GB1578906A - Apparatus for cutting vegetation - Google Patents

Description

(54) APPARATUS FOR CUTTING VEGETATION (71) WE, WEED EATER, INC., a corporation organized and existing under the laws of the State of Delaware, United States of America of 10515 Harwin Drive, Houston, Texas 77036, United States of America do hereby declare the invention, for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to apparatus for cutting vegetation, and more particularly relates to improved apparatus for cutting vegetation with a flexible non-metallic cord member.

It is well known to cut or mow grass, weeds and other vegetation with a moving flail-like member, and it is now well known to employ a flexible non-metallic cord member for the purpose of cutting vegetation located in places which are inaccessible to apparatus employing a rigid steel blade.

In particular, the trimmer which is marketed in various forms under the trademark WEED EATER, and which is described in U.S. Patents No. 3,708,967; No. 3,826,068; and No. 3,859,776; is now widely known and used for this purpose.

According to the invention there is provided apparatus for cutting vegetation comprising: a length of non-metallic flexible cord; rotatable support means for revolving said cord in a cutting plane; an electric motor for rotating said support means; and a full wave rectifier electrically connected between said motor and an A.C. mains input.

The apparatus preferably includes a casing extending around said motor, a hollow handle extending from said casing, an electric switch located adjacent the free end of the handle and an electric lead extending through said hollow handle and connecting said switch with said rectifier.

More preferably it includes a casing portion extending obliquely from said motor and tapering towards an end region defining a connection for said handle, said rectifier being located in said tapering casing portion.

Preferably the handle includes coupling means whereby one portion of said handle may be rotated about the handle axis in increments with respect to the other.

Preferably said coupling means comprises a first tubular member telescopically inserted in a second tubular member, interengageable formations whereby rotational alignment of said first member may be fixed in relation to said second member in any of a plurality of alignments; said formations being disengageable upon telescopic movement of said first member with respect to said second, and resilient means biased against said telescopic movement for maintaining inter-engagement in any one of said plurality of alignments.

Further preferred features will be found set out in the appended claims.

Embodiments of the invention are hereafter described with reference to the accompanying drawings, in which: Figure 1 is a pictorial view showing a first embodiment of a cutting apparatus; Figure 2 is a pictorial side view, partly in cross-section, of the apparatus depicted in Figure 1, wherein the mechanical features and configuration of the apparatus are set forth in greater detail.

Figure 3 is an exploded assembly drawing of one embodiment of the head and spool assembly useful in the apparatus of Figures 1 and 23.

Figure 4 is a cross-sectional view of the head assembly depicted in Figure 3 in a static or nonrotating position showing the cutting cord mounted therein.

Figure 5 is a bottom view of the spool depicted in Figure 3.

Figure 6 is a top view of the spool depicted in Figure 3.

Figure 7 is a bottom view of the head depicted in Figure 3.

Figure 8 is a top view of the head depicted in Figure 3.

Figure 9 is a side view of the vaned head of Figure 8 in a static or nonrotating position.

Figure 10 is a partial side view representation of one embodiment of a cutting cord aperture.

Figure 11 is a similar partial side view representation of another embodiment of a cutting cord aperture.

Figure 12 is an alternate three windowed embodiment of the apparatus depicted in Figure 7.

Figure 13 is an alternate three windowed embodiment of the apparatus depicted in Figure 8.

Figure 14 is a partial view showing the portable apparatus of Figure 1 being used to cut grass or weeds in the upright level position.

Figure 15 is a similar partial view showing the apparatus of Figure 1 being used to cut in the perpendicular or sideways position.

Figure 16 is a partial cross-sectional view of the handle of the apparatus of Figures 1 and 23 showing the attitude-adjusting mechanism for positioning of the cutting head as shown for example in Figures 14 and 15.

Figure 17 is a cross-sectional view taken along line 17-17 of Figure 16 showing the attitude-adjusting mechanism of the handle of the apparatus.

Figures 18 and 19 are partial side views of the housing of the apparatus of Figure 2 and showing details of a knife assembly for the manual cutting of the cord.

Figure 20 is a partial front view of the knife assembly of Figure 19 and taken along the line 20-20 thereof.

Figure 21 is a bottom view of the housing of the device depicted in Figure 2 and showing the details of the second knife member for automatically cutting the line member when the device is in operation.

Figure 22 is a partial isometric view of the details of the automatic knife cutting member depicted in Figures 2 and 21.

Figure 23 is a pictorial side view, partly in cross-section, of another embodiment of the apparatus wherein the mechanical features and configuration of the apparatus are set forth in detail.

Figure 24 is a top plan view of the head member depicted in Figure 23.

Figure 25 is a bottom plan view of the head member depicted in Figure 24.

Figure 26 is a cross-sectional view of the head assembly depicted in Figure 23 in a static oi nonrotating position showing the cutting cord mounted therein.

Figure 27 is an exploded assembly drawing of the head assembly of Figure 26.

Figure 28 is a top plan view of the spool depicted in Figure 27.

Figure 29 is a side plan view of the spool depicted in Figure 27.

Figure 30 is a cross-sectional side view of the spool depicted in Figure 27 and taken along line 30-30 of Figure 29.

Figure 31 is a bottom plan view of the spool depicted in Figure 27.

Figure 32 is a top plan view representation of the unitary bearing element illus trated in ure27.

Figure 33 is a pictorial side view, partly in cross-section, of yet another embodiment of the cutting apparatus, wherein the mechanical features and configuration of the apparatus are set forth in detail.

Figure 34 is an exploded assembly drawing of one embodiment of the head and spool assembly in Figure 33.

Figure 35 is a top view of the head depicted in Figure 34.

Figure 36 ts a bottom view of the head depicted in Figure 34.

Figure 37 is a cross-sectional view of the head assembly depicted in Figure 34 in a static or nonrotating position showing the cutting cord mounted therein.

Figure 38 is a bottom view of the insert depicted in Figure 34.

Figure 39 is a bottom view of the locking clip depicted in Figure 34.

Figure 40 is a top view of the spool depicted in Figure 34.

Figure 41 is a bottom view of the spool depicted in Figure 34.

Figure 42 is a side cross-sectional view of the spool depicted in Figure 34.

Figure 43 is an exploded assembly drawing of an alternate embodiment of the head and spool assembly depicted in Figure 34.

Figure 44 is a top view of the head depicted in Figure 43.

Figure 45 is a bottom view of the head depicted in Figure 43.

Figure 46 is a top view of the spool depicted in Figure 43.

Figure 47 is a bottom view of the spool depicted in Figure 43.

Figure 48 is a cross-sectional view of the alternate head assembly depicted in Figure 43 in a static or nonrotating position showing the cutting cord mounted therein.

Figure 49 is a bottom view of the insert depicted in Figure 43.

Although Figures 23 and 33 do not show the presence of a full wave rectifyer, such a rectifyer, as shown at 21 in Figure 2, should be assumed to be fitted in each embodiment.

