US2958987A - Knife sharpener - Google Patents

Description

Nov. 8, 1960 JEPSON KNIFE SHARPENER Filed Aug. 18, 1958 III/'II/ KNIFE SHARPENER Ivar Jepson, Oak Park, Ill., assignor to Sunbeam Corporation, Chicago, 111., a corporation of Illinois Filed Aug. 18, 1958, Ser. No. 755,624

3 Claims. (Cl. 51-116) The present invention relates to a knife sharpener, and more particularly to a household type of knife sharpener.

Small power driven knife sharpeners for use in the home to sharpen kitchen knives and the like are well known in the appliance field. Such sharpeners commonly employ several rotating wheels or discs between which the knife to be sharpened is drawn. The two abrasive discs are frequently mounted coaxially and are driven by a small electric motor. Although the use of two grinding wheels permits both sides of the knife to be sharpened at the same time, such an arrangement presents problems with respect to obtaining the proper angle benited States Patent tween the grinding wheels and the blade being sharpened.

'In sharpening a knife, it is desirable to shape the cutting edge so that it has a narrow angle defined by the intersecting surfaces of the blade.

Regardless of how the surfaces of two axially spaced grinding discs are shaped, I

this desired angle at the cutting edge, it is necessary to have the grinding surfaces overlapping so they define a it is difficult to obtain a well defined angle on the cutting edge which terminates at a sharp, even apex. To obtain sharp angle. It would be desirable, therefore, to provide a knife sharpener having overlapping grinding surfaces to permit the grinding of a well defined angle at the cutting edge.

It has also been found that a grinding wheel in a knife sharpener should rotate in a particular direction with fore, preferable to have the grinding wheels or discs moving a direction from the cutting edge toward the back of the knife in the area of engagement. In the convention'al sharpeners having the co-axially aligned discs,

both types of relative engagement are obtained between the blade and the abrasive discs resulting in a feather vedge along at least a portion of the blade. It would be desirable, therefore, to have a knife sharpener in which guiding means are provided to insure engagement between the knife blade and the grinding wheels in an area in which the grinding wheels would be moving from the cutting edge toward the back of the knife. I It is accordingly an object of the invention to provide a new and improved knife sharpener.

Another object of the invention is to provide a knife sharpener having overlapping grinding surfaces and knife guiding means insuring proper engagement of the knife by the grinding surfaces and without any dulling effect on the knife.

Still another object of the invention is to provide a knife sharpener in which the drivingmotor and grinding wheels 3 are mounted on a frame to form a unit insertable into a hollow housing provided with a knife guiding slot and also having index means to precisely locate the unit relative to the slot.

A further object of the invention is to provide a knife 37 . plate portions 17 and 18 which extend upwardly on sharpener in which a switch actuator forms a segment of the housing and carries switch contacts thereon together with stop means in the housing for pressing the contacts together as the actuator is pressed inwardly of the housing.

Further objects and advantages of the present invention will become apparent as the following description proceeds, and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of the present invention, reference may be had to the accompanying drawings in which:

Fig. 1 is a perspective view of a knife sharpener forming one embodiment of the invention and during use to sharpen a knife;

Fig; 2 is an enlarged, fragmentary, vertical section of the knife sharpener shown in Fig. 1 and taken along line 2-2 of Fig. 3 showing the motor in full lines and portions of the switch;

Fig. 3 is an enlarged top plan view of the internal mechanism of the knife sharpener with a portion of the housing cut away;

Fig. 4 is an enlarged, fragmentary, vertical section of the knife sharpener taken along line 44 of Fig. 2 with only one of the grinding wheels shown in full; and

Fig. 5 is an enlarged, fragmentary section of a portion of the knife sharpener and showing an actuating switch thereof.

The present invention provides a knife sharpener including a pair of overlapping cup-shaped grinding wheels :driven at different rotational speeds such that the speed of the rims of the wheels are the same. The knife sharpener mechanism including the grinding wheels fits into a cup-shaped housing of plastic having a slot in the upper end thereof. Portions of the mechanism frame engage projections on the housing and notches in the housing to precisely locate the grinding wheels in a position in which only the proper side of the wheels can be engaged by a knife in the slot. The housing has an opening toward which a plastic plate carrying switch contacts is urged. When the plate is pressed manually inwardly from the opening, one of the contacts engages a stop in the housing and closes on the other contact.

