US3781989A

US3781989A - Can opener

Info

Publication number: US3781989A
Application number: US00258594A
Authority: US
Inventors: M Swetlitz; J Richard
Original assignee: Westinghouse Electric Corp
Current assignee: Sunbeam Corp
Priority date: 1972-06-01
Filing date: 1972-06-01
Publication date: 1974-01-01
Anticipated expiration: 1991-01-01
Also published as: CA966646A; ES415427A1; AR198416A1; GB1426232A; JPS4942479A; DE2327137A1; AU5600173A

Abstract

The disclosed device is a power driven can opener in which the outer layer of the end seam of a can is severed. The disclosure is particularly directed to specific critical dimensions and relationships of the parts which yield a commercially practical electrically powered can opener adapted to open most of the cans encountered in normal use in the home.

Description

United States Patent 1 1 1 1 3,781,989

Swetlitz et al. Jan. 1, 1974 [54] CAN OPENER 2,582,504 1/1952 Reed 30 155 x 3,060,566 10/1962 H b' 3O 4 R [751 inventors Swahili James Richard 3,719,991 3/1973 Fiia nci 30/155 both of Monroeville, Pa.

[73] Assignee: Westinghouse Electric Corporation, Primary Examiner0thell M. Simpson P gh, Assistant ExaminerGary L. Smith [22] Filed: June 1, 1972 Attorney-F. H. Henson et a].

21 A I. No.: 258 594 i 1 pp 571 ABSTRACT 52 us. 01. 30/4 R, 30/155 The disclosed device is a Power drive" can Opener 51 1m. B67b 7/38, B67b 7/30 which the Outer layer of the end mm of a can is [58] :Field of Search 30/4 R 8'5 9 15, ered. The disclosure is particularly directed to specific 30/155 critical dimensions and relationships of the parts which yield a commercially practical electrically pow- [56] References Cited ered can opener adapted to open most of the cans en- UNITED STATES PATENTS countered in normal use in the home.

l.999,370 4/1935 Olschewski 30/9 9 Claims, 13 Drawing Figures 14 P J1Il|l|lI|lll;Ill|l|I|D\ 3o 34 F 32/ 48 52 7 2 i 76 I l' 1 11 I I 74 75 l I I6 1 I 32 34 I l PATENIE JAN H974 SHEET 2 0F 4 Ill! PATENTED JAN 1 I974 SHEET 3 [IF 4 PIC-3.8.

CAN OPENER BACKGROUND OF THE INVENTION 1. Field of the Invention The invention pertains to the art of can openers of the type in which the outer layer of a multi-layer end seam of a can is severed by the can opener.

2. Description of the Prior Art Numerous patents on can openers of the type adapted to cut the double seam on an end of the can have issued. Of those known to applicant, the following disclose can openers which are manually powered and in which the outer layer of the end seam of a can is cut: 3,510,941; 3,302,283; 3,094,776; 3,067,510; 2,997,786; 1,360,256. U.S. Pat. Nos. 1,935,680 and 1,684,414 disclose manually powered can openers which include embodiments for cutting the outside layer of the can end seam, and also alternative embodiments for cutting the inside layer. U.S. Pat. No. 3,006,070 discloses an electrically powered can opener in which the outside layer of the can end seam is cut. U.S. Pat. No. 3,206,849 discloses a manually powered can opener in which the end seam is flared outwardly and its inside layer cut, while U.S. Pat. Nos. 3,477,263 and 3,313,023 disclose electrically powered can openers of this type. U.S..Pat. No. 1,537,608 discloses a manually powered can opener in which the side wall of the can is cut immediately below the top end seam of the can. U.S. Pat. Nos. 3,161,952, 3,110,962 and 2,886,887 disclose electrically powered openers of the character adapted to cut the end seams of metal barrels or drums of industrail type.

As far as we know, can opener constructions according to the teachings of the above-identified patents have not been successfulin the home art, or as a practical matter even reasonably available. We believe that the only seam or rim cutting can opener which has been marketed to any extent in the U.S. is one having the construction taught in the U.S. Pat. Nos. 3,313,023 and 3,477,263, and which has a number of objections to it in our view. We are also aware of one hand operated opener, that corresponding to U.S. Pat. No. 3,510,941 which was or is marketed outside of the U.S. at least, but is also considered to be deficient in a number of respects.

From our work in the area from which our invention arose, some of the reasons why outside rim cutting can openers have not been readily available have become apparent, even though it is our belief that a can opener of that character has a number of distinct advantages, such as being more sanitary and safer than the ordinary can opener, as well as permitting reclosure of the opened can. The difficulties which can be expected to be encountered in developing a satisfactory manuallyoperated outside rim cutting can opener are equally applicable, and compounded, when the intent is to develop such a can opener which is electrically powered, and which can be produced at a'cost which permits it to be sold in competition with the conventional electrically powered can opener of the type in which a cutter severs the can lid immediately inside the top rim.

