US3798768A

US3798768A - Hedge trimmer assembly

Info

Publication number: US3798768A
Application number: US00271930A
Authority: US
Inventors: W Cowley; R Stutzke
Original assignee: Vermont American Corp
Current assignee: Robert Bosch Tool Corp
Priority date: 1972-07-14
Filing date: 1972-07-14
Publication date: 1974-03-26
Anticipated expiration: 1991-03-26

Abstract

The cutting blade of a hedge trimmer slides between rigidly bolted stationary guard and overlying cover plates in which portions of the stationary guard about its bolt apertures have been pressed into projections which project through slotted apertures of the cutting blade to engage the cover plate, the concave underside of the pressed projections being shaped to resist turning of the nuts on the bolts.

Description

United States Patent [191 Cowley et a].

[ Mar. 26, 1974 1 1 HEDGE TRIMMER ASSEMBLY [75] Inventors: William C. Cowley; Robert E.

Stutzke, both of Louisville, Ky.

[73] Assignee: Vermont American Corporation, Louisville, Ky.

[22] Filed: July 14, 1972 121] App]. No.1 271,930

{52] US. Cl. 30/223 [51] Int. Cl B26b 19/02 [58] Field of Search 30/210, 215, 216, 217, 30/218, 220, 221, 222, 223, 224, 225

[56] References Cited UNITED STATES PATENTS 109,479 11/1870 Wilson t 1 30/218 357.718 2/1887 Lee 30/222 X 525,783 9/1894 Gillette 30/220 2,575,038 11/1951 Banka 30/220 X 2,755,551 7/1956 Johnson 30/210 Primary Examiner-Donald G. Kelly Assistant Examiner-J. C. Peters Attorney, Agent, or Firm.1ohnson, Dienner, Emrich, Verbeck & Wagner 57 ABSTRACT The cutting blade of a hedge trimmer slides between rigidly bolted stationary guard and overlying cover plates in which portions of the stationary guard about its bolt apertures have been pressed into projections which project through slotted apertures of the cutting blade to engage the cover plate, the concave underside of the pressed projections being shaped to resist turning of the nuts on the bolts.

9 Claims, 6 Drawing Figures HEDGE TRIMMER ASSEMBLY This invention relates to electric hedge trimmers or the like and particularly to the blade assembly of such devices.

A principal object of the invention is to provide novel and improved means and method for slidably mounting the cutting blade of an electric hedge trimmer between its stationary guard and cover plate by a non-loosening connection which does not bind the blade.

Conventionally, a stationary guard is fixed to the trimmer handle and the cutter blade is assembled therebetween and a cover plate by means of spaced bolts which pass through aligned apertures in the three elements, the apertures of the cutting blade comprising elongated slots which accommodate reciprocal axial movement of the cutter blade relativeto the stationary guard in the operation of the hedge trimmer. Commonly, a shoulder bolt is used in order to avoid binding of the parts which would interfere with free reciprocal blade movement. Such bolts have a smooth surfaced cylindrical section which is long enough to extend from the head through the assembly and an outer threaded end of reduced diameter, the nut tightening against the bottom of the shoulder or cylindrical section. Ordinarily, bolts having a cylindrical section longer than the overall thickness of the assembly are selected to accommodate any variation in thickness of the parts constituting the assembly, and a light spring washer is placed under the head to take up slack or play. Alternatively, an ordinary bolt has been used with an enlarged sleeve over the bolt stem, the sleeve being long enough to keep the cover plate and stationary guard from locking onto the blade with tightening of the nut. However, particularly in this latter construction, there is a prob lem of the nut loosening with vibration of the hedge trimmer during its normal operation and a special type of locknut has to be employed.

In accordance with this invention; combination spacer guides are integrally formed in the stationary guard by striking annular portions of the material about each of its bolt holes. The integral projections thus struck ride in the cutter blade slots to guide the reciprocal axial movement of the blade and simultaneously provide an end surface against which the retainer or cover plate may be rigidly tightened using an, ordinary nut and bolt. The end of the die forming the concave side of the projections has a non-circular or polygonal shape corresponding to that of the nut so that it will form a seat or abutment on the under side of the projection which the nut engages as it is tightened on the threaded bolt end. This'seat or abutment provides resistance to further turning 'of the nut and so effectsa nonloosening connection of the assembly.

A feature of the invention is that the projections are struck to a depth only slightly greater than the thickness of the cutting blade wherefore the nut may be securely tightened on the bolts to produce a rigid assembly between the cover plate and stationary guard which does not bind the cutter blade.

