Mechanism for sharpening a writing instrument

Information

  • Patent Grant
  • 6397480
  • Patent Number
    6,397,480
  • Date Filed
    Thursday, July 6, 2000
    24 years ago
  • Date Issued
    Tuesday, June 4, 2002
    22 years ago
Abstract
A pencil sharpener (10) is disclosed as including a body (12) with a hole (22) for receiving an end of a pencil, a cutting blade (24) secured to the body (12) for sharpening the pencil, and a stopper (30) movable relative to the body (12) to vary the length of the end of the pencil which may be received into the hole (22).
Description




BACKGROUND OF THE INVENTION




This invention relates to a mechanism for sharpening a writing instrument, e.g. pencil, and in particular such a sharpening mechanism in which the length of the sharpened end of the writing instrument which may be inserted into the sharpening mechanism may be adjusted.




Pencil sharpeners have been made available for a very long period of time. While various modifications have been made to the outward appearance of such sharpeners to make them more aesthetically attractive, relatively few improvements have been made to the basic structure. Conventional pencil sharpeners include a generally conical insertion hole tapering from a broad outer entrance to a sharp inner end. This hole allows an end of a pencil to be inserted into the sharper, such that the pencil will be sharpened by a cutting blade secured to the sharpener when the pencil is rotated relative to, and moves into, the sharpener.




In one type of conventional pencil sharpeners, the inner end of the hole is not closed, such that the pencil may be caused to go on rotating relative to and moving into the insertion hole. The disadvantage of such an arrangement is that more than the necessary pencil may be cut away, or the user may not wish the pencil to be so sharp.




As an improvement, some pencil sharpeners are provided with a stopper at the inner end of the insertion hole so as to limit the inward movement of the pencil relative to the sharpener. By way of such an arrangement, once the pencil has proceeded to abut the stopper, further rotation thereof will not bring about any further inward movement of the pencil, so that no further pencil will be cut away. A disadvantage associated with such an arrangement is that the pencil sharpener cannot sharpen the pencil to a degree of sharpness which is up to the requirement of the user.




As yet a further improvement, some conventional sharpeners provide two insertion holes, each with a cutting blade, yet one without a stopper and one with a stopper. Not only does such an arrangement increase the cost of production, this type of pencil sharpeners also suffers from the shortcoming that basically only two degrees of sharpness are allowed.




It is thus an object of the present invention to provide an improved mechanism for sharpening an writing instrument in which the above shortcomings are mitigated, or at least to provide a useful alternative to the public.




SUMMARY OF THE INVENTION




According to the present invention, there is provided a mechanism for sharpening a writing instrument, which mechanism including a body member with a hole adapted to receive an end of said writing instrument, a cutting blade secured to said mechanism and adapted to sharpen said writing instrument, wherein said mechanism further includes a stopper movable relative to said body member to vary the length of said end of said writing instrument receivable into said hole.











BRIEF DESCRIPTION OF THE DRAWINGS




An embodiment of the present invention will now be described, by way of an example, and with reference to the accompanying drawings, in which:





FIG. 1

is a perspective view of a pencil sharpener according to the present invention;





FIG. 2

is an exploded view of the pencil sharpener shown in

FIG. 1

;





FIG. 3

is a front view of the pencil sharpener shown in

FIG. 1

;





FIG. 4

is a top view of the pencil sharpener shown in

FIG. 1

;





FIG. 5

is a bottom view of the pencil sharpener shown in

FIG. 4

;





FIG. 6

is a left side view of the pencil sharpener shown in

FIG. 4

;





FIG. 7

is a right side view of the pencil sharpener shown in

FIG. 4

;





FIG. 8

is a rear view of the pencil sharpener shown in

FIG. 4

;





FIG. 9

is a cross-sectional view of the pencil sharpener taken along the line A—A in

FIG. 3

;





FIG. 10

is a cross-sectional view of the pencil sharpener taken along the line B—B in

FIG. 4

; and





FIG. 11

is a cross-sectional view of the pencil sharpener taken along the line C—C in FIG.


3


.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT





FIGS. 1 and 2

show a pencil sharpener according to the present invention, generally designated as


10


. The pencil sharpener


10


includes a body


12


which is secured to an end cap


14


by two screws


16


. The body


12


includes a front circular plate


18


with a circular entrance


20


, which leads into a conical hole


22


, which may be seen more clearly in FIG.