However, in our work leading to the invention, we believe that we have contributed substantially to the solution of a number of the problems that can be expected to be encountered in developing an outside rim cutting can opener adapted to be powered electrically with a reasonable cost motor.

SUMMARY OF THE INVENTION In accordance with our invention, we provide an electrically powered can opener in which the exterior layer of the end seam of the can (hereinafter called the rim of can) is severed to release the can end from the can body by engaging the rim between a rotatable drive wheel and a rotatable cutting wheel. The parts of the can opener essentially comprise a housing including a base adapted to be supported upon a work surface so that the can during opening is supported from the can opener, as distinguished from being directly supported upon a work surface. The drive wheel is beveled and has: a knurled, small diameter inner section adapted to engage the rim top edge; a knurled conical section adapted to engage the inner face of the rim; and a larger diameter outer section. The cutting wheel has a generally frusto-conical shape' having a peripheral cutting edge adapted to engage and cut the outer layer of the rim of a can. Electric motor means rotates the drive wheel when the motor means is energized. Means are provided for shifting the drive wheel toward the cutting wheel to place the wheels in operative cutting relation with the can rim therebetween, and to concurrently energize the motor means. The wheels are disposed relatively to each other to define a space between the cutting edge and said inner periphery in the range of about 0.046 to 0.056 inch. The drive wheel has a pressure angle defined between a plane normal to the axis of the drive wheel and the face of the conical section of about 15. Additionally, the drive wheel and cutter wheel are supported for longitudinal adjustment along their respective axes of rotation. The adjustment is such that with the drive wheel in a position closest to the cutter wheel in the absence of the can rim therebetween, the part of the conical section closest to the drive wheel is spaced from the cutting edge in the range of about 0.013 to 0.020 inch.

A number of other dimensional and spatial relationships are also present in the can opener according to our invention and will be detailed in the descriptive part of this specification.

DRAWING DESCRIPTION FIG. 1 is a vertical sectional view corresponding generally to one taken along the line [-1 of FIG. 2;

FIG. 2 is a partly-broken elevational view of the front face of the can opener, that face being the one to which the can is applied;

FIG. 3 is a partly-broken elevational view of the opposite or back side of the can opener with the housing back removed;

FIG. 4 is an enlarged sectional view of the main part of the operating mechanism;

FIG. 5 is an enlarged sectional view of the rim portion of a can;

FIG. 6 is an enlarged view of the inner face of a can rim, and showing the relationship during cutting of the face of the conical section of the drive wheel to the rim inner face;

FIG. 7 is a top view of the rim of FIG. 6 and showing the relationship of the lower portion of the edge of the conical section to the rim;

FIG. 8 is a sectional view of the cutter wheel;

FIG. 9 is a fragmentary view, partly broken, and enlarged relative to FIG. 8 for the purpose of showing detail of the notches provided on the peripheral cutting edge of the cutter wheel;

FIG. 10 is a face view of a portion of the cutting edge containing a single notch;

FIG. 11 is a top view of the fragment of FIG. 10;

FIG. 12 is an exploded isometric view of the portion of the drive train for the drive wheel through which the drive wheel is shifted to and from driving positions; and

FIG. 13 is a graph showing the relationship between spring washer deflection, the forces resulting therefrom, and how they relate to can rim thickness.

DESCRIPTION or THE PREFERRED EMBODIMENT The general basic structure of the can opener, which also includes a knife sharpener therewith, will first be described in connection with FIGS. 13, with attention thereafter being directed to the numerous details of construction which are considered highly important to a satisfactory can opener of this type.

The shell of the can opener includes a main housing 10 of molded plastic, a front cover 12 and a rear cover 14 of molded plastic, and a metal front plate 16.

The housing 10 includes a base portion 18 adapted to support the can opener upon a work surface such as a kitchen counter top 20. The part of the main housing 10 above the base provides a rectangular frame open on its front and rear, and accommodates most of the internals of the can opener. Referring to FIG. 3 as well as FIG. 1, a rib and boss assembly 22 is provided as an integrally molded part at the top center, and adjacent to each of the bottom corners to provide support for the operating assembly of the can opener as well as to fasten the rear housing 14 to the main housing by means of long screws 24 as seen near the top of FIG. 1.

The rear housing 14 is in the general form of a shell with its inner open face abutting the rear face of the main housing 10, and including a projecting shell 26 which houses a knife sharpener wheel 28 which is not of direct concern in connection with our invention.

The front cover 12 is in the general form of a shell with an open inner face abutting the main housing 10, and having a partly open outer face which accommodates the projection therethrough of a part of the operating mechanism of the can opener.

The front plate 16 is of general rectangular shape in outline and includes a hood portion 30 overlying and encompassing the upper part of the drive wheel of the operating mechanism. The portion of the front plate 16 below the area in which the rim of the can 31 is being cut is inclined outwardly as it descends so that a can being opened with the can opener resting on a level surface does not have its longitudinal axis in a perfectly vertical disposition, but rather is inclined to the degree that the lower part of the front plate engages the sidewall or lower rim of the can.