Referring now to Figures 1-2, a portable type mowing and edging device generally designated by the numeral 2 is shown, and which is of the type preferred for lighter tasks in residential-size plots or areas, where electrical power is immediately and conveniently available to the operator. Accordingly, the apparatus may be composed of a two-piece adjustable tubular member 4 and 6 having a casing 8 containing electric motor 10 mounted at one end, which motor drives a cord cutting head 42. The handle 6 is removably attached to and supports casing 8 by screws 15 insertable in shank 14. Such a device 2 is portable and is hand held and manipulated by an operator by means of trigger handle 16 and intermediate handle 18. Handle 16 is attached to tubular member 4 by screws 25, whereas handle 18 is attached to tubular member 4 by an easily adjustable wing-nut assembly 27. Power may be applied to the motor 10 through a conventional electrical cord 20, having an appropriate plug at one end (not shown), and having its other end passed through the tubular members 4 and 6 for connection with the motor 10 by means of connectors 17 and 19 at contacts of a full-wave bridge rectifier 21. An appropriate ON-OFF switch or trigger 22 may conveniently be located adjacent the handle 16 at the upper end of the tubular member 4, for interconnection with the conductor 20 and motor 10. The cutting plane of the cutting string 26 may be easily arranged in either a horizontal or vertical position (Figures 14 and 15) or tilted to any angle, to cut along sidewalks, around trees and rocks, and along fences and the like, where it is either unsafe or difficult to cut with conventional apparatus, merely by turning and manipulating handles 16 and 18. Additionally, an attitude adjustment mechanism 98 may be provided to enable tube member 6 to telescopically, rotatably and incrementally lock with respect to tube member 4, wherein an operator may adjust the attitude of the cutting head in relation to the ground, as will be described in more detail hereafter with regard to Figures 16 and 17.

Referring more particularly to Figure 2, there may be seen a larger and more detailed pictorial representation of the apparatus depicted more generally in Figure 1. More particularly, the apparatus or vegetation cutter 2 depicted therein may be seen to include a hollow casing 8 or the like, with a single cord circular cutting head 42 which is rotated by the shaft 36 of an electrical motor 10 of suitable design mounted within casing 8. Casing 8 in the embodiment of Figures 1 and 2 also carries a manually operable knife 7 for cutting cord 26 to length prior to operation of the device. This cutting knife 7 will be described in more detail hereinafter with reference to Figures 18-20.

The cutting head 42 may be further seen to include cutting strand 26 extending laterally from the cutting head 42 through either aperture 60 or 62 (Figure 3) of suitable configuration, a distance which is a function of the present invention as will hereinafter be explained. As further indicated, the casing may have an oval or tear-dropped shaped interference guard or shield member 30 which in the embodiment of Figures 1 and 2 mounts at one end thereof a stationary cutting blade 37 described in more detail hereinafter with reference to Figures 21 and 22. The interference member prevents the cutting head 42 from being brought into injurious contact with a wall or tree during its rotation by motor 10.

When the motor 10 is inactivated and the rotary head 42 is in a static condition, the cutting cord 26 will tend to flexibly dangle from one of the equally spaced-apart apertures 60 and 62 (Figure 3) to the extent permitted by inherent characteristics of cord 26. When the cutting head 42 is rotated at normal operating velocities, however, the cord 26 will tend to stand out rigidly (but will yield when cutting) from the peripher of the cutting head 42 as indicated in Figures 1-2.

As will hereinafter be explained in greater detail, a spool containing surplus cord is removably insertable into cutting head 42, and held in place by glide ball 32. In addition to securing the spool in place, glide ball 32 allows the device to be operated, if desired, without having to be continually and solely supported by an operator. The device 2 may be rested and propelled forward on the glide ball 32 when in operation if this type of cutting is found to be desirable. Generally the unit is supported by the operator at handles 16 and 18.

The electric motor 10 operates in an optimum manner when the air around it is allowed to be circulated or otherwise cooled. The hollow casing 8 effectively allows air to freely circulate around motor 10, therefore providing forced air circulation. The plurality of upstanding fins 28 located on the top of cutting head 42 and extending radially outward from the axis thereof provide forced circulation of air about motor 10 when motor 10 rotates head 42. Rapid rotation of head 42, and hence of fins 28, causes said fins to create a low pressure zone within casing 8, whereby air is drawn from the atmosphere through either openings 34 in lower tubular member 6 or through slots 35 in shank 14, and passed through shank 14, casing 8, and around the motor 10, and expelled through the space 38 between shield 30 and cutting head 42.

This circulation of air sufficientlv cools motor 10 to provide maximum efficiency and minimal ambient temperature rise.

Moreover the openings 34 and slots 35 are sufficiently removed from the cutting area that cut grass or other debris flung up by cord 26 is not likely to enter openings 34 and slots 35 along with the air.

The cutting cord 26 may be composed of a variety of suitable materials as, for example, an elastoplastic extrusion which has been stretched to align the molecules axially. An example of such line is a nylon monofilament of the type commonly used for fishing line. However, other lines may be used, as for example, yarn, cord, rope, twine, braided line, or monofilament, whether described as elastoplastic, elastomeric, natural fiber, or synthetic fiber, and whether compounded of several materials.

Referring now to Figures 3-9, it may be seen that the lower end of the drive shaft 36 from motor 10 is arranged for threading engagement with a drive adapter or attachment member 36A. Drive adapter 36A extends downwardly through head 42 and is arranged at its lower extremity for threading arrangement with glide ball 32. Drive adapter 36A inserts tightly into head 42 and retains its relationship with head 42 by means of its hexagonal head 40 which is insertable into head 42. Rotation of drive adapter 36A by drive shaft 36 causes head 42 to rotate, thereby extending the cord 26 to perform a cutting function.

Glide ball 32, in addition to engaging drive adapter 36A and securing said drive adapter 36A in relationship with head 42 so as to provide axial rotation thereof, also releasably secures spool 44 within head 42 as shown in Figure 4. Spool 44 contains spare cutting cord 46 therein, which is arranged for paying out at predetermined times and at predetermined lengths to vary the effective working length of the cutting line 26. Removal of glide ball 32 by unthreading from drive adapter 36A allows removal of spool 44 so that a fresh full spool may be reinserted into head 42, or alternatively spool 44 may be rewound with new replacement cord, or the like. The external circumference of glide ball 32 may be provided with equally spaced-apart vertical lineal protrusions 33 to insure a better grip for easier removal. Holes 64 and 66 as seen in Figures 7 and 8 are provided in head 42 so that after glide ball 32 is removed from drive adapter 36A, spool 44 may be more easily removed from head 42 by pressing manually with a finger or other object through the holes 64 and 66 to thereby force the spool 44 to disengage from head 42.

