AU2001287294A1

AU2001287294A1 - Method of forming tool with dual-material handle

Info

Publication number: AU2001287294A1
Application number: AU2001287294A
Authority: AU
Inventors: Joseph R. Hoepfl; Christopher D. Thompson
Original assignee: Snap On Technologies Inc
Current assignee: Snap On Inc
Priority date: 2000-03-30
Filing date: 2001-03-29
Publication date: 2002-01-03
Anticipated expiration: 2021-03-29

Description

METHOD OF FORMING TOOL WITH DUAL-MATERIAL HANDLE

Cross-Reference to Related Applications

This application is a continuation-in-part of serial no. 09/370,829, filed

August 9, 1999 which, in turn, is a division of application serial no. 08/931,086,

filed September 15, 1997.

Background

The present application relates to hand tools, particularly drivers, such as

screwdrivers, nut drivers and the like. The application relates in particular to

methods of making tool handles.

Description of the Prior Art

It is known to provide hand tools with plastic handles which are typically

formed of a single plastic material molded around an end of a tool shank.

It is also known to provide tool handles with a two-part construction,

including an inner portion formed of a hard or rigid material for the necessary

handle strength, and an outer gripping portion formed of a softer and/or more

resilient or flexible material for user comfort and to afford an improved grip by

increasing the frictional gripping force between the tool handle and the user's hand.

However, heretofore such dual-material handles have either had a relatively

complex and expensive construction or have suffered from slippage of the outer

hand grip portion relative to the inner body portion. Also, in molding prior dual-material handles, it has been difficult to

maintain uniform depth of the outer gripping material. Typically, the inner rigid

core is supported by its ends as a preform in a mold cavity and the outer resilient or

flexible gripping material is injected along one side of the longitudinal extent of

the handle and then flows circumferentially around the handle in both directions

along substantially the entire longitudinal extent. This can introduce bending or

uneven forces on the preform, which can cause uneven depth of material. Also, in

the event that there are raised indicia on the preform around which the softer

material is to be flowed, these bending forces can result in an improper seal

between the tops of the raised indicia and the mold, causing the inflowing material

to cover and obscure the indicia. Also, this technique tends to result in a cold knit

line in the finished handle extending longitudinally of the preform along the side

thereof opposite from the mold inlet gate.

Summary

This application describes a technique for providing an improved hand tool

with a handle construction which avoids the disadvantages of prior tools while

affording additional structural and operating advantages.

The application describes a hand tool with a dual-material handle of simple

and economical construction, with a hard core and softer outer grip portion. The

handle affords improved user grip and comfort while providing superior bonding

of the handle materials and prevention of slippage of the outer grip portion.

An improved method of molding the handle is also disclosed which results in balanced forces on mold preform inserts, good sealing around raised indicia on

the preform and avoidance of cold knit lines on the finished handle.

In particular, there is provided a method of forming a hand tool comprising

the steps of: injection molding a relatively hard and rigid inner body having an

elongated central portion and two end flanges extending laterally outwardly of the

central portion around the entire periphery thereof, the central portion having a

peripheral groove formed therein adjacent to an end flange, and injection molding

around the inner body an outer gripping body formed of a relatively soft and

resilient material so as to surround the central portion of the inner body and fill the

groove.

Brief Description of the Drawings

For the purpose of facilitating an understanding of the subject matter sought

to be protected, there are illustrated in the accompanying drawings preferred

embodiments thereof, from an inspection of which, when considered in connection

with the following description, the subject matter sought to be protected, its

construction and operation, and many of its advantages should be readily

understood and appreciated.

FIG. 1 is a side elevational view of a hand tool with a portion of the tool

shank broken away;

FIG. 2 is a slightly enlarged, fragmentary, side elevational view of the tool

of FIG. 1 , with the outer gripping body removed;

FIG. 3 is a view in vertical section taken along the line 3-3 in FIG. 2; FIG. 4 is a fragmentary view in vertical section taken along the line 4-4 in

FIG. 1 ;

FIG. 5 is an enlarged, fragmentary, sectional view of a portion of the handle

of FIG. 4;

FIG. 6 is an enlarged view in vertical section taken along the line 6-6 in

FIG. 1;

FIG. 7 is an enlarged view in vertical section taken along the line 7-7 in

FIG. 1 ;

FIG. 8 is a fragmentary sectional view of a mold assembly for making the

handle of the hand tool of FIGS. 1-7; and

FIGS. 9A through 9C are diagrammatic illustrations of the material flow in

the mold assembly of FIG. 8, with the orientation of the parts inverted from that in

FIG. 8.

Detailed Description

Referring to FIGS. 1 and 4-7, there is illustrated a hand tool, generally

designated by the numeral 10, in the nature of a screwdriver. The tool 10 includes

an elongated handle 11 and an elongated shank 12 projecting from one end of the

handle 11, substantially axially thereof, and terminating in a tip 13, such as a flat

blade screwdriver tip. While the tool 10 is in the form of a screwdriver, it will be

appreciated that the principles of the present invention are applicable to other types

of hand tools, particularly manually rotatable driver-type tools.