The internal operating mechanism within the shellformed of the housing parts described is supported at three points from the bosses 22 by means of the same screws 24 which also fasten the rear cover 14 to the main housing 10. The front cover 12 is secured by means of upper and lower screws 32 which pass through the front face of the front cover 12 and into bosses 34 provided on the "cast housing for the internal operating mechanism. The front plate 16 is fastened to the front cover by a pair of hook-like tabs at the upper end of the front plate engaging in slots in the front cover at the hood 30, and by a single screw 36 passing into a boss molded on the front face of the front cover 12.

Referring now to FIGS. 1 to 4, a die cast block 38 is provided from which all of the parts of the operating mechanism are supported. The cast block is itself supported from the shell as described previously. Among the main parts of the operating mechanism are the following. A drive wheel 40 is fixed for rotation upon a shaft 42 which extends horizontally from front to rear through a suitable front bearing 43 in the block 38, then extends through: a cam bearing 44 which is secured to the block; then through a cam 46 which has the operating handle or lever 48 associated therewith; through a series of conical spring washers 50 to a drive gear 52 fixed to the shaft; and then through an adjusting nut 54 and a locking nut 56 on the right end, threaded portion of the shaft 42. As viewed in FIG. 4, the shaft 42 is provided with a circumferential groove 58 to receive a C ring 60 which serves as a backup for a washer and popout spring 62 which bears against the left face of the cam bearing and urges the shaft 42 and attached parts to the left. The drive wheel has an interi- Orly-threaded central bore with right hand self-locking threads which is turned onto the exteriorly-threaded left end of the shaft to secure the parts.

The cutter wheel 64 is of generally truncated conical shape and has a central bore by which the wheel is received upon a fixed, nonrotatable mandrel 66 which has its upper end received in a bore in the casting. A well is machined in the top surface into which a lubricated felt washer 65 is placed to provide necessary lubrication. An enlarged lower end 68 is externally threaded and received in an internally threaded bore in the casting. A thrust washer 70 is interposed between the shoulder on the enlarged portion 68 of the mandrel, and the lower surface of the cutting wheel 64.

Referring now to FIG. 1, the drive train for transmitting the power from the electric motor 72 to effect rotation of the shaft 42 and drive wheel 40 includes a helically shaft 74 anchored in a self aligning bearing 75 and rotatable with the rotor of the motor 72, a spur gear 76 with helical threads driven by the shaft 74 and fixed upon a smaller diameter spur pinion 78 which in turn drives the large spur gear 52 fixed to the shaft 42 carrying the drive wheel 40. The

gears

76 and 78 are rotatable upon the axle 80 which has its one end supported in a bore in the cast block. A top portion of gear 76 is shown cut away to permit a view of the downwardly projecting end of the lever 48, which is also shown in FIG. 12.

Referring to FIG. 3, the cast block also supports a switch housing 82 containing a normally open switch 84 with a rearwardly-projecting, slidable actuating button 86. When the operating handle 48 is depressed (turned counter clockwise as viewed in FIG. 3), to shift the drive wheel shaft and drive wheel in a direction to capture the rim of a can between the pressure wheel and the cutter wheel 64, the button 86 is depressed near the end of the stroke of the operating lever to also energize the drive motor 72.

Referring to FIG. 2, a torque pin 88 adjacent the cutting and drive wheels projects outwardly from its anchor point. The lower side of this pin is at approximately the same level as the lowermost point of the smaller diameter section of the drive whell 40. This pin engages the top edge of the rim of a can being opened and prevents the can from being tilted in a counterclockwise direction about the point where opening of the rim is occurring. In other words, during opening, the torque applied to the can by the drive wheel is counteracted by the pin thereby retaining the can in a vertical position.

A can retainer plate 90 of generally shallow U- shaped configuration is fastened to the cast block as is seen in FIG. 2, with the bight portion of the retainer plate being disposed to underlie the lower exterior edge of the top rim of the can being opened. This retaining plate ordinarily does not function to help support the can being opened, since the top edge of the bight does not engage the rim in normal opening operations. However, in case of large heavy cans the lid having been severed may lift enough to allow the can to break away and drop in which'case it will catch on the top edge of the plate.

The front plate 16 has its exposed face in the plane approximately 5-8 from the vertical so that the can, 31, while being opened, is tilted approximately to that extent, as may be seen in FIG. 1.

Since many of these specifically critical dimensional and spatial relationships of the parts of the can opener of the invention stem from the requirement that most of the normal range of different cans encountered in a household be opened, attention will first be directed to cans in general'and the end seams or rims provided on such cans.

As shown in FIG. 5, the can sidewall 92 is bent over on itself to form a downwardly open hook, and the can top wall 94 is curled up over the bight of the sidewall hook and then curls down over the outside and back up into the hook as illustrated. This rim, or as it is called in the can art a double seam, includes sealing compound between those layers formed from the sidewall and the top wall, to provide an air tight seal. The layer of the rim to be cut by the can opener of the invention is the outer layer 96. The dimensions of the rim of particular interest in connection with this invention are the can rim height indicated by the legend CRH, the can rim thickness indicated by the legend CRT, and the thickness of the can lid material which is also the thickness of the outer layer 96.

