US3858383A

US3858383A - Electrically powered tool

Info

Publication number: US3858383A
Application number: US131141A
Authority: US
Inventors: Richard W Glover
Original assignee: Rockwell International Corp
Current assignee: Porter Cable Corp
Priority date: 1971-04-05
Filing date: 1971-04-05
Publication date: 1975-01-07
Anticipated expiration: 1992-01-07
Also published as: FR2132421A1; CH554632A; FR2132421B1; CA949114A; GB1360573A; DE2214666A1

Abstract

An electrically powered tool having a hollow metallic, usually elongated handle secured at one end to a motor-receiving and tool-supporting housing, an inner, relatively rigid tube extending axially through the metallic in spaced apart relation thereto, and one or more electrical conductors each having an electrical insulation covering extending through the inner insulating tube and into the housing for connection to the tool driving motor therein for supplying operating current thereto. A handle grip may be provided at the end of the handle remote from the housing. The inner insulation tube and the insulation covering on the conductors provide a double insulation construction in the handle. The handle and insulating tube are supported in such a manner that no metallic fasteners are inserted through the walls of the handle and the insulating tube.

Description

llnited States Patent [191 Glover .lan.7, 1975 ELECTRICALLY POWERED TOOL [75] Inventor: Richard W. Glover, Joppa, Md.

[73] Assignee: Rockwell llnternational Corporation,

Pittsburgh, Pa.

[22] Filed: Apr. 5, 1971 [21] Appl. No.: 131,141

[52] US Cl 56/l0.5, 56/l7.4, 56/255 [51] Int. Cl A0lg 3/06 [58] Field of Search 56/256, 10.1, 10.5, 17.4,

56/l7.5, 17.6, 10.3, 255, DIG. 18; 306/21,

[56] References Cited UNITED STATES PATENTS 2,672,002 3/1954 Nelson 56/256 X 2,926,478 3/1960 Jepson 56/l0.3 3,034,275 5/1962 Happe et a1. 56/l7.5 X 3,350,864 11/1967 Sheps et al 56/l7.5 X

Primary Examiner-Louis G. Mancene Assistant ExaminerJ. N. Eskovitz [5 7] ABSTRACT An electrically powered tool having a hollow metallic, usually elongated handle secured at one end to a motor-receiving and tool-supporting; housing, an inner, relatively rigid tube extending axially through the metallic in spaced apart relation thereto, and one or more electrical conductors each having an electrical insulation covering extending through the inner insulating tube and into the housing for connection to the tool driving motor therein for supplying operating current thereto. A handle grip may be provided at the end of the handle remote from the housing. The inner insulation tube and the insulation covering on the conductors provide a double insulation construction in the handle. The handle and insulating tube are supported in such a manner that no metallic fasteners are inserted through the walls of the handle and the insulating tube.

5 Claims, 12 Drawing Figures Patented Jan. 7, 1975 3 Sheets-Sheet 1 1N VENTOR RIG/MRO W. 6201 67? ATTORNEYS Patented Jan. 7, 1975 3,858,383

3 Sheets-Sheet 2 I MQWWZ WW ATTO NEYS IELIECTRICAILLY POWERED TOOL FIELD OF INVENTION This invention relates to electrically powered devices and is especially concerned with power tool constructions in which electrical conductors extend through a handle to supply current to a tool-driving electric motor.

BACKGROUND In electrically powered lawn trimmers, combination lawn trimmer and edger tools, and other similar devices, the tool construction is conventionally provided with an elongated, tubular handle through which conductors having an insulating covering are extended to supply current to the electric motor in the tool housing. The elongated handle is fixed to the motor-receiving housing and is usually made of metal to provide structural strength and economy of manufacture. The power-operated lawn trimmer-edger described in US. Pat. No. 3,350,864 (issued to M. I. Sheps et al. on Nov. 7, i967) is typical of this construction.

