US3777791A

US3777791A - Electric pencil sharpener

Info

Publication number: US3777791A
Application number: US00255274A
Authority: US
Inventors: H Uchida
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 1971-05-26
Filing date: 1972-05-22
Publication date: 1973-12-11
Anticipated expiration: 1990-12-11
Also published as: CA976049A; GB1351427A; FR2139180A1; AU4277572A; NL7207198A; NL158440B; FR2139180B1; DE2225069A1; SE396319B; DE2225069B2

Abstract

An electric pencil sharpener comprising a rotatable cutter holding block and a cutter element capable of undergoing a relative rotation with respect to the cutter holding block for shaving an end portion of a pencil inserted in the sharpener, the cutter element being adapted to separate away from its engagement with the end portion of the pencil, when the pencil end portion has been shaved to a predetermined degree of sharpness, so as to ensure the prevention of an excessive, unnecessary shaving of the pencil end portion beyond the predetermined degree of sharpness.

Description

United States Patent 1 1 Uchida Dec. 11, 1973 [5 1 ELECTRIC PENCIL SHARPENER 2,572,875 10/1951 Markvart et al 144 2871 [75] Inventor: Hajime Uchida, Fukuoka, Japan 73 Assigneez Matsushita Electric Industrial Co 3,134,365 5/1964 Hori. .1 l44/28.7 X Ltd Osaka, Japan 3,678,975 7 1972 lman1sh1 et al. 144/2872 x [22] Filed: May 22, 1972 Primary ExammerAndrew R. Juhasz l l PP N05 255,274 Assistant ExaminerJames F. Coan Attorney-E. F. Wenderoth et al.

[30] Foreign Application Priority Data May 26, 1971 Japan 46/36525 Oct 15, 1971 Japan ..46/81991 [57] ABSTRACT 197] 46/89345 An electric pencil sharpener comprising a rotatable Japan 46/97673 cutter holding block and a cutter element capable of Feb. 28, Japan undergoing a relative rotation respect to the cut ter holding block for shaving an end portion of a penfi 8 cil inserted in the sharpener, the cutter element being 72 28 3 adapted to separate away from its engagement with l r g 'gi'gg'i 71 the end portion of the pencil, when the pencil end portion has been shaved to a predetermined degree of sharpness, so as to ensure the prevention of an excessive, unnecessary shaving of the pencil end portion be- [56] References cued yond the predetermined degree of sharpness.

UNITED STATES PATENTS 1,532,l67 4/1925 Weiler l44/28.7l 18 Claims, 18 Drawing Figures PATENTEU DEC! 1 I975 777, 7 9 l SHEET 8 [1F 6 FIG. /7

ELECTRIC PENCIL SHARPENER The present invention relates to an electric pencil sharpener and, more particularly, to an electric pencil sharpener capable of preventing a pencil from being excessively or unnecessarily shaved.

An electric pencil sharpener heretofore largely utilized generally comprises rotary means rotatable in one direction by a motor and cutter means operatively carried by said rotary means so as to rotate in the direction opposite to the rotational direction of said rotary means whereby an end portion of the pencil inserted in the pencil sharpener can be sharpened in engagement with said cutter means during the rotation of said rotary means.

In this arrangement, the user of the electric pencil sharpener oftentimes feel inconvenience in that means indicative of completion of the sharpening operation by the pencil sharpener is not available to the user and, therefore, the pencil is oftentimes excessively or unnecessarily shaved.

To eliminate this inconvenience, there has been recently proposed an electric pencil sharpener wherein a signalling device, in the form of an indicating lamp or a buzzer, for indicating the completion of the sharpen ing operation is provided. However, in view of the fact that a cutter for shaving the pencil end portion is rotated at a high speed, the pencil end portion has a tendency to be excessively or unnecessarily shaved during a particular period beginning from the operation of the signalling device and ending at the moment said pencil is withdrawn from the pencil sharpener. Accordingly, with this pencil sharpener provided with the signalling device, the user is compelled to concentrate his attention on the commencement of operation of the signalling device, or otherwise the pencil inserted in the pencil sharpener will be excessively or unnecessarily shaved.

Accordingly, an essential object of the present invention is to provide an improved electric pencil sharpener capable of ensuring the prevention of an excessive, unnecessary shaving of a pencil inserted in the pencil sharpener by which the disadvantage inherent in the conventional electric pencil sharpener can be substantially eliminated.

Another object of the present invention is to provide an improved electric pencil sharpener wherein means is provided for disengaging a cutter from an end portion of the pencil inserted in the pencil sharpener when said pencil end portion is sharpened to a predetermined degree of sharpness, whereby the prevention of an excessive, unnecessary shaving of the pencil end portion is advantageously ensured.

A further object of the present invention is to provide an improved electric pencil sharpener of the type above referred to wherein means is provided for indicating to the user a completion of a pencil sharpening operation.

A still further object of the present invention is to provide an improved electric pencil sharpener of the type above referred to wherein means for adjusting the timing at which the cutter is separated from its shaving engagement with the pencil end portion is provided for enabling the user of the pencil sharpener to adjust the finished degree of sharpness of the pencil end portion as desired.

A still further object of the present invention is to provide an improved electric pencil sharpener of the type above referred to wherein the means for adjusting the timing at which the cutter is separated from its shaving engagement with the pencil end portion and means for indicating to the user the completion of the pencil sharpening operation are both provided not only for enabling the user to adjust the degree of sharpness of the pencil end portion but also for indicating the completion of the sharpening operation to the user.

A still further object of the present invention is to provide an improved electric pencil sharpener of the type above referred to which can be manufactured with minimum parts and without requiring complicated manufacturing steps for achieving any one of the above various objects of the present invention.

According to an essential embodiment of the present invention, the electric pencil sharpener in principle comprises a switch and a motor, said switch adapted to close upon insertion of a pencil into the electric pencil sharpener for energizing said motor and open upon withdrawal of said pencil therefrom for deenergizing said motor, rotary means rotatable in one direction by said motor when said switch is closed, cutter means operatively carried by said rotary means so as to rotate in the direction opposite to the rotational direction of said rotary means whereby an end portion of said pencil inserted can be sharpened in engagement with said cutter means during the rotation of said rotary means, and means for separating said cutter means from said engagement between-said cutter means and said pencil end portion when said pencil end portion has been sharpened to a predetermined sharpness to ensure the prevention of an excessive, unnecessary shaving of the pencil beyond the predetermined sharpness, said cutter means being returned to an initial position, in which a fresh pencil is ready to be sharpened by the pencil sharpener, from the disengaged position when an external pushing force that has been applied to the opposite end portion of said pencil is removed.

The electric pencil sharpener of the principal construction as hereinbefore described has an essential advantage in that an excessive, unnecessary shaving of the pencil which is inherent in the conventional sharpener of this kind irrespective of the provision of the signalling device can be substantially eliminated with simplitied mechanisms. Accordingly, it is clear that no pencil is substantially wasted thereby permitting the pencil to be economically used in writing, drawing or for other purposes.