In an evaluation of the range of cans normally encountered in the household, it has been concluded that they fall into three general categories. Small cans, with thin rims and of relatively soft steel construction comprise somewhat under percent ofthe market according to our informatiomLarge cans, such" as three pound coffee cans and other large cans which are vacuum packed, have relatively thick rims, are of relatively harder steel, and comprise about l0 percent of the cans encountered. Most of the remaining cans are what we characterize as regular cans, with average thickness rims and of a steel of intermediate hardness. However there is another category comprising beer and soda pop cans, as well as some pet food cans, which have an average rim thickness, but which are made of harder steel than the regular intermediate size cans comprising the average 80-85 percent of the cans encountered.

It is our view that an evaluation of the specific character and dimensions of the various can rims to be cut is of substantial importance in connection with a can opener of the character with which the invention deals since, for satisfactory opening of the can, only the outer layer 96 should be cut. If the cutter wheel penetrates too far beyond the layer, there is a tendency to push the severed edges into a position which locks the top of the can back on. Alternatively, if the penetration is not sufficient, the layer will not be completely severed and it will be impossible for practical purposes for the user of the can opener to remove the lid. The relationship be tween CRT and the force requirements for opening various cans will be described hereinafter in connection with FIG. 13.

Knowledge of the different CRH (can rim heights) of the range of cans encountered is also important in connection with a can opener of the type with which this invention deals, since the cutter wheel must operate against a portion of the outer layer 96 of the rim which is essentially centered on the CRH. In that connection, in a rim type can opener of the character with which the invention deals, the plane of the cutting edge is inclined with respect to a plane which parallels the top of the can. This angular relationship is not in itself something that we have contributed to this art, since such relationships are disclosed in at least four of the prior art US. Pat. Nos. noted; namely 2,997,786, 3,094,776, 3,302,283, and 3,510,941. This relationship is termed a dive angle in at least some of the patents noted, and is considered to be a convenient expression of the relationship and will be used hereinafter to mean that relationship. The dive angle provides an upwardly urging force upon a can during cutting so that the can is not dropped, and also lifts the lid to complete the severing action and break or loosen the seal between the layers. This dive angle will be discussed later in connection with the cutter wheel characteristics.

It has also been found in the study of the cans that the outer layer 96 of the rim frequently has a slight radius therein exaggerated in FIG. 5 so that the outer face of the layers 96 is slightly convex. This convexity has some bearing on the pressure angle of the drive wheel which will be considered in connection with the drive wheel itself.

Returning to FIG. 4, the drive wheel 40 includes an inner diameter section 98 carrying longitudinally extending knurls thereon, a conical section 100 carrying radially extending knurls thereon, and an outer diameter section 102. The angle defined between a plane normal to the axis of the drive wheel, and the face of the conical section is indicated by the numeral 104 in FIG. 4 and is called the pressure angle. The distance between the cutting edge of the cutting wheel 64 and the closest point on the inner diameter section 98 of the drive wheel is termed the Y dimension and is indicated by the numeral 106 in FIG. 4. The distance between the closest point of the cutting edge of cutter wheel 64 and the facing conical section 100 of the drive wheel, when the drive wheel is in its furthermost right position as viewed in FIG. 4, without a can to be cut in place, is indicated by the numeral 108 and is termed the G dimension. Both the Y and G dimensions are critical for proper cutting, and are factory and service adjustments. The sequence and manner in which these adjustments are made will be described after the importance of these particular dimensions relative to other critical factors is explained.

The radial distance between the periphery of the smaller diameter section 98 and the large diameter section 102 of the drive wheel must be sufficient to provide a backup against the inner layer of the rim. This dimension, which we call the DIFF., must not be so great as to prevent the top of the rim from being in good engagement with the longitudinal knurls on the smaller diameter section 98. That would result from the larger section 102 engaging the generally flat surface 94 of the top of the can and obstructing the upward movement of the rim into a position for the cutting operation. The diameters of the

sections

98 and 102, and the pressure angle 104 must also be selected with consideration given to the smallest radius ofa can to be opened, such as a sardine can with corner radii of about inch. In that connection, FIGS. 6 and 7 illustrate the relationship of the conical section 100 to the inner surface of the rim 47, with the direction of rotation of the drive wheel 40 being indicated by the curved arrow while the two arrows at the rim indicate the direction of movement of the rim as the drive wheel is rotating. Both the top and bottom of the bead move at the same rate. However, the knurls 101 on the conical section have an angular velocity so that the outermost end of a knurl moves further in a given unit of time than the inner end of the same knurl. This requires that there be some slippage between knurl and rim, which in turn is a function of the pressure angle, and finally that the radial knurls 101 be properly shaped to prevent the knurls from acting as teeth on a milling machine cutter, which could lead to metal shavings.