The tool construction described in US. Pat. No. 3,350,864 is disadvantageous, for if the electrical insulating cover on one or more of the electrical conductors becomes defective to expose one or more of the electrical conductors, the exposed conductor or conductors may contact the metal handle and thus present a hazardous condition of shock to the user of the tool.

SUMMARY & OBJECTS OF INVENTION The present invention overcomes the foregoing problem by providing for a novel handle construction wherein a relatively rigid inner tube of electrical insulating material extends through the outer tubular metallic handle and wherein the electrical conductors extend through the inner tube. As a result, the insulating covering on the conductors and the inner tube provide a double insulation construction for the safety of the user of the tool. In accordance with a preferred embodiment of this invention, the inner insulating tube extends at both ends axially beyond the tubular handle.

In further safeguarding against hazardous shock conditions, the inner tube of this invention is retained in place solely by electrically insulating plastic parts, and no metallic fasteners or other metallic parts of any kind are inserted into or through the outer metal handle. By not extending any metallic fasteners or other metallic parts through the outer metallic handle, the possibility of puncturing the inner insulating tube and contacting the electrical conductors extending through the inner tube is avoided. Furthermore, no parts of any kind extends through the wall of the inner insulating tube.

According to this invention, the motor-receiving housing is of the split clam shell type having two mating plastic halves. In assembled relation, the outer metal handle is confined against radial or transverse movement relative to the housing by being clamped at its lower end between the mating halves of the housing. The outer metal handle is confined against axial or longitudinal displacement relative to the housing by internal plastic bosses which are integral with the split housing halves and which interfittingly and radially extend through apertures in the outer handle. The split housing halves are rigidly secured together in the usual manner by metal screws or the like, but none of these screws extend through or into either the outer metal handle or the inner insulating tube.

In this invention, the handle grip, which houses the motor-controlling switch, is also of the split clam shell type having two mating, plastic clam shell halves. The upper end of the outer handle is clamped between the mating halves of the handle grip, and, similar to the motor-receiving housing construction, the handle grip halves are integrally formed with internal bosses which interfittingly and radially extend through apertures in the upper end of the outer handle. In this manner the tubular handle and the handle grip are secured against relative movement. The mating halves of the handle grip are rigidly and securely fastened together by metal screws. But, like the motor-receiving housing construction, none of the screws securing the mating handle grip halves together extend into or through either the outer metallic handle or theinner insulating tube.

To secure the inner insulating tube against displacement relative to the motor-receiving housing, the outer metallic handle and the handle grip, both the motor receiving housing and the handle grip are formed with ribs to define axially spaced apart, internal wells that receive opposite ends of the inner insulating tube. Engagement of the inner insulating tube with side and bottom wall surfaces of these wells retain the inner insulating tube in place and in concentric radially spaced relation to the outer metallic handle. Relative transverse movement of the inner insulating tube may also be limited by abutment of the inner tube with the previously described plastic bosses.

From the foregoing handle and housing construction, it will be appreciated that the metallic handle and other metallic parts, such as fasteners, are in spaced relation to and disposed outwardly of the inner insulation tube to thereby provide an effective and economical handle insulation construction thatsafeguards the user against hazardous shock conditions.

With the foregoing in mind, a major object of this invention is to provide a novel construction that guards against hazardous shock conditions in the type of electrically powered tool that has electrical conductors extending through an elongated, metallic handle.

Another important object of this invention is to provide a novel construction for electrically insulating conductors from an elongated metallic handle and other metal parts in the type of electrically powered tool wherein the conductors extend through the handle to a motor that is mounted in a housing at one end of the handle.

A more specific object of this invention is to provide a novel construction for mounting an outer metallic handle and an inner electrical insulating tube in an electrically powered tool having a motor-receiving housing at one end of the handle and conductors extending through the inner tube to the motor in the housing.

Still another important object of this invention is to provide a novel electrically powered tool which provides safety in handling and operation and which is easy and economical to manufacture.

