US3768163A

US3768163A - Grass trimmer sharpening device

Info

Publication number: US3768163A
Application number: US00228564A
Authority: US
Inventors: E Weber; G Sesta
Original assignee: Black and Decker Manufacturing Co
Current assignee: Black and Decker Corp
Priority date: 1972-02-23
Filing date: 1972-02-23
Publication date: 1973-10-30
Anticipated expiration: 1990-10-30
Also published as: JPS4894992A; FR2173524A5; DE2308506A1; CA947083A; GB1353312A

Abstract

A portable, powered grass or hedge trimmer or the like comprising a housing enclosing a motor and having a handle and trigger means disposed thereon. A plurality of relatively movable blades are provided, and at least one blade is driven by the motor. The blades include cooperable teeth adapted to cut grass or the like. A novel sharpening device is provided and includes a body or sheath provided with abrasive stones adapted to sharpen the teeth of at least one blade when the motor is energized and the blades moved relative to one another. The sheath, when in place, can also protect one or more of the blades and thereby helps prevent accidental injury when the device is not in use.

Description

ilnited States Patent Weber et al.

GRASS TRIMMER SHARPENING DEVICE Inventors: Edwin]. Weber, Baltimore; Gerald J. Sesta, Glenarm, both of Md.

Black and Decker Manufacturing Company, Towson, Md.

Filed: Feb. 23, 1972 Appl. No.: 228,564

Assignee:

9/1931 Bennettetal .51/211 RX 12/1943 Wisterman et al 30/138 X 2,895,268 7/1959 Martinmaas, .lr. 5l/250 Primary Examiner-Donald G. Kelly Assistant Examiner-Howard N. Goldberg Att0rney-Leonard Bloom et al.

[57] ABSTRACT A portable, powered grass or hedge trimmer or the like comprising a housing enclosing a motor and having a handle and trigger means disposed thereon. A plurality of relatively movable blades are provided, and at least one blade is driven by the motor. The blades include cooperable teeth adapted to cut grass or the like. A novel sharpening device is provided and includes a body or sheath provided with abrasive stones adapted to sharpen the teeth of at least one blade when the motor is energized and the blades moved relative to one another. The sheath, when in place, can also protect one or more of the blades and thereby helps prevent accidental injurywhen the device is not in use. i

7 Claims, 8 Drawing Figures GRASS TRIMMER SHARPENING DEVICE SUMMARY OF THE INVENTION The present invention is directed to a novel sharpening device for a portable cutting or trimming unit of the type having relatively movable, toothed blades and to a novel method of in place sharpening of one or more blades of this type of unit. This device includes a sheath or body provided with abrasive means engageable with cutting teeth on at least one of the blades of the unit. Sharpening is effected simply by relatively moving the blades, as by turning the unit on, with the sheath in place, and requires no disassembly of the blades from the unit. Sharpening is, therefore, carried out simply and quickly and, since no direct handling of the blades is required, is performed very safely. Furthermore, the sharpening device can be constructed to protectively encompass one or more blades when in place thereon to reduce the likelihood of injury to one handling the unit, or to the blades themselves, while the unit is not in use.

Main-objects, therefore, of the present invention are to provide a novel sharpening device and method for one or more toothed blades of a portable,- powered, cutter or trimmer unit or the like, which device is adapted for quick, easy, and safe use, and which does not require disassembly of the blade or blades from the unit for sharpening.

Further important objects of the present invention are to provide a toothed blade sharpening device of the above character which can also serve as a storage and safety device to protect one or more of the blades from being damaged, or from injuring one handling the unit, when not in use.

Additional important objects are to provide a novel blade sharpening device of the above character which is relatively inexpensive to manufacture, durable in construction, and reliable in use. i

Other important objects to the present invention will become more apparent from a consideration of the detailed description to follow taken in conjunction with the drawings annexed hereto.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view-illustrating-a portable, power driven grass trimmer and a blade sharpening device therefor embodying the present invention;

FIG. 2 is an enlarged plan view of the blades and the sharpening device of FIG. 1 and showing the parts in position for blade sharpening; I

FIG. 3 is a plan view of the sharpening device of FIGS. 1 and 2;

FIG. 4 is a sectional view of FIG. 3 taken lines 4-4 thereof;

FIG. 5 is a sectional view of FIG. 2 taken along the lines 55 thereof;

FIG. 6 is an enlarged sectional view of a portion of FIG. 3 taken along the lines 66 thereof;

FIG. 7 is a perspective view illustrating one modified form of the invention as used with a different type of cutter or trimmer unit; and

FIG. 8 is a sectional view of FIG. 7 taken along the lines 8-8 thereof.