In FIG. 7, a line 110 is shown relative to the curved rim 47 of the can, this line corresponding to a line lying in the plane of the ends of the knurls 101 on the conical section. Since the FIG. 7 view corresponds to a plan view, the line 110 is straight. lt illustrates that because of can rim curvature, as the ends of the knurls 101 descend or rises the ends approach the inside surface of the rim. From this it will be appreciated that if a pres sure angle of were provided, the ends of the radial knurls 101 would dig into the inner surface of the rim on any relatively small can. If the pressure angle is increased, of course the line 110 would be spaced farther from the rim 47 shown in FIG. 7.

From the illustrations in FIGS. 6 and 7 then, it would appear to be beneficial to have a relatively large pressure angle. However, the pressure angle also bears upon the ability of the opener to support the weight of whatever can is being opened, as it is being opened and is unsupported directly from any work surface. Additionally, it has been found that if the pressure angle is too large, difficulty is experienced in maintaining the Y" dimension within the proper range. In this connection, it is noted that the Y" dimension to which the opener is initially adjusted is 0.048 inch, with experience indicating that so long as the Y" dimension remains within a range of 0.046 to 0.056 inch, most cans will be satisfactorily cut. The initial setting of the Y dimension toward the smaller end of the range is to compensate for wear-during use.

The currently preferred pressure angle is about If the pressure angle is increased to, say, 25, the effective Y" dimension during cutting will become unstable, with an effective Y" dimension of 0.046 inch or less, the cutter edge is so far above the CRH centerline that there is more tendency for the cutter wheel to slip off the can rim, resulting in the can dropping in some instances. or in failure to completely cut the layer 96. As noted before, if the pressure angle is less than about 15 there is a tendency for the drive wheel to produce excessive shavings from the inside surface of the rim.

In our currently preferred form of can opener, the drive wheel 40 (FIG. 4) has an outer section 102 with a diameter of 0.570 inch, an inner section 98 with a diameter which includes the longitudinally-extending knurls of about 0.410 inch, a pressure angle of 15 plus or minus l/2, with each of the teeth, or knurls, including both the longitudinally extending knurls and the radial knurls being about 10 apart. The knurls are in the range of 0.010 to 0.015 inch deep and are provided with a 45 chamfer at the outer end of the radial knurls, and at the inner end of the longitudinal knurls. The chamfer on the outer end of the radial knurls aids in reducing milling or abrading of the inner wall of the can rim as the drive wheel rotates. To also reduce the chance of abrading, after the knurls are initially formed on the drive wheel, the drive wheel, is placed in an abrading machine where the sharp edges of the teeth are removed so that all of the teeth have ridge extremities with a radius in the range of about 0.002 to 0.006 inch.

The characteristics of the cutter wheel 64 are also important in obtaining a satisfactory cut of the range of cans to be opened. The diameter of the cutting wheel is selected to correlate with the dive angle and with the range of can rims to be cut. The dive angle functions not only to insure that the rim of the can is held up in a position to be cut and driven, but also serves to lift the lid thereby severing the metal. If the lift is enough the elastomeric seal between the layers of the lid and the can body is also broken. Since the exterior layer 96 of the can rim, and the cutting edge of the cutting wheel 64, are intersecting arcs in a cutting operation, the greater the diameter of the cutting edge the greater the length of cutting edge in contact with a given penetration of the cutting edge into the layer 96. As the can rim moves through the cutting location, the dive angle of the cutting edge tends to tilt the can in a direction in which the cutting edge would align itself with the middle of the rim. However, this is prevented by the upper edge of the rim engaging against the lower edge of the torque pin 88 so that the can is essentially level as it would be viewed against the can opener face in FIG. 2. Most of the lift of the lid, to break the elastomeric seal, is accomplished by the portion of the peripheral cutting edge of the cutting wheel 64 in FIG. 2 which is visible to the right of the drive wheel 40, since that is the portion which is trailing the cut.

The currently preferred diameter of the cutting edge of the cutter wheel 64 is about 0.650 inch, and the dive angle which is currently preferred is about 15 to 16. Referring now to FIGS. 811, the cutter wheel has a central bore adapting it to rotate upon the fixed spindle or mandrel 66 (FIG. 4). The shape of the cutter wheel is that of a generally frusto-conical wheel with the cutting edge formed by the corner having an included angle of about 82 between the top face 112 of the wheel adjacent the cutting edge of the wheel, and the circumferential side 114 of the wheel. The angle between a line parallel with the axis of the cutter wheel, and the face 114 depending from the cutter edge is about 18.