Further objects of this invention will appear as the description proceeds in connection with the appended claims and the below-described drawings.

DESCRIPTION OF DRAWINGS FIG. 1 is a front elevation of an electrically powered trimmer incorporating the principles of this invention; FIG. 2 is a side elevation of the trimmer shown in FIG. 1;

FIG. 3 is an enlarged, fragmentary, longitudinal section taken substantially along lines 33 of FIG. 1;

FIG. 4 is an enlarged, fragmentary section taken substantially along lines 44 of FIG. 1;

FIG. 5 is a fragmentary bottom plan view of the trimmer shown in FIGS. 1 and 2;

FIG. 6 is a section taken substantially along lines 6-6 of FIG. 3;

FIG. 7 is a section taken substantially along lines 7-7 of FIG. 3;

FIG. 8 is a section taken substantially along lines 88 of FIG. 3;

FIG. 9 is a section taken substantially along lines 99 of FIG. 4;

FIG. 10 is a section taken substantially along lines 10-10 of FIG. 4;

FIG. 11 is a section taken substantially along lines 11-11 of FIG. 3; and

FIG. 12 is a section taken substantially along lines 1212 of FIG. 4.

DETAILED DESCRIPTION The invention is described herein as being incorporated into an electrically powered trimmer. However, it will be appreciated that the invention herein is equally applicable to other electrically powered tools having a hollow, metallic handle fixed at one end to a motor-receiving housing and electrical conductors extending through the handle to a tool-driving motor in the housing.

As shown in FIGS. 1 and 2, the trimmer incorporating the principles of this invention generally comprises a hollow, longitudinally split, clam shell type motor housing 20, an elongated, tubular handle 22, and a handle grip 24. As shown in FIG. 3, an electric motor 26 of conventional construction is mounted in housing and has an armature shaft 28 that is rotatably supported in housing 20 by bearings indicated at 30. A rotary cutting or trimmer blade 32 is coaxially fixed on the lower end of shaft 28 by suitable, conventional means. The armature shaft rotational axis is vertical and blade 32 is horizontally oriented when the trimmer is disposed in its normally operative, upright position. Bearings and the various parts of motor 26 are supported in housing 20 in any suitable, conventional manner. Handle 22 is straight and may be formed from any suitable material such as aluminum.

As shown in FIGS. 1 and 2, housing 20 is formed with a hollow motor-receiving body portion or skirt 34 and a hollow, handle-receiving collar or boss portion 35. A

tool supporting skid plate 36 (see FIGS. 1, 2 and 5) is adapted to be set on the ground as the trimmer is guided by the user over the surface. As shown, skid plate 36 is vertically below housing portion 34 and motor 26, and blade 32 is horizontally disposed in an open, recessed region 38 between skid plate 36 and housing portion 34. Skid plate 36 is suitably fixed tothe rearward end of housing 20 by a rib portion indicated at 39. With this construction the recessed region 38 receiving blade 32 is open at the front and along both sides and is closed at the rear on rib portion 39. The lower end of handle 22 is coaxially received in collar portion 35.

As best shown in FIG. 1, housing'20 is longitudinally divided into two mating, essentially

complementary shells

40 and 42 to provide a clam shell type enclosure for internal parts of the trimmer.

Shells

40 and 42 are separately molded from a suitable, electrically nonconductive or insulating plastic material and have oppositely dished curvatures to define interior cavity for receiving motor 26.

Shells

40 and 42 are formed with mating longitudinal edge surfaces as indicated at 44 in FIG. 3. These edge surfaces 44 seat against each other in a plane that longitudinally and medially intersects body portion 34 and collar portion 35. Thus,

shells

40 and 42 respectively define mating halves of body portion 34 and collar portion 35. The edge surfaces 44 are furthermore seated against each other in a plane containing both the rotational axis of shaft 28 and the longitudinal axis of handle 22. Housing halves 40 and 42 are rigidly secured together by screws 48 which extend through smooth walled bores in one of the housing halves and which are threaded into aligning tapped bores in the other of the housing halves.