A further feature of the invention is that the concave half of the striking die is so shaped that the lateral sides of the forming projections are. generally parallel and the projections have a lateral width only slightly less than the slot in the cutting blade so that they guide the reciprocal movement of the cutting blade-and, having a length considerable shorter than the corresponding dimension of the slots in the blade, do not interfere with the reciprocal movement.

The striking of the projection to the required shape maybe obtained economically and in a highly practical manner and the invention not only reduces assembly costs by lowering the number of elements required to be assembled, but also facilitates the assembling of the elements and eliminates the needs for washers, special nuts and the like which contributes to costs in terms of material as well as in labor. At the same time the invention makes it feasible to use an ordinary nut and bolt for the connections.

Many other objects, advantages and features of the invention will be at once apparent or will become so upon consideration of the description of a preferred embodiment of the invention which follows:

Referring now to the drawings which are illustrative of the invention and wherein like parts are identified by like reference numerals:

FIG. 1 is a perspective view of an electric hedge trimmer embodying the novel assembly comprising the present invention;

FIG. 2 is a cross sectional view taken through one of the connections of the cutter blade assembly and is particularly identified as taken along lines 22 of either FIG. 1 or 3 looking in the direction indicated by the arrows;

FIG. 3 on the other hand, is a longitudinal sectional view taken through the same connection along lines 33 of FIG. 2;

FIG. 4 is an exploded view the blade assembly;

FIG. 5 is a plan view of the underside of the assembly and is taken along lines 55 in FIG. 3 looking in the direction indicated by the arrows; and

FIG. 6 is a fragmented view taken along lines 6-6 of FIG. 3 looking in the direction indicated by the arrows.

of the parts comprising Referring now more specifically to the several views wherein like parts are identified by like reference numerals, FIG. 1 shows an electric hedge trimmer 10 which comprises a motor housing 12 and a handle 14 integral with the motor housing. A cutting blade assembly indicated generally at 16 comprises a stationary guard or fixed blade 18, a movable or cutting blade 20 and a retainer or coverplate 22. As illustrated in FIG. 4, the stationary guard 18 has four openings 24 which accommodate two pairs 26a, 26b of mounting screws used to secure the rear end of the stationary guard 18 to the under side of the hedge trimmer handle 14. .One of each said pairs of mounting screws 26a and 26b appear in FIG. 1. The portion of guard 18 which projects forwardly of the hedge trimmer handle is serrated along at least one edge thereof and comprises a series of teeth 28 relative to which the cutting teeth 34 of the blade 20 are reciprocated.-As shown in FIG. 4, cutting blade 20 overlies guard 18 and has a lateral slot 30 adjacent its innermost end which is engaged by drive mechanism (not shown) operated by motor 12 to reciprocate the blade 20 in ato and fro relation longitudinally of the stationary guard 18. The rear end of the cuttingblade 20 terminates short of mounting screws 26b and has a pair of longitudinally extending slots 32 through which the forward located pair of mounting screws 26a pass to permit said reciprocal movement. The cutting teeth 34 of blade 20 cooperate with the serrations 20 of the stationary guard to cut or trim hedge branches as in the usual operation of hedge trimmers. It will be understood that stationary guard 18 and cutting blade 20 also may have teeth arranged on both their longitudinal edges, as is also conventional. At spaced intervals along the length of the cutting blade 20 are aligned longitudinal slots 36, one of which is illustrated in FIG. 4. Said slots 36 align with apertures 38 in the stationary guard and apertures 40 in the cover plate 22 to receive threaded bolts 42 which secures the illustrated assembly of cover plate 22, stationary guard 18 and reciprocal cutting blade 20 therebetween. Nuts "44 are tightened on the threaded end of each said bolts blade 20 and preferably their upper annular surface 50 about aperture 38 isessentially planar and generally parallel to said side 48 of stationary guard. The material thickness of the projections, measured between their raised outer surface 50 and concave recessed underside 52 is obviously no greater but substantially equal to the material thickness of the stationary guard 18 from which they are pressed. The substantially equal dimension derived by the die operation performed in the production of these generally concavo-convex projections 46 provides for a greater economy of material (e.g. steel) usage. Further a simple and efficient construction is provided. The portion of the striking die which forms the concave underside 52 of the projections 46 preferably has an end shaped to simultanesously produce a polygonal-shaped depression or seat 54 in said underside 52 which is only slightly larger than and corresponds to the shape of the nuts 44 which are threaded to the ends of bolts 42. The other or receiving die is preferably so shaped that the formed projection is provided with generally parallel lateral sides 56 disposed normal to the surface 48 whereas the leading and trailing