FIGS. 9 through 1! illustrate details relating to the cutter edge considered to be relatively important for proper operation of the can opener. The cutting edge is provided with a number of shallow notches equally spaced thereabout as is generally taught in U.S. Pat. No. 3,510,941. The size and spacing of these notches 116 is considered relatively important since they provide the friction required to prevent relative slippage between the cutting edge and the core rim, and also provide proper perforation of the rim. In that connection, while the rim is referred to herein as being severed or cut, it actually is perforated by the cutter wheel and then torn or forced apart on opposite sides of the perforation line. ln the currently preferred arrangement, the notches have a depth as indicated by the dimension carrying the numeral 120 in FlG. 9 of about 0.0025 to 0.0055 inch. The widthofthe notches at the peripheral cutting edge and as indicated by the numeral 122 in FIG. 11 should be in the range of about 0.007 to 0.013 inch. The currently preferred number of notches in the peripheral cutting edge is 48. Thus, with the 0.650 inch diameter of the cuttin'gedge at its extremity, the ratio of the length of the edge portions 118 between the notches, to the width of the notches at the extremity of the periphery, is in a range between 2 to l and to 1.

Another important characteristic of the cutting wheel is that the peripheral cutting edge portions 118 between notches not be unduly sharp, nor too blunt. Therefore, the cutter wheel is subjected to a controlled tumbling or abrading process in which the portions 118 of the cutting edge between the notches are slightly blunted by being given radii in the range of about 0.0005 inch to 0.00l5 inch. This range of radii provides excellent cutting for a can opener according to our invention. Too large a radius would prevent the proper penetration and complete cutting would not occur. Too sharp an edge is subject to breakage and allows the cutter wheel edge to penetrate too deeply and cut into the second layer of metal thus tending to lock the lid back to the can.

The dimensions of depth, width and spacing between the notches set forth herebefore is also important in that if the notches are too deep and too wide, too large a pillar is left between the cuts and the lid can not be lifted by the dive angle of the cutter wheel. If the notches are spaced too far apart, the wheel does not get a sufficient grip on the can rim and accordingly stops turning upon its mandrel. The resulting sliding action between rim and cutting edge will yield metal slivers. The angle of the face 114 of the cutting wheel relative to the rim layer 96 is also important in determining the amount of penetration of the cutting edge. The cutter wheel is of tool steel hardened to about 60-62 Rockwell C hardness and then double tempered at about 390 F to obtain an adequate life of the part.

Part of the mechanism for effecting shifting of the drive wheel 40 toward the cutter wheel 64, and thereby obtaining an engagement of the can rim therebetween is illustrated in FIG. 12. The cam bearing 44 includes a pair of diametrically opposite disposed sloping cam recesses 45 on its face adjacent the operating handle 48. The face of the cam 46 facing the handle 48 includes diametrically opposite cam follower projections 46a which project through accommodating slots 49 in the portion of the handle 48 through which the drive shaft 42 projects. When the handle 48 is pulled down, from a position in which the can follower projections 46a are seated in the cam recesses 45, (that is from a position in which the cam 46 is at its farthermost left position as shown in FIGS. 4 and 12), the cam 46 will be rotated in a clockwise direction, as-viewed in FIG.

12 and cammed to the right. This movement displaces the shaft 42 to the right and accordingly pulls the drive wheel 40 into a position in which the rim of the can is engaged between the drive wheel and cutter wheel. The shaft is forced to the right during this movement by the transmission of force through the conical spring washers 50 which bear against the gear 52 and accordingly the adjusting nut 54 and lock nut 56.

If a can rim is not present in the space between the drive wheel and cutter wheel, the conical washers 50 will simply transmit the force with the degree of deflection of the washers being only that amount necessary to overcome the leftward force of the popout spring 62 (FIG. 4). However, if the rim of a can is between the drive wheel and cutter wheel, the degree of force exerted to displace the shaft to the left will be a function of the deflection of the washers 50, which in turn will be a function of the CRT and resistance to penetration of the peripheral cutting edge into the rim of the can.

FIG. 13 is a graph which relates spring washer 50 deflection to the force exerted upon the can rim for cutting and to the can rim thicknesses of various cans. The graph there presented is based upon an initial penetration of the cutter wheel edge into the rim of about 0.010 inch during shifting of the drive wheel, a gap or G setting of 0.015 to 0.0l8 inch, and the use of a 10 pound popout spring 62. The

major curves

124, 126, 128 assume the use of6 standard conical spring or beveled washers, arranged in series relationship, and being of the type carrying the designation BO-500-025 and available from the Associated Spring Corporation. The other curve 138 assumes the use of four of these washers. The lefthand ordinate carries a scale of total washer deflection in inches. The abscissa is scaled in pounds of force and the right-hand ordinate is scaled in can rim thickness in inches. The blocks adjacent the right-hand ordinate indicating the character of the cans by legends show the range of can rim thicknesses normally encountered in the various sizes type cans. Thus for example it can be seen that a regular can typically has a CRT between about 0.048 and 0.052 inch.

It has been empirically determined that the force required to be exerted to achieve the proper penetration of the cutter wheel on the small cans is in a range of about 25 to 35 pounds. For a regular can, the force range is about 45 to 65 pounds, and for a large can it is about to l 10. Preferably the actual force exerted by the can opener falls in the central part of this range. As an example with respect to small cans, if a force for example of about 15 pounds is exerted, the cut will likely not be complete. If the force exceeds say 40 pounds, the lid may be resealed. The failure to open by being on the low force side is applicable to all of the cans. With respect to the larger cans, if the force exceeds say NO or US pounds, not only will there be possible resealing, but it is also quite possible that the drive motor will stall.