As shown in FIGS. 2 and 3, collar portion 35 extends upwardly and rearwardly from the rearward end of the housing in angularly spaced relation to body portion 34 in such a manner that an acute angle is defined between the longitudinal axes of body portion 34 and collar portion 35, with this construction an acute angle is also defined between the longitudinal handle axis and the aligned longitudinal axes of body portion 34 and shaft 28 As shown in FIGS. 3, and 8, handle 22 is clamped at its lower end between the collar-defining portions of

housing halves

40 and 42 and is confined against transverse or radial movement relative to housing 20 solely by separable seating engagement with opposing interior surfaces of

housing halves

40 and 42 as best shown in FIG. 8. To confine handle 22 against rotational and longitudinal movement relative to housing 20, housing half 40 is molded with two internal bosses or lugs 50 and 51 (see FIGS. 3, 6 and 7), and housing half 42 is similarly molded with two interior bosses or lugs 52 and 53. Bosses 50-53 extend radially inwardly relative to handle 22 and interfittingly extend through separate apertures 56 (see FIGS. 3, 6 and 7) that are radially formed through the tubular wall of handle 22.

Bosses

50 and 51 are spaced apart along the axis of handle, as are

bosses

52 and 53, and

bosses

52 and 53 respectively radially align with

bosses

50 and 51. Separable abutment of the edges of apertures 56 with bosses 50-53 confines handle 22 against axial and rotational motion relative to collar 44.

From the foregoing description it is clear that handle 22 is confined against movement relative to housing 20 solely by separately seating engagement with surfaces of

housing halves

40 and 42. Bosses 50-53 are internally formed on those segments of

housing halves

40 and 42 that define collar portion 35, and bosses 50-53 extend radially with respect to collar portion 35.

As shown in FIGS. 1, 2 and 4, handle grip 24 is mounted on the upper end handle 22. Grip 24, like housing 20, is of the split clam shell construction which is longitudinally divided into two mating,

complementary shells

60 and 62.

Shells

60 and 62 are separately molded from a suitable electrical insulating plastic material and have oppositely dished curvatures to define an interior cavity 66 (see FIG. 4). In assembled relation of

halves

60 and 62, handle grip 24 is formed with a collar or tubular end portion 68 and a gripping portion 70 that extends horizontally and rearwardly from portion 68. Collar portion 68 coaxially receives the upper end of handle 22 as shown.

Shells

60 and 62 are formed with mating longitudinal edge surfaces indicated at 72 in FIG. 4. These edge surfaces 72 seat against each other in a plane which contains the longitudinal axis of handle 22 and which longitudinally and medially intersects portions 68 and 70.

Halves

60 and 62 are rigidly secured together by screws 71 which extend through smooth walled bores in one of the halves and which are threaded into aligning tapped bores in the other of the halves.

As best shown in FIGS. 1 and 4, handle 22 is clamped at its upper end between the collar defining portions of

halves

60 and 62 and is confined against radial or transverse movement relative to handle grip 24 solely by separable seating engagement with opposing interior surfaces of the collar defining portions of

halves

60 and 62. A boss construction similar to bosses 50-53 is provided on

halves

60 and 62 for confining handle grip 24 against rotary or longitudinal movement relative to handle 22. Accordingly, like reference numerals suffixed by the letter a have been applied (see FIGS. 4, 9 and to designate the internal bosses or lugs on grip handle halves 60 and 62.

As shown in FIGS. 4, 9 and 10 grip half 60 is molded with bosses 50a and 51a, and handle grip half 62 is molded with

bosses

52a and 53a. Bosses 50a-53a extend radially inwardly from the interior of its

grip hanand bosses

52a and 53a respectively radially align with bosses 50a and 51a. Separable abutment of bosses 50a-53a with the edges of apertures 78 confines handle grip 24 against longitudinal and rotation movement relative to handle 22. Thus, it will be appreciated that handle grip 24 is confined against movement relative to handle 22 solely by separable seating engaging surfaces of

handle grip halves

60 and 62 with handle 22.