Spool 44 as seen in Figures 3, 5, and 6 is composed of a bottom wall 48 and a top wall 50 spaced a predetermined distance by annular hub 52. Interior of hub 52 is an aperture 54 in wall 48 through which drive adapter 36A passes when threaded into glide ball 32. The spool top wall 50 has insert knobs or ridge members 56 and 58 which correspond to and insert into window apertures 60 and 62 in head 42 when spool 44 is placed within head 42. Knobs 56 and 58 position spool 44 and close or seal off the bottom of window apertures 60 and 62, whereby the cutting line 26 is effectively prevented from being deflected vertically as will hereinafter be more fully explained.

The spool bottom wall 48 is provided with cylindrical alignment protuberance tabs 68 and 70 extending downwardly therefrom.

When the spool 44 is placed within head 42, the tabs 68 and 70 harmoniously insert into corresponding cylindrical depressions or detents 72 and 74 in head 42 as seen in Figure 7, thereby positioning and further securing spool 44 therein for rotation along with head assembly 42.

Referring now to Figures 12 and 13, there may be seen a top and bottom view of another embodiment of the present invention. In particular, the depicted head 80 may be seen to be generally similar to the head 42 illustrated in Figures 3, 7, 8, and 9. The principal difference, however, may be seen to be the fact that, in the head 42 previously described, the head is preferably provided with two window apertures 60 and 62 wherefrom a cutting cord may protrude.

The head depicted in Figures 12 and 13, however, is preferably provided with three window apertures 102, 104, and 106 equally spaced-apart around the circumference of head 80, from either of which a cutting cord may be extended. It can readily be seen that use of the three-window aperture head 80 requires modification of spool 44. More particularly, use of head 80 requires that three insert knobs 56, 57 anci 58, be located on spool top wall 50 as illustrated for example in Figure 21, so that the three knobs may correspond to and insert into window apertures 102, 104 and 106. In addition, the spool bottom wall 48 is modified to provide three cylindrical alignment protrusions extending therefrom, similar to the protrusions 68 and 70 of Figure 6 hereinbefore described which protrusions harmoniously insert into the corresponding cylindrical depressions 82,84 and 86 of Figure 12.

It may be clearly seen in Figures 3-4, that in one embodiment a single cord 26 extends from the body of the cutting head 42, and through one of the two window apertures 60 and 62. In the embodiment therein depicted, one end of the cord 26 is inserted through aperture 55 in the spool hub 52, and then knotted together to prevent disengagement therefrom. The line 26 is then preferably wound about the spool 44, oppositely of the direction of rotation of spool 44 and head 42, and then extended through one of respective window apertures 60 and 62, as hereinbefore stated.

The cord 26 may be unwound and paid out from the spool 44 without removing the spool 44 from the head 42, by drawing it from one of respective window apertures 60 and 62 and simply pulling down on the cord 26 to the next window aperture. This movement of cord 26 from aperture to aperture is made possible by virtue of the fact that the top wall 50 of the spool 44 is stiff but resilient. It is to be noted, that a spool modified as hereinbefore described for use with the embodiment of the cutting head depicted in Figures 12 and 13, may be similarly wound and unwound with cutting cord.

In an alternate embodiment of the present invention, a pair of cutting cords 26 may be provided but no additional structure is required to provide this dual cutting cord feature. For example, and in light of Figures 3 and 4, the empty spool 44 is wound as above. However, in the dual cutting cord embodiment, the cord 26 is first doubled along its length thereby providing two free ends. That portion of the line that is doubled is inserted through aperture 55 and knotted as above. The doubled cord is then wound onto the spool until the two free travelling ends are reached. Each free end of the cord 26 is then extended through one of the respective window apertures 60 and 62, thus providing a head assembly 42 including a pair of cutting cords 26. To extend either of the cords, it is then merely required to pull down on the cord as seen in Figure 4 until that cord reaches the next window aperture.

Since wall 50 is resilient, the cord can be pulled along the space defined by wall 50 and the inner periphery of head 42 until it reaches the next window aperture. The other cord may be extended or paid out in similar fashion. While two cutting cords may similarly be provided in the three exit head arrangement depicted in Figures 12, 13 and 21, use of plural cords is not considered altogether desirable in this particular embodiment since no two of the exit window apertures 102, 104 and 106, are diametrically opposed one to the other. The use of three cutting cords, however, in this particular embodiment is contemplated, although a single cord 26 has been found to be entirely sufficient for the majority of purposes to which this apparatus is put to use in vegetation cutting operations.

Referring now to Figure 3, the two window apertures 60 and 62 are each composed of a pair of curvilinear and spaced apart sidewalls 61 and 61A. In this embodiment of the present invention, the cutting cord 26 is composed of a coiled portion 46 (Figure 4) wound about the spool 44, and a free travelling end portion extending along a tangent thereto outwardly through one of the respective window apertures 60 and 62.

Accordingly, the line tends to abut the trailing one of the pair of sidewalls 61 and 61A composing the respective one of the two windows 60 and 62, rather than the sidewall which leads the line as it is carried arcuately about by rotation of the cutting head 42.

It has been found beneficial to provide these trailing sidewalls with metallic bearing element inserts 76 and 78 preferably formed of a material which has a reduced tendency to develop friction from engagement with the vibrating cutting cord, and further preferably having a smooth or polished surface for carrying the cutting cord. These inserts 76 and 78 may be formed by a variety of different materials which are suitable for such purposes, but it has been found that a polished metal such as brass or stainless steel is especially suitable.

Referring now to Figures 10 and 11, it may be seen that the windows 60 and 62 of Figure 3 may be altered in design so as to provide bulbous shaped apertures 88 or 90 as shown, or any other similarly shaped aperture. Rapid revolution of head 42 will force cutting line 26 into constricted portions 92 or 94, thereby reducing the up and down deflection of the cutting cord 26 in the vicinity of the windows 88 or 90 as hereinbefore discussed. Furthermore, the bearing inserts 76 and 78 (Figure 3) as hereinbefore described may be suitably shaped and inserted into the bulbous windows 88 or 90. It is to be noted that the alternate embodiment of the head 80 depicted in Figures 12, 13 and 21, may likewise employ bulbous window configurations 88 or 90 disclosed herein.

Referring now to Figures 14 and 15, two positions or attitudes for operating the device 2 are depicted. Figure 14 shows a partial view of device 2 being operated in a horizontal position with the cutting path described by cutting cord 26 being essentially parallel to the ground. The lower portion of the handle 6 is shown supporting casing 8 by means of shank 14. Cutting head 42 is shown with cutting cord 26 extending therefrom. In actual practice, much of the grass or weeds to be cut will be close to the ground, and therefore the device 2 will have to be tilted slightly to cause the cutting cord 26 to cut. In this regard, glide ball 32 may be used to allow the unit to "ride" the ground as the cutting operation takes place, and the convex outer lower shape of the glide ball 32 enables an operator to conveniently tilt the unit 2 to any desired angle.