The present invention will be hereinafter fully described in conjunction with various preferred embodiments thereof with reference to the accompanying drawings, in which;

FIG. 1 is a partially sectional side view of an electric pencil sharpener in one embodiment of the present invention,

FIG. 2 is a sectional side view, on an enlarged scale, of an essential portion of the sharpener of FIG. 1, showing a cutter means in one position,

FIG. 3 is a similar view to FIG. 2, showing the cutter means in a second position,

FIG. 4 to FIG. 7 are each similar views to FIG. 2, showing second to fifth embodiments of the present invention, respectively,

FIG. 8 is a schematic perspective view, on a further enlarged scale, of a portion of FIG. 7, showing a manner in which an operating lever is operatively connected with a cutter element carrying spindle,

FIG. 9 is a similar view to FIG. 2, showing a sixth embodiment of the present invention in which means for adjusting the sharpness of the pencil end portion is provided,

FIG. 10 to FIG. 12 are each partially sectional side views of an electric pencil sharpener in seventh to ninth embodiments of the present invention, respectively,

FIG. 13 is a schematic electric wiring diagram showing a manner in which a switch operable by the pencil, a signaling device and a motor are connected with respect to one another,

FIG. I4 is a partially sectional side view of an electric pencil sharpener in a tenth embodiment of the present invention,

FIG. 15 is a schematic top plan view of an essential portion of the pencil sharpener of FIG. 14,

FIG. 16 is a partially sectional side view of an electric pencil sharpener in an eleventh embodiment of the present invention,

FIG. 17 is a schematic top plan view, on an enlarged scale, of a portion of FIG. 16 showing a manner in which a switch is supported, and

FIG. 18 is a schematic perspective diagram showing a bearing structure which may be employed in the present invention for connecting the cutter element carrying spindle to a cutter holding block and for accommodating a slidable strip member and an operating lever.

Before the description of the present invention proceeds, it is to be noted that like parts are for the sake of brevity, designated by like reference numerals throughout the several views of the accompanying drawings.

A basic construction and operation of an electric pencil sharpener to which the present invention can be applicable will be first described with reference to FIG. I.

An electric pencil sharpener so far shown in FIG. 1 comprises a housing 1 consisting of a base 2 of substan-v tially rectangular box-like shape having a pair of lateral side portions (not indicated), a rear portion 2a and a bottom portion 2b, and a covering 3 of substantially rectangular cap-like shape having a pair of lateral side portions (not indicated), a front portion 3a, a rear portion 3b opposed to said front portion 3a and a top portion 30, said base 2 and said covering 3 being secured to each other in any known manner such as by the use ofa plurality of screws. An opening of the housing 1 defined by the front portion 3a of the covering 3, the pair of lateral side portions of the base 2 and the bottom portion 2b of the base 2 is adapted to receive therein a scrap box 4 into which scraps of a pencil to be sharpened are collected during a pencil sharpening operation.

The covering 3 has in its front portion 3a a hole 3a through which a suitable socket member 5 extends in a non-detachable manner. The socket member 5 has formed therein a pencil guiding bore 5a extending in the lengthwise direction thereof and has one end situated outside the housing 1 and is finished in any desired fashion for a decorative purpose and the other end situated within the housing 1 has rigidly mounted thereon a ring-shaped switch structure 6 having a circular opening 6a in alignment with said guiding bore 50: of the socket member 5. This ring-shaped switch structure 6 may be of any known construction and designed such that a switching circuit (not shown) associated with a motor M is closed to energize the motor M as a pencil to be sharpened is passed through said circular opening 6a and opened to deenergize the motor M as the pencil is withdrawn therefrom. The switch structure 6 also has an annular bearing portion 6b, the function of which will be mentioned later.

Disposed within the housing 1 and situated above the scrap box 4 is a cutter holder assembly generally comprising a cutter holding block 7 and a bearing block 8. The cutter holding block 7 has a front portion having a tapered guide hole 7a tapering toward a substantially intermediate portion of said block 7, an open end of said guide hole 7a being surrounded by an annular flange 7b integral with said front portion of said holding block 7. The annular flange 7b of the holding block 7 is rotatably engaged in the annular bearing portion 65 of the socket member 6 with the longitudinal axis of said guide hole 7a aligned with that of said circular opening 6a of said ring-shaped switch structure 6.

The cutter holding block 7 has at its rear portion a shaft 7c having one end integral with said block 7 and thelother free end being rotatably supported in a manner as will be described later. This cutter holding block 7 also has a substantially cornered opening 7d in which some parts of a mechanism for preventing an excessive shaving of a pencil to be sharpened are operatively accommodated as will be described later.

The bearing block 8 for operatively supporting the cutter holding block 7 is rigidly supported by a mounting-framework 9 of substantially L-shaped cross section having an upright panel 9a carrying said bearing block 8 in position and a base panel9d rigidly mounted on the bottom portion 2d of the base 2 in any suitable manner such as by means of spot-welding or by the use of set screws. This bearing block 8 has a bore 8a through which the shaft of the holding block 7 is rotatably extended with the free end of said shaft 7c having rigidly mounted thereon a gear wheel 10. The gear wheel 10 is in mesh with a drive gear 12 mounted on an output shaft 13 of the motor M, suitably supported in position by means of the mounting framework 9, so that the rotational force which is produced by the motor M can be transmitted to the cutter holding block 7 through the drive gear 12 in mesh with the gear wheel 10, causing the cutter holding block 7 to rotate about the longitudinal axis of said block.

The bearing block 8 carries a fixed ring gear 14 rigidly secured thereto as at 8b and encircling the rear portion of the cutter holding block 7 with the plane of said fixed ring gear 14 intersecting the longitudinal axis of said holding block 7. This fixed ring gear 14 has the gear teeth on the inner peripheral surface thereof.

A cutter'element 15 of any known construction and of cylindrical shape is rotatably mounted on a spindle 16 having a front end portion rotatably supported in a bearing hole 72 in a bearing lug 7f integral with the front portion of the holding block 7 and the other end preferably tapered and rotatably supported in a bearing hole 7g in a bearing lug 7h integral with the rear portion of the holding block 7. The cutter element carrying spindle 16 is also has rotatably mounted thereon a pinion gear 17 rigidly connected with a rear end of said cutter element 15. This pinion gear 17 is constantly engaged with the gear teeth of the fixed ring gear 14 whereby, during the continuous rotation of the cutter holding block 7 about its own longitudinal axis which is effected by the motor M, the pinion gear 17 rolls around the inside of the fixed ring gear 14 assuming a planetary motion while said pinion gear 17 and, hence, the cutter element rotates about the axis of the spindle 16.

The cutter element 15 has a substantial peripheral surface in parallel relation to the tapering of the guide hole 7a of the holding block 7 so that the end portion of a pencil to be sharpened, which is exposed to the cutter element 15 through a slit (not visible) formed in a surrounding surface of the tapered guide hole 7a, can

t be shaved by the cutter element 16 during the rotation of the cutter holding block 7 and the simultaneous planetary motion of the cutter element 15 rotating about the axis of the spindle '16.

in the electric pencil sharpener of the construction so far described above, when a pencil to be sharpened is inserted into a pencil passage consisting of the bore 5a of the socket member 5, the circular opening 6a of the ring-shaped switch structure 6 and the tapered guide hole 7a of the front portion of the cutter holding block 7, the switching circuit of the switch structure 6 is closed thereby causing the motor M to rotate in one direction. As the motor M is rotated in the manner as hereinabove described, the rotational force is then transmitted to the cutter holding block 7 through the engagement between the drive gear 12 and the gear wheel 10, causing the holding block 7 to rotate about its own longitudinal axis. This rotation of the holding block 7 is accompanied by the planetary motion of the cutter element 15 while the latter is rotated about the longitudinal axis of the spindle 16 by the engagement between the pinion gear 17 integral with the element 16 and the gear teeth of the fixed ring gear 14.

At the same time the cutter element 15 rotates in the planetary motion, the end portion of the pencil thus inserted can be rapidly shaved by said rotating cutter element 15 to sharpen that end portion of the pencil.

If the pencil that has been inserted into the passage is subsequently withdrawn from said passage and, more specifically, if the pencil is withdrawn from the circular opening 60 of the switch structure 6, the switching circuit of the switch structure 6 is opened to terminate the supply of electric power from a suitable power source to the motor M so that the rotation of the holding block 7 can be stopped. It is to be noted that pencil shavings produced during the pencil sharpening operation are collected in the scrap box 4 which may be removed from the sharpener proper.