BROAD STATEMENT OF THE INVENTION Broadly described, the present invention relates to a sharpener for a cutting blade assembly including relaalong the tively movable toothed cutting blades, said sharpener comprising a body, said body including means detachably securing said body to one of said blades, spaced abrasive means on said body fitting between the teeth of said one blade and rubbingly engaging the teeth of the other of said blades when said body is detachably secured to said one blade, said abrasive means functioning to sharpen the teeth of said other blade when it is moved relatively to said one blade.

In another aspect, the present invention relates to a sharpener for a portable power operated cutter of the type having at least two relatively movable toothed cutting blades, said sharpener comprising a body having a blade receiving recess therein, said body having upstanding side walls including a tapered portion adapted to grippingly engage one of said cutting blades when the latter are in position in said recess, a plurality of abrasive stones fixed in said recess and adapted to interfit between the teeth of said one cutting blade, said stones adapted to engage the underside of the teeth of the other of said cutting blades and sharpen the latter when the blades are moved relative to each other, said side walls of said body being shaped to allow manual insertion and removal of said blades to and from said body recess. I In still another aspect, the present invention relates to a sharpener for a cutting bladeassembly of a portable grass trimmer or the like of the type including a housing having a handle, a motor in said housing and having an output shaft, stationary toothed blade means fixed to said housing, movable toothed blade means driven by said output shaft and cooperable with said stationary blade means, said sharpener comprising a body, means on said body releasably engageable with said stationary blade means to releasably secure said body thereto, a pluiality of abrasive stones fixed to said body and extending between the teeth of said stationary blade means and engaging the teeth of said movable blade-means when said body is releasably engaged with said stationary blade means, the teeth of said movable blade rubbingly engaging said abrasive stones when said body is engaged with said stationary blade means and said motor is energized and said movable blade means driven by said output shaft, whereby said movable blade means is sharpened.

In still another aspect, thepresent invention relates to a sharpener for a cutting blade assembly of a portable trimmer or the like of the type including a housing having a handle, a motor in said housing, a stationary blade fixed to said housing and having spaced teeth thereon, amovable blade operatively engaged with said motor and having spaced teeth thereon, said stationary blade teeth and said movableblade teeth having cooperatively engageable shearing .edges thereon, said sharpener comprising a body including means grippingly engageable with said stationary blade, spaced abrasive means on said body fitting between the teeth of said stationary blade and rubbingly engaging the teeth of said movable blade when said body is grippingly engaged with said stationary blade, said abrasive means functioning to sharpen the shearing edges of the teeth of said movable blade when it is driven by said motor.

DETAILED DESCRIPTION Referring now more specifically to the drawings, a portable, power operated grass trimmer, one type of unit with which the present invention finds particular use, is illustrated generally at 11 in FIG. 1 and is seen to include a clam shell housing 1-3 having a motor portion 15, a transmission portion 17 and a handle '19. An electric motor (not shown) is disclosed within the motor portion 15 and may be powered from a suitable electric source connected thereto by a line cord (not shown). Alternatively, the motor may be powered by electric storage battery means suitably located within the housing 13. A switch trigger 21, disposed within the handle 19, turns the motor on and off. A safety lock assembly 23 interlocked with the trigger 21, is provided atop the handle .19 to prevent accidental actuation of the motor.

It will be understood that the particular blade means of cutting or trimming units of the general category with which the present invention finds use is not limited -to that illustrated herein and described below. Thus,

the blade means may include: one or more stationary blades together with one or more movable blades; a plurality of blades all of which move;.or movingblades which oscillate, rotate, reciprocate, or a variation thereof. In addition, the description of toothed cutting blades to follow refers generally to blades having cooperable shearing edges disposed non-parallel or nonconcentric to the path of relative blade movement. Furthermore, the terms cutting (cutter) or trimming (trimmer) unit refer to devices of this general type used to cut grass, shrubs-or foilage, or a variety of other similar or related materials.