Referring more particularly to Figure 15, the unit 2 depicted in Figure 14 is shown in the alternate vertical attitude. The device 2 may be used in this attitude to trim areas otherwise not accessible, trim in a straight line by "trenching" a grass plot in the con ventional manner, or the like.

Proper manual manipulation of handles 16 and ] 8 (Fig. 2) of apparatus 2 may result in either a horizontal or vertical cutting attitude as hereinbefore described and depicted in Figures 14 and 15. However, attitude adjusting means 98 as shown in Figure 16 may be incorporated between upper and lower tubular members 4 and 6, respectively, to facilitate attitude adjustment by allowing tubular members 4 and 6 to be axially rotated and telescopically arranged with respect to each other in increments of 90.

Referring more particularly to Figures 16 and 17, upper tubular member 4 is shown terminating at its lower end 108 in a tubular insert 110 suitably permanently affixed thereto. Inserts 110 and 114 are axially aligned, and insert 110 extends beyond member 4 and inserts snugly but slidably into insert 114. Near the lower extremity of slidable insert 110 and affixed thereto are two protruding knobs 116 and 116A, rectangular in cross-section, and releasably retained by slots 118A-D, whereby insert 110 may be rotated axially within insert 114. Spring 120 is axially aligned and contained within tubular member 6 between insert 110 and washer 122. Washer 122 retains spring 120 in place, and is itself retained in position by a crimp 124 in the circumference of tubular member 6. Electrical lead 20 may be seen extending substantially through the center of aperture 126 in washer 122, and further through the axial center of spring 120, then through the axial centers of inserts 110 and 114, and finally through the axial centers of tubular members 4 and 6. Thus, it will be apparent that downward pressure in the axial direction on upper tubular member 4 and hence on insert 110, sufficient to overcome the upward bias exerted by spring 120, will cause tubular members 4 and 6 to converge and telescope until annular surfaces 130 and 132 contact.

Knobs 116 and 11 6A will then be forced downwardly sufficiently to be disengaged from slots 11 8A and 118C. In this compressed mode, tubular members 4 and 6 may be axially rotated in opposite directions sufficient to rotate knobs 116 and 11 6A 90" within member 6 and align them with slots 11 8B and 118D. Removal of the downward pressure will cause spring 120 to force insert 110 and member 4 upward again and to slide knobs 116 and 116A into slots 118B and 11 8D. In this manner, tubular member 4 may be rotated in 90" increments with respect to tubular member 6, thereby enabling an operator to choose between a horizontal (Figure 14) or vertical (Figure 15) cutting attitude while retaining handles 16 and 18 in the same convenient easy to hold position shown in Figures 1-2.

With reference again to Figures 12 and 13, a further feature of the present invention includes means whereby the three exit head embodiment may be balanced rotationally so as not to transmit unwanted vibrations to the motor shaft 36. Thus, to provide a smooth running and rotationally balanced head assembly 80, it is necessary to offset the weight attributable to the cord 26 extending outwardly of one of window apertures 102, 104, 106. If, for example, as depicted in Figure 12, a single cutting cord passes outwardly of the periphery of head 80 via aperture 102, the mass of the peripherally extending portion of the cord 26 will unbalance the head 80 in a rotational sense. Thus, the head at point 102 will include a mass that is not offset by a corresponding mass at a location diametrically opposite point 102. To overcome this deficiency, and with reference to Figure 13, there will be seen three balancing ribs 102A, 104A, and 106A. Each balancing rib is located diametrically opposite its corresponding window aperture. Thus, for example, balancing rib 1 04A balances window aperture 104. When the head 80 is assembled for grass cutting operation and includes therein a full spool of cord 26, the cord is inserted into one of apertures 102, 104, 106. The cord extends outwardly of one of these apertures and acts as a flail to cut vegetation. Normally, a five to six inch length of cord 26 is used for cutting operations. However, as noted above, it is this section of cord that causes head 80 to rotate in an otherwise unbalanced condition. It is therefore the function of the balancing ribs to offset this mass of the five or six inch flail. This is accomplished by constructing the balancing ribs of an amount of material equal in weight to the mass of thc extended flail section of cord 26. This weight of the balancing rib will vary from unit to unit depending, of course, upon variable factors such as cord diameter, cord density, length of the flail portion of the cord, and the particular materials of construction of the head 80, cutting cord 26 respect to the axis of rotation of the head or housing member 80. As illustrated in Figure 13, the space between walls 200 and 202 is otherwise open. It should be noted, that the two exit head embodiment of Figures 7 and 8 is likewise of double-walled construction as hereinbefore explained with reference to Figures 12 and 13.

Referring now to Figures 18-20, and more particularly to Figure 18, there is therein depicted an embodiment of the present invention featuring a manually operated knife assembly or cutting mechanism 7 which functions to cut the cord 26 to approximately the desired length prior to the startup of a vegetation cutting operation. Thus, the knife assembly 7 is attached and carried by housing 8 and is located thereon at a position above the head member 42 and vertically spaced above the cutting plane. The knife assembly is positioned a predetermined distance above the cutting plane so that operation of the knife 7 to pre-cut cord 26 results in a cord length of approximately 5-6 inches. Thus, the function of knife assembly 7 is to enable the operator to cut the line 26 to approximately its desired effective cutting length prior to the grass cutting operation. The cord 26 will be cut to the exact length desired by the automatic knife assembly 37 during actual operation of the device, which will be described hereinafter with reference to Figure 21 and 22.

Referring now to Figure 20, the knife assembly 7 will be seen to comprise a air of spaced-apart and parallel mounting flanges 23 and 24, fixed to housing 8 or molded integrally therewith. Pivotally mounted within flanges 23 and 24 is a movable pressure block 29 carried by pins 41 and 43. As seen in Figures 18 and 19, the pins 41 and 43 provide for pivoted movement of the pressure block 29 towards and away from housing 8. Thus, in Figure 18, the pressure block 29 is moved away from housing 8 to receive the section of the cord 26 to be cut, while in Figure 19, the pressure block 29 is shown in its position after the cutting of cord 26 to a predetermined length has been completed.

As seen in Figure 18, housing 8 carries a stationary knife blade 45 which is preferably of metal and which is of rigid construction and including a durable and sharp cutting surface. Housing 8 includes a beaded slot 47 for mounting the blade 45, with slot 47 being constructed such that blade 45 may be removed therefrom for purposes of replacing therein a fresh blade element. Thus, blade 45 will become dulled over a period of use and beaded slot 47 provides for the ready replacement thereof.