There is shown in the drawings a knife sharpener which includes a pair of grinding wheels 10 and 11 forming a part of a unitary assembly including frame members 12 and 13 and an electric motor 14. The frame members 12 and 13 consist of two vertically disposed, spaced plate members between which the electric motor 14 is clamped. The unitary assembly fits into a plastic casing or housing 15 composed of plastic material such as vinyl or other suitable plastic material. The housing 15 is provided with a slot 16 for aligning a knife K (Fig. l) with the wheels 10 and 11 and limiting engagement of the knife to portions of the grinding wheel which are rotating in a direction for the best sharpening action. The guide slot keeps the knife blade out of contact with the other'portions of the grinding wheels. To prevent movement of the unitary assembly relative to the slot 16, the frame members 12 and 13 are provided with upstanding arcuate the outside of the grinding wheels 10 and 11.

A pair of ribs or bracket projections 19 and 2 0 are formed integrally with the housing 15 and extended across the bottom of the upper wall in a direction parallel to the guide slot 16. The arcuate plate portions 17 and 18 are shaped to fit the concave upper wall ofhousing 15 and are spaced to straddle the bracket projections 19 and 20. The engagement between the plate portions 1'! and I8 and the bracket projections 19 and 20 assures accurate location of the unitary assembly carrying ath'e grinding wheels and 11 with respect to the slot 16. Any misalignment between slot 16 and the grinding wheels 10 and 11 would, of course, result in the knife K engaging the grinding wheels 01f center and having the cutting edge ground off center.

To form a grinding chamber within which the grinding wheels 10 and 11 are mounted, the frame members 12 and 13 are formed with inwardly projecting arcuate walls or shelves 25 and 26 respectively. The arcuate walls 25 and 26 ext-end above the motor 14 and abut each other along a plane defined by the slot 16. As can be best seen in Fig. 4, the wall 26 extends outwardly to engage the walls of casing 15. Similarly, the wall 26 also engages adjacent portions of casing 15. The walls 25 and 26 together with the plate portions 17 and 18 cooperate with the casing to form an enclosure or chamber for the. grinding wheels 10 and 11. With the grinding wheels separated from the motor 14, the abrasive grit and filings associated with the sharpening operation are kept, out of the motor where they might cause malfunctioning.

In order to further limit relative movement between casing 15 and the unitary assembly with its associated grinding wheels 10 and 11, there are provided notches 21 and 22 (Fig. 4) located at the ends of the slot 16 and extending transversely thereto. The notches 21 and 22 are formed by overhanging bars or ribs 23 and 24 molded integrally with the housing 15. End portions of arcuate shelves 25 and 26 fit into the notches 21 and 22, respectively.

To assemble the frame members 12 and 13 with the motor 14 therebetween, a pair of cap screws 27 are employed which extend through clearance holes in frame member 12 and the field assembly of motor 14 and engage tapped holes in the frame member 13. The motor 14 is thus located and clamped between the frame members to form the unitary assembly. To insure proper alignment of the frame members 12 and 13, the portions ofthe frame members which engage the motor 14 are in the form of inwardly extending bosses 29 which surround the cap screws 27 and have their faces machined for accurate engagement with the field of motor 14.

The cup-shaped housing 15 is retained in assembled relation to the frame members 12 and 13 by four cap screws 30. To support the cap screws 30, the frame members 12 and 13 have four casing assembly lugs 32 which extend outwardly in a horizontal plane from each corner of the unitary assembly including frame members 12 and 13. Each lug 32 has a clearance hole formed therein to accommodate one of the upwardly extending cap screws 30. To receive the ends of the cap screws 30, the cup-shaped housing 15 is formed with downwardly projecting posts 31. The cap screws 30 extend upwardly through the holes in the lugs 32 into threaded engagement with the posts 31 to draw the lugs against the ends of posts 31.