According to a first preferred embodiment of the present invention, as clearly shown in FIGS. 2 and 3, the cornered opening 7d of the cutter holding block 7 defined by four surrounding inner walls, only three of which are shown and indicated by 7i, 7j and 7k, accommodates therein a slidable strip member 18 slidably supported in position by the holding block 7 by means of a suitable retainer 19 secured to the inner wall 7j within the opening 7d of the holding block 7. The slidable strip member 18 has on one end an integral feeler 20 extending substantially at right angles to the slidable strip member 18 and arranged so as to be contacted by the lead point of the end portion of a penother end of said slidable strip member 18 is pivotally connected with an operating lever 22 extending downwardly between the bearing lug 7h and the inner wall 7k and terminating at a position where the terminal end of said operating lever 22 is contactable with the tapered end of the cutter element carrying spindle 16. The inner wall 7k has at a substantially central portion a tapered projection 7m contactable with an intermediate portion of the operating lever 22 and providing a fulcrum for the operating lever about which the latter pivots in response to the movement of the slidable strip member 18.

The cutter element carrying spindle 16 has a reduced diameter portion 16a at a portion adjacent to the front end extremity of said spindle 16. it is to be noted that this reduced diameter portion 16a has a pair of annular surfaces 16b and defining said reduced diameter portion 16a which are inclined outwardly with respect to each other substantially as shown, the length of said reduced diameter portion 161: being slightly greater than the thickness of the front bearing lug 7g of the holding block 7.

A compression spring 23 is positioned outside the front bearing lug 7g and housed within a plug member 24 which may be made of synthetic resin and nondetachably secured to said front bearing lug 7g. This compression spring 23 has an external diameter preferably equal to or not more than the diameter of the spindle 16 and interposed between the bottom of said plug member 24 and the circular surface of the front end extremity of the spindle 16 so that the latter is normally biased toward the operating lever 22. For preventing a possible displacement of this compression spring 23, the bottom of the plug member 24 and the end face of the front end extremity of the spindle 16 may be provided with projecting

pieces

24a and 16d, respectively, each of which is of a diameter substantially equal to the internal diameter of the spring 23 and receives the corresponding end of the spring 23.

With the arrangement as hereinbefore described, prior to the lead point of the end portion of the pencil 21 being sufficiently sharpened, which condition is substantially shown in FIG. 2, the clearance between the slit, formed in the tapered guidehole 7a which opens toward the cutter element 15 and through which that end of the pencil to be shaved to sharpen the lead point thereof is exposed to the cutter element 15, and the substantial peripheral surface of said cutter element 15 in uniformly maintained over the whole length of said slit as shown in FIG. 2.

Shortly before the lead point of the pencil 21 is sufficiently sharpened, this lead point of the pencil 21 commences to contact the feeler 20 of the slidable strip member 18 and, as that end portionof the pencil 21 is further shaved with the application of an external pushing force to the opposite end portion of said pencil, the strip member 18 is rearwardly moved with the feeler 20 in contact with the lead point of the pencil 21, causing the operating lever 22 to pivot about the fulcrum or projection 7m so that the cutter element carrying spindle 16 is frontwardly moved against the compression spring 23.

When the spindle 16 is thus moved such that the reduced diameter portion 16a thereof attains a position where it accommodates therein the thickness of the front bearing lug 7g, at which condition the lead point of the pencil 21 is substantially sufficiently sharpened,

the spindle 16 suddenly pivots about its tapered end in a direction substantially perpendicular to and away from the longitudinal axis of the cutter holding block 7 with the reduced diameter portion 16a thereof accommodating therein the thickness of the front bearing lug 7g, thus establishing the condition substantially as shown in H6. 3. This is possible partly because, during the continuous rotation of the cutter holding block 7 as hereinbefore described, a centrifugal force acts not only on the spindle 16, but also on the cutter element 15, so as to move them away from the longitudinal axis or rotational axis of the cutter holding block 7, and partly because the cutter element receives a substantial amount of load exerted by the pencil end to be shaved so long as the external pushing force is applied to the opposite end of the pencil 21, which said load has a tendency to move the cutter element 15 away from the pencil end being shaved and is substantially proportional to the amount of the external pushing force thus applied.

Once the condition as shown in H6. 3 has been attained, the cutter element 15 commences to run idle while the cutter holding block 7 continues to rotate and, hence, shaving of the pencil end no longer proceeds in view of the fact that an angular clearance between the slit of the pencil guide hole 7a and the peripheral surface of the cutter element 15 is formed in which diverges toward the front bearing lug 7g as clearly shown.

The cutter element carrying spindle 16 thus moved from the original position assumed during a period in which the shaving of the pencil end proceeds can be returned to the original position by the action of the compression spring 23 as the external pushing force, that has been applied to the opposite pencil end, is removed and concurrently the rotational speed of the holding block 7 and hence the motor M is lowered to reduce the value of the centrifugal force acting on the element 15 and the spindle 16. Nevertheless, this is achieved when the pencil 21 that has been inserted into the pencil passage of the pencil sharpener which consists of the bore 50, the annular opening 6a, (both shown in FIG. 1) and the pencil guide hole 7a, is withdrawn therefrom accompanying the opening of the switching circuit of the switch structure 6 thereby to deenergize the motor M.

So far as the first preferred embodiment of the present invention shown in FIGS. l to 3 is concerned, whether or not the lead point of that end portion of the pencil 21. has been sufficiently sharpened can be easily detected by either the sense of touch of an operator holding .the pencil 21 or the sense of hearing of the operator. This is possible because, once the condition shown in FIG. 3 has been established wherein the spindle 16 has been angularly moved as hereinbefore described, no substantial contact between the pencil end portion, which is exposed through the slit of the pencil guide hole 7a of the holding block 7, and the cutter element 15 takes place and a sound of idle rotation of the cutter element 15 is generated which is unusual as compared with that generated during the shaving period.

From the foregoing, it has now become clear that an excessive, unnecessary shaving of a pencil can be advantageously prevented by the provision of a simplified mechanism.

Referring now to F l0. 4 in which a second preferred embodiment of the present invention is shown, the only difference between the first and second embodiments resides in the method of supporting the operating lever 22. As clearly shown, the operation lever 22 in FIG. 4 is pivotally connected at the substantially middle portion with an elongated projection 7m while that end of the slidable strip member 13, which has been described as pivotally connected with the operating lever 22 in the foregoing embodiment, is adapted to abut against the corresponding end of the operating lever 22. This embodiment of FIG. 4 functions in substantially the same manner as the foregoing embodiment without any reduction of the performance.

A third preferred embodiment of the present invention will be hereinafter described with reference to FIG. 5. in this embodiment, a cutter element carrying spindle 25 is employed which is in the form of a headless screw having atone end portion a threaded portion 25a threaded into a threaded blind hole 7n formed in the wall 7k below the tapered projection 7m, and having the other end situated within the bearing hole 72 of the front bearing lug 7f. It is to be noted that the rear bearing lug 7g that has been required in the foregoing embodiments of FlGS. l to 3 and FlG. 4 is omitted in this embodiment. Adjacent to said other end of said spindle 25, the latter has a reduced diameter portion 25a having a pair of outwardly

inclined surfaces

25b and 25c, the shape and function of said reduced diameter portion 25a being the same as those indicated by

parts

16a, 16b and 166 in the foregoing embodiments.

The cutter element 26 is substantially the same as that indicated by 15 in FIGS. 1 to 4, but has the inner peripheral surface spaced from the peripheral surface of the spindle 25 by means of an annular ring member 27, rotatably mounted on said spindle 25, and a sleeve portion 17a of the pinion gear 17. The annular ring member 27 has a width slightly smaller than the length of the reduced diameter portion 25a and has an outer peripheral surface rigidly connected in any suitable manner with the inner peripheral surface of the cutter element 26 at a position close to the front end of the cutter element 26.

The rear end of the cutter element 26 is nonrotatably mounted on the sleeve portion 17a of the pinion gear 17 so that said cutter element 26 can be rotated integrally with said pinion gear 17.