Referring again to Figure 20, pressure block 29 includes an aperture 49 therein, and a force plate member 51. When it is desired to trim cord 26 to a predetermined length prior to beginning a vegetation cutting operation with the device of the present invention, the terminal end of cord 26 is brought upwardly towards assembly 7 and inserted into and through aperture 49. This places the line member 26 between the blade 45 and the force plate 51. Adjustment of the amount of line pulled upwardly through aperture 49 will obviously determine the length which will be trimmed off and hence the length of cord 26 remaining after the line trimming operation. Once positioned as above between blade 45 and force plate 51, it is simply necessary to manually push pressure block 29 towards housing 8. Hence, force plate 51 forces line 26 against blade 45 and the cord is thereby cut as seen, for example in Figure 19, with the free cut end portion 26A falling to the ground. The pre-cut section of line 26B is then removed from cutting assembly 7 with the result that the unit may then be used to cut vegetation in the fashion hereinbefore described. For the sake of convenience, the pressure block 29 may be provided with a slanted lower wall 53 to easily accommodate grasping thereof by a thumb and forefinger, for example, in order to lift the block 29 away from the housing 8. It will therefore be apparent that assembly 7, as above described, provides a convenient mechanism for the operator of the device of the present invention to pre-trim the cord 26 to size, and eliminates the necessity of the operator of the device to carry upon his person some type of knife or cutting mechanism.

With reference now to Figures 21 and 22, there is therein illustrated and depicted a stationary and automatic cutting assembly 37 for trimming cord 26 to size as the head member 42 rotates. Thus, as shown in Figure 22, interference shield member 30 carries at its underside cutting blade or knife element 71 having a sharp metal cutting surface 71A. Carried integrally with member 30, is a knife mounting assembly indicated by the numerals 81, 81B and 91. The mounting assembly for the knife 71 includes and is seen to comprise, a single downwardly extending and solid wall section 81B having an upper bead portion 91 and a lower bead portion 81. Each of the beads includes therein slots 81A and 91A for removably receiving the blade 71. Thus, it will be apparent that when blade 71 becomes dulled after extended use, it may be easily replaced with a fresh blade by first removing the blade 71 from mounting wall section 81B, by sliding blade 71 out from slots ilA and 91A. The new blade is then inserted in slots 81A and 91A and pushed along the slots until the surface 71A is in alignment with the outer edges of beads 81 and 91 as is clearly depicted in Figure 22. It should be noted that the blade 71 is supported and braced all along its rearward surface by wall portion 81 B, only a portion of which is shown exposed in Figure 22.

It will be readily apparent, therefore, with the knife 71 mounted as described above, that the cutting surface 71A lies in a plane perpendicular to the path of travel of the cord 26. Thus, as seen in Figure 21, the line 26 is rotated by head member 42 in a path which must cross the blade surface 71A. As cord 26 is so rotated, it is automatically trimmed to its desired length 26B with the excess portion 26A falling by the wayside. If it is desired to cut vegetation with a cord 26B of a length of 5.0 inches for example, it is simply necessary in the construction of this unit to space knife 71 five inches from the outer periphery of the head member 42.

Thereafter, a five inch cord length 26B will be maintained automatically and regardless of the fact that the cord is six inches in length prior to start-up of the apparatus. It is therefore contemplated, that the operator of the device will initially pay out about seven or eight inches of cord 26 from head member 42 prior to the initiation of any vegetation cutting operation. The operator may then re-cut the cord 26 to about six inches wit the knife assembly depicted in Figures 18-20. Thereupon, and afterwards, the blade assembly 37 of Figures 21 and 22 will automatically cut the cord 26 to the exact length 26B desired, which according to the preferred mode of operation disclosed herein is about 5.3 inches. Hence, it will be seen that the dual knife assembly of Figures 18-22 provides a simple and convenient system for cutting the cord 26 to its desired and effective working length and without the necessity of manually measuring the length thereof.

In a preferred embodiment of the present invention, it has been determined that an effective length-to-diameter ratio for a nylon monofilament cord 26 or the like, will often be about 35:1 and may be as high as about 82:1 for present purposes. It has further been found that the best cutting line for the purposes of this invention are extruded nylon line, having a diameter of about 0.060 inches to about 0.125 inches, with 0.065 to 0.080 inches being preferred.

The normal rotating speed will be on the order of 6000-7500 RPM, with 6800-7000 RPM being preferably during normal use of the equipment of Figure 1.

Referring now to the embodiment of Figure 23, a portable type edging and trimming device generally designated by the numeral 2 is shown, and which is of the type preferred for lighter tasks e.g. in residential-size plots where electrical power is immediately and conveniently available to the operator.

Accordingly, the apparatus may be composed of a tubular member 4 having a casing 8 containing electric motor 10 mounted at one end, which motor drives a cord cutting head 42. The tubular member 4 is removably attached to and supports casing 8 by screws 15 insertable in shank 14. Such a device 2 is portable and is hand held and manipulated by an operator by means of trigger handle 16. Handle 16 is fixedly attached to the tubular member 4 by means of screws indicated generally at 25. Power may be applied to the motor 10 through a conventional electrical-type insulated cord or conductor 20, having an appropriate plug at one end (not shown), and having its other end passed through the tubular member 4 for connection with the motor 10 by means of connector 17. An appropriate ON-OFF switch or trigger 22 may conveniently be located adjacent the handle 16 at the upper end of the tubular member 4, for interconnection with the conductor 20 and motor 10. The cutting plane of the cutting cord 26 may be easily arranged in either a horizontal or vertical position or tilted to any angle, to cut along sidewalks, around trees and rocks, and along fences and the like, where it is either unsafe or difficult to cut with conventional apparatus, merely by turning and manipulating handle 16. Referring more particularly to Figure 23, there may be seen a hollow casing 8 or the like, with a single cord circular cutting head 42 which is rotated by shaft 36 of electrical motor 10 of suitable design mounted within casing 8.

The cutting head 42 may be further seen to include cutting cord 26 extending laterally from the cutting head 42 through either aperture 60 or 62 (Figure 25) of suitable configuration, a distance which is a function of the present invention as will hereinafter be explained. As further indicated, the casing may have a flange portion or shield 30 for preventing the cutting head 42 from being brought into injurious contact with a wall or tree during its rotation by motor 10.

Referring now to Figure 26, it may be seen that the lower end of the drive shaft 36 from motor 10 is arranged for threading engagement with a drive adapter or attachment member 36A. Drive adapter 36A extends downwardly through head 42 and is arranged at its upper extremity for threading arrangement with shaft 36. Drive adapter 36A inserts tightly into head 42 and retains its relationship with head 42 by means of head 40 which is carried within head 42. Rotation of drive adapter 36A by drive shaft 36 causes head 42 to rotate, thereby extending the cord 26 to perform a cutting function.

Tab element 32, in addition to housing drive adapter 36A and securing said drive adapter 36A in relationship with head 42 so as to provide axial rotation thereof, also releasably secures spool 44 within head 42 as shown in Figure 27. Spool 44 contains spare cutting cord 26 therein, which is arranged for paying out at predetermined times and at predetermined lengths to vary the effective working length of the cutting line 26. Unlocking of tab element 32 by unthreading it from keyway slots 21 allows removal of spool 44 so that a fresh full spool may be inserted into head 42, or spool 44 may be rewound with replacement cord.