The motor 14 is provided with an armature shaft 41 on which are secured and keyed thereto gears 42 and. 43 and a cooling fan 44. To enclose the motor completely, the housing 15 is provided with a bottom cover plate 46 which serves as a closure for the bottom opening in housing 15. To prevent the motor 14 from overheating within the casing, a pair of air vent openings 45 and 47 are provided in the cover plate 46. The fan 44 rotates in such'a direction to draw air in through inlet opening 45 on one side of the cover plate 46 and discharge it through the outlet opening 47 on the opposite side of the cover plate. The cover plate is secured to the frame members 12 and 13 by cap screws 48 and fits into an inner groove 49 in the housing 15. The gears 4'2 and 43 mesh with and drive gears 52 and 53 keyed to shafts 54 and 55, respectively. The shafts 54 and 55 are journaled in bushings 56 in bores 57 formed in the members 12 and 13 at precise angles relative to one another such that the shafts 54 and 55 tilt both upwardly and toward the back of the housing 15 as illustrated in Figs. 2 and 3.

Because of the angle between the armature shaft 41 and the shafts 54 and 55 mounting the grinding discs, bevel gears are used for gears 42, 43, 52 and 53.

In one constructed embodiment of the invention, the angle between the axis of each of the shafts and the horizontal was about twenty degrees. The angle between the axis of each of the shafts and a vertical plane through the armature shaft was about three and one-half degrees. Both of the grinding wheels 10 and 11 are cup-shaped having central base portions 10a and 11a respectively. To permit mounting of the grinding wheels 10 and 11 on the shafts 54 and 55, the central portions 10a and 11a are provided with holes or apertures 10b and 11b which receive the mounting means. To accomplish the mounting of grinding wheel 10 on shaft 54, a pair of metal washer-like members 58 and 59'are keyed to a nut 60 with the grinding wheel clamped between the washers. To maintain the grinding wheel centered with respect to shaft 54, the washer 58 is formed with a shouldered portion 58a which is received in the hole 10b in the grinding wheel. The nut 60 is threadedly received on the end of shaft 54 to complete the assembly of grinding wheel 10 to the shaft. Similarly the grinding wheel 11 is secured to shaft 55 by washer-like members 61 and 62 keyed to a nut 63 threaded on the upper end of the shaft 55.

The grinding wheels 10 and 11 are formed with cylindrical side walls 10c and 110 respectively which extend from the central portions 10a and 11a of the grinding wheels. The, outer edges of the side walls and terminate in grinding faces 10d and 11d respectively which consist, of annular surfaces substantially perpendicular to the axes of shafts 54 and 55 respectively. Because of the orientation of the shafts 54 and 55, it is necessary to have the faces 10d and 11d slightly conical in shape. In the constructed embodiment in which the shafts angled three and one-half degrees from the vertical plane through the axis of the armature shaft the surfaces 10d and 110? were angled such that any radial segment thereof defined an angle of 3 /2 degrees with a plane perpendicular to the axis of shaft 54 or shaft 55 respectively. The grinding wheel 10 has an external diameter of portion 100 which is slightly less than the inner diameter of the cylindrical portion 110 of the cupshaped wheel 11. The wheel 10 is positioned so that its lower portion projects into the wheel 11 and the planes defined by the grinding faces 10d and 11d overlap. By reason of the overlapping relationship of the grinding faces 10d and 11d, each face engages the cutting edge of the knife K when the knife is resting on an end portion or knife rest 64 of the groove 16.

The shafts 5'4 and 55 and the wheels 10' and 11 are tilted slightly in the horizontal plane to form an angle preferably of about three and one-half degrees in a horizontal direction toward the back of the housing 15 away from the knife rest 64. When the knife is resting on the knife rest 64 and against the wheels 10 and 11, it is engaged only by the portions of grinding faces 10d and 11d which are positioned toward the front of the housing. These portions are designated by numerals 65 and. 66 in Fig. 3. The motor 14 drives the wheels 10 and 11 in the same direction which is such that the portions of the rims of the wheel nearest the stop 64 or the front of the housing are being moved upwardly so that grinding occurs from the cutting edge toward the back of the knife K which provides the best sharpening action. Because of the slightly conical shape provided on the grinding faces 10d and 11d, the knife edge when resting on the knife rest or stop 64 is engaged across the entire widths of the faces 10d and 11d at the points of engagement 65 and 66.