Referring to FIGS. 3 and 4, insulated, power cord conductors 90 extend through handle grip 24 and a rigid, electrical insulating tube 92 in handle 22 to motor 26 for supplying operating currenty to motor 26. One or more of the conductors 90 is connected through a motor-controlling switch 94.

As shown in FIG. 4, switch 94 is suitable mounted in portion 70 of handle grip 24, and has a switchactuating, finger-manipulatable trigger 96 extending through an aperture on the underside of grip portion 70 in such a manner that it is engagable by the users index finger when he grips portion 70 with one hand. A trigger guard 98 externally extends around trigger 96. Guard 98 is preferably formed by two mating rib portions 100 (See FIGS. 2 and 4) which are respectively integral, molded segments of

handle grip halves

60 and 62. As shown, guard 98 extends from the underside of grip portion 70 to the adjacent side of collar portion 68.

The power cord comprising conductors 90 for supplying operating current to motor 26 is generally indicated at 102 in FIG. 4 and is of conventional construction. Power cord 102 has an outer, relatively thick insulating cover extending around both conductors and terminating in a suitable fitting 104. Fitting 104 is fixed in an aperture in the rearward end of handle grip portion as shown. Each of the conductors extending through and beyond the outer power cord insulation is separately covered with electrical insulation as shown in FIGS. 3 and 4. The portions of conductors 90 extending beyond fitting 104 internally pass through cavity 66 and tube 22 and into the interior of housing portion 34 where they are connected to motor 26.

As shown in FIGS. 3 and 4, insulating tube 92 is formed from any suitable electrical insulating material and coaxially extends through handle 22. Tube 92 is substantially concentric with handle 22 and extends at boths ends axially beyond handle 22 by sufficient distances to ensure that conductors 90 do not rub against or come within close proximaty to the ends of handle 22 in housing 20 and handle grip 24. The tubular walls of tube 90 is imperforate so that the only openings are the open, opposite ends of the tube.

The opposite ends of tube 92 are coaxially received in relatively shallow axially aligned, opposed wells 106 (FIG. 3) and 108 (FIG. 4). Separable surface abutment of the opposite ends of tube 92 with the smooth cylindrical side walls and axially opposed flat bottoms of wells 106 and 108 confine tube 92 against movement relative to housing 20, handle 22 and handle grip 24 to thus retain rube 92 concentrically in place in radially inwardly spaced apart relation to the cylindrically smooth inner periphery of handle 22 and other parts with the possible exception of the ends bosses 50-53 and 50a-53a.

Referring to FIGS. 3 and 11, well 106 is formed by a pair of abutting complementary,

internal rib portions

110 and 112 in collar portion 35. Rib portion 110 is a rigid, integral, molded part of housing half 40, and rib portion 112 is a rigid integral molded part of housing half 42. Well 106 is formed partly in rib portion 110 and partly in rib portion 112 as shown in FIG. 11.

Rib portions

110 and 112 are axially spaced from the adjacent end of handle 22 and extend generally radially inward from the lower end of collar portion 35 at its juncture with the remainder of housing; 20. Well 106 axially align with the longitudinal axis of collar portion 35. Conductors 90 extend freely through an enlarged opening in the bottom wall .of well 106 and are spaced sufficiently far apart from the rib surfaces so as not to rub against the rib surfaces.

Referring to FIGS. 4 and 12, well 108 is formed by an internal handle grip rib construction which is substantially the same as

rib portions

110 and 112. Accordingly, like reference numerals suffixed by the letter a have been applied to designate the rib portions defining well 108.