Withthis in mind, the illustrated trimmer is, provided with a pair of

grass cutting blades

24,25 which extend forwardly from the housing portion 17. The bottom blade 24 is fixed to the housing-13 and is provided .with a plurality of spaced, generally forwardly extending teeth 27. The upper blade 25, on the other hand, is pivoted to the fixed blade 24 by means of a rivet. 29, and also has a plurality of forwardly extending, spaced teeth 31. The blade 25 is oscillated about the pivot 29 by means offthe motor (not shown) disposed within the housingportion .15 by, for example, an orbiting eccentric driven by the motor and disposedwithin an elongated slot (not shown) in the rearward, concealedportion of the blade 25. Such constructions are relatively common and well known in the art and need not be explained further here. i I

Desirably, the stationary blade 24 is somewhat wider than the oscillating blade 25'and has one more tooth than the blade 25. In addition, the stroke ofthe oscillating blade 25 is 'such that cutting edges 33 on each tooth 31 cooperates with cutting edges 35 on each of two adjacent teeth 27 on the stationary blade 24, while not extending laterally past the confines of the blade 24. Thus, cutting

edges

33, 35 cooperate with 'one another during relative movement to cut grass or other material disposed therebetween.

In order for the

blades

24, 25 to cut properly, their

edges

35, 33 must be maintained relatively sharp. In addition, in the case of battery powered devices, blade sharpness controls cutting efficiency of the unit anddirectly affects the life of the batteries. In practice, it has been found that in two-bladed shears such as that illustrated herein, this can best be achieved by utilizing blades of different hardness, namely, one relatively hard, permanently sharpened blade, and one of somewhat less hardness. Blades of the same or nearly the same hardness tend to wear excessively, especially where the blades are held in scissor-like engagement. Thus, if the dulled blades cannot be resharpened, they must be replaced.

Specifically, then, the stationary blade 24 desirably is constructed from arelatively hard and wear resistant material, such as heat treated steel, and its edges'35 are initially sharpened at a suitable angle, for example perperidicular to the plane of the blade 24 The moving blade 25, on the other hand, is constructed from, for example, a heat treated steel which is softer'than the material of the blade 24. The edges 33 of blade 25 are also initially sharpened at a suitable, forexample, an acute angle; however, as a result of thesofter nature of the material of the blade 25, the edges 33 require periodic sharpening during use in order to maximize the cutting efficiency of the device. Proper sharpening of these blades, however, can be difiicult and often requires a professional to perform it properly; Quite often, it also is necessary to remove one or both blades from units of this type in order to perform this sharpening. This is undesirable for obvious reasons which include expenditure of time and money to maintain the tool 11 in optimum'operating condition.

In accordance with the present invention, the edges 33 of blade 25 are quickly and easily sharpened by the user without-requiring anyspecial skill or tools and without requiring-any disassembly of the blade from the unit. Thesharpener assembly of the present invention comprises a plastic body 41 having a hollow recess 43 formed therein. The body 41 is preferably constructed from astitf, non-warping, slightly flexible plastic material, such as .those sold.-under the trademarks .ABS, Nylon or Lexan. The recess 43 is shaped somewhat complementary to ,the outside contour of the blade 24 and is adapted to snugly receive the blade therein. Preferably. the-body 41 defines overhanging lips' 45, 47 which overlay the outer edges of the blade 24 at least at an area adjacent the tool housing 17. Thus, when inserting the blade 24 into the recess 43, the blade s outer edges snap? under

theoverhanging jlips

45, 47, to thereby retain the blade 24 in place within the recess 43. ;When it is desiredto remove the body 41 from the blade 24, the body 41 simply is pried away from the blade 24, 'and. the flexible nature of the material of the body 41. allows

thelips

45, 47 to deflect outwardly to thereby release the blade 24. In addition, the body 41 may have

recesses

46, 48 to receive the end of the outer teeth '27 on the blade 24 to help retain to the

blades

24, 25 in place on the body .41.