Means have been provided so that the grinding faces 10d and 11d of the wheels 10 and 11 travel at substantially the same linear speed. Since grinding faces 10d and 11d have different diameters, the equality in linear speed is accomplished by having different gear ratiosv between the gears 42 and 52 and respectively. The gear, 43 is smaller than the gear 42 Y and the gear 53 is larger than the gear 52 by such amounts ta e the gears 43 and 53,

that the face d ofthe wheel v10 has the same linear The bar 23 of the housing is positioned sufiiciently low,

and in engagement with the wheels 10 and 11, but the 8 bar 23 is positioned sufiiciently high that when the knife edge is moved away from the knife rest 64 and moved into only the portions 65 and 66 of the wheels 10 and 11 on the other side of the wheels from the bar 23. Hence, the knife edge is kept out of contact with the portions of the wheels 10 and 11 moving downwardly relative to the knife blade. Consequently, grinding across the blade toward the cutting edge never occurs with the subject invention.

Electric power is supplied to the motor 14 from electric cord 71 passing through a suitable opening at the rear of the housing 15. One conductor (not shown) of the cord 71 is connected directly to the motor as is well known in the art and the other conductor 72 is connected to a switch 69 which is made up of a pair of vertically extending L-shaped contact springs 73 and 77. The switch 69 is mounted on and operated by a pivotally mounted plate member 75 which is fabricated of some suitable insulating material such as plastic. To pivotally mount the plate member 75 on the frame members 12 and 13, a pair of spaced, parallel arms 79 extend upwardly and are pivotally connected by pins 80 to lugs 81 which project from the frame members 12 and 13.

The bottom of the plate member 75 is provided with an inwardly projecting, elongated boss 74 which serves to mount the L-shaped contact springs 73 and 77 Screws 76 and 78 are threadedly received in boss 74 to secure the contact springs 73 and 77 respectively to the plate member 75. Contact springs 73 and 77 each have horizontally extending legs 84 and 85 which extend in overlapping relation as can be best seen in Fig. 2. The contact springs 73 and 77 are inclined upwardly at slightly different angles so that the legs 84 and 85 are spaced from each other when the contact springs are in the open position for the switch 69.

The switch is connected in the circuit by the conductor 72, of power cord 71, which is secured to the spring contact 73 by means of screw 76. The other contact spring 77 is connected to the motor by a conductor (not shown).

To deflect spring contact 77 into engagement with spring contact 73 when the plate member 75 is rotated, a ceramic button 82 is mounted on the inside face of the spring contact 77 in engagement with the field of the motor 14. To limit the clockwise rotation of the plate member 75 around the pivot pins 80, there are a pair of cars 83 formed integrally with plate member 75 and extending outwardly therefrom to engage the casing 15. The plate member 75 is normally biased in a clockwise direction by the spring contact 77 which is in a deflected position when button 82 is in contact with the motor 14 and ears 83 are engaged with the casing 15. Thus the spring contact 77 tends to bias the switch to the open position in which plate member 75 is rotated in the clockwise direction to the full extent of its travel.

When the plate member 75 is pressed inwardly rotating it counterclockwise around its pivotal mounting, the spring contact 77 deflected to a greater extent until the leg 85 of the spring contact 77 is brought into contact with leg 84 of the spring contact 73. This engagement between legs 84 and 85 completes the circuit through motor 14 and energizes the motor.