The curve 124 indicates the actual force of the cutting wheel edge upon the can rim with a G setting of the can opener of 0.016 inch. The dash line curves 126 and 128 correspond to the forces on the rim which result from G settings of 0.015 and 0.018 inch, respectively. It will be apparent from these curves that if the G setting is decreased, the actual force applied to the rim increases for a given can and, conversely, if the G setting is increased, the actual force upon the rim of the given can will be decreased. This is understandable since with the smaller G settings, there is increased deflection of the washers with a given can. It is noted that in shifting the drive wheel to the right, the washers must deflect initially sufficiently to equal pounds to overcome the popout spring. This 10 pound popout spring has been factored into the curve (i.e., the curves have been translated accordingly to the left). The generally parallelogram shaped

areas

130, 132, 134 which are hatched along the curve indicate the force versus washer deflection ranges which will generally satisfactorily open cans of the particular size. Thus, small cans having a CRT in the range of 0.040 to 0.42 inch will be satisfactorily opened with washer deflections in the range of about 0.014 to 0.016 inch, giving forces in the range of about 23 to 35 pounds.

To further explain the relationships, regardless of the can to be opened, the drive wheel attempts to shift to the right to a position corresponding to its gap setting. The degree to which this movement is resisted corresponds to the particular CRT. With smaller cans, the drive wheel is able to come closer to the gap setting than with a CRT that is larger. Accordingly, with a thinner CRT the washer deflection is less and, accordingly, the force is less. With a thicker CRT the deflection of the washers is greater and, accordingly, the forces are greater.

The rectangular block 136 indicates the area in which beer and pop cans, and certain pet food cans generally fall and the related force requirements to open these cans. In other words, these cans tend to have a CRT which corresponds generally to regular cans, but the metal is somewhat harder than the metal found in regular cans. Thus greater forces are required to obtain the proper cut than with regular cans. However, this is not considered of much importance with beer cans and pop cans since they are commonly opened in other ways than with an electrical can opener.

While it is our view that using six of the conical washers providing a curve such as 124 shown in FIG. 13 is preferable, if four of these washers are used instead, the curve 138 which passes through the block 136 results. While most cans will be satisfactorily opened with the force versus washer deflection curve a shown in 138, there is a tendency with some of the smaller cans to be resealed because of the excessive force being applied, and a tendency, particularly with some of the larger cans, for the motor to stall.

The motor 72 (FIG. 1) is a conventional shaded pole induction motor of the same general character as has been used previously in electric can openers. We have found that adequate torque is available, when six of the conical spring washers are used, with stator stack height of one inch and a coil is provided with 620 turns. However, if the number of spring washers is reduced to four, the increased force makes it preferable that the G dimension be changed to a range of 0.01 8 to 0.020 inch to reduce the load upon the motor. To compensate for possible reduced line voltages, the stack height may be increased to a range of about 1.14 to 1.25 inches, and with at least 595 turns in the coil.

In operating the can opener generally, the can 31 is held in a position in which the top rim is located between the drive wheel and the cutter wheel. The operating lever 48 is then swung down to move the drive wheel into a position pushing the rim toward the cutting wheel. As the operating handle approaches the lower end of its travel the switch actuation button 86 is engaged and moved downwardly to close the switch which energizes the motor. The handle is held down while the can is driven through at least one full rotation of the can by the operation of the drive wheel, and the outer layer 96 of the can rim is severed and concurrently lifted slightly to break the seal effected by the sealing compound between the layers forming the rim. The can is supported by the can opener during the cutting operation and need not be manually supported additionally. After a complete cut is provided, the can is grasped to support it manually as the lever 48 is raised to release the can rim from the cutting location. The popout spring 62 insures that the drive wheel 40 moves away from the cutting wheel to release the can rim as the operating lever 48 is raised to its top position.

We claim:

1. In a can opener of the type in which the exterior layer ofa can rim is severed to release the can end from the can body, by engaging and moving the can rim between a rotatable drive wheel and a rotatable cutting wheel:

a housing adapted to be supported stationarily during a rim severing operation, said drive wheel and cutting wheel being located adjacent the upper part of the housing;

said drive wheel having an inner cylindrical section of one diameter having knurls on its circumference adapted to engage the top edge ofa can rim during a cutting operation, an outer section of larger diameter than said inner section, and an intermediate conical section having knurls on its face thereof adapted to engage the inner wall of a can rim; said cutting wheel being of generally frusto-conical shape having a peripheral cutting edge adapted to engage and cut the outer layer of said rim; motor means for effecting rotation of said drive wheel when said motor means is energized;

means for shifting said drive wheel toward said cutting wheel to place said wheels in clamping and operative cutting relation with said can rim therebetween, and to energize said motor means upon effecting said clamping;

said wheels being disposed relative to each other to define a space between said cutting edge and the closest point thereto of said inner cylindrical section in the range of 0.046 inch to 0.058 inch; and said drive wheel has a pressure angle defined between a plane normal to the axis of said drive wheel and the face of said conical section of about 15.