A plurality of abrasive sharpening members, for example, abrasive stones are disposed within the recess 43 in the body 41 and are suitably disposed so that when the stationary blade 24 is positioned in the recess 43 and the tool ll-turned on, the blade 25 is sharpened. The stones 51 are positioned to fit between the teeth 27 of the stationary blade 24 and protrude slightly upwardly thereof. The teeth 31 of the moving blade 25 are normally disposed in rubbing contact with the teeth 27 of the stationary blade 24 so that when the blade 24 is positioned within the recess 43, the teeth 31 of the moving blade 25 resiliently engage the abrasive stones 51. Thus, with the parts so positioned, the cutting edges 33 ofthe teeth 31 rub against the stones 51 when the tool 11 is turned on.

By way of example, the stones 51 can be constructed of an aluminum oxide vitreous material having a coarseness of approximately grit. With this material, and utilizing a heat treated steel for the movable blade 25, the stone crystals break away as the blade teeth 31 rub thereagainst. This results in sharp edges on the stones 51 being continuously presented to the blade edges 33.

The stones 51 are secured in place within the body recess 43 in any suitable manner. For example, the body 41 may be provided with molded in recesses 53 and the stones 51 secured in place within the recesses 53 by a suitable rubber based cement or a melting type glue.

A modified form of the invention is shown in FIGS. 7 and 8. Here, the tool with which the sharpening device is used as a power operated hedge trimmer and having an elongated stationary blade or comb 101 and a reciprocating blade 103. The comb 101 has laterally extending, spaced teeth 105 disposed on one or both sides thereof. The reciprocating blade, conventionally operated by a rotating crank (not shown) driven by an electric motor (not shown) is provided with corresponding laterally extending, longitudinally spaced treading teeth 107 on one or both sides thereof. A cover plate 109 is disposed atop the reciprocating blade 103 and, together with the stationary blade 101, sandwiches the reciprocating blade 103 therebetween. Hedge trimmer construction of this type, whether driven by a corded electric motor or a cordless electric motor are well known in the art and need not be explained further here. However, for a detailed explanation thereof, reference may be made to the US. Pat. to Wells, No. 3,564,714 and the U.S. Pat. to Riley, No. 3,161,954, both of which are owned by the assignee hereof.

A sharpener device for sharpening the cutting edges of the teeth 107 of the reciprocating blade 103 is illustrated generally at 111 in 'FIGS. 7 and 8 and is seen to include a resilient sheath 113 adapted to releasably grip the underside of the stationary blade 101 and the top of the blade cover plate 107. The resilient holder 113 is provided with one 'or more abrasive stones 115 adapted, when the holder 113 is in place as shown in FlGS. 7 and 8, to fit between adjacent ones of the teeth 105 of the stationary comb 101. When so positioned, the abrasive stones 115 rubbingly engage the underside of the cutting teeth 107 of the blade 103, so that these teeth 107 may be sharpened simply by turning the device on and reciprocating the blade 103 with the resilient holder 113 in place.

By the foregoing, there has been disclosed a novel sharpening device calculated to fulfill the inventive objects hereinabove set forth, and while preferred embodiments of the present invention has been illustrated and described in detail, various additions, substitutions, modifications, and omissions may be made thereto without departure from the spirit of the invention.

We claim:

1. A sharpener for a cutting blade assembly including relatively movable toothed cutting blades, said sharpener comprising a body, said body including means detachably securing said body to one of said blades, spaced abrasive means on said body fitting between the teeth of said one blade and rubbingly engaging the teeth of the other of said blades when said body is detachably secured to said one blade, said abrasive means functioning to sharpen the teeth of said other blade when it is moved relatively to said one blade.

2. A sharpener for a portable power operated cutter of the type having at least two relatively movable toothed cutting blades,'said sharpener comprising a body having a blade receiving recess therein, said body having upstanding side walls including a tapered por tion adapted to grippingly engage one of said cutting blades when the latter are in position in said recess, a plurality of abrasive stones fixed in said recess and adapted to interfit between the teeth of said one cutting blade, said stones adapted to engage the underside of the teeth of the other of said cutting blades and sharpen the latter when the blades are moved relative to each other, said side walls of said body being shaped to allow manual insertion and removal of said blades to and from said body recess.