To the motor 14, the user of the sharpener presses viewed in Fig. 4, that clearance for the knife K is provided when the knife K rests on the knife rest 64 engagement with the bar 23, the knife edge will engage r 6 against theplate 75 which pushes the contact 77 into engagement with the contact 73. The laterally projecting legs or end portions 84 and 85 of the contacts 73 and 77 overlap and engage one another to form the contact portions ,of the switch. Then, when it is desired to tie-energize the motor 14, the user releases the plate 75. The contact 77, being of leaf spring construction, urges the plate 75 back in the clockwise direction, as viewed in Fig. 5, and the ends of spring contacts 73 and 77 separate. Molded feet 89 of known construction are secured by screws to the bottom cover plate 46 and sup port the sharpener in a position elevated above the table top or other surface on which it is used so that cooling air is free to enter the inlet '45 and flow from the outlet 47. I a

The positions of the wheels 10 and 11 tilted toward the back of the housing 15 and upwardly, together with the flat, slightly frustoconical rims of the wheels, insome that the faces 10d and 11d of the wheels contact the edge of the knife being ground. The position of the knife rest 64 relative to the wheels 10 and 11 causes the knife edge to always be contacted by the portions of the grinding wheels 10 and 11 which are moving upwardly against the cutting edge of the knife. By the provision of the projections 19 and 20 and the arcuate plates 17 and 18, the assembly is precisely located and held against movement transversely of the slot 16, and the notches 21 and 22 and the shelves 25 and 26 interlock with one another to precisely locate the grinding wheels 10 and 11 longitudinally of the slot 16. This indexing structure is precise and rugged while being simple and inexpensive in its fabrication and assembly. In addition, the arcuate plates 17 and 18 cooperate with the shelves 25 and 26 and the casing 15 to form a grinding chamber separated from the housing portion. The switch unit including the pivotally mounted actuating plate 75, which also carries the switch contacts 73 and 77 also is simple, effective and inexpensive. This switch unit does not require a separate cover and contact mounting and actuating means, and has a minimum of moving parts.

While there has been shown and described one particular embodiment of the present invention, it Will be apparent to those skilled in the art that various modifications may be made without departing from the invention in its broader aspects, and it is therefore aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the present invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. In a knife sharpener, a pair of cup-shaped grinding wheels, the rim of one of said wheels being adapted to fit partially into the rim of the other of said wheels, a housing having a knife guiding slot extending across the top thereof from front to rear, means mounting said wheels rotatably in said housing generally on opposite sides of said slot in positions in which the lower portion of the rim of said one of said wheels extends into the lower portion of the rim of said other of said wheels, said mounting means mounting said wheels on axes of rotation such that the openings in said cup-shaped wheels open toward the top and back of said housing, the opposed faces of said grinding wheels being conical in shape, one end of said slot defining a knife rest upon which a knife blade may be supported during sharpening, said rest being positioned along a line defined by the intersection of the cones including said conical faces of said grinding wheels, and a stop at the other end of said slot positioned above a line defined by the intersection of two planes each normal to the axis of each grinding wheel and passing through the outermost edge of each grinding wheel.

2. A knife sharpener comprising an electric motor, a frame mounting said electric motor having a pair of spaced end plates extending upwardly therefrom, an in verted cup-shaped housing enclosing said motor, a knife receiving slot in said housing, said end plates abutting said housing on either side of said slot, wall means on said frame cooperating with said end plates and said housing to form .a chamber between said end plates closed except for said slot, a pair of grinding wheels mounted for rotation in said chamber adjacent said slot, drive meansconnecting'said motor and said grinding wheels.

3. A knife sharpener comprising an electric motor, a frame mounting said electric motor having a pair of spaced end plates extending outwardly therefrom, a housing member for said motor engaging said end plates, 21 pair of grinding wheels mounted for rotation between said end plates, drive means connecting said motor and said 15 2,365,1 1

8 grinding wheels, wall means on said frame cooperating with said plates and said housing to form a compartment for said grinding wheels separated from said motor, and a knife receiving slot in said housing providing access to said compartment and said grinding wheels.

References Cited in the file of this patent UNITED STATES PATENTS 1,606,813 Schultz Nov. 16, 1926 1,946,311 7 'Comeau Feb. 6, 1934 2,019,471 Broberg Oct. 29, 1935 2,722,783 ORussa Nov. 8, 1955 2,775,075 McMaster et a1 Dec. 25, 1956 Madl et a1. Dec. 23, 1958

Images