa) by depressing the second actuating lever 24b, which causes the arm second 51b to flex, thereby disengaging the second tab formed on the second end 50b from the third and fourth indentations 52b, 54b. Engagement of the second tab formed on the second end 50b with the third and fourth indentations 52b and 54b therefore operates to securely maintain the second blade carrier 38b (and hence the second blade 34) in either the retracted or extended position. 
     Referring now to the cross-sectional view of FIG. 5, it will be appreciated that when the housing halves 12, 14 are coupled together, the blade carrier 38 is maintained within a longitudinal sliding track formed by protrusions 56, 58, 60 and 62 formed integrally with the housing half 12 and by protrusions 64, 66, 68 and 70 formed in the housing half 14. These protrusions from the housing halves 12, 14 form top and bottom C-channel tracks in which the blade carrier 38 runs. It will be appreciated by those skilled in the art that the exact configuration of such tracks is not critical to the present invention, merely that some means for limiting the motion of the blade carrier 38 be provided within the housing halves 12, 14. 
     As best illustrated in FIG. 5, an indentation 72 is formed in the housing half 14 behind the blade carrier 38 in order to provide a space for storage of spare blades 29. The spare blades 29 may be first blades 28 and/or second blades 34, both of which will fit in this storage space. The spare blades 29 are stored in an inverted position as compared to the blade in the blade carrier 38. 
     It will be appreciated by those skilled in the art that the utility knife 10 of the present invention exhibits several advantages over prior art utility knives. First, the utility knife 10 allows independent extension and retraction of two blades. This is a particularly desirable feature when two different blades, such as a straight blade and a hooked blade, need to be used repeatedly during the same project. A further advantage of the dual-mechanism of the utility knife 10 is that it allows the cutting surfaces 30, 31 of the two blades 28,34 to be oriented in opposite directions. Such an orientation of the cutting surfaces 30, 31 facilitates single-handed reorientation of the utility knife 10 in the user&#39;s hand in order to position the other blade for use. Such reorientation simply involves rotating the knife in the user&#39;s hand about an axis extending through the fastener 16. Such a flipping motion is easily accomplished with one hand. When both blades 28, 34 are left in the extended position, the user may easily switch between blades 28,34 by simply rotating the utility knife 10 with a single hand. 
     By comparison, the prior art double-ended utility knives required that one blade be retracted and the other blade be extended whenever the user desired to switch to the other blade. Furthermore, the cutting surfaces on the prior art double-ended utility knives face in the same direction, thereby making it extremely difficult to reorient the knife for use with the other end without employing both of the user&#39;s hands. Another useful feature of the utility knife 10 of the present invention is the provision of a somewhat wider handle than is customary in such knives, with the inclusion of the cavity 72 behind each blade carrying mechanism which allows for the storage of spare blades 29 on both sides of the knife 10. Not only does this increase the number of spare blades 29 which may be carried in the knife 10, it also facilitates carrying spare blades 29 for both types of blades (e.g. a straight blade 28 and a hooked blade 34). 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.