Spool 44 as seen in Figures 27-31 is composed of a bottom wall 48 and a top wall 50 spaced a predetermined distance by hub 52.

Interior of hub 52 is an aperture 54 which accommodates keyway elements 21 to fit over tab element 32 and lock spool 44 to head 42 when the spool 44 is placed within head 42. Thus, it will be apparent from Figure 27, that tab element 32 includes a pair of ears 32A and 32B. Each of ears 32A and 32B are spaced above the wall 19 of head 42. Spool member 44 includes keyway elements 21 and 21A each of which is carried by the hub 52 of the spool 44 and formed integrally therewith. Each keyway will be seen to comprise a pair of inwardly extending flange elements 64 and 66 which define therebetween an open ended slot 68. It should be apparent that when spool 44 is inserted into head member 42, that the slot 68 will be positioned to encompass one of ears 32A-B. As seen in Figure 28, the top wall 50 of spool 44 includes a radially extending member 56 which may be grasped manually by the thumb and forefinger.

Turning of member 56 thereby rotates the spool 44 within head member 42 so as to cause the slots 68 of keyways 21 and 21A to engage and thereby lock with respect to each of the ears 32A-B of tab element 32.

This provision of tab 32 and keyways 21 and 21A provides an easy and convenient manner by which spool 44 may be placed within and locked for rotation along with head member 42. To remove the spool 44 from head member 42, it is merely required to turn member 56 in the opposite direction whereby slots 68 of the keyways are unlocked from the respective ears of the tab member 32.

With reference again to Figure 27, a guard element is therein depicted which is of circular configuration and of a diameter to fit snugly over the spool walls 48 and 50 and to rest therebetween. The guard element includes an aperture or cut-out portion through which the terminal end of cord 26 passes. This guard member 70 functions to thereby prevent the remaining coiled portion of the cord 26 on spool 44 from unravelling when the spool 44 is removed from head member 42. In addition, it is contemplated to size the cut-out portion 72 of guard 70 such that the amount of material removed will be substantially equal to the mass of the flail section of line member 26.

This removal of an equal amount of mass of material from guard element 70 provides for balancing of the unit when rotating. Thus, the mass of the extended cord 26 at one side of the head unit will be offset by that portion of the mass removed to provide the cut-out portion 72.

Referring now to Figures 25-27 the two window apertures 60 and 62 are each composed of a pair of curvilinear and spaced apart solid sidewalls 61 and 61A. In this embodiment of the present invention, the cutting cord 26 is composed of a coiled portion wound about the spool 44, and a free travelling end portion extending along a tangent thereto outwardly through one of the respective window apertures 60 and 62.

Accordingly, the cord tends to abut the trailing one of the pair of sidewalls 61 and 61A composing the respective one of the two windows 60 and 62, rather than the sidewall which leads the cords as it is carried arcuately about by rotation of the cutting head 42.

The cutting cord 26 tends to vibrate longitudinally as the cutting head 42 is rotated, and thus to oscillate laterally against the trailing sidewall of one of the windows 60 and 62 in a manner to generate sufficient localized heat to at least partially melt the cutting cord at a point along its length where it contacts the said trailing sidewall. The tear-drop portions 74 and 74A minimize such rubbing to some extent by tending to hold the cord immobile at these points, but such holding effort as may be exerted by the tear-drop portions 74 and 74A must of necessity be limited so as not to restrict the ease whereby new lengths of the cutting cord may be paid out as desired.

It has been found beneficial, therefore, to provide these trailing sidewalls with metallic bearing element inserts 76 and 78 preferably formed of a unitary piece of material which has a reduced tendency to develop friction from engagement with the vibrating cutting cord, and further preferably having a smooth or polished surface for carrying the cutting cord. These inserts 76 and 78 may be formed in one piece of a variety of different materials which are suitable for such purposes, but it has been found that a polished metal such as brass or stainless steel is especially suitable. The bearing element will be seen to include an apertured wall 58 connecting inserts 76 and 78. The aperture 58A is sized to pass over tab element 32 and rest flush with wall 19 of head element 42 so as not to interfere with the locking mechanism 21 and 21A.

With reference again to Figure 27, a further feature of the present invention includes means whereby the head may be balanced rotationally so as to not transmit unwanted vibrations to the motor shaft 36.

Thus, to provide a smooth running and rotationally balanced head assembly 42, it is necessary to offset the weight attributable to the cord 26 extending outwardly of one of window apertures 60 and 62. If, for example, as depicted in Figure 26, a single cutting cord passes outwardly of the periphery of head 42 via aperture 62, the mass of the peripherally extending portion of the cord 26 will unbalance the head 42 in a rotational sense. Thus, the head at point 62 will include a mass that is not offset by a corresponding mass at a location diametrically opposite point 62. To overcome this deficiency, and with reference to Figure 27, there will be seen guard 70 with cut-out 72.

When the head 42 is assembled for grass cutting operation and includes therein a full spool of cord 26, the cord is inserted into one of apertures 60 and 62. The cord extends outwardly of one of these apertures and acts as a flail to cut vegetation. Normally, a three inch length of cord 26 is used for cutting operations. However, as noted above, it is this three inch section of cord that causes head 42 to rotate in an unbalanced condition. It is therefore the function of the cut-out 72 to offset this mass of the three inch flail. This is accomplished by constructing the cut-out portion 72 to be of an amount of material equal in weight to the mass of the extended three inch flail section of cord 26. This weight of the removed cutout portion 72 will vary from unit to unit depending, of course, upon variable factors such as cord diameter, cord density, length of the flail portion of the cord, and the particular materials of construction of the head 42, cutting cord 26, and guard member 70.

Sufficient to say, however, that the guard 70 includes a cut-out 72 of a mass equal or substantially equal to the mass of the extended cutting flail portion of cord 26.

In the Figures 23-32 embodiment of the present invention, it has been determined that an effective length-to-diameter ratio for a nylon monofilament cord will often be greater than 20:1 and is preferably about 35:1 for present purposes. It has further been found that the best cutting cord for the purposes of this invention are extruded nylon cord, having a diameter of about 0.060 inches to about 0.125 inches, with 0.065 inches being preferred. The normal rotating speed will be on the order of 10,000-14,000 RPM, with 12,000 RPM being preferable during normal use of the equipment. It has been determined further that for this Figure 23 32 embodiment disclosed herein, the optimum parameters call for a cutting length of about 2.3 inches being preferred. A head diameter of about 3.4 inches is desirable, thus providing a cutting path of about 8.0 inches, although cutting heads of substantially larger or smaller diameters are contemplated herein.