2. In a can opener according to claim 1 including:

means supporting said drive wheel for longitudinal adjustment along its axis of rotation;

means supporting said cutting wheel for longitudinal adjustment along its axis of rotation; said drive wheel, when disposed in said operative cutting relation with said cutter wheel, having the closest points of said conical section and said peripheral cutting edge being spaced in a range of about 0.013 inch to 0.020 inch.

3. In a can opener according to claim 1 wherein:

said inner cylindrical section of said drive wheel has a diameter of about 0.4l inch, and said outer section has a diameter of about 0.57 inch so that the radial dimension across the face of said conical section is in the order of about 0.08 inch.

4. In a can opener according to claim 1 wherein: said knurls on said conical section extend generally radially,

and are chamfered at their radially outer ends to eliminate sharp corners thereon.

5. A can opener according to claim 1 wherein: the ridge edges of said knurls on said conical section are blunted to a degree that a radius is provided on said ridges in the range of about 0.002 to 0.006 inch. 6. In a can opener according to claim 1 wherein: said cutter wheel peripheral cutting edge is provided with a number of notches substantially equally spaced therearound; and the portions of said cutting edge between said notches are blunted to a degree that said cutting edge has a radius in the range of about 0.0005 to 0.0015 inch.

7. In a can opener according to claim 6 wherein:

the ratio of the length of the portions of said cutting edge between said notches to the width of said notches at said peripheral cutting edge is in the range of5 to l to 2 to l.

8. In a can opener according to claim 7 wherein:

said cutter wheel has a diameter at said cutting edge of about 0.65 inch.

9. In a can opener according to claim 8 wherein:

said notches are in the range of about 0.0025 inch to 0.0055 inch deep as measured from the extremity of said cutting edge.

Claims

1. In a can opener of the type in which the exterior layer of a can rim is severed to release the can end from the can body, by engaging and moving the can rim between a rotatable drive wheel and a rotatable cutting wheel: a housing adapted to be supported stationarily during a rim severing operation, said drive wheel and cutting wheel being located adjacent the upper part of the housing; said drive wheel having an inner cylindrical section of one diameter having knurls on its circumference adapted to engage the top edge of a can rim during a cutting operation, an outer section of larger diameter than said inner section, and an intermediate conical section having knurls on its face thereof adapted to engage the inner wall of a can rim; said cutting wheel being of generally frusto-conical shape having a peripheral cutting edge adapted to engage and cut the outer layer of said rim; motor means for effecting rotation of said drive wheel when said motor means is energized; means for shifting said drive wheel toward said cutting wheel to place said wheels in clamping and operative cutting relation with said can rim therebetween, and to energize said motor means upon effecting said clamping; said wheels being disposed relative to each other to define a space between said cutting edge and the closest point thereto of said inner cylindrical section in the range of 0.046 inch to 0.058 inch; and said drive wheel has a pressure angle defined between a plane normal to the axis of said drive wheel and the face of said conical section of about 15*.

2. In a can opener according to claim 1 including: means supporting said drive wheel for longitudinal adjustment along its axis of rotation; means supporting said cutting wheel for longitudinal adjustment along its axis of rotation; said drive wheel, when disposed in said operative cutting relation with said cutter wheel, having the closest points of said conical section and said peripheral cutting edge being spaced in a range of about 0.013 inch to 0.020 inch.

3. In a can opener according to claim 1 wherein: said inner cylindrical section of said drive wheel has a diameter of about 0.41 inch, and said outer section has a diameter of about 0.57 inch so that the radial dimension across the face of said conical section is in the order of about 0.08 inch.

4. In a can opener according to claim 1 wherein: said knurls on said conical section extend generally radially, and are chamfered at their radially outer ends to eliminate sharp corners thereon.

5. A can opener according to claim 1 wherein: the ridge edges of said knurls on said conical section are blunted to a degree that a radius is provided on said ridges in the range of about 0.002 to 0.006 inch.

6. In a can opener according to claim 1 wherein: said cutter wheel peripheral cutting edge is provided with a number of notches substantially equally spaced therearound; and the portions of said cutting edge between said notches are blunted to a degree that said cutting edge has a radius in the range of about 0.0005 to 0.0015 inch.

7. In a can opener according to claim 6 wherein: the ratio of the length of the portions of said cutting edge between said notches to the width of said notches at said peripheral cutting edge is in the range of 5 to 1 to 2 to 1.

8. In a can opener according to claim 7 wherein: said cutter wheel has a diameter at said cutting edge of about 0.65 inch.

9. In a can opener according to claim 8 wherein: said notches are in the range of about 0.0025 inch to 0.0055 inch deep as measured from the extremity of said cutting edge.