The operating lever 28 shown in FIG. 5 has one end pivotally connected with the slidable strip member in the same fasion as in the first embodiment of FIGS. 1 to 3 and has adjacent to the other end an opening 28a with a diameter slightly greater than the diameter of the spindle 26 so that said spindle 26 loosely extends through said opening 28a of the operating lever 28. A portion of the operating lever 28 surrounding the opening 28a is normally in contact with the pinion gear 17 under the force of a compression spring 29 inserted between the front bearing lug 7f and the adjacent end of the cutter element 26 around the reduced diameter portion 25a of said spindle 26.

By the action of the compression spring 29 urging the cutter element 26 in the direction toward the operating lever 28, the operating lever 28 is normally pivoted about the fulcrum 7m so that the slidable strip member 18 is biased in the direction toward the pencil guide hole 7a. Accordingly, as that end portion of the pencil 21 situated within the pencil guide hole 7a is shaved to sharpen the lead point thereof, the lead point of said pencil 21 contacts the feeler 20 of the slidable strip member 18. So long as an external pushing force is applied to the other opposite end portion of the pencil, the contact between the pencil lead point and the feeler causes the slidable strip member 18 to move in the direction opposite to the pencil guide hole 7a against the compression spring 29. During this movement of the strip member 18, the operating lever 28 is, of course, pivoted about the fulcrum 7m so that the pinion gear 17 and thus the cutter element 26 is moved in the direction opposite to the direction of the force exerted by the compression spring 29, resulting in the annular ring member 27 moves into the reduced diameter portion a when the spring 29 is compressed.

Care must be taken, to facilitate the angular movement of the cutter element, to provide a clearance between the peripheral surface of the spindle 26 and the inner peripheral surface of the pinion gear 17.

It is clear that, for the same reason as hereinbefore described in connection with the first embodiment, the angular clearance is formed between the slit of the pencil guide hole 7a and the peripheral surface of the cutter element 26 upon movement of the annular ring member 27 into the reduced diameter portion 25a whereby no excessive shaving of the pencil end portion after it has been sufficiently sharpened takes place. it is to be noted that, unless otherwise the external pushing force is applied to the opposite end portion of the pencil or the pencil end portion to be shaved is situated within the pencil guide hole 7a, the cutter element 26 is returned by the compression spring 29 to or assumes the original position, substantially as shown in FIG. 5, respectively. When the cutter element 26 is in the angular position condition, it runs idle in the same man ner as in the first embodiment or the second embodiment.

However, care must also be taken in that the axial length of the toothed portion of the pinion gear 17 is preferably greater than the axial length of the fixed ring gear 14 (FIG. 1) so that, even when the cutter element 26 is moved toward the front bearing lug 7f, the pinion gear 17 and the fixed ring gear 14 are not disengaged. In a fourth embodiment of the present invention shown in FIG. 6, a cutter element carrying spindle 30 is slidably supported by the front bearing lug 7f and a blind hole 31 of a diameter slightly greater than the diameter of the spindle 30. This spindle 30 is normally urged in the direction toward the front bearing lug 7f by the action of a compression spring interposed between the end face of that end portion of said spindle 30, slidably accommodated within the blind hole 31 formed in the block 7 as shown, and the bottom of the blind hole 31. The spindle has at the other end portion a reduced diameter portion 30a having a pair of outwardly inclined surfaces 30b and 300 in the same fashion as in the foregoing embodiments, said reduced diameter portion 30a being located outside the front bearing lug 7f. The cutter element 26 and the pinion gear are mounted on the spindle 30 in the same manner as in the third embodiment of FIG. 5 and, therefore, these elements are designated by the same reference numerals as used in FIG. 5.

An operating lever 33 has in a portion adjacent to its free end an opening 33a of a diameter slightly greater than the diameter of the spindle 30, through which the spindle 30 extends, and the other end is pivotally connected with the holding block 7 at an upper portion of the opening 7d by means of a transverse pin 34 extending at right angles to said operating lever 33 between the surface 7j and the surface opposed to said surface 7j. An end extremity of the slidable strip member 18 adjacent to the operating lever 30 is adapted to abut against substantially the middle portion of said lever 33. In the vicinity of the opening 33a in the lever 33, an elongated pin 35 of a length greater than the diameter of the opening 33a in the lever 33 extends through the spindle 30, the both end portions of which are situated on the both sides of said spindle 30 and contacting a surrounding portion of the lever 33 on the side adjacent to the blind hole 31.

In this embodiment shown in FIG. 6, as the slidable strip member 18 is moved in the direction toward the operating lever 33 while being pushed by the lead point of the pencil end to be shaved, that end extremity of said strip member 18 abuts against the intermediate portion of the operating lever 33 causing the latter to pivot about the transverse pin 34 so that the spindle 30 is moved in the direction toward the blind hole 31 against the compression spring 32 by the engagement between the end portions of the elongated pin 35 and that portion of the operating lever 33 surrounding the opening 33a. Thus, it is clear that, as the spindle 30 is moved against the compression spring 32, the reduced diameter portion 30a of the spindle 30 moves to a position in which it is accommodated within the thickness of the front bearing lug 7f, resulting in the angular movement of the spindle 30 and thus the cutter element 26 for the same reason as hereinbefore described.

Of course, in this embodiment shown in F IG. 6, the prevention of an excessive, unnecessary shaving of the pencil end portion can be advantageously ensured without any substantial reduction of the performance as compared with the foregoing various embodiments.

Referring now to FIGS. 7 and 8 in which a fifth embodiment of the present invention is shown, the cutter element 15 and the pinion gear 17 are mounted on a spindle 35 in the same manner as in the first embodiment of FIGS. 1 to 3. However, the spindle 35 has one end slidably supported by the front bearing lug 7f and the other end slidably inserted in a recess 36 formed in the inner wall 7k of the block 7 below the tapered projection 7m, said recess 36 having a radially outwardly diverging surface 36a as shown. This spindle 35 carries, at a portion adjacent to the end thereof inserted in the recess 36, a pair of

pins

37a and 37b extending through that portion of the spindle 35 at right angles to the longitudinal axis of the spindle 25 in spaced relation with respect to each other.

An operating lever 38 has an opening 38a through which the spindle 35 loosely extends while a portion of said lever 38 surrounding said opening 38a is sandwiched between the pair of the pins 37a and 37!; as clearly shown in FIG. 8. A compression spring 39 for urging the spindle 35 in the direction toward the recess 36 is interposed between the pinion gear 17 and the portion of the lever 38 surrounding the opening 38a so that a resilient force exerted by said spring 39 can be transmitted to one of the pins 37b and hence the spindle 35 through the lever 38. This spring 39 also acts to pivot the lever 38 about the fulcrum 7m so that the slidable strip member 18 is biased toward the pencil guide hole 7a.

It is to be noted that the space between the

pins

37a and 37b must be slightly greater than the thickness of ll I the operating lever 38 for accommodating the pivotal movement of said lever 33% about the fulcrum 7m.

in the arrangement of the embodiment of FIGS. 7 and 8, when the slidable strip member 18 is sufficiently pushed rearwardly with the feeler 20 in contact with the lead point of the pencil end portion to be shaved, the operating lever 38 is pivoted about the fulcrum 7m so that the compression spring 39 is not only compressed, but also the spindle 35 is moved in the direction opposite to the direction of the force of the spring 39 by the engagement between that portion of the lever 38 surrounding the opening 38a and the one of the pins 37a.