Referring now to the embodiment of Figure 33, a portable type mowing and edging device generally designated by the numeral 2 is shown, and which is of the type preferred for lighter tasks in residential-size plots or areas, and the like, where electrical power is immediately and conveniently available to the operator. Accordingly, the apparatus may be composed of a tubular member 4 having a casing 8 containing electric motor 10 mounted at one end, which motor drives a string cutting head 42. The tubular member 4 is removably attached to and supports casing 8 by screws 15 insertable in shank 14. Such a device 2 is portable and is hand held and manipulated by an operator by means of trigger handle 16 and intermediate handle 18. Handle 16 is attached to tubular member 4 by screws 25, whereas handle 18 is attached to tubular member 4 by an easily adjustable wing-nut assembly 27. Power may be applied to the motor 10 through a conventional electricaltype insulated cord or conductor 20, having an appropriate plug at one end (not shown), and having its other end passed through the tubular member 4 for connection with the motor 10. An appropriate ON-OFF switch or trigger 22 may conveniently be located adjacent the handle 16 at the upper end of the tubular member 4, for interconnection with the conductor 20 and motor 10. The cutting plane of the cutting cord 26 may be easily arranged in either a horizontal or vertical position or tilted to any angle, to cut along sidewalks, around trees and rocks, and along fences and the like, where it is either unsafe or difficult to cut with conventional apparatus, merely by turning and manipulating handles 16 and 18.

The single cord circular cutting head 42 is rotated by the shaft 36 of the electrical motor 10 mounted within casing 8. The cutting head may further be seen to include cutting cord 26 extending laterally from the cutting head 42 through either aperture 60 or 62 (Figure 34) of the suitable configuration, a distance which is a function of the present invention as will hereinafter be explained. As further indicated the casing may have a circular flange portion or interference member 30 for preventing the cutting head 42 from being brought into injurious contact with a wall or tree during its rotation by motor 10. Shield member 30 may have a cutting blade 21 suspended therefrom perpendicular to the cutting path by means of holder 23 at the extremity of shield 30 furthest from head 42. Cutting blade 21 acts as a cord length adjuster by automatically trimming off excess cord lengths when the head 42 is rotated sufficiently rapidly to cause cord 26 to stand out rigidly from the cutting head 42 and pass across the cutting blade 21. An additional cord trimming blade 23A is located on the outside front portion of casing 8 and includes a hinged cord trimmer lever 25.

This trimming blade 23A may be used to trim cord for any reason while the device 2 is not in operation.

In the Figure 33 embodiment of the present invention, it has been determined that an effective length-to-diameter ratio for a nylon monofilament cord or the like, will often be greater than 40:1 and is preferably about 49:1 for present purposes. It has further been found that the best cutting cord for the purposes of this embodiment are extruded nylon cord, having a diameter of about 0.060 inches to about 0.125 inches, with 0.065 inches being preferred. The normal rotating speed will be on the order of 6000-10,000 RPM, with 8,500 RPM being preferable during normal use.

Referring now to Figures 33-42, it may be seen that the lower end of the drive shaft 36 extends downwardly through head 42 from motor 10 and is arranged for threading engagement at its lower end 35 with keyed retainer member 37 in threaded aperture 39. Drive shaft 36 inserts tightly into aperture 39 in head 42 and retains its relationship with head 42 by means of its flattened portion 31, which is insertable into head 42.

Rotation of drive shaft 36 by motor 10 causes head 42 to also rotate, thereby extending the string to perform a cutting function.

Spool 44 contains spare cutting cord 46 therein, which is arranged for paying out at predetermined times and at predetermined lengths to vary the effective working length of the cutting cord 26. Spool 44 is composed of a bottom wall 48 and a top wall 50 spaced a predetermined equidistance by hub 52.

Interior and on the top side of hub 52 is a centrally located opening 57 wherein two annular locking protuberances 49 and 51 spaced diametrically opposite each other and extending partly around the interior of spool 44 are arranged for releasable engagement with protuberances 43 and 45 on retainer member 37. Removal of spool 44 from head 42 may be accomplished by rotating spool 44 by means of grip element 33 so that locking protuberances 49 and 51 are rotated out of locking engagement with protuberances 43 and 45 on retainer member 37. Removal of spool 44 from head 42 enables a fresh spool to be inserted into head 42, or spool 44 may be rewound with replacement cord or the like.

Window insert member 76, composed of arms 76A and 76B and inserts 77A and 77B, is releasably retained within head 42 by retainer member 37 which is insertable through aperture 79. Inserts 77A and 77B correspond to and insert into window apertures 60 and 62 in head 42, and enhance cutting cord life.

As previously described, head 42 is rotated by shaft 36 of motor 10 inserted into aperture 39 of head 42. The spool 44 with cutting cord 26 wound thereon is contained within head 42 between two semicircular housing walls 41A and 41B, each having inner walls 202 and outer walls 200. The head 42 is provided with two window apertures 60 and 62 wherefrom a cutting cord may protrude, the said two apertures each having a curvilinear bearing surface 61.

Referring now to Figures 43-49, an alternate embodiment of the present invention is shown, similar to that depicted in Figures 34-42. As hereinbefore described with regard to head 42, the single cord circular cutting head 142 is rotated by the shaft 136 of motor 10. The lower end of drive shaft 136 is arranged for threading engagement with retainer member 137 in aperture 135.

Drive shaft 136 inserts tightly into aperture 131A and in head 142 and retains its relationship with head 142 by means of its flattened portion 131, as hereinbefore discussed.

Spool 144, similar to spool 44 in Figure 34, contains spare cutting cord 146 therein which is inserted into aperture 155 and wound onto and payed out from hub 152 as hereinbefore described in detail. Spool 144 also has a bottom wall 148 and top wall 150.

Hub 152 extends beyond bottom wall 148 to form glide ball 133. Interior of hub 152 is a centrally located cavity 157 wherein three annular locking protuberances 151A, 151B and 151C, equally spaced about the circumference of cavity 157, are arranged for releasable engagement with protuberances 149A, 149B, and 149C within head 142.

Removal of spool 144 from head 142 may be accomplished by rotating spool 144 by means of glide ball 133, the external surface of which may be provided with equally spaced-apart vertical lineal protrusions 132 to insure a better grip for easier removal, so that locking protuberances 151A, 151B and 151 C are rotated out of locking engagement with protuberances 149A, 149B and 149C within head 142.

Window insert member 176, composed of arms 176A, 176B and 176C and inserts 177A, 177B and 177C, is releasably retained within head 142 by spool 144.

Aperture 179 permits retainer member 137 to pass therethrough and engage drive shaft 136. Inserts 177A, 177B and 177C correspond to and insert into window apertures 160, 162 and 164 in head 142, and enhance cutting cord life as has previously been explained in detail.

Head 142 is similar to head 42 previously depicted and described. The spool 144 with cutting cord 146 wound thereon is contained within head 142 between three partcircular housing walls 141A, 14113 and 141 C, each having inner walls 202 and outer walls 200. The head 142 is provided with three window apertures 160, 162 and 164 wherefrom a cutting cord may protrude, the said three apertures each having a cur vilinear bearing surface 161.