9


. As in conventional pencil sharpeners, a cutting blade


24


is secured by a screw


26


to the body


12


, so that when an end of a pencil is inserted into the hole


22


, rotation and moving in of the pencil relative to the body


12


will cause the pencil to be cut and sharpened by the blade


24


.




As can be seen clearly in particular in

FIG. 2

, the pencil sharpener


10


includes a knob


28


associated with a stopper


30


. A lower end


32


of the knob


28


is received with a cavity


34


of the end cap


14


, and a ring


36


sits on the end cap


14


, so that the knob


28


may rotate relative to the end cap


14


. The inner surface


38


of the ring


36


is threaded. In addition, the knob


28


includes a spindle


40


whose outer surface is threaded. The stopper


30


includes a stopping surface


42


. The lower part of the stopper


30


is provided with internal threads


44


and external threads


46


. The lower part of stopper


30


is received within a cavity


48


between the spindle


40


of the knob


28


, and the inner surface


38


of the ring


36


of the knob


28


, in such a way that the internal threads


44


of the stopper


30


mesh with the spindle


40


, and the external threads


46


mesh with the threads on the inner surface


38


of the ring


36


. It should be understood that although there are the two threaded engagements between the knob


28


and the stopping member


30


, i.e. the engagement between the spindle


40


and the internal threads


44


of the stopper


30


on the one hand, and the engagement between the external threads


46


of the stopper


30


and the threads in the inner surface


38


of the ring


36


on the other hand, one such engagement will suffice for the purpose of the present invention.




The upper part of the stopper


30


is in the form of a generally rectangular prism, and is received within a channel


50


formed by a guiding member


52


, which guides the movement of the stopper


30


relative to the body


12


. By way of such an arrangement, rotation of the knob


28


will cause the stopper


30


to translationally move relative to the body


12


between a first position (as indicated by P


a


in

FIG. 9

) in which the stopping surface


42


is at or lower than (in the sense of

FIG. 9

) the sharp end of the hole


22


, and a second position (as indicated by P


b


in

FIG. 9

) which is above (again in the sense of

FIG. 9

) the end of the hole


22


. When the stopping surface


42


is in position P


a


, the pencil sharpener


10


will function as one with no stopper. When the stopper


30


is moved by the knob


28


such that the stopping surface


42


is at P


b


, the end of the pencil inserted into the hole


22


will abut the stopping surface


42


, so as to limit the length of the end of the pencil which can be inserted into the hole


22


. Such an arrangement may thus vary the length of the end of a pencil which can be inserted into the hole


22


. A further feature of the present invention is that the stopping surface


42


may be positioned anywhere between P


a


and P


b


, so that the degree of sharpness of the sharpened pencil may be selected by the user.



Claims
  • 1. A mechanism for sharpening a writing instrument comprising a body member with a hole adapted to receive an end of said writing instrument, a cutting blade secured to said mechanism and adapted to sharpen said writing instrument, and a knob member and a stopper threadedly engaged with each other, wherein said knob member is movable only rotationally relative to said body member about a longitudinal axis of said body member, and wherein rotation of said knob member causes said stopper to slidingly move along an axis which is substantially parallel to said longitudinal axis of said body member to vary the length of the end of a writing instrument receivable into said hole.
  • 2. A mechanism according to claim 1 wherein said knob member and said stopper are movable relative to each other.
  • 3. A mechanism according to claim 1 wherein said stopper includes an end with an outer threaded portion which is engaged with a threaded portion in at least part of an inner surface of said knob member.
  • 4. A mechanism according to claim 1 wherein said stopper includes an end with an inner threaded portion which is engaged with a threaded portion in at least part of a spindle member of said knob member.
  • 5. A mechanism according to claim 1 wherein said stopper includes a substantially rectangular prismatic end translationally movable relative to a guiding member.
  • 6. A pencil sharpener including a mechanism according to claim 1.
US Referenced Citations (3)
Number Name Date Kind
4506716 Hayashi Mar 1985 A
4620370 Zownir et al. Nov 1986 A
4755074 Roberts Jul 1988 A