The angular movement of the cutter element takes place when the spindle 35 is thus moved such that the end of said spindle 35, that has been inserted in the recess 36, becomes positioned on the radially outwardly diverging surface 36a of the recess 36. This is, of course possible for the same reason as described in connection with the first embodiment of FIGS. 1 to 3, that is, by the action of the centrifugal force acting on the cutter element and the spindle so as to move them away from the axis of rotation of the holding block 7 in cooperation with the load imposed by the pencil end portion within the pencil guide hole 7a with respect to the cutter element 15. However, it is to be noted that, when the angular movement of the cutter element 15 takes place, the clearance between the slit of the pencil guide hole 7a and the peripheral surface of the cutter element 15 diverges toward the operating lever 38. This is different from the foregoing embodiments wherein the same clearance can be observed as diverging toward the front bearing lug 7f.

The pencil sharpener according to this fifth embodiment of FIGS. 7 and 8 ensures the prevention of an excessive. unnecessary shaving of the pencil in substantially the same manner as afforded by the foregoing various embodiments. It is to be noted that the cutter element 15 and the spindle 35 in the angularly moved condition can be returned to the original position by the action of the compression spring 39 only if the rotational speed of the holdingblock 7 is lowered to reduce the value of the centrifugal force and concurrently the cutter element 15 is released from the abovementioned load by removing the external pushing force applied to the opposite end portion of the pencil 21.

According to a sixth embodiment of the present invention, there is provided means for controlling the sharpness of the pencil end portion to be shaved, with which the quality, as well asthe performance, of pencil sharpeners manufactured in accordance with the teachings of the present invention can be uniformly adjusted before they are placed on the commercial market. This will be explained with reference to FIG. 9 wherein only the essential portion of the pencil sharpener is shown, the construction and function of which pencil sharpener of this embodiment are substantially the same as that in the first preferred embodiment of FIGS. 1 to 3 except for the differences which will be mentioned later.

Referring now to FIG. 9, the rear portion of the cutter holding block 7 and the shaft 70 thereof are provided with a guide hole 7p extending therethrough in alignment with the axis of rotation of the holding block 7 and having one end open to the cornered opening 7d and into the other end of which is threaded an adjustment screw 40. Within this guide hole 7p, a long pin 41,

which may be integral with the adjustment screw 40, is slidably accommodated and has one 41a in contact with the screw 44) and the other end 4111 tapered and adapted to contact the intermediate portion of the operating lever 22 in such a way as to serve as a fulcrum about which said operating lever 22 pivots, said tapered end 41b acting in the same manner as the tapered projection 7m employed in the first embodiment.

With this arrangement, by turning the adjustment screw 40, the stroke of sliding movement of the slidable strip member 18 within the cornered openign 7d of the holding block 7 can be advantageously varied as the position of the fulcrum 41b is varied. A startling feature of this sixth embodiment of HG. 9 is that deviation of the shaving capacity of a pencil sharpener from the capability of producing a desired sharpness can be substantially eliminated merely by turning the adjustment screw. This feature is particularly useful during a manufacturing process in that no precise positioning of the various parts and components employed is required with respect to the cutter holding block 7.

In order to make this feature available to a user of the pencil sharpener of the present invention, a seventh preferred embodiment of the present invention is provided as shown in FIG. 10, which will be hereinafter described.

. In the seventh embodiment as shown, the long pin 41 and the adjustment screw 40, which have been used in the foregoing embodiment of FIG. 9, are replaced by an elongated slidable rod 42 having one end tapered as indicated by 42a and adapted to contact the intermediate portion of the operating lever 22 and the other end situated outside the guide hole 7p of the holding block 7, an intermediate portion thereof extending slidably through said guide hole 7p.

Disposed in the vicinity of said other end 42!; of said slidable rod 42 and above the motor M (not shown, but shown in FIG. I) is a cam block 43 having on a lower end face an integral spindle member 43a journalled in a bearing recess 44a in a bridge panel 44. The latter bridge panel 44 is rigidly mounted on a pair of

side panels

9c and 9d (FIG. 15) constituting the mounting framework 9 together with the upright and bottom panels 9a and 912, said bridge panel 44 being mounted above the motor M. This cam block 43 has on the upper end face an integral shaft 43b in axial alignment with said spindle member 43a, a free end of which is adapted to receive an index knob 45 rotatably positioned above the top portion 3c of the covering 3 of the housing I as shown.

The cam block 43 may be of circular cross section having the longitudinal axis arranged in an offset relation to the axis of the shaft 43b or the spindle 43a so that, as said cam block is rotated by turning the index knob 45, the slidable rod 42 can be reciprocated along the guide hole 7p of the holding block 7 with its end 42b in contact with the peripheral surface of said cam block 43. This cam block 43 is has therein a recess 43c extending from the lower end face thereof in parallel relation to and adjacent to the peripheral surface of said cam block, in which said recess 430 a compression spring 46 is housed. This recess 33: is adapted to accommodate therein a detent ball 47 employed for providing a plurality of detent stops to the rotation of the cam block in cooperation with the corresponding number' of detent recesses 44b formed'in the bridge panel 44 along the curved path of travel of said detent ball 47 resulting from the rotation of the cam block.

From the foregoing, it is clear that, simply by rotating the index knob 45 causing the eccentric rotation of the cam block 43 from one detent stop to another, the same effect as afforded by the foregoing embodiment of FIG. 9 can be achieved. As hereinbefore described, this embodiment has an advantage, as compared with the foregoing embodiment, in that the user of the pencil sharpner can adjust the sharpness of the pencil as he desires.

The mechanism additionally provided in the seventh embodiment of FIG. 10 may be simplified such as shown in FIG. 1 l in which an eighth embodiment of the present invention is shown.

In FIG. 11, instead of the cam block43 employed in the foregoing embodiment, a lever 48 is utilized. This lever 48 has one end pivotally connected with an intermediate portion of the bridge panel 44 and the other end situated outside the top portion 3c of the covering 3 through a guide slot 49 in said top portion 30, an intermediate portion of said lever 48 being adapted to contact the end 42b of the slidable rod 42. An index knob 50 is mounted on the other end of the lever 48 and is slidable on the outer surface of the top portion 3c of the covering 3 so that, as the knob 50 is moved in the direction parallel to the direction of sliding movement of the slidable rod 42, the lever 48 pivots about the lower end causing the sliding movement of the slidable rod 42. Nevertheless, the sliding movement of the slidable rod 42 results in variation of the position of the fulcrum about which the operating lever 22 pivots.

In the foregoing various embodiments, an arrangement has been described in which completion of the shaving operation by the cutter element can be detected by the sense of touch or hearing of the user of the pencil sharpener. To eliminate this inconvenience, it is possible to provide a signaling device for signaling to the user or operator the completion of the shaving operation by the cutter element. This is shown in FIG. 12 in which the signaling device according to a ninth embodiment of the present invention is employed in the form of a warning lamp as indicated by 51.

Referring now to FIG. 12, the warning lamp 51 is housed in a casing 52 on the interior surface of the top portion 3c of the covering 3 with a portion of said top portion 3c above said lamp 51 being a window 53 through which the user can observe whether the lamp position, urges the slidable rod 42 in the direction toward the cornered opening 7d.

The arrangement of FIG. 12 functions as follows. As the pencil end portion shaved to sharpen the lead point thereof in the manner as hereinbefore described, the slidable strip member 18 is rearwardly moved. However, in view of the fact that an axial pushing force exerted by the actuator member SW; of the switch SW on the slidable rod 42 has value smaller than the axial pushing force exerted by the compression spring 23 on the cutter element carrying spindle 16, the rearward movement of the slidable strip member 18 is accompanied by a pivotal movement of the operating lever 22 about the tapered end of the spindle 16, causing the slidable rod to move rearwardly with the tapered end 42a thereof in contact with the operating lever 22 so that the actuator member SW operates the button SW to switch the switch SW on with the result that the lamp 1 51 is illuminated.