With reference to Figures 44 and 45, a further feature of the present invention includes means whereby the three exit head embodiment may be balanced rotationally so as to not transmit unwanted vibrations to the motor shaft 136. To overcome this deficiency, and with reference to Figure 46, there will be seen three balancing ribs 160A, 162A, 164A. Each balancing rib is located diametrically opposite its corresponding window aperture. Thus, for example, balancing rib 164A balances window aperture 164.

As hereinbefore noted, the curvilinear cord bearing surface 161 of each of window apertures 160, 162, 164, is preferably formed by constructing the head member 142 of a pair of spaced apart walls 200 and 202 seen in Figures 44 and 45. Thus, wall 200 defines the outer periphery of head member 142 whereas wall 202 defines the inner periphery thereof. It will be seen that in Figure 44, the balancing ribs 1 60A, 1 62A and 164A, are placed between walls 200 and 202 and are positioned radially with respect to the axis of rotation of the head or housing member 142. As illustrated in Figure 44, the space between walls 200 and 202 is otherwise open. It should be noted, that the two exit head embodiment of Figures 35 and 36 is likewise of double-walled construction as hereinbefore explained with reference to Figures 44 and 45.

WHAT WE CLAIM IS: 1. Apparatus for cutting vegetation comprising: a length of non-metallic flexible cord; rotatable support means for revolving said cord in a cutting plane; an electric motor for rotating said support means; and a full wave rectifier electrically connected between said motor and an A.C. mains

Claims (16)

**WARNING** start of CLMS field may overlap end of DESC **. explained in detail. Head 142 is similar to head 42 previously depicted and described. The spool 144 with cutting cord 146 wound thereon is contained within head 142 between three partcircular housing walls 141A, 14113 and 141 C, each having inner walls 202 and outer walls 200. The head 142 is provided with three window apertures 160, 162 and 164 wherefrom a cutting cord may protrude, the said three apertures each having a cur vilinear bearing surface 161. With reference to Figures 44 and 45, a further feature of the present invention includes means whereby the three exit head embodiment may be balanced rotationally so as to not transmit unwanted vibrations to the motor shaft 136. To overcome this deficiency, and with reference to Figure 46, there will be seen three balancing ribs 160A, 162A, 164A. Each balancing rib is located diametrically opposite its corresponding window aperture. Thus, for example, balancing rib 164A balances window aperture 164. As hereinbefore noted, the curvilinear cord bearing surface 161 of each of window apertures 160, 162, 164, is preferably formed by constructing the head member 142 of a pair of spaced apart walls 200 and 202 seen in Figures 44 and 45. Thus, wall 200 defines the outer periphery of head member 142 whereas wall 202 defines the inner periphery thereof. It will be seen that in Figure 44, the balancing ribs 1 60A, 1 62A and 164A, are placed between walls 200 and 202 and are positioned radially with respect to the axis of rotation of the head or housing member 142. As illustrated in Figure 44, the space between walls 200 and 202 is otherwise open. It should be noted, that the two exit head embodiment of Figures 35 and 36 is likewise of double-walled construction as hereinbefore explained with reference to Figures 44 and 45. WHAT WE CLAIM IS:

1. Apparatus for cutting vegetation comprising: a length of non-metallic flexible cord; rotatable support means for revolving said cord in a cutting plane; an electric motor for rotating said support means; and a full wave rectifier electrically connected between said motor and an A.C. mains input.

2. Apparatus according to claim 1 including a casing extending around said motor, a hollow handle extending from said casing, an electric switch located adjacent the free end of the handle, and an electric lead extending through said hollow handle and connecting said switch with said rectifier.

3. Apparatus according to claim 2 including a casing portion extending obliquely from said motor and tapering towards an end region defining a connection for said handle, said rectifier being located in said tapering casing portion.

4. Apparatus according to any preceding claim wherein the handle includes coupling means whereby one portion of said handle may be rotated about the handle axis in increments with respect to another portion.

5. Apparatus according to claim 4 wherein said coupling means comprises a first tubular member telescopically inserted in a second tubular member, interengageable formations whereby rotational alignment of said first member may be fixed in relation to said second member in any of a plurality of alignments; said formations being disengageable upon telescopic movement of said first member with respect to said second, and resilient means biased against said telescopic movement for maintaining inter-engagement in any one of said plurality of alignments.

6. Apparatus according to any preceding claim wherein said cord has a diameter of at least 0.06 inches.

7. Apparatus according to any preceding claim further incorporating a knife assembly whereby said cord may be cut to a desired ength.

8. Apparatus according to claim 7 wherein said knife assembly comprises a pair of spaced apart parallel flanges on a surface of said apparatus; a blade mounted transversely between said flanges and having a cutting edge disposed outwardly from said surface; a pressure block having a force plate mounted thereon, said pressure block being hinged for pivotal movement towards the space defined between said flanges so that at least part of said force plate may be brought adjacent and in overlapping relationship with said blade, whereby a cord may be forced against said blade by pivotal movement of said block.

9. Apparatus according to claim 8 wherein said blade is demountable.

10. Apparatus according to either claim 8 or claim 9 further comprising an aperture through said pressure block disposed between said force plate and said pivotal mounting.

11. Apparatus according to any one of the preceding claims wherein said rotatable support means includes a cutting head having at least one aperture in a sidewall thereof for receiving said cord, a trailing edge wall of said aperture having a curvilinear surface of substantially tear drop like cross-section whereby friction of the cord extending through said aperture during rotation of said head is reduced.

12. Apparatus according to any preced

ing claim wherein said rotatable support means includes a cutting head having at least one aperture in a sidewall thereof for receiving said cord, the trailing edge wall of the aperture being fitted with a bearing insert whereby the friction of the cord extending through said aperture during rotation of said head is reduced.

13. Apparatus according to any preceding claim wherein said rotatable support means includes a cutting head having a co-axially located cord storage spool and having at least one aperture in a sidewall of said cutting head, said spool being provided with balancing means whereby the balance of said cutting head is maintained during rotation while a portion of said cord is extended from said spool through said aperture to a free end portion lying outside said head.

14. Apparatus according to claim 13 wherein said balancing means is constituted by a rib provided on said spool substantially diametrically opposite said aperture and of a mass substantially equal to said cord portion lying outside said head.

15. Apparatus according to claim 13 including a pair of diametrically opposite apertures for receiving said cord and wherein said balancing means is constituted by a tubular guard element fitting snugly over the circumference of said spool, said element having a cut out portion adjacent the aperture through which said cord passes, said cut out portion having a mass substantially equal to said cord portion lying outside said head.

16. Apparatus according to claim 1 substantially as described herein with reference to any one of the embodiments described herein with reference to the accompanying drawings.