The handle 11 is of two-part construction, including an inner body 20 and an outer gripping body 35. Referring also to FIGS. 2 and 3, the inner body 20 is

preferably injection molded around an end of the shank 12 and formed of a suitable

plastic material, such as polypropylene, although other materials could be used.

Preferably, the inner body 20, as molded, is a relatively hard and rigid member,

including an elongated central portion 21 coaxial with the shank 12. The central

portion 21 has a main rear section 22, a forwardly sloping section 23, a reduced

cross-section neck section 24 and a flared section 25. The central portion 21 is

unitary at its rear end with an end flange 26, which extends laterally outwardly

from the central portion 21 around its entire periphery and has a curved end surface

27. The central portion 21 is unitary at its forward end with an end flange 28,

which projects laterally outwardly from the central portion 21 around its entire

periphery and terminates in a substantially flat end surface 29.

Formed in the outer surface of the inner body 20 at the junction between the

central portion 21 and the front end flange 28 is a peripheral groove 30. If desired,

a similar groove may be provided adjacent to the rear end flange 26. The inner

body 20 has a transverse cross-sectional shape which varies from one end to the

other. Thus, the main or rear section 22 has a transverse cross section which is

generally in the shape of a triangle with rounded corners (see FIG. 6), while the

cross section at the neck section 24 may have a generally tri-lobular shape (see

FIG. 7). Raised indicia 32 may project laterally outwardly from the outer surface

of the main rear section 22.

The outer gripping body 35 is preferably injection molded around the inner body 20 and is formed of a suitable thermoplastic elastomer material, although

other materials could be used. Preferably, the material of the outer gripping body

35 is selected so that, in its as-molded condition, it is relatively soft and flexible to

provide an improved gripping surface and improved comfort for a user's hand. The

outer gripping body 35 completely covers the central portion 21 of the inner body

20 between the end flanges 26 and 28, except that the outer surface of the outer

gripping body 35 is preferably substantially flush with the tops of the raised indicia

32, as can best be seen in FIGS. 4-6, filling all of the spaces between the indicia

32. The outer gripping body 35 also fills the groove 30 on the inner body 20 to

facilitate non-slip adhesion of the outer gripping body 35 to the inner body 20.

The outer gripping body 35 has end portions 36 and 37 which have a thickness

such that they do not extend laterally outwardly substantially beyond the periphery

of the end flanges 26 and 28. In the preferred embodiment the front end portion 37

is substantially flush with the outer surface of the front end flange 28, while the

rear end portion 36 may extend laterally outwardly a slight distance beyond and

slightly overlap the outer surface of the rear end flange 28, as can best be seen in

FIGS. 1 and 4. It will be appreciated that the end flanges 26 and 28 cooperate with

the outer gripping body 35 to inhibit longitudinal sliding movement of the outer

gripping body 35 relative to the inner body 20.

Preferably, the thickness of the outer gripping body 35 is substantially

constant along the length and around the periphery of the handle, but it may vary

slightly. However, it will be appreciated that, by suitable design of the molding tools, the outer surface of the finished hand tool 10 may have any desired cross-

sectional shape anywhere along its length.

There results a hand tool with a hard, rigid inner body 20 fixedly secured to

the tool shank 12 so as to provide the necessary strength for high-torque

applications, while at the same time providing a relatively soft and flexible outer

gripping body 35 for contact with the user's hand to afford a comfortable frictional

gripping surface

The handle 11 is formed in a two-shot injection molding process, the inner

body 20 being formed in the first shot and the outer gripping body 35 being formed

in the second shot. The first shot is conventional and, therefore, is not described in

detail herein. Referring to FIG. 8, there is illustrated a mold assembly 40 for

performing the second shot. The mold assembly 40 includes a lower mold part 41

and an upper mold part 42 which cooperate to define a mold cavity 43. In

operation, after the formation of the inner body 20, which, in the illustrated

embodiment, as been molded with an axial bore 12A in the front end thereof, is

moved as a preform into the mold cavity 43. More specifically, the inner body 20

is fitted over a fixture 44, which projects axially into the mold cavity 43 and is

received into the axial bore 12 A for accurately positioning and temporarily

supporting the inner body 20. Then the mold assembly 40 is closed. As can be

seen in FIG. 8, the mold assembly 40 has an inlet gate 45 positioned directly over

the peripheral groove 30 for introducing the mold charge thereinto. It can be seen

that, when the mold assembly 40 is closed, it clamps tightly around the end flanges 26 and 28 of the inner body 20 for supporting the inner body 20 at its opposite

ends. Also, the mold cavity 40 is designed so that, in its closed condition, the

lower part 41 seals tightly against the distal ends of the indicia 32 along a seal

surface 48.