51 is switched on or not. For operating this signalling lamp 51, a switch SW is mounted, for example, on the bridge panel 44 so as to beoperated by the slidable rod An electrical circuit associated with this signalling lamp 51 and the switch SW is clearly shown in FIG. 13. From the circuit diagram of FIG. 13, it is clear that the lamp 51 and the switch SW are disposed in parallel relation to the motor M and in series relation to the switching circuit of the ring-shaped switch structure 6.

The switch SW is preferably of the type having a pivotable actuator member SW normally urged by any suitable means, such as a coil spring, away from a switch button SW movable by said actuator member SW, to operate the switch SW. The actuator member SW, is adapted to be operated by the end 42b of the slidable rod 42 and, when the switch SW is in the off- After the actuator member SW, has operated the button SW no further rearward movement of the slidable rod 42 takes place and, hence, the tapered end 42a of the rod 42 acts as a fulcrum about which the operating lever 22 pivots to move the spindle 16 such that the reduced diameter portion 16a accommodates therein the thickness of the front bearing lug 7f in the manner as hereinbefore described.

In this embodiment, in view of the fact that the pencil sharpening operation by the use of an electric pencil sharpener is finished in a manner of seconds, it does not take more than 0.3 second from the completion of the rearward movement of the slidable rod'42 to the commencement of angular movement of the cutter element 15 and, therefore, no substantial inconvenience will arise even if the user construes the illumination of the signaling lamp 51 as indicating the completion of the shaving of the pencil end portion. The switch SW can be, of course, brought into the off-position substantially at the same time the external pushing force applied to the pencil is removed which accompanies the return of the cutter element 15 in the angularly moved condition to the original position.

The embodiment of FIG. 12 may be combined with the embodiment of FIG. 10 or FIG. 11 as shown in FIG. 14 or FIG. 16, respectively, in the form of tenth and eleventh embodiments of the present invention.

Referring first to FIG. 14 and FIG. 15 in which the tenth embodiment of the present invention is shown, the switch SW is located between the gear wheel 10 and the cam block 43. As clearly shown in FIG. 15, this switch SW is rigidly secured on a substantially L- shaped follower 54 having an upper end provided with a fine adjustment screw 55 threadably extending therethrough, the function of which will be mentioned later, and pivotally supported on the bridge panel 44 by means of a channel-shaped member 56 having a pair of arms sandwiching the bridge panel 44, a pin member 57 being in turn inserted through one of said arms, said bridge panel 44 and the other of said arms for pivotal movement of the switch SW. This switch SW is normally urged to pivot about the pin member 57 by means of a wire spring 58 such that the fine adjustment screw 55 is contacted with the peripheral surface of the cam block 43 for permitting the follower 54 to follow the peripheral surface of the cam block 43.

It is to be noted that the cam block 43 employed in this embodiment is in the shape of a comma as clearly shown in FIG. 15. Mounted on the bridge panel 44 at a position rearwardly of the cam block 43 is an electrical terminal board having a plurality of terminal members for electrical connection with a power source by means of wires.

In this arrangement, not only is the signaling lamp 51 lighted at the completion of the shaving of the pencil end, the but also the sharpness of the pencil end can be selected as desired merely by rotating the index knob 45.

The eleventh embodiment shown in FIG. 16 and FIG. 17 is such that the switch SW is pivotally supported by the side panel 9c by means of a bracket member 59, as clearly shown in FIG. 17, so that said switch SW can be pivoted about a pin 60 in response to the pivotal movement of the lever 48. It is to be noted that this switch SW is normally urged to pivot in one direction by a wire spring 61 so that a poition of the switch SWcontacts substantially the middle portion of the lever 48. The same effect as afforded by the foregoing embodiment of FIGS. 15 and 16 can obviously be obtained by sliding the index knob 50.

Although the present invention has been fully disclosed in conjunction with the various preferred embodiments thereof, changes and modifications will be apparent to those skilled in the art. For example, the front and rear bearing lugs 7f and 7g and the retainer 19 for slidably supporting the slidable strip member 18 can be integrally formed such as shown in FIG. 18. However, this arrangement of FIG. 18 is not a claimed feature of the present invention and, accordingly, the details thereof are herein omitted. In addition, although the signaling device has been described as comprising an indicating lamp, this may be replaced by a buzzer. Thus, such changes and modifications should be, unless otherwise they depart from the true scope and spirit of the present invention, construed as included therein.

What is claimed is:

1. An electrical pencil sharpener comprising a power source, a switch and a motor, said switch being disposed between said power source and said motor, a cutter holding block rotatable in one direction by said motor when said switch is closed, cutter means operatively carried by said cutter holdingblock so as to rotate in the direction opposite to the rotational direction of said cutter holding block, whereby an end portion of a pencil inserted in the pencil sharpener can be sharpened in engagement with said cutter means during the rotation of said cutter holding block, and means for separating said cutter means from said engagement with said pencil end portion when said pencil end portion has been sharpened to a predetermined sharpness to ensure the prevention of an excessive, unnecessary shaving of the pencil beyond the predetermined sharpness, said cutter means being returned from the separated position to' an original position, in which any fresh or spoiled pencils are ready to be sharpened by the electric pencil sharpener when an external pushing force that has been applied to the opposite end portion of said pencil is removed.

2. An electric pencil sharpener comprising a power source, a switch and a motor, said switch being disposed between said power source and said motor, a cutter holding block having on one end an integral shaft operatively connected with said motor for rotation of said cutter holding block in one direction and in the other end a pencil guide hole for accommodating therein an end portion of a pencil to be shaved and tapering toward a substantially intermediate portion thereof in axial alignment with the axis of rotation of said holding block, a ring-shaped gear firmly secured to a framework and having an inner peripheral surface with gear teeth thereon, cutter means including a cutter, a pinion gear and a spindle rotatably supported by said cutter holding block for rotatably carrying said cutter thereon, said cutter means being normally maintained by a spring element in a first position in which said cutter is engageable with said pencil end portion within said pencil guide hole for sharpening said pencil end portion and capable of being moved to a second position in which the engagement between said cutter and said pencil end portion is released, said pinion gear being in constant mesh with said gear teeth of said ringshaped gear, whereby rotation of said cutter holding block results in rotation of said cutter in the direction opposite to said rotational direction of said cutter holding block for effecting a shaving of said pencil end portion with said cutter in said engagement with said pencil end portion, and means operable in response to a forward movement of said pencil effected by the application of an axial pushing force to the opposite end portion of said pencil such that said cutter means can be brought into said second position when said pencil end portion is substantially shaved to a predetermined sharpness, thereby to ensure the prevention of an excessive, unnecessary shaving of the pencil, said cutter means being capable of returning to said first position by the action of said spring element when said external pushing force is removed.

3. An electric pencil sharpener as claimed in claim 2 wherein said switch is adapted to close upon insertion of the pencil into the electric pencil sharpener for energizing the motor and open upon withdrawal of said pencil therefrom for deenergizing said motor.

4. An electric pencil sharpener as claimed in claim 2 wherein said means operable in response to said forward movement of the pencil inserted in the pencil sharpener comprises a slidable member slidable in contact with the pencil end portion and an operating lever pivotable about a fulcrum in response to the slid ing movement of said slidable member, and further comprising means in said cutter holding block for operatively accommodating therein said slidable member and said operating lever and having therein said fulcrum about which said operating lever pivots.