sides

58, 60 of the projection are unrestrained by the striking dies so that these sides assume a generally inclined stretched shape as illustrated best .in FIGS. 3 and 4. As seen best in FIGS. 2 and 6, the

struck projections 46 have a width only slightly less than the width of the receiving slot 36 so that their parallel sides 56 act to confine or guide the reciprocal movement of the cutting blade and the length of said projections is considerably less than the length of said slot 36 so as to accommodate said reciprocal movement. As illustrated by FIGS. 2 and 3, the cutting blade is readily assembled with the stationary guard 18 by locating its spaced slots 36 over the correspondingly spaced projections 46 and positioning the retainer plate or cover plate 22 thereover with its apertures aligned with the apertures 38 in said projections 46 of the stationary guard 18. When thus aligned, ordinary bolts 42 may be passed through the aligned apertures and nuts 44 tightened on their threaded ends. Projections 46 have a height greater than the thickness of the cutter blade 20 wherefore the nuts may be tightened firmly on the bolt end to produce a rigid connection of the cover plate to the stationary guard without binding the blade therebetween. As a nut 44 is tightened into its receiving depression or seat 54 on the concave underside of the projections, the sides of the nut are drawn into engagement with wall 62 of said seat 54 which then provides resistance to turning of the nut and there will be no tendency for the assembly to loosen as it is subjected to vibration during operation of the hedge trimmer.

From the above, it will be apparent that all of the recited objects, advantages and features of the invention have been demonstrated as obtainable in a highly convenient and practical manner. It will be further appreciated that many variations, changes and/or rearrangement of the described parts may be made-in keeping with the spirit of the invention and as defined by the appended claims.

Thus having described our invention, we claim:

1. In a hedge trimmer or the like having drive means for reciprocating a cutting blade relative to a stationary guard and a cover plate between which the cutting blade is slidably assembled, the improvement wherein the cutting blade has at least one elongated slot with generally parallel sides extending longitudinally of the blade, one of the said stationary guard and cover plate having an apertured projection pressed therefrom to the form of a raised outer side and recessed underside, said projection extending into said slot and having a height only slightly greater than the thickness of the cutting blade, the thickness of the projection between its raised outerside and recessed underside being no greater than the thickness of the one of said stationary guard and cover plate from which it is pressed and said projection further having a width and a length less than the corresponding width and length of said slot in the cutting blade, the other of said stationary guard and cover plate having an aperture which aligns with the aperture of said projection, and a connector element extending through said apertures rigidly securing the cover plate to the stationary guard, the cutter blade being free to axially slide therebetween.

2. The improvement of claim 1 wherein the projection has a width only slightly less than the width of the slot and a length considerably less than the length of the slot. I

3. The improvement of claim 2 wherein the lateral sides of the projection are generally parallel to each other and normal to the plane of the surface from which it projects.

4. The improvement of claim 1 wherein the connector element comprises a bolt and the recessed underside of the projection includes a non-circular shaped seat which receives a nut into which the threaded stem of the bolt is threadedly connected to resist turning of the nut.

5. The improvement of claim 1 wherein the cutting blade has a plurality of axially aligned slots spaced longitudinally thereof and the stationary guard has one such projection extending through each said slots, each said projections having a concave underside.

6. The improvement of claim 5 wherein each said projections has a width only slightly less than the width of the slot which receives the same and a length considerably less than the length of the said slot.

7. The improvement of claim 5 wherein the two lateral sides of each said projections are generally parallel with each other and the sides of the other projections and generally normal to the plane of the stationary guard surface from which they project.

8. The improvement of claim 5 wherein a bolt extends through aligned apertures in the cover plate and projections of the stationary guard and a nut is tight- 5 threaded end of the bolt.

cned on the threaded end of the bolt which projects into the concave underside of the projections.

9. The improvement of claim 8 wherein the concave underside of the projections includes wall portions which resist turning of the nut when tightened on the

Claims

2. The improvement of claim 1 wherein the projection has a width only slightly less than the width of the slot and a length considerably less than the length of the slot.

8. The improvement of claim 5 wherein a bolt extends through aligned apertures in the cover plate and projections of the stationary guard and a nut is tightened on the threaded end of the bolt which projects into the concave underside of the projections.

9. The improvement of claim 8 wherein the concave underside of the projections includes wall portions which resist turning of the nut when tightened on the threaded end of the bolt.