Rib portions 110a and 112a extend radially inwardly in the upper region of collar portion 68. Rib portion 110a is an integral molded portion of handle grip half 60, and rib portion 112a is an integral, molded portion of handle grip half 62. Well 108 is formed partly in rib portion 110a and partly in rib portion 112a as shown in FIG. 12. Rib portions 110a and 112a are axially spaced from the adjacent end of handle 22, and well 108 axially aligns with the longitudinal axis of collar portion 68. Conductors 90 extend freely through an enlarged aperature in the bottom wall of well 108 and are sufficiently spaced from the rib surfaces so as not to rub against the rib surfaces.

As shown in FIGS. 6-10, bosses 50-53 and 50a-53a may optionally extend radially into handle 22 by a sufficient distance to provide end abutment surfaces that are adapted to abut the outer periphery of tube 92 for further limiting transverse or radial displacement of tube 92 in the assembly. Tube 92 and the insulation covering on each conductor 90 provides a safeguarding double insulation.

From the foregoing description it will be appreciated that handle 22 and tube 92 are held in place solely by separable seating engagement wtih interior, electrically insulating surfaces of the plastic clam shell halves 40, 42, 60 and 62. Furthermore, no metallic fasteners or other metallic parts of any kind (apart from the conductors themselves, of course) are disposed in, or inserted into or through handle 22. Instead, only the plastic bosses 50-53 and 50a-53a are inserted into handle 22. Thus all metallic parts are spaced outwardly from handle 22 and also from tube 92 so that there is no danger that such metallic parts will puncture tube 92 and- /or rub against the insulating covering of the conductors extending through the handle. In addition, it will be appreciated that no parts of any kind (apart from the conductors themselves) are disposed in or inserted into or through the inner insulating tube 92.

The double insulation construction provided by this invention effectively guards against hazardous shock conditions, and the construction is easy to assemble and economical to manufacture.

What is claimed and desired to be secured by Letters Patent is:

1. In an electrically powered lawn care tool, a housing, a rotatable cutting blade, an electric motor mounted in said housing for rotating said blade, an elongated, tubular handle member having one end received in said housing and extending upwardly and rearwardly from said housing when said housing is in its upright position, said housing being mounted on said handle member at said one end thereof, handle grip means positioned on said handle member, electrically insulated electrical conductor means connected to said motor for supplying operating current thereto, and a rigid tubular part made of electrical insulating material and extending axially through said handle member, said tubular part being formed separately of said electrically insulated conductor means, and said conductor means extending through said tubular part and into said housing for connection to said motor, said housing and said handle grip means being integrally formed with first and second means respectively, and said first and second means respectively engaging the opposite ends of said tubular part to confine said tubular part against axial movement relative to said handle member.

2. The electrically powered lawn care tool defined in claim 1, wherein said housing and said handle grip means are formed from electrical insulating material, and wherein said first and second means are disposed interiorly of said housing and said handle grip means respectively.

3. The electrically powered lawn care tool defined in claim 2, wherein said tubular part extends at both ends axially beyond said handle member and terminates at opposite ends respectively in saidhousing and said handle grip means.

4. The electrically powered lawn care tool defined in claim 1, wherein said first and second means support said tubular part in spaced apart relation from said handle member.

5. In an electrically powered lawn care tool having a rotatable blade, a motor housing divided into opposed, mating separately formed shells of electrical insulating material, means securing said shells together, an electric motor mounted in said housing for rotating said blade, a hand-manipulatable, elongated hollow, rigid handle member extending from said housing, handle grip means positioned on said handle member, electrically insulated conductors connected to said motor for supplying operating current thereto, and a tubular part made of electrically insulating material and extending through said handle member, with said conductors extending through said tubular part and into said housing, wherein said handle grip means is formed from electrical insulating material, and wherein said handle and said tubular part are respectively secured against displacement relative to said housing and said handle grip means and to each other only by separable seating engagement with surfaces of said housing and said handle grip means.

Claims

3. The electrically powered lawn care tool defined in claim 2, wherein said tubular part extends at both ends axially beyond said handle member and terminates at opposite ends respectively in said housing and said handle grip means.