FIGS. 9A-9C diagrammatically illustrate the progression of the mold charge

50 through the mold cavity 43. As can be seen in FIG. 9 A, the mold charge

initially is introduced into the peripheral groove 30 and flows circumferentially

therearound, forming a ring of material 51, filling the groove 30.

Then, referring to FIG. 9B, the mold charge begins to move longitudinally

rearwardly along the inner body 20 around the entire length of the ring of material

51, forming an advancing front 52. This front continues to move rearwardly in the

direction of the arrows in FIG. 9C, flowing around the raised indicia 32 and finally

stopping against the end flange 26. Because the mold charge advances in a

continuous ring of material, it exerts substantially equal pressure on the inner body

20 at all points around the periphery thereof, thereby preventing a tendency to bend

or deflect the inner body 20 in the mold cavity 53. Thus, the outer gripping body

35 is formed with a desired thickness in a uniform manner and the seal between the

lower mold part 41 and the raised indicia 32 is maintained. After completion of the

second shot of the mold, the mold assembly 43 is opened and the completed handle

11 is removed, after which a shank 12 may be press fitted into the bore 12A or

fixedly secured therein by other means, such as suitable adhesives or the like.

However, it will be appreciated that in forming the tool 10, the inner body 20 may alternatively be injection molded around an end of the shank 12 in the first

mold shot, after which the outer gripping body 35 is injection molded around the

inner body 20. In that case the fixture 44 would not be used and the mold assembly

40 would be slightly modified to accommodate the shank 12. Also, it will be

appreciated that other techniques could be used for forming and applying the outer

gripping body 35 and, if desired, it could be preformed and secured in place by the

use of suitable adhesives or the like.

From the foregoing, it can be seen that there has been provided an improved

hand tool and method of forming same with a handle having both high strength and

a comfortable gripping surface for contact with the user's hand.

The matter set forth in the foregoing description and accompanying

drawings is offered by way of illustration only and not as a limitation. While

particular embodiments have been shown and described, it will be obvious to those

skilled in the art that changes and modifications may be made without departing

from the broader aspects of applicants' contribution. The actual scope of the

protection sought is intended to be defined in the following claims when viewed in

their proper perspective based on the prior art.

Claims

We Claim:

1. A method of forming a hand tool comprising the steps of:

injection molding a relatively hard and rigid inner body having an elongated

central portion and two end flanges extending laterally outwardly of the central

5 portion around the entire periphery thereof,

said central portion having a peripheral groove formed therein adjacent to

an end flange, and

injection molding around said inner body an outer gripping body formed of

a relatively soft and resilient material so as to surround said central portion of said

o inner body and fill said groove.

2. The method of claim 1 , wherein said inner body is generally

triangular in transverse cross section.

3. The method of claim 1 , wherein said outer body is molded to a

thickness such that the portions thereof respectively adjacent to said end flanges

s are laterally approximately coextensive with said end flanges.

4. The method of claim 3, wherein said outer body is formed to a

thickness such that the portion thereof adjacent to at least one of said end flanges is

substantially flush therewith.

5. The method of claim 1 , wherein said step of injection molding said

o inner body includes molding said body around a tool shank such that the shank

projects from an end of said inner body substantially coaxially therewith.

6. A method of forming a hand tool comprising the steps of:

providing a relatively hard and rigid inner body having an elongated central

portion and two end flanges extending laterally outwardly of the central portion

around the entire periphery thereof and a peripheral groove formed in the central

5 portion adjacent to one end flange, and

injection molding around the inner body an outer gripping body by causing

mold charge in fluid state to flow first along the peripheral groove to form a ring of

material which fills the groove and abuts the one end flange and then to flow

longitudinally along the central portion to another end flange,

o the mold charge being such that it cools to a relatively soft and resilient

material in solid state.

7. The method of claim 6, wherein the mold charge, while flowing

along the length of the central portion, exerts substantially equal pressure thereon

around the entire periphery thereof.

s

8. A method of forming a hand tool comprising the steps of:

providing a relatively hard and rigid inner body having an elongated central

portion with two ends and two end flanges extending laterally outwardly of the

central portion around the entire periphery thereof and a peripheral groove formed

in the central portion adjacent to one end flange,

o supporting the inner body only at the ends in a mold cavity, and

injection molding around the inner body an outer gripping body by

introducing a mold charge in fluid state into the mold cavity adjacent to the one end flange so that the charge flows first along the length of the peripheral groove

to form a ring of material which fills the groove and abuts the one end flange and

then flows longitudinally along the central portion to another end flange,

the mold charge being such that it cools to a relatively soft and resilient

material in solid state.

9. The method of claim 8, wherein the mold charge, while flowing

around the entire periphery thereof.

10. The method of claim 8, wherein the inner body has raised indicia on

the central portion thereof, and further comprising providing a seal against the

distal ends of the indicia so that the mold charge flows around the indicia but does

not cover the distal ends thereof, the mold charge, while flowing along the length

of the central portion, exerting substantially equal pressure thereon around the

entire periphery thereof so as not to disturb the seal against the indicia.