5. An electric pencil sharpener comprising a power source, a switch and a motor, said switch being disposed between said power source and said motor and adapted to close upon insertion of a pencil into the electric pencil sharpener fro energizing said motor and open upon withdrawal of said pencil therefrom for deenergizing said motor, a cutter holding block having on one end an integral shaft operatively connected with said motor for rotation of said cutter holding block in one direction and in the other end a pencil guide hole for accommodating therein an end portion of the pencil to be shaved and tapering toward a substantially intermediate portion thereof in axial alignment with the axis of rotation of said holding block, a ring-shaped gear firmly secured to a framework and having gear teeth on an inner peripheral surface, cutter means including a cutter, a pinion gear and a spindle rotatably supported by said cutter holding block for rotatably carrying said cutter thereon, said cutter means being normally maintained by a spring element in a first position in which said cutter is engageable with said pencil end portion within said pencil guide hole for sharpening said pencil end portion and capable of being brought into a second position in which the engagement between said cutter and said pencil end portion is released, said pinion gear being in constant mesh with said gear teeth of said ring shaped gear, whereby rotation of said cutter holding block results in rotation of said cutter in the direction opposite to said rotational direction of said cutter holding block for effecting a shaving of said pencil end portion with said cutter in said engagement with said pencil end portion, a slidable member and an operating lever, said slidable member being capable of sliding in response to a forward movement of said pencil effected by the application of an axial pushing force to the opposite end portion of said pencil and said operating lever being capable of pivoting about a fulcrum in response to the movement of said slidable member such that said cutter means can be brought into said second position when said pencil end portion is substantially shaved to a predetermined sharpness, thereby to ensure the prevention of an excessive, unnecessary shaving of the pencil, said cutter means being capable of returning to said first position by the action of said spring element when said external pushing force is removed, and means formed in said cutter holding block for operatively accommodating therein said slidable member and said operating lever and having therein said fulcrum about which said operating lever pivots.

6. An electric pencil sharpener as claimed in claim wherein said spindle is slidably supported by said cutter holding block by means of a pair of bearing members and having a reduced diameter portion at one end portion thereof adjacent to one of said bearing members, said spring element being disposed outside said one of said bearing members such as to urge said spindle in one direction with the other end thereof engageable with said operating lever, said reduced diameter portion being capable of, as said spindle is moved in the direction opposite to the urging direction of said spring element in response to the pivotal movement of said operating lever, accommodating therein the thickness of said one of said bearing members, thereby permitting said cutter means to move to said second position.

7. An electric pencil sharpener as claimed in claim 5 wherein said spindle is in the form of a screw member having one end supported by said cutter holding block by means of a bearing member and the other end fixedly threaded into a blind hole formed in said cutter holding block and having a reduced diameter portion at one end portion thereof between said bearing member and said cutter with said spring element interposed therebetween, said cutter having an annular ring member so sized as to fit into said reduced diameter portion as said cutter is moved against the spring element in response to the pivotal movement of said operating lever, whereby said cutter means can be positioned in said second position.

8. An electric pencil sharpener as claimed in claim 5 wherein said spindle has one end slidably supported by said cutter holding block and the other end slidably accommodated in a blind hole in said cutter holding block with said spring element interposed between said other end and the bottom of said blind hole for urging said spindle in one direction, said spindle having a reduced diameter portion at said one end thereof located outside said bearing member, said reduced diameter portion being capable of, as said spindle is moved in the direction opposite the urging direction of said spring element in response to the pivotal movement of said operating lever, accommodating therein the thickness of said bearing member, thereby permitting said cutter means to move to said second position.

9. An electric pencil sharpener as claimed in claim 5 wherein said spindle has one end slidably supported by said cutter holding block by means of a bearing member and the other end slidably inserted in a recess in said cutter holding block and having an outwardly diverging surface, and includes a pair of pins, each extending at right angles to the axis of said spindle in a spaced relation with respect to each other with the space therebetween adapted to accommodate the operating lever and said spring element is interposed between said pinion gear and said operating lever for urging said operating lever and said spindle in one direction, said cutter means being movable to said second position whensaid spindle is moved against the spring element in response to the pivotal movement of said operating lever causing said other end of said spindle to rest on said radially outwardly diverging surface of said recess.

10. An electric pencil sharpener as claimed in claim 5 wherein said slidable member is slidably supported by a retainer member secured to said holding block within said accommodating means and has at one end a feeler contactable with said pencil end portion and the other end pivotally connected with a corresponding end of said operating lever.

11. An electric pencil sharpener as claimed in claim 10 wherein said other end of said slidable member is adaptedto abut against said corresponding end of said operating lever.

12. An electric pencil sharpener as claimed in claim 5 further comprising means for adjusting the sharpness of said pencil end portion by selectively varying the position of said fulcrum about which said operating lever pivots.

13. An electric pencil sharpener as claimed in claim i 12 wherein said adjusting means comprises a slidable pin member silidably accommodated within a guide hole in the shaft of the cutter holding block and has one end serving said fulcrum, and an adjustment screw adjustably threaded into said guide hole and engaged with the other end of said pin member so that turning of said adjustment screw results in the sliding movement of i said pin member, thereby permitting the position of said fulcrum to vary in response to said turning of said adjustment screw.

14. An electric pencil sharpener as claimed in claim 12 wherein said adjusting means comprises a slidable rod slidably accommodated with a guide hole in the shaft of the cutter holding block and has one end serving as said fulcrum about which the operating lever pivots, and a manually operable lever having one end pivotally connected with the framework and on the other end a knob, the other end of said slidable rod being adapted to be pushed by a substantially intermediate portion of said manually operable lever, whereby the pivotal movement of said manually operable lever results in the sliding movement of said rod, thereby permitting the position of said fulcrum to vary in response to said pivotal movement of said manually operable lever.

15. An electric pencil sharpener as claimed in claim 12 wherein said adjusting means comprises a slidable rod slidably accommodated within a guide hole in the shaft of the cutter holding block and has one end serving said fulcrum about which the operating lever pivots and the other end situated outside said guide hole and a cam block rotatably supported by the framework and having a plurality of detent stop positions whereby, by rotating said cam block, said slidable rod slides in response to the rotation of said cam block causing the position of said fulcrum to vary.

16. An electric pencil sharpener as claimed in claim wherein said shaft has a guide hole extending in alignment with the axis of rotation of said cutter holding block in which said guide hole a slidable rod is accommodated and has one end serving as said fulcrum, and further comprising a signaling device including a switch operable by the other end of said slidable rod, whereby said signaling device can be operated substantially at Y the same time said cutter meansis brought into said second position.

17. An electric pencil sharpener comprising a power source, a switch and a motor, said switch being disposed between said power source and said motor and adapted to close upon insertion of a pencil into the electric pencil sharpener for energizing said motor and open upon withdrawal of said pencil therefrom for deenergizing said motor, a cutter holding block having on one end an integral shaft operatively connected with said motor for rotation of said cutter holding block in one direction and at the other end a pencil guide hole for accommodating therein an end portion of the pencil to be shaved and tapering toward a substantially intermediate portion thereof in axial alignment with the axis of rotation of said holding block, a ring-shaped gear firmly secured to a framework and having gear teeth on an inner peripheral surface, cutter means including a cutter, a pinion gear and a spindle rotatably supported by said cutter holding block for rotatably carrying said cutter thereon, said cutter means being normally maintained by a spring element in a first position in which said cutter is engageable with said pencil end portion within said pencil guide hole for sharpening said pencil end portion and capable of being brought into a second position in which the engagement between said cutter and said pencil end portion is released, said pinion gear being in constant mesh with said gear teeth of said ringshaped gear, whereby rotation of said cutter holding block results in rotation of said cutter in the direction opposite to said rotational direction of said cutter holding block for effecting a shaving of said pencil end portion with said cutter in said engagement with said pencil end portion, a slidable member and an operating lever, said slidable member being capable of sliding in response to a forward movement of said pencil effected by the application of an axial pushing force to the opposite end portion of said pencil and said operating lever being capable of pivoting about a fulcrum in response to the movement of said slidable member such that said cutter means can be brought into said second position when said pencil end portion is substantially shaved to a predetermined sharpness, thereby to ensure the prevention of an excessive, unnecessary shaving of the pencil, said cutter means being capable of returning to said first position by the action of said spring element when said external pushing force is removed, means in said cutter holding block for operatively accommodating therein said slidable member and said operating lever, a slidable rod slidably positioned in a guide hole in said shaft of said cutter holding block in alignment with the axis of rotation of said cutter holding block and having one end situated within said accommodating means and serving as said fulcrum and the other end situated outside said cutter holding block, and means operatively associated with the other end of said slidable rod for adjusting the sharpness of said pencil end portion by selectively varying the position of said one end of said slidable rod and, hence, said fulcrum about which said operating lever pivots.