3. A sharpener as defined in claim 2 wherein said side wall tapered portions are defiectable to releasably receive said one cutting blade.

4. A sharpener as defined in claim 2 wherein said body recess has a depth, defined by said side walls, greater than the combined thickness of said blades, whereby said sharpener body effectively protects said blades. 1

5. A sharpener for a cutting blade assembly of a portable grass trimmer or the like of the type including a housing having a handle, a motor in said housing and having an output shaft, stationary toothed blade means fixed to said housing, movable toothed blade means driven by said output shaft and cooperable with said stationary blade means, said sharpener comprising a body, means on said body releasably engageable with said stationary blade means to releasably secure said body thereto, a plurality of abrasive stones fixed to said body and extending between the teeth of said stationary blade means and engaging the teeth of said movable blade means when said body is releasably engaged with said stationary blade means, the teeth of said movable balde rubbingly engaging said abrasive stones when said body is engaged with said stationary blade means and said motor is energized and said movable blade means driven by said output shaft, whereby said movable blade means is sharpened.

6. The improvement of claim 5 wherein said body includes a recess shaped to receive said stationary blade means, means in said recess for grippingly engaging said stationary blade means, said abrasive stones being positioned in said recess.

7. A sharpener for a cutting blade assembly of a portable trimmer or the like of the type including a housing having a handle, a motor in said housing, a stationary blade fixed to said housing and having spaced teeth thereon, a movable blade operatively engaged with said motor and having spaced teeth thereon, said stationary blade teeth and said movable blade teeth having cooperatively engageable shearing edges thereon, said sharpener comprising a body including means grippingly engageable with said stationary blade, spaced abrasive means on said body fitting between the teeth of said stationary blade and rubbingly engaging the teeth of said movable blade when said body is grippingly engaged with said stationary blade, said abrasive means functioning to sharpen the shearing edges of the teeth of said movable blade when it is driven by said

Claims

2. A sharpener for a portable power operated cutter of the type having at least two relatively movable toothed cutting blades, said sharpener comprising a body having a blade receiving recess therein, said body having upstanding side walls including a tapered portion adapted to grippingly engage one of said cutting blades when the latter are in position in said recess, a plurality of abrasive stones fixed in said recess and adapted to interfit between the teeth of said one cutting blade, said stones adapted to engage the underside of the teeth of the other of said cutting blades and sharpen the latter when the blades are moved relative to each other, said side walls of said body being shaped to allow manual insertion and removal of said blades to and from said body recess.

3. A sharpener as defined in claim 2 wherein said side wall tapered portions are deflectable to releasably receive said one cutting blade.

4. A sharpener as defined in claim 2 wherein said body recess has a depth, defined by said side walls, greater than the combined thickness of said blades, whereby said sharpener body effectively protects said blades.

5. A sharpener for a cutting blade assembly of a portable grass trimmer or the like of the type including a housing having a handle, a motor in said housing and having an output shaft, stationary toothed blade means fixed to said housing, movable toothed blade means driven by said output shaft and cooperable with said stationary blade means, said sharpener comprising a body, means on said body releasably engageable with said stationary blade means to releasably secure said body thereto, a plurality of abrasive stones fixed to said body and extending between the teeth of said stationary Blade means and engaging the teeth of said movable blade means when said body is releasably engaged with said stationary blade means, the teeth of said movable blade rubbingly engaging said abrasive stones when said body is engaged with said stationary blade means and said motor is energized and said movable blade means driven by said output shaft, whereby said movable blade means is sharpened.

7. A sharpener for a cutting blade assembly of a portable trimmer or the like of the type including a housing having a handle, a motor in said housing, a stationary blade fixed to said housing and having spaced teeth thereon, a movable blade operatively engaged with said motor and having spaced teeth thereon, said stationary blade teeth and said movable blade teeth having cooperatively engageable shearing edges thereon, said sharpener comprising a body including means grippingly engageable with said stationary blade, spaced abrasive means on said body fitting between the teeth of said stationary blade and rubbingly engaging the teeth of said movable blade when said body is grippingly engaged with said stationary blade, said abrasive means functioning to sharpen the shearing edges of the teeth of said movable blade when it is driven by said motor.