18. An electric pencil sharpener as claimed in claim 17 further comprising a signaling device for indicating to the user of the electric pencil sharpener a completion of the shaving operation, said signaling device including an additional switch operatively disposed between the other end of said slidable rod and said adjusting means such that said additional switch is activated by said slidable rod to operate said signaling device.

Claims

1. An electrical pencil sharpener comprising a power source, a switch and a motor, said switch being disposed between said power source and said motor, a cutter holding block rotatable in one direction by said motor when said switch is closed, cutter means operatively carried by said cutter holding block so as to rotate in the direction opposite to the rotational direction of said cutter holding block, whereby an end portion of a pencil inserted in the pencil sharpener can be sharpened in engagement with said cutter means during the rotation of said cutter holding block, and means for separating said cutter means from said engagement with said pencil end portion when said pencil end portion has been sharpened to a predetermined sharpness to ensure the prevention of an excessive, unnecessary shaving of the pencil beyond the predetermined sharpness, said cutter means being returned from the separated position to an original position, in which any fresh or spoiled pencils are ready to be sharpened by the electric pencil sharpener when an external pushing force that has been applied to the opposite end portion of said pencil is removed.

2. An electric pencil sharpener comprising a power source, a switch and a motor, said switch being disposed between said power source and said motor, a cutter holding block having on one end an integral shaft operatively connected with said motor for rotation of said cutter holding block in one direction and in the other end a pencil guide hole for accommodating therein an end portion of a pencil to be shaved and tapering toward a substantially intermediate portion thereof in axial alignment with the axis of rotation of said holding block, a ring-shaped gear firmly secured to a framework and having an inner peripheral surface with gear teeth thereon, cutter means including a cutter, a pinion gear and a spindle rotatably supported by said cutter holding block for rotatably carrying said cutter thereon, said cutter means being normally maintained by a spring element in a first position in which said cutter is engageable with said pencil end portion within said pencil guide hole for sharpening said pencil end portion and capable of being moved to a second position in which the engagement between said cutter and said pencil end portion is released, said pinion gear being in constant mesh with said gear teeth of said ring-shaped gear, whereby rotation of said cutter holding block results in rotation of said cutter in the direction opposite to said rotational direction of said cutter holding block for effecting a shaving of said pencil end portion with said cutter in said engagement with said pencil end portion, and means operable in response to a forward movement of said pencil effected by the application of an axial pushing force to the opposite end portion of said pencil such that said cutter means can be brought into said second position when said pencil end portion is substantially shaved to a predetermined sharpness, thereby to ensure the prevention of an excessive, unnecessary shaving of the pencil, said cutter means being capable of returning to said first position by the action of said spring element when said external pushing force is removed.

4. An electric pencil sharpener as claimed in claim 2 wherein said means operable in response to said forward movement of the pencil inserted in the pencil sharpener comprises a slidable member slidable in contact with the pencil end portion and an operating lever pivotable about a fulcrum in response to the sliding movement of said slidable member, and further comprising means in said cutter holding block for operatively accommodating therein said slidable member and said operating lever and having therein said fulcrum about which said operating lever pivots.

6. An electric pencil sharpener as claimed in claim 5 wherein said spindle is slidably supported by said cutter holding block by means of a pair of bearing members and having a reduced diameter portion at one end portion thereof adjacent to one of said bearing members, said spring element being disposed outside said one of said bearing members such as to urge said spindle in one direction with the other end thereof engageable with said operating lever, said reduced diameter portion being capable of, as said spindle is moved in the direction opposite to the urging direction of said spring element in response to the pivotal movement of said operating lever, accommodating therein the thickness of said one of said bearing members, thereby permitting said cutter means to move to said second position.

9. An electric pencil sharpener as claimed in claim 5 wherein said spindle has one end slidably supported by said cutter holding block by means of a bearing member and the other end slidably inserted in a recess in said cutter holding block and having an outwardly diverging surface, and includes a pair of pins, each extending at right angles to the axis of said spindle in a spaced relation with respect to each other with the space therebetween adapted to accommodate the operating lever and said spring element is interposed between said pinion gear and said operating lever for urging said operating lever and said spindle in one direction, said cutter means being movable to said second position when said spindle is moved against the spring element in response to the pivotal movement of said operating lever causing said other end of said spindle to rest on said radially outwardly diverging surface of said recess.

11. An electric pencil sharpener as claimed in claim 10 wherein said other end of said slidable member is adapted to abut against said corresponding end of said operating lever.

13. An electric pencil sharpener as claimed in claim 12 wherein said adjusting means comprises a slidable pin member silidably accommodated within a guide hole in the shaft of the cutter holding block and has one end serving said fulcrum, and an adjustment screw adjustably threaded into said guide hole and engaged with the other end of said pin member so that turning of said adjustment screw results in the sliding movement of said pin member, thereby permitting the position of said fulcrum to vary in response to said turning of said adjustment screw.

16. An electric pencil sharpener as claimed in claim 5 wherein said shaft has a guide hole extending in alignment with the axis of rotation of said cutter holding block in which said guide hole a slidable rod is accommodated and has one end serving as said fulcrum, and further comprising a signaling device including a switch operable by the other end of said slidable rod, whereby said signaling device can be operated substantially at the same time said cutter means is brought into said second position.

17. An electric pencil sharpener comprising a power source, a switch and a motor, said switch being disposed between said power source and said motor and adapted to close upon insertion of a pencil into the electric pencil sharpener for energizing said motor and open upon withdrawal of said pencil therefrom for deenergizing said motor, a cutter holding block having on one end an integral shaft operatively connected with said motor for rotation of said cutter holding block in one direction and at the other end a pencil guide hole for accommodating therein an end portion of the pencil to be shaved and tapering toward a substantially intermediate portion thereof in axial alignment with the axis of rotation of said holding block, a ring-shaped gear firmly secured to a framework and having gear teeth on an inner peripheral surface, cutter means including a cutter, a pinion gear and a spindle rotatably supported by said cutter holding block for rotatably carrying said cutter thereon, said cutter means being normally maintained by a spring element in a first position in which said cutter is engageable with said pencil end portion within said pencil guide hole for sharpening said pencil end portion and capable of being brought into a second position in which the engagement between said cutter and said pencil end portion is released, said pinion gear being in constant mesh with said gear teeth of said ring-shaped gear, whereby rotation of said cutter holding block results in rotation of said cutter in the direction opposite to said rotational direction of said cutter holding block for effecting a shaving of said pencil end portion with said cutter in said engagement with said pencil end portion, a slidable member and an operating lever, said slidable member being capable of sliding in response to a forward movement of said pencil effected by the application of an axial pushing force to the opposite end portion of said pencil and said operating lever being capable of pivoting about a fulcrum in response to the movement of said slidable member such that said cutter means can be brought into said second position when said pencil end portion is substantially shaved to a predetermined sharpness, thereby to ensure the prevention of an excessiVe, unnecessary shaving of the pencil, said cutter means being capable of returning to said first position by the action of said spring element when said external pushing force is removed, means in said cutter holding block for operatively accommodating therein said slidable member and said operating lever, a slidable rod slidably positioned in a guide hole in said shaft of said cutter holding block in alignment with the axis of rotation of said cutter holding block and having one end situated within said accommodating means and serving as said fulcrum and the other end situated outside said cutter holding block, and means operatively associated with the other end of said slidable rod for adjusting the sharpness of said pencil end portion by selectively varying the position of said one end of said slidable rod and, hence, said fulcrum about which said